[andycsb]

Hi Guys,

Placed 2 2'x4' foam (4 inch thick) panels on the center front wall over the weekend.  It did not sound good. Focus improved but overall SQ esp on female vocals sounded dry with a definite increase in sibilance. I have since removed them.

Thinking of QRD diffusers now. Maybe a 2'x2' or a 2'x4' panel on the front wall center. What do you guys think? My main concern now is that it will "dry" out the sound as well.

Thanks.

[paul79]

I'm thinking of flanking a polyfuser with 2 QRD diffusers here myself on the front wall between speakers.

[Big Red Machine]

I'm a big proponent of diffusion. I think it is underused. If you tame your bass issues first, don't try to absorb everything with absorbing side panels. Give diffusion a try on the sides and ceiling.

[JLM]

A common approach (like from Floyd Toole) is to use absorption on front/rear/corners and diffusion on side walls.  Toole doesn't promote lots of treatment (we acclimate to typical residential settings).  I use book cases on side walls, filled in a fairly random pattern (probably a good compromise). 

For absorption high density fiberglass is the best (see GIK circle here at Audio Circle).  Open cell foam is all but useless.

Diffusors are only effective down to around 1,000 Hz (they work based on size of sound wave).  They must be made of sound reflective materials (not thin sheets of plastic).

Overall low frequencies are extremely hard to treat.  Proper room shape, dispersed bass sourcing, and finally a bit of DSP/EQ (effective only at the listening spot) is all you can do.

[Austin08]

Hi Guys,

Placed 2 2'x4' foam (4 inch thick) panels on the center front wall over the weekend.  It did not sound good. Focus improved but overall SQ esp on female vocals sounded dry with a definite increase in sibilance. I have since removed them.

Thinking of QRD diffusers now. Maybe a 2'x2' or a 2'x4' panel on the front wall center. What do you guys think? My main concern now is that it will "dry" out the sound as well.

Thanks.

I had a similar set up like your. Since then I just replaced those panel with 2 GIK Alpha panels. The different was night and day. (maybe because my speaker is MG So diffuser work better?) I am not expert but after putting two GIK Alpha panels, I could hear better detail, soundstage is bigger, and vocal is more natural compare to old set up.

[andycsb]

Thanks guys.
@JLM...I often hear that foam is not good too. Why do you think that? Unnatural soundng after absorption? I am concerned about it thinning out the sound....esp in the vocal band.
@austin08...nice setup! My speakers are monopole. Did those diffusers thicken and smoothen vocals in your case?

[rodge827]

I found this Room Reflection Calculator posted a while back on AC, and it helped my room issues immensely!

http://www.acoustic.ua/forms/calculator4.en.html

You can use inches instead of cm's and get the same results.
I do used DSP (Dspeaker Antimode Dual Core 2.0) for bass frequencies below 110hz.

Chris 

[Austin08]

@austin08...nice setup! My speakers are monopole. Did those diffusers thicken and smoothen vocals in your case?

Vocal seems floating and lighter (smoother?). Before, Vocal sound very intense and heavy.

[Big Red Machine]

Foam is very limited in frequency range as opposed to Owens 703, for instance.

http://www.bobgolds.com/AbsorptionCoefficients.htm

[JLM]

Best recipe for good room acoustics, in order of effectiveness/importance: 

- Layout, speakers/listener away from walls, near-field is best for removing room induced effects
- Diffuse bass sourcing (multiply subs, search for 'swarm' here at Audio Circle)
- Proper room shape (read Floyd Toole's "Sound Reproduction"), avoid cubes and long tubes to avoid echo
- Room size, bigger (within sane residential limits) is better for reducing room effects
- Treatment only as necessary (too much can deaden the sound)
- Add DSP/EQ only as needed (can only be effective at a single location)

I listen near-field (speakers 5 feet away from listening location) in a Cardas "Golden Cuboid" shaped room (8 feet x 13 feet x 21 feet).  As such treatments are minimally effective.  Also use DSP (below 250 Hz) to provide baffle step compensation.

[C17FXR]

I listen near-field (speakers 5 feet away from listening location) in a Cardas "Golden Cuboid" shaped room (8 feet x 13 feet x 21 feet).  As such treatments are minimally effective.  Also use DSP (below 250 Hz) to provide baffle step compensation.

OMG your ceiling is 21 feet high, your heating bill must be through the "roof" in the winter.        

Good information in this thread, keep the info coming guys starting to looking into this myself.
Diffusion or absorption that is.  Not the 21 foot ceiling, having a hard enough time with my cathedral ceiling. 

[jk@home]

I use QRD diffusers on the front wall behind monopole speakers. Less of an effect than when I had Maggies in there, but still gives the music a touch more depth. If you go with the plain foam QRDs, make sure you lay a couple of good coats of paint on them before your final verdict, as the unpainted version is a lot more absorbent.

OC703 absorption everywhere else. I do have a couple of ATS foam panels (actually made slightly longer by cutting/combining three 2x2 panels) on the side walls behind the speakers. Using just to break up the two plain parallel side walls, without adding too much more absorption. Plus I needed something else visually in there, other than more plain fiberglass panels. 

To the fellow who wants to try polys with QRDs, I played around with polys when I had the Maggies, and tried exactly what you proposed with my present KEFs. Prefer all QRDs. Just remember that QRDs offer time domain diffusion, polys not so much. I would stick with one or the other.

I'm happy with the acoustic treatments now, current project is building a pair of "subwoofer bridge" stands, to isolate the KEFs from the subs better (not that it really seems to be a problem).

[andycsb]

Thanks for info guys.

@jk@home. Your system sure is impressive. Did the diffusers change the tone in the vocal band? In your setup...besides a little more depth...any change in image density and sibilance? Thanks.

[jk@home]

To me, image density is similar to depth, so I would say yes to that. Sibilance?, no. The Kefs can be real tricky with sibilance, being "bright" one of the main complains about them. Adjusting speaker height, toe in, plus the electronics used have had more effect in controlling that issue. There still is a touch of that in my system, with some of our music, but I don't blame the QRDs for that. More likely the 20 yr. old Aragon amp that is still hanging in there until something more worthy comes along.

[roscoe65]

This is off-topic, but what are the subs you are using?  and what are their dimensions?

R

I use QRD diffusers on the front wall behind monopole speakers. Less of an effect than when I had Maggies in there, but still gives the music a touch more depth. If you go with the plain foam QRDs, make sure you lay a couple of good coats of paint on them before your final verdict, as the unpainted version is a lot more absorbent.

OC703 absorption everywhere else. I do have a couple of ATS foam panels (actually made slightly longer by cutting/combining three 2x2 panels) on the side walls behind the speakers. Using just to break up the two plain parallel side walls, without adding too much more absorption. Plus I needed something else visually in there, other than more plain fiberglass panels. 

To the fellow who wants to try polys with QRDs, I played around with polys when I had the Maggies, and tried exactly what you proposed with my present KEFs. Prefer all QRDs. Just remember that QRDs offer time domain diffusion, polys not so much. I would stick with one or the other.

I'm happy with the acoustic treatments now, current project is building a pair of "subwoofer bridge" stands, to isolate the KEFs from the subs better (not that it really seems to be a problem).

[jk@home]

They are diys that I made years ago. 12" drivers from Rythmik (back when he offered non-servos) Thinking TC Sounds made them special for him. The internal box area is 2 cubic feet, the external is 18" cube. Lots of bracing. The front grilles came pre-assembled from Parts Express, fit perfectly. All I had to do was sink some neo magnets into the boxes (at just the right spots), to line up with the grilles magnets.  I use the subs for mid bass to take up the slack for the LS50s.
 

 

[roscoe65]

Thanks jk.

I have some GR Research XLS Encore monitors that will live on a pair of PE subwoofers and I wanted to know how they would look.  Your subs are about 50% bigger than mine, so I think I can get by with it.

R

[jk@home]

Thanks jk.

I have some GR Research XLS Encore monitors that will live on a pair of PE subwoofers and I wanted to know how they would look.  Your subs are about 50% bigger than mine, so I think I can get by with it.

R

How do you plan on isolating the monitors from the subs? I raised my KEFs a couple inches yesterday with some wood blocks, to get an idea of what the added height from the bridge stands would sound like, while still using the Isoacoutic platforms. Liked what I heard, so now I may just add another concrete paver, painted with black Duratex and resting on Sorbothane pads, between the sub's tops and the Isoacoustic stands (just like the one between the subs and the floor base). And not even go with bridges, don't think they will be necessary.

[roscoe65]

I'ma big fan of isoacoustics stands ( I use them with other speakers) and plan on doing the same.

You can also try using the higher extension tubes with the Isoacoustics stands.  But then again, the additional mass loading on the subs wouldn't hurt as well.

[jk@home]

I'ma big fan of isoacoustics stands ( I use them with other speakers) and plan on doing the same.

You can also try using the higher extension tubes with the Isoacoustics stands.  But then again, the additional mass loading on the subs wouldn't hurt as well.

Just an FYI, if you plan on going with the newer aluminum cast Isoacoustic Apertas, they only come with the shorter set of tubes. Plus they are actually 3/4" lower than the plastic ones when set up as low as possible.

I settled on upgrading the plastic to Aperta models, and placing them on Mapleshade blocks, with PE isolation cones super glued to the bottom of the maple. That gave me 3+ more inches rise than just using the Isos.