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Bass traps

post #1 of 25
Thread Starter 
Hello,

I was wondering if anyone had any opinions on wether or not this would be a good material for bass traps.

http://www.ebay.com/itm/4-x-27-x-82-Foam-Rubber-Sheet-Cushion-Replacement-/310491197429?pt=LH_DefaultDomain_0&hash=item484ab7aff5

Even if this may not the absolute perfect material, if the edges were cut to 45 degree angles, so as to be stood up in a corner and appear to be flat at a 45 degree angle to the walls forming a corner, could one expect to have a significant bass trapping effect? The attached picture should give a idea of what I'm describing.



How about these?

http://www.youtube.com/watch?v=iyYUpkpL0gw

Any advice/opinions greatly appreciate!
Thank you in advance
post #2 of 25
Thread Starter 
Sorry, accidental double post. Please delete other post if possible. My apologies.
post #3 of 25
Usually bass traps are made out of Owens Corning 703 Fiberglass, or Roxul Mineral wool. Placement straddling a corner is (sidewall/front, sidewall/ceiling,
sidewall/floor, sidewall/rear) recommended. 4" or thicker is recommended. I don't recommend any type of foam (at least that is the thought at Real Traps,
and other acoustic web sites)....I'm sure some will say foam is fine. Some use regular fiberglass insulation (like you use for walls etc (R19 or whatever).

A good place to purchase materials for bass traps is http://atsacoustics.com/ Their prices can't be beat IMO. I had them make 4 bass traps for me in micro
suede fabric, roxul wool. 2 for the sidewall/front and 2 for the sidewall/ceiling (in the front). All 2'X4' by 4" thick with no backing (the 1/4" ply they normally use on the back
of their panels). This helped flatten (smooth out the bass).....and measured as such.

Some guys use 3 or 4 mil milar covering the trap as this helps keeping some of the higher frequencies from be absorbed.

For do it your self materials can be bought reasonably at......http://www.atsacoustics.com/cat--DIY-Acoustic-Materials--102.html
I'm no expert but you can find out a lot more by reading http://www.avsforum.com/t/255432/acoustical-treatments-master-thread

vardo
Edited by vardo - 10/28/12 at 5:59pm
post #4 of 25
Thread Starter 
Vardo,

Thank you for the information! I think I'm going to go the same route. I've been doing a lot more reading, there are quite a few threads out there already covering the subject, and it seems my situation calles for exactly the same thing you describe. I think I'm going to make some traps with the Roxul wool and place them at the first reflection points.

However, I have 16ft vaulted ceilings in my living room so do you think it would make sense to also make several to put higher up on the walls and ceiling? When standing in my room I get the "clap echo" and am pretty sure that mose of it is due to so much bare drywall real estate up there. I don't have all the technical equipment to measure the room but all the threads I read about using these at reflection points seem to yield good results and was wondering if I should also try to dampen the sound higher up in the room or if I would be wasting the energy/money.

Any advice greatly appreciated.
Thanks again for the help!
post #5 of 25
Quote:
Originally Posted by vardo View Post

Usually bass traps are made out of Owens Corning 703 Fiberglass, or Roxul Mineral wool. Placement straddling a corner is (sidewall/front, sidewall/ceiling,
sidewall/floor, sidewall/rear) recommended. 4" or thicker is recommended. I don't recommend any type of foam (at least that is the thought at Real Traps,
and other acoustic web sites)....I'm sure some will say foam is fine. Some use regular fiberglass insulation (like you use for walls etc (R19 or whatever).


if you're limited to using porous-only velocity-based LF absorbers, then there are three (3) key metrics to consider:

1- the thickness of the absorber. porous insulation is a velocity-based absorber and thus must be placed (spaced away from rigid boundary) into areas of higher particle velocity in order to be effective. at the rigid boundary, pressure maximizes while particle velocity goes to zero (thus, thin porous absorbers are not effective at LF absorption). sufficiently thick traps must be utilized to be effective to the lower (longer) wavelengths. you can also utilize an air-gap to space the insulation away from the rigid boundary (akin to a "free lunch", if you will).

2- the size of the absorber. the absorber must be as large as possible (with respect to wavelength) such that the LF wave does not simply diffract around the absorber. placement within the corners helps force the wave through (across) the porous absorber. sq area/coverage is key, but care must be taken such that the large (broadband) LF absorbers do not overly attenuate the specular region as well - as the porous material is broadband in nature. thus, a reflective barrier can be utilized to restrict this (plane surface, scattering or diffused surface preferred - but depends on the overall specular response one wishes to achieve). 6mil plastic wrapping on the outer face of the porous absorber will begin to reflect indirect specular energies 500hz and up.

3- the gas-flow-resistivity of the porous material. GFR, not density as so commonly mistated, is the key value regarding the modeling of a porous absorber. since you are interested in LF absorption, sufficiently thick porous absorbers must be utilized to space the porous structure away from the rigid boundary and into areas of higher particle velocity for the lower (longer) wavelengths. as you construct thicker and thicker traps, you'll want to utilize a material with lower gas-flow-resistivity. fortunately (for once), the most effective material is actually the lowest cost. sufficiently thick traps of pink fluffy attic insulation (~5000rayls/m GFR) is more effective for LF absorption than the denser (higher GFR) oc703, oc705, and equiv mineral wools. the pink fluffy should be loosely filled and uncompressed!. you can hang strips of the pink fluffy from the ceiling down, and/or utilize orchid bird netting to constrain the insulation - and wrap with plastic membrane (6mil plastic as mentioned above) or a more complex scattering/diffusion device if resources allow.

attenuating the LF energy such that the reflected signals are lower in gain (and thus cause less destructive interference within the frequency-response) is one benefit, but they will also decrease the LF decay times as evident within the waterfall/CSD plot.

references:
AFMG SoundFlow (free for 30-day trial): http://soundflow.afmg.eu/index.php/sf-features-en.html
Porous Absorber Calculator (with transfer matrix calcs borrowed from Acoustic Absorbers & Diffusers (Cox/D'Antonio): http://www.whealy.com/acoustics/Porous.html
post #6 of 25
Good information from localhost127. He is probably the most informative poster on the acoustical treatments master thread.

The science of acoustic treatments for a room is not easy to understand. Most people read a book on it and still come away confused.
Others will make a sketch or layout of the room and send it to someone like Ethan Winer of Real Traps and ask for acoustic information
on trap/diffuser placement and quantity (but there is usually a fee involved or you have to buy their products). The Real Traps web site has a good
bit of acoustic information...realtraps.com.

If you are going to make bass traps from the first reflection point, then you will need an air gap between them. Maybe a 4" trap with a 2" air
gap (possibly using tubing spacers) from the wall. Also I recommend the traps be covered by 4/6 mil of mylar because the traps will absorb
a lot of the higher frequencies...you don't want to have a dead sounding room.

Usually 2" traps placed against the wall (made from roxul or 703 fiberglass) will stop the slap echo...because the higher frequencies are absorbed.
This is usually done at the first reflection point and or even the second reflection point (speaker on the opposite side). I ordered 4 2X4, 2" panels
from ATS (plywood backed)...but with 4 absorption panels on the wall(s) my room became to dead sounding. One on each side was enough. You can place
absorption panels on the ceiling, up higher on the walls, or on the wall behind the main speakers.

I suggest you make a minimum amount, and see what the effect is. Taking measurements of the sound in your room is very important in regards
to ordering, making absorption panels and their placement.

My 2 cents.....vardo
post #7 of 25
Quote:
Originally Posted by vardo View Post

If you are going to make bass traps from the first reflection point, .....

bear in mind my comments were with respect to LF porous absorbers (for wavelengths within the modal region of a given small acoustical space), not broadband panel absorbers that are used for attenuating indirect specular reflections (that behave/can be modeled as light (angle of incidence = angle of reflection) as you are now discussing. we know from Delaney, Bazely, and Miki models (and subsequent modifications, as they satisfy all of the various mods to it) - that 4" absorber w/ 4" air-gap (of the commonly sourced and often recommended rigid fiberglass 3pcf or 4pcf mineral wool) will be sufficient to fully attenuate a broadband indirect signal to the lower Schroeder cut-off region of which is 250-300hz in typical volume home residential spaces.

if the choice has been made to attenuate such indirect first-order reflections within your space, then ideally you would want to utilize a sufficiently thick porous absorber that fully attenuating the indirect specular reflection, and doesn't merely eq/color/filter the reflection by attenuating the mid-HF specular band but allowing the lower band to persist.
post #8 of 25
Thread Starter 
Well, given that you guys are obviously the ones to talk to about this, I suppose I need to give a little more insight into my exact situation so you know why I'm asking to begin with.

Here are a couple of picture of my living room where I am setting this all up as well as an updated pic of the work I had to do to the mantle to get the new center channel speaker to fit. The mantle has since been completed and painted as of the time this pic was taken.







The speakers shown in these pictures, except for the last picture of the mantle, are focal's. They are bookshelf speakers that I recessed into the wall when we got the tv set up over the mantle thinking that was just awesome. rolleyes.gif After having the Focal's for some time, it became more and more annoying that sometimes I would have a hard time making out voices, etc. and the 8in sub that came with the kit was a far cry from what I needed to fill that space so I thought that just getting bigger better speakers would do the trick.

Anyway, these focals are gone now, the holes are patched up and in their place, on Omnimount 60.0 brackets, are Paradigm Studio 20 bookshelf speakers, a cc-590 center on the mantle, and ADP-590 surrounds, which are actually coming in the mail today and I have not fully decided how to mount just yet. The ADP's however, will not be mounted on the wall behind the couch, on either side of the window like the focal's are now. They will most likely go on side walls, to the left and right of the couch. I was thinking of putting a couple of acoustic panels on either side of the window where the focals currently reside. The Studio 20's are pointed slighty in from an apporximate 30 degree angle and the cc-590 center as well as the Studio 20's are all pointed slightly down into the listening position. The center channel, as you can see, has to no choice but to be butted up against the stone, as there is just no other place to put it. It is rear ported and I've plugged the port with styrofoam and the sound seems to be quite good out of it. I can not hear any chuffing or boomy muddy bass/sound from it. Would it be of benefit to put some Roxul insulation behind it?

Also, I have replaced the 8" sub with the Premier Acoustics PA-150 15" subwoofer. I have an Onkyo tx-sr507 (which can be seen in the right side of the third picture) with Audyssey which I have learned is much better at setting up the speakers the way they should be than I am. So I've run Audyssey, it has the speakers crossing over at 70, etc., and I've set the subwoofer accordingly and have not touched the settings there after. The sub is sitting in between the big fluffy chair and the end table, basically under the receiver that is mounted to the wall behind the fluffy chair. It is a couple of feet away from the wall and pointed straight out into the room.

So here is the problem. With Audyssey set up, speakers set up to the best of my limited acoustic ability, when I put a movie in and watch it for a while, (LOTR, or Master and Commander, any good surround sound movie) it initially seems to sound awesome, but I still feel like I should be able to hear the voices clearer and as if that wasn't annoying enough, after a short bit, I notice that my ears are actually starting to hurt which makes no sense to me because I am not playing it louder than when I go into a movie theater and my ears aren't hurting when I'm done watching a movie in a theater. This led me to search google and I find a thing called "listening fatigue" and it seems to be from horrible acoustics more than anything. I know its not the Paradigms because I auditioned them for quite a while and bought them specifically because they were so much easier to listen to than the Klipsh's which I did noticed were hard on my ears.

So that is where I am at, and is why I am looking at acoustic panels, etc. I was thinking of putting a couple acoustic panels above the love seat at the first reflection, and maybe a couple more on the slanted ceiling above the couch at reflection points there, and was considering putting them higher up on the walls, above all the pictures to help deaden the sound echoing out of the cathedral ceiling. Also a couple on either side of the picture window. We have some nice thick black-out blinds that I can draw down in front of the window, as well as the curtains to help keep noise from bouncing off the glass. For a reference of scale on how large the room is, the tv is 65". Also, with the bookshelf speakers on the Omnimounts, they are only about 8" away from the wall so should I put an acoustic panel directly behind them as well?

Any insight into how to better this situation is greatly appreciated.
Thanks for all the great input so far!!
Edited by GrasaDeCastor - 10/30/12 at 9:13am
post #9 of 25
Nice speakers (Paradigm) and the PA-150 sub is very good for mid bass (consider getting a second one when funds allow).

Like I said in a previous post that I'm be no means an expert (Iocalhost is). Just a guess but I would address first reflection points,
and putting absorption panels on the walls, ceiling etc. You have a lot of extra wall(s) there and the echo you are getting is IMO
bothering your ears or causing listening fatigue.

Bass traps are great (when done right), and IMO the more the better. But I think high freq reflection absorption panels will deaden the room,
so as not to cause ear fatigue and smear the vocals. Just looking at your room the slap echo must be off the chart.

Also if there was anyway of bringing the front speakers out further from the TV (more) that would help. Two bad you are limited on space on either
side of the fireplace. Just looking at the omni mount brackets on line it appears when mounted they will be further out from the wall (like you said
8") and also mount them maybe at the midpoint of your TV and aimed directly down toward your listening area.

The 2" roxul wool absorption panels (2" with ply back) I ordered from ATS work great for absorbing the higher frequencies (which like I said is smearing the sound
and creating listener fatigue due to a overabundance of higher frequencies).

Post your question and pictures on the acoustical treatments master thread....you will get a lot of different opinions and questions. Everything from have you
done measurements of the room or have you read a book on acoustics....etc, etc...
There are a lot of very knowledgeable on that forum (more so than I), localhost, Denis Erskine, GIK Acoustics and so on.

You have a nice room (listening area there) and have spent some good money on equipment...so it needs to be enjoyed as much as possible. smile.gif

Good luck, vardo

EDIT: this site from Real Traps may be helpful
http://www.realtraps.com/placing_mt.htm
Edited by vardo - 10/30/12 at 2:19pm
post #10 of 25
Thread Starter 
Quote:
Originally Posted by vardo View Post

Nice speakers (Paradigm) and the PA-150 sub is very good for mid bass (consider getting a second one when funds allow).
Like I said in a previous post that I'm be no means an expert (Iocalhost is). Just a guess but I would address first reflection points,
and putting absorption panels on the walls, ceiling etc. You have a lot of extra wall(s) there and the echo you are getting is IMO
bothering your ears or causing listening fatigue.
Bass traps are great (when done right), and IMO the more the better. But I think high freq reflection absorption panels will deaden the room,
so as not to cause ear fatigue and smear the vocals. Just looking at your room the slap echo must be off the chart.
Also if there was anyway of bringing the front speakers out further from the TV (more) that would help. Two bad you are limited on space on either
side of the fireplace. Just looking at the omni mount brackets on line it appears when mounted they will be further out from the wall (like you said
8") and also mount them maybe at the midpoint of your TV and aimed directly down toward your listening area.
The 2" roxul wool absorption panels (2" with ply back) I ordered from ATS work great for absorbing the higher frequencies (which like I said is smearing the sound
and creating listener fatigue due to a overabundance of higher frequencies).
Post your question and pictures on the acoustical treatments master thread....you will get a lot of different opinions and questions. Everything from have you
done measurements of the room or have you read a book on acoustics....etc, etc...
There are a lot of very knowledgeable on that forum (more so than I), localhost, Denis Erskine, GIK Acoustics and so on.
You have a nice room (listening area there) and have spent some good money on equipment...so it needs to be enjoyed as much as possible. smile.gif
Good luck, vardo
EDIT: this site from Real Traps may be helpful
http://www.realtraps.com/placing_mt.htm

Thanks for the advice Vardo,

Like you said, I think I'm gonna get some Roxul and make several panels and try strategically placing them about the room and test them in different areas, first reflections, etc. I'll also copy this post and submit it to the Acoustic treatments master thread. I didn't know that one existed. Thank you for the heads up!
post #11 of 25
As has been said localhost knows his stuff. To get the best results I would look into measurement equipment for ETC, freq. response, bass decay... The rabbit hole can go quite deep to say the least.

Now if thats too much some things can be done that will be of benefit IMO. For better audible diaglog I would work on center channel. Your right wall is closer to speakers than the left wall. This will disrupt the balance as you are getting earlier arriving with higher gain reflections from that side. Seeing you have art on that wall maybe a few of these would work.

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

I use the 244 panels in basic black with a 4" air gap myself for specular reflections.

Also the window behind you will be reflecting as well. Someone else can probably lead you in the best direction, but some type of heavy material that can aborb as broadband as possible would be advised such as heavy drapes. Now something not broadband will color the reflection/sound, but if it does some over the vocal range it will help dialog. Sometimes compromises have to be made.

A thicker rug that absorbs more broadband would help vocals and fatigue as well. Also if that glass table is at the angle of incidence it will reflect as well.

I think panels where current surrounds are to get first reflection from them and moving new speakers to the sides would be helpful for surround sound.

Bass traps are of definite benefit, but as they stated above size matters with bass traps and long wavelengths. Sometimes big bass traps in multi purpose rooms at high particle velocity areas will not go over well with the non audio folk and room decor. Subwoofer placement is key, and multiple same subs are a good thing.

All IMO, good luck!
post #12 of 25
The window itself is a bass trap. No window, or drapes for that matter, is going to keep low frequency energy from leaving the room. No energy reflection of the frequency means, no worries. Now, if you are talking about sound and light coming from outside, well that's a different matter altogether as well as shaping the acoustical presentation within the room itself. Drapes are essentially useless for anything but higher frequencies, but those I would prefer to stick around rather than be absorbed. There is a function of some absorption based on the distance of the curtains from the boundary, but there isn't much broadband about it. In essence, there is one BIG bass trap in the rear. To be honest, you have many other problems in the room that are more important than worrying about the bass trapping. smile.gif
post #13 of 25
Quote:
Originally Posted by SierraMikeBravo View Post

The window itself is a bass trap.
A window may allow bass to pass through it more easily than a wall, but that doesn't make it a trap. Windows are also highly reflective of mids and highs and if they're large should be covered with drapes or curtains. Follow this link to definitive explanations of bass traps and room treatments in general by probably the #1 authority in that field:
http://www.realtraps.com/articles.htm
post #14 of 25
Shawn you are absolutely correct about the window. This thread started off about bass traps, but seeing the pictures of the OP's room, I think the problem is an over abundance
of high frequencies (reflections) that are bothering the OP's listening experience, smearing the vocals and such, saying the sound hurts his ears after listening for a
while. I think his speaker selection is very good, and the center channel is more than adequate for his listening room ; (he seems to have trouble hearing the vocals at times). As you can see, the walls, ceiling, opening to a stairway which goes up to the second story (another huge wall(s) it would seem to me he has to dampen
the high frequency reflections. Using the curtains in the back will help this, as well as absorbers at first reflection points, and absorbers on the ceiling, walls etc.
will tighten up the sound in his room.

In that room high frequency reflections look to me something to be problematic..
.....I'm no expert at all. I used some bass traps and 2 panels near first reflection points in my small
room, and it improved the sound. It was a minimal expenditure, and being in a small room (that has very little echo), I think I did OK. I'll need more bass traps in
the future (getting bass to sound it's best in a small room isn't easy, as you know).

Working for the Erskine group, and being HAA Design Certified -THX Certified Pro, my knowledge of acoustics pales in comparison yours.
Anymore information from you to the OP would be nice.

vardo
post #15 of 25
Sorry if I sounded like that a piece of cloth or drap would act as a bass trap. After seeing pictures I was in easy changes mode to help overall presentation. I thought something behind you would be a good idea for more than one presentation consideration and that thickness/material... should be considered by someone other than me.smile.gif Yeah not much mass to stop bass in a window like that. Just an acoustics hobbyist myself, looks like you have a lot of great help here!
post #16 of 25
Thread Starter 
Vardo/Luke/Shawn/Bill

I think you guys are hitting the nail on the head. I started off with bass traps but it seems my problem is more with higher frequency stuff so I am getting acoustic panels, either going to order from GIK acoustics or home made with the Roxul wool. It's starting to look like I'm going to need more than I initially thought so I may end up making them myself. I was also thinking of making an acoustic cloud and hanging it, but I'm not sure if it would be better served up at the peak of the ceiling or down lower near the lighting fixture above the couch. The ceiling looks to be an almost perfect 45 degree angle and I've got the new bookshelf speakers mounted about mid point of the tv, slightly toed in and slightly angled down into the seating area of the couch. If it turns out that the ceiling is 45 degrees, then I should be able to draw a straight line out from the bookshelves to where it hits the ceiling above the couch, and then straight down into what should end up being the listening position, thus giving me my first reflection on the ceiling from the front speakers, yes? (hard to hold a mirror on the ceiling so I'm trying to think outside the box)

Also, I"ve got the ADP 590 surrounds mounted on the side walls now, and the focals that were on either side of the windows are gone. I'm going to buy some of the 3" Roxul wool insulation tomorrow and try tacking it up on either side of the windows, as well as in positions around the room so I can get an idea of how much of an effect it will have on my sound in the room before I fully commit to building/buying the traps. That way, I won't end up with a bunch of traps all sized for certain positions and find out they need to be in other positions.

The Roxul is $36 for 12 4' x 15'' batts so I'm going to try to buy 24 batts, put a few on each side of the window, a few on the wall that is to the right if you are sitting on the couch looking at the tv, some higher up on the walls above the art work and a few on the ceiling around what are hopefully the first reflection points. I'm really looking to deaden the room as much as I can because I believe my problems with the higher frequencies are fairly severe.

I'm less concerned with the bass at this point simply because I've tried listening with my subwoofer turned off and the things I am looking for to improve, voices, listening fatigue, etc., do not get better with less bass. I actually quite like the bass in the room. For the most part, I think Audyssey has done a good job setting up the subwoofer, and I think I have it in a good position in the room, and I don't crank it so loud that it is over powering, but when bass events happen in movies, it is impressive without being distracting. I guess I'm saying I think it sounds natural and while I'm sure there is room for improvement, for the most part the bass sounds like it part of the rest of the system and not a seperate distracting entity. I'm no expert, and I've not heard any really nice expensive subs for comparison to high end, but I can tell you the 15" PA-150 sub I got is replacing an 8" Focal sub and I do know what really inadequate/ muddy bass sounds like on the low end and the PA-150 is not it.

Also, I specifically am interested in trying to put a couple of the Roxul batts on the wall directly behind the front bookshelf speakers since I don't have the luxury of moving them further away from the wall and I wanted to get your opinions on that idea.

Here is a kind of crappy pic I took of the bookshelf speakers tonight so you can see what I'm talking about now that they are up.



Anyway, I guess that is all for now. I'm really excited to get the Roxul batts tomorrow and start playing with them to see what happens in the room. Any thoughts you guys have are greatly appreciated and I want to thank you for the ideas and the direction you've been able to give me so far!

All the best,
GrasaDeCastor
post #17 of 25
Quote:
Originally Posted by Bill Fitzmaurice View Post

A window may allow bass to pass through it more easily than a wall, but that doesn't make it a trap. Windows are also highly reflective of mids and highs and if they're large should be covered with drapes or curtains. Follow this link to definitive explanations of bass traps and room treatments in general by probably the #1 authority in that field:
http://www.realtraps.com/articles.htm

I don't think a couple of 1/8" panes of glass are going to be reflecting an enormous amount of low frequency energy back into the room. The bass trap is outside itself. Most of the energy transmitted moves right through the glass and into the great beyond. I think the neighbor will have to contend with it more than the OP. As mentioned, drapes will work for high frequencies, but not so much for the lower midrange where frequencies are more problematic.

OP...be careful about absorbing too much high frequencies in certain locations. You'll find that to be just as objectionable as not absorbing at all. smile.gif
post #18 of 25
Quote:
Originally Posted by SierraMikeBravo View Post

I don't think a couple of 1/8" panes of glass are going to be reflecting an enormous amount of low frequency energy back into the room. The bass trap is outside itself. Most of the energy transmitted moves right through the glass and into the great beyond.
Sound doesn't pass through the glass, it causes the glass to vibrate, and those vibrations are what's heard on the opposite side. While much of the low frequency energy hitting the glass will be expended vibrating the glass not all will, and that which isn't will remain in the room, creating pressure nodes just as a wall will, albeit at lesser levels than a wall. For a window to act as a true bass 'trap', ie., with no pressure nodes created by its presence, it would have to be an open window.
Quote:
As mentioned, drapes will work for high frequencies, but not so much for the lower midrange where frequencies are more problematic.
Agreed, but it's the high frequencies where glass is the most problematic, being a virtually perfect reflective medium for highs. I have cellular shades in all my windows, which by dint of their shape and construction damp reflections well into the upper midrange as well as greatly improving the heating/cooling energy efficiency of the house.
post #19 of 25
It seems most of the posters in here have already covered the fundamentals around design, material, and coverages so I'll leave that area alone.

*If you're interested in DIY - it's super easy!*

As for the acquiring the material - Look for local insulation suppliers - SPI is a popular nationwide chain. You can likely pick up the OC703 or equivalent for MUCH cheaper than it is sold online, especially taking shipping out of the equation. For reference, if you're looking at rigid fiber board - anything 2" thicker or better, unfaced, and with a 3# / cu foot density is great. I wound up with Johns Mansfield 814 I believe which cost me around 70.00 for 9 2' x 4' pieces (1 case). 2 cases later I've covered both front corners floor to ceilling, one rear corner, and 4 reflection points on the walls with a sheet left over. All of my treatments are 4" thick.

See the link in my signature (Gorilla's playroom) for details on my builds.
post #20 of 25
Quote:
Originally Posted by Bill Fitzmaurice View Post

Sound doesn't pass through the glass, it causes the glass to vibrate, and those vibrations are what's heard on the opposite side. While much of the low frequency energy hitting the glass will be expended vibrating the glass not all will, and that which isn't will remain in the room, creating pressure nodes just as a wall will, albeit at lesser levels than a wall. For a window to act as a true bass 'trap', ie., with no pressure nodes created by its presence, it would have to be an open window.
Agreed, but it's the high frequencies where glass is the most problematic, being a virtually perfect reflective medium for highs. I have cellular shades in all my windows, which by dint of their shape and construction damp reflections well into the upper midrange as well as greatly improving the heating/cooling energy efficiency of the house.

If you have the need to get super techincal, mechanical energy vibrates air molecules as well, so even if the window was open, it is still vibrating air molecules and is not passing through nothing. Yes, I am well aware of the physics. For all intents and purposes the glass offers little resistance, and on a first order cursory observation, you could say it "passes" through with little affect. I am sure we could write a Ph.D. dissertation on the effects of propogating waves eminating from a point source where electrical energy is converted to mechanical energy resulting in the vibration of the cone of the speaker which then results in the vibration of air molecules causing increased pressure on the tympanic membrane which then transmits sound to the ossicles and then to the cochlea. Or, we could just call it good and say that the magnitude of the vibrational energy of the window panes resulting from low frequency sound wave interaction and emission is insignificant next to the power of the force...errr wait...(had to say it but sounds better in Darth's voice) is insignficant next to that of the surrounding boundaries. smile.gif
post #21 of 25
Quote:
Originally Posted by SierraMikeBravo View Post

If you have the need to get super techincal, mechanical energy vibrates air molecules as well, so even if the window was open, it is still vibrating air molecules and is not passing through nothing. Yes, I am well aware of the physics. For all intents and purposes the glass offers little resistance, and on a first order cursory observation, you could say it "passes" through with little affect. I am sure we could write a Ph.D. dissertation on the effects of propogating waves eminating from a point source where electrical energy is converted to mechanical energy resulting in the vibration of the cone of the speaker which then results in the vibration of air molecules causing increased pressure on the tympanic membrane which then transmits sound to the ossicles and then to the cochlea. Or, we could just call it good and say that the magnitude of the vibrational energy of the window panes resulting from low frequency sound wave interaction and emission is insignificant next to the power of the force...errr wait...(had to say it but sounds better in Darth's voice) is insignficant next to that of the surrounding boundaries. smile.gif

I think you missed BIll's point. If the window were an open hole, no sound would reflect at any frequency from the "window" (including of course bass frequencies) in which case it would act like a perfect bass trap in that the bass energy that "strikes" the opening to outdoors is gone from the room forever (which we could perhaps emulate with 15 or 20 feet of porous absorber). Since Bill designs bass reproduction systems for a living, I tend to trust his POV even if I don't grok it at first.
post #22 of 25
GrasaDeCasta...make sure you order Roxul Rockboard 60, because it's rigid. It's has good absorption properties just like Roxul AFB. The panels I had made
from ATS are made with Roxul AFB, which is fine because it is in a frame and covered by material. It's not rigid at all. You are going to be handling these and putting them
in different spots etc...you don't want them to fall apart on you.

Another suggestion Luke Kamper made is to get a thicker (and also maybe larger carpet). I think it's a good suggestion, but of course may not be in the budget.

Best of luck and let us know how this all turns out.

vardo
post #23 of 25
Quote:
Originally Posted by JHAz View Post

I think you missed BIll's point. If the window were an open hole, no sound would reflect at any frequency from the "window" (including of course bass frequencies) in which case it would act like a perfect bass trap in that the bass energy that "strikes" the opening to outdoors is gone from the room forever (which we could perhaps emulate with 15 or 20 feet of porous absorber). Since Bill designs bass reproduction systems for a living, I tend to trust his POV even if I don't grok it at first.

I completely understood his point of view, and he is correct from a purely scientific perspective. My point of view is much broader, and is such that, even with the window in place, the magnitude of the vibrational energy reflected back into the room is irrelevant (meaning, it isn't much) when compared to surrounding materials and boundaries. In effect, glass in place or not, for all intents and purposes, the window acts as a bass trap; for low frequencies. Now, mid and high frequencies, different matter altogether.
post #24 of 25
Quote:
Originally Posted by SierraMikeBravo View Post

In effect, glass in place or not, for all intents and purposes, the window acts as a bass trap; for low frequencies.
Not IME. In practice the areas where glass is found tend not to be problematic with respect to lows as they're seldom located in room corners, but by no means do they absorb low frequencies.
post #25 of 25
Thread Starter 
Well, I'm getting to these informative posts a day late. Yesterday morning I got up and started measuring and finding reflection points. As it turns out, I think the 45 degree ceiling above the couch was the worst culprit. My wife was gone for the day so after about an hour and a half of taping her hand held vanity mirror to the ceiling, sitting, removing mirror and tape and repositioning, sitting again, I eventually found all nine reflection points. 3 on each wall and 3 on the ceiling that were pretty much directly over the seating position. Off to Lowes I go.

I bought all the necessary 1x4's and 2 packages of this:
http://www.lowes.com/ProductDisplay?partNumber=305816-1278-RXSS31525&langId=-1&storeId=10151&productId=3394032&catalogId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

I then went to Joann Fabric and bought 22 yards of tan cloth and 3.5 yards of what they call "duck cloth" which I inteneded to use for the cloud I was going to build. I ended up building 12 Acoustic panels, 3 1/2 inches thick with the 3" Roxul wool inside and a single 10' x 40" acoustic cloud, again full of the 3" Roxul. It took me all day to build and mount most of the panels. Hanging the cloud by myself was by far the hardest part and I didn't quite get all the panels up by the time my wife got home at about 11pm so I had to stop short and will finish tonight or tomorrow. I put two, 6ft by 2ft panels on each side of the window, mounted the cloud directly over the couch covering a huge reflection area. While the panels had to be flush against the wall, I was able to hang the cloud down about 3 inches from the ceiling leaving a nice gap there. Two panels are mounted high up on the wall filling the blank wall space to the left of the fireplace and one panel on the right side. Three panels will go on the wall behind the love seat and two will go on the wall going up the staircase. Two more smaller panels will be mounted directly behind the bookshelf speakers to help absorb the reflections coming from the back of the speakers.

I'm going to have to put some type of hook system on the side walls so (staircase wall and loveseat wall) because when I took the pictures and art down to hang the panels it really was too much and looked ridiculous so if I can leave the artwork there and have a few hooks ready, when I want to watch a movie I can just hang the panels over the artwork and remove them when I am done to preserve the aesthetics of the room. I think this will actually serve a dual purpose because if I hang the panels on a hook system over the artwork it will allow a gap behind the panels to make them more effective. Not to mention keeping my wife happy. Needless to say she is less than impressed with the acoustic cloud now hanging from the ceiling. biggrin.gif

The worst part is I wasn't finished with everything by the time she got home so I only got a few minutes of listening to the movie Supernova at about 11pm but I could already tell the sound was MUCH better. It seemed I could hear the voices much better and clearer and was getting no listening fatigue. The sound was not irritating my ears if that makes sense. I usually watch movies at about level 40 on the receiver and my wife does not like it that loud but last night she was sitting right next to me and didn't say anything about it being too loud.

I'm going to try to figure out some kind of hooking system for the panels on the side walls and am excited to get it finished and run through some more surround intense movies. On a side not when I ran Audyssey with all the paradigms now in place it set them to cross over at 50hz!! Does anyone have any opinions about such a low crossover? Is it because the woffers in the speakers are larger?

I'll try to get some pictures posted in the next day or so of the cloud and panels.

Thank you for all the help and advice!
Edited by GrasaDeCastor - 11/3/12 at 7:58am
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