John Sayers' Recording Studio Design Forum

Speak now or forever live with not voicing your opinion:



Attached is a sketch to accompany this description of the proposed test.


Test 1: reference wall 1

5/8" drywall
2x4 studs 24" OC, R13 fiberglass
5/8" drywall



Test 2: reference wall 1 with panel traps added per ethans basic designs, including the "high bass trap"

5/8" drywall
2x4 studs 24" OC, R13 fiberglass
5/8" drywall
Ethan panel trap recommendations


Test 3: repeat of 2, sans high bass trap


Test 4: reference wall 1 with panel traps tuned to lower frequencies added
5/8" drywall
2x4 studs 24" OC, R13 fiberglass
5/8" drywall
Low frequency panel traps


Test 5: repeat of test 4 with a second layer of drywall added to the non-trap side, and both layers of drywall on the non-trap side not attached to the structure

so

5/8" drywall
5/8" drywall
no attachment to studs
2x4 studs 24" OC with R13 fiberglass
5/8" drywall
low-frequency panel traps

Test 6: repeat of test 5 with low frequency traps unsealed


Test 7: repeat of 5 and 6 with Ethans traps


Test 8: repeat of 5 and 6 with no traps, as a second reference, so:

5/8"
5/8"
no attachment to studs
2x4 studs 24" OC with R13 fiberglass
5/8" drywall



This protocol is subject to change at my discretion. That is an ambitious and potentially time consuming set of tests. The tests are competing with some important-to-GG Company work, and some possibility that the entire test protocol cannot be done exists.

It seems very clear to me that part of how destructive panel traps will be to TL relates to the rleative locations of the resonances in the wall and the reosnances in the traps, and as such it is necessary to add the lower frequency traps as well. I presume that <100hz panel traps are not uncommon anyway. And further, the potential for contesting whatever results arise from the test almost mandate a broader set of tests lest whatever 1 or 2 tests are run wind up of use to nobody and simply the subject of additional debate.

Low frequency trap shall consist of 3.5" deep cavity with R13 fiberglass insulation and double 5/8" drywall.

_________________
Technical director, Green Glue Company
(Audio Alloy)
All posted content copyright Brian Ravnaas or Green Glue Company except as noted and may not be reproduced without permission.

Brian,

Is it possible to use a distance keeper to keep the wool away from the front panel of the trap?

In your case you build the horizontally, which makes this probably a bit annoying.

That's how it explicit adviced in this trap design of Ethan. Keeping the wool spaced from the front panel.

Brian, this indeed should be nice work, and even when it doesn't work out as itended or planned due to lack of time, energy or whatever, many thanks for this more than generous offer.

_________________
Best regards - Eric Desart
My posts are never meant to sell whatever incl. myself, neither direct, nor indirect.

well, i will get as much of it done as is at all possible.

alot of those changes will only take 10 minutes or so, and would allow a fairly rapid re-test.

i willt ry to space the insulation away, is a simple thumbtack or two an acceptable method of doing this.

_________________
Technical director, Green Glue Company
(Audio Alloy)
All posted content copyright Brian Ravnaas or Green Glue Company except as noted and may not be reproduced without permission.

Brian,

> That is an ambitious and potentially time consuming set of tests. <

No kidding - I still can't believe you're willing to do this! Outstanding!!!!



> Low frequency trap shall consist of 3.5" deep cavity with R13 fiberglass insulation and double 5/8" drywall. <

The design calls for one inch thick 703 rigid fiberglass. For the purposes of these tests I imagine fluffy fiberglass would be okay, but in that case you should make it two or even three inches thick instead of only one inch. Even three inches will fit in a 3.5 inch cavity, and will still leave enough clearance to not touch the vibrating front panel.

--Ethan

_________________
The acoustic treatment experts
Buy my DVD

Maybe it's just too late or I'm just blind but what's the diff between test 1

and 3?

Also, if TL is a large concern, I'd suspect that most folk would use the double 5/8" as the backing - potentially even with a 3/4" MDF backer on the 'trap'.

I know you can't test everything - just trying to simulate the reality that most folks would encounter. Besides, if I don't bitch now, I have no future right to

Bryan

_________________
I am serious..... and don't call me Shirley

www.gikacoustics.com

Bryan,

test 1 has no traps, test 3 has panel traps but not the all-fibrous "high bass" trap. On studiotips, Rod Gervais hypothesized that the high bass trap and its effect on TL should be determined so its included once. My guess is that it won't do much of anything for TL, so if that proves to be true it won't be included on other tests, leaving some "regular" wall space.


Ethan,

when i said "deep bass" trap, i meant one even deeper, tuned to 50hz or so. It is important in my estimation to model a trap with resonance NOT IN LINE WITH that of the walls. This should be in line with the decoupled wall, but not the other wall, giving a broader perspective.


All,

we're building those suckers tonight, and i'll post pictures if i can.

_________________
Technical director, Green Glue Company
(Audio Alloy)
All posted content copyright Brian Ravnaas or Green Glue Company except as noted and may not be reproduced without permission.

Brian,

> when i said "deep bass" trap, i meant one even deeper, tuned to 50hz or so. It is important in my estimation to model a trap with resonance NOT IN LINE WITH that of the walls. This should be in line with the decoupled wall, but not the other wall, giving a broader perspective. <

Excellent. More information is always better than less.

--Ethan

_________________
The acoustic treatment experts
Buy my DVD

Brian,

My best guess is the same as yours - I don't believe it will have any effect - or such a small effect as to be almost unmeasurable.

But - I am one who always hates unanswered questions - so I figure if we build them like this - we should test them like this.

with fluffy fiberglass insulation the thumbtacks won't do much good - the glass will just form around them - and if you have enough tacks so that doesn't happen - then the glass will effectively damp the panel.

If you want to use the fluffy stuff - perhaps you would be better off using some nylon strapping to hold the glass at least an inch from the panel - you could just staple it (the strapping that is) to the sides of the frame.

I hope that helped.

Sincerely,

Rod

_________________
Ignore the man behind the curtain........

hey Rod, 10-4 on your logic and i think its sound. I just would rather run the tests w/o the absorption in one of the rooms as the standard advises against high absorption rooms. But its a good idea.

I am having trouble finding 703 here in Fargo, and could not find any on Friday.

Any suggestions?

_________________
Technical director, Green Glue Company
(Audio Alloy)
All posted content copyright Brian Ravnaas or Green Glue Company except as noted and may not be reproduced without permission.

Brian,

> I am having trouble finding 703 here in Fargo, and could not find any on Friday. <

Mineral wool? High-quality non-sculpted acoustic foam?

--Ethan

_________________
The acoustic treatment experts
Buy my DVD

Brian,

If we have it in one test then it establishes a baseline to measure against.

Past that point I can't see why we would need it.



Try using
Johns Manville Linacoustic - it's 3pcf material as well.

You should be able to get it here:

Macarthur Company
1449 43rd St W,
Fargo, ND, 58102
Phone:(701) 282-8181

Sincerely,

Rod

_________________
Ignore the man behind the curtain........

Thanks Brian - figured I was just having a senior moment.

Looking forward to the results.

Bryan

_________________
I am serious..... and don't call me Shirley

www.gikacoustics.com

that's awesome, rod!

its on the schedzule for tomorrow, i'll call those guys in the AM and post pics if possible.

_________________
Technical director, Green Glue Company
(Audio Alloy)
All posted content copyright Brian Ravnaas or Green Glue Company except as noted and may not be reproduced without permission.

No probs Brian, it was my pleasure.

I look forward to the results,

Sincerely,

Rod

_________________
Ignore the man behind the curtain........

got the goods at the place rod mentioned.

and even better, they had 703 on hand. so we're all set.

pictures soon!

_________________
Technical director, Green Glue Company
(Audio Alloy)
All posted content copyright Brian Ravnaas or Green Glue Company except as noted and may not be reproduced without permission.