Room Treatment

[ShinOBIWAN]

Hey chaps I spotted the great thread on bass traps here and wanted to post my own room treatment effort.

On the walls I have framing with 3" Rockwool RW5 and 2" RW3 rigid fibreglass.

Within the fitted cabinets at the front room are alcove where the speakers partially sit. Inside the alcove is treated with 4" RW5 on all surfaces to help calm bass.

Besides physical treatments there's also digital room correction taking up a little more of the slack.

Here's the mockup I worked to:

 

[ShinOBIWAN]

And some snaps of the work as it progressed. These are pretty self explanatory so I'll be sparse on commentary.

First is the frame work:

 

[ShinOBIWAN]

Painting and fitting the fibreglass into framework.

 

[ShinOBIWAN]

The stretching, tacking and gluing fabric over a foam backing and around the frames.

 

[ShinOBIWAN]

2" Rockwool RW3 goes in between the flanking 3" RW5.

 

[ShinOBIWAN]

Then fast forward and do the remaining walls:

 

[ShinOBIWAN]

First part of the fitted cabinet goes in at the front of the room:

After this the projection screen goes up and I can finally watch movies again(through headphones ):

 

[ShinOBIWAN]

New carpet and sofa go in and the important bits of kit are moved back whilst waiting for the last bits of the fitted cabinets.

Speakers are given a face lift with baffle trim done in the same material that went on the walls.

 

[ShinOBIWAN]

And that's where I'm at. The project is stalled by the manufacturer of the cabinets and specifically they are having troubles delivering that two bits that fit around the speakers. I had them custom made since the application and fit is quite specific so this is half the problem and the other is that they're having trouble sourcing the same wood from their usual supplier.

Its an annoying wait because the room is very nearly finished but I've promised they'll arrive before Christmas.

Not had chance to listen yet and hear the improvements the treatments have made. I've been so busy with other more important(but boring) things. I hope to do so very soon though.

 

[Tenson]

What is the cream fabric you used? Is that a printed pattern on it, or is it suede?

How does it sound? Your work is lovely as always so I don't want to be negative, but I'd have thought it would sound too dead looking at the amount of coverage you have gone for. The soundstage will be considerably collapsed left to right compared to what you are probably used to.

I'm re-working the acoustics in my room at the moment too, and have gone for only treating appox 1m square areas on each side wall at the reflection points. I positioned most of my treatment on the back wall, with absorption directly behind the listener, again about 1m square and quadratic diffusors pretty much floor to ceiling left and right of the listener on the back wall. I am still planning to treat a patch on the wall directly behind each speaker.

I tried the diffusors on the side walls spaced around the first reflection absorbers at first, and found the result too dead, with a very narrow soundstage. I think you need some reflections from the sides walls to let the system 'breath', just not ones that arrive in the first 10ms or so.

Anyway thats how I have gone for it. I will do a write up in the next couple of weeks when I finish. My microphone broke and I am still waiting for a replacement to arrive.

P.S. sorry it seems I posted before you had finished! Also to add, despite the points I made about soundstage, you will get incredible detail

 

[Mr_Sukebe]

Looks like a lot of good work, nice.
How did you measure the room upfront and decide the level of damping required?

 

[Dev]

Lost for words Shin:mana:

Well done.

 

[lbr]

Utterly remarkable. I bet that sounds fantastic. :notworthy

Can I come and live with you please :green:

 

[andyoz]

Shin, you really make me chuckle...you don't do things by halves.

My initial thoughts concur with Tenson...too dead dude unless you are going for pure home theatre usage. Diffusion on some of the walls wouldn't hurt at all...

I would maybe experiment with some low-freq membrane absorbers on the lower parts of the walls in place of you existing mid and high frequency absorbers. You can use the existing timber framing, etc. The room is small and I can only assume there are some "hot" room modes in there.

I am going to be posting my own experiments with my new listening room - the shell of which is finally complete!

 

[Tenson]

What is the brown center sstrip? Is that purely for looks, or is it acoustic?

Andy's idea is good. I'd certainly consider covering the bottom panels (still with the rockwool in there) with 6mm ply and seal with caulk. You could also still cover the front with the fabric. This will help the bass a lot and liven the room up a bit.

I'm not sure about having all the mid and high absorbers at the same height in the room then, so you might alternate top and bottom panels being bass traps and mid-high absorbers. Hope that makes sense.

Anyway I don't mean to rain on your parade. It looks stunning. I wish mine looked as good!

 

[andyoz]

Andy's idea is good. I'd certainly consider covering the bottom panels (still with the rockwool in there) with 6mm ply and seal with caulk. You could also still cover the front with the fabric. This will help the bass a lot and liven the room up a bit.

You may also consider mixing up the ply thickness and/or cavity depth behind a bit. Otherwise you could "suck" too much energy out of the room at too narrow a frequency band and make the LF response worse. I think 12mm ply on say a 100mm cavity has have peak absorption at around 75Hz (depends on many factors though). Maybe do half with 6mm ply and the other half with 12mm ply. That should offset the membrane resonances about 15-20Hz.

Also, make sure there is a 10-15mm gap between the ply and the mineral wool behind otherwise the membrane will be too damped, severely reduce it's performance. It's got be sealed to work as Simon says.

If you want to get real fancy, try some "slotted" absorbers with peak absorption around 140Hz. Basically, 18mm mdf with 6mm "slots" cut at 95mm centres, on 100mm cavity with medium density mineral wool in the cavity. These sort out the "gap" in absorption that normally occurs between where the stretched fabric absorpers taper off (below 200Hz) and where the membrane absorbers kick in below say 100Hz.

Really need to measure what effect the treatments are having to get a good linear response in there though.

 

[ShinOBIWAN]

Thanks for the kind words.

The fabric isn't air permeable and quite thick. Its known as Alcantara and is man made suede. No printed pattern, it has a grain so you simply brush the material with you hand to get whatever pattern your after.

I was worried I'd gone overboard on absorption when I first slotted in the fibreglass. The room felt very silent and almost completely devoid of any atmosphere - it was quite unnerving at first.

I went back and chose a reflective fabric as well as 6mm closed cell furniture foam for the backing to give some of the air back within the room.

As you also state Simon the lower portion is cover in 4mm ply and tuned to problematic area's as best as I was able to do with the dimensions of the room. I couldn't get the lowest frequencies <45hz but EQ will do here.

The brown center strip is simply 2" RW3(density = 60kgm3) as opposed to the 3" RW5(100kgm3) everywhere else. I went with this because the midrange driver first reflection is here and I was seeing a fair amount of combing in my initial measurements. RW3 is more effective than RW5 here.

Here's a part of the data I gathered before treatment so as to provide some perspective for comparison.

All measurements taken at the listening position with no smoothing except for the CSD plots.

Frequency response at listening position with no smoothing:

Step response at listening with no smoothing:

CSD showing 1 second after pulse with 48oct smoothing:

 

[Tenson]

Thanks for the kind words.

The fabric isn't air permeable and quite thick.

I chose a reflective fabric as well as 6mm closed cell furniture foam for the backing to give some of the air back within the room.

Interesting way to do it. What you have then is basically a 'limp mass' absorber. Many studios use a cavity filled with rockwool and covered with 'PKB2' (plastic deadsheet and felt on one side.) It absorbs over quite a broad range from upper bass to mid and then you can have the PKB2 either way round to the room to have more or less energy absorbed at higher frequencies.

Behind the limp mass absorbers they also sometimes have membrane bass traps similar to the plywood over a cavity design you have used.

How did you go about tuning the plywood absorbers?

Anyway, know a little more about how you did it I have to say I think it sounds like you've done a great job and most potential issues. I look forward to your reports on how it sounds. Don't forget to tell us lot over here! I haven't read DIYA for ages.

 

[ShinOBIWAN]

Hey Simon

I built it and tried to give aesthetic appeal but I have to say most of the theory credit goes to Rainer Weber who is the chief engineer at Siemens Acoustics. A forum member on here named Gerner, who I oddly argued with over DRC vs. straight gain with wire, put me in touch with him after becoming friends over email. Both Gerner and Rainer are great guys and I thank them for much of the help as well as suggestions. I'm not much of an acoustic treatment expert so I followed the plan as closely as possible. Its still not perfect and allowances had to be made in order to reach a level homeliness and practicality. At one point there were talks about 6" membrane absorbers but quickly scaled back to my original plan of 3". I also wanted liked his idea of a floating treatment on the roof between the listening position and speakers but again the room is already small and that would have made it look pretty imposing and unfriendly. Also the cabinet at the front of the room is less than optimal since it has cavities causing resonance, these are(or will be) filled with 4" RW5 around the loudspeakers to try help somewhat.

BTW Rainer is behind this enterprise and does some very nice work. He is also a friend Aleks at RAAL and uses his ribbon in an upcoming design:

http://www.akustiksystem.de/

I will not know exactly how well the room performs until I get the measurements done but even now you can tell its made a large difference with everyday things such as just talking in the room or clapping hands etc.

 

[andyoz]

Shin,

Do you know the resonant freq. of your 4mm ply on 3" cavity membrane absorbers. I suspect they could be well above 100Hz (probably 120-140Hz) and if you're not careful, you could have a nasty "suck out" of energy in the lower midrange with very little effective low-frequency control. Membrane absorbers can be savagely efficient.

Can you generate some test tones? Place you hand over the membrane absorber and vary the frequency until you feel the panel really get going, that's your resonance.

We normally rely on slot absorbers in the upper bass/lower midrange as they are more predictable.