Corner Bass Traps - Always beneficial?

[Ethan Winer]

It is tempting for consumers to think that by merely putting a panel on the wall they have helped the bass response.

Good bass traps work well, as proven by the Before / After response and ringing I posted earlier in this thread. Those traps were in fact against the wall with no air gap. But you need more than one panel.

The issue there other than accommodating many of them is whether you have made the room too dead because you have substantial amount of absorption at higher frequencies now (and gotten rid of some beneficial reflections).

You really should learn the facts before criticizing the results of someone's products:

One big feature of RealTraps products is their large amount of absorption at very low frequencies, with intentionally less absorption at mid and high frequencies. The very specific curve of absorption versus frequency sets RealTraps apart from all other acoustic treatment manufacturers. This lets you put enough traps in a room to truly solve the problems in the bass range, but without making the room too dead sounding as can happen with panels made of foam or plain fiberglass. (We also have versions that absorb fully at mid and high frequencies when that's appropriate.)

I really hope this is the last time I have to explain this again.

I believe the measurement he has put forward is from his own living room

Again, even minimal reading reveals that all of those test results are from a certified acoustics lab.

I have to say, it gets tiring repeatedly correcting someone who can't be bothered to understand what he's criticizing.

--Ethan

 

[microstrip]

(...) I have to say, it gets tiring repeatedly correcting someone who can't be bothered to understand what he's criticizing.

--Ethan

Ethan,

Please do not take it as a criticism, but your answers (and most of the statements we find in the net from several other companies) are mostly qualitative or not fully defined. When you say "less than 100 Hz" this does not answer the questions of people who want to know the absorption at 35 Hz. Saying the answer is somewhere in a 10 minute video is not answering a question. I understand that manufacturers sometimes can not tell all the details in an open forum - surely I will not ask you to reveal the mechanical characteristics of the limp mass membranes used in your Magetraps.

BTW, the thread was just addressing the poor performance of pure porous bass absorber panels, without any type of membrane or air gap, and as far as I know RealTraps do not belong to this type of absorbers. My comments just addressed this first type of devices.

 

[NorthStar]

As I said earlier, this was a lot of treatment in a small room. Full details in this video:

Hearing is Believing

Again, you don't need that much treatment to make a real improvement below 100 Hz.

--Ethan

----- :b

Ethan,

Please do not take it as a criticism, but your answers (and most of the statements we find in the net from several other companies) are mostly qualitative or not fully defined. When you say "less than 100 Hz" this does not answer the questions of people who want to know the absorption at 35 Hz. Saying the answer is somewhere in a 10 minute video is not answering a question. I understand that manufacturers sometimes can not tell all the details in an open forum - surely I will not ask you to reveal the mechanical characteristics of the limp mass membranes used in your Magetraps.

BTW, the thread was just addressing the poor performance of pure porous bass absorber panels, without any type of membrane or air gap, and as far as I know RealTraps do not belong to this type of absorbers. My comments just addressed this first type of devices.

---- Still, videos are a good aid in the right direction, IMO. :b
Corner bass traps, panel bass traps, they all contribute to better sound, better balance (frequency response, time delay).
This is where measurements and listening goes well together.
{Listen well at all stages of room's treatments, including bass absorption, and take measurements each time.}

 

[Ethan Winer]

Please do not take it as a criticism, but your answers (and most of the statements we find in the net from several other companies) are mostly qualitative or not fully defined. When you say "less than 100 Hz" this does not answer the questions of people who want to know the absorption at 35 Hz.

Nobody knows exactly how much any bass trap absorbs at 35 Hz because no acoustics lab is certified to report absorption at such a low frequency. Most labs are certified down to 100 Hz, and a very few are certified down to 80 Hz. More to the point, showing Before / After data and stating the room size and number of traps gives a good indication of how much improvement people can expect in their own rooms. IMO this is even better than saying "each bass trap provides 5.2 sabins of absorption at 60 Hz" or whatever. I don't think most people could relate such numbers to how much the response and ringing will be improved.

Saying the answer is somewhere in a 10 minute video is not answering a question. I understand that manufacturers sometimes can not tell all the details in an open forum

I have very few secrets. But I already posted the Before / After data for the same measurements shown in the video. See my posts #30 and #38. I linked to the video only after I was asked for more detail.

BTW, the thread was just addressing the poor performance of pure porous bass absorber panels, without any type of membrane or air gap, and as far as I know RealTraps do not belong to this type of absorbers. My comments just addressed this first type of devices.

Even plain porous absorbers work better than the simulations I've seen posted here. As I often say, empirical evidence trumps theory every time.

--Ethan

 

[amirm]

Good bass traps work well, as proven by the Before / After response and ringing I posted earlier in this thread. Those traps were in fact against the wall with no air gap. But you need more than one panel.

A million pennies is also a lot of money but you need a darn big jar to hold them all . Read my post where I said people buy *a* panel and put them on the wall and expect it to do something. Fact that you have 11 of them (!) just in the front of room is not representative of how people will use these panels.

You really should learn the facts before criticizing the results of someone's products:

Ethan, please leave this tone of voice to other forums. This is WBF. We hold ourselves to a higher standard. As to your data point, the peak absorption in your product to its performance in bass is 7:1. If your problem is bass frequencies and you put enough of those on the wall to get sufficient response, you have 7X of that in higher frequencies that you did not intend to treat at all. Calling a product "bass trap" when 85% of its absorption is at higher frequencies is an oxymoron and pure marketing. This is the starting description of your mondotraps:

"MondoTraps and Corner MondoTraps offer more low frequency absorption than any other bass trap of its size." A product that is down to an alpha of just 0.15 at 70 Hz is not a "bass trap." It is not trapping much of anything at those frequencies.

I really hope this is the last time I have to explain this again.

Again? When did we discuss your specific product before? If we had, I would have given the above answer showing that your point did not have merit anyway.

I have quoted top experts in the industry with similar views. Shown simulations *which agreed* with your own data and you talk like some accusation was made without foundation?

Again, even minimal reading reveals that all of those test results are from a certified acoustics lab.

Certified lab did not put forward frequency response measurement of a room with a lot of absorbers in it as you mentioned. That was what my comment was referring to.

I have to say, it gets tiring repeatedly correcting someone who can't be bothered to understand what he's criticizing.

--Ethan

What's there to understand? That there is 80% marketing, 20% technical here? You honestly want to say Dr. Toole knows less than you? That the laws of physics changes in your shop? I know the science. If you want to demonstrate how velocity of sound is not zero at the wall, let's see that. And please focus on the technical matter than discussing me. If you are frustrated or angry, please take it elsewhere.

 

[Bill Hart]

Perhaps a dumb question, but when the issue of membranes in bass traps (or whatever you want to call them) came up, I was wondering if some sort of passive driver, like the sympathetic drivers that are used in some speaker systems, would work as a form of acoustic treatment. Couldn't those be tuned to effectively react to certain resonant frequencies with some degree of accuracy?

 

[JackD201]

Not a dumb question. Answer is yes it can be done. Not the most cost efficient thing in the world but the answer is yes all the same.

 

[Kal Rubinson]

Perhaps a dumb question, but when the issue of membranes in bass traps (or whatever you want to call them) came up, I was wondering if some sort of passive driver, like the sympathetic drivers that are used in some speaker systems, would work as a form of acoustic treatment. Couldn't those be tuned to effectively react to certain resonant frequencies with some degree of accuracy?

Something like this? http://www.msr-inc.com/downloads/pdf_files/080830_SprngTrp_Resi v2.pdf

 

[Bill Hart]

Something like this? http://www.msr-inc.com/downloads/pdf_files/080830_SprngTrp_Resi v2.pdf

Nice catch there, Kal. I'll look into those as possible adds for the next room.

 

[microstrip]

Perhaps a dumb question, but when the issue of membranes in bass traps (or whatever you want to call them) came up, I was wondering if some sort of passive driver, like the sympathetic drivers that are used in some speaker systems, would work as a form of acoustic treatment. Couldn't those be tuned to effectively react to certain resonant frequencies with some degree of accuracy?

Yes - a loudspeaker having a large bass speaker can be used as bass trap. Loading its output with resistors - a la Sonus Faber Extrema - will change the damping. But it is not optimized for this function.

As I went through some types of bass traps I got the impression that the membrane bass trap is the way to go for DIY. The best I tried in my room until today were the RPG modex corner, but they are very expensive. I am currently in the process of building some large area traps in the front wall, similar to those Bruce B. has in his studio.
The most critical point of the membrane bass trap is the tuning of the membrane. Curiously, although any of the tools that are used for DIY speaker measurement can be used for developing and fine tuning the bass trap membranes, there is little information about it available in the net. And most DIY users still go the brute force approach, buying enormous quantities of OC703.

Besides the F.A. Everest book, I have found that there is plenty of information, projects and debate at the Gearslutz forum

http://www.gearslutz.com/board/studio-building-acoustics/

and particularly

http://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/

 

[Bill Hart]

Yes - a loudspeaker having a large bass speaker can be used as bass trap. Loading its output with resistors - a la Sonus Faber Extrema - will change the damping. But it is not optimized for this function.

As I went through some types of bass traps I got the impression that the membrane bass trap is the way to go for DIY. The best I tried in my room until today were the RPG modex corner, but they are very expensive. I am currently in the process of building some large area traps in the front wall, similar to those Bruce B. has in his studio.
The most critical point of the membrane bass trap is the tuning of the membrane. Curiously, although any of the tools that are used for DIY speaker measurement can be used for developing and fine tuning the bass trap membranes, there is little information about it available in the net. And most DIY users still go the brute force approach, buying enormous quantities of OC703.

Besides the F.A. Everest book, I have found that there is plenty of information, projects and debate at the Gearslutz forum

http://www.gearslutz.com/board/studio-building-acoustics/

and particularly

http://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/

Obrigado, Micro. Are Bruce B's area traps shown on this forum?

 

[edorr]

Best thing to do is measure with REW and find the peaks and pull them down with a DSP. That will get rid of boominess. Filling in the gaps can be done with better placement of speakers or addition of subs.

Edit: I noticed you have trinnov. Let it optimize the bass. Corner bass traps are not a whole lot more efficient than above because again, they are working against the laws of physics.

As I was thinking through my calibration strategy I had this thought. The Evolution MM3's have active woofers with adjustable volume. Since jacking up nulls with room correction is harder (some say undesirable/impossible) than pulling down peaks, would it be advisable to set volume of the woofer units at say 5db higher volume than the mid/high section of the speaker? This would decrease the size of any nulls, and make life easier for the Trinnov DRC. Keep in mind that my target curve has an 5db boost (smoothing out at 120Hz) of the lows anyway, so the need to pull down any peaks resulting from the boost may be limited. Any comments?

 

[RBFC]

As I was thinking through my calibration strategy I had this thought. The Evolution MM3's have active woofers with adjustable volume. Since jacking up nulls with room correction is harder (some say undesirable/impossible) than pulling down peaks, would it be advisable to set volume of the woofer units at say 5db higher volume than the mid/high section of the speaker? This would decrease the size of any nulls, and make life easier for the Trinnov DRC. Keep in mind that my target curve has an 5db boost (smoothing out at 120Hz) of the lows anyway, so the need to pull down any peaks resulting from the boost may be limited. Any comments?

My understanding of "jacking up nulls" with room correction is that you can easily overdrive the amplifier(s) that run your bass. Whether you turn up your woofers via their own control or via the RC, you will still be asking for a great deal more power to the bass drivers.

Lee

 

[dallasjustice]

As I was thinking through my calibration strategy I had this thought. The Evolution MM3's have active woofers with adjustable volume. Since jacking up nulls with room correction is harder (some say undesirable/impossible) than pulling down peaks, would it be advisable to set volume of the woofer units at say 5db higher volume than the mid/high section of the speaker? This would decrease the size of any nulls, and make life easier for the Trinnov DRC. Keep in mind that my target curve has an 5db boost (smoothing out at 120Hz) of the lows anyway, so the need to pull down any peaks resulting from the boost may be limited. Any comments?

IME, that's what I've found. If you have powered subs, it's much better to just turn the volume knob up on the powered sub and then use DRC to take down peaks where needed than it is to apply gain via DRC to the nulls. Nyal can come in here if he wants, but I believe he also told me once that nulls caused by room boundaries cannot be fixed with DRC.

 

[edorr]

My understanding of "jacking up nulls" with room correction is that you can easily overdrive the amplifier(s) that run your bass. Whether you turn up your woofers via their own control or via the RC, you will still be asking for a great deal more power to the bass drivers.

Lee

It was my undestanding that the hardware risk associated with "jacking up nulls" is the speaker not the amp. You need to feed the speaker far more power within a small frequency range to get the volume up, potentially overdriving it. I'm pretty ignorant in the issue though, so may be one of the pro-luminaries can elobrate.

 

[edorr]

It stands to reason that most of the additional acoustic energy at a certain frequency gets cancelled out, it is very hard to jack up a null. However, I boost a null by 6db with Trinnov in my current setup without any problems, and with great sonic benefit. Nulls of the 20db variety are probably the real problem here.

 

[amirm]

As I was thinking through my calibration strategy I had this thought. The Evolution MM3's have active woofers with adjustable volume. Since jacking up nulls with room correction is harder (some say undesirable/impossible) than pulling down peaks, would it be advisable to set volume of the woofer units at say 5db higher volume than the mid/high section of the speaker? This would decrease the size of any nulls, and make life easier for the Trinnov DRC. Keep in mind that my target curve has an 5db boost (smoothing out at 120Hz) of the lows anyway, so the need to pull down any peaks resulting from the boost may be limited. Any comments?

I would think that it would do so on its own. That is what JBL Synthesis ARCOS does:

You see two faint lines. One is the original levels. The elevated one is after the correction boosted levels prior to pulling down the peaks. Of course you need to have speakers that can handle the increased levels.

 

[edorr]

You see two faint lines. One is the original levels. The elevated one is after the correction boosted levels prior to pulling down the peaks. Of course you need to have speakers that can handle the increased levels.

Interesting. It looks like the Trinnov may be doing the same. As you notice, the 12Db dip at 35Hz is lifted by about 6db, the 7db dip at 60Hz also goes up to 1db.

 

[Gregadd]

Ironic? After accusing so many others of selling Snake Oil, it's annoying to have someone refer to your product as "Snake Oil." Remember incompetence trumps corruption. A person is more likely to be wrong than dishonest.

 

[Ethan Winer]

Ethan, please leave this tone of voice to other forums. This is WBF. We hold ourselves to a higher standard.

Amir, I have never publicly suggested that you are incompetent. I believe others have explained the problem to you privately, so let's leave it at that.

--Ethan