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Bass Trap design/specs to reduce 55Hz-100Hz
Bass Trap design/specs to reduce 55Hz-100Hz
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Old 8th August 2019, 12:51 AM   #1
Heifetz1000 is offline Heifetz1000
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Join Date: Mar 2014
Default Bass Trap design/specs to reduce 55Hz-100Hz

Hello,
Can anyone recommend a design for a bass trap that would reduce frequencies in the range 55Hz-1001Hz?
Perhaps a Tube Trap? What size would it need to be? How can the design and specs such as dimensions; insulation thickness/flow specs or distance from corners be required for this Tube Trap?

Are there any other possibilities?
thx so much,
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Old 25th September 2019, 03:11 PM   #2
turk 182 is offline turk 182  Canada
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so an entire octave of bass is too loud in your room? just how big is this room?
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Old 26th September 2019, 07:41 PM   #3
mushroommunk is offline mushroommunk  United States
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Location: Auburn Hills, Michigan
More than just an octave (x2), he's saying he has an entire decade(x10) that's wrong. Twice that even.

If it was 55 and a decade above that wouldn't surprise me, you're right in modal range, but all the way to 1000? Sounds to me like a setup or speaker issue.

I agree with Turk182, some measurements and more info on room size, equipment, and setup is in order.
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Old 30th September 2019, 06:00 PM   #4
turk 182 is offline turk 182  Canada
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i think the text of the post contains a typo...and yeah i could be wrong but the thread title seems more likely....but all is quiet from the OP.
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Old 30th September 2019, 11:35 PM   #5
Adhoc1 is offline Adhoc1
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It will be hard to make 1 absorber which covers the range 55 to 110 Hz, that's 1 octave. It needs to be very thick in that case, 300 mm / 12" and upwards.

In general, the lower in frequency the harder with a wide band in frequency (Hz). Think in wavelengths! 55 Hz = 6,25 m / 20,56 feet, 15 Hz down = 40 Hz and wave length is 8,60 m / 24,7 feet. Quite a difference! 110 Hz = 3,13 m / 10,3 feet. 15 Hz down and 95 Hz = 3,62 m / 11,9 feet. 15 Hz difference in both cases but the change in wave length is huge in comparison.

I would go for 2 helmholtz absorbers which preferably overlap in their effective absorbtion range. "Effective" I would see as absorbtion factor 0,8 and above. (0,5 means a change of 3 dB, not very much). If you look at your wave lengths it should be obvious they also need to be as large in length and width as is practicable for you. You don't influence a 6,25 m wave much or at all with a small object.

In general: Using a "thin" perforated plywood / MDF instead of a "thick" one tends to make the helmholtz more broadband but at the same time less effective at a certain frequency. There should an airgap between the backside of the plywood sheet and the insulation inside. Suitable air gap can be the same as the hole diameter or larger. It is advantageous for maximum absorbtion to compartmentalize the inside of the Helmholtz. Distance between holes should be a lot larger than the hole diameter. By combining hole diameter, length between holes, air gap and the airflow resistivity of the insulation inside you can "tailor make" your absorber for a certain frequency range. In the picture used airflow resistivity is 7000 Pa.s/mē. that would equate to the fluffiest most light weight attic insulation you can findd. A high airflow resistivity is not necessarily better, on the contrary often, but if total allowed thickness is small, say 50-100 mm / 2-4", one should go up in airflow resistivity, 20-30 000 could be better.

In enclosed picture there are 2 absorbers which almost overlap. On Multi-layer Absorber Calculator you can calculate with other dimensions. If you are using American units, calculate them to 2 decimals for entered mm-units. To turn out tuned as wanted versus theory it is very picky with measurements and construction. It should be an airtight box with a perforated facing sheet. If the box leaks, it will be as functinal as a punctured balloon, -no fun. Do not have a fabric close to the holes, that will restrict the airflow through the holes and the absorber may turn out useless. For widest broadband and highest absorbtion in combinations, you should strive for "medium damping". "High damping" will mean max absorbtion but within a narrow band of frequencies. "Low damping" is just that, low damping of the frequencies.
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Old 19th October 2019, 01:44 PM   #6
digitalthor is offline digitalthor  Denmark
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Quote:
Originally Posted by Heifetz1000 View Post
Hello,
Can anyone recommend a design for a bass trap that would reduce frequencies in the range 55Hz-1001Hz?
Perhaps a Tube Trap? What size would it need to be? How can the design and specs such as dimensions; insulation thickness/flow specs or distance from corners be required for this Tube Trap?

Are there any other possibilities?
thx so much,
Add a DSP - measure and correct.
If it should be really good - add minimum 2 subs


There's more - I simplified - obviously But building bass traps - will become huge and unpractical.
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Old 25th October 2019, 09:24 AM   #7
Solexine is offline Solexine
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Test to put two large teddy bears in the front corners. Say 1,5 meters high bears.
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Old 26th October 2019, 05:31 AM   #8
tizman is offline tizman  Canada
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Location: Toronto
A couple of full size StudioTips SuperChunks? That should be a good start. Easy to DIY too. Teddy bears in front of them should help with the lower growling frequencies. Seriously though, the Super Chunks are the direction I'm considering. Google it.

Last edited by tizman; 26th October 2019 at 05:33 AM.
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Old Yesterday, 02:21 PM   #9
Just Dave is offline Just Dave
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Default Bass Trap Design

To the OP: F. Alton Everest has a very good section on absorber design in "Master Handbook of Acoustics", including formulae. Also, although probably much harder to find, "Acoustical Designing in Architecture" by Vern Knudsen and Cyril Harris goes into good depth on the topic.
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