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Discussion Starter · #1 ·
I nees some expert help on this one. I've bought my GOM material already so I hope the answer is yes, that they are all pretty much the same.


The tech at GOM couldn't tell me if there are any differences acoustically between say the FR701, Streetwise, Anchorage, etc. She said indeed the 701 is widely used for putting in front of speakers, but couldn't comment on whether or not it was/is because of the acoustic transparency in that particular fabric.


I have the red and black Streetwise material and it has an actual pattern to it, so the question is, is it acoustically the same as the others and does it need to be run in one direction vs the other because of the pattern?


Boy, the things I get myself into.



Thanks for any comments.


Chris
 

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I believe the FR701 fabrics are all labled as being "acoustically transparent." I am not aware of any data or marketing claims that would differentiate the transparency of one pattern vs. another.


In reality, nothing is truly "acoustically transparent," but fabrics like GOM 701 series should not create an "audible" difference in sound quality. Perhaps one could measure the difference in transparency between various patterns, but I doubt even a measureable difference would amount to anything worth worrying about.
 

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Not all GOM fabrics are transparent enough to be used in front of speakers. There is a thread here somewhere that Terry Montlick posted that listed the GOM fabrics and their effect on sound in terms of high freuquency absorbtion. Can't find it right now.



If you stick with FR701-2100 for in front of the speakers, others will be generally acceptable for wall treatments unless they're very tight weaves - which some of the GOM fabrics are.


Bryan
 

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All of the GOM fabrics are considered to be "acoustically transparent" and are suitable for panel covering.
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by bpape /forum/post/0


If you stick with FR701-2100 for in front of the speakers, others will be generally acceptable for wall treatments unless they're very tight weaves - which some of the GOM fabrics are.

That's the point. I already have the Streetwise material in posession.

Quote:
Originally Posted by bpape /forum/post/0


Not all GOM fabrics are transparent enough to be used in front of speakers. There is a thread here somewhere that Terry Montlick posted that listed the GOM fabrics and their effect on sound in terms of high freuquency absorbtion. Can't find it right now.

Yes, but which ones? The folks at GOM themselves cannot, or will not, commit to telling which, if any, of their fabrics are or are not more or less acoustically transparent.




"Acoustical transparency is a matter of degree -- nothing is 100%. High frequencies are always attenuated to some degree. Generally, you need only be concerned within the Guilford line if you want to use a fabric as a speaker grill cloth, or if you have had a high-performance acoustical design done which critically relies on a specific sound absorption balance."


This is a quote from Terry on GOM. I pretty much already figured that any cloth in front of a speaker will attenuate the highs, my concern is specifically if the Streetwise is less transparent.


Maybe I'll do a few tests with my tone generator, some pink noise and a SPL meter.


Chris
 

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Quote:
Originally Posted by CCLAY /forum/post/0


I pretty much already figured that any cloth in front of a speaker will attenuate the highs, my concern is specifically if the Streetwise is less transparent.


Maybe I'll do a few tests with my tone generator, some pink noise and a SPL meter.


Chris

Hi Chris,


According to John Cudak, Streetwise has "adequate" acoustic properties, but is not suitable for speaker cloth applications.

Is there a design construction newbie FAQ? Posting #16

Guilford of Maine Acoustic Properties


Here's a couple of other threads on the subject that may also be of interest.

All GOM accoustically transparent?

Loss of high freq absorbtion due to fabric type


Good luck with your project.


Larry
 

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Quote:
Originally Posted by bpape /forum/post/0


If you stick with FR701-2100 for in front of the speakers....

Oops, I forgot the "2100" part of that. Shows what I know.



I guess I also misunderstood the question a little bit. Oh well, hopefully people will have mercy on the jobless guy!
 

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Quote:
Originally Posted by bpape /forum/post/0


Thanks for posting that link Larry. The 2nd one is the one I was trying to find.


Bryan

Hi Bryan,


You're welcome.


Although I've seen some postings in which Terry has discussed this subject, and I know he has done studies, I have not seen a list posted by him. I do not believe the attachment is one of his. Based on the posting I believe John Cudak is the author.


Larry
 

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I used Gom 701 (don't remember the #) and did not like the sound of my speakers which I had for years. So I opted for speaker grill cloth in front of my speakers. sounds good now. Gom is really a wall/panel fabric not speakers IMO.
 

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Discussion Starter · #11 ·
Thanks for the info and links, Larry. Very much appreciated. Guess I should done a little more 'searching' before I posted. And bought, for that matter



Unfortunately, all 7 of my speakers will have Asphalt Streetwise in front of them. Now my decision is whether to keep the Streetwise or can it and go to the 701. Drats. I'll do my own testing this weekend and post the results next week.


Chris
 

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Quote:
Originally Posted by CCLAY /forum/post/0


Thanks for the info and links, Larry. Very much appreciated. Guess I should done a little more 'searching' before I posted. And bought, for that matter



Unfortunately, all 7 of my speakers will have Asphalt Streetwise in front of them. Now my decision is whether to keep the Streetwise or can it and go to the 701. Drats. I'll do my own testing this weekend and post the results next week.


Chris

Hi Chris,


No problem. It's sometimes quite difficult to find threads even when you know that they exist.


Naturally I'd be interested in your testing, but you also might try an other blind test. See if you can actually hear a difference with your eyes closed and with a helper moving the fabric in front of the speakers and away.


In normal situations even trained listeners have difficulty perceiving differences in levels that are 2 dB or less. Here's a quote from Everest's Master Handbook of Acoustics:

Quote:
At 1 kHz, for very low levels, a 3-dB change is the least detectable by ear, but at high levels the ear can detect a 0.25-dB change. A very low level 35-Hz tone requires a 9-dB level change to be detectable. For the important midfrequency range and for commonly used levels, the minimum detectable change in level that the ear can detect is about 2 or 3 dB. Making level changes in increments less than these is usually unnecessary.

At above 12 kHz the "acoustically transparent" GoM FR701 2100 series has a maximum attenuation of 2 dB (less for lower frequencies). For Streetwise this value is only slightly higher at 3 dB. In most cases at normal listening levels these difference in levels would be barely detectable.


No insult is intended, but judging from his picture, Caspian is not a teenager. Therefore, it is remarkable that he can even hear a tone above 12 kHz, let alone an extremely small difference in dB between the attenuation of speaker cloth versus GoM FR701 2100.



In summary, you may find that from an acoustical perspective that Streetwise fabric may turn out to be fine. However, it should be pointed out that it isn't certified to be fire retardant. As was pointed out in the other threads, it is the combination of acoustic properties plus it's fire retardant properties that makes GoM FR701 2100 so popular in home theater applications.


Larry
 

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Discussion Starter · #13 ·
Thanks once again for the excellent info Larry. I've got friends lined up for tomorrow to do some blind testing and SPL measuring. Fortunately, I'm not a.....ahem....teenager either.



Chris
 

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Quote:
Originally Posted by CCLAY /forum/post/0


Thanks once again for the excellent info Larry. I've got friends lined up for tomorrow to do some blind testing and SPL measuring. Fortunately, I'm not a.....ahem....teenager either.



Chris

Hi Chris,


Yeah, in the interests of science perhaps you might try renting a teenager to participate.



That is, if you can find one who hasn't already destroyed their hearing with iPods, rock concerts, or car sound systems.



Larry
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by LarryChanin /forum/post/0


rock concerts, or car sound systems.



Larry

I think half my own hearing was destroyed once at a Scorpions concert. I just haaaad to have the fifth row....
 

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Discussion Starter · #16 ·
Well, I did as much testing and listening as my ears could stand and found the chart 'Guilford of Maine Acoustic Properties' that Larry posted a link to was/is pretty darn accurate.


It was a little hard testing at those frequencies in my HT room because it's only about half done and I had tones bouncing all over the place in the room. That and the fact of the 1kHz - 6.3kHz range can be brutal on the ears, even at lower volumns.


I wish I had a little 701 material to do some side by sides, but regardless, it was unanimous with everyone that you could hear an audible difference, which came as no surprise, with the Streetwise material in front of the Triad In-Room Golds. Not a huge difference, but noticable.


Chris
 

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Quote:
Originally Posted by CCLAY /forum/post/0


Well, I did as much testing and listening as my ears could stand and found the chart 'Guilford of Maine Acoustic Properties' that Larry posted a link to was/is pretty darn accurate.


It was a little hard testing at those frequencies in my HT room because it's only about half done and I had tones bouncing all over the place in the room. That and the fact of the 1kHz - 6.3kHz range can be brutal on the ears, even at lower volumns.


I wish I had a little 701 material to do some side by sides, but regardless, it was unanimous with everyone that you could hear an audible difference, which came as no surprise, with the Streetwise material in front of the Triad In-Room Golds. Not a huge difference, but noticable.


Chris

Hi Chris,


Thanks for the update.


So, have you decided what you are going to do?


Larry
 

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Discussion Starter · #18 ·
Yeah, I'm going to stick with the Streetwise. The difference in sound is not really a deal breaker, imo. Plus, I'm sure that I'd be able to hear a small difference even with the 701 in front of the speakers.


The Triads sound just a tad more open and airy with nothing covering the drivers, but that wouldn't make for a very good looking theater, would it?


One thing I found bizzare was one buddy of mine couldn't hear the 12kHz tone at all, with or without cloth in front of the speaker.



Chris
 

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Quote:
Originally Posted by CCLAY /forum/post/0


Yeah, I'm going to stick with the Streetwise. The difference in sound is not really a deal breaker, imo. Plus, I'm sure that I'd be able to hear a small difference even with the 701 in front of the speakers.

Yes, with the Streetwise versus nothing you should have a maximum difference in levels of about 3 dB at over 12 kHz. With the Streetwise versus 701 that maximum difference in levels would be about 1 dB. Human hearing is not likely to pick that up at normal listening levels.

Quote:
Originally Posted by CCLAY /forum/post/0


One thing I found bizzare was one buddy of mine couldn't hear the 12kHz tone at all, with or without cloth in front of the speaker.



Chris

Not bizarre at all. The bizarre part is you, at your advanced years, with Scorpion abused hearing, could hear it.
 
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