[madfloyd]

I have a 14 x 25 x 7.5 room.   Soundproofed with ASC wall damp system (walls/ceiling), heavy exterior doors etc.   Wall to wall thick shag carpet.

I had ASC wall planks all over the side walls, but I've removed them.   I have RealTraps for bass.

Problem is music sounds dull and lifeless.  I have 4 sets of speakers (Aerial Model 9s, Salk SongTowers, JM Labs Micro Utopias, Focal 1007 BE, the latter combined with JL Audio F113 subwoofers).   I have good electronics, have swapped everything I could think of to eliminate a weak link somewhere (which is why I have mutiple pairs of speakers).  I've played with speaker placement. I now believe it's the room.

I have an 11' wide screen on the front wall (room doubles as a home theater).  The screen is 8" out from the front wall (built out on 2x4 frame).  I imagine this screen is reflective, not absorptive.   

What can I do?   I can't remove the carpet and can't figure out what the heck is making everything sound so dark.  I don't hear 'air' very well at all, vocals are recessed, harmonies are hard to pick apart, etc.

I'm wondering if adding diffusion would help liven it up - but I know there can be downsides to that as well.

Any tips or advice appreciated.

Thanks in advance.

[WGH]

Many speaker designs incorporate a rear facing ambience tweeter to add openness and air to the sound. My own speakers have an adjustable ambience tweeter and I like what it does since my room is also fairly dead.

VMPS recently added an ambience tweeter to their catalog. It looks like something to check out for not much cash and a pair costs much less than any room treatment.
http://www.audiocircle.com/index.php?topic=51181.0

Wayne

[richidoo]

My .02... fwiw, etc... Because you say the midrange sounds confused while the electronics all check out and not too much absorbtion leads me to point blame toward that big vinyl screen hanging between the speakers. It reflects crucial ambience cues from the front wall from getting to you, but it is not 100% soundproof and what does get through will be distorted in eq and phase, screwing up the direct sound. Can you get that screen out of there temporarily to see if that helps? WEEZ (God rest his soul) used to say nothing should go between the speakers. In my experience stuff in between and also especially close to the speakers usually screws things up- especially a gigantic vinyl sound barrier.

Is the screen out far because it is so wide it won't fit behind the speakers? The speakers should be in front of the plane of the screen. Maybe a smaller screen could allow mounting on the front wall without speakers blocking the view.  If you can't move it you can probably treat the area behind it to stop the reflections from getting through and bouncing around behind, but your soundstaging won't reach the potential with the screen out in front of the speakers.

With the walls and ceiling just sheetrock, you should be getting enough reverb. The carpet is fine if the ceiling is hard or diffuse. Realtraps have a mask that prevents absorbing too much higher freqs. Drape a paper bag or cardboard over them to prove to yourself that they are not too absorptive.

Try bringing in a boombox or portable to see how it sounds in different positions - in front of the screen, at the speaker position, behind the screen, etc. You might discover a pattern that makes sense.
Good luck!
Rich

[TONEPUB]

Im in agreement with RD about trying to keep everything from the
space between the speakers....

That might just be the biggest problem.

Also, where's your couch, what's it's proximity to the rear wall
and what's the rear wall like in terms of surface?

[madfloyd]

The speakers are about 5' out from the front wall while the screen is only 8" so it's not like the screen is right in between the speakers.

I sit about 12.5 - 13' from the front wall - so I'm roughly 8' from the speakers and about 12' from rear wall.   The rear wall is mostly untreated; there is a doorway, small recessed cavity that houses 2 equipment racks.  What remaining surface (not that much) is untreated.  I can't move my sitting position further back because there is a riser with 2nd row of seating.

I can, with some effort, get the screen out. I've been thinking I ought to try that.

[Ethan Winer]

an't figure out what the heck is making everything sound so dark.

Since you're a RealTraps customer, you could send us a couple of photos so we can see your room and give you more personal advice. I'm sure there are very easy solutions for this.

--Ethan

[richidoo]

I coulda sworn that the IP said 8', not 8"...   

Woulda been an easy answer if it really was 8'   

[James Romeyn]

I have a 14 x 25 x 7.5 room.   Soundproofed with ASC wall damp system (walls/ceiling), heavy exterior doors etc.   Wall to wall thick shag carpet.

I had ASC wall planks all over the side walls, but I've removed them.   I have RealTraps for bass.

Problem is music sounds dull and lifeless.  I have 4 sets of speakers (Aerial Model 9s, Salk SongTowers, JM Labs Micro Utopias, Focal 1007 BE, the latter combined with JL Audio F113 subwoofers).   I have good electronics, have swapped everything I could think of to eliminate a weak link somewhere (which is why I have mutiple pairs of speakers).  I've played with speaker placement. I now believe it's the room.

I have an 11' wide screen on the front wall (room doubles as a home theater).  The screen is 8" out from the front wall (built out on 2x4 frame).  I imagine this screen is reflective, not absorptive.   

What can I do?   I can't remove the carpet and can't figure out what the heck is making everything sound so dark.  I don't hear 'air' very well at all, vocals are recessed, harmonies are hard to pick apart, etc.

I'm wondering if adding diffusion would help liven it up - but I know there can be downsides to that as well.

Any tips or advice appreciated.

Thanks in advance.

My room's dimensions are similar to yours: 16-7 x 25-9 x 7-7.  Does anything in your entire system invert polarity?  If so or if not absolutely sure, do try inverting both speaker polarities.  Though unlikely to the degree stated, your symptom could be consistent w/ inverted absolute polarity.

Absorption down as low as 200-150 Hz is OK as long as it's not overdone (overdone is purely subjective).  If you are employing absorption that is effective well below 150 Hz (requires a LOT of OC703), recent personal experience is that such will absolutely detract from sound quality & cause the stated sympton.  This is personal experience after installing about 50 sheets of OC703 in a professionally designed full-circumference acoustic soffit in my last room to flatten bass modes; equivalent ASC value is $8k.  This is well beyond theory for me. 

IMO the single biggest difference between live music & reproduced is the way small (meaning any domestic) room behaves below 200 Hz vs. large commercial spaces.  Achieving in a small room the bass performance of large rooms exceeds every prior known improvement whether components, speakers or accessories.  Reflectivity in the bass range is absolutely critical in achieving the intended performance level; absorption in the bass range is absolutely verbotten.  This goes against all or most intuition yet it turns out to be true in my personal experience.  Your stated symptom is very consistent w/ what I experienced in my last room filled w/ OC703.

If bass modes are a concern there are a couple different subwoofer-based solutions I could offer, none involve the use of EQ to flatten modes (never recommended).  But no matter what, the more a room employs absorption to flatten bass modes (applies ONLY to absorption below 200 Hz; absorption above 200 Hz does NOT count) the worse, the dryer, the more artificial & lifeless it will sound.  Yes, bass modes may be flattened (bath water tossed) but the baby goes w/ it.  The only way to cure the defect is to remove the bass absorption to return the room's original reflective quality; bass modes must be flattened in another fashion.  I did not have to remove my w-w medium pile carpet & medium-thick pad to achieve appropriate reflectivity.  Considering the quantity of OC703 required for bass absorptoin the carpet/pad appear to offer little to no absorption below 200 Hz.  Maybe someone else can post coefficients of absorption vs. frequency for med. carpet& pad over slab.  I still employ a small to moderate amount of selectively placed absorption at higher frequencies. 
     

       

[madfloyd]

Ethan: Thanks for the offer, I will take a few photos and send them to you tomorrow.

ro7939:  What is OC703?

[JackD201]

My suspicion is the thick shag wall to wall carpet. Too bad it's on the "no touch" list. 

Here's why I suspect it to be so. These are the absorption coefficients for heavy carpet on concrete or with standard backing. Shag should be worse. Note that the presence frequencies lie between 4kHz and 6kHz hence the bold strike on the 4kHz figures. Your carpet is absorbing more than half the energy of the surface incidence at any given point.

                              125Hz     250Hz   500Hz    1kHz     2kHz    4kHz
Heavy Carpet on slab   .02       .06        .14        .37       .60     .65
On foam rubber           .08       .24        .57        .69       .71     .73

[bpape]

Just a guess - but my thought is that with the stiff walls, you've now got a lot more bass buildup and ringing in the room which is masking a lot of the other information.  You mentioned you had some of Ethans traps but don't say how many. 

Bryan

[James Romeyn]

Ethan: Thanks for the offer, I will take a few photos and send them to you tomorrow.

ro7939:  What is OC703?

OC703 is Owen's Corning's title for rigid fiberglass panels, 2" x 2' x 4', sold in packs of 12 at specialty commercial insulation suppliers.  Someone recently posted they purchased 3" thickness but that's all I know about 3".  It's one of the most common materials employed for absorption/modification of audible waveforms, esp in the bass range. 

There is proven, specific multiple woofer methodology that minimizes bass modes w/o EQ, w/o mechanical absorption & maintaining all the room's natural reflectivity in the bass range (as mentioned, vital to proper reproduction).  Beyond that the only other method I know of to absorb bass waves & bass modes is a Helmholtz resonator: large, cumbersome & tuned to a narrow bandwidth.  EQ of any kind simply moves a room's mode from one location in physical space to another (sometimes w/ worse effects), making it an inferior mode cancelling device. 

Your 7.5' ceiling is scary close to 1/2 the 14' wall.  Put your room dimensions into Ethan's wonderful room calculator (thanks Ethan!) & be prepared for a surprise.  I'm pretty sure your room has worse modal effects than mine, & mine was so bad (till installing the specialty multi-woofer system) that powerful bass below 50 Hz was unlistenable (new solid construction, slab floor & front wall, rigid & w/ little flex to absorb modes).      

[madfloyd]

My room width was actually 15' wide, but because it would have been a multiple of the ceiling height, I shortened the width to 14'.

[madfloyd]

Sent pics to Ethan (via James' email - only email address I saw on the site).

[Ethan Winer]

Sent pics to Ethan (via James' email - only email address I saw on the site).

Yes, that's the correct address. Jim is the go-to guy for customer service, and he knows as much as me about this stuff.

--Ethan

[Ethan Winer]

Sorry, I must have missed this the first time around:

If you are employing absorption that is effective well below 150 Hz ... will absolutely detract from sound quality & cause the stated sympton.  This is personal experience after installing about 50 sheets of OC703

It is not possible to have too much bass trapping in a small room. Indeed, that is the single best way to get a small room to behave more like a large room. However, it's definitely possible to have too much absorption at mid and high frequencies, and your 50 sheets of 703 is proof of that. Since you made your own treatments, my best advice is to cover portions of the 703 with thin card stock or thin plastic or similar. This will retain all the bass trapping which you do want, but add back some life at mid and high frequencies. The best traps to cover are those straddling or near corners, and anywhere else out of the way of direct reflections.

--Ethan

[James Romeyn]

Sorry, I must have missed this the first time around:

If you are employing absorption that is effective well below 150 Hz ... will absolutely detract from sound quality & cause the stated sympton.  This is personal experience after installing about 50 sheets of OC703

It is not possible to have too much bass trapping in a small room. Indeed, that is the single best way to get a small room to behave more like a large room. However, it's definitely possible to have too much absorption at mid and high frequencies, and your 50 sheets of 703 is proof of that. Since you made your own treatments, my best advice is to cover portions of the 703 with thin card stock or thin plastic or similar. This will retain all the bass trapping which you do want, but add back some life at mid and high frequencies. The best traps to cover are those straddling or near corners, and anywhere else out of the way of direct reflections.

--Ethan

my best advice is to cover portions of the 703 with thin card stock or thin plastic or similar.

Thanks for the advice but it was already in the design.  The outer surface of the OC703 was treated & was fully reflective.  I'm quite sure I mentioned it was professionally designed.  I wasn't about to spend that much money experimenting.  The fact that performance improved (so very dramatically) by flattening the modes w/o bass absorption, rather "proves" that bass absorption degrades performance.      

I now believe a specific multi-sub approach is infinitely more preferred & the less bass absorption the better (none is the goal).     
 

...bass trapping...is the single best way to get a small room to behave more like a large room.

  Is it true that the sum total reason for bass absorption is to flatten modes?  If yes, if bass absorption minimizes reflectivity (obviously "absorptive" & "reflective" are opposites) & if large rooms are reflective in the bass range, one must then prove that reflectivity in the bass range is unrelated to sound quality.  I would suggest readers visit a large commercial space, listen attentively to how the bass sounds relative to the rest of the spectrum, then go home & listen, esp if you have a lot of bass absorption. 

Welti & Dr. Earl Geddes are the prime promoters of the mult-sub approach (their solutions to flatten modes have some differences but more similarities).  As far as I know neither profits from their stated methodology.  Any amount of absorption effective down into the bass range detracts from performance when compared to the modes being flattened in the alternative suggested method.  The more bass absorption, the more (overly) dry, synthetic & amusical & the less will a "small" (meaning domestic) room sound like a large commercial space. 

The expansive quality to the sound in large rooms is because the modes are totally subsonic (they exist but are inaudible) & because large rooms are highly reflective in the bass range (the acoustic devices you see on the walls are ineffective below 150-200 Hz).  Saying something is "not possible" when one has not personally auditioned the suggested option/alternative is bad practice IMO, w/ all due respect.  DIYaudio.com & other forums have many posts on the subject.  Here's one link:  http://www.diyaudio.com/forums/showthread.php?s=&threadid=134568&perpage=25&pagenumber=2  IMO within a few years the use of bass absorption will be largely a thing of the past.  The difference is that great.  I suggest adherents & promoters of bass absorption research the multi-sub approach, test it & see if there are scientific holes.  So far I've seen none & rather the science backs it up.   

Do large rooms have bass traps?  Do large rooms have "absorption" effective below 150-200Hz?  The sum total reason for the existence of bass absorption is to flatten modes.  A more effective method to flatten modes is one that maintains all the room's natural reflectivity in the bass range.  Such a method is proven to exist.  The reflective quality in the bass range is a prime hallmark of the single greatest difference in listening quality between large rooms & small rooms treated w/ bass absorption.         

The described multiple sub method to flatten bass modes (there's are several fine points beyond the quantity of subs) indeed requires significantly less absorption overall & no absorption effective below 150 Hz.  But rooms do still benefit from selective apsorption & diffusion above 150-200 Hz.  Plus, once the bass modes are flattened & the room's natural reflectivity is present, the single greatest detriment to sound quality is solved (IMHO greater than any speaker or component improvement unless your room has virtually no modes).  Getting the bass right can only improve the effectiveness of room tuning above 200 Hz. 

[bpape]

Large room acoustics is a completely different topic than small room acoustics.  In large rooms, you want to encourage the bass field to propogate.  Modal issues do not come into play nearly as much since the room dimensions are generally larger than the longest wavelengths being produced.

Also, large spaces inherently have a large amount of bass control built in - it's called an audience.  Human bodies are excellent bass absorbers.  Put a few hundred or a few thousand in a space and effectively, the entire floor of the space is one huge bass absorber.

Treating the bass in a small room is not only for dealing with frequency response issues, but also to bring relative decay times into line.  Most small rooms have very little bass control and a large amount of square footage of upper mid and high frequency absorption (carpet, curtains, furniture, etc.) so the decay time becomes skewed.  Installing broadband bass control balances things out.

Bryan

[youngho]

Jimbo, I think it's important to note:

1. There are different kinds of bass absorption. For example, fiberglass panels are primarily resistive absorbers. Other options include panel/diaphragmatic absorbers, Helmholtz absorbers, and active absorbers. Unfortunately, resistive absorption is most effective at areas of maximal particle velocity, but it is usually placed near areas of maximal pressure fluctuations (which are the areas of lowest particle velocity). Thus, the absorption through resistance is increased when pulled away from the room boundaries to create an air gap. Often, a limp mass membrane is added to the fiberglass to make it less purely resistive.

2. Geddes calls for "a large amount of sound absorption at low frequencies" with "as little absorption at higher frequencies as we can reason-
ably get away with." This is cleaerly spelled out in chapter 4 of the online portion of his book on home theater at http://www.gedlee.com/downloads/Chapter%204.pdf. The primary method he suggests is through using the room boundaries themselves during the construction phase by mounting the drywall in such a way that it "flexes" as much as possible in order to flatten and widen modal resonances. However, I believe that diaphragmatic absorbers like the RPG Modex Plate would probably be an acceptable substitute in already constructed rooms. In any case, it's important to note that the purpose of bass absorption is not only to flatten the resonant peaks. It will also widen the peaks and incidentally also boost nulls (side benefit of reducing standing waves).

3. Floyd Toole, who was Todd Welti's former "boss" at Harman, also suggests that "damping of room modes is advised" in his book "Sound Reproduction." He discusses the types of bass absorption in #1 and seems to favor membrane/diaphragmatic and Helmholtz over resistive absorbers. He also writes that it's desirable "to attenuate and broaden the resonant peaks."

4. Welti does work for Harman, and JBL does make a device called Bass Pro that incorporates the Sound Field Management approach. His general approach does seem to rely on a significant amount of equalization (look at the results from the investigation where equalization was not used in the original white paper on multiple subwoofers). However, many of the take home messages are free.

5. The modes in large rooms are not subsonic or inaudible; they are actually key to making large rooms sound like large rooms when it comes to the bass region. Rather, the modes are distributed very differently from small rooms. There is a fascinating ongoing discussion of spatial bass in the AVS forums (http://www.avsforum.com/avs-vb/showthread.php?t=1113793). Both Geddes and Welti are participating, as they both are also in the discussion on multiple subwoofers at http://www.diyaudio.com/forums/showthread.php?s=&postid=1733281#post1733281 (Welti joins in later in the discussion). I should note that Dennis Erskine disagrees with both Geddes and Toole about the use of room boundaries as bass absorbers.

Bryan, the numbers in Everest's Handbook suggest that human beings are excellent midrange but not bass absorbers, although their bass absorption does improve with more formal attire and upholstered seats. Toole also presents a seat absorption graph suggesting to me that a large part of the effect below 1 KHz may be due to the seats themselves.

[JackD201]

I'm confused. Madfloyd wants more midrange and upper octave energy and the discussion went to bass absorption. Is the approach suggested then to sap off the contrast frequencies so as to give the presence region more prominence? Hey that works too but IMO is rather counter intuitive. Such an approach creates higher power demands on the gear to attain the same SPL.