Control Room with cellulose in left in bags?

[widrace]

Hello folks, I'm new here and am requesting opinion regarding the use of cellulose bags - not blown or sprayed.

Regal Industries sells a rectangular bag that measures 12"x16"x29" weighing 25lbs. That figures to 7.76-lb/cf density. The bags would be stacked (at 12" thickness) wall-to-wall, floor-to-ceiling - surrounding and almost flush to the monitors. I wish to damp a somewhat problematic (measured) 48.6 hz 3,0,0 mode, and this stack could be located quite close to the null at that frequency.

The monitor wall is multi-splayed, of 2x12 framed construction, moveable fore/aft and houses 3 large monitors. Other than the monitor openings it is 100% faced with (cloned) RPG BAD panel. For this application, one inch of 6-lb/cf Acousticotton backing was substituted for 705 fiberglass the panel would normally use. Currently, all of the monitors are positioned flush with these panels, and the main L/R monitors are positioned at 20% of the length and width of the room. Incrementally moving the wall (towards the boundary) from 80.8" (the 20% point) to 70" placed the monitors in the 3,0,0 null and provided mixed results. To be sure, these monitors are currently neither freestanding nor soffited. It is possible to face and seal the front wall with multi-layers of drywall, etc, to realize a true soffit but I thought to investigate this idea first. No EQ is the goal, and some storage area would be welcome.

The room's boundaries are 14.4' x 23.1' x 33.6' (1/1.6/2.33) of frame construction with RC holding two-layers of X-code drywall. The ceiling is cathedral (peak running longitudinal) and the 14.4' height figure is an average. Drywall is also wrapped around each ceiling truss (width-wise) forming varying depth unsealed cavities. These cavities are faced in the same manner as the monitor wall except for panels being bowed into poly shape. Sidewalls use same curved technique as Sony M1. The floor slab is isolated and covered with 1" hardwood. The rear monitor wall houses two monitors and has not been built yet. For evaluation I functionally duplicated the front monitor wall.

The rear boundary also has a large full-width cavity extending 13' beyond the main rear room boundary, and begins at 12' elevation. In the middle of the room this cavity has a 4' high opening and reduces to 16" at each side. This is intended to be a passive bass trap, and is now partially filled with various absorptive junk materials. The face of this cavity along with an additional portion of the main boundary wall will be covered with rather deep diffractal diffusors. When all is said and done, the diffusors will be flush with the finished rear (monitor) wall.

For a test I bought some 30+ bags and surrounded one of the front monitors, placed directly behind the Acousticotton surface - with the bags extending floor-to-ceiling, sidewall-to-center monitor. Result was much tighter bass (regardless of the walls for/aft position), and brought up questions such as:

1) How close am I to a true hard-baffle effect?
2) Could this be a path to the best of both worlds - freestanding vs. soffit?
3) Estimated absorption coefficient of bags at 50-100 hz placed in a null?
4) How closely do I really need to package the bags?
5) Would these bags be as effective as 703/705 for this application?
6) How close could the 'bagged' monitor walls be pushed toward the boundaries?
7) Would some bags placed in the bass trap cavity at selected 1/4 wavelength intervals work well?

Cost-wise, closely packed bags are the same as 4" of 703 covering the same surface area, but the bags offer 3 times the depth. The modularity of the bags is a big plus and I don't have to cut/contain glass.

If anyone feels I am way off here please say so!

Comments please, your time is appreciated.... and sorry for long post too.

Thanks, Steve

[Ethan Winer]

Steve,

I'm sure those bags helped - probably a lot. But the only way to answer your own "how good" questions knowledgeably is to measure the room with and without them in place. Not just the response, but also modal ringing which is just as important. Do you have software such as ETF or FuzzMeasure or the free Room EQ Wizard?

--Ethan

[widrace]

I once had use of the TEF20 but that went away. Now considering ETF and Smaartlive. Will ETF do real-time FFT?

Thanks, Steve

[z60611]

I did a quick test a couple of years ago
http://www.bobgolds.com/CornerTrap/20040627/compare.htm
that includes having a bag of pink fiberglass in a corner.
Hardly definitive, but it did show some smoothing.

For years I've been lightly asking people to put 24 bags into their rooms (six in each corner) and do before/after tests with pictures.

[Ethan Winer]

Steve,

> Will ETF do real-time FFT? <

ETF has a mode where it sweeps repeatedly and updates the display continuously so you can see the effect of changes as you work. If that's what you mean.

--Ethan

[widrace]

Ethan, I suppose you would call that pseudo real-time. Sounds good enough for intended purpose however. Seems as if ETF nor smaartlive will individually do all of what I'd like. Still looking.

At the moment I have nothing more than a s/generator and RS SPL.

z60611, thanks for that info. I may be the guy that runs the A/B test you mentioned - but it will probably be with cellulose bags. Since no one has beat me up and professed doom/gloom, I'm thinkin' it may be time to carry on with more bags and some test gear.

Sure would like to digest some more opinion before I'm become ebays' biggest cellulose seller.

[brianrcdd]

I just ran across this post, and feel somewhat less crazy because I had just done the same thing. Basement studio with concrete walls. I was getting a severe low-end cancellation from the rear wall of the control room. I had seen a post about leaving the pink stuff rolled up in the corner. In my last trip to Lowe's I noticed that the square bags of cellulose were only 8 dollars, so I decided to give it a try. And I figured because I was leaving it in the bags, I could always return them if it didn't work.

It worked and then some! The difference was easy enough to detect, even without ETF. Before, the low end was there if I stood next to the back wall, but disappeared when I moved to the mix position. It was also very erratic throughout the room in general. With the wall stacked with the cellulose bags, the problem simply went away, making my monitors sound like they are supposed to. I can also get up and move around the room with less changes as I move.

Does it work better than 703/705? I'll probably never know, having spent available funds on the bags. Perhaps someone with a suitable test setup (Ethan?) could give it a whirl and let us know. As was said above, the cost is similar to the 70x solution perhaps a bit cheaper per sq ft. It's also available virtually anywhere, something you can't say for the OC stuff. I suppose a downside is it does eat up a foot of floorspace, but I'm very happy to give it up to get these kinds of results.

Brian

[jorge]

I have bales of rockwool stacked in 2 corners of my studio and it helps noticeably to even out the bass. It is ugly by usual standards, although it looks kind of impressive in an industrial way. When I get the time I plan to put the 2'x4'x4" rockwool slabs into Ready Traps bags to make them less unsightly, or else make SuperChunk bass traps.

My concern about bags of cellulose is that cellulose is very flammable and would go up in flames in a minute if it somehow got ignited. Rockwool is not flammable and is probably more effective per inch of thickness than cellulose for attenuating low frequency sound. Applying fireproofing solution to the surface few inches of the cellulose would require you to take it out of the bags. Another partial solution, given that you have already invested in the bags, is to make sure there is no electrical wiring (that could possibly cause a fire) in the corners and use the bags to fill the corners, covered over by a fireproof layer of 703 or 705 that could be thin (1" or 2"). This would reduce the possibility of igniting the cellulose.

[widrace]

I am curious to the flammability issue. The product that I purchased is rated Class 1 - at least it says so on the bag. Also says "Meets amended CPSC Std. for flame resistance....Critical radiant flux - greater than or equal to 0.12 w/cm squared. Smoldering combustion...less than 15%"

Out of curiousity I tried to burn some and it would not. To be specific, with a propane torch applied to a loose wad of the stuff a green hue was observed on the surface. With the torch removed the green hue stopped instantly and there was no residual burning regardless of how long the torch was applied. I wish I could say that about some of the other stuff in the room. Does anyone know the specific meaning of all that mumbo-jumbo on the bag?

I went ahead and bought 100 more bags of the same product and played around some more. First experiment was to distribute some 40 bags forming three rows in the 13' deep bass trap area. Row one was in front, row two in the middle, and row three against the back wall. The bags were staggered within a row producing 'windows' such that you could see the row behind. For the second level of bags the same technique was used. These were not solid-bag walls - about 30-40 % open area perhaps.

It totally changed character - from a echo chamber into a near anechoic space. With a buddy sreaming from the rear corner of the space I could barely hear him from the front - just 15' away.

The second test was the monitor wall again. Monitors are splayed at 30 degrees with the woofers placed about 70" from the wall behind and 58" from the side wall. Without any bags the sound was quite spacious with audible cancellations. As bags were stacked around the right monitor the spaciousness/cancellations were incrementally reduced and things tightened right up. With 100% fill around the monitor the area directly behind was quite calm, and the only LF I could hear was from the untreated monitor - rather boomy LF too. I did note the audible cancellations were reduced more with the bags primarily 'blocking' the sidewall as opposed to other directions. The overall volume balance between the monitors changed too. The 'bagged' monitor now required another 1/2 inch of channel fader to compensate (by ear).

Subjectively, it's much more accurate sounding, and more music requires a bunch less EQ at the board to sound good. The spaciousness element is missed but not with all that comb-filtering. Some rear diffusors should fix that I'm thinkin'.

I need to measure some of this. Please comment!

[jorge]

Widrace,
It seems I was wrong in my assumption that the cellulose was flammable.
According to the Regal website, their cellulose insulation is treated with flame retardant and flammability is not a problem. The data they present actually shows the cellulose to be equvalently fire retardant to mineral wool, and better than fiberglass. Your testing confirms that the cellulose is not a fire hazard.
In addition, the data on the one cellulose product on Bob Gold's acoustic absorption website indicates that cellulose can be similar to rockwool in its low frequency acoustic insulation properties.
Looks like you may be on to something, we should investigate cellulose insulation further. The only downside I have found is that it can rot or support mold and fungal growth if in a damp environment like a basement. It certainly seems to be less noxious to work with than rockwool or fiberglass. Thanks for sharing the idea.

[widrace]

Thank you jorge for you research and comment. I'm still playing around answering my own questions, and will share the results.

[jorge]

Thank you for your post and for raising the idea of cellulose insulation. I am looking forward to hearing about your experience with it. Fireproofed cellulose insulation could be a major improvement over rockwool or fiberglass. I am still itching from putting rockwool insulation into Ready Bags last night!
Do you know if anyone makes cellulose insulation in blocks (eg, 2'x4'x4") that could be used interchangeably with rockwool or 703? Also I am wondering if anyone makes cellulose insulation that has been treated with antifungal agents so it won't get mildew or mold growth in a typical basement environment.

[widrace]

Just so happens that when the truck dropped off the Regal bags I noticed a pile of bags from a different manufacturer that looked very close to those dimensions. They were shaped like fertilizer bags - so didn't have perfectly square sides. You could probably shape them however. Don't know the packaged density.

I'm out of town at the moment, and forget the brand name, but when I get back I'll find out and post the manufacturer. Good thing too was the bag wrapping was more robust than Regals.

I believe the Regal bags did have a spec on them about fungus, etc. I'll post that too when able.

[widrace]

The manufacturer of the wool bags is Certainteed. It's called Insulsafe 4 Premium Blowing Wool. Web site says: This product is noncombustible, noncorrosive and odor free. In addition, InsulSafe 4 won’t settle, contains no chemicals to cause mildew and fungus growth, contains no formaldehyde, provides no sustenance for vermin, contains no asbestos, won’t rot or decay and won’t absorb moisture.

Go here for futher detail:

http://www.certainteed.com/CertainTeed/ ... C2%AE4.htm

I called Certainteed to get the bags size and weight to calculate density (in the bag) but they couldn't tell me the actual size. Weight was something like 28 lbs., so by guessing at the size I'm thinking the density is somewhere around 7-8 lbs/cf. or better. A factory rep was going to call me back but hasn't yet.

A local supplier could probably tell you the actual size and cost. There's gotta be more manufacturers than Certainteed selling this kinda stuff too.

Cheers....