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#2747818 - 01/18/16 11:49 PM Build a Better Bass Trap/Ultimate Studio - Questions
devnull Offline
Member

Registered: 01/18/16
Posts: 2
Hi Ethan,
Thanks for all the info you make available - it has been most helpful. I'm particularly interested on your "Build a Better Bass Trap" design and the Ultimate Home Studio video. I have some questions on a number of points...

I'm planning my first (and last) home studio (control/live). Room is 15'x12'x8' approximately. Desk facing one 12' wall, all walls drywall except right side is masonry block and it has a 6Wx3H window in it facing my garage. Rear wall has door near corner. Floor will be tiled. Hope to be able to do some live recording in the back half of the room. I'll give more details and drawings in another post later when I've tried to figure things out a bit. Haven't REW measured it yet - have an RTA mic on order. Right now I'm just trying to plan some acoustic treatment options. Bob Gold's room modes shows sub 100Hz for my dimensions as:

36.6 hz 
48.4 hz  24.3% 
60.7 hz  20.2% 
69.9 hz  13.1% 
73.3 hz  4.6% 
78.9 hz  7% 
85.1 hz  7.2% 
87.8 hz  3% 
92.6 hz  5.1% 
96.8 hz  4.3% 

1) So - just to sanity check my understanding of your traps a bit...

High Bass Trap: 1/8" plywood has surface density of 0.42 so I calculate F=170/SQRT(M*D)=170/SQRT(0.42*1.5)= 214 Hz -1/2 Oct 151 Hz, +1/2 Oct 302 Hz (150-300 as you say).

Low Bass Trap: 1/4" plywood has surface density 0.8 so I calculate F=170/SQRT(0.8*3.5)= 101 Hz -1/2 Oct 71 Hz, +1/2 Oct 142 Hz (you say 80-150 - close enough).

You covered 80-300 Hz. What about a panel for 40-80? For instance, would 1/2" plywood with 7" depth cavity work giving F=170/SQRT(1.52*7) = 52 Hz, -1/2 Oct 36.8, +1/2 Oct 73 Hz? Would I use 2" FG in this case? Is it best to keep the FG close to the panel (>1/2" away) or is the 1.5" standoff you use still OK? Would some other panel type besides plywood be a better choice here?

2) Assuming I want all three panel types above, what would you recommend for panel rotation? I was thinking: High-Mid / 52 Hz / High-Mid / Split 101/214 Hz / repeat...
I was trying to figure out a way to put an 2" FG absorber in front of the 101 and 214 Hz panels (maybe mount the plywood panel on some standoffs inside the frame). In this case I might do something like: 52 Hz, 101-Absorber, 52 Hz, 214-Absorber, repeat. Does this sound like a resonable ratio? I'm thinking the LF range needs more area than the higher LF octaves.

3) Do you feel that the 2" FG absorber is sufficient on your mid-high given you have the panel traps covering 80-300 Hz - e.g. 4" FG absorber is overkill given the panel traps - or would 4" be better if I have the space?

4) I assume if I have some panel traps in the corner (on both walls - maybe 1 52Hz and 1 split 101/214), I could still front these with a diagonal FG panel? Would this be advisable? 2"? 4"? 6" FG? Alternatively, I could put a super chuck triangular trap in front of the two panels (assuming 1/2" clearance and back of tri-trap is open)? Should I close of the space between the wall and the triangular FG so that there isn't a path for air to go around the FG? (maybe use metal duck tape to close the gap between the panel traps and the triangular FG frame?

5) Would you advise the above panel+FG configuration in the corner over a larger all super chuck corner trap? I assume answer would also apply to ceiling/wall boundaries.

6) Are there other panel options that I should consider. For instance would limp-mass MLV ring less or absorb better than plywood?

7) I'm looking at diffusors as well. If I'm sticking to say 6" build depth to keep the min distance to listener down to about 3' - and I build the cells with EPS filers, is it still reasonable to put anything behind this absorber wise? FYI - I'm thinking of diffusion on the left wall (maybe 9'Wx4'H - N23/I23 1D 5 periods) and leaving the masonry block wall live. I was thinking of splitting your panel traps to add the diffusor in on the right wall (2' Trap, 4' Diffuser, 2' Trap).

8) Given a diffusor on one side and a live wall on the other (like your studio video), how would you record a vocalist? Maybe gobo behind singer on live wall side, blumeline in front of singer with diffuser 3' behind it? (saw your video on recording in your warehouse)- understand you can have more mics - but trying to understand how depth from diffuser is going to be handled in my 12' wide room and how diffusor should interface with mics.

9) I've got 6' of book case on my rear wall. Was thinking of placing a diffuser in front of it (on wheels like a gobo) with an aborption panel below - diffuser 6'Wx4'H - N23/I23 1D 3 periods, 6'x2' FG absorber 6" Deep . Corners will still have panel traps and absorption. I was probably going to put a triangular FG trap above it on the ceiling wall boundary. Do you have any better suggestion for the book case situation? BTW - the gobo/diffuser ("diffugo"!) could be repositioned to combine with the side wall diffuser to make sort of an isolation area - assuming this would be a good thing for recording?

10) If I put some diffusion in my cloud (maybe 2' min distance criteria) and I'm trying to mic a drum kit - the overhead mic's will be too close to the difuser. I was thinking of something like a skyline down the middle of the cloud and FG absorbers on either side - then overhead mics could go up against the FG absorbers on either side. Maybe 8' ceiling is just to low to even consider diffuser? What about a scattering panel (something like RPG's radiator)? Mix with FG panels? Trying to ask if I should just cover the ceiling with FG absorption (maybe with panel traps behind or alternating as you have), or if scatting/diffusion would be advisable in some capacity - remember I'm trying to record here?

11) Would a scattering panel in front of the window be a good thing? (It currently has a wonderful view of my garage with a curtain in front of it - and yes if I used the garage for the live room, this room would make a great control room - but...)

12) In your ultimate studio - you didn't have any panel traps? Would you recommend a 6" FG trap over the panel Trap? Does the diffuser change the situation such that the panel traps are not necessary or didn't fit?

13) I can get 9.5 lbs of GreenFiber celuloid blown insulation for $10 in a 1.9 cuf package. I could spread this out in a panel to whatever density makes sense and retain with 1/4" square mesh. Would 4.5 lb/cuf be reasonable for say 4" or 6" depth. If so, one package gives me about 4 cuf - or at 4" depth, 12 sq feet of panel? Any reason not to use this as opposed to 4.5 lb/cuf rock wool (which is $23 for 12 sqft x 4").

14) Assuming I'm trying to avoid overly impacting on my mid/high absorption for recording purposes, any advice on what to install on first to try to treat and measure until things are "ok"?

15) I've looked some at VPRs with steel panels and it seems that most DIY's don't seem to have to much success. Also looked at Hemholtz resonators and they seem too hard to tune and place and are bulky for a small room - though I could get them in 3 of my corners or go through the window to the garage. Would you agree I'm better off to pass over these?

Sorry if this was a lot of questions - any advice would be most appreciated.

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#2747906 - 01/19/16 10:39 AM Re: Build a Better Bass Trap/Ultimate Studio - Questions [Re: devnull]
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Yes, that's a lot of questions, but I can dismiss several of them with one suggestion: As explained in my article, those wood panel bass traps are not a good choice for treating a room the size of yours. You'll do much better using thick FRK-type rigid fiberglass, along with non-FRK material for reflection points. If bass traps are a 8-12 inches thick you can use fluffy fiberglass. Otherwise use 703 or 705 for normal thickness panels.

Diffusion makes sense on the rear wall, but I'd definitely not have diffusers at reflection points on the side walls or the ceiling cloud.

(14) There's little risk of making a room this size too dead.

I'll save the rest until you post a drawing or 2-3 photos.

--Ethan

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#2752194 - 02/02/16 06:59 AM Re: Build a Better Bass Trap/Ultimate Studio - Questions [Re: Ethan Winer]
devnull Offline
Member

Registered: 01/18/16
Posts: 2
Thanks Ethan. Will do.

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#2753995 - 02/09/16 09:26 AM Re: Build a Better Bass Trap/Ultimate Studio - Questions [Re: Ethan Winer]
dboomer Offline
Member

Registered: 02/08/16
Posts: 21
Loc: SoCal
Originally Posted By: Ethan Winer
You'll do much better using thick FRK-type rigid fiberglass, along with non-FRK material for reflection points.



First I thank you for all the help you graciously donate to those of us who are a little lost on the subject. (i've spent the last 3 days reading most all of this forum)

Why will absorber type traps outperform membrane types in this room? I would have thought Membrane types would be more efficient at lower frequencies for a given "trap" size.

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#2754080 - 02/09/16 01:14 PM Re: Build a Better Bass Trap/Ultimate Studio - Questions [Re: dboomer]
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
In small rooms you can get peaks and deep nulls at all frequencies due to the unavoidable close proximity to the walls and ceiling. So some peaks and nulls are related to the room dimensions and are thus predictable, but you can have peaks and nulls at virtually any frequency. Tuned absorbers help only select frequencies, where broadband absorbers help at all frequencies.

--Ethan

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#2754118 - 02/09/16 02:57 PM Re: Build a Better Bass Trap/Ultimate Studio - Questions [Re: Ethan Winer]
dboomer Offline
Member

Registered: 02/08/16
Posts: 21
Loc: SoCal
I'm trying to understand ... are you saying it is more desirable (in a small room) to knock down a broad range of bass frequencies rather than focus on attenuating the big peaks? Or is it just easier for a novice to do?

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#2754298 - 02/10/16 10:45 AM Re: Build a Better Bass Trap/Ultimate Studio - Questions [Re: dboomer]
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
It's better to absorb all bass frequencies than only the few that relate to the rooms dimensions. This has nothing to do with which type of trap is easier to make, though fiberglass traps are also simpler and cheaper than wood panels traps.

--Ethan

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Moderator:  Ethan Winer