Acoustical Treatments Master Thread - Page 400 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 277Likes
Reply
 
Thread Tools
post #11971 of 11991 Old 09-14-2017, 05:15 AM
Senior Member
 
Join Date: Jun 2016
Location: Atlanta
Posts: 222
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 16
Quote:
Originally Posted by Mpoes12 View Post
That approach came from the style of one particular very well respected and knowledgeable home theater installer (Erskine). There are lots of good ways to solve the acoustics of a theater and few can be applied universally without accounting for the rooms size, shape, construction, etc. that approach has been one that has worked well for many. Having said that, it's not the approach I took or have used with others.

The above mentioned approach is designed to mitigate early reflections and tame the low frequencies around the front of the room and to evenly lower the RT60 value. I would call it somewhat consistent with the LEDE room as the front is made fairly dead. The plastic increases LF absorption slightly while reducing the lower midrange absorption somewhat. That is good because (for whatever reason) many home theaters have too much absorption in the 300-500hz range. You want to have the flatest RT60 value you can have. In a perfect world it would be around .21-.25 from 20hz to 20khz. That isn't realistic so we usually focus on the 100hz to 10,000hz range and accept a rising RT60 value below 200hz or so. In my room I had a dip in the RT60 value of the mostly untreated room at 500hz. My room averages about .32 with just carpet and one 2" layer of insulation on the front wall, but at 500hz it was .24. Had I lined the entire room with 2"-4" insulation including the front of the room, everything would drop above 300hz and the 500hz dip would be even worse. At the moment my RT60 is flat down to 300hz and then rises as the frequency lowers. I'm working on fixing that still but that's the hardest area to fix too.

So how does this answer your question? That is a good generic approach but it's not a panacea and not doing that isn't automatically wrong. Understanding the physics is tricky and most don't have time or will to learn it, so a general suggestion makes life easy. It is totally possible that following that approach in some rooms could yield poor results.


Sent from my iPhone using Tapatalk
I need to decide what to have the builder do for me during the initial construction. Obviously, anything I can have him do makes life easier. Would you recommend that I treat the front wall with 1" lin/3 mil plastic/1" lin and then evaluate how the room does from there after I move in and set it up?
GatorBlues is offline  
Sponsored Links
Advertisement
 
post #11972 of 11991 Old 09-14-2017, 07:22 AM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by VideoGrabber View Post
Did you really mean 4-feet of depth? Perhaps you're using 'depth' in a different way than I might.



This is your spandex AT screen, correct?

In some small-room configurations, surround-sound speakers can also throw a fair amount of sound at the screen. If it is AT, then absorption behind it may help reduce unwanted first reflections from that source.


I did mean to say depth so I think I am using the term differently. I don't mean depth as in the height from the ceiling. I mean it extends 4' from the screen toward the listener along the length of the room and is 8' along the width of the room. I consider the front to back to be depth.


Yes I have a spandex screen and yes I mean the area behind it. My setup, like many on these forums, uses a portion of the front room to hide the speakers and some of the subwoofers. I have a false wall to cover them and the entire wall is acoustically transparent. I went with extra depth to allow for larger subwoofers (Because AVS is a bad influence) and so I have a 30" deep by 11' wide space that has every surface covered in insulation.


I may not be understanding your comment about throwing sound at the screen. Do you mean the surround speakers (as in effect speakers) that are on the side and rear of the room? If yes, then I would imagine they always throw sound at the screen to some extent and certainly in smaller rooms they would throw more. I would question the need to absorb or diffuse that sound simply because it should be fairly late arrival. The room would need to be really small (and if it is, then I would agree, absorbing that off the rear and front wall would help give an illusion of a larger room). Even then, the temporal difference between the direct sound and the reflected sound from the front of the room would be so great (relative to the size of the room) that it shouldn't have a big effect on clarity. Our ears should actually filter that out largely.


As to your comment about aiming the CD speakers, I would argue that CD speakers were designed specifically to be aimed in the way you mention. They SHOULD be aggressively toed in and using them straight on is the INCORRECT way to use CD speakers. Bill's paper, Dr. Geddes, Harman, Peavey, etc. have all referenced or pushed the concept (and I'm sure there are more I'm not aware of). In talking with some guys that design recording studio's, I was told that the aggressive toe of CD speakers has been the common practice and wisdom of the field for decades. I know there will be people who disagree and prefer something and of course you can do what you want with your own speakers. I just feel that the argument for aggressive toe is based on solid objective concepts that make too much sense to ignore.
Mpoes12 is online now  
post #11973 of 11991 Old 09-14-2017, 07:41 AM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by GatorBlues View Post
I need to decide what to have the builder do for me during the initial construction. Obviously, anything I can have him do makes life easier. Would you recommend that I treat the front wall with 1" lin/3 mil plastic/1" lin and then evaluate how the room does from there after I move in and set it up?

You can do that, I do think treating the wall is critical. I don't know where Erskine landed in his recommendation, I feel like the specifics of the suggestion have changed. I used and prefer to use 2" instead of 1". I know that when asked by another acoustic expert about why he used the plastic and why he preferred less depth, he noted that having a full 4" or more of insulation caused too much absorption at around 500hz. I had thought he was nuts as the common wisdom had been (at least amongst the studio guys) that thicker is better because it extends the LF absorption and most rooms have far too much midrange and HF absorption and not nearly enough LF. When I took measurements of my converted bedroom theater, I did not have this problem. There was no dip in the RT60 at 500hz. When I measured my new soundproof purpose built theater, I did have an unusual dip in the RT60 curve at 500hz. Where as most of the range was around .32s, it dipped to .24s at 500hz. One thing people sometimes forget is that even 1" insulation will absorb 100% of the incident sound (or darn near 100%) above a certain frequency. Going with 2" extends the lower frequency in which 100% of the incident sound is absorbed, but it doesn't absorb any more sound above that point since 100% of it was absorbed. If you go to 4" then again, the LF number is pushed down.


A 2" thick panel typically rolls off its absorption starting below 400hz. A 4" panel starts to move that down to 300hz and usually rolls off in a more shallow manner. If rooms tend to have too much absorption at 500hz then you can see that even a 2" panel is absorbing a bit too much. However, none of this changes the fact that pretty much every room in existence does not have nearly enough absorption below 300hz. The plastic helps reduce some of the midrange/midbass absorption and would increase the LF absorption a decent amount potentially. How much depends on the thickness of the fiberglass behind the plastic. That is why I prefer the thicker 2" absorption myself. I also found that once I installed the first 2" absorption material layer on my front wall, the dip at 500hz in the RT60 went away, it flattened out largely, and what remained was a fairly flat curve that rose dramatically below 200hz. In other words, even without the plastic, my room suddenly had a flat curve but without enough LF absorption.


That means you really need to measure because every room could be different. While I added plastic to a portion of the wall, I also added a lot more insulation to sections of the wall to help. I still do not have nearly enough LF absorption and plan to add a bunch more bass traps in the future. I even have a large corner trap that goes floor to ceiling and is 24' across, but that actually did very little.
Mpoes12 is online now  
 
post #11974 of 11991 Old 09-14-2017, 11:12 AM
Senior Member
 
Join Date: Jun 2016
Location: Atlanta
Posts: 222
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 16
Quote:
Originally Posted by Mpoes12 View Post
You can do that, I do think treating the wall is critical. I don't know where Erskine landed in his recommendation, I feel like the specifics of the suggestion have changed. I used and prefer to use 2" instead of 1". I know that when asked by another acoustic expert about why he used the plastic and why he preferred less depth, he noted that having a full 4" or more of insulation caused too much absorption at around 500hz. I had thought he was nuts as the common wisdom had been (at least amongst the studio guys) that thicker is better because it extends the LF absorption and most rooms have far too much midrange and HF absorption and not nearly enough LF. When I took measurements of my converted bedroom theater, I did not have this problem. There was no dip in the RT60 at 500hz. When I measured my new soundproof purpose built theater, I did have an unusual dip in the RT60 curve at 500hz. Where as most of the range was around .32s, it dipped to .24s at 500hz. One thing people sometimes forget is that even 1" insulation will absorb 100% of the incident sound (or darn near 100%) above a certain frequency. Going with 2" extends the lower frequency in which 100% of the incident sound is absorbed, but it doesn't absorb any more sound above that point since 100% of it was absorbed. If you go to 4" then again, the LF number is pushed down.


A 2" thick panel typically rolls off its absorption starting below 400hz. A 4" panel starts to move that down to 300hz and usually rolls off in a more shallow manner. If rooms tend to have too much absorption at 500hz then you can see that even a 2" panel is absorbing a bit too much. However, none of this changes the fact that pretty much every room in existence does not have nearly enough absorption below 300hz. The plastic helps reduce some of the midrange/midbass absorption and would increase the LF absorption a decent amount potentially. How much depends on the thickness of the fiberglass behind the plastic. That is why I prefer the thicker 2" absorption myself. I also found that once I installed the first 2" absorption material layer on my front wall, the dip at 500hz in the RT60 went away, it flattened out largely, and what remained was a fairly flat curve that rose dramatically below 200hz. In other words, even without the plastic, my room suddenly had a flat curve but without enough LF absorption.


That means you really need to measure because every room could be different. While I added plastic to a portion of the wall, I also added a lot more insulation to sections of the wall to help. I still do not have nearly enough LF absorption and plan to add a bunch more bass traps in the future. I even have a large corner trap that goes floor to ceiling and is 24' across, but that actually did very little.
Just to make sure I'm understanding, for the front wall, are you suggesting 2 layers of 2" with a plastic layer in the middle? Or just two layers of 2"? Again, the builder will be long gone and the room finished before I have a chance to install the sound system and even think about learning how to take measurements. So the idea is to do what can be done while still leaving the option to adjust later with as little additional building work as possible.

Also, with respect to LF, I have been reading about putting A/C vents into the back of my 10 foot long, 16 foot wide, 16" high riser, which will be filled with insulation. I won't know how effective that turns out to be until the room is finished and I install a sound system, of course.

Thanks for all of your help.
GatorBlues is offline  
post #11975 of 11991 Old 09-14-2017, 11:43 AM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by GatorBlues View Post
Just to make sure I'm understanding, for the front wall, are you suggesting 2 layers of 2" with a plastic layer in the middle? Or just two layers of 2"? Again, the builder will be long gone and the room finished before I have a chance to install the sound system and even think about learning how to take measurements. So the idea is to do what can be done while still leaving the option to adjust later with as little additional building work as possible.

Also, with respect to LF, I have been reading about putting A/C vents into the back of my 10 foot long, 16 foot wide, 16" high riser, which will be filled with insulation. I won't know how effective that turns out to be until the room is finished and I install a sound system, of course.

Thanks for all of your help.

2" insulation/plastic/2" insulation is my suggestion. I was just making the point that this isn't guaranteed to be better. You are asking for generic acoustic advice which is akin to asking a tire salesman his opinion on the best tires for your car without telling him what car you have or how you will use it. Even in this analogy, telling a person what car you have tells them a lot about that car because of all the data that is available. Telling me about your room actually doesn't help because I don't have data.


As for LF absorption, yes the riser should provide some LF absorption. For the most part nobody knows how this will work until they have it all setup and done. It is theoretically possible to model the behavior, but most of us don't have access to such software. I've tried to model the behavior but a poor match between my model and reality. Here is what I can say, it makes the most sense to place the vents near boundaries. This is because these are areas of high pressure and where Bass is building up. This would be along the walls, with the corners being the most important area. There is likely to be a Helmholtz resonance from these and I believe that is part of how these operate. The volume of the box is so great that you actually need quite a few vents just to get the resonance up into the 20-30hz range or higher.


I'll just add that these riser bass traps are better than nothing, they help, but I do not consider them significant bass trapping and I have not experienced them contributing significantly. Basically, I don't have them to pull down the LF RT60 values nor do they seem to make huge differences in the LF decay or flatness. No reason not to do it, but you usually still need more.
GatorBlues likes this.
Mpoes12 is online now  
post #11976 of 11991 Old 09-14-2017, 06:51 PM
Advanced Member
 
grendelrt's Avatar
 
Join Date: Jun 2004
Location: Richmond, VA
Posts: 530
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked: 115
Measuring out my ceiling panel, I have 2 ceiling speakers (HTR7000) that are angled drivers for Atmos duty. I am using 1 x 3s to do the framing (so 2.5 in depth actual dimension) and was wondering if there was a guideline of how close I can get to the side of that speaker without interfering with it?
grendelrt is online now  
post #11977 of 11991 Old 09-19-2017, 06:31 PM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by grendelrt View Post
Measuring out my ceiling panel, I have 2 ceiling speakers (HTR7000) that are angled drivers for Atmos duty. I am using 1 x 3s to do the framing (so 2.5 in depth actual dimension) and was wondering if there was a guideline of how close I can get to the side of that speaker without interfering with it?


Can you give more detail. What exactly are you referring to? What is an HTR7000 and what kind of ceiling panels. Do you mean acoustic panels on the ceiling? Is the HTR7000 a speaker and is it an in ceiling that is flush with the ceiling? If that is the case then you should reconsider. If it's anywhere near the speaker it will provide a hard reflective surface and will likely cause a lot of diffraction. Beside impacting the overall sound quality of the speaker it will also play into a mechanism the ear uses to locate sounds. It makes be speakers easier to locate and reduces the seamless pan you would otherwise get.

What I would do if that is the case is build the panels differently. You will want a panel that is open on the sides so sound hitting the sides can be absorbed. You could cut a lot of holes in the frame but it will still cause some diffraction around the edges. You could build a frame using a more open material like metal drywall edging. You could also use thick acoustic foam (which is really just open cell PU foam and wrap that in fabric. If you go this route then don't buy the acoustic foam with patterns or egg crate cut into it. You want a 3-4" thick sheet. It will weigh quite a bit less which is nice and actually absorbs about the same as fiberglass.

Another option could be to mount the speakers flush with the panels by building external boxes for them. That isn't a bad option either. As long as they are flush with the panels it won't cause problems.


Sent from my iPhone using Tapatalk
Mpoes12 is online now  
post #11978 of 11991 Old 09-19-2017, 06:41 PM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by grendelrt View Post
Measuring out my ceiling panel, I have 2 ceiling speakers (HTR7000) that are angled drivers for Atmos duty. I am using 1 x 3s to do the framing (so 2.5 in depth actual dimension) and was wondering if there was a guideline of how close I can get to the side of that speaker without interfering with it?


Can you give more detail. What exactly are you referring to? What is an HTR7000 and what kind of ceiling panels. Do you mean acoustic panels on the ceiling? Is the HTR7000 a speaker and is it an in ceiling that is flush with the ceiling? If that is the case then you should reconsider. If it's anywhere near the speaker it will provide a hard reflective surface and will likely cause a lot of diffraction. Beside impacting the overall sound quality of the speaker it will also play into a mechanism the ear uses to locate sounds. It makes be speakers easier to locate and reduces the seamless pan you would otherwise get.

What I would do if that is the case is build the panels differently. You will want a panel that is open on the sides so sound hitting the sides can be absorbed. You could cut a lot of holes in the frame but it will still cause some diffraction around the edges. You could build a frame using a more open material like metal drywall edging. You could also use thick acoustic foam (which is really just open cell PU foam and wrap that in fabric. If you go this route then don't buy the acoustic foam with patterns or egg crate cut into it. You want a 3-4" thick sheet. It will weigh quite a bit less which is nice and actually absorbs about the same as fiberglass.

Another option could be to mount the speakers flush with the panels by building external boxes for them. That isn't a bad option either. As long as they are flush with the panels it won't cause problems.


Sent from my iPhone using Tapatalk
Mpoes12 is online now  
post #11979 of 11991 Old 09-19-2017, 06:51 PM
Advanced Member
 
grendelrt's Avatar
 
Join Date: Jun 2004
Location: Richmond, VA
Posts: 530
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked: 115
Quote:
Originally Posted by Mpoes12 View Post
Can you give more detail. What exactly are you referring to? What is an HTR7000 and what kind of ceiling panels. Do you mean acoustic panels on the ceiling? Is the HTR7000 a speaker and is it an in ceiling that is flush with the ceiling? If that is the case then you should reconsider. If it's anywhere near the speaker it will provide a hard reflective surface and will likely cause a lot of diffraction. Beside impacting the overall sound quality of the speaker it will also play into a mechanism the ear uses to locate sounds. It makes be speakers easier to locate and reduces the seamless pan you would otherwise get.

What I would do if that is the case is build the panels differently. You will want a panel that is open on the sides so sound hitting the sides can be absorbed. You could cut a lot of holes in the frame but it will still cause some diffraction around the edges. You could build a frame using a more open material like metal drywall edging. You could also use thick acoustic foam (which is really just open cell PU foam and wrap that in fabric. If you go this route then don't buy the acoustic foam with patterns or egg crate cut into it. You want a 3-4" thick sheet. It will weigh quite a bit less which is nice and actually absorbs about the same as fiberglass.

Another option could be to mount the speakers flush with the panels by building external boxes for them. That isn't a bad option either. As long as they are flush with the panels it won't cause problems.


Sent from my iPhone using Tapatalk
Yeah its a flush mount speaker with an angled driver instead of pointing straight down. I've already built the panels now, they are 3" deep. It's looking like the panel side will be about 12 " away from the side of the hole where the speaker is. I just looked up the install guidelines for the speakers and they say to stay 12" from a wall, so I am thinking I will be OK since my panel only extends down 3" vs a wall (fingers crossed).

Last edited by grendelrt; 09-19-2017 at 07:29 PM.
grendelrt is online now  
post #11980 of 11991 Old 09-20-2017, 01:52 AM
Member
 
Join Date: May 2017
Posts: 38
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 4
Absorption layout

Hi, there. Planning HT as a part of living room, which is remodelled from scratch. Based on preliminary research ended up with the following absorption layout. Would appreciate any thoughts and feedback on suggested approach.

Speakers layout: 5.1.4 (with further upgrade to 7.1.4)
Bed layer: on-wall Totem Tribe II/III. Though on-walls (not in-walls), want to mount them flush to absorption surface.
Top layer: in-ceiling Totem Masks

Front wall
AT woven screen and AT fabric panels around
2'' 703 with 2'' gap (can be increased 2''-3'' more if necessary), floor to ceiling across the whole wall

Side wall 1
2'' 703 with 2'' gap, 1'x2' panel

Side wall 2
Nothing as it's far away to the right and will have bookshelves, which will act as absorbers anyway

Back wall
2'' 703 with 2'' gap, floor to ceiling

Corners (bass traps)
4'' 703 with 4'' average (0'' to 8'') air gap, floor to ceiling, 1' wide
Additional corner trap can be introduced between front wall and ceiling

Ceiling and floor
As it's part of the living room, not sure if it can be cured somehow, aside of the thick carpet on the floor in front of the couch.

Material
703 2'' or 4'' thick (depending on application). Shall I introduce FRK/plastic at some places (corners?) ?

Thanks!
Attached Thumbnails
Click image for larger version

Name:	HT Layout (absorption).png
Views:	32
Size:	184.4 KB
ID:	2285300  
OKGeek is online now  
post #11981 of 11991 Old 09-20-2017, 08:07 AM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by OKGeek View Post
Hi, there. Planning HT as a part of living room, which is remodelled from scratch. Based on preliminary research ended up with the following absorption layout. Would appreciate any thoughts and feedback on suggested approach.



Speakers layout: 5.1.4 (with further upgrade to 7.1.4)

Bed layer: on-wall Totem Tribe II/III. Though on-walls (not in-walls), want to mount them flush to absorption surface.

Top layer: in-ceiling Totem Masks



Front wall

AT woven screen and AT fabric panels around

2'' 703 with 2'' gap (can be increased 2''-3'' more if necessary), floor to ceiling across the whole wall



Side wall 1

2'' 703 with 2'' gap, 1'x2' panel



Side wall 2

Nothing as it's far away to the right and will have bookshelves, which will act as absorbers anyway



Back wall

2'' 703 with 2'' gap, floor to ceiling



Corners (bass traps)

4'' 703 with 4'' average (0'' to 8'') air gap, floor to ceiling, 1' wide

Additional corner trap can be introduced between front wall and ceiling



Ceiling and floor

As it's part of the living room, not sure if it can be cured somehow, aside of the thick carpet on the floor in front of the couch.



Material

703 2'' or 4'' thick (depending on application). Shall I introduce FRK/plastic at some places (corners?) ?



Thanks!


I think your plan sounds good. Do you have an ability to take measurements. Without knowing the RT60 values or having real measurements of the effect of the room modes it's hard to give better advice. If the room is highly reflective you may need more panels. If it's got an uneven RT60 plot you may need to use it more strategically or even use 1" panels in places. Measurements would be the best first step before committing. Remember you don't need it fully setup. One relatively full range speaker (bass solid down to 50hz is more than fine) is adequate for this.

Placing 4" 703 sheets across corners does give more bass absorption. Adding FRK will reduce the high frequency absorption and slightly increase LF absorption. This is often good but should be decided again by measurements. Also, when the traps go floor to ceiling it creates a cavity that can resonate. This can make for an uneven absorption with weird peaks and dips. It's causes by trapped standing waves basically. The fix is to break up the chamber with 703. You can either switch to a super chunk style (cut triangles stacked in the corner) or just add a few triangles every so many feet. The two would actually perform very similarly overall.


Sent from my iPhone using Tapatalk
OKGeek likes this.
Mpoes12 is online now  
post #11982 of 11991 Old 09-21-2017, 06:36 AM
Member
 
Join Date: May 2017
Posts: 38
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 4
Quote:
Originally Posted by Mpoes12 View Post
I think your plan sounds good. Do you have an ability to take measurements. Without knowing the RT60 values or having real measurements of the effect of the room modes it's hard to give better advice. If the room is highly reflective you may need more panels. If it's got an uneven RT60 plot you may need to use it more strategically or even use 1" panels in places. Measurements would be the best first step before committing. Remember you don't need it fully setup. One relatively full range speaker (bass solid down to 50hz is more than fine) is adequate for this.
Thanks, man! I didn't think about RT60 uniformity, so it's great you've mentioned that. Currently in design stage, so measurements will be available a bit further along the way. Will definitely post here.


Quote:
Originally Posted by Mpoes12 View Post
Also, when the traps go floor to ceiling it creates a cavity that can resonate. This can make for an uneven absorption with weird peaks and dips. It's causes by trapped standing waves basically. The fix is to break up the chamber with 703. You can either switch to a super chunk style (cut triangles stacked in the corner) or just add a few triangles every so many feet. The two would actually perform very similarly overall.
Awesome. That's for sure was not on my radar. Impression was that the more bass traps I have, the better, but I see, that not all basstraps are created equal
OKGeek is online now  
post #11983 of 11991 Old 09-21-2017, 11:29 AM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by OKGeek View Post
Thanks, man! I didn't think about RT60 uniformity, so it's great you've mentioned that. Currently in design stage, so measurements will be available a bit further along the way. Will definitely post here.




Awesome. That's for sure was not on my radar. Impression was that the more bass traps I have, the better, but I see, that not all basstraps are created equal

RT60 Uniformity is important as a means of understanding the listenability of a room. In more tangible terms, when a room has really good decay in the mid and high frequencies, but poor decay in the bass, a room may have clear dialogue but sound boomy. Conversely, a room with good bass decay but poor mid/high decay may lack speech intelligibility, may have audible echo issues, etc. Notches in the decay can make it sound unnatural. The actual decay of the instruments or recording are already on the recording, so you don't want the room to contribute to that.


I really think that the main reason for keeping the RT60 values over .2 seconds is really more because a room that is too dead is uncomfortable, and the reason to move music rooms above .3 is just because a lot of recordings don't have good "room sound" unless they are a more natural or acoustic recording. It also wouldn't be possible to get bass decay that low and I do think having an even/flat RT60 value over the widest possible frequency range sounds more natural.


In terms of bass trapping, the more the better is mostly true, but certainly not all bass traps are created equally. Corners of rooms are very special places acoustically and need to be treated in very special ways. It's a lot more efficient of acoustic material to simply place 4"-6" panels across a corner instead of chunks, and they actually absorb, overall, very similarly to solid chunk absorbers, however if the material is too thin and doesn't break up all paths that the waves reflect in, you can get a less ideal absorption. Some commercial options have solved this simply by placing "shelves" of acoustic material up the length of the trap at periodic positions.


My main concern with over-use of full range bass traps is the RT60 problem. As an example, the GIK tritrap is nearly flat from 80hz to 250hz in absorption. The Monster bass trap is similarly flat out to 500hz or so. With numerous 4" panels also in the room you can end up with too much absorption at 200hz to 500hz and so its not uncommon to see a notch in the RT60.
OKGeek likes this.
Mpoes12 is online now  
post #11984 of 11991 Old 09-21-2017, 11:51 AM
Member
 
Join Date: May 2017
Posts: 38
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 33 Post(s)
Liked: 4
Quote:
Originally Posted by Mpoes12 View Post
RT60 Uniformity is important as a means of understanding the listenability of a room. In more tangible terms, when a room has really good decay in the mid and high frequencies, but poor decay in the bass, a room may have clear dialogue but sound boomy. Conversely, a room with good bass decay but poor mid/high decay may lack speech intelligibility, may have audible echo issues, etc. Notches in the decay can make it sound unnatural. The actual decay of the instruments or recording are already on the recording, so you don't want the room to contribute to that.


I really think that the main reason for keeping the RT60 values over .2 seconds is really more because a room that is too dead is uncomfortable, and the reason to move music rooms above .3 is just because a lot of recordings don't have good "room sound" unless they are a more natural or acoustic recording. It also wouldn't be possible to get bass decay that low and I do think having an even/flat RT60 value over the widest possible frequency range sounds more natural.


In terms of bass trapping, the more the better is mostly true, but certainly not all bass traps are created equally. Corners of rooms are very special places acoustically and need to be treated in very special ways. It's a lot more efficient of acoustic material to simply place 4"-6" panels across a corner instead of chunks, and they actually absorb, overall, very similarly to solid chunk absorbers, however if the material is too thin and doesn't break up all paths that the waves reflect in, you can get a less ideal absorption. Some commercial options have solved this simply by placing "shelves" of acoustic material up the length of the trap at periodic positions.


My main concern with over-use of full range bass traps is the RT60 problem. As an example, the GIK tritrap is nearly flat from 80hz to 250hz in absorption. The Monster bass trap is similarly flat out to 500hz or so. With numerous 4" panels also in the room you can end up with too much absorption at 200hz to 500hz and so its not uncommon to see a notch in the RT60.
Amazing! Thank you very much for sharing all that!

Sent from my YD201 using Tapatalk
OKGeek is online now  
post #11985 of 11991 Old 09-21-2017, 12:03 PM
Advanced Member
 
grendelrt's Avatar
 
Join Date: Jun 2004
Location: Richmond, VA
Posts: 530
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked: 115
For anyone who has made acoustic panels for their ceiling, I am looking for some examples of a good build. I ran into issues mounting mine with Z clips due to how close the tolerance is on them. I am probably going back to the drawing board and making a couple new panels, but looking for ideas on how to make them to facilitate easy mounting. Currently I am thinking a 1x2 + quater round frame, then adding a spacer below each z clip on the ceiling and panel to give a little extra tolerance. I think doing a fabric wrapped frameless panel with a drywall holder directly into the roxul would be the easiest, but I don't think it would hold up over time. So any one who has done ceiling panels, preferably flush against the ceiling or close to it, please share your build =) Thanks!!
grendelrt is online now  
post #11986 of 11991 Old 09-21-2017, 03:32 PM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by grendelrt View Post
For anyone who has made acoustic panels for their ceiling, I am looking for some examples of a good build. I ran into issues mounting mine with Z clips due to how close the tolerance is on them. I am probably going back to the drawing board and making a couple new panels, but looking for ideas on how to make them to facilitate easy mounting. Currently I am thinking a 1x2 + quater round frame, then adding a spacer below each z clip on the ceiling and panel to give a little extra tolerance. I think doing a fabric wrapped frameless panel with a drywall holder directly into the roxul would be the easiest, but I don't think it would hold up over time. So any one who has done ceiling panels, preferably flush against the ceiling or close to it, please share your build =) Thanks!!


Are you against gluing them to the ceiling?


Sent from my iPhone using Tapatalk
Mpoes12 is online now  
post #11987 of 11991 Old 09-21-2017, 04:00 PM
Advanced Member
 
grendelrt's Avatar
 
Join Date: Jun 2004
Location: Richmond, VA
Posts: 530
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked: 115
Quote:
Originally Posted by Mpoes12 View Post
Are you against gluing them to the ceiling?


Sent from my iPhone using Tapatalk
Hmmm I am guessing that would mean destroying the drywall to get them down.....so probably shouldnt do that, but out of curiosity, how would that work? Would they still be framed?
grendelrt is online now  
post #11988 of 11991 Old 09-21-2017, 04:22 PM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by grendelrt View Post
Hmmm I am guessing that would mean destroying the drywall to get them down.....so probably shouldnt do that, but out of curiosity, how would that work? Would they still be framed?


They certainly could be. There are strong adhesives these days, but no it is better to not frame them. Usually you harden the edges with resin.

It's hard to do what you are asking. I made wooden French cleats for my last build that they slid into but it limited my options so I glued them this time. However I'm using a vicoustic melamine foam and wood panel so the weight is low enough for silicone adhesive which can be peeled off later.

For what it's worth if we are talking 2"-4" panels. Acoustic foam that is solid rather than with a cut pattern has about the same absorption as fiberglass of the same size. The test data for vicoustic cinema panels with fabric cover is nearly identical to the Gik spot panels and both are the same thickness. Foam is known to absorb better for its weight/density than fiberglass which is why it's more widely used in things like aerospace industry where you need the most performance with the least weight. It's biggest problem is that it's significantly more expensive. A 4" thick sheet of PU acoustic foam in a 2x4 size is about $100 or so.

If that opens up options and you don't need that much it may be worth considering.


Sent from my iPhone using Tapatalk
Mpoes12 is online now  
post #11989 of 11991 Old 09-21-2017, 05:12 PM
Advanced Member
 
grendelrt's Avatar
 
Join Date: Jun 2004
Location: Richmond, VA
Posts: 530
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked: 115
Quote:
Originally Posted by Mpoes12 View Post
They certainly could be. There are strong adhesives these days, but no it is better to not frame them. Usually you harden the edges with resin.

It's hard to do what you are asking. I made wooden French cleats for my last build that they slid into but it limited my options so I glued them this time. However I'm using a vicoustic melamine foam and wood panel so the weight is low enough for silicone adhesive which can be peeled off later.

For what it's worth if we are talking 2"-4" panels. Acoustic foam that is solid rather than with a cut pattern has about the same absorption as fiberglass of the same size. The test data for vicoustic cinema panels with fabric cover is nearly identical to the Gik spot panels and both are the same thickness. Foam is known to absorb better for its weight/density than fiberglass which is why it's more widely used in things like aerospace industry where you need the most performance with the least weight. It's biggest problem is that it's significantly more expensive. A 4" thick sheet of PU acoustic foam in a 2x4 size is about $100 or so.

If that opens up options and you don't need that much it may be worth considering.


Sent from my iPhone using Tapatalk
Thanks for the reply, yeah I am doing a 2" panel of Roxul 60 since I already have sheets of it. Right now, I think my only option is wood frame, backer board, Z bars with spacers. I could also make a wood french cleat, did you find those easier than using a z bar type solution?
grendelrt is online now  
post #11990 of 11991 Old 09-21-2017, 07:19 PM
Advanced Member
 
Join Date: Dec 2015
Posts: 695
Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 328 Post(s)
Liked: 158
Quote:
Originally Posted by grendelrt View Post
Thanks for the reply, yeah I am doing a 2" panel of Roxul 60 since I already have sheets of it. Right now, I think my only option is wood frame, backer board, Z bars with spacers. I could also make a wood french cleat, did you find those easier than using a z bar type solution?

Not easier. I was being lazy. I had wood and I didn't have zbar. You could give it a try, it's possible that the wood would work better, I've never bothered to experiment.

I have always found this approach limiting. It's very difficult to mount something that covers most of an area of the ceiling because it needs room to slide into place.

I will be mounting some corner bass trap soffits that I plan to build and was intending to use zbar or a similar cleat. It will run the length of the room so if that works out I'll be sure to take picture of how I did it. I'm looking at other mounting options as well though.


Sent from my iPhone using Tapatalk
Mpoes12 is online now  
post #11991 of 11991 Old 09-21-2017, 08:54 PM
AVS Forum Special Member
 
dnoonie's Avatar
 
Join Date: Jan 2014
Location: Seattle, WA area
Posts: 1,038
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 310 Post(s)
Liked: 268
Quote:
Originally Posted by grendelrt View Post
For anyone who has made acoustic panels for their ceiling, I am looking for some examples of a good build. I ran into issues mounting mine with Z clips due to how close the tolerance is on them. I am probably going back to the drawing board and making a couple new panels, but looking for ideas on how to make them to facilitate easy mounting. Currently I am thinking a 1x2 + quater round frame, then adding a spacer below each z clip on the ceiling and panel to give a little extra tolerance. I think doing a fabric wrapped frameless panel with a drywall holder directly into the roxul would be the easiest, but I don't think it would hold up over time. So any one who has done ceiling panels, preferably flush against the ceiling or close to it, please share your build =) Thanks!!
I've hung my ceiling panels with hooks and eyes connected with zip ties. My wall panels are all hung on a 1" plywood mounting strip, it gives me a good plenum, is more secure since the mounting strip is attached to studs and puts fewer holes in the wall.

Cheers,

OPPO BDP-93, Pioneer Kuro Pro-150FD, Dynaudio 2x BM-12a Mk III Mains, 2x BM 6a Mk II surround, 2x BM 14s Subs, Allan and Heath MixWizard, room is 11'7"x 16'6"x 8" dedicated and treated.
dnoonie is offline  
Sponsored Links
Advertisement
 
Reply Dedicated Theater Design & Construction

Tags
Fv15hp Subwoofer , Denon , Audyssey

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off