Acoustical Treatments Master Thread [Text View] - Page 23

R Harkness

12-07-09, 03:14 PM

Advice Needed:

I have my stand mounted L/R speakers fairly close to the room corners on either side of the projection screen. I had left the dry-wall open on the sides of the screen and filled it with 4" fibre-board to get at least some bass trapping if possible. I plan to add another 4" thickness of the fibre-board (OFI 48) to make the trap 8" thick.

In front of the 8" of fibre board in the room corners are 5 hanging panels of black velvet, on each side of the screen. These travel horizontally to mask different widths of the screen, and when opened the panels stack 5 deep on each side, in the room corner. So I'd presume that adds a tiny bit more absorption.

BUT....the issue is that I'm considering replacing one or two of the velvet panels with a light-weight board material, then wrapping the velvet around the stiff material, to get a nice, flat velvet-covered panel for masking.

I'm looking at using 4mm thick Coroplast - a white corrugated plastic sheet. So it's very thin and mostly hollow (due to corrugation - think cardboard).

ETA picture - this is what I'm talking about, 4mm thick:
http://www.archivalsuppliers.com/images/Picture%20818.jpg

I don't intend to replace all 5 panels on each side of my screen with this Coroplast, only one or perhaps two of the panels per side. So a max of 4mm to 8mm of Coroplast would go in the room corners.

Do I need to worry about putting such a panel behind my speaker, between the speaker and the acoustic OFI 48 fibre-board I'm using as "bass" traps?
Will it stop the sound from being absorbed or reduce the effectiveness of
the acoustic absorption behind the speaker?

I'm figuring probably not - that at the type of bass frequencies I'd hope to be absorbing, such a thin piece of corrugated plastic material wouldn't "stop" the sound from being absorbed by the bass traps behind it. But thought I should check before I go ahead.

Thanks.

Techlord

12-07-09, 08:58 PM

Wow this thread is a little more into tearing down drywall, I live in a condo and am just looking for acoustic treatments to hang on my walls. My living room is 12 ft. x 18 ft. and I'm sitting 9 1/2 feet from my flat panel display, my room is rectangular but almost square. My problem is I have my back to a wall about 1ft. behind my head, sliding door on my left and to the right go's into my dinning room am tired of the constant reverb ecos, my AV gear consists of MKsound 750 THX 5.1 speaker system, Denon AVR-5700, Oppo BDP-83SE and a Samsung LN52B750 series LCD. My seeting vtwo 12ft I'm not intrested in buying new AV gear with room corrections (tight budget) and would like something affordable that I can just hang on my walls. I have thick carpeting with area rug and nothing in-between me and my speakers. Thank you for any reply/advice, Techlord. :)

I have my seating position between the wall that meaures 12ft., so my width would be 18ft.

nathan_h

12-07-09, 11:19 PM

Techlord

12-08-09, 12:40 AM

The mirror trick is a good one. Thick panels where sound bounces like a pool ball from the speaker, off a wall or ceiling or floor, to your ear.

http://www.realtraps.com/art_room-setup.htm

-

Secondarily, bass trapping in the corners.

http://www.realtraps.com/placing_mt.htm

-

From the GIK web site, a picture of how it might look. Since you are sitting at the back wall, consider changing that. Sitting out into the room will sound much better.

http://www.gikacoustics.com/images/room_layout_662.gif

It's impossible to do it like the picture, I would be looking at my sliding glass door. If you turn it around I'm looking at my kitchen bar area, the way it is is the way it must be done. Here better yet hear are some pictures, excuse the mess I've been painting. My camera makes my place look half as large.

Thank you soo much for you help so far! :D

Rob Will

12-08-09, 08:53 AM

A civic group is seeking to construct a multi-media theater inside of a local museum. Noise transmission to other parts of the building will not be a major issue because of the proposed theater location. What does seem to be a problem is that the existing space has a 16' high 3-faceted vaulted ceiling that concentrates reflected sound back toward the center of the room. Frankly, the existing room sounds horrible!:eek:

Otherwise, the room is basically a 27' x 31' rectangle with the screen wall (front) being 27' x 11' high. A 7.1 surround system is proposed with the LCR speakers behind an AT screen.

There are approx. 47 seats in the proposed theater with the back row adjacent to the back (27') wall. The seating is on risers with the back row elevated approx 4' above the main floor.

1.) Will a 2" fiberglass ceiling tile system help kill the concentrated reflections from the ceiling?

2.) How would you treat the screen wall?

3.) How would you treat the back wall?

4.) How would you treat the sides?

5.) If placing bass traps at a 45 degree angle in the corners can't work due to aesthetics and space limitations, how would you kill boomy bass?

Thanks,
Rob

CJO

12-08-09, 09:21 AM

Rob- do you have the budget to hire a professional? Especially with the existing conditions and restraints you have, you would end up with a much better result.

CJ

Weasel9992

12-08-09, 10:57 AM

Rob- do you have the budget to hire a professional? Especially with the existing conditions and restraints you have, you would end up with a much better result.

CJ

I completely, totally agree.

Frank

Weasel9992

12-08-09, 11:01 AM

It's impossible to do it like the picture, I would be looking at my sliding glass door. If you turn it around I'm looking at my kitchen bar area, the way it is is the way it must be done. Here better yet hear are some pictures, excuse the mess I've been painting. My camera makes my place look half as large.

That's going to be the tough way to do it...even taking into account that the room is larger than the picture makes it out to be, there's a very short distance between your speakers and the wall behind your head. You'll want thick bass trapping on the back wall behind your head (which may mean moving the couch out from the wall another 6") and at least 4" panels on the front wall behind the speakers. To say it in more general terms, you'll want as much 50-250Hz trapping as you can stand to look at.

Frank

Rob Will

12-08-09, 12:24 PM

Here's the problem:

Thus far we only have funding for the preliminary architectural work. Things like:
Overall space considerations
Structural engineering
Electrical engineering
Fire codes
etc.

IF we can advance the project, and there proves to be enough space within the museum to make this happen, and the structural works out, we are going to address the topics of acoustics and outfitting as the next phase of our fund raising. So yes, acoustic professionals WILL be involved BEFORE the design is complete.

Here's our chicken-egg scenario:
We need to get a general feel for the space considerations and overall $$$. Things like: will we have a baffle wall? Will we be looking at a drop ceiling?

The reason that we need to ask these PRELIMINARY questions is because they ultimately impact whether or not the project is doable. For example things like relocating the sprinkler system ($$$).

So these are very preliminary questions to get a feel for the overall space.
We are not going to get formal acoustic work done until we see that things like structural come back OK and will handle the weight of 50 people as a live load.

This is NOT a do it yourself sort of project and we are seeking input from numerous company reps at the highest levels. We even put on a "theater tech" show to help educate ourselves. The Christie rep brought in a 10,000 lumen projector etc. Many other area museums and school districts attended our show and it was a great success.

Any GENERAL SUGGESTIONS that you have will be most helpful in steering the ultimate outcome of this project::).

Thanks,
Rob

Techlord

12-08-09, 03:27 PM

That's going to be the tough way to do it...even taking into account that the room is larger than the picture makes it out to be, there's a very short distance between your speakers and the wall behind your head. You'll want thick bass trapping on the back wall behind your head (which may mean moving the couch out from the wall another 6") and at least 4" panels on the front wall behind the speakers. To say it in more general terms, you'll want as much 50-250Hz trapping as you can stand to look at.

Frank

I am new at this, where might I find some affordable 50-250Hz trapping and what does it look like? Perhaps they come in colors, I will look at mud on the wall to get better sound! :D

Thank you Weasel,
Techlord! :)

Rob Will

12-08-09, 11:02 PM

Techlord

12-09-09, 12:56 AM

I have googled 50-250Hz trapping treatments and comes up with nothing?:confused:

pepar

12-09-09, 08:53 AM

I have googled 50-250Hz trapping treatments and comes up with nothing?:confused:
StudioTips (http://forum.studiotips.com/viewforum.php?f=8&sid=6f255fddc231316b26a927435ba4ea72)

Techlord

12-09-09, 09:10 AM

StudioTips (http://forum.studiotips.com/viewforum.php?f=8&sid=6f255fddc231316b26a927435ba4ea72)

Thank you for the link pepar, but I just want to buy it and hang it however strange it might look. :)

rhcorolla

12-09-09, 11:02 AM

Thank you for the link pepar, but I just want to buy it and hang it however strange it might look. :)Phone or e-mail realtraps.com and/or gikacoustics.com. If you provide them your A/V room lay-out/ equipment/ listening preferences/ restrictions/ budget/ etc.; they have expertise & products to acoustically treat your room a little, a lot, or somewhere in-between. Their websites also have excellent articles/ theory/ diagrams/ etc. re: acoustics/ sound treatments/ etc..

If you want to DIY, then a LOT of research, due diligience & hard work is needed.

Ethan Winer

12-09-09, 04:43 PM

Phone or e-mail realtraps.com and/or gikacoustics.com.

Exactly, and thanks. :D

DIY is great, and I help people with that all the time. But not everyone is up for that. Another reason to buy from a vendor is the good ones will tell you what you need and where to put it. For many people that's a lot better than spending literally weeks doing research, and still not being certain they have the correct strategy.

--Ethan

Weasel9992

12-09-09, 05:09 PM

I have googled 50-250Hz trapping treatments and comes up with nothing?:confused:

A well-built 4" absorber will cover much of that...you'll need thicker absorbers to get down into the 50's.

Frank

R Harkness

12-09-09, 08:35 PM

BUMP:

If I'm going to make these panels it has to be by the weekend, so I'm hoping someone can help me with some info on the question below.
Many thanks.

Advice Needed:

I have my stand mounted L/R speakers fairly close to the room corners on either side of the projection screen. I had left the dry-wall open on the sides of the screen and filled it with 4" fibre-board to get at least some bass trapping if possible. I plan to add another 4" thickness of the fibre-board (OFI 48) to make the trap 8" thick.

In front of the 8" of fibre board in the room corners are 5 hanging panels of black velvet, on each side of the screen. These travel horizontally to mask different widths of the screen, and when opened the panels stack 5 deep on each side, in the room corner. So I'd presume that adds a tiny bit more absorption.

BUT....the issue is that I'm considering replacing one or two of the velvet panels with a light-weight board material, then wrapping the velvet around the stiff material, to get a nice, flat velvet-covered panel for masking.

I'm looking at using 4mm thick Coroplast - a white corrugated plastic sheet. So it's very thin and mostly hollow (due to corrugation - think cardboard).

ETA picture - this is what I'm talking about, 4mm thick:
http://www.archivalsuppliers.com/images/Picture%20818.jpg

I don't intend to replace all 5 panels on each side of my screen with this Coroplast, only one or perhaps two of the panels per side. So a max of 4mm to 8mm of Coroplast would go in the room corners.

Do I need to worry about putting such a panel behind my speaker, between the speaker and the acoustic OFI 48 fibre-board I'm using as "bass" traps?
Will it stop the sound from being absorbed or reduce the effectiveness of
the acoustic absorption behind the speaker?

I'm figuring probably not - that at the type of bass frequencies I'd hope to be absorbing, such a thin piece of corrugated plastic material wouldn't "stop" the sound from being absorbed by the bass traps behind it. But thought I should check before I go ahead.

Thanks.

Techlord

12-09-09, 09:16 PM

Phone or e-mail realtraps.com and/or gikacoustics.com. If you provide them your A/V room lay-out/ equipment/ listening preferences/ restrictions/ budget/ etc.; they have expertise & products to acoustically treat your room a little, a lot, or somewhere in-between. Their websites also have excellent articles/ theory/ diagrams/ etc. re: acoustics/ sound treatments/ etc..

If you want to DIY, then a LOT of research, due diligience & hard work is needed.

Thank you rhcorolla, I called Realtraps and they have Guilford Minitraps 2 by 4 foot size panel absorbers for $179-$249 and can special order larger sizes available, up to 4 by 8 feet! I think I'll be getting three 4 x 8 foot HF absorbing panels to tame the high frequencies ecos, two verticals and the other horizontal along the top behind of my 52" LCD display. Do you think I should invest in corner absorbing panels or are three 4 x 8 foot HF absorbing panels enough?

rhcorolla

12-10-09, 08:11 AM

Thank you rhcorolla, I called Realtraps and they have Guilford Minitraps 2 by 4 foot size panel absorbers for $179-$249 and can special order larger sizes available, up to 4 by 8 feet! I think I'll be getting three 4 x 8 foot HF absorbing panels to tame the high frequencies ecos, two verticals and the other horizontal along the top behind of my 52" LCD display. Do you think I should invest in corner absorbing panels or are three 4 x 8 foot HF absorbing panels enough?Bass trap-wise, best bang for the buck is to treat as many corners as you reasonably can either by straddling a 4” min. thk. flat panel at corners or getting even more absorption w/ super chunk or solid fiberglass corner adsorbers. You have 12 corners in a room (4 vertical corners, 4 floor-wall corners & 4 ceiling-wall) that can potentially be treated. Of course furniture/ room openings, windows, aesthetics, wife acceptance factors, budget play into these choices.

This Real Traps article discusses bass traps.

http://www.realtraps.com/lf-noise.htm

A good initial investment is to utilize a Radio Shack or equivalent Sound Pressure Level meter ($50 or so) & utilize test tones (mp3 file in referenced article for 10 Hz- 300 Hz tones) to determine where you have peaks & nulls in your particular room & primary listening area. Is your room “live” or “dead” or somewhere “in-between”? YOUR specific set-up & room limitations dictate best path forward.

Again, talking to the fine folks at Real Traps & GIK Acoustics (who have forgotten more about acoustics than I or most posters on this thread will ever know) are the best sources for your particular set-up/ situation.

Edit: Techlord, At the risk of information overload, here are two excellent articles re: room acoustics & sound treatments from the (2) recommended subject matter experts. Don’t be intimidated by all the info. Just focus on key points re: best placement for early reflection panels & bass traps. The 38% rule for room set-up is also very helpful.

http://www.realtraps.com/art_room-setup.htm

http://www.gikacoustics.com/education.html

pepar

12-10-09, 08:49 AM

Spaceman

12-10-09, 08:58 AM

pepar

12-10-09, 09:02 AM

How kid-proof /pet-proof is the GOM fabric? I have visions of my cats using the walls as scratching posts and my kids.....well they're kids. Is it pretty durable? I prefer the seamless look of Big's walls above and below a chair rail but am thinking the panel approach may make repairs easier. Any thoughts?
No, it's not *that* durable. You will not be happy with your cats if they use your panels as scratch pads. And the panel covering would need to be REPLACED; there is no repair that I can think of that would fix the damage.

Parent up and prevent the damage from happening in the first place!

Weasel9992

12-10-09, 11:50 AM

I'd like to throw something out there that a consumer of acoustical treatments should know in order to make a completely informed buying decision. In bulk from an HVAC insulation distributor, a 2x4x2" sheet of OC 703, the material that goes into the panels being discussed here, is about $6-$8. The others here make good points about DIY research taking time and companies like Realtraps and GIK doing basic analysis and recommending what should go where, but without the underlying raw material cost you really don't have the whole picture.

That's true, but also in the interest of fairness it's only true if you can get the insulation material locally. After you add other materials, a DIY 2" trap is typically around $20 (for just fabric-wrapped insulation), or around $30 (for a panel with an internal frame). That doesn't count installation hardware or the time it takes to make it though.

Frank

pepar

12-10-09, 12:23 PM

That's true, but also in the interest of fairness it's only true if you can get the insulation material locally. After you add other materials, a DIY 2" trap is typically around $20 (for just fabric-wrapped insulation), or around $30 (for a panel with an internal frame). That doesn't count installation hardware or the time it takes to make it though.

Frank
Yes, Frank, I neglected to include the important caveat that a local supplier is needed as shipping and handling of a product as voluminous as fiberglass can quickly inflate the per sheet price.

Jeff

gdc

12-10-09, 03:58 PM

BUMP:

If I'm going to make these panels it has to be by the weekend, so I'm hoping someone can help me with some info on the question below.
Many thanks.

What you are planning to do should have NO adverse effect on any other bass trapping you do. Of course, it will have no positive effect either.

It looks like those panels could be slightly reflective at higher frequencies, though.

gdc

12-10-09, 04:02 PM

OK guys, has anyone used a decorative column as a bass trap in the four corners of a room?

What would happen if you made a 4-sided box with the outer skin of 1/4" pegboard (Masonite)- then experimented with various acoustic materials inside the "column"?

The dimensions of the column might be something like 12" x 12" x 96" tall. It would be fabric wrapped and positioned a couple of inches from each corner of the room.

Anybody venture a guess as to what the sound absorption characteristics of this "column" would be?

Thanks,
RobAbsorption would not be great. You need more thickness.

In addition, you want to straddle the corner.

Finally, the masonite might reflect some energy back into the room. Ideally, you want an open face (fabric covered) to the sound energy coming INTO the corner. Without that, the 'bass doesn't all enter the trap.'

Techlord

12-10-09, 04:40 PM

Bass trap-wise, best bang for the buck is to treat as many corners as you reasonably can either by straddling a 4” min. thk. flat panel at corners or getting even more absorption w/ super chunk or solid fiberglass corner adsorbers. You have 12 corners in a room (4 vertical corners, 4 floor-wall corners & 4 ceiling-wall) that can potentially be treated. Of course furniture/ room openings, windows, aesthetics, wife acceptance factors, budget play into these choices.

This Real Traps article discusses bass traps.

http://www.realtraps.com/lf-noise.htm

A good initial investment is to utilize a Radio Shack or equivalent Sound Pressure Level meter ($50 or so) & utilize test tones (mp3 file in referenced article for 10 Hz- 300 Hz tones) to determine where you have peaks & nulls in your particular room & primary listening area. Is your room “live” or “dead” or somewhere “in-between”? YOUR specific set-up & room limitations dictate best path forward.

Again, talking to the fine folks at Real Traps & GIK Acoustics (who have forgotten more about acoustics than I or most posters on this thread will ever know) are the best sources for your particular set-up/ situation.

Edit: Techlord, At the risk of information overload, here are two excellent articles re: room acoustics & sound treatments from the (2) recommended subject matter experts. Don’t be intimidated by all the info. Just focus on key points re: best placement for early reflection panels & bass traps. The 38% rule for room set-up is also very helpful.

http://www.realtraps.com/art_room-setup.htm

http://www.gikacoustics.com/education.html

My room is "live" and more "reflective" that "live" in the extreme, I believe if I can tame the "reflectiveness it would sound much better! I never thought to use my Radio Shac Sound Pressure Level meter for finding peaks & nulls in my room, I guess it has more uses than I thought! :D You have mentioned Bass traps, I have an MKSound THX 5.1 sound system where anything below 80Hz go's to the non-ported 12" subwoofer. I only have two corners that are within close proximity to my speakers, the other two corners are bending into the dining room. I definitely need high frequency absorbing panels behind my speakers and flat panel display if I understand it correctly, I will read through those links probably more than once, I'm not easily the kind that would give up do to overload! :D

Thank you,
Techlord. :)

Techlord

12-10-09, 04:48 PM

I'd like to throw something out there that a consumer of acoustical treatments should know in order to make a completely informed buying decision. In bulk from an HVAC insulation distributor, a 2x4x2" sheet of OC 703, the material that goes into the panels being discussed here, is about $6-$8. The others here make good points about DIY research taking time and companies like Realtraps and GIK doing basic analysis and recommending what should go where, but without the underlying raw material cost you really don't have the whole picture.

So you think I could build my own wooden frame and buy these inexpensive insulation? For the record I do not have early reflection between me and my speakers, my ear is the first thing sounds will intersect.

rhcorolla

12-10-09, 05:17 PM

So you think I could build my own wooden frame and buy these inexpensive insulation? For the record I do not have early reflection between me and my speakers, my ear is the first thing sounds will intersect.
:eek: Woah! You really need to read up on the subject as you have first reflection/ early reflection sound waves bouncing all over creation: off your floors, ceiling, side walls, back wall & front wall that come to your listening area. Sound treatment panels in the right locations help minimize/ eliminate these problems to prevent coloration, provide more detail & hopefully provide a flatter frequency response to your ears (improving peaks & nulls @ certain frequencies).

Terry Montlick

12-10-09, 05:21 PM

Anybody venture a guess as to what the sound absorption characteristics of this "column" would be?

This is a Helmholtz absorber. My guestimate is that it would have peak absorption in the range 200-400 Hz. The material you stuff it with can effect the bandwidth (tightness of the peak) some. It won't reach very much below 100 Hz, though.

- Terry

pepar

12-10-09, 06:07 PM

So you think I could build my own wooden frame and buy these inexpensive insulation?
That depends on your shop skills, motivation level and proximity to an HVAC insulation distributor (http://www.spi-co.com/directory.html). I built my own (http://peparsplace.com/Pg_16.htm).

For the record I do not have early reflection between me and my speakers, my ear is the first thing sounds will intersect.
If you have a ceiling and floor between you and the speakers, you have early reflections. Even if your room is wide you will have early reflections. Yes, the line between your speakers and your ears is the most direct path, but it's not that the "early" reflections arrive *before* the direct sound, it's that they arrive just after and blur the image.

Rob Will

12-10-09, 07:53 PM

This is a Helmholtz absorber. My guestimate is that it would have peak absorption in the range 200-400 Hz. The material you stuff it with can effect the bandwidth (tightness of the peak) some. It won't reach very much below 100 Hz, though.- Terry

Terry, Thanks for the info. Did your answer take into account that I was considering the use of 1/4" perforated pegboard? Would a true Helmholtz absorber have a non-perforated skin? Are there other skin materials that would provide better / different absorption characteristics?

Thanks again,
Rob

Terry Montlick

12-10-09, 08:00 PM

Terry, Thanks for the info. Did your answer take into account that I was considering the use of 1/4" perforated pegboard? Would a true Helmholtz absorber have a non-perforated skin? Are there other skin materials that would provide better / different absorption characteristics?

Thanks again,
Rob
Yes. I assumed common perf board with 1/4" holes on 1" centers.

To make a Helmholtz resonator, you need a chamber with holes. You can have one hole, or a number of them on a regular grid. The hole size, spacing, material thickness (I assumed 1/4") and resonator volume all determine the absorption.

R Harkness

12-10-09, 08:15 PM

Terry Montlick,

Would you mind tackling the question I have on this page (see above, with photo) about the effects of putting 4mm thick Coroplast in front of my bass trap area?

(And, if it will act as a barrier to the effectiveness of the bass trap, would heavily perforating the Coroplast help?).

Thanks.

Terry Montlick

12-10-09, 08:22 PM

R Harkness

12-10-09, 09:20 PM

I don't know of any acoustic use for corrugated plastic. It can only interfere with the operation of a bass absorber.

- Terry

(Sigh)...thanks Terry.

Back to the drawing board for me...

Rob Will

12-10-09, 10:42 PM

Does anyone have pics of corner bass traps disguised as decorative columns?
I'm trolling for ideas regarding a theater space in a public building.
The traps would need to be durable enough for groups of school kids to visit the theater.

The space currently has some serious reflections.
Here are the reverb times::eek:
32Hz - 0.8 sec.
63Hz - 1.48 sec.
125Hz - 1.10 sec.
250Hz. - 1.44 sec.
500Hz - 1.48Hz.
1000Hz. - 1.18 sec.
2000Hz. - 1.06
4000Hz. - 0.61 sec.
8000Hz. - 0.33 sec.

Thanks,
Rob

Techlord

12-10-09, 11:41 PM

That depends on your shop skills, motivation level and proximity to an HVAC insulation distributor (http://www.spi-co.com/directory.html). I built my own (http://peparsplace.com/Pg_16.htm).

If you have a ceiling and floor between you and the speakers, you have early reflections. Even if your room is wide you will have early reflections. Yes, the line between your speakers and your ears is the most direct path, but it's not that the "early" reflections arrive *before* the direct sound, it's that they arrive just after and blur the image.

Yes it's that after effects that blur the image that I trying to get rid of, I probably hear the same blurred image over and over again killing the original image! So would you recommend the Guilford MiniTraps that are 2 by 4 feet, and 2.75 inches thick which are good for reflection control? I will probably get a few for behind my speakers to start with and go from there.

mrkplatt

12-11-09, 11:25 AM

Attached is the layout of my room showing the locations of the ATS Traps that I have now. Three 4" traps (2' wide floor to ceiling - 7' ceiling in the room) in the wall-to-wall corners and 2'x4'x2" on the walls.

I'm wondering if anyone can advise me on how to treat my "tunnel" and "cave". A tunnel at the entry way in the front of the theater, and a cave in the rear of the theater.

Thanks for any advice!

bpape

12-12-09, 10:52 PM

Rob Will

12-13-09, 02:32 PM

What are the dimensions of the space and are those measured with or without people in the space? The numbers may be good, OK, or bad depending.

Bryan

The proposed space is about 26' wide x 31' deep and has a 3-faceted vaulted ceiling 16' high.

At this time, we are just trying to get some basic layout ideas.

As far as having people in the room for a reverb measurement(?), it does not yet exist with seating - for now just a museum space with a few exhibits - so I can't measure that.

My question would be: How can you take a space with so much reverb that it is hard to understand speech and make it a high quality theater? How can 1.5 second reverb times EVER be a good thing? :eek:

Thanks,
Rob

pepar

12-13-09, 02:52 PM

The proposed space is about 26' wide x 31' deep and has a 3-faceted vaulted ceiling 16' high.

At this time, we are just trying to get some basic layout ideas.

As far as having people in the room for a reverb measurement(?), it does not yet exist with seating - for now just a museum space with a few exhibits - so I can't measure that.

My question would be: How can you take a space with so much reverb that it is hard to understand speech and make it a high quality theater? How can 1.5 second reverb times EVER be a good thing? :eek:

Thanks,
Rob
That's rhetorical, right?:)

Rob Will

12-14-09, 09:34 AM

That's rhetorical, right?:)

Yes, as opposed to outright sarcasm like:

"Everyone on this forum is so forthcoming with information"

I'm just trying to get a basic understanding of some acoustical issues to convey to our architect. Fortunately, Ethan Winer has gone to a lot of effort to share his knowledge and posted some VERY informative articles on the net. I will be sure and tell the architect about RealTraps acoustic ceiling tile and other cost-effective products:).

Aside from that, I am trying to get a feel for how much space we need behind the screen, approx speaker sizes and mounting locations, and most of all...... we are looking for bass trapping ideas that look like architectural elements.

This is a 27' x 31' room.
It will have a ceiling mounted projector and roughly a 15' wide AT screen in 16:9. Any info about that screen wall would be most helpful.

Thanks,
Rob

pepar

12-14-09, 10:12 AM

Yes, as opposed to outright sarcasm like:

"Everyone on this forum is so forthcoming with information"

I'm just trying to get a basic understanding of some acoustical issues to convey to our architect. Fortunately, Ethan Winer has gone to a lot of effort to share his knowledge and posted some VERY informative articles on the net. I will be sure and tell the architect about RealTraps acoustic ceiling tile and other cost-effective products:).

Aside from that, I am trying to get a feel for how much space we need behind the screen, approx speaker sizes and mounting locations, and most of all...... we are looking for bass trapping ideas that look like architectural elements.

This is a 27' x 31' room.
It will have a ceiling mounted projector and roughly a 15' wide AT screen in 16:9. Any info about that screen wall would be most helpful.

Thanks,
Rob
Respectfully, Rob, if you popped in with one question, many here could answer. But you seem to be looking for turnkey design services. Those on this thread that have that ability are pros who make a living at it.

You can either continue to do your own research, or you can become a customer of Ethan's or GIK or Terry Montlick and be told what to place where (and where to buy it in the case of Terry as he is *only* :) an acoustician and not a vendor).

Jeff

Ethan Winer

12-14-09, 05:24 PM

How can you take a space with so much reverb that it is hard to understand speech and make it a high quality theater?

That's a large space, so the answer is a fair amount of absorption placed in various locations around the room. Where depends on many factors, such as the location of the seating and loudspeakers etc.

--Ethan

bpape

12-14-09, 08:22 PM

The point Rob was that if the room was 50x100, those times are more acceptable than if it's 10x15.

The room you're describing is not quite big enough for large space acoustics but pretty big for small space acoustics.

For a theater will full range music you'll need some broadband bass control and a reasonable amount of absorption around the space including reflections and the front wall to get it under control.

Behind an AT screen, the amount of space will depend on the speakers, their depth, etc. Broadband bass control can also be hidden behind the false wall if the entire wall is also AT.

Columns are an easy way to get broadband bass control in the room. You can also use sealed panel type absorbers concealed as wood paneling around the bottom of the room.

Can you at least give us an idea of how many seats will be in the space and what type they will be? What is the floor covering like? Is the ceiling hard I assume and not a drop tile design? There are just a ton of variables.

Bryan

Rob Will

12-14-09, 11:48 PM

Thanks guys!

A lot of people seem to assume that I'm not covering all the bases;).
The reality is that over the last two years, I have received specific product recommendations from Real Traps and GIK. Tomorrow, I am expecting a call from a major speaker manufacturer regarding speaker depth and specific product recommendations. A few months ago, Christie flew in some projector equipment for us to look at. IMHO and regardless of all this manufacturer support, I have not even touched the surface of "turn key" design - and don't intend to.

The reason that I ask a lot of questions and read EVERY Ethan Winer article I can find is that I want to be an informed consumer and be able to ask relevant questions of vendors and design professionals. To be a better consumer, I have purchased FuzzMeasure and am using my guitar amp with an external mic for analyzing a test tone. I'm just getting started but so far, this acoustics stuff looks like a LOT of fun! I even signed up for an SAE Online course (surround sound and auditory environment). I hope it is a good class.

I figure that a public forum is for the open exchange of ideas and information. The Yellow Pages is for seeking work.

When the time comes to recommend a vendor. I'll probably remember the really smart ones who taught me the basics and helped our theater project be the best it could be:D.

Hey Ethan, you will think this is funny - I've been weighing samples of insulation board from construction sites to get the density - look what you started!

Thanks all for the info,
Rob

Techlord

12-15-09, 12:58 AM

erkq

12-15-09, 01:21 AM

I have heard and understand a lot about absorbing panels, I only have bass coming from my subwoofer, why would I need bass absorbers? My sub is truly non-directional, as in I could not tell you where it was in the room if I didn't know where it was.

To cut reflections resulting in standing waves and response nodes.

Techlord

12-15-09, 03:00 AM

To cut reflections resulting in standing waves and response nodes.

Come to think of it from time to time my sub does rattle the plates in my kitchen, I'll probably buy some bass tone tubes. Will bass absorbers cut down on vibrations in the room?

Dennis Erskine

12-15-09, 05:28 AM

Rob...the course may prove interesting and perhaps confusing without understanding of some the fundamentals. I'd suggest you purchase Floyd Toole's book "Sound Reproduction".

Terry Montlick

12-15-09, 09:57 AM

The proposed space is about 26' wide x 31' deep and has a 3-faceted vaulted ceiling 16' high.

...

My question would be: How can you take a space with so much reverb that it is hard to understand speech and make it a high quality theater? How can 1.5 second reverb times EVER be a good thing? :eek:

Thanks,
Rob
You add a lot of absorption. A space that size should have a reverberation time of under about 0.4 seconds in order to be a high quality movie theater.

Commercial cinemas have their walls lined with acoustically absorbing material. If this isn't possible, more creative solution may be used -- such as hanging a lot of large absorptive acoustical clouds or baffles. I once did a design (for a large residential space) which had fifteen of these, each 4x8 feet!

- Terry

bpape

12-15-09, 10:51 AM

Broadband bass control is there to:

- Help with specific bass response issues
- Help extend the bass response by eliminating cancellations
- Maximize intelligibility and tightness by getting the decay time into the proper range.

Bryan

Terry Montlick

12-15-09, 11:32 AM

giomania

12-15-09, 02:28 PM

You add a lot of absorption. A space that size should have a reverberation time of under about 0.4 seconds in order to be a high quality movie theater.

Commercial cinemas have their walls lined with acoustically absorbing material. If this isn't possible, more creative solution may be used -- such as hanging a lot of large absorptive acoustical clouds or baffles. I once did a design (for a large residential space) which had fifteen of these, each 4x8 feet!

- Terry

Terry,

Since I will be measuring my room to see what else I might need to add, what should the reverberation time in my ~21' x 27' room?

Thanks.

Mark

yacht422

12-15-09, 04:08 PM

One more note on acoustic treatment. For a reverberant, acoustically hostile environment (such as a typical classroom), research has shown that early reflections actually improve speech intelligibility. So a couple of acoustic panels (either absorptive or diffusive) at early reflection points should not necessarily be your first course of action.

- Terry
'classroom' as opposed to the typical 16 X 23 h/t? are early reflections not ALWAYS a "bad" thing??
for the diy in this thread, there are some things we ( I ) have taken as an absolute, among those things, reflection points. short of an rta intervention, how are we to know whether to do or not to do?(could experiment i guess - panels up - - - panels down - - panels half size etc, ad nauseum:rolleyes:)
walt

Digity8

12-18-09, 11:30 AM

I've used the mirror trick to find out the best place for my ATS acoustic panels, it seems its pretty close to the speaker itself, is that normal? :confused:

nathan_h

12-19-09, 01:11 PM

I've used the mirror trick to find out the best place for my ATS acoustic panels, it seems its pretty close to the speaker itself, is that normal? :confused:

Depends on your room. But it is 100 percent possible.

bpape

12-20-09, 09:43 AM

Just remember that you have a reflection point/area for each speaker to each seat on each wall. So, 3 speakers up front, 4 seats, 12 points on each wall for example.

Bryan

pepar

12-20-09, 10:30 AM

And then look up and down and, the direction that is commonly missed, to the rear. Absorbing the 12ms delayed reflection from the sound that goes the six feet past me to the rear wall and then the same six feet back made the most difference in my room.

Ethan Winer

12-20-09, 12:05 PM

Absorbing the 12ms delayed reflection from the sound that goes the six feet past me to the rear wall and then the same six feet back made the most difference in my room.

Yes, a lot of people overlook the difference between first reflections and early reflections. A wall closer than ten feet behind you gives early reflections if left untreated.

--Ethan

yacht422

12-22-09, 06:20 PM

Yes, a lot of people overlook the difference between first reflections and early reflections. A wall closer than ten feet behind you gives early reflections if left untreated.

--Ethan
when dealing with first and second reflections, is there a proper size wall panel for each? what might be considered too large?
walt

pepar

12-22-09, 07:47 PM

when dealing with first and second reflections, is there a proper size wall panel for each? what might be considered too large?
walt
It's all about the angles; the angles determine the correct size for first reflection point absorbers. (I don't think I've heard or anybody treating the second reflection points.) People talk about the mirror trick, but I prefer to think of pool shots. Angle of incidence equals angle of reflection. In any case, for each surface an analysis should be done projecting a line from each speaker to the surface and on to each listener. The points on the wall where these lines bounce define the size of the absorber.

glaufman

12-22-09, 10:44 PM

Yes, a lot of people overlook the difference between first reflections and early reflections. A wall closer than ten feet behind you gives early reflections if left untreated.

--Ethan

Yes, sometimes the terms get used interchangeably... perhaps you could give a quick refresher on the differences and their implications for the more confused among us... :o

Weasel9992

12-23-09, 10:53 AM

when dealing with first and second reflections, is there a proper size wall panel for each? what might be considered too large?
walt

Like Pepar said, there are a bunch of variables which lead to tons of options. Sometimes a 2'x2' panel is enough, but I'd say a 2'x4' panel is more reasonable as a starting place about 90% of the time.

Frank

Ethan Winer

12-23-09, 11:41 AM

when dealing with first and second reflections, is there a proper size wall panel for each? what might be considered too large?

Too large is not likely to be a problem, but too small is. As pepar said, it's not a point, but an area. And the size of the area directly depends on how far you are from the speakers and how far the speakers are from the walls. The farther away, the larger the area you need to treat. In a close-up situation a 2x2 foot panel could be enough. Once you're 10 to 12 feet away or farther, even 4x4 feet is not too large.

--Ethan

Ethan Winer

12-23-09, 11:44 AM

Yes, sometimes the terms get used interchangeably... perhaps you could give a quick refresher on the differences and their implications for the more confused among us... :o

A reflection is considered "early" if it arrives at your ears within about 20 milliseconds of the direct sound. Where the reflection comes from, or how many bounces it took to get to your ears, is irrelevant. All that matters is the time delay. A "first" reflection is literally that. A reflection that arrives at your ears on a single bounce, before other bounces.

--Ethan

glaufman

12-23-09, 03:20 PM

Thank you!

Dennis Erskine

12-24-09, 07:49 AM

Early reflections have two components ... time and intensity (loudness). A second dimension to "loudness" would be the delta between the "loudest" of the early reflections and the softest of those reflections as compared to the direct sound. The frequency at which that will occur will change based upon the primary (direct) distance assuming you keep the same delay (say 20ms) in the ITDG. As the primary distance increases, the degrees off axis from the speakers will also change. Taken with the quality of the off axis response at the seating locations will then begin to suggest a strategy for treatment (diffusive, absorptive, etc.)

Ethan Winer

12-24-09, 10:26 AM

Early reflections have two components ... time and intensity (loudness).

Good point Dennis. If early reflections are at least 15 dB below the direct sound, the resulting comb filter peaks and nulls are more tolerable than when they're only 5 dB reduced.

--Ethan

glaufman

12-24-09, 02:58 PM

avare

12-24-09, 03:18 PM

Umm...err... ITDG?

Initial Time Delay Gap

Merry Christmas, with no delay,
Andre

glaufman

12-24-09, 03:28 PM

Geez, we have an acronym for everything, don't we!

Techlord

12-24-09, 05:00 PM

I have my work cut out for me, my THX speaker system has the LCR speakers tweeters angled 4.7 degrees away from the sweetspot while my center speaker has the tweeter angle 4.7 degrees up. I will probably angle the center speaker down rather than up since it's above the listening position, as for angling my LR speakers in is out of the question! I have already tried that and seem to loose the stereo imagining completely, like there out of phase. I think some absorbers in towards the corners of the room will be needed.

Question: once I calibrate all my speakers for the listening possition(sweetspot), am I supposed to find the peak loud areas with my SLPM in the room and treat those areas with absorbers?

Happy Christmas Eve,
Tecklord. :)

Ethan Winer

12-25-09, 11:59 AM

am I supposed to find the peak loud areas with my SLPM in the room and treat those areas with absorbers?

The first place for bass traps is in the corners. Understand that rectangle rooms have 12 corners, not just four. After the corners are treated, the next place is the rear wall behind the listening position. If that wall is closer than ten feet behind you, the traps need to absorb mids and highs as well as bass.

--Ethan

Techlord

12-25-09, 04:29 PM

The first place for bass traps is in the corners. Understand that rectangle rooms have 12 corners, not just four. After the corners are treated, the next place is the rear wall behind the listening position. If that wall is closer than ten feet behind you, the traps need to absorb mids and highs as well as bass.

--Ethan

I have a foot behind me to the rear wall. I have noticed big difference in surround sound quality and placement of sounds by leaning my head forward a foot, the surround sound effect is more easily heard. I have moved my couch forward 1ft., what a big difference it makes! That's the most effective thing I have even done with speaker positioning that made the most difference! Before the surround sound sounded diffused and reflected!

Goshwin

12-25-09, 10:30 PM

Ethan Winer

12-27-09, 11:54 AM

So less then 10 ft means no sound diffusers back there?

Not necessarily. My point is that when the rear wall is closer than about ten feet, the reflections at mid and high frequencies are considered "early" and should be addressed. I've used diffusors as close as a few feet behind with good results.

--Ethan

kevinzoe

12-27-09, 02:58 PM

Not necessarily. My point is that when the rear wall is closer than about ten feet, the reflections at mid and high frequencies are considered "early" and should be addressed. I've used diffusors as close as a few feet behind with good results.

--Ethan

~~~~~~~~~~~~~~~~~~~~~~
Goshwin wrote: "So less then 10 ft means no sound diffusers back there?
I was thinking of putting a line of diffusers across the wall at 3/4 level. "

Goshwin, if you're planning on putting diffusion on the back wall behind the listening chair, then ponder the following considerations:

1.) LOW FREQUENCY OPERATING RANGE - as diffusers need to handle long wavelengths and should work down to your room's Schroeder or Transition frequency (typcially 300-500Hz), pick a design with the deepest cell/well depth as you can find or build yourself, with the limitation being distance from diffuser to listening chair (see point 2. below).

2.) DISTANCE BETWEEN BACK WALL & LISTENING CHAIR - should be 3 wavelengths of the lowest frequency that the diffuser will perform well at, so that the sound coalesceses before it reaches your ears and troublesome lobbing isn't heard. If you're considering the more popular QRD- or Skyline-types of diffusers, then a conservative calculation of the lowest frequency wavelength will be to multiply the deepest cell depth in inches by 2 to get the entire wavelength of the lowest freq that the diffuser will work well at and then express it in feet by dividing it by 12 and then divide it into the speed of sound of 1130. For example, a Skyline of max cell depth of 7.5" will perform well down to 904Hz [ 1130/((7.5*2)/12) ]. The diffuser will continue to perform to lower frequencies but with diminishing ability. Now calculate 3 wavelengths of 904Hz as follows: 1130/904 * 12 * 3 = 45inches. So you'd need to sit at least 45inches away from the rear wall with a diffuser of max depth equal to 7.5 inches.

3.) DIFFUSER PLACEMENT - be sure they are centered at ear level so 3/4 height may/may not fit the bill depending on seating height and of course your height! Also it should cover 2ft below and above your ear level so a minimum dimension of 4ft.

4.) WALL COVERAGE AREA - Prof Trevor Cox a diffusion expert, told me that some general diffusion principles exist, most relevant is the less periodicity the more diffuse the scattering. Dr Floyd Toole concurs saying "these designs get better as they get larger." So, to improve scattering efficiency over your desired wall area, choose a Skyline diffuser with the largest prime number or QRD diffuser with the largest number of wells to cover the desired area, and in both cases a max cell/well depth as calculated above. So it's better to have one large diffuser than several smaller ones put together. For a polyfuser pick one with at least a 12" radius however when combined with other polyfusers it loses its ability to diffuse low frequencies, so space them apart, change angles, and change their radius depths too if possible.

Hope these other considerations are useful and helpful.

yacht422

12-28-09, 02:16 PM

re: item #2
how does one treat a two row room, when the rear row is 14" from the wall? I have no flexibility regarding the chair(s) location. "they gotta be there".
walt

Kal Rubinson

12-28-09, 02:38 PM

re: item #2
how does one treat a two row room, when the rear row is 14" from the wall? I have no flexibility regarding the chair(s) location. "they gotta be there".
waltAbsorbtion, not diffusion.

kevinzoe

12-28-09, 02:52 PM

re: item #2
how does one treat a two row room, when the rear row is 14" from the wall? I have no flexibility regarding the chair(s) location. "they gotta be there".
walt
Yacht422 - with only 14" behind the last row you really only have 1 viable option which is for broadband absorption in the centre of the back wall. As a 14" clearance is not much room to play with, I'd suggest you consider the type of broadband bass trap called "membrane or diaphragmatic" which works on the principle of absorbing sound most efficiently when the sound wave's pressure is maximized, which is right at the point on impact with the wall - so diaphragmatic absorption traps hang on the wall and are usually thin enough to work with your 14" limitation. The other absorption option most seem to select is a "resistive" broadband bass trap which should be a minimum of 4" thick with the thicker the better. However, the resistive traps works best when the sound air partical speed is maximized (not its pressure) which is one-quarter of the wavelength's distance out from the wall. So a 100Hz has a wavelength of 11.3ft so one-quarter equals 34", clearly beyond your 14" distance. Your 14" distance equates to about one-quarter of a 250Hz frequency so the resistive trap type may still be acceptable and is typically less costly than the thinner diaphragmatic type.

You might consider diffusion on either side of the broadband absorption if the distance between it and the rear seats warrants it.

Weasel9992

12-29-09, 05:58 PM

You might consider diffusion on either side of the broadband absorption if the distance between it and the rear seats warrants it.

Good point Kevin...diffusion isn't totally precluded. It just can't be placed instead of absorption.

Frank

yacht422

12-30-09, 05:40 PM

kal: kevin: weasel9992: many thanks for the insights and the defining math.
i am a diy guy - will fab 4" thick absorbers for the rear wall(currently 2")[ two - 2' X 4' X 2" covered and framed] soooo much to learn, so little time.
( we used to race sailboats on the chesapeake bay - and i thought THAT was complicated! HAH!)
walt

Weasel9992

12-31-09, 10:32 AM

i am a diy guy - will fab 4" thick absorbers for the rear wall(currently 2")[ two - 2' X 4' X 2" covered and framed]

Cool...that'll work a lot better than 2".

Frank

yacht422

12-31-09, 01:40 PM

Cool...that'll work a lot better than 2".

Frank
thx, and a happy new year!:)
walt

captainkidd

01-02-10, 09:42 AM

Hello all! I am building/setting up a dedicated theater room and looking for some help in regards to placement of 6 newly constructed acoustic panels. The panels are 2'X4' constructed with Owens Corning 703 2" fiberglass insulation and will stand about 2.5" off the walls.

I better start with a rundown of my setup. The room is a big rectangle but only about 40% of it is the 'theater'. The rectangle is 30'X20'X16' high and I am using the first 12' for my theater. The 125" projector screen is placed on the end of one long wall with seating positioned along the opposite wall, about 17' from the screen.

My Receiver is a Denon AVR 590 and speakers are a 5.1 system of Klipsch WF-35 towers and matching center with smaller surrounds and an Energy 200 watt, 8" sub. The speakers are placed such that the two on the left side are out in space since there is no dividing wall on the left side to separate the theater area from the gaming area.

The room is a converted RV garage which is why it is so tall. The long walls (front and rear) are concrete block, the right hand (near) wall is sheet rock and the left hand (far) wall, which is about 18' away from the left side of the 'theater' area is a giant garage door. The floor is VCT tile over concrete.

The sound in the room is extremely lively with a lot of echo and I am having a hard time hearing dialogue in movies. I think the bass sound effects might be drowning out the dialogue because when I listen to music that doesn't have much bass the words are crisp and clear.

So, on to my question. I have built 6 of these,

http://www.instructables.com/id/Make-accoustic-panels-for-your-recording-studio-or/

And am looking for advice on where to install them. I am not sure weather to orient them horizontally or vertically and weather to use them in corners as bass traps, at early reflection points on the near wall or on the rear wall. There is not enough room between my screen and the right hand wall/floor to position one of them in there at a 45 degree angle so that option is out.

I wish I could draw the room to help show the layout but don't know how. Hopefully my description is good enough. So, any suggestions?

yacht422

01-02-10, 11:52 AM

Can you build a room in a room? you can make a manageable rectangle out of a few studs and some drywall -all diy - and then there will be a room you can easily 'sound' treat. :)
Given the cubes of the existing space, you'll need way more amp power and far larger sub(s) and lots of sound panels to generate satisfying sound ( as opposed to noise:eek:) - and of course, carpeting.
there are industry men that monitor this site and will provide useful insights - but - trying to treat a room of this size is almost industrial in scope, imho.
good luck
walt

Pete

01-02-10, 04:13 PM

Kal Rubinson

01-02-10, 06:57 PM

There seems to be a multitude of manufactures that are selling acoustic treatments. If there were a CW short list of the most competent and comprehensive vendors -- specifically with HT in mind -- who would be on it?Most of them are mentioned and wrung out here in this forum. For a starting list, take a look at the links provided by Rives Audio: http://www.rivesaudio.com/resources/links/frame.html

WWWestonC

01-02-10, 08:30 PM

Although I'm constructing my first and a low budget theater, you guys have me convinced to take the time and try and incorporate some acoustical treatments.

Where I'm at now, the walls/soffits are mudded and taped, the stage and cabinets are built, and the riser will be built this week.

I went to Wal-mart and picked up some black fabric (12 yards of it) and am planning to spray with the 3M fire retardant. I'm going to call HVAC contractors this week to try to secure some Linacoustic.

My question is can someone direct me to a good thread with pictures on the install of a similar build. I'm hoping for a thread with pictures detailing the install of the fabric / acoustical treatments. I was planning on painting the wall red above ear level all the way around.

Appreciate any help you can provide.

Here's a link to my build thread which has some (weak) pictures. I can get more if needed.

http://www.avsforum.com/avs-vb/showthread.php?t=1205353

Kemet

01-02-10, 09:07 PM

Can OC Foamular 150 panels be used as acoustical panels to absorb early reflection frequencies behind a speaker or would they just be wasting space?

MikeWojcik

01-02-10, 11:35 PM

I know I've read in this forum that speakers should not be placed behind Anchorage since it is less transparent than , say 701. Would a subwoofer be impacted as well?

Thanks!

MarkMac

01-03-10, 05:32 PM

Can OC Foamular 150 panels be used as acoustical panels to absorb early reflection frequencies behind a speaker or would they just be wasting space?
I don't know if there is any acoustic data available for this product, but I would guess that it would be a very poor choice for an absorption material. This a rigid foam insulation product, and I would expect that if would be very reflective...(but I don't have any data to back that up).

Dennis Erskine

01-04-10, 07:11 AM

This is a closed cell foam product and would not provide the absorption benefit you're looking for.

Weasel9992

01-04-10, 10:29 AM

There seems to be a multitude of manufactures that are selling acoustic treatments. If there were a CW short list of the most competent and comprehensive vendors -- specifically with HT in mind -- who would be on it?

Budget, the amount of help you need and how you want to install things all factor into who you use.

Frank

pepar

01-04-10, 10:32 AM

Noob question, but I want to be sure ...

Will a simple waterfall measurement at my primary listening position give me all the data I need to determine whether the reduction in absorption and addition of diffusion that I *think* I need is .. really .. needed. :o

TIA!

Jeff

CJO

01-04-10, 10:44 AM

I know I've read in this forum that speakers should not be placed behind Anchorage since it is less transparent than , say 701. Would a subwoofer be impacted as well?

Thanks!

I'm no professional, but I wouldn't think that there would be an issue with bass. The Anchorage reflects higher freqencies significantly more than 701, which is why it isn't suggested for full-range speakers.

CJ

HT1

01-04-10, 04:40 PM

I have a multi-purpose room that is half bar and home theater. We had our first gathering over the holidays mainly in the bar half of the room where I noticed that conversations where really loud. I'm guessing due to room echo since the bar half is tile floor, wood bar and the entire room is drywall. My question is how can I tame some of this echo? I do not have any fancy measuring device and wouldn't know what to with them if I did. But I would like to build some panels to hang on the walls just to do some low tech experiments to see if I can tell a difference by ear. From what I have read I'm guessing I need sound absorption material? My room dimensions and layout are all in my signature thread. This is has been my first attempt at this bar/ht thing so I'm learning thru trial and error and I go. Any suggestions would be appretiated.

forestmoonstudio

01-04-10, 05:57 PM

I am doing a HT from an exisiting room. Walls are drywall. My wife wants hardwood floors. We are going to get a big area rug that will take up alot of the floor space. The room is 16'x14'. The 106'' screen will be on front wall. The back wall is a Bay window that will have block out curtains covering it. One side wall will have a door and a column. The other side wall will have 3 columns built onto it. I was thinking of building panels for the walls out of covered OC 703.
Now getting to my real question. Will putting framed movie posters on the acoustic panels basically void out the panels?

Would the pink or blue insulation foam work good for panels instead of the fiberglass?

MikeWojcik

01-04-10, 09:16 PM

Thanks CJ

that is what i was thinking (although without the "qualifications" to do so).

Can any experts confirm? Question is whether subwoofer frequencies are sufficiently less impacted by the use of GOM Anchorage fabric in front to allow that without sound quality impacts...

Thanks
Mike

I'm no professional, but I wouldn't think that there would be an issue with bass. The Anchorage reflects higher freqencies significantly more than 701, which is why it isn't suggested for full-range speakers.

CJ

Kemet

01-04-10, 10:24 PM

This is a closed cell foam product and would not provide the absorption benefit you're looking for.

Thank you very much for the confirmation on Foamular 150, I was hopeful it might but didn't expect it to provide much benefits.

Bass Slut

01-05-10, 12:47 AM

i have an open unfinished poured concrete basement, with some carpet on the floor for office space, wife all upstairs

i have 7.6' x 22.6' x 38.6'
which gives me resonances @ 75hz x 50hz x 14.6hz

i used 3 old speakers from the eighties with 2.0 cubic feet of volume each.
i blanked off the holes & made Helmholtz resonators to spec, one for each dimension

while playing music, i used rolled cardboard & pvc for telescopic ports
it all seemed to tune in quite audibly
then i made the tune sound right by padding the ring time efficiency with rags

the 75hz box got a piece of wood over a 4" open hole, to create an adjustable valve, tuned right in, took 1.6 rags
the half moon finished port appeared close to calc, 2.8"
very audible, to the middle of the basement

the 50hz box, i suspect may be padding the room & maybe the peak in my band pass
tunes right in with 2.0 cu' box, 3.75" id port, 3.6" long
about 1/8" longer than calc, probably stuff still in speaker box reduced actual volume
after listening in the middle of better sounding basement, i added just another 15% of a rag to the 50 hz box
very audible, to the middle of the basement

the 14.6hz box i used a 2.5" ID port, 14.5" long
my third speaker cabinet from the eighties was only 1.77 cu'
& this port tunes 1/4" shorter than calc
i only have 15% of a rag in this box for ring time
if you stuff in one too many rag, it goes to mud instantly
this box does more to clean up the sound than anything
it doesn't appear to eliminate allot of obvious sound, but it's a necessity

i located all three resonators @ the stacked subs for the most energy
which is 6' from the computer/main listening area
i have two stacked 6.6 cu' band pass boxes stacked in the corner, 45 degrees
one port firing @ corner ceiling, one port @ corner floor

placement seemed to be critical to get the most out of them
almost a phasing issue the way they sound good
i tried various arrangements of the resonators around the sub & the best seems to be:
75hz box on top of the subs firing @ ceiling
50hz box on floor, straight out from the back of the 45 degree subs, where it's in phase w something

the 14.6hz box sounds good pointed @ my head
it would make a nice hat
i didn't think it would help much, but it's octaves of 30 45 60
it really cleans up the sound & it's root freq is narrow & fatiguing
it's also on the floor, the furthest out, next to the 50, pointing up

it sounds really really good
it seems like it helped the nulls i experience in the middle of the basement just as much
the ringing is still serious @ the rear corner, next to the furnace

i could listen for days now

i wonder if there's helmholtz dampening effects over a range of freqs & corner loaded calcs, graphs, plots, models over room space??

it sounds good & everything, but i haven't seen much info on efficiency anywhere

would i have a better effect over the entire basement if i used a 5' long 4" diameter port, instead of a 1' long 2.5" diameter port, on the 14.6hz box ??

would i have a better effect over the entire basement if i used a larger box, how much db ??

great forum

Bass Slut

01-05-10, 09:35 AM

oh well, so much for the longest first post evar :confused:

looks like i made a math error on room width & should be targeting 25hz, not 50
for anyone that could read that

which means 25hz & 125 hz aren't dampened

maybe i'll get out & buy some 4" pvc today

i highly recommend helmholtz boxes for concrete rooms:D

Bass Slut

01-06-10, 12:21 AM

i have an acoustic consulting friend i called today & we spoke @ length
his thoughts were the 38 foot long section of the basement was irrelevant
but the width of the room would be ringing an octave over it's width @ 50hz loud
he said i should keep the 50 hz box because it would be 6db more influential than the 25hz box & there' more music there

it turns out after remeasuring & claculating that my 14.6hz box with it's 1 inch longer port & uncalculated innards volume was actually tuning to 25 hz
that's why it was so obvious to tune with the 50 hz box next to it
home on all three port adjustments is audible to the millimeter
concrete room is nice

to sum it up:
3 helmholtz resonators @ 75hz, 50hz, 25hz placed @ sub corner
75 hz matches floor to ceiling resonance
25 hz matches the width of the room
50 hz offers more help with width of room, octave up
best sounding sub i've evar had

this forum has been a gold mine & i'm sure there's lots more to learn :)

maxfli

01-06-10, 12:10 PM

Hi all,

I am ready to add treatment to my converted 2-car garage HT room. One of the challenges I have is in the corners for adding bass traps. Each corner has a 9" x 9" pillar from floor to ceiling that restricts the area for using certain products.

I've decided on cutting product to fit the area. I understand that foam products though maybe easier to work with aren't good for bass-trapping. So, which of these products would be easier to work with for cutting into sections and fitting into a corner: OC 703, Johns Manville IS 300 or 600, or Certainteed OEM 300 or 600?

Secondly, if 3" of OEM 600 is 64% absorptive at 125 Hz, does it hold that 2 sheets of 3" OEM 600 would be ~ 128% aborptive?

Thanks,
Max

kevinzoe

01-06-10, 02:19 PM

Max - regarding your 2nd question, I don't think it's as simple as just doubling the absorption effectiveness for the given 125Hz frequency. (After all, what does 128% mean?!)

At the very best I would think that the 1st panel being 64% effective (whatever that truly means) lets 36% through it so adding a 2nd panel (behind the 1st panel) will absorb 64% of the 36% that it 'sees' or 23%. So I think that the very best you could hope for is 87% (64%+23%), but that is likely stretching things as there will be sound waves that reflect off of it at higher frequencies and propogation loss just through the air as well . . . The thicker you can make the traps the better off it will perform down to lower frequencies.

For what it's worth, my bass traps range in thickness from 12" to 35.5" and have a 6.5" air space behind them all which roughtly equates to a quarter wavelength of 500Hz which is an estimated transition zone (or Shroeder frequency) for my sized room. You might want to calculate what the 1st, 2nd, and 3rd modes are of the garage's dimensions (i.e. length, width, and height) and base the trap's thickness around at least the 3rd mode of each dimension and preferable the 2nd mode too - the first mode of the longest dimension will likely require too thick a fibreglass filled trap to be practical. So if your length is say 25feet, then the 1st, 2nd and 3rd nodes are at 22.6Hz, 45.2Hz and 67.8Hz. (Calculation: speed of sound 1130 divided by 2 times the length of 25ft = 22.6Hz) So, building a trap to deal with the length's 3rd mode of 67.8Hz requires that the bass trap extend out from the wall to a thickness equal to one-quarter of the 67.8Hz wavelength which is 50" !! (Calculation: 1130/67.8*12=200"; 0.25*200=50") It might be more practical to use these calculation for the smaller two dimensions (width and height) and use a parametric eq to deal with remaining bass mode peaks.

If you're building 'resistive-type' bass traps filled with some kind of fibreglass, then remember that they work best when there is an air space behind them, in other words you might consider leaving the 9" airspace to accommodate your pipes. You can always put the bass traps in the opposite walls corners closer to the wall (i.e. smaller air space between wall and edge of trap) as a mix of things often helps to balance things out.

Good luck.

maxfli

01-06-10, 09:09 PM

Thanks for your response Kevinzoe. Your explanation makes alot of sense to me. I had always intended to 3X or 4X the 3 inches of product to get closer to a 100% absorption. I like the idea of placing the absorbers away from the wall to increase the rate.

The area where these will go is on a stage that is only about 4' deep at the corner. I'm going to trade out my SVS PB13 subs for their PC 13 cylindar subs to allow for treatment materials. The PB13 are great subs, but are beasts and consume about 2 feet of the 4 feet of stage, the pillars another 9", leaving little or no room for treatment. The PC13 have a much smaller form factor and are a better choice for my size room (20 L x 16 W x 9 H)

I will also look at the calculations as you've suggested, but may have to sacrifice some treatment size to keep the asthetics of the room. The room was built with visual appeal in mind. I'm just now getting to acoustic treatments and plan to treat as much as possible, but may go to a SVS sub equalizer if I don't have room to do the correct size of treatment.

I still am interested in knowing which of these materials is easier for cutting and shaping for the space I have.

Thanks again,
Max

bob53

01-06-10, 10:04 PM

Hi everyone,

I was hoping to solicit some help re: the appropriate acoustical treatments for my 2-channel / HT environment in my basement family room.

The room:
The room is irregular in shape (see pics below) but the main component is ~ 15 x 20 x 8.5 (ft). The room is open in the rear to the staircase and the HT system is not centered with the space. A fireplace was removed from the room to provide the room in the "space / enclave / nook" behind the proposed AT screen.

The systems:
The front screen wall will be AT, composed of Seymour XD material and GOM for the surrounding framing. Behind this wall, the plan calls for the speakers (3 Triad gold monitors, stand mounted), HT sub (1-2 JL F112s), and 2-channel boundary woofers (Lyngdorf W210s x 2 ).

The issues:
My 2-channel system relies upon the Lyngdorf software/hardware - including the two boundary woofers. For those not familiar with the Lyngdorf Room Perfect system, the boundry woofers exploit the room by aiming their 4 10 inch speakers at the 2 corners to produce bass, mid-bass, and midrange (the boundary woofers are, by design, digitally crossed over at 300-400 Hz!!!) while retaining 95 dB sensitivity and consuming minimal power. The mains only need to handle frequencies beyond 300-400 Hz.

http://www.lyngdorf.com/index.php?option=com_content&task=view&id=27&Itemid=55

http://www.lyngdorf.com/index.php?option=com_content&task=view&id=76&Itemid=43

http://www.lyngdorf.com/downloads/product_descriptions/roomperfect_productdescription_english.pdf

So my concern is that traditional acoustic treatments behind the screen wall may negatively impact the performance of this non-traditional arrangement, as the woofers rely upon reflections where bass traps and absorbing materials are traditionally placed.

Questions:
1. Should any treatments be used along the front wall? The Triad speakers are not ported, neither is the JL F112, and I assume this may be of some benefit in this case re: reflections behind the screen wall.

2. Should I still treat first reflection points within the room? Is the right.
reflection point less important given the fact it is much further away vs. the right.

3. What can be done about the open staircase at the back wall? It occupies the entire back wall (no door to close, etc.)

While I understand the basics of acoustics and treatments, specific recommendations would be helpful as I am still quite unfamiliar with the finer points of acoustic theory as it relates to this discussion.

Here are drawings of the room, a perspective of the room from the rear, and a more detailed drawing of the proposed screen wall.

http://i17.photobucket.com/albums/b58/inflammation/HTbasementplan.jpg

http://i17.photobucket.com/albums/b58/inflammation/basementperspective_iteration2.jpg

http://i17.photobucket.com/albums/b58/inflammation/HTbasicplacement.jpg

Thank you in advance for the assistance,

Bob

bighoot

01-06-10, 10:10 PM

Quick question, the celing in my basement theater is approx 7ft. There is a 8" beam running accrost the room at the mid point, I have been wanting to remove the beam and replace with Steel I beam so the celing would be flush. Got to wondering if I where to drywall down tho the beam and then taper the celing from the beam to the floor joist( it would appear that the celing drops in the middle of the room and tapers back to the front and read walls) would be 8' over a 10ft span. Taking out the beam is going to be a PITA so I am looking for solutions. Saw this in a commercial theater not sure if it was for accoustics or something else. Ideas

yacht422

01-07-10, 10:34 AM

It's all about the angles; the angles determine the correct size for first reflection point absorbers. (I don't think I've heard or anybody treating the second reflection points.) People talk about the mirror trick, but I prefer to think of pool shots. Angle of incidence equals angle of reflection. In any case, for each surface an analysis should be done projecting a line from each speaker to the surface and on to each listener. The points on the wall where these lines bounce define the size of the absorber.

ARE THERE NO SIDE WALL SECOND REFLECTION POINTS?
IN OTHER WORDS, TREATING THE FRONT OF THE ROOM SIDE WALLS (1st r/p) is all that is needed for SIDE WALLS?
FRONT AND REAR WALLS -DIFFERENT DISCUSSION, FOR NOW.
WALT

pepar

01-07-10, 11:24 AM

ARE THERE NO SIDE WALL SECOND REFLECTION POINTS?
IN OTHER WORDS, TREATING THE FRONT OF THE ROOM SIDE WALLS (1st r/p) is all that is needed for SIDE WALLS?
FRONT AND REAR WALLS -DIFFERENT DISCUSSION, FOR NOW.
WALT
Speaker to a wall to another wall to your ears? Yes, of course. I've just never heard of anyone treating for that though. Come to think of it, I've never even heard anyone refer to second reflection points. I'm sure the real acousticians here have a better answer, but my guess is that beyond the FIRST reflections, the next ones are more diffuse, more delayed and meld into the reverberant field.

Actually, I think front wall and rear wall *are* part of the same discussion if you want to improve your acoustics.

yacht422

01-07-10, 12:45 PM

speaker to a wall to another wall to your ears? Yes, of course. I've just never heard of anyone treating for that though. Come to think of it, i've never even heard anyone refer to second reflection points. I'm sure the real acousticians here have a better answer, but my guess is that beyond the first reflections, the next ones are more diffuse, more delayed and meld into the reverberant field.

Actually, i think front wall and rear wall *are* part of the same discussion if you want to improve your acoustics.
yes! I have front and rear treatments, but not to the degree of your h/t. This is still a work in progress. The additional work i do follows the knowledge i gain from this thread.:)
attached is a pdf of the right wall showing the wall treatments walt

pepar

01-07-10, 01:24 PM

yes! I have front and rear treatments, but not to the degree of your h/t. This is still a work in progress. The additional work i do follows the knowledge i gain from this thread.:)
attached is a pdf of the right wall showing the wall treatments walt
Wow, Walt, nicely done. WRT the surround - if it is a dipole or bipole, the absorber on which it is mounted is likely interfering with it providing envelopment. FWIW, I probably wouldn't have any treatment there unless it was needed to manage RT60.

Jeff

yacht422

01-07-10, 02:51 PM

Wow, Walt, nicely done. WRT the surround - if it is a dipole or bipole, the absorber on which it is mounted is likely interfering with it providing envelopment. FWIW, I probably wouldn't have any treatment there unless it was needed to manage RT60.

Jeff
i can remove, just sits on the dipoles(2 cones face to front, one 6" into the room, two cones to the rear)
the problem i have been attempting to resolve is reflected in the chart attached.
[i use the anthem room correction software (ARC) which works along the same lines as audessy(sp).]
there is a major hump in the lf/rf as well as an over/under swing at the 500 to 2500 range in the dipoles. i had hoped that the wall treatments hanging on the di's would solve the 'di' problems - did not, but, i never took them down.
still looking for solutions to those issues
walt

johnbomb

01-07-10, 04:00 PM

Has anyone utilized drywall for bass trapping? I'm planning on installing 16" to 32" wide panels of drywall around the room with thicknesses alternating between 1/4", 1/2", and 5/8", backed with pink insulation.

By adding weight selectively to the panels, I hope to tune their resonances to those of the involved axial room modes above 80hz (I'm building a "double bass array" to counteract those below 80hz, as linked below).

http://www.avsforum.com/avs-vb/showthread.php?t=837744

Thanks,
John

kevinzoe

01-07-10, 06:23 PM

ARE THERE NO SIDE WALL SECOND REFLECTION POINTS?
IN OTHER WORDS, TREATING THE FRONT OF THE ROOM SIDE WALLS (1st r/p) is all that is needed for SIDE WALLS?
FRONT AND REAR WALLS -DIFFERENT DISCUSSION, FOR NOW.
WALT

******************************
Yacht422(a.k.a.Walt):
Regarding your question about treating second reflection points - I had this exact discussion with Dr Sean Olive over the phone recently and he said that 2nd reflection points would not likely require treatment due to several factors that reduce the specular intensity of a 2nd reflection. These factors that reduced the 2nd reflection 'loudness' level included propogation loss before and after the 1st boundary impact (1st reflection point), the impact of the 1st reflection point itself, and the reduced reflected energy if the 1st reflected point was an absorber or diffuser.

So to your point IF you're going to treat side wall or ceiling 1st reflection points, you can forget about treating 2nd reflection points (which is likely a good thing as they could be nasty to pin point without some kind of ray tracing system). I'd agree with Pepar in that reflections after the 1st reflection points become part of the indirect and reverberant sound field.

For music-only rooms (like what I have), treating 1st reflection points isn't really required (unless large slap echo exists between hard parallel surfaces) as Dr Floyd Toole points out in his latest book. The reflections actually add to the sense of listener envelopment and apparent sound source width and helps create a low "Inter Aural Cross-Correlation" which is a fancy scientific term that means that the left and right ears are hearing different things - a high IACC means the ears are hearing very similar or the same thing. Toole goes on to say that treating 1st reflection points is a good idea if you're a musician who is mastering their music or someone doing comparative stereo component evaluations (magazine reviewers?!).

Clear as mud? :)

yacht422

01-07-10, 06:38 PM

******************************
Yacht422(a.k.a.Walt):
Regarding your question about treating second reflection points - I had this exact discussion with Dr Sean Olive over the phone recently and he said that 2nd reflection points would not likely require treatment due to several factors that reduce the specular intensity of a 2nd reflection. These factors that reduced the 2nd reflection 'loudness' level included propogation loss before and after the 1st boundary impact (1st reflection point), the impact of the 1st reflection point itself, and the reduced reflected energy if the 1st reflected point was an absorber or diffuser.

So to your point IF you're going to treat side wall or ceiling 1st reflection points, you can forget about treating 2nd reflection points (which is likely a good thing as they could be nasty to pin point without some kind of ray tracing system). I'd agree with Pepar in that reflections after the 1st reflection points become part of the indirect and reverberant sound field.

For music-only rooms (like what I have), treating 1st reflection points isn't really required (unless large slap echo exists between hard parallel surfaces) as Dr Floyd Toole points out in his latest book. The reflections actually add to the sense of listener envelopment and apparent sound source width and helps create a low "Inter Aural Cross-Correlation" which is a fancy scientific term that means that the left and right ears are hearing different things - a high IACC means the ears are hearing very similar or the same thing. Toole goes on to say that treating 1st reflection points is a good idea if you're a musician who is mastering their music or someone doing comparative stereo component evaluations (magazine reviewers?!).

Clear as mud?
but - - - it covers the ground!
Regrettably, my task is somewhat more complex than 'A' chair with all the audible firepower pointed at it.
I have 8 leather chairs and the Master Audio sound track coming from all sides.
I'm not complaining, just observing a fundamental difference in your and my needs.
I've read thru two how to books, one by jim smith, the other by a reviewer, and both tomes concentrate on the single chair audiophile - not the 8 chair h/t.
so - - - i continue to read and post and slowly kind folks such as yourself offer guidance.
Thanks - and, any additional insights are appreciated.
walt

kevinzoe

01-07-10, 07:57 PM

but - - - it covers the ground!
Regrettably, my task is somewhat more complex than 'A' chair with all the audible firepower pointed at it.
I have 8 leather chairs and the Master Audio sound track coming from all sides.
I'm not complaining, just observing a fundamental difference in your and my needs.
I've read thru two how to books, one by jim smith, the other by a reviewer, and both tomes concentrate on the single chair audiophile - not the 8 chair h/t.
so - - - i continue to read and post and slowly kind folks such as yourself offer guidance.
Thanks - and, any additional insights are appreciated.
walt

Walt - much of Dr Floyd Toole's latest book is dedicated to HomeTheatre so your multi-person requirements are addressed in it. I scimmed that section of course so I can only recommend you borrow/buy it.

yacht422

01-08-10, 12:10 PM

******************************
Yacht422(a.k.a.Walt):
Regarding your question about treating second reflection points - I had this exact discussion with Dr Sean Olive over the phone recently and he said that 2nd reflection points would not likely require treatment due to several factors that reduce the specular intensity of a 2nd reflection. These factors that reduced the 2nd reflection 'loudness' level included propogation loss before and after the 1st boundary impact (1st reflection point), the impact of the 1st reflection point itself, and the reduced reflected energy if the 1st reflected point was an absorber or diffuser.

So to your point IF you're going to treat side wall or ceiling 1st reflection points, you can forget about treating 2nd reflection points (which is likely a good thing as they could be nasty to pin point without some kind of ray tracing system). I'd agree with Pepar in that reflections after the 1st reflection points become part of the indirect and reverberant sound field.

For music-only rooms (like what I have), treating 1st reflection points isn't really required (unless large slap echo exists between hard parallel surfaces) as Dr Floyd Toole points out in his latest book. The reflections actually add to the sense of listener envelopment and apparent sound source width and helps create a low "Inter Aural Cross-Correlation" which is a fancy scientific term that means that the left and right ears are hearing different things - a high IACC means the ears are hearing very similar or the same thing. Toole goes on to say that treating 1st reflection points is a good idea if you're a musician who is mastering their music or someone doing comparative stereo component evaluations (magazine reviewers?!).

Clear as mud? :)
am i to understand that treating first reflection points is not necessarily necessary, in Dr. Tooles opinion, if we are treating a home theater? This certainly flies in the face of prevailing wisdom. Obviously, i'll need to read the book.
thx again
walt

pepar

01-08-10, 12:21 PM

am i to understand that treating first reflection points is not necessarily necessary, in Dr. Tooles opinion, if we are treating a home theater? This certainly flies in the face of prevailing wisdom. Obviously, i'll need to read the book.
thx again
walt
Walt, there are those that are saying early lateral reflections are good. Ceiling, floor and rear wall are still treated. You're right about conventional wisdom, and I really have a hard time abandoning my thinking that the room should be neutralized as much as possible and the speakers should re-create the environment the artist created. New tech from companies like Audyssey and Dolby are aimed at expanding the front soundstage.

Jeff

yacht422

01-08-10, 03:31 PM

Weasel9992

01-08-10, 03:41 PM

Interestingly enough, they were not concerned about first reflections, but, rather, controlling the lower notes...

I know what they're getting at there, but there's a balance to be struck. It's not one or the other...it's both.

How do we know what to do? With most rooms of a certain size and shape, used for a particular purpose, there are a number of basic steps you can take to solve a bunch of the issues as they tend to be the same or similar from room to room. From there you have to be more targeted based on the clients preferences, specific equipment employed and the particulars of room geometry, furniture placement and so on.

Frank

yacht422

01-08-10, 04:49 PM

I know what they're getting at there, but there's a balance to be struck. It's not one or the other...it's both.

How do we know what to do? With most rooms of a certain size and shape, used for a particular purpose, there are a number of basic steps you can take to solve a bunch of the issues as they tend to be the same or similar from room to room.
From there you have to be more targeted based on the clients preferences, specific equipment employed and the particulars of room geometry, furniture placement and so on.

FrankSo, at that point, is there a personal visit? I can provide room geometry, etc. but, short of an actual , shall i say RTA how do we know we have done the best we can do? (poor choice of words, as i feel "best we - - - " etc portends mucho dollars .
The truth is, with 8 chairs, there is only an average [I]best sound(i guess) and so i might be tilting at windwheels in my attempt to go much past where i am now. I JUST DO NOT KNOW!!:confused:
Walt, in uncomfortably cold, rainy, florida.

Frank[/QUOTE]

Weasel9992

01-08-10, 05:35 PM

So, at that point, is there a personal visit? I can provide room geometry, etc. but, short of an actual , shall i say RTA [if that is correct] how do we know we have done the best we can do? (poor choice of words, as i feel "best we - - - " etc portends mucho dollars .
The truth is, with 8 chairs, there is only an average best sound(i guess) and so i might be tilting at windwheels in my attempt to go much past where i am now. I JUST DO NOT KNOW!!

That was a funny edit Walt.

Not usually from us or a company like ours. What you might want to do is call up somebody like Dennis Erskine and have him put together a comprehensive design. It'll cover a ton of bases...best way to go in just about every case if the budget is there. Even if it's not it's worth stretching for. Dennis (or someone like him) will make recommendations that will include a bunch of integrated solutions.

Frank

yacht422

01-08-10, 05:47 PM

That was a funny edit Walt.

Not usually from us or a company like ours. What you might want to do is call up somebody like Dennis Erskine and have him put together a comprehensive design. It'll cover a ton of bases...best way to go in just about every case if the budget is there. Even if it's not it's worth stretching for. Dennis (or someone like him) will make recommendations that will include a bunch of integrated solutions.

Frank
Thx for the recommendation. probably, at this point, the one best thing i can do.
Tonight is our wedding aniv, so i am taking the missus out to dinner,etc.
To all who offered insights, my thanks.
Have a great weekend (we MAY get snow here tomorrow - florida - snow!:cool:)
Walt

Weasel9992

01-08-10, 06:26 PM

Thx for the recommendation. probably, at this point, the one best thing i can do.
Tonight is our wedding aniv, so i am taking the missus out to dinner,etc.
To all who offered insights, my thanks.
Have a great weekend (we MAY get snow here tomorrow - florida - snow!:cool:)
Walt

It's cold as heck here too. No snow though. :D

Frank

kevinzoe

01-08-10, 07:37 PM

It's cold as heck here too. No snow though. :D

Frank

Cold 'ya say . . .?! Why you southern types are a bunch of pansies - It's -20C with the windchill and -40C a couple of provences west of here, not that's cold!

Walt -before you contact Denise Erskine (or anyone else) I'd highly recommend you read Dr Floyd Toole's book, which if nothing else will educate you enough to better communicate with and understand Denise's recommendations.

I can't imagine that ASC's recommendation for just the front wall was going to cost US$10K - seems rather steep to me for a single wall. The front wall is the least important wall in my opinion and your Revel speakers are forward firing to boot so not sure what basis their reco's were based on.

Cheers,
kevin

forestmoonstudio

01-08-10, 08:26 PM

yacht422

01-08-10, 09:05 PM

cannot attach orig quote was $9400 + frt. to manage the front of the room.
walt

yacht422

01-08-10, 09:09 PM

cannot attach orig quote was $9400 + frt. to manage the front of the room.
walt
to clarify: this $$ amount was for the front side walls of the room. i.e two front side walls, not the wall behind the screen.

yacht422

01-08-10, 09:14 PM

Cold 'ya say . . .?! Why you southern types are a bunch of pansies - It's -20C with the windchill and -40C a couple of provences west of here, not that's cold!

Walt -before you contact Denise Erskine (or anyone else) I'd highly recommend you read Dr Floyd Toole's book, which if nothing else will educate you enough to better communicate with and understand Denise's recommendations.

I can't imagine that ASC's recommendation for just the front wall was going to cost US$10K - seems rather steep to me for a single wall. The front wall is the least important wall in my opinion and your Revel speakers are forward firing to boot so not sure what basis their reco's were based on.

Cheers,
kevin
you do need to recognize that in fl we all walk naked!!;)
so - 20 deg f is extreme shrinkage weather.

nathan_h

01-08-10, 11:49 PM

I am still wondering about framed movie posters on acoustic panels. Will the panels not work, because I would have a reflective surface on them?

The panels will not work as well, nor as they were designed.

kevinzoe

01-09-10, 06:29 AM

I am still wondering about framed movie posters on acoustic panels. Will the panels not work, because I would have a reflective surface on them?

***************************
Forestmoonstudio:

If you bought the acoustic panels, then I'd suggest you call the manufacturer (if you haven't already done so) and ask them your question.

Otherwise, if the posters are made from paper then it'll be too thin to adversely affect the panel's performance except for the very highest frequencies; most frequencies will not even 'see' the paper. If it's glass over paper then I'd expect that it'll extend its reflective nature to lower frequencies which may or may not be a good thing. So, will you be able to hear the difference with and without the paper posters over the panels, likely not. As always try both ways and trust your ears.

If it's a bass trap you're using and you want just the low frequencies to be absorbed then by all means put a glass poster in front of it to help reduce the mid/upper frequency abosorption, but if it's mid/upper frequency absorption you seek, then it likely makes sense not to put a glass covered poster in front of the panel.

forestmoonstudio

01-09-10, 07:30 AM

Thank you for the advice guys. My room is only 16'x14' I will have columns on the walls and with that it will not leave alot of room. I know I will need the panels but I will try and put the framed posters on the panels and see how it sounds.

Weasel9992

01-09-10, 09:12 AM

I am still wondering about framed movie posters on acoustic panels. Will the panels not work, because I would have a reflective surface on them?

They'll work, but they'll be much more reflective from the high mid range on up. Won't affect the low end qualities at all. The problem is, in HT set ups the person usually wants to put these kind of panels at the first reflection points, and that won't work. You'd want a more reflective panel away from reflection points...the corners or back wall would be fine.

Frank

captainkidd

01-09-10, 10:07 AM

I have recently built a home theater consisting of a 125" projector screen, Epson 1080P projector, Denon AVR 590 receiver and Klipsch Icon W series 5.1 speaker set up all connected through HDMI.
I am wondering if it will be possible for me to get good surround sound considering my rooms limitations.
The room is actually a converted RV garage. The entire garage WAS 70' deep by 20' wide by 16' high. It is built entirely out of concrete block with a VCT tile floor and sheetrock ceiling. The two end walls are huge roll up garage doors.
I walled off the last 30' of it by building a sheetrock wall with a set of double doors going into the 'new' garage. This 30' X 20' x 16' H rectangular room is the new man cave. It has a pool table, dart board, vending machine and now theater in it.

I will try to describe the room as best I can. The theater uses up about 12' of the rectangle starting along the new sheetrock wall. The screen is mounted on one concrete wall and the seating area is backed up near the opposite wall about 16'-18' away. So, the right hand speakers are in corners while the left hand speakers are near the front and rear walls but there is no left hand wall, just open space going over to the pool table ect.

When we attempted to watch our first movie the dialogue was very difficult to understand due to the poor room acoustics. I added a medium sized throw rug over the tile in front of the screen and built (6) 2' X 4' acoustic panels out of 2" thick owens corning 703, framed in pine, covered with a light cloth and stood off the walls about 2". I hung these starting at the first reflection point on the right hand wall and centered at ear height and basically continued them, evenly spaced every 10" along the side wall and along the rear wall, ending just past the seating are.
These changes helped quite a bit but certain parts of movie dialog still seem to disappear. I get the feeling that there is just too much reverb at certain tones and sometimes the bass seems to drown out everything.

So I am wondering if it is even possible to get good sound in a room like this or if I am just going to be stuck with mediocre sound due to the off balance design of the room? Any advice would be greatly appreciated.

zmisst

01-09-10, 10:38 AM

Walt, there are those that are saying early lateral reflections are good. Ceiling, floor and rear wall are still treated. You're right about conventional wisdom, and I really have a hard time abandoning my thinking that the room should be neutralized as much as possible and the speakers should re-create the environment the artist created. New tech from companies like Audyssey and Dolby are aimed at expanding the front soundstage.

Jeff

After taking a sabatical for a while glad to see that the "absorb-all-first-reflection" dogma continues to be under assault. Probably as a result of people reading Toole's book; and finding the occasional nugget of heresy from Dennis and even Terry now I see.

I looked into this issue quite a bit and concluded the following, based on primarily on Toole's book and evidence cited therein, and considering and contrasting all the conflicting advice given on this thread and in this forum:

In order of priority:
* add sound absorbing material (at least 3-4" thick) to front wall.
* add sound absorbing material or diffusers to center portion of rear wall
* consider diffusing/scattering surfaces on walls opposite surround speakers to enhance envelopment and help avoid flutter echoes.

If you think your side wall absorption makes the room sound better, try moving the side absorbers to the front or rear walls instead. (Don't just take them out of the room completely). By testing the absorbers in different locations in the room you will get the same effect on total room reverb, but will not interfere with the lateral reflections and will stead absorb more of the front and rear reflections which are of much more benefit (especially front).

While I was also drawn to the idea (and the cool applet that plotted the reflection points) I have seen nothing to show that there is a benefit to absorbing side wall first reflection points and there is persuasive evidence that absorption on the side walls is harmful since in blind tests people actually prefer side wall reflections: especially for speech intelligibility. 90% of most movie audio is dialogue, the dialogue is what we most concentrate on and lower speech intelligibility is very annoying.

Put your absorption on the front and rear and don't worry about the sides. If you still doubt, read Toole's book.

yacht422

01-09-10, 01:18 PM

After taking a sabatical for a while glad to see that the "absorb-all-first-reflection" dogma continues to be under assault. Probably as a result of people reading Toole's book; and finding the occasional nugget of heresy from Dennis and even Terry now I see.

I looked into this issue quite a bit and concluded the following, based on primarily on Toole's book and evidence cited therein, and considering and contrasting all the conflicting advice given on this thread and in this forum:

In order of priority:
* add sound absorbing material (at least 3-4" thick) to front wall.
* add sound absorbing material or diffusers to center portion of rear wall
* consider diffusing/scattering surfaces on walls opposite surround speakers to enhance envelopment and help avoid flutter echoes.

If you think your side wall absorption makes the room sound better, try moving the side absorbers to the front or rear walls instead. (Don't just take them out of the room completely). By testing the absorbers in different locations in the room you will get the same effect on total room reverb, but will not interfere with the lateral reflections and will stead absorb more of the front and rear reflections which are of much more benefit (especially front).

While I was also drawn to the idea (and the cool applet that plotted the reflection points) I have seen nothing to show that there is a benefit to absorbing side wall first reflection points and there is persuasive evidence that absorption on the side walls is harmful since in blind tests people actually prefer side wall reflections: especially for speech intelligibility. 90% of most movie audio is dialogue, the dialogue is what we most concentrate on and lower speech intelligibility is very annoying.

Put your absorption on the front and rear and don't worry about the sides. If you still doubt, read Toole's book.
i just ordered it. Amazon promises Toole's book next tues. :)
That said, what about the ceiling? I can move the side absorbers to the ceiling, which, again, most posters seem to recommend.:confused:
I REALLY hate the thought that all the 2008 advice i've read/received was in error, and most of my room treatments are,basically,incorrect.:mad:
walt
but, again, my appreciation for the insights gained here!
(for the benefit on our Canadian friends out on the tundra in snuggies and mukluks, we in florida, the land of orange juice and bikini's, had snow this am.):D:D:D:D

whumpf

01-09-10, 01:58 PM

(for the benefit on our Canadian friends out on the tundra in snuggies and mukluks, we in florida, the land of orange juice and bikini's, had snow this am.):D:D:D:D

What part of Florida? We have cold here, but not cold enough to snow (supposed to be 34 tonight).

kevinzoe

01-09-10, 02:33 PM

i just ordered it. Amazon promises Toole's book next tues. :)
That said, what about the ceiling? I can move the side absorbers to the ceiling, which, again, most posters seem to recommend.:confused:
I REALLY hate the thought that all the 2008 advice i've read/received was in error, and most of my room treatments are,basically,incorrect.:mad:
walt
but, again, my appreciation for the insights gained here!
(for the benefit on our Canadian friends out on the tundra in snuggies and mukluks, we in florida, the land of orange juice and bikini's, had snow this am.):D:D:D:D

*********************
Yikes, snow in the oranges and bikini belt?! So much for global 'warming.'

Walt, glad to hear that you've order THE book. I'll be sending you a PM regarding Chapter 22 that you'll find of interest.

I was thinking about your bass traps and lack of space and having to swap out SVS box subs for their cylinder cousins to safe floor space . . . Are you familiar with membrane/diaphragmatic bass traps that work differently than fibreglass-filled traps? The former work where the air PRESSURE is maximized (which is at the impact of the wall) and the latter work where the air particle MOTION is maximized which is one-quarter of the wavelength out from the wall. So, I would suggest you look at RPG's website, for example, for the diaphragmatic bass traps that hang on the wall and take up maybe 4"-6" vs the much thicker fibreglass filled resistive-type traps when floor space is scarce.

By the way, mukluks are back in style don't you know! :D

Bass Slut

01-09-10, 04:42 PM

captainkidd
i'm @ 4 post so y not
run you exact room dimensions through a room mode calculator
there are many, but you need to understand what freqs are overlapping
1130 ft per sec speed of sound /20' wide room / two trips = 28.25hz

30' long may not need treatment = 18.83hz & 37.6hz problems
20' = definate problems @ 28.25, but especially @ 56.5hz
16' will ring @ 35.3hz & 70.6hz bad
without running it through a mode overlap calculator, cause you didn't input inches, it looks like 3 homemade helmholtz resonantors place near the listening position would fix it all

i'd just make them 2.0cubic feet each, like a cheap speaker box, & tune each one to 56.5hz, 35.3hz & 70.6hz
i'd use 2.7" hole, no port on the 70hz, a 4" dia port on the 56hz & 3" id port on the 35hz
if your math is all right, you can tune the ports to the mm by ear yourself
i padded each helmholtz eff/ring time/bandwith by throwing in small rags, into the resonator 1 @ a time

the freqs octave up into the voice range & overlap...ooh

nothing else will work

yacht422

01-09-10, 06:36 PM

kevin: your pm was blocked - did not receive it - (i am a mac guy -that may be the reason.)
In advance, however, I thank you and will pay particular attention to #22.
Regarding the sub comments: Not me! I am not certain who you wanted to post your recommendation to, but, I do not have a space limitation.(16 X 23 X 10)
walt

yacht422

01-09-10, 06:40 PM

Kevin: I have the pm. Thanks mucho!!
Walt

Bass Slut

01-11-10, 08:06 AM

glaufman

01-11-10, 09:50 AM

well i assume somebody has read all 190 pgs here & more

so my question is, is there a DIY thread on making helmholtz boxes to cancel root freq modes somewhere b4 i attempt to help people by making one w pics ??

i have searched
just trying to help

thx

Joe:)

I'll admit I haven't searched, but I also haven't seen one, and I would love ot see one. Especially is it goes into designing one for certain freqs, BW, etc...

pepar

01-11-10, 11:21 AM

What part of Florida? We have cold here, but not cold enough to snow (supposed to be 34 tonight).
It was 65 and raining in Cancun two nights ago. Had to wear a long sleeve shirt. Brrr. :D

Kal Rubinson

01-11-10, 12:28 PM

I'll admit I haven't searched, but I also haven't seen one, and I would love ot see one. Especially is it goes into designing one for certain freqs, BW, etc...
Links here:
http://www.mhsoft.nl/Helmholtzabsorber.asp#HelmholtzPanelAbsorber
http://forum.studiotips.com/index.php?sid=40e271899a3649a9564d625053ee43f6

johnbomb

01-12-10, 11:53 AM

Thanks, Kal, but the first link doesn't work.

Kal Rubinson

01-12-10, 11:58 AM

Thanks, Kal, but the first link doesn't work.
I know but I was hoping it was just my computer that was at fault.

CruelInventions

01-12-10, 12:47 PM

Quotes edited and bolded for clarity:

......
I looked into this issue quite a bit and concluded the following, based on primarily on Toole's book and evidence cited therein, and considering and contrasting all the conflicting advice given on this thread and in this forum:

In order of priority:
* add sound absorbing material (at least 3-4" thick) to front wall.
* add sound absorbing material or diffusers to center portion of rear wall
* consider diffusing/scattering surfaces on walls opposite surround speakers to enhance envelopment and help avoid flutter echoes.

If you think your side wall absorption makes the room sound better, try moving the side absorbers to the front or rear walls instead. (Don't just take them out of the room completely). By testing the absorbers in different locations in the room you will get the same effect on total room reverb, but will not interfere with the lateral reflections and will stead absorb more of the front and rear reflections which are of much more benefit (especially front).

..........

Put your absorption on the front and rear and don't worry about the sides. If you still doubt, read Toole's book.

.........

Walt -before you contact Denise Erskine (or anyone else) I'd highly recommend you read Dr Floyd Toole's book, which if nothing else will educate you enough to better communicate with and understand Denise's recommendations.

I can't imagine that ASC's recommendation for just the front wall was going to cost US$10K - seems rather steep to me for a single wall. The front wall is the least important wall in my opinion and your Revel speakers are forward firing to boot so not sure what basis their reco's were based on.

Cheers,
kevin

Seeming descrepancy here regarding the front wall treatment recommendation; one person says it's important, the other, not so much. Both naming Toole's work/advice as a primary source of expertise.

Have one of you misinterpreted Toole's work? Or is there some subtle nuance I am missing in which both of you may be correct?

My previous but somewhat vague impression has been that front wall treatment is recommended for 5.1 or more multi-channel rooms, but not so important for a strictly 2 channel type music room. Of course, corner-type bass treatments being a different discussion.

Thanks in advance.

mike2060

01-12-10, 02:32 PM

Covering the whole front wall is good for HT because the surrounds don't get reflected and for SBIR.

For 2 channel as long as your speakers are far enough from the walls usually diffusion is used I believe. If you speakers are close to the walls you need some absorption behind them for SBIR.

Weasel9992

01-12-10, 03:11 PM

Covering the whole front wall is good for HT because the surrounds don't get reflected and for SBIR.

There's some debate on this point, but I would agree.

For 2 channel as long as your speakers are far enough from the walls usually diffusion is used I believe. If you speakers are close to the walls you need some absorption behind them for SBIR.

This is really room and speaker-dependent. Sometimes diffusion on the front wall is appropriate, but lots of times it's not.

Frank

Ethan Winer

01-12-10, 04:33 PM

Thanks, Kal, but the first link doesn't work.

That site seems to be gone, for now anyway. I have the calculator (Windows only), and I'm glad to email it to anyone who wants it. Reach me through my home page:

www.ethanwiner.com

--Ethan

yacht422

01-12-10, 06:36 PM

There's some debate on this point, but I would agree.

This is really room and speaker-dependent. Sometimes diffusion on the front wall is appropriate, but lots of times it's not.

Frank
what/how does one treat the front wall when it is mostly screen?
although my room is 16+' wide, there are no front corners, as such.
the front of the room has a four foot mini wall at 45deg from the flat walls.
(ref pic : easier than explaining)
walt

Ethan Winer

01-13-10, 09:01 AM

what/how does one treat the front wall when it is mostly screen?

Wall-floor and wall-ceiling corners are good, and flat on the wall behind the screen can help too if you have at least 3 or 4 inches or more space.

the front of the room has a four foot mini wall at 45deg from the flat walls.

Why are those corners walled off? Can you remove that?

--Ethan

kevinzoe

01-13-10, 01:36 PM

Quotes edited and bolded for clarity:

Seeming descrepancy here regarding the front wall treatment recommendation; one person says it's important, the other, not so much. Both naming Toole's work/advice as a primary source of expertise.

Have one of you misinterpreted Toole's work? Or is there some subtle nuance I am missing in which both of you may be correct?

My previous but somewhat vague impression has been that front wall treatment is recommended for 5.1 or more multi-channel rooms, but not so important for a strictly 2 channel type music room. Of course, corner-type bass treatments being a different discussion.

Thanks in advance.
*******************************
CruelInventions - sorry for the confusion. I expect it's my fault. My statement that the front wall is likely the least important wall to treat was in the context of 2-ch stereo not HT and that the 2-Ch stereo speakers are forward firing. Reason being is that a number of factors combine to make the sound from the front wall much less audible than say 1st reflection points off side walls, ceiling, and floor. From Toole's book, these factors include:
* sound energy propogation loss or decline in steady-state sound level as a function of distance through air at about -3dB per double distance
* reduced sound energy upon impact with surfaces that are absorbing or diffusing before traveling to the front wall
* precedence effect caused our attention to focus on the first arrival/direct sound and we simply are not aware of the reflections as spatially seperate events, or much less so.

For HT, Toole recommends 3-4" minimum thickness of absorption in the centre portions of the front and back walls.

Hope this helps . . .

Electric_Haggis

01-13-10, 03:00 PM

what/how does one treat the front wall when it is mostly screen?
although my room is 16+' wide, there are no front corners, as such.
the front of the room has a four foot mini wall at 45deg from the flat walls.
(ref pic : easier than explaining)
walt

For what it's worth, I use the inch or so behind my screen & curtains to store the packing foam & cardboard for my speakers. There's also a thin layer of acoustic polyroll material.

Apart from helping to reduce a little transmission to the next apartment, it makes a noticeable difference to the liveness and bass boom of the room.

You can see this below...

erkq

01-13-10, 03:20 PM

what/how does one treat the front wall when it is mostly screen?

I know. That big flat reflective surface can be a problem. This is one of the overlooked advantage of an AT screen.

yacht422

01-13-10, 03:47 PM

Wall-floor and wall-ceiling corners are good, and flat on the wall behind the screen can help too if you have at least 3 or 4 inches or more space.

Why are those corners walled off? Can you remove that?

--Ethan
no- it has to do with the overall design of the space - there is a full bathroom to the right of the h/t, and we needed space to enter the shower:ergo. angled wall.
the opposite wall holds a small closet, and was built as an "aesthetic".(balanced the room visually.)

yacht422

01-13-10, 03:52 PM

ethan, the screen is mounted directly on the wall. i'd need to make standoffs to move it out. are there sound reasons to do so?
then the next question is 4" of what, and wall to wall, i presume.
walt

LotToLearn

01-14-10, 10:57 AM

I searched everywhere but can find the answer - is Owens Corning 703 a fire retardant material? I am planning to build panels for my room using these panels covered with GOM FR701 but want to make sure the panels themselves will not be a fire hazard.

Weasel9992

01-14-10, 11:40 AM

Ethan Winer

01-14-10, 02:34 PM

are there sound reasons to do so?

Yes, all rooms need plenty of bass trapping.

then the next question is 4" of what, and wall to wall, i presume.

4 inches of rigid fiberglass. Even more at the bottom if possible, straddling the wall-floor corner fully from left to right.

--Ethan

yacht422

01-14-10, 10:05 PM

ethan: many thanks!
walt

pocoloco

01-15-10, 02:43 PM

pepar

01-16-10, 09:48 AM

Some food for thought....

I've been reading Sound Reproduction by Floyd Toole and it says that bass traps using resistive absorption (ie: rigid fiberglass) placed at wall boundaries/corners are ineffective because those are high pressure regions. For fiberglass to be effective, it needs to be placed in high VELOCITY regions which work out to be away from wall boundaries. And placing fiberglass away from wall boundaries is not very practical.

So basically the common rule here to pack corners full of fiberglass to work as bass traps goes out the window. He actually goes as far to say that acoustic companies that produce fiberglass products that fit into corners and marketed as "bass traps" is ineffective and is more "wishful thinking". If you want bass traps at the corners, membrane absorbers or resonators are the way to go.
well, those who are packing their corners are not just sticking a little there. many use the 17" face chunk design, and some have the luxury (of space) to use the 24" face. my understanding of why to trap the corner is that ALL modes are present there.

wishful thinking? :rolleyes: yeah, maybe that's what cleaned up the overhang in my room that used to be present in the waterfalls.

mike2060

01-16-10, 10:19 AM

Some food for thought....

I've been reading Sound Reproduction by Floyd Toole and it says that bass traps using resistive absorption (ie: rigid fiberglass) placed at wall boundaries/corners are ineffective because those are high pressure regions. For fiberglass to be effective, it needs to be placed in high VELOCITY regions which work out to be away from wall boundaries. And placing fiberglass away from wall boundaries is not very practical.

So basically the common rule here to pack corners full of fiberglass to work as bass traps goes out the window. He actually goes as far to say that acoustic companies that produce fiberglass products that fit into corners and marketed as "bass traps" is ineffective and is more "wishful thinking". If you want bass traps at the corners, membrane absorbers or resonators are the way to go.

He may be talking about removing the room modes rather than just decreasing decay time.

Ethan Winer

01-16-10, 12:40 PM

So basically the common rule here to pack corners full of fiberglass to work as bass traps goes out the window.

Not in this universe. My company's video Hearing is Believing (http://www.realtraps.com/video_hearing.htm) shows a huge before/after change with a lot of bass traps, and in this case the traps aren't even straddling corners. Floyd is correct in theory, but in practice you don't have to put panels several feet out from the wall to make a huge improvement. The video above shows a very large improvement in the response and ringing to 40 Hz and below.

He actually goes as far to say that acoustic companies that produce fiberglass products that fit into corners and marketed as "bass traps" is ineffective and is more "wishful thinking". If you want bass traps at the corners, membrane absorbers or resonators are the way to go.

Again, he is wrong - and easily proven wrong - in the above video as well as in many other articles, videos, and graphs all over my company's web site.

--Ethan

Ethan Winer

01-16-10, 12:41 PM

many use the 17" face chunk design, and some have the luxury (of space) to use the 24' face.

34 inches rules! :D

yacht422

01-16-10, 03:11 PM

34 inches rules! :D

is this 34" deep, or, 34" across the front of the corner(i.e. the hypotenuse)
i currently am 17" deep X 34" front X eight feet, floot to ceiling, GOM faced.
walt

yacht422

01-16-10, 05:14 PM

Yes, all rooms need plenty of bass trapping.

4 inches of rigid fiberglass. Even more at the bottom if possible, straddling the wall-floor corner fully from left to right.

--Ethan when you say 'more', how much? and, related, is this a product your company mfgs?
you may pm me if you choose not to respond in this thread.
thx
walt

yacht422

01-16-10, 05:16 PM

new question.
we all cover the f/g with GOM. is there any knowledge/statistics about covering the rigid f/g with plastic screening? (as in 'screen door' screening.)
walt

gremmy

01-17-10, 01:21 AM

Not in this universe. My company's video Hearing is Believing (http://www.realtraps.com/video_hearing.htm) shows a huge before/after change with a lot of bass traps, and in this case the traps aren't even straddling corners. Floyd is correct in theory, but in practice you don't have to put panels several feet out from the wall to make a huge improvement. The video above shows a very large improvement in the response and ringing to 40 Hz and below.

Again, he is wrong - and easily proven wrong - in the above video as well as in many other articles, videos, and graphs all over my company's web site.

--Ethan

And to second what you're saying, Ethan, all anyone has to do to actually "see" the difference that can be obtained with corner mounted bass traps is to download REW and measure the in-room response before and after. This is important for people to do anyway, since everyone's room is different and very few match the models exactly. If you put your absorption in the right place (and in the right amounts), the difference, both measured and audible, is *not* subtle.

Spaceman

01-17-10, 12:58 PM

http://i847.photobucket.com/albums/ab35/spacemanlee--/ScreenWall3.jpg

In this scenario, do I need corner bass traps beside the screen wall in the main room AND behind the screen, where I currently show the 2" of 703? The cross-hatched patterns indicate the bass traps and the 2" of 703 up against the wall.

I'm hoping to put the sub, mains and ctr behind an AT screen. One concern I have is with imaging. If the mains go behind the screen, they will only be 6' apart at the most. Front row viewing will be from 9 1/2'. Will the mains be too close together? Moving them to the sides gets problematic because they would need to sit in front of the duct, but I don't want to move the screen any further into the room. I'm hoping behind the screen is ok.

Ethan Winer

01-17-10, 01:30 PM

is this 34" deep, or, 34" across the front of the corner(i.e. the hypotenuse)

That was half meant as a joke, because my company recently started offering a filled corner trap that's 34 inches wide across the front face.

--Ethan

Ethan Winer

01-17-10, 01:31 PM

all anyone has to do to actually "see" the difference that can be obtained with corner mounted bass traps is to download REW and measure the in-room response before and after. This is important for people to do anyway

Yes and Yes.

Ethan Winer

01-17-10, 01:33 PM

In this scenario, do I need corner bass traps beside the screen wall in the main room AND behind the screen wall in the recessed cavity?

IMO, in every scenario you want as much bass trapping as possible.

--Ethan

yacht422

01-17-10, 05:00 PM

so, my present arrangement is ok, i presume.
( i also have two 2'X4'X4" 701 panels on the rear wall, each on either side of a double wide window that i have "faced" with a 4" X 4' X 6' panel.)
you had mentioned bass trapping at the front wall, floor to wall, 4" min. thick.
Do you offer this , and is 6" better than 4"?(or, is this another diy project that will yield acceptable results)
(i am running two subs, and a pair of full range spkrs, front firing, ported 360 deg. at the bottom. (REVEL Ultima Salons)
walt

yacht422

01-17-10, 05:09 PM

tccolv

01-18-10, 12:18 PM

My head is spinning and my theater is a-waiting....
http://www.avsforum.com/avs-vb/images/smilies/eek.gif
I was all set to completely cover my front wall (18' x 9') with 2" DIY Rockwool panels. I changed course based on some threads saying that 2" was too much absorption, so instead, in each corner, I hung 2' x 8' 4" thick panels and bought enough 1" 703 to do the center 14'. The 703 will be framed on 1/4" 4x8 luan sheets.

Now I read (at about post 175) that 3"-4" is the cats meow for the front wall. Too late! Panels built. So I'm wondering if my luan backed 1" panels were hung on furring strips giving me 2" gap from the wall, would the 703 faced luan act as a diaphamic basstrap, if so, how much, or would it even be worth bothering with?

Any feedback?

Weasel9992

01-18-10, 06:06 PM

Now I read (at about post 175) that 3"-4" is the cats meow for the front wall. Too late! Panels built. So I'm wondering if my luan backed 1" panels were hung on furring strips giving me 2" gap from the wall, would the 703 faced luan act as a diaphamic basstrap, if so, how much, or would it even be worth bothering with?

Any feedback?

Well...at some frequency it probably does. There's no way to know unless you test it. 1" 703 is fine for the front wall though...3"-4" is great if the room is small and you need more low frequency absorption, but I think you'll be alright the way you are. How does it sound? Have you had a chance to give the room a test run?

Frank

jlupo

01-19-10, 03:44 PM

the equal lateral triangle is always best for stereo imaging. Optimum timbre and imaging is obtained when you point (toe-in) the speakers towards the listening position. Also pulling them away from the wall will open up the sound, increase spaciousness and improve imaging. I have mine 4' off the screen wall with a 15 degree toe-in angle. Just open them up the best you can.

dweltman

01-19-10, 07:26 PM

I am thinking about putting some of the panels with art prints in my room. They would go behind my listening position. The listening seats are pretty close to the rear wall, about 2-3 feet. The ASC panels claim to have diffusion strips, which they say are ideal for this sort of location. Something about the sound being too "dead" if you are too close to a panel that is straight absorbing. Would this really be advantageous as compared to other panels?

Weasel9992

01-20-10, 06:24 PM

jcieutat

01-20-10, 09:27 PM

OK, since good advice is being dished out here I thought I would jump in. I am new to the home theater world. We are in the construction phase of our addition that will be a home theater. The room is basically 18' x 14' with a 9' ceiling. In the room there is also a 2' x 6' insert for the computer area. So the room is not perfectly rectangular. It would have been 18' x 16' but it is behind our living room fireplace so it goes into this room which is an addition. We are going with spray foam insulation for energy efficiency. The walls and ceiling will be sheetrock and the flooring will be engineered hardwood. My audio will be KEF HTS5005.2 with a set of Proficeint Audio in ceiling speakers for the rear channels. I am told I need to add some acoustical panels into the room. I am kind of confused about the placement. I was going to build columns to house them because I want the room to have a clean look and not have panels hanging on the walls everywhere. Do these things need to be directly across from the speakers? Any advise would be greatly appreciated. Tomorrow I will scan in the floor plan and post it here.

humyt

01-21-10, 03:21 AM

Ethan Winer

01-21-10, 03:10 PM

^^^ Yes, symmetry is important. But the side walls toward the back of the room are not the first place I'd put diffusors. The rear wall makes more sense.

--Ethan

dweltman

01-21-10, 03:55 PM

Ethan:
so then the conclusion is that the rear wall is a good place for diffusion, but diffusors lose efficacy if your listening position is too close to the rear wall?

kevinzoe

01-21-10, 10:01 PM

I'm planning to install some diffusors on the rear side walls of the room, just wondering if the layout of the diffusors needs to be symmetrical on both side walls?

Can I install say 3 pieces of 2' x 2' diffusors on the left side wall and 1 piece on the right side wall? This is due to an existing cabinet obstructing some parts of the rear right side wall.

*****************
Humyt - diffusion on the rear side walls does not need to be symetrical. I have a GIK D1 diffusor on the rear left side wall and a Skyline diffuser across from it on the right side wall and when one is removed there is very little sonic affect because just one is sufficient to attenuate flutter echo between the rear side walls. So, of course you should experiment but I would predict that having 2-3 on one rear side wall and only 1 on the opposite won't hurt things at all. Dr. Floyd Toole in his latest book shows various HT acoustical setups and there are examples of differing diffusion treatments across from each other (e.g. hemicylindrical, QRD diffusers.)

I agree with Ethan that diffusion on the back wall is where I put my first diffusers before the rear side walls. What kind of diffuser are you thinking of using because it's thickness (aka deepest well or cell depth) should be a minimum of 8" and work down to 300Hz and then use bass traps for <300Hz. One idea is to put a bass trap in the middle of the back wall with diffusers on either side of it, OR build a very deep diffuser and put bass traps beneath it for the floor/wall corner and back wall corners from floor-to-ceiling.

Clear as mud?

humyt

01-21-10, 11:13 PM

Thanks for the advice Ethan and Kevinzoe. I am thinking of trying out the Aurelex T-Fusor which is also 6" thick as the GIK D1 diffusor. The planned locations for them are:

a) 1 panel at each corner of the rear wall at ear height

b) 4 panels at first reflection point on the ceiling

c) 1 panel to each side wall of the main listening position at ear height

Front and rear walls (middle part) will use absorption as per Dr.Toole's book Chp. 22.

1 bass trap at each wall/ceiling corners (Auralex LENRD).

Does this sound right? My usage will be mainly for movies (7.2 channels + DSX wides setup). Room size is 4.3m(W) x 6.5m (L) x 2.5m (H).

kevinzoe

01-22-10, 11:07 AM

Humyt - If you're buying Auralex then don't expect Ethan to respond as he reqpresents a 'competitor' to Auralex.

6" deep diffusers - GIK D1 or Auralex T-Fusor - aren't really deep enough to diffuse really effectively down to +-300Hz which represents your estimated room's Schroeder frequency or transition frequency. Have you considered building a Skyline or hemicyclindrical diffuser which can be customized to your needs and offers greater depth flexibility? Just a thought . . .

Regarding your point "a) 1 panel at each corner of the rear wall at ear height" I think bass traps should go there not diffusion.

Regarding your point "c) 1 panel to each side wall of the main listening position at ear height" I don't think you need anything on the side walls directly beside the listening chair as reflections hitting this spot will bounce ahead or behind you so aren't an issue. Instead try experimenting with the diffusers on the side wall's 1st reflection points which is slightly ahead of the listening position but not quite to the speakers.

Have you read Toole's book as you mentioned chapter 22 . . .? If so, lots of 'sound' advice in it for you.

Thanks for the advice Ethan and Kevinzoe. I am thinking of trying out the Aurelex T-Fusor which is also 6" thick as the GIK D1 diffusor. The planned locations for them are:

a) 1 panel at each corner of the rear wall at ear height

b) 4 panels at first reflection point on the ceiling

c) 1 panel to each side wall of the main listening position at ear height

Front and rear walls (middle part) will use absorption as per Dr.Toole's book Chp. 22.

1 bass trap at each wall/ceiling corners (Auralex LENRD).

Does this sound right? My usage will be mainly for movies (7.2 channels + DSX wides setup). Room size is 4.3m(W) x 6.5m (L) x 2.5m (H).

Lightspeed66

01-22-10, 01:22 PM

Room treatment is one area I hadn't even considered, and don't know if I would have even missed it if it wasn't there. That said, I'm picky about the sound and have $$ invested.

If I had $100 and DIY, where would be the first place to put something to have the biggest effect? i may add more later, but for now I've got to keep it small.
ATS has some Roxul Rockboard 60 I could use in 2x4 panels.

My room is 8 foot ceiling, maybe 18-20 deep and 12 wide? Curtains along one side wall, back of room has desk and computer setup in one corner and stairs in the other. Viewing/seating is about midway into the room, center.

I could fit:

-1 to 3 panels along side wall on right.
-several panels on the wall behind the mains and tv (50").
-MAYBE something on back wall center, although WAF would crumble.
-corners behind mains and tv, maybe.

$$ wise $100 would get me about 4 panels of that size with cloth and hardware. Where should I focus energy? Will it even do anything?

Ethan Winer

01-22-10, 02:09 PM

So then the conclusion is that the rear wall is a good place for diffusion, but diffusors lose efficacy if your listening position is too close to the rear wall?

Not exactly. In fact, diffusion probably is less necessary if you're very far from the rear wall because the distance alone will spread the sound. Plus, reflections from a distant surface are weaker and so less damaging. My main point is that the side walls are out of the way of the "line of fire" so to speak, so that's a less important location.

--Ethan

Ethan Winer

01-22-10, 02:11 PM

I am thinking of trying out the Aurelex T-Fusor which is also 6" thick as the GIK D1 diffusor.

GIK's diffusor is a genuine QRD type. The T-Fusor is not nearly as good IMO.

--Ethan

bpape

01-22-10, 03:01 PM

Just as a follow-up, the D1 has a higher cutoff on the top end as some of the well faces are polys to extend it to over double what a standard well face would do.

I would also agree with Ethan with regard to the side wall placement vs behind the seating. Another location that's 'out of the line of fire' is up high on the walls where you're primarily looking to minimize slap echo.

Bryan

Lightspeed66

01-22-10, 04:31 PM

OK read much more. Thanks for the articles Ethan.

I'm going to try one panel on the right wall at a reflection point, and bass traps in the corners behind the mains and tv. Would additional panels behind each main speaker be useful?

Not sure on materials and design of the bass traps themselves, but it will be all DIY. Also, not sure if upper and lower corners or floor to ceiling? Would just one 2x4 panel be effective? BTW, the sub is located in the corner to the left of the mains if that matters.

yacht422

01-22-10, 06:23 PM

kevinzoe

01-22-10, 06:49 PM

does rockwool (slab form) offer as good or better performance than oc 703 for floor to wall trapping?
i am considering 6" wlde X 16" hi X 10 feet long.( front wall under screen.)
walt
(this is in response to an earlier comment by ethan - bass trap the front under the screen)

Walt - check out this link for absorption coefficients between various products, including OC and Rockwool and Roxl:
http://www.bobgolds.com/AbsorptionCoefficients.htm

By the way, how goes the reading of 'the book?' :) Your impressions?

If one is to build bass traps and have an air space behind the trap, then why are people using OC 703 when 701 has a higher 125Hz absorption coefficient??? I contrasted OC 701 3" thickness (using the 16" air space specs on the link above) with OC 703 3" and 4" thickness and in both cases the 701 less dense material had better low freq absorption. So why do people seem disposed to get 703 instead?

At 1KHz the trend is reversed with OC 703 being more absorbent than 701, but for bass traps I don't want 1KHz absorbed, I want it either reflected or diffused.

Elill

01-22-10, 06:56 PM

Anyone know what the minimum recommended seating distance is from a BAD panel?

Also if anyone can tell me the diameter of the holes that would be useful.

humyt

01-23-10, 07:14 AM

Regarding your point "a) 1 panel at each corner of the rear wall at ear height" I think bass traps should go there not diffusion.

Regarding your point "c) 1 panel to each side wall of the main listening position at ear height" I don't think you need anything on the side walls directly beside the listening chair as reflections hitting this spot will bounce ahead or behind you so aren't an issue. Instead try experimenting with the diffusers on the side wall's 1st reflection points which is slightly ahead of the listening position but not quite to the speakers.

Have you read Toole's book as you mentioned chapter 22 . . .? If so, lots of 'sound' advice in it for you.

Really appreciate your advice kevinzoe. Perhaps I didn't phrase it correctly, what I meant to say was placing 1 panel each towards the side of the rear wall. I do intend to place bass traps at the corners.

As for the diffusors at the side walls, I was thinking of following what was suggested in Figure 22.3 (page 506) of Dr. Toole's book, specifically Wall B, where a long array of engineered diffusors lined quite a fair bit of the side wall. Is this a good practice for multi-channel setup?

humyt

01-23-10, 07:16 AM

yacht422

01-23-10, 02:59 PM

Walt - check out this link for absorption coefficients between various products, including OC and Rockwool and Roxl:
http://www.bobgolds.com/AbsorptionCoefficients.htm

By the way, how goes the reading of 'the book?' :) Your impressions?

If one is to build bass traps and have an air space behind the trap, then why are people using OC 703 when 701 has a higher 125Hz absorption coefficient??? I contrasted OC 701 3" thickness (using the 16" air space specs on the link above) with OC 703 3" and 4" thickness and in both cases the 701 less dense material had better low freq absorption. So why do people seem disposed to get 703 instead?

At 1KHz the trend is reversed with OC 703 being more absorbent than 701, but for bass traps I don't want 1KHz absorbed, I want it either reflected or diffused.kevin: re: book. pg 86; it's like the bible - cannot read it once and understand it all.

kamich70

01-23-10, 11:33 PM

soooo... after reading all of this... what would someone on here charge me to tell me what to put where if I can give room dimensions, etc??

nathan_h

01-24-10, 12:30 AM

It's likely, though you mention "soundproofing" whereas most of this discussion is not about keeping sound in the room (ie soundproofing), but, rather, about making the room itself better for the sound inside of it (ie acoustic treatment).

Weasel9992

01-25-10, 11:26 AM

soooo... after reading all of this... what would someone on here charge me to tell me what to put where if I can give room dimensions, etc??

It depends on what you actually need. If it's simple acoustic treatment, then the vendors here won't charge you anything. If it's room design, then there are several highly qualified professionals who post here all the time. I'm not privvy to their rates, but you could simply PM them.

Frank

pepar

01-25-10, 11:44 AM

soooo... after reading all of this... what would someone on here charge me to tell me what to put where if I can give room dimensions, etc??
As you probably "got" from Frank's post, there is more to it than "here are my dims, what do I put where?" It *might* be that simple, but then it might not and you do more harm than good.

If you are taking the DIY route to sound treatments, you will need a (free) app like Room EQ Wizard and a (not free) calibrated mic.

Jeff

jjmbxkb

01-25-10, 06:21 PM

Weasel9992

01-25-10, 06:25 PM

Hi, in the process of treating my room, and got the following questions:

1. What is the performance difference between a foam corner bass trap and a 4" OC703 panel mounted at the corner?

2. Particularly, has anybody had any experience with this? http://www.prosoundfoam.com/12_in_Pro_Sound_Foam_Bass_Trap-details.aspx

Thanks very much for any information.

I'm really not being a bit flippant when I say the difference is, 4" of OC703 straddling a corner actually works and foam does not. It simply is not a good source for bass trapping. You really only have to view the lab test data to see the very clear distinction. Even if you were to use foam, by the time you'd used enough to equal the effectiveness of a panel trap you'd have spent much more than you would have on even a commercially purchased panel.

Frank

jjmbxkb

01-25-10, 06:29 PM

I'm really not being a bit flippant when I say the difference is, 4" of OC703 straddling a corner actually works and foam does not. It simply is not a good source for bass trapping. You really only have to view the lab test data to see the very clear distinction. Even if you were to use foam, by the time you'd used enough to equal the effectiveness of a panel trap you'd have spent much more than you would have on even a commercially purchased panel.

Frank

Frank, thanks very much for the quick response. That makes it pretty simple, I will use panels then.

Kal Rubinson

01-25-10, 07:28 PM

maxfli

01-26-10, 01:12 AM

Someone had posted previously about placing a movie poster over a 2' x 4' acoustic panel and if I recall other than as a bass trap, this was Ok. How about something like this?

http://cgi.ebay.com/WISCONSIN-BADGERS-HOCKEY-DYNASTY-BANNER_W0QQitemZ140376203300QQcmdZViewItemQQptZUS_SM_Fan_Sho p?hash=item20af12e024

I imagine it's about 1/16" or less think wool banner. Thanks in advance.

jjmbxkb

01-26-10, 08:50 AM

Try www.realtraps.com where there are measurements of similar devices.

Thanks for the link. It really helps me with the basics.

forestmoonstudio

01-26-10, 04:35 PM

How much would 1.1 life size standups absorb sound? I will have at least three on one side wall and one on the other smaller side wall. The back wall will have curtains covering a bay window. The front wall is the screen wall.

Would I really need acoustic panels if I have these guys blocking most of the wall space?

My Darth Vader:
http://i203.photobucket.com/albums/aa60/pineyridge/vader.jpg

pepar

01-26-10, 04:39 PM

You're kidding, right? :eek:

NJ Jackals

01-26-10, 05:01 PM

I *think* what he's asking is that he knows the popups are a reflective surface so would that largely defeat a treated wall behind it. Either way, the answer to "would I really need acoustic panels" is "yes".

forestmoonstudio

01-26-10, 05:27 PM

PEPAR, no I am not kidding.:D

NJ, these are not cardboard standups. These are costumes on manniquins. Sorry for the confusion. Do you think they will absorb or reflect sound? I would think that a body ( Human or mannequin ) would absorb sound. I would hate to buy acoustic panels only to be covered up by my mannequins.

Terry Montlick

01-26-10, 06:09 PM

forestmoonstudio

01-26-10, 07:00 PM

Thank you Terry. That answers my question.

KERMIE

01-26-10, 07:06 PM

Anyone know at what Frequencies the average NON-AT screen reflects and lets pass through?

The thought was since my Screen will be about 2 Feet in front of the front wall to build a 4 inch deep SEALED frame filling with Rigid Fiberglass then set the screen (100" diag) on the frame. You would have a:

94" x 56" x 4" trap floating 2 feet off the front wall centered between the left/right, floor/ceiling.

Would this do any low/mid Bass Trapping even though it is not in a corner?

yacht422

01-27-10, 08:03 AM

Hard and curvy, so in general good diffusers. You could still benefit from acoustic panels, because indirect sound will still reach behind the mannequins and improve reverberation times and dialog intelligibility.
This begs the question: is it the shape that matters, or the construction material that matters(or a little of both)?
If one were planning on half round diffusers, floor to ceiling, would it matter if one were to use the cardboard footing tubes(cut in half) or plastic pipe(again, cut in half) etc.
Would they be placed empty against the wall, or filled with f/g or rock wool. - - - or, in the final analysis, are commercially manufactured tubes truely the best way to go?! (toole recommends a combo of tubes and shapes -i am looking at tubes, for now)
Walt

Terry Montlick

01-27-10, 08:16 AM

This begs the question: is it the shape that matters, or the construction material that matters(or a little of both)?
If one were planning on half round diffusers, floor to ceiling, would it matter if one were to use the cardboard footing tubes(cut in half) or plastic pipe(again, cut in half) etc.
Would they be placed empty against the wall, or filled with f/g or rock wool. - - - or, in the final analysis, are commercially manufactured tubes truely the best way to go?! (toole recommends a combo of tubes and shapes -i am looking at tubes, for now)
Walt
I was only addressing the special case of manniquins space somewhat away from the wall. Hard convex rather than concave surfaces should always be used.

Weasel9992

01-27-10, 03:46 PM

Would I really need acoustic panels if I have these guys blocking most of the wall space?

I just want to be the first one to express my geeky delight at that Darth Vader mannequin. That is super cool.

Frank

yacht422

01-27-10, 08:12 PM

I was only addressing the special case of manniquins space somewhat away from the wall. Hard convex rather than concave surfaces should always be used.
thx for the response. however, one question remains: should the hard convex unit be empty or stuffed with adsorbing material? and, if we are diffusing, is the diameter important ( say, 12" vs: 6")[ X 8' long], or is the number of them a bigger factor. (so much to know, so little time)
walt

highlife

01-28-10, 09:35 AM

Hi, I am ready to address treatments now that my room is mostly complete. I have read many posts in this thread and have ideas of what and where to place treatments. I would like to confirm my thoughts with the experts in this thread! Here are a few pics so you can see my challenges. Behind the screenwall is a problem and I feel I will need to treat the entire wall area. I have not hooked up components yet so I dont know how bad it may be. So, besides the area behind the screen wall, would you recommend side wall or rear wall treatment? I am not considering ceiling as the height is an issue at only 80".

Many thanks for your thoughts and advice!

pepar

01-28-10, 10:05 AM

highlife

01-28-10, 11:54 AM

pepar

01-28-10, 12:14 PM

Thanks Jeff, I looked through your build site. The back of my screenwall is different in that it is not fully enclosed. I walk through the other side of the basement, behind a water heater, to get to that space. By blocking it off with say, triangle bass traps, I block off my entrance. The panels in front can be removed, but they are wedged in there pretty tight and would be a hassle to remove. The other corner behind that wall has a gas meter, which would limit the corner traps to about 36" high.

Questions:

1. Would it still be somewhat effective to trap the 36" of corner space (floor to gas meter)?
2. For the entrance side, could a thicker panel be placed, say behind the main speaker, for bass traps? Does linacoustic traps all frequencies?
3. How do you determine first reflection points on the sidewalls?
4. With the back of my room being open to a stairwell, is treatment effective?

Many thanks!
At a certain point, you should do some acoustical measuring. But I think it is safe to add bass traps without doing that. Traps are best in corners, and don't only look at wall/wall corners. Floor and ceiling intersections with walls count as well. It is almost impossible to have too much bass trapping.

Here is a site (http://www.bobgolds.com/AbsorptionCoefficients.htm) with a LOT of test data for various materials typically used for absorbers. You will probably need to go somewhere like this (http://forum.studiotips.com/viewforum.php?f=8&sid=8380a48b667debb6e42f0e7369db5195) to learn more about BASS TRAPS.

Calculate where to place absorbers for first reflection points? Ever play pool? :)

highlife

01-28-10, 04:42 PM

pepar

01-28-10, 06:21 PM

I was hoping to get some advice based on the photos I posted, not to become the resident expert on measuring frequency responses. I appreciate your reponses Jeff, don't get me wrong, but reading test data is not what I was looking for.

I believe I will need to cover the entire wall behind the screen with linacoustic, or something similar. The corners will be a challenge due to the reason previously stated, and I can do my best to place as many traps possible given the space. Still clueless on first reflection points on sidewalls, is there a basic distance formula front the front speakers? And rear walls, do they require sound absorption as well?

Thank you.
I would cover the entire wall, no actually the entire cavity, behind the wall. Beyond that, this is a place to come to learn how to fish, not to be given fish for free. There are members here who make and sell acoustical treatments that could probably ask you some simple questions and make recommendations to you. To continue with my metaphor, they will recommend which fish you buy from them and where (and how) to mount them. :)

The first reflection points are all about the locations of the speakers, the locations of the listeners and the distances. You could do the mirror/flashlight trick, or you could visualize pool shot angles.

Back wall? Depends on how the room is laid out and, more importantly, how it measures.

Elill

01-28-10, 07:50 PM

Anyone know what the minimum recommended seating distance is from a BAD panel?

Also if anyone can tell me the diameter of the holes that would be useful.

Anyone?

KERMIE

01-29-10, 01:28 AM

Anyone know at what Frequencies the average NON-AT screen reflects and lets pass through?

Guys, any help on this. Or should I ask, what Frequencies does the average screen reflect?

Thanks in advance

yacht422

01-29-10, 02:29 PM

Guys, any help on this. Or should I ask, what Frequencies does the average screen reflect?

Thanks in advance
you might call your screen maker - they would have the best info on their own products(which may vary from mfg to mfg)

adammb

01-29-10, 03:22 PM

kevinzoe

01-29-10, 06:52 PM

thx for the response. however, one question remains: should the hard convex unit be empty or stuffed with adsorbing material? and, if we are diffusing, is the diameter important ( say, 12" vs: 6")[ X 8' long], or is the number of them a bigger factor. (so much to know, so little time)
walt

***************
Walt,
As luck would have it I'm finishing building TWO hemi-cylindrical diffusers (sometimes called polyfusers or 'those round things on the wall'). I've re-studied Toole's section in his latest book and communicated with his protege Dr Sean Olive a week ago about this very topic, before I made too many mistakes. . .

For the Harman listening room they used a 48" diameter Sonotube concrete forming tube and cut in in half (i.e. 180 degrees) with a radius of 24". They then applied Dynamat Xtreme car panel (http://www.dynamat.com/products_automotive_dynamat_xtreme.html) on the inside of the tube (concave part) to help stiffen it and reduce resonances. They filled the inside cavity with fibreglas and wrapped it in fabric and used cleats to hang it on the wall. You can see it on the rear walls of their room in this link:
http://seanolive.blogspot.com/2009/05/harman-international-reference.html

For my project I also chose a 48" diameter sonotube but used a 130 degree arc to get the right wall width coverage and radius extending into the room (called Sagitta) given my smaller room size and proximity to the listening positions. I used the following program to do "what if?" scenarios with various values for radius and degree arc to calculate the "sagitta," "chord length" and "circumfrence."

http://demonstrations.wolfram.com/SagittaApothemAndChord/

I also used Dynamat on the interior and they filled the inside cavity with Owens Corning 701 Fibreglas wrapping it in plastic to prevent any loose fibres from entering the room. I made sure to mark a 6.5" line within the cavity which I used to mark where the fibreglass will start in order to create an air space between the wall and the start of the fibreglass, which equates to about 1/4 the wavelength of about 500Hz which I'm being conservative as estimating my Schroeder or transition frequency to be. I used 2-3 1"*2" studs on 'L' brackets to keep the fibreglass from springing back past the 6.5" line. Finally, I wanted a look more luxurious than cloth for a cover so got some red oak veneer with self adhesive glue already on it and all you need is a hot iron to melt the glue to the outside convex part of the tube. Be sure to sand the tube's exterior first to remove the wax so the veneer will bond with it.

The radius or Sagitta that extends into the room is only important if you wish to use it for bass trapping, which never hurts. The deeper the radius/sagitta the lower the bass trapping will work. Also the hard wood veneer will diffuse the mid/high frequencies.

Finally, if you are planning on using multiples of them on the same wall, you have to be careful to space them out and/or randomly place them and/or change the radius of each one.

Clear as mud, again?

kevinzoe

01-29-10, 07:53 PM

I have a room that is 22'x19'x7'5" and a fireplace in left rear of the room. I was planning on adding OC703 to the entire front wall and the side walls at 4.5' up on the wall. I am also going to have partially false soffits in which I will put cotton batting to absorb the bass. On top of that I have Auralex Lenrds that I will have on the front wall and I am not sure about the rear wall. Can someone please help me find a diagram of some sort of recommended placement. I know every room is different but it seems the more I read about this the more options I get. I can get 1",2", and 4" OC703 and will be placing this behind fabric panels made of GOM. I am going to be using this room for 96% home theater in an 11.1 setup using height channels. I am afraid since my ceiling is so low that I cannot put any treatment on the ceiling but I may change my mind down the road. Can someone have too many bass traps as I was going to make the stage and riser into bass traps.

Any and all help would be greatly appreciated. If you want some more details about my build my thread is Sweetwood 11.1.

Thanks:)

*****************
"I was planning on adding OC703 to the entire front wall and the side walls at 4.5' up on the wall"

Firstly, do you really want/need to absorp the entire front and side walls as it sounds like you'll make it too dead sounding, but to each his own . . . Secondly, use a minimum of 3"-4" thickness of your absorbing panels to act as a broadband absorber -- too thin and it'll just act as a treble attenuator throwing off the spectral balance that you paid dearly for from your beloved speakers.:) Thirdly, the acoustical treatment should start 1 foot below your ear level and extend to 3 feet above your ear level, at the very least, which may or may not coincide with your "4.5' up on the wall" statement.

"Can someone please help me find a diagram of some sort of recommended placement"

Read Dr Floyd Toole's latest book to educate yourself before you waste money or build things incorrectly. He is as knowledgable and unbiased as any trusted source of info can be. The last chapter is where he lays out where different kinds of HT acoustical treatments ought to go - very helpful! Just so you know, he recommends absorption in the middle of the back and front walls with diffusion on either side of the absorption.

"Can someone have too many bass traps . .. "
Great question. You can guess at what the answer is if you ask any of the bass trap manufacturers . . . Since all small rooms suffer from bass modes you will need a combination of multiple subwoofers, bass traps, and parametric EQ to get the bass right. Typically the more bass traps you use the better the peaks and nulls become (i.e. lowering a peak and raising a null) while reducing ringing time and reverb time. BUT you will also need to turn up the bass volume. There are 2 other problems: (i) the bass traps don't magically stop working at say 500Hz which would be ideal, they keep on absorbing higher frequencies, albiet less effectively the higher up in freq you go, which only compounds the dead sounding room problem, and (ii) manufacturers don't always tell you how to properly set the bass traps up to max their effectiveness which may be self serving to get you to buy more of them. For resistive types made from fibreglass you need to pull them away from the wall by about 6-7" and have them extend as far into the room as possible to work at lower frequencies. Diaphragmatic bass traps work differently and work best when hung right on the wall where the air particle pressure is maximum - this obviously has a much smaller foot print. To counter the bass traps absorbing higher frequencies, try putting something hard like a sheet of plywood in front of them so that mid-higher frequencies will reflect off of it while bass frequencies won't even "see" the plywood.

hope this helps . . .

kevinzoe

01-29-10, 08:43 PM

I have two questions regarding primitive root (skyline) diffusers:

1) How would substituting round wooden dowels for square rods affect performance?

2) How would mounting these dowels (or rods) on a curved surface, such as a large polycylindrical diffuser, affect performance?

Thanks,
John
************************
John - interesting questions you pose.

Question 1: I would expect that replacing square with round wooden pieces will significantly add to the absorption of the diffuser due to the additional open spaces between round shaped dowels. I don't think you want to raise the absorption level of a diffuser, otherwise you'd have put an absorber there instead of a diffuser . . . If round shapes would have worked, then I would surmise that RPG and others would have used it.

Question 2: If you are going to use a hemicylindrical diffuser and attach round dowels perpendicular to the hemicyclindrical's surface, then you are in theory creating a 2 dimensional diffuser; if the hemicylindrical is oriented vertically then it diffuses sound horizontally, while the round dowels are oriented horizontally and would diffuse sound in the vertical plane. Nice idea but I think a better 2D diffuser is the Skyline based on whatever prime number is large enough to cover your desired wall space.

Have you used the following Skyline calculator? I've found it to be the best, but there could be others . . .

http://www.oliverprime.com/prd.php

If you want some help in using it, PM me.

Hope this helps some . . .