Question for bpape or any other knowledgeable Treatment specialists

[Halon451]

Bryan or others, I had briefly discussed some treatment options a long while back with you on this forum, but it's been well over a year now, and suffice it to say, I never got around to doing anything to put up acoustic treatments of any kind. Now I'm back on the trail at last, and come to you again for advice.

I've noticed lately that even though my system sounds great overall, at times, there seems to be a muddying of the mid-bass to higher frequency sounds coming from my center channel speaker that I cannot directly attribute to speaker or receiver inadequacies. From my signature you'll see that I'm running a fairly decent setup with decent speakers and a receiver with plenty of power to drive them. I've noticed this effect primarily during loud explosions in movies, where I get plenty of low-end sound that is "relatively" controlled, but the upper frequency sounds that accompany such scenes (i.e., the crashing, splintering, shattering sound effects) are the ones that are a bit less than desirable. I'm *thinking* that this could be on account of some reflections at the rear wall - where the couch is located, and maybe even some from the wall behind the center channel speaker, albeit to a lesser degree.

I'm the first to admit, I've gotten myself to a point where I understand the system aspects of HT very well, but room acoustics and treatment is still something that I haven't spent a great deal of time on, although most of the concepts and diagrams make sense to me - just need some assistance in my own real-world application to help improve my sound a bit.

Here is a rough draft of my room layout and you can view the photos of my room from the link to my HT below.

Any thoughts are greatly appreciated.

Should be noted that this is an old diagram - the bookshelf in the corner has now been replaced with a potted plant, and the L/R mains are a little further away from the wall and toed in slightly. The sub is positioned a little closer to the Left Main than depicted:

Here is an older pic of the rear wall - as you can see, space constraints limit me to basically shoving the couch right up against the wall.

Newest pics (poor quality..sorry) - showing the front three and new sub position (which is now perched atop a Gramma isolation pad - not shown). Also have hardwood flooring which replaced the carpet in the old pics, and I'm sure that didn't help me acoustically, but it made the wife a lot happier.

Also, the center channel speaker is tilted slightly upward so that the tweeter is in direct line with the ears of whoever sits on the couch.

 

[Halon451]

I meant to say this as well - not only for the sake of correcting the 'muddying' effect I'm getting, but any and all treatment options in general are most definitely welcomed. Would need to keep WAF high obviously, so decorative panels are ideal, but probably way out of my budget for this kind of stuff. I'm good with my hands, so DIY is definitely an option, but would need some help in finding correct materials, and where these are usually obtained.

Thanks again guys

 

[jostenmeat]

I meant to say this as well - not only for the sake of correcting the 'muddying' effect I'm getting, but any and all treatment options in general are most definitely welcomed.

I think your candidates for placement are very good. From what I have gleaned over the last couple of years, the back wall would be of great priority, because you're right up against it. Bass collects there, muddying your FR, masking other frequencies. Some experts would say to LOAD with massive broadband treatments there.

BTW, if it was me, I'd experiment with center speaker by pulling it closer to lip of cabinet, away from the wall some more.

Would need to keep WAF high obviously, so decorative panels are ideal, but probably way out of my budget for this kind of stuff. I'm good with my hands, so DIY is definitely an option, but would need some help in finding correct materials, and where these are usually obtained.

DIY-made-easier: Chameleon Bass Traps (that I originally learned about from WmAx, and that's what he uses IIRC).

http://www.readyacoustics.com/index.php?main_page=product_info&products_id=2&zenid=cbbb86a16d3bcfd93911c5557946899c

For fabrics, they offer a selection, but here are other vendors. If you want to find your own, some use cotton muslin, some use burlap, and the common recommendation for DIY-art is to use Ritt dye, since paint is reflective.

Some vendors to check out for covering fabric:
http://www.studio-acoustic-solutions.com/fr701.html
http://www.atsacoustics.com/cat--Fabric--107.html
http://www.acousticalsolutions.com/fabrics
http://www.acoustex.com/Home.html

 

[Halon451]

I think your candidates for placement are very good. From what I have gleaned over the last couple of years, the back wall would be of great priority, because you're right up against it. Bass collects there, muddying your FR, masking other frequencies. Some experts would say to LOAD with massive broadband treatments there.

Okay, here is where things start to get a little confusing for me - I've read several threads pertaining to the use of various materials, which is better suited for lower frequencies, which is better suited for higher freq reflections, absorption factors, hell - which type is easier to cut and mold even, so I'm afraid I would be at a loss in deciding which application to use without some guidance.

Thanks jostenmeat, I'll take a look at those links. In your opinion though, that rear wall is definitely a good place to start, eh?

 

[jostenmeat]

Okay, here is where things start to get a little confusing for me - I've read several threads pertaining to the use of various materials, which is better suited for lower frequencies, which is better suited for higher freq reflections, absorption factors, hell - which type is easier to cut and mold even, so I'm afraid I would be at a loss in deciding which application to use without some guidance.

Fiberglass is easier to work with. Dialing down higher frequencies is easier. Dialing down lower frequencies will be a function of thickness/mass. You can actually dial down lower frequencies, yet help minimize HF absorption by the covering itself, by making it more reflective for the HF. The most common material seems to be OC 703. If you have a higher budget, 705 may be more desirable for its density. Considerably more expensive though. Mineral wool will be significantly cheaper, but significantly more difficult to work with by most accounts. Some people still use it though.

http://www.ethanwiner.com/density.html

What you can do in the meanwhile is run some test tones to see which frequency range seems to be the most offensive. Armed with that knowledge, the experts can better help you.

Thanks jostenmeat, I'll take a look at those links. In your opinion though, that rear wall is definitely a good place to start, eh?

Yes. Remember the first pic I posted in the Spaniard's thread? That set actually belongs to Glenn Kuras, owner of GIK.

However, you can simply just play around, and add to taste. Even Savant here, the "resident acoustics expert", would tell you the same thing.

 

[Halon451]

...yet help minimize HF absorption by the covering itself, by making it more reflective for the HF...

This part was confusing - did you mean to say minimize 'reflection'... making it more 'absorptive'? I thought the point with treatments was to minimize reflections to the extent possible - those second and third order reflections that cause peaks and valleys in the FR. Or maybe I misunderstood your point. I also do understand a certain amount of reflection is necessary - having a HT system in an anechoic chamber is neither practical, nor desired, but I'm just now starting to get my head around this aspect of it. Better late than never

 

[jostenmeat]

This part was confusing - did you mean to say minimize 'reflection'... making it more 'absorptive'?

No, I meant what I typed. I offered that in case you wanted to dial down ONLY lower frequencies, leaving other frequencies alone, as much as possible (because any panels you put up will still most likely absorb some HF).

I thought the point with treatments was to minimize reflections to the extent possible - those second and third order reflections that cause peaks and valleys in the FR.

Yes, at my place, I got very large absorbers that are actually designed for even greater HF absorption, yet are large because I wanted bass absorption too!

Or maybe I misunderstood your point. I also do understand a certain amount of reflection is necessary - having a HT system in an anechoic chamber is neither practical, nor desired, but I'm just now starting to get my head around this aspect of it. Better late than never

Yeah. Play, add to taste. On one hand, a few people don't like any absorption, criticizing other critically treated systems as anechoic chambers as you say. Then you have some experts and professionals that use on the order of 50+ panels in their room. They might tell you there is treated, and then there is treated. Ethan Winer has said on multiple occasions that going overkill with bass trapping is virtually impossible.

 

[Halon451]

Okay, second question to the previous - where do I find readily available Owens Corning 703 or 705? Are these panels usually available at the Home Depot/Lowe's type places, or do I have to special order them? I think I could get by with some of these, and build a decent frame for them, cover it with some decorative fabric from JoAnn's or similar and keep the costs of this project within some kind of reasonable limits.

 

[jostenmeat]

You'll have to call around. I have a friend who found a TON of fiberglass (maybe even literally!) to do up his entire band practice room in the backyard of his home. I don't think it was OC, but he did staggered studs, etc.

Read nibhaz's post here for some more insight, and a good video.
http://forums.audioholics.com/forums/showpost.php?p=660883&postcount=135

In fact, if you go bother nibhaz, he might take some effort in finding some for you if he has free time. Of course, you'll have to let him know the area where you live. edit: nm, you live in Tampa, heh.

 

[Halon451]

You'll have to call around. I have a friend who found a TON of fiberglass (maybe even literally!) to do up his entire band practice room in the backyard of his home. I don't think it was OC, but he did staggered studs, etc.

Trolling construction sites perhaps... Just kidding. I'll do some digging around as well, now that I know what I'm looking for. At any rate, I certainly appreciate the insight JM. It's been a terrific help.

 

[bpape]

Wow. I don't check in for a few hours and a flurry of activity!

Just my 2 cents:

Front left corner as much broadband as thick as you can.

Something about 4" or more thick on the wall behind the seating

2-4" directly behind the mains on the front wall for boundary effects.

OC703 or equivalent will be fine for all of those applications if you want to DIY. If you have a hard time finding 703, PM me.

Bryan

 

[Halon451]

Thanks a ton for the suggestions Bryan. That front left corner is indeed a sore spot, I don't even need to measure room response with a meter to know that -merely walking in that direction with the sub firing is like walking into a giant timpani drum. With only a few inches to spare between corner and window though, I've been at a loss as to how to integrate a bass trap solution that isn't going to be an eyesore.

The rest of the info is definitely reasonable. Will PM about the OC703/705.

Thanks again!

 

[nibhaz]

Halon,

I started to do some research for deep bass absorptions, which means I started looking up SCA builds. Now after taking a closer look at your drawing and pictures I see that I’ve wasted some time, but I’ll post what I’ve found anyways, just to get your creative thoughts rolling.

I’m 99% sure this thread belongs to an audioholics member, but I can’t recall there screen name here.

This thread is good, because it shows that good absorption can be built along the vertical corner between the wall and ceiling. The second and last pictures are the most valuable to my point.


You could possibly build a smaller SCA style absorber in that front left corner, if there is enough room between the corner and window.

If you were to use the cut pattern on the far left, you would only need a little over 1’ corner to window gap, and it would only take 3 X 2” thick panels to produce 8 linear feet of absorber.

However, I would speculate that you could achieve much better low end abortion if you were to build 4” or 6” thick panels and then stacked them in the corner at an acute angle to the corner. The key to this method would be ensuring that the sides of the panels make contact with the room boundaries. This method would utilize 4 to 6 panels for 8 linear feet of absorber.

Beyond the corner, here are some things to keep in mind while planning your build.

1.Thicker generally means better low end absorption​

2.Air gaps behind a panel increase its low end absorption. In other words, a 2” panel with a 2” gap, performs almost as well as a 4” panel with no gap, but uses half the material.​

3.The thicker the panel the less dense the material you should use. (technically lower gas resistivity), especially when considering the price vs. performance ratio.​

I would consider using the Porous absorber calculator to plan your build. Keep in mind that it shows a single angle of incident, so play with that value to get a better idea of in room performance.

Ballpark gas flow values for OC products:
701: 8,300 rayls
703: 16,500 rayls
705: 30,000 rayls

 

[Halon451]

This is now officially going to be fun. My engineering instincts are already perking up at the prospects! Eh, due to other issues on the home front last night, I didn't get a chance to measure the distance between the window gap and the front left corner in question like I had intended but will tonight. It would be so much easier if home developers and architects put a little thought into their living rooms with respect to HT planning

Anyhoo.. as far as those cut patterns go, I'm very sure without even measuring that I'm way under the one foot mark, therefore by my reasoning, in order to have roughly the same volume of absorption material I would have to cut and measure a narrow angle from the facing wall that extends further out on that side than it does between corner and window. It would not place the face of the material at a nice 45 degree angle, but I don't know if that matters or not.. ? Not to mention - looks and aesthetics again. Always a factor.

Question for anyone in general: As bpape suggested, placing a panel behind each main speaker up front (which I had already pretty much counted on having to do), but any thoughts as to placing a much smaller panel of the same material behind the center speaker? Would that make any significant differences?

 

[jostenmeat]

It would not place the face of the material at a nice 45 degree angle, but I don't know if that matters or not.. ? Not to mention - looks and aesthetics again. Always a factor.

It will matter, maybe only a very tiny bit, maybe more, but the fact that you are even addressing this spot with large amounts of broadband absorption is good already. IOW, if you are asking, "Is it still worth it to do this?", then we are certainly going to say yes.

Question for anyone in general: As bpape suggested, placing a panel behind each main speaker up front (which I had already pretty much counted on having to do), but any thoughts as to placing a much smaller panel of the same material behind the center speaker? Would that make any significant differences?

Probably. However, I am led to believe that just as good of a candidate is the cabinet top itself. Now, I know . . . doing either of them is a matter of pulling off something that looks decent.

My center speaker actually sits on top of a OC 705 panel. The speaker weighs 25 lbs, it's no problem.

 

[Halon451]

It will matter, maybe only a very tiny bit, maybe more, but the fact that you are even addressing this spot with large amounts of broadband absorption is good already. IOW, if you are asking, "Is it still worth it to do this?", then we are certainly going to say yes.



Probably. However, I am led to believe that just as good of a candidate is the cabinet top itself. Now, I know . . . doing either of them is a matter of pulling off something that looks decent.

My center speaker actually sits on top of a OC 705 panel. The speaker weighs 25 lbs, it's no problem.

Yes, looking decent is paramount. If I were to come up with a design that fits the space, I would probably look at fabric coverings that would closely match the surrounding wall paint, or at least come close enough to it - make it blend in a little more. I'm going to keep options open for that corner for now and concentrate on the other areas until I get a little more comfortable with the building process. At least the area behind the couch - I can find some decent fabric with a design on it that would make it look good hanging on the wall, same with the area behind each main speaker. I could probably just custom cut a piece of 703 or 705 for the center channel's wooden base, wrap it in black fabric and have a bit of isolation between speaker and cabinet. I'm guessing this was your intention with your center - more of a decoupling thing than absorption?

 

[jostenmeat]

I'm guessing this was your intention with your center - more of a decoupling thing than absorption?

No, mostly absorption. My center speaker is very close to floor, which creates midbass boosts, which in turn will mask dialogue. I have 80 lbs of treatments just for the floor. I have thought about going with scope dimensions (just use a hook to stop screen) if only for better center placement. However, this is a dedicated HT, and as much time I've spent learning about audio, video is still sort of king (even if the audio stuff cost so much more as a collective whole). No one I've asked among guests/friends/family gives me the go ahead to reduce screen size for audio's sake. On one hand, as you know, not many people know what even half way decent audio in a home sounds like. Also, the good number of absorbers + Audyssey MultEQ XT have done quite a bit for me. I also have tried to make sure I have good space from the front wall to the front three speakers.

I have corner traps in three corners, as well reflections treated on sidewalls. I suspect the one place that needs most consideration by myself is the ceiling at this point. Most treatments are covered by thick curtaining. My front corner traps are not at 45 degrees, but significantly less, still with angle, and they still help.

I have a separate stereo in the LR. I've massively treated the front wall, and have a very large 30 lbs treatment I prop on the couch back on the sidewall, in my asymmetrical room for critical listening.

 

[Halon451]

If I was doing a dedicated HT room, I could obviously afford to take a different approach with regards to sound treatments and build them into the structure of the room, etc. As it is, this is my living room, so I'm going to be limited in what I can apply and where. But my whole mindset going into this, is something is better than nothing at all, and I'm ready to take that step - can always add to it later if I figure out better ways to blend it in with the decor and aesthetic of the room.

 

[nibhaz]

Question for anyone in general: As bpape suggested, placing a panel behind each main speaker up front (which I had already pretty much counted on having to do), but any thoughts as to placing a much smaller panel of the same material behind the center speaker? Would that make any significant differences?

Rob,

If you are going to place panels behind your speakers you’ll need to make sure that they are of sufficient thickness. Personally, I’d suggest 4” thick with 2” gap, if you can get away with it. The reason being is that, speakers don’t start to radiate in a rearward direction until the lower frequency ranges, so the panel needs to be effective in this range.

I think it would be useful to place a similarly thick panel, horizontally behind your center channel. It looks like a 1’ x 4’ x 4” panel would fit nicely under your display.

It will matter, maybe only a very tiny bit, maybe more, but the fact that you are even addressing this spot with large amounts of broadband absorption is good already. IOW, if you are asking, "Is it still worth it to do this?", then we are certainly going to say yes.

+1 QFT

Yes, looking decent is paramount. If I were to come up with a design that fits the space, I would probably look at fabric coverings that would closely match the surrounding wall paint, or at least come close enough to it - make it blend in a little more. I'm going to keep options open for that corner for now and concentrate on the other areas until I get a little more comfortable with the building process. At least the area behind the couch - I can find some decent fabric with a design on it that would make it look good hanging on the wall, same with the area behind each main speaker. I could probably just custom cut a piece of 703 or 705 for the center channel's wooden base, wrap it in black fabric and have a bit of isolation between speaker and cabinet. I'm guessing this was your intention with your center - more of a decoupling thing than absorption?

If customization and looks are paramount I have three words for you: Dye-sublimation printing.

Sometimes referred to as sub-dye printing. You can have any image you can imagine printed on a fabric, without compromising the fabric’s breathability. I imagine Tampa has decent conference business, so it’s highly likely that you’d be able to find a local print shop with this technology.

Also, the good number of absorbers + Audyssey MultEQ XT have done quite a bit for me. I also have tried to make sure I have good space from the front wall to the front three speakers.

This has been my experience as well, despite what some detractors have to say about Audyssey.

I have corner traps in three corners, as well reflections treated on sidewalls. I suspect the one place that needs most consideration by myself is the ceiling at this point. Most treatments are covered by thick curtaining. My front corner traps are not at 45 degrees, but significantly less, still with angle, and they still help.

I wouldn’t fret the corner panel’s positioning at all

Do you have a drop ceiling with acoustic tiles?

 

[Halon451]

If you are going to place panels behind your speakers you’ll need to make sure that they are of sufficient thickness. Personally, I’d suggest 4” thick with 2” gap, if you can get away with it. The reason being is that, speakers don’t start to radiate in a rearward direction until the lower frequency ranges, so the panel needs to be effective in this range.

At what frequency are we talking here? My little SVS's only dig down to about 65Hz, plus they're crossed over to the sub at 80 as it is. Oh, well I should note that by the end of this week the SBS-01's are going to be replaced with matching SCS-01(M)'s, not that this is going to make a huge difference in this regard.