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Very Low Freqs bass trap material and dimensions advice required
Old 4th February 2009
  #1
Gear Maniac
 
🎧 10 years
Very Low Freqs bass trap material and dimensions advice required

Hi everyone.
I wanna build a bass trap for my subwoofer and mount it on the wall on it's back. Room is already treated but I still have some small phase issues at 50Hz on my sweetspot. I think building a bass trap right on the back of it would help.

I understand that
Owens-Corning 705-FRK maybe the best material and 6 or more inches with one more inch air in the back may do the trick.

Any more suggestions or advice on this one ?

Old 4th February 2009
  #2
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
Bass traps generally work best in corners where the modal resonances build up the most. And it quite likely that you would need more than one trap.
Old 4th February 2009 | Show parent
  #3
Gear Maniac
 
🎧 10 years
6 out of 8 corners are treated. the sub is somewhere in the middle of the front wall.

how bout material and thickness specs?
Old 4th February 2009 | Show parent
  #4
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
How exactly are the corners treated?
Old 4th February 2009 | Show parent
  #5
Gear Maniac
 
🎧 10 years
6 corners filled with Auralex cubes, all I could afford. room and full front wall also treated, bass is clear-not single noted-, image width and height (ceiling also has 2 clouds) all good for my purposes. I have no ring effects whatsoever, no flutter and no apparent resonance at moderate playback levels, just a small dip due to some phase issues at around 50hz. this is what I'm interested in fixing. I tried moving around lifting it up and changing phase of the sub, but nothing. sub is sitting on a "great gramma", is turned around 25 degrees and is 60 cms left from the middle of the room. for some reason Focal suggests placing it at a corner, sounds crap there, moved it back where it loved, put the cube back in the corner.


how bout material and thickness specs?
Old 4th February 2009 | Show parent
  #6
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
I would say that the Auralex cubes that you are using are not very effective, especially at 50Hz. I take it one of the rooms dimensions is around 11ft?

Anyway just look at the super corner chunks or panels of 6" thick Fibre/mineral board.

This thread shows you a design for panels.
Old 4th February 2009 | Show parent
  #7
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
What is the size of the room and how are you set up?

YES putting 6" bass traps on the back wall WILL help, as there is generally some pretty nasty nulls and peaks coming from that area. If you can space it off the wall further, I would do so. 50hz is a pretty hard to hit, with must DYI projects.

Glenn
Old 4th February 2009 | Show parent
  #8
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
Good the professionals here.

I should have asked about the monitoring position.
Old 4th February 2009 | Show parent
  #9
Gear Maniac
 
🎧 10 years
Quote:
Originally Posted by Lemonsqueezer ➑️
I would say that the Auralex cubes that you are using are not very effective, especially at 50Hz. I take it one of the rooms dimensions is around 11ft?

Anyway just look at the super corner chunks or panels of 6" thick Fibre/mineral board.

This thread shows you a design for panels.
I've read the entire thread, and I know my corners can be improved, but for now I need some absorption for the FIRST reflection, right back of the sub.
Old 4th February 2009 | Show parent
  #10
Gear Maniac
 
🎧 10 years
Quote:
Originally Posted by Glenn Kuras ➑️
What is the size of the room and how are you set up?

YES putting 6" bass traps on the back wall WILL help, as there is generally some pretty nasty nulls and peaks coming from that area. If you can space it off the wall further, I would do so. 50hz is a pretty hard to hit, with must DYI projects.

Glenn
Room is an 18*15*10. Bass trap will be placed behind the sub on the front wall. When I spaced it off the front wall the frequencies went nuts and unfortunately it was the best position I could find. I know 50 Hz is hard to hit, that's why I asked specific help on dimensions and material. Any suggestion welcome.
Old 4th February 2009 | Show parent
  #11
Gear Maniac
 
🎧 10 years
Mixing position is at 38% of the front to back right in the middle and speakers are placed in the equilateral triangle angles with a 4' side.

Any suggestion welcome
Old 4th February 2009 | Show parent
  #12
Lives for gear
 
🎧 10 years
Quote:
Room is already treated...6 out of 8 corners are treated...6 corners filled with Auralex cubes...room and full front wall also treated...
I daresay your room is not, in fact, treated. When you say "room and front wall also treated," what are you using other than the Auralex cubes?

Quote:
...for now I need some absorption for the FIRST reflection, right back of the sub...
From a factual standpoint, you don't. There's no significant first-reflection phase cancellation at 50Hz unless your sub is at least several feet away from the wall. Your problem is the result of room mode resonance, not the wall behind the sub.

Your best bet is probably going to be to follow the generally accepted practices repeated ad infinitum on this board: get rid of the Auralex and replace it with 6" of 705. If you still have a problem after that, you could look at getting into some tuned-trap-style shenanigans.
Old 4th February 2009 | Show parent
  #13
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Quote:
Originally Posted by Brainchild ➑️
I daresay your room is not, in fact, treated. When you say "room and front wall also treated," what are you using other than the Auralex cubes?

From a factual standpoint, you don't. There's no significant first-reflection phase cancellation at 50Hz unless your sub is at least several feet away from the wall. Your problem is the result of room mode resonance, not the wall behind the sub.

Your best bet is probably going to be to follow the generally accepted practices repeated ad infinitum on this board: get rid of the Auralex and replace it with 6" of 705. If you still have a problem after that, you could look at getting into some tuned-trap-style shenanigans.
spot on
Old 4th February 2009 | Show parent
  #14
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Quote:
Originally Posted by Lemonsqueezer ➑️
Good the professionals here.

I should have asked about the monitoring position.
No worries about not asking.

Glenn
Old 5th February 2009 | Show parent
  #15
Gear Maniac
 
🎧 10 years
Thanx everyone for the responses here. I will start upgrading soon.

P.S. anyone knows where I can find 705 in Europe ?
Old 5th February 2009 | Show parent
  #16
Lives for gear
 
🎧 15 years
To treat 50hz you should look into helmotz or membrane.
Old 5th February 2009 | Show parent
  #17
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
Quote:
Originally Posted by Tomer1 ➑️
To treat 50hz you should look into helmotz or membrane.
I personally agree, but only after broadband treatment has been completed.
Old 5th February 2009 | Show parent
  #18
Lives for gear
 
Weasel9992's Avatar
 
🎧 15 years
Quote:
Originally Posted by Throttler ➑️
Room is an 18*15*10. Bass trap will be placed behind the sub on the front wall. When I spaced it off the front wall the frequencies went nuts and unfortunately it was the best position I could find. I know 50 Hz is hard to hit, that's why I asked specific help on dimensions and material. Any suggestion welcome.
Everybody's right, of course. It'd be great if a couple of 705 panels would solve this 50Hz issue, but they won't. This will require some doing, and the first thing to start with is the room as a whole. After that, then Tomer's suggestion of a tuned absorber comes into play. If you don't do it this way you'll probably end up chasing your tail, spending a bunch of money and not solving the problem.

Frank
Old 5th February 2009 | Show parent
  #19
Lives for gear
 
🎧 15 years
Quote:
Originally Posted by Lemonsqueezer ➑️
I personally agree, but only after broadband treatment has been completed.
If you have a large space with high ceiling then sure,
But most pre-existing rooms converted into small project studio dont have have the laxury to built 8-10` broadband panels which allows for .6 absorption efficiency as low as 70hz.

For 50hz you can also go with a perforated panel which is rather easy to build and inexpenssive,
the Important thing is to recognize the exact resonate freq and which mode is involved (axial,tang,etc...) so you can possition the device at the most optimal spot.
Old 5th February 2009 | Show parent
  #20
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
Quote:
Originally Posted by Tomer1 ➑️
If you have a large space with high ceiling then sure,
But most pre-existing rooms converted into small project studio dont have have the laxury to built 8-10` broadband panels which allows for .6 absorption efficiency as low as 70hz.
.
Oh I don't have a large space with a high ceiling. Should I not bother making any broadband absorbers then?
Old 5th February 2009 | Show parent
  #21
Lives for gear
 
🎧 10 years
I'm a fan of the sublime elegance of resonant absorbers.

Something tells me that the o.p.'s room has not been evaluated to the necessary level of detail to warrant any kind of tuned absorption, however. At the very least, the room should be fully measured first. I'm positive a 50Hz null is not the only problem with the room.

It's a safe bet that numerous resonators tuned to a variety of frequencies would be needed, eating up a lot of real estate in the process. Then, once all the problem low frequencies are targeted, there is still bound to be a lot of unevenness between resonant frequencies (and higher up the spectrum). To say nothing of imaging issues, etc., at higher frequencies. Porous absorption would go a long way to alleviate those problems.

On top of those considerations, resonant absorbers require precise craftsmanship in order to be even marginally effective. I personally see them as either a last-resort method for mopping up major bass problems, or part of a no-holds-barred full-scale integrated studio build/design.

Panel absorbers may make more sense, but they have to cover a large amount of area in order to be effective. They may not protrude a full 6" into the room (though probably not much less than that), but they will shrink the room dimensions on all sides if they're going to be adequate for significant bass correction.

Porous absorption is always a good idea for every small environment. It's also necessary regardless of whether you use tuned traps or not.
Old 5th February 2009 | Show parent
  #22
Lives for gear
 
🎧 10 years
Quote:
Originally Posted by Brainchild ➑️
I'm a fan of the sublime elegance of resonant absorbers.

Something tells me that the o.p.'s room has not been evaluated to the necessary level of detail to warrant any kind of tuned absorption, however. At the very least, the room should be fully measured first. I'm positive a 50Hz null is not the only problem with the room.

It's a safe bet that numerous resonators tuned to a variety of frequencies would be needed, eating up a lot of real estate in the process. Then, once all the problem low frequencies are targeted, there is still bound to be a lot of unevenness between resonant frequencies (and higher up the spectrum). To say nothing of imaging issues, etc., at higher frequencies. Porous absorption would go a long way to alleviate those problems.

On top of those considerations, resonant absorbers require precise craftsmanship in order to be even marginally effective. I personally see them as either a last-resort method for mopping up major bass problems, or part of a no-holds-barred full-scale integrated studio build/design.

Panel absorbers may make more sense, but they have to cover a large amount of area in order to be effective. They may not protrude a full 6" into the room (though probably not much less than that), but they will shrink the room dimensions on all sides if they're going to be adequate for significant bass correction.

Porous absorption is always a good idea for every small environment. It's also necessary regardless of whether you use tuned traps or not.
What he said thumbsup
Old 5th February 2009 | Show parent
  #23
Lives for gear
 
Weasel9992's Avatar
 
🎧 15 years
Quote:
Originally Posted by Brainchild ➑️
I'm a fan of the sublime elegance of resonant absorbers.

Something tells me that the o.p.'s room has not been evaluated to the necessary level of detail to warrant any kind of tuned absorption, however. At the very least, the room should be fully measured first. I'm positive a 50Hz null is not the only problem with the room.

It's a safe bet that numerous resonators tuned to a variety of frequencies would be needed, eating up a lot of real estate in the process. Then, once all the problem low frequencies are targeted, there is still bound to be a lot of unevenness between resonant frequencies (and higher up the spectrum). To say nothing of imaging issues, etc., at higher frequencies. Porous absorption would go a long way to alleviate those problems.

On top of those considerations, resonant absorbers require precise craftsmanship in order to be even marginally effective. I personally see them as either a last-resort method for mopping up major bass problems, or part of a no-holds-barred full-scale integrated studio build/design.

Panel absorbers may make more sense, but they have to cover a large amount of area in order to be effective. They may not protrude a full 6" into the room (though probably not much less than that), but they will shrink the room dimensions on all sides if they're going to be adequate for significant bass correction.

Porous absorption is always a good idea for every small environment. It's also necessary regardless of whether you use tuned traps or not.
Very well put.

Frank
Old 5th February 2009 | Show parent
  #24
Gear Maniac
 
🎧 10 years
ok, new place from scratch...
Old 5th February 2009 | Show parent
  #25
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
!!!
Old 6th February 2009 | Show parent
  #26
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
Do you not have the room response to post up?
Old 6th February 2009 | Show parent
  #27
Gear Maniac
 
🎧 10 years
does it matter? I'm reading the posts here and I'm thinking two options. Stick with that since whatever you may try you may still not get a result (see posts above), go to another place and design is from scratch.
Old 6th February 2009 | Show parent
  #28
Lives for gear
 
Lemonsqueezer's Avatar
 
🎧 10 years
It's not my room so it doesn't matter to me

A picture paints a thousand words.
Old 7th February 2009 | Show parent
  #29
Here for the gear
 
🎧 10 years
broadband

Tuning resonators is not really the best choice because there are many complexities in small rooms that create multiple occurrences. Because the cubic dimension is relatively small, simply adding furniture or people can shift things or ad additional occurrences.

Understanding LF and locating the "PRESSUREZONE"s Β΄™ <-(private joke...sorry) so they can be understood and treated is the first step. the typical crossover point from ray to wave acoustics in small rooms is typically around 400Hz-500Hz. This is where the absorption need to begin and carry on to the tonic frequency of the room.

Call Jeff Madison at RPG and ask about the Total Room solution and the traps that are implemented with that system.
Old 8th February 2009 | Show parent
  #30
Lives for gear
 
🎧 15 years
I don't see how foam (as thick as it can be) can help with sub 70hz nulls and peaks,even if your strategy is large surface area coverage and 30cm thick foam its still not going to help much when fighting against a 20db peak.

I believe every room should be looked into independently to maximize treatment effectiveness\minimize problems and spend your money wisely.

General absorption kits are fine if your on low budget,not willing to consult a professional and not willing to spend time learning the basics in order to treat your room correctly.
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