John Sayers' Recording Studio Design Forum Archive

Thanks Steve, you've put my mind at rest about these hangers. Won't be starting for a while longer but I feel prepared now.

Hi guys, I'm back at it again. I've cleared out my room and am ready to buy the materials and start work.

I will tackle the bass hangers for the closet area first.

You mentioned using a herringbone pattern for the hangers. I was wondering how you get the hangers to stay in such an arrangement without moving out of position and touching against each other?

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This is the image in my head. How do you make them stay at the desired angle without shifting?

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I noticed you mentioned varying the thickness of the panels. I don't understand why. It seems that a panel 1/2'' thick should be able to absorb anything a thinner panel could, but even better.

So why not have all 1/2'' thick panels instead of alternating from 1/2'' to 1/4'' for example?
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Will 1'' of insulation on both sides of the base be enough?

Can you substitute 2.5-4.5 PCF Roxul Rockwool for the 3.0 PCF Fiberglass?

Which product would be best for a hanger? I was thinking of using 1'' AFB Roxul Rockwool but don't know if it's going to work for a hanger.

Does the insulation have to be faced with paper for glueing or will the unfaced stuff adhere just as well?

At the moment I'm considering using Rockwool behind the slat resonators and the faced fibreglass for the hangers; both hanger and slat resonator insulation wrapped in burlap. I would like to use all rockwool if possible though as it's cheaper.

Steve, was still wondering what you think about this when you can get to it. Many thanks.

I was thinking if I use 2 chains vs. 1 chain per panel I can get them to stay in the herringbone pattern... which will require i build a frame for this hanging pattern and for isolation like you mentioned. I think that's the route I'll take.

I'm still wondering about the thickness. Is 1'' on each side of the panel enough or should I go thicker? What should I vary the thicknesses from? From what thickness to what thickness would be a good range? I was thinking 1'' to 2''. What do you suggest?

I appreciate your help.

Your plan for double chain hanging is the right one; roxul is essentially a direct replacement (acoustically) for 703, so that's fine; and for wrapping the panels you want something a bit thicker preferably; like standard 3-1/2" house insulation.

If you fasten the insulation to the panel by wrapping duct tape around it every couple feet, that will change both density and thickness of the insulation over the length of the hanger; this broadens the effective range of the panel, which is a good thing.

Also, my reasons for differing thicness of panels follows the same logic; different panel thicknesses will have different resonances, at which absorption will be highest; by using different thickness panels, you get a smoother response (more even absorption)

Wrap them first so you know what the REAL thickness will be; then hang them spaced just far enough apart so the insulation touches the next one but the PANELS do NOT have a chance of touching each other.

The herringbone pattern forces lower frequency waves to travel a longer path thru the herringbone, into/out of the absorbers mounted around the inside perimeter of the trap, then back through the herringbone and the cloth cover, before being able to return to the room. On the way, the insulation gets TWO tries at absorbing sound; plus, the angle of incidence is very shallow so the sound actually has to pass through MORE absorption on its path.

If you already have enough mid-high frequency absorption in the room, you can place the 3 PCF stuff across the FRONT of the trap - this should lessen the HF absorption a bit and enhance the LF absorption more, by virtue of the 1/4-wavelength effect (more bass absorption) and by partially masking the hangers/fluffy insulation (for slightly less HF absorption overall)

If you're not sure about the last paragraph, you can just put the frame across the panel mouth until testing is done; cloth won't change the result very much and if the sound in the room is too lacking in highs you can put roxul batts across the face of the trap before adding the cloth. Higher density than 3 PCF might be better if that's the case; more around the 6 PCF range would keep the room brighter and still give good bass absorption... Steve

Thanks Steve, this will help me a lot. Some great ideas and information here. I think I will go ahead and make the hangers now.

I'm not sure if I'm understanding the last two paragraphs about the cover though. Should I place the 3 PCF or 6 PCF insulation on a backing such as a large plywood panel, then place this across the opening? Or should I place it within the framing of the room facing side of the hanger frame?

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So if there are enough highs, just cover this frame with cloth. If there aren't enough fill it with 6 PCF and then cover with cloth? I'm not sure if you meant placing the cover insulation by itself, within the framing, or backed by a panel. I'm guessing you meant within the room side of the framing.

How about placing a plywood panel covered with cloth to cover the entrance to the hanger traps? Would this interfere with the working of the trap too much? I was thinking the lows would just pass through and the highs would all come bouncing back. What do you think of this? Or will the panel reflect back some low-mids I would be better off absorbing and this is why you suggest cloth?

I was thinking of using linoleum for the center mass of the hangers like Barefoot suggested. Lowe's doesn't carry anything near 1/4''. I'm thinking these will be tiled linoleum instead of panels. Anyone know where to find the ideal panel form Linoleum in at least 1/4'' thickness? So far my internet and phone book searches have proved fruitless. Will have to stop by tomorrow morning at a few places to see what's in stock.

I think this may be ideal instead:

http://www.aknightcompany.com/productli ... erview.asp

I finally took some action after I felt I knew enough to start. I went to Home Depot and we took a look around and bought all the raw materials.

They didn't have masonite or celotex, but they had 1/2'' MDF. I compared it to some dense particle board and it seems like this particle board was denser and heavier than the MDF. It was also cheaper. The MDF felt like it was bending more than this particle board of an equal thickness when we picked it up. I told the guy helping me my plans and he said some people use this particle board for speaker cabinets. Well, I think it will work just as good as MDF. I got 3 boards of 1/2'', 1 board of 5/8'', and 1 board of 3/4''. They cut each board into four 1' x 8' strips. 1` because I got 13'' as the width for each board from my calculations. Each one ends up a little less than a foot. Close enough, I don't want them touching anyway.

I went with standard house insulation like you recommended... R 13 Fibreglass rolls. It's 3 1/2'' thick.

Will probably start tomorrow and take pictures when I finish and along the way perhaps. Thanks for your advice Steve, it's really helped me to get going on this.

Instead of a cage we are going to try something else
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= existing joists in closet.

The two side supports are sections of 2''x4'' 's. These will be connected to existing joists. Then the four beams running across will be 2'x 4's for hanging the traps in the herringbone pattern. I will attach cork to the two side beams where they meet the walls to decouple them a bit.

Basically an improvised top section of the planned cage.

ollie wrote:I usually use 1" Dacron covering 1/2" Celotex or solid pink insulation, its very light but absorbtive. Masonite and pegboard also work but are heavy and more expensive.

Hello,

Sorry for jumping a little late on this train.

What are you talking about when you mention Dacron and Celotex ? A quick search on Celotex on Google reveals quite a lot of different products... What's the density of Celotex ? (Masonite seems to be around 1 kg/m2 of 1mm thickness). What is Celotex is actually made of ? I might be able to find an equivalent product made in Europe.

Also, I suppose the density of the product would change the frequency range of bass trap hangers ? How do you calculate this ?

Thanks a lot,

Michel

Im just getting use to this sketchup stuff. But here is a file and a question.
I think you ansewered my question early on this thread but its unclear.
Can you NOT had hangers in the space of a Mass/space/mass isolation wall?

Glad you guys brought this back; I apparently missed Lex's questions of last year

Lex, if it's not too late - you do NOT want plywood backing anywhere in your trap, this isn't a resonant trap so air depth BEHIND the absorbent is your friend.

what I meant as to the 3 or 6 PCF stuff - first build your trap with hangers, inner walls lined with 703 or equivalent, etc - the FACE of the trap initially should have just a frame (like you were going to build a wall here) and you can just hang whatever cloth you intend to use temporarily from the top of the frame, so it's in the same location it will end up at.

Then, with just the insides of the trap finished (inner wall lined with absorbent, hangers finished and in place) do whatever testing/listening you can, and if the highs don't seem bright enough I would then opt for the HIGHER density insulation (like 6 PCF) in between the "studs" of your front frame, covering finally with the cloth. If you do NOT notice a lack of highs, then you'll likely get better overall results using the lighter weight (3 PCF) absorbent.

In either case, this goes BETWEEN the studs of your face frame, with the cloth over that.

msikio, the type of Celotex referred to here is also sometimes called (wrongly) "sound board" - it's light (maybe half the weight of gypsum wallboard) slightly porous, and made of reprocessed wood fiber with very little compression (as compared to MDF, particle board, Masonite, etc)

"dacron" refers to a light spun dacron insulation, usually white in color - you can just use standard spun fiberglass house insulation for this, the thinner R-11 batts work fine.

As to density/frequency calculations - I'm not sure anyone has done this. Typically people just "cut to fit" whatever spaces are available behind trap walls, making different size panels to fill the space; I've seen as small as maybe 8" wide and 8 feet long hung horizontally in a sloped ceiling, up to nearly 3 feet wide and 8 feet long hung vertically. I think the variability in spaces is at least partially responsible for NOT having specific resonances, along with the fact that the insulation wrapped/taped to the boards damps them. In my next life, I hope to have time to build a trap with one section left as ingress/egress, and experiment with differing materials as well as just filling it with offcuts of insulation, and run comparison tests with graphs; but please don't ask in the next 5 years about that part, I doubt it'll happen before then

Carpwftx - hangers belong inside a TRAP with an absorbent front; this is where they work to absorb lower frequencies, literally by "swaying in the breeze", so to speak, which absorbs the energy required to phyically move them as well as the absorption caused by longer path lengths, insulation portion of the hanger...

For inside a wall (which is your situation) you just want insulation, anywhere from 1 to 3 PCF (lower density here improves BASS TL, which is generally where walls are weakest, so standard house insulation (.8 PCF figerglass, for example, but NOT foam types) works fine and is generally cheaper than ANY of the rigid board types.

For a typical wall with double gypboard on the outer sides of frames, a complete fill of fiberglass with slight compression when you attach wall panels is best; this gives some damping of the panels without causing hard contact between the leaves of the wall.

HTH; and Lex, sorry I missed your last-year's question. When this happens, and you need the info, PLEASE BUMP your posts til I catch it... Steve

Thanks Steve for the quick reply. This forum is really interesting.

knightfly wrote:
msikio, the type of Celotex referred to here is also sometimes called (wrongly) "sound board" - it's light (maybe half the weight of gypsum wallboard) slightly porous, and made of reprocessed wood fiber with very little compression (as compared to MDF, particle board, Masonite, etc)

I don't know if there's an equivalent of this over here in Europe. I can use thin chipboard instead I suppose.

knightfly wrote: "dacron" refers to a light spun dacron insulation, usually white in color - you can just use standard spun fiberglass house insulation for this, the thinner R-11 batts work fine.

This is probably what we call Molleton. It is used underneath fabric affixed to a wall.

knightfly wrote: As to density/frequency calculations - I'm not sure anyone has done this. Typically people just "cut to fit" whatever spaces are available behind trap walls, making different size panels to fill the space; I've seen as small as maybe 8" wide and 8 feet long hung horizontally in a sloped ceiling, up to nearly 3 feet wide and 8 feet long hung vertically.

...

As you can calculate resonant traps, I just assumed there was a way to calculate hangers too... no worries.

By the way, are hangers better than resonant bass traps ? Would you normally use hangers in a bigger space or for lower/higher frequencies ?

Thanks in advance,

Michel, Paris, France

msikio wrote:By the way, are hangers better than resonant bass traps ? Would you normally use hangers in a bigger space or for lower/higher frequencies ?

I think the problem with resonant bass traps over hangers is that they are tuned to specific frequencies (i.e., not broadband) so you would have to first know what the problem frequencies are and then make a trap for each one. Hangers are more of a broadband absorber so you would't to know about any particular bass frequency problems before you test the room.

len

Michel - check this page out, about half way down.

http://johnlsayers.com/Studio/Pages/Somewhere.htm

What I do with hangers when you are placing them between two parallel surfaces, like in the ceiling of the studio, is divide the distance and put a hanger, divide again and put a hanger etc etc till you have enough. In other words you put them at the nodes of the harmonics.

In a corner trap you do what Steve said, just cut them to fit.

I use the light Celotex board Steve mentioned. We call it Canite in Australia. It's the board you see used for notice boards, painted white on one side and you can stick drawing pins into it easily.

That Dacron is so much easier to use than prickley, itchy, fiberglass

Oh - that control room is somewhere in Europe so you can get the materials


cheers
john

Hello John,

John Sayers wrote:Michel - check this page out, about half way down.

http://johnlsayers.com/Studio/Pages/Somewhere.htm

Nice work on that control room, "somewhere in Europe"

John Sayers wrote:In other words you put them at the nodes of the harmonics.

Interesting

John Sayers wrote: I use the light Celotex board Steve mentioned. We call it Canite in Australia. It's the board you see used for notice boards, painted white on one side and you can stick drawing pins into it easily.

I might be what we call "Isorel mou". It's available in 10mm and 20mm thicknesses. It's made of wood fibers.

Thanks a lot,

Michel