Very Low Freqs bass trap material and dimensions advice required

[Throttler]

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 ?

[Lemonsqueezer]

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.

[Throttler]

6 out of 8 corners are treated. the sub is somewhere in the middle of the front wall.

how bout material and thickness specs?

[Lemonsqueezer]

How exactly are the corners treated?

[Throttler]

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?

[Lemonsqueezer]

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.

[Glenn Kuras]

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

[Lemonsqueezer]

Good the professionals here.

I should have asked about the monitoring position.

[Throttler]

Originally Posted by Lemonsqueezer

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.

[Throttler]

Originally Posted by Glenn Kuras

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.

[Throttler]

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

[Brainchild]

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?

...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.

[Glenn Kuras]

Originally Posted by Brainchild

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

[Glenn Kuras]

Originally Posted by Lemonsqueezer

Good the professionals here.

I should have asked about the monitoring position.

No worries about not asking.

Glenn

[Throttler]

Thanx everyone for the responses here. I will start upgrading soon.

P.S. anyone knows where I can find 705 in Europe ?

[Tomer1]

To treat 50hz you should look into helmotz or membrane.

[Lemonsqueezer]

Originally Posted by Tomer1

To treat 50hz you should look into helmotz or membrane.

I personally agree, but only after broadband treatment has been completed.

[Weasel9992]

Originally Posted by Throttler

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

[Tomer1]

Originally Posted by Lemonsqueezer

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.

[Lemonsqueezer]

Originally Posted by Tomer1

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?

[Brainchild]

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.

[BadJones]

Originally Posted by Brainchild

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

[Weasel9992]

Originally Posted by Brainchild

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

[Throttler]

ok, new place from scratch...

[Lemonsqueezer]

!!!

[Lemonsqueezer]

Do you not have the room response to post up?

[Throttler]

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.

[Lemonsqueezer]

It's not my room so it doesn't matter to me

A picture paints a thousand words.

[Pelonis]

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 ´™ <-(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.

[Tomer1]

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.