GIK Acoustics 244 Sound Panel Review

[Glenn Kuras]

Sorry if I wasn't being specific.

I didn't know that I wasn't allowed to ask questions concerning Glenns products, I just thought that since the thread was entitled "GIK Acoustics 244 review", and since I'm highly interested in them, I thought that I would ask some questions concerning them here.

Again, I apologize.

--Sincerely,

Vaughan,
Sorry I did not answer your question on the thread.. I got a email (which btw I totally respect) about talking about my product.. So with that said I can talk about anything to do with acoustics, but not about our product.. Yes YES YES this is a review of our product, but I have to let it stand on it own. I hope you do understand, but I have to respect Audioholics..
You may email me though..
Glenn

 

[HAA Acoustics]

Hello all, Gene asked me to jump in on this thread to throw my two cents worth in. For what it's worth, in my opinion these deep bass modes you're discussing are not a practical target for most bass traps. It's correct to point out the mild improvement in the lowest octave of bass but I'd be hesitant to give the DIY'rs who read this the impression that this is a significant improvement. That's not to say these panels don't work; I recommend integration of such treatments but primarily as a modifier of the effects of Speaker Boundary Interference Response (SBIR) and any strong modal resonances in the 80 to 1000 Hz range where the panels showed better effectiveness.

In the typical residential environment (especially if the WAF is an issue) bass traps begin to be so large to be effective that they begin upsetting the balance of high frequency reverberation in the room... not a good trade off; smooth bass for limited envelopment. Why not deal with the bottom two octaves of bass by the more effective approach of subwoofer/listener position/EQ utilizing a limited introduction of this type of treatment to help solve SBIR issues?

HAA

 

[Ethan Winer]

Vaughan,

> thank you for offering your advise on the matter. You can expect to get a PM from me. . .sometime. <

If you want my technical advice I'm glad to help. But please don't send me a PM or email. I prefer to answer in the public forum so the effort I put into answering can help others. This also lets others jump in and add more information I may have overlooked.

Best is probably to start a new thread with a relevant subject.

--Ethan

 

[Glenn Kuras]

Hello all, Gene asked me to jump in on this thread to throw my two cents worth in. For what it's worth, in my opinion these deep bass modes you're discussing are not a practical target for most bass traps. It's correct to point out the mild improvement in the lowest octave of bass but I'd be hesitant to give the DIY'rs who read this the impression that this is a significant improvement. That's not to say these panels don't work; I recommend integration of such treatments but primarily as a modifier of the effects of Speaker Boundary Interference Response (SBIR) and any strong modal resonances in the 80 to 1000 Hz range where the panels showed better effectiveness.

In the typical residential environment (especially if the WAF is an issue) bass traps begin to be so large to be effective that they begin upsetting the balance of high frequency reverberation in the room... not a good trade off; smooth bass for limited envelopment. Why not deal with the bottom two octaves of bass by the more effective approach of subwoofer/listener position/EQ utilizing a limited introduction of this type of treatment to help solve SBIR issues?

HAA

Yes bass traps like ours are much better from 80 hz and up and I would say that eqing below 50 hz is the right way to go if you have a problem in that area. But as Ethan said people a lot of times think they have big problems in the 40 hz area but it turns out that the problems are really in the 80 hz and above.
Also I do recommend when building bass traps that you use the facing to not over dampen the HF.. It will also act as a membrane, which helps more on the low end..

Glenn

 

[Ethan Winer]

> Gene asked me to jump in on this thread to throw my two cents worth in. <

Great, thanks. More expert opinions are always welcome.

But who are you?

> It's correct to point out the mild improvement in the lowest octave of bass but I'd be hesitant to give the DIY'rs who read this the impression that this is a significant improvement. <

I agree it's not practical to expect a big improvement from any "porous" absorber in the lowest octave from 20 to 40 Hz. However, some commercial products - like the subject of this review - are more effective below 100 Hz than the simple panels most people make using plain rigid fiberglass. But your main point is well taken. My only objection was to the suggestion that a panel four inches thick can't do anything useful below 250 Hz, which is clearly not the case.

> In the typical residential environment (especially if the WAF is an issue) bass traps begin to be so large <

This is a great point. It's like the joke "you can have any two of the three." You can have effective, small, and looks good, but not all three at once. In fact, strike "small" because a small bass trap that's effective is theoretically impossible to build. However large and attractive are not mutually exclusive. The key is to build the room slightly larger, apply the treatments, then build a false wall (often fabric) in front of the treatments. Most people are not willing to do this because of the expense and effort. But it's definitely possible.

> Why not deal with the bottom two octaves of bass by the more effective approach of subwoofer/listener position/EQ utilizing a limited introduction of this type of treatment to help solve SBIR issues? <

As best I've been able to determine, there's no one subwoofer or listener location that will yield a response even close to flat. Sure, some places are better than others. But mostly it's a trade-off: 60 Hz is great here, but now 40 Hz is missing. And 40 Hz is decent over there but now 55 and 72 Hz are ringing like crazy. And so forth.

As for EQ, this has been discussed a lot lately. The two main failings of EQ are it cannot raise a null by very much, and it doesn't reduce ringing like bass traps do. Ringing is the primary cause of the effect known as "one note bass," and it's at least as important as raw LF response. Another problem with EQ is that any improvement you get is valid for only one very small location.

--Ethan

 

[HAA Acoustics]

Sorry for appearing to be the phantom blogger. I'm Gerry Lemay, Director of the HAA. I chose to use the HAA signature because from time to time we may have other folks from our group jump in representing the Alliance. By the way we encourage presenting new techniques so we're not about dictating that our current doctrine is the only way to skin a cat. Our techniques are heavily weighed toward practicality in a non-audiophile home so we often are smoothing bass without the benefit of panels like these. When a dealer can add bass treatments the results are invariably better between 80 and 1000 Hz but it's the rare job indeed when a client will allow a sub-bass trap on the premises.

Flat response is highly unlikely using only one technique, but a combination of tools can be very effective. The vast majority of our members are working AV Installers who rarely are given a rectangular room much less an opportunity to use any traps as I mentioned. Our approach is to place listeners in acoustically similar regions (bass-wise) then go after the big dog modes with sub position and polish with EQ.

HAA

 

[gene]

> Gene asked me to jump in on this thread to throw my two cents worth in. <

Great, thanks. More expert opinions are always welcome.

But who are you?

HAA (Home Acoustics Alliance) is one of a select few organizations we endorse as authoritive experts in the field of acoustics. They offer training courses to dealers, installers and consumers in efforts to help improve system integration and education of sound acoustical principles.

 

[Glenn Kuras]

>Flat response is highly unlikely using only one technique, but a combination of tools can be very effective. The vast majority of our members are working AV Installers who rarely are given a rectangular room much less an opportunity to use any traps as I mentioned. Our approach is to place listeners in acoustically similar regions (bass-wise) then go after the big dog mode with sub position and polish with EQ.<

that really is to bad, because throwing bass traps into your mix (set up) will most defiantly make your job much easer..

Glenn

 

[gene]

that really is to bad, because throwing bass traps into your mix (set up) will most defiantly make your job much easer..

Using multiple even # of subs (ie. 2 or 4) correctly positioned also works wonders in creating a wider and more consistent listening area of smooth bass response. This is a technique most competent installers are using today which is also championed by the likes of Dr. Toole from Harman, THX and also discussed in HAA training courses.

 

[gene]

As for EQ, this has been discussed a lot lately. The two main failings of EQ are it cannot raise a null by very much, and it doesn't reduce ringing like bass traps do. Ringing is the primary cause of the effect known as "one note bass," and it's at least as important as raw LF response. Another problem with EQ is that any improvement you get is valid for only one very small location.

You are incorrect about EQ or more relevantly used minimum phase PEQ’s NOT reducing ringing.

Low-frequency room resonances behave as minimum-phase phenomena (Dr. Toole recently authored a paper on this that he submitted to AES). According to Dr. Toole, a parametric equalizer that matches the frequency and Q of a resonance can be used to reduce its amplitude and, thereby, it’s ringing. It is totally predictable, but it works only for a single listener. Filling sharp dips is contraindicated because these tend to be destructive interference holes, and not minimum-phase phenomena. As Dr. Toole points out, multiple subs solve two problems – generating similar bass for multiple listeners and attenuating (i.e. damping) the resonances, reducing the need for EQ.

 

[Glenn Kuras]

Using multiple even # of subs (ie. 2 or 4) correctly positioned also works wonders in creating a wider and more consistent listening area of smooth bass response. This is a technique most competent installers are using today which is also championed by the likes of Dr. Toole from Harman, THX and also discussed in HAA training courses.

Hey I can not say that you are wrong... If done right then multiple numbers of subs, if placed right can help. But it is only going to help in a very small area... Meaning if you then move your head a foot the response will change.. So what are you going to do about multiple setting?
Just today I finished a studio here in town.. They had things set up really well but if you moved your head 6 inches the bass was totally different.. After we finished the room it gave a much wider response throughout the room.. Actually the guy tried to huge me after he was so happy...
I think the key to a great room is many things.. Maybe multiple subs, maybe eq, but to say that a room with bad acoustics is going to sound good is really a stretch..
Now with all that said, please do not take what I am saying as “if you do not treat your room then you are a loser”, but if you are dedicated to great sound then room acoustics are a HUGE part of it… Everything has its place..

Glenn

 

[Vaughan Odendaa]

Glenn, I respect your reasons completely and I understand. Now, where are the pictures, guys ? I need to see more of those white panels !

--Sincerely,

 

[Ethan Winer]

Hi Gerry,

> I'm Gerry Lemay, Director of the HAA <

Ah, much better!

> it's the rare job indeed when a client will allow a sub-bass trap on the premises. <

I understand that, and I fight the same battles every day. It kills me that people will spend the kind of money they do on expensive loudspeakers and other gear, when their entire investment goes down the drain as soon as they put it in an un- or under-treated room. But I do know all about WAF.

What bothers me more than anything is that most of these people don't even know what they're missing. Many times in my career as an audio pro I've had someone say, "Listen to how great my stereo sounds." And all I can do is smile and pretend to agree.

--Ethan

 

[gene]

Hey I can not say that you are wrong... If done right then multiple numbers of subs, if placed right can help. But it is only going to help in a very small area... Meaning if you then move your head a foot the response will change.. So what are you going to do about multiple setting?

Glenn you should do some reading on this topic if you haven't already. I suggest some of the white papers on Harman's website and some of their contributions to AES. I never said there is no need to treat a room but the benefits of multiple subs for increased modal control over a wider listening area are far greater than you may realize.

Here is an article we did on the topic which isn't nearly as comprehensive as the stuff done by Toole/Olive:

Place for Bass

 

[gene]

I understand that, and I fight the same battles every day. It kills me that people will spend the kind of money they do on expensive loudspeakers and other gear, when their entire investment goes down the drain as soon as they put it in an un- or under-treated room. But I do know all about WAF.

Even more sad when they dump $1000's on cables as a promised cure all for their sound problems

 

[Ethan Winer]

Gene,

> Using multiple even # of subs (ie. 2 or 4) correctly positioned also works wonders in creating a wider and more consistent listening area of smooth bass response. <

Understood. But only below 80 Hz or so, depending on room size and of course the sub crossover frequency. So I agree that multiple subs are great if you can afford it. (My one sub cost $2,000 and I'm not about to buy three more!) Then when you add bass traps you really have something to write home about.

> You are incorrect about EQ or more relevantly used minimum phase PEQ’s NOT reducing ringing. Low-frequency room resonances behave as minimum-phase phenomena (Dr. Toole recently authored a paper on this that he submitted to AES). According to Dr. Toole, a parametric equalizer that matches the frequency and Q of a resonance can be used to reduce its amplitude and, thereby, it’s ringing. It is totally predictable <

Yes, I know the theory and this too has been discussed endlessly. Please forgive the link to my site, but you may find THIS direct comparison of bass traps versus EQ interesting. It's a huge web page with 2.5 MB of graphs and photos, so I'll give you the conclusion here:

Contrary to the claims of EQ proponents, an expert in the field was not able to reduce ringing even a little, and in fact his attempt to bring up a few nulls caused the ringing to become worse. In fairness, in the follow-up discussion at AVS another expert pointed out that the first expert did a poor job of setting the EQ. I then asked the second expert to show that he can do a better job and reduce ringing by a meaningful amount. That was months ago and I've never heard further.

> it works only for a single listener. <

Bingo. And the "correction" is so localized it doesn't even work for both ears at the same time! If you view the graphs on the above page, look especially at the first two showing the untreated room (no traps, no EQ) at the listening position and also four inches to the right. My ears are seven inches apart. I may have a big head, but not dimensionally! So for a normal adult the change from one ear to the other will be even greater.

Only four inches away, and even at frequencies as low as 40 Hz, there's a very noticeable change in the response. So there's no way one EQ setting could correct the response for both ears, let alone provide the incredibly critical balance need to reduce ringing. I do understand that in theory it might be possible to reduce ringing. But only in an ivory tower, not in the real world or for two ears at the same time. Let alone for you and the person next to you on the couch. I have seen Floyd Toole's oscilloscope display showing ringing being reduced. What Floyd doesn't show is what happens when the measuring microphone is moved an inch or three, and he doesn't say how many hours it took him to set the EQ. In fact, such a high precision is needed to counter ringing I bet it would quickly drift out of whack over time and/or with small temperature changes.

--Ethan

 

[gene]

Contrary to the claims of EQ proponents, an expert in the field was not able to reduce ringing even a little, and in fact his attempt to bring up a few nulls caused the ringing to become worse. In fairness, in the follow-up discussion at AVS another expert pointed out that the first expert did a poor job of setting the EQ. I then asked the second expert to show that he can do a better job and reduce ringing by a meaningful amount. That was months ago and I've never heard further.

Your "expert" clearly wasn't expert. Trying to fill cancellation holes will INEVITABLY lead to problems. That is one of the first thing real experts learn, from experience if not from theory. You Don't BOOST NULLS!

And at low frequencies, where wavelengths are very long (about 22 feet at 50 Hz), a few inches make little difference unless one is near a narrow interference dip or null. Even then it will affect only a very narrow range of frequencies. The notions of a need for great precision and thermal stability are far fetched at best.

I suggest you sit in on one of Dr. Toole's classes at CEDIA as his course covers this topic very well.

(My one sub cost $2,000 and I'm not about to buy three more!) Then when you add bass traps you really have something to write home about.

Two or even four decent less expensive subs properly placed in the room can be way more rewarding than a single overpriced one. High caliber theaters that promote a wide listening area all use at least 2 subs to do the job correctly.

 

[Ethan Winer]

Gene,

> Your "expert" clearly wasn't expert. <

Hey, he's not my expert!

Seriously, Terry does this for a living, and many people commented in the follow-up discussion that if he couldn't EQ a system properly, what chance did they have?

Do you have a system with a parametric EQ, and a way to measure and display ringing? If so, I'd love to see some before / after graphs showing ringing being reduced by a meaningful amount. But I'd also want to see what happens a few inches away.

> You Don't BOOST NULLS! <

Agreed. You're preaching to the choir.

> at low frequencies ... a few inches make little difference unless one is near a narrow interference dip or null. <

Yes, I once measured a change of 15 dB across four inches at 100 Hz. That was starting at the null center. But look again at the first two graphs on the page I linked above. The peak at 42 Hz changes by 3 dB from the center position to four inches right of center. When I ran those tests I was so surprised that I moved the mike back to center, measured again, then went back again, just to be sure it wasn't a measuring glitch. It wasn't.

> Two or even four decent less expensive subs properly placed in the room can be way more rewarding than a single overpriced one. <

Good point. Though I don't consider my $2,000 SVS sub overpriced. It is a killer piece of hardware.

--Ethan

 

[HAA Acoustics]

I'd like to again throw my two cents worth in to this discussion. There seems to be much agreement as to the effectiveness of bass traps, but I wanted to reinforce the value of multiple subs for the consumers reading this. Let there be no mistake, the purpose of multiple sub placement as discussed by Welti (Harman International) is the creation of a general areas of similar response. Further, acknowledging that some listening areas are better than others; a well designed system includes specific placement of listening seats in these acoustically similar areas. Once all listeners are properly positioned, any changes to the response for listener A will benefit listener B. Changes to the response can be effected by traps, speaker position and EQ. Obviously this discussion is limited to the <80 Hz realm and as I mentioned "sub bass" treatment is not practical for most folks due to the aesthetics. For most consumers, its' not a matter of choosing an extra sub versus bass traps, its usually a matter of two subs versus one; traps are not in the debate.

Keep in mind that all of the techniques to smooth response reduce low frequency gain; a very expensive commodity if smooth bass is desired. Two subs have the added benefit of creating two partially decorellated signals besides the 6 dB of gain. This has the welcome effect of partially filling the dips in response meanwhile phase differences go to work decoupling modal peaks. It's a wonderful thing that greatly aids in the smoothing of response at selected listening positions (and decently everywhere). It's well worth considering.

Above 80 Hz the variability of the sound field indeed becomes less manageable and bass traps begin to take their rightful place in the mix. Our targets are the reflections which create dips and peaks in response at various frequencies for various locations in the room through 1000 Hz. Here the absorption of these reflections is the only truly reliable way to control the effect of these echoes but at a price; the loss of extra reflections reduces the complexity of the sound field and exposes audible comb filtering between adjacent speakers heard by any listeners not precisely placed equi-distant from all speakers. This "comb filtering" is irrevocable because any path difference between two or more sources causes it; there's no cure. Comb filtering rips up smooth frequency response. Reflections do create comb filtering but they also add complexity to the sound field and act to mask the more egregious comb filtering of the multiple speakers (only if they are properly positioned though). This exposes an interesting paradox; absorbing reflections reveals a better sense of clarity and focus but only for the sweet spot. This sets up non-sweet spot listeners for bad sound.

For a two channel system, we simply clamp our head in the sweet spot and enjoy. In a home theater we apologize to our guests for the disparity between our seat and theirs. So what is the right answer? It depends on your goal; sweet spot versus good for everybody. For the bass trap supporters both approaches are benefited by the use of such treatment. The HAA teaches to use thick absorption behind and beside the LCR speakers if possible, then measure the sound field using spatial averaging, and finally maneuver the LCRs until the smoothest response is achieved. We then touch up the result with very precisely applied EQ if it's available. The spatial averaging measurement has the benefit of exposing resonances over simple cancellations; resonances are much more audible. Home theaters do have an advantage over two channel systems in that the center channel in effect automatically increases the complexity of the sound field by creating a third source. It's also important to note that adding distance between the listeners and any speakers moderates the audibility of comb filtering as well.

HAA (on behalf of the AV Professionals we represent)

 

[gene]

Here the absorption of these reflections is the only truly reliable way to control the effect of these echoes but at a price; the loss of extra reflections reduces the complexity of the sound field and exposes audible comb filtering between adjacent speakers heard by any listeners not precisely placed equi-distant from all speakers.

It is usually NOT possible to sit the listeners equadistant from all speakers. Don't you agree that time alignment in the processor takes care of this problem?

As for spatial averaging in the primary listening positions to look for system pathologies, Do you apply any weighing to those averages? For example, you emphasize more importance for 2 or 3 of the 6 seats for the owner who still wants their money seat?

On another note, how do you deal with asymmetric "L" shaped rooms where the front L speaker is near a wall, while the front R speaker is open to the L portion of the room?