[CAK]

Dedicated 2 channel room 14x12x8. Whats the word on front wall treatment?

I have a 3x5 bay window in the middle of the front wall (in-between speakers). I have 2x4x2" panels on either side of the window, 2" blinds with thin drapes over window. Thinking about adding an additional acoustic panel over window, or possibly an acoustic blanket over window.

That would be a total of (2) 2x4x2" panels and either an additional panel 3x5' or blanket 3x5' covering the 3x5' window. Does this sound like overtreatment for a 12' long wall or am I close?

For reference, I have (2) 2x4x2" panels on either side wall (14' wall) covering 1st and 2nd reflections with (2) more panels on the back wall, 3 feet behind listening chair.

Speakers are Infinity Renaissance 90. They are a somewhat di-pole plannar driver.

Here's more info on the speakers:

http://www.infinity-classics.de/infinity/models/Renaissance-series-1992/index-Renaissance.htm   (just click on 90 on left side)

I have built-in bass trap columns from floor to ceiling in each forward corner 18x15".  As far as the columns...the right column was already there as it houses AC ducting for downstairs. I reconstructed the column to work as a bass trap and added the left column so both sides are symmetrical. Would rather have not had them, but had no choice so decided to make them as acoustically functional as possible.

Also, my plans are also to add another 2x4x2" panel on the side walls closer to the pillar for a total of three on each side. It seems like I have allot of slap echo on the empty wall from behind the speaker to the column. Probably space the panel about 6" from the column (to match the distance from front wall panel to column) and bring the existing panels back towards the listener position to try to equal out the sides a bit.



Speakers are 7'6" apart and listening position is 8' away.  Speakers are 38" from front wall.
Any suggestions would be appreciated.


Here is a picture:

[bpape]

How and with what are the bass columns built?  What particular issues are you trying to resolve by covering the window?

Bryan

[Mike Dzurko]

Good looking room already. I like your wall color choice     My recommendation would be to listen closely to Bryan, he knows his stuff.

[CAK]

Bryan,

Funny you should ask about the columns. I lurk this site and the AVS site alot and there was a member over there that had to work with a column for his HT room. I think you designed the bass trap for him...I pretty much just copied your design and duplicated it on the other corner as well

The room actually sounds really, really good.

The one issue is this: my plans are also to add another 2x4x2" panel on the side walls closer to the pillar for a total of three on each side. It seems like I have allot of slap echo on the empty wall from behind the speaker to the column. Probably space the panel about 6" from the column (to match the distance from front wall panel to column) and bring the existing panels back towards the listener position to try to equal out the sides a bit.

The thread kind of started out as a front wall question. I know the curtains are doing nothing for treatment. Just wondering if I should get a bit more aggressive behind the curtain to equal out the front wall. The side wall at column is a whole different issue, but I'm hoping my plans above will help with that?

[bpape]

So the 2 front corners in the room are just open, cloth covered absorbers?  I'm confused - sorry, long week.  Time for a 

Bryan

[CAK]

Bryan,

Actually, they are framed out and coverd with 1/4 ply. The insides of the columns are treated per your design with absorption.

[8thnerve]

I don't know specifically about Bryan's design, but that doesn't sound like it'll work.  By putting ply or drywall up, you are blocking most of the sound from getting to the area Bryan designed.  You need fabric or some other porous material that will allow sound to travel through to get to the absorptive stuff inside those columns.  I would suggest cutting out an inch of the drywall on those columns in both corners where they meet the walls.  Then cover that 1" vertical gap with fabric or something non-reflective and you'll have a custom corner trap!

Nathan Loyer
Eighth Nerve

[rockadanny]

CAK - Looks fantastic!! Huge WAF. If this method works - hiding/disguising the "audio" treatment behind architectural improvements, I may be able to properly treat my audio/living room.

Bryan - How much absorption would be lost (in reflection) if the 244 panels were enclosed this way - boxed in with 1/4" plywood? Is there a better, more transparent material to use other than plywood? It would need to be somewhat rigid to appear like part of the wall? Or differently constructed?

[CAK]

I don't know specifically about Bryan's design, but that doesn't sound like it'll work.  By putting ply or drywall up, you are blocking most of the sound from getting to the area Bryan designed.  You need fabric or some other porous material that will allow sound to travel through to get to the absorptive stuff inside those columns.  I would suggest cutting out an inch of the drywall on those columns in both corners where they meet the walls.  Then cover that 1" vertical gap with fabric or something non-reflective and you'll have a custom corner trap!

Nathan Loyer
Eighth Nerve

Unfortunately, the one column houses AC ducting. Open columns would have been optimal but I also needed to dampen the actual duct from air noise entering the room. Bass still travels through the 1/4 ply and gets absorbed inside the column, it's just not as efficient as leaving them open.  Like I said, I had to make a compromise 

Not sure if a 1" gap along each wall would be a significant opening to do anything?

Believe it or not, this room does not have any bass issue's...it's +/- 4 db from 25hz and up (+4 at 44hz and -3 at 70hz) Just mostly concentrating on reflective area's and slap echo.

[8thnerve]

Not sure if a 1" gap along each wall would be a significant opening to do anything?

It will alright, and it'll address slap echo and virtually every other acoustic anomaly as well.  By cutting that gap, you get rid of 4 corners in the front of the room.  (has to be done right, from the wall it should be a smooth shot into the fiberglass, I can give you more details if you're interested)  If both of those areas are stuffed with fiberglass or mineral wool, you'd be blown away by the difference.

Nathan Loyer
Eighth Nerve

[bpape]

May well be from a frequency response standpoint - more concerned with decay time in the bottom end.  For purposes of calculations, those corner columns do almost nothing.  For a membrane (sealed) like that to work, it must be, well, sealed air tight for the air inside to act as a spring.  It's likely doing a little something but hard to tell what or where.

If it was me, I'd get some 4" behind the curtains or in front of them and likely the same centered on the rear wall before I'd worry more about anything more on the side walls.  You might also want to consider doing some 4" along the bottom of the recessed area up front (under the window and under the 2 panels you already have up there.)

It's also possible to do some 4" on the SIDES of those front columns.  I'm sure there's quite a buildup in that little nook and that would be an easy way to deal with it.

Danny,

You wouldn't want to do that to 244's.  Again, for a hard face massive face like plywood to work effectively, it needs to be over a sealed cavity with absorbtion close (not touching) the plywood.  Even if you do it right, you'd turn a broadband absorber into an absorber that would work efficiently over about 1.5 octaves only.

Bryan

[CAK]

Yes...details would be great!

Thanks

[bpape]

Just remember if you cut the slit at the wall to the area with the ductwork, the sound transmission will also go up into and out of the room.  I wouldn't recommend it. 

If you have the same thing in the rear, I'd open it up all the way assuming there's drywall on the wall surface behind the columns.  That will help with broadband in the rear and kill a much larger part of the corner.  If you just cut a slit, you'll get something in there and there will be some effect but 90% of the sound will still be bouncing off the hard surface.  Whether that's a good thing or not depends on how you want the room to sound.  Appears to me you prefer it a little deader than most.

Bryan

[CAK]

May well be from a frequency response standpoint - more concerned with decay time in the bottom end.  For purposes of calculations, those corner columns do almost nothing.  For a membrane (sealed) like that to work, it must be, well, sealed air tight for the air inside to act as a spring.  It's likely doing a little something but hard to tell what or where.

If it was me, I'd get some 4" behind the curtains or in front of them and likely the same centered on the rear wall before I'd worry more about anything more on the side walls.  You might also want to consider doing some 4" along the bottom of the recessed area up front (under the window and under the 2 panels you already have up there.)

It's also possible to do some 4" on the SIDES of those front columns.  I'm sure there's quite a buildup in that little nook and that would be an easy way to deal with it.

Danny,

You wouldn't want to do that to 244's.  Again, for a hard face massive face like plywood to work effectively, it needs to be over a sealed cavity with absorbtion close (not touching) the plywood.  Even if you do it right, you'd turn a broadband absorber into an absorber that would work efficiently over about 1.5 octaves only.

Bryan

Bryan,

Thanks for the info, I'll do the 4" behind the curtains and experiment with some absorption on the columns. No columns in the back, but I do have 2 2x4x2" panels on the back wall.  The side wall panel closest to the rear wall is about 4 feet away; the back of the room is livelier than the front by a small amount which seems to work well so far. I just need to tame the slap in the front.

That was the dilemma with the front columns. One had to stay; I tried to address the problem as best that I could by sealing up and not having the absorption material touching.  Symmetry is a huge thing for me, so I had to build one on the other side to match. 

Thanks again.

[CAK]

Bryan,

I was thinking...I can possibly eliminate the columns in the room but need your input on the alternative.

Instead of columns I can triangulate the corners with this dimension, 20" into the room from front wall, 15" from side wall. This would form triangles in the front corners which leaves me enough room for the AC duct which is now in the right column. I could build both solid and cover both triangles with custom floor to ceiling 2" 703 panels. 

The other thought was this, the right side triangle will have to be solid because of the AC however I can take the left column out altogether and just make a floor to ceiling panel that matches the right side 2" 703 panel, filling the void behind the left triangle with 703 (bass trap). The right side has to be enclosed for AC, the left side can be made to look like the right for symmetry. Make sense?

I'm wondering if having a bass trap in one corner will skew the sound to one side?

Your thoughts would be greatly appreciated 

[bpape]

Keep the front of the room symmetric.  If you need additional bottom end control in the front, I'd just build some smaller triangular absorbers in each of the 4 front corners to make it LOOK like one triangle.  You've isolated the HVAC for good reason - leave it.  Just add to it to get a more broadband benefit from those locations.  At most, the plywood covered columns are MAYBE doing 2-3 octaves centered who knows where and who knows what kind of coefficient they're yielding. 

Bryan

[CAK]

I did a little more bass plotting today; interestingly I'm actually -8db from 50-65 Hz.  I'm wondering if those columns are canceling that frequency out somehow?  Even with moving the speakers from 2' away from the front wall all the way to 5', not much difference in that range however low end (40hz and lower) disappeared some the further out I got. Also experimented with side wall distance, from 12" all the way to 28" center of tweeter, again not much difference.

In general, is it better to have an angled corner rather than a column? I can still isolate the AC; it'll just be in a triangle shaped box rather than a column.  It would also give me a little more wiggle room for speaker placement as I won’t have a corner protruding in to room.

I'm really starting to suspect my columns however I'm not sure if my room dimensions (14x12x8) are just such that it won’t matter, that frequency will be cancelled no matter what.

On a side note, can you PM a quote for a complete room make up from scratch, keep in mind I can fanagle/rebuild the columns some to suite the best possible response. This is getting frustrating and I may need to take a fresh approach.

Thanks,

Chris

[CAK]

For the experts...

What kind of effect would triangulating the front wall to side wall corners have on frequency response/ringing/echo etc.

As a general rule, would it be better to go this route than the columns I already have? In other words, what’s the lesser of two evils?

[Ethan Winer]

What kind of effect would triangulating the front wall to side wall corners have on frequency response/ringing/echo etc.

If you mean to wall off the corners with sheet rock - don't do it! All that accomplishes is removing the single best place for bass traps.

If that's not what you mean, please clarify.

--Ethan

[CAK]

Ethan,

If you look at the columns pictured on the first page, the right side houses an AC duct. I built the left side to match. I can take those columns out and fit the duct in a triangle compartment from floor to ceiling. The left would be built to match the duct in the right triangle. The triangle would be 20" out from the front wall, 15" from side wall.

Looking from above, instead of this:
_________
|     |
|     |
|___|   
|
| 

I would have this:

_________
|   /
|  /
| /
|/
|
|


I would be able to cover the triangles with 703 from floor to ceiling as well. I'm just wondering which is more detrimental to sound waves?

Chris