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window behind monitors.... best way to treat this??

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Re: window behind monitors.... best way to treat this??

Postby Ethan Winer » Sun Jan 16, 2005 6:02 pm

Foz,

> Exactly what has been "solved" by using ETF? <

The vague results from 1/3 octave noise tests, where all activity in a relatively wide band is averaged rather than showing the true detail.

More to the point, either this type of test gives useful information or it doesn't. Who thought of it first (or in my case thought of it independently) is irrelevant. Bert pointed out that someone else did similar tests with MLSSA in the early 1980s. So if anything that confirms the value of such a test, no? Or did that fellow who used MLSSA conclude his tests were useless and gave no information of value?

--Ethan
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Re: window behind monitors.... best way to treat this??

Postby bert stoltenborg » Sun Jan 16, 2005 6:46 pm

Ethan,

I didn't mean it as an attack on you or something.

Read the stuff on the studiotips forum to see that generalizing (is this english?) these measurements is not possible. You are measuring a room/treatment combination, not a treatment.

That's exactly what these "vague 1/3 octave noise tests, where all activity in a relatively wide band is averaged rather than showing the true detail", developed by very intelligent and learned acousticians, try to avoid.

And about using measurements/waterfalls for determining specific effects in rooms, yes, I wrote about that (for what my contributions are worth) several times in the past couple of years. :bouncy:

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Re: window behind monitors.... best way to treat this??

Postby Scott R. Foster » Sun Jan 16, 2005 10:04 pm

Plotting resonances in a waterfall graph is trivial... its been done for years, and ETF is just a cheap way to collect the info, and create the graph.

Three cheers for ETF! I've got it. I use it, I like it. So do a lot of other folks.

:boring:

As to pretending that you had to "devise a new method..." to measure low frequencies...

http://www.ethanwiner.com/density/density.html

Pullllleassse!

ETF comes out of the box with a LF mode... you "devised a new method" in the same sense one discovers "new methods" for cleaning teeth when you use a tooth brush.

Ethan: you are good at explaining complex things in simple ways... a valuable skill... but IMO your inflated ego, your tendancy to take personal credit for the blindingly obvious, and your refusal to account for elements of a process which you cannot control or fully disclose the elements you do not understand makes this noble work at times come off as sheer silliness and blurs the message with utter nonsense. You so often go from being helpful into being misleading.. and this topic is a case in point.

In that, your stated purpose ["...assess the absorption of these materials at very low frequencies"] involves the measurement of MATERIALS, and collecting information on the LF absorption characteristics of a material - EXCLUSIVE OF THE ROOM WHERE THE MEASUEMENT IS TAKEN - is not trivial, and changing the graph used to display the data changes NOTHING about the hurdles to excluding the room from the measurement.

As has been explained to you a dozen times, there is a world of difference between measuring a material, and measuring a room that contains the material. I just don't understand why you refuse to "get it" on this point... and instead pretend you are conducting LF material absorption test when you are really conducting tests on the room[s] in question [with or without various materials added].

Let me put it this way... you've done your tests and published the results on the web... now, using your skills as an "acoustic expert" and your published data, please state the absorption coefficient for the following at 79 Hz in whatever terms you may [absolute, relative, or otherwise]:

3" 701
3" 703
3" 703-FRK
3" 705
3" 705-FRK


Now tell me how this varies for each material at 94 Hz.

Please report these material characteristics exclusive of the acoustic artifacts of the test room... as I want to use your information to choose the proper absorptive material I will use in a different room.

Thanks

:headbang:
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Re: window behind monitors.... best way to treat this??

Postby Hugh Robjohns » Mon Jan 17, 2005 12:35 pm

Foz wrote:Ethan: you are good at explaining complex things in simple ways... a valuable skill... but IMO your inflated ego, your tendancy to take personal credit for the blindingly obvious, and your refusal to account for elements of a process which you cannot control or fully disclose the elements you do not understand makes this noble work at times come off as sheer silliness and blurs the message with utter nonsense.

Oi! Enough already! Foz, Cool it....

I thought we had finally managed to get away from this kind of personal abuse but sadly, here you are starting it up again. For the very last time, PERSONAL ATTACKS OF THIS KIND ON ANYONE WILL NOT BE TOLERATED HERE. DO I MAKE MYSELF CLEAR?

Let's just accept (finally) that waterfall plots do have constructive uses in assessing the effects of treatment of room modes and move on shall we?

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Re: window behind monitors.... best way to treat this??

Postby Ethan Winer » Mon Jan 17, 2005 8:22 pm

Bert,

> You are measuring a room/treatment combination, not a treatment. <

I measured how successfully the various absorber materials controlled about eight modal frequencies. As explained in my report, the only frequencies I can test in that room are those that resonate. But within that limitation I am very much assessing how well those materials work, and I would expect an equivalent amount of absorption in any room. I'm sure it's possible to derive Sabins of absorption directly if ETF allowed exporting the data into a form that could be analyzed as data rather than by eye.

> That's exactly what these "vague 1/3 octave noise tests, where all activity in a relatively wide band is averaged rather than showing the true detail", developed by very intelligent and learned acousticians, try to avoid. <

Nobody is saying that reverb room tests are not useful, or that the people who developed the standards are less than super experts. However, those reverb rooms are not intended to measure reliably below 100 Hz. You can't even use them for relative comparisons, which is was my goal. This is what my tests accomplished. Are my tests perfect? No, of course not. But do they yield useful information not available at any price from a lab? You bet they do!

Anyone who doesn't want to use my data to help them decide what materials to buy is welcome to ignore it! :smirk:

--Ethan
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Re: window behind monitors.... best way to treat this??

Postby Eric Desart » Mon Jan 17, 2005 10:35 pm

Ethan Winer wrote:I measured how successfully the various absorber materials controlled about eight modal frequencies. .........

But within that limitation I am very much assessing how well those materials work, and I would expect an equivalent amount of absorption in any room.

......... You can't even use them for relative comparisons, which is was my goal. This is what my tests accomplished. .......... But do they yield useful information not available at any price from a lab? You bet they do!

Anyone who doesn't want to use my data to help them decide what materials to buy is welcome to ignore it! :smirk:


This is well meant and in the interest of the acoustic community.

Ethan you once more ignore the complete thread about this at Studiotips, while you know any single letter written.
You caused the thread to be born, and followed it to learn.

Experienced people who know how to interpret your page will not use it.
It are the ones, with less experience who blindly trust what you say/write which have to suffer for it.
You failed to make valid comparisons, and thereby mislead page visitors.

This is extensively explained in this thread which you know very well:
http://forum.studiotips.com/viewtopic.php?t=1348

Acoustically your comparison is wrong/misleading and publishing it as such is irresponsible.

And the moderators may believe this is personal, but for me this is a very damaging page, which mainly hurts people depending on, and trusting the assumed knowledge/responsibility of others.

And I think it can be interesting for other ETF users too to check the impact in function of the relative y-axis scale which make comparisons in certain situations VERY to EXTREMELY questionable.
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Re: window behind monitors.... best way to treat this??

Postby Scott R. Foster » Mon Jan 17, 2005 11:02 pm

No thanks Hugh:

The debate is NOT as you state on the question of whether waterfall plots are useful... or whether ETF is useful [wonderful product IMO.. I've been reccomending it for years]. No, the discussion centers on the claim that LF absorption test can be done at home with ETF. That claim is explicitly propounded at both here at this forum, in articles in you magazine, and followed up on at Ethan's web site where results are published arising from "new methods" Ethan has "devised" which purport to show comparison measurements of the materials that are useful in understanding the intrinsic attributes of these materials.

This is FALSE, and the fact you don't have a problem with that speaks volumes.

PS to Ethan: I'm still waiting on numeric responses on the absorption characteristics of 701, 703 and 705 interpolated from your "new methods" of LF absorption measurement.

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Re: window behind monitors.... best way to treat this??

Postby Ethan Winer » Mon Jan 17, 2005 11:36 pm

Eric,

> you once more ignore the complete thread about this at Studiotips <

And you once more ignore the intent of my tests and their value for relative assessment of materials. If you don't think my tests are useful even for relative assessment, that's your choice. But I probably speak for a lot of people when I say the constant complaining about Ethan, here and elsewhere, is becoming quite tiring. And it surely contributes nothing to anyone's understanding of acoustics.

Image

--Ethan
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Re: window behind monitors.... best way to treat this??

Postby Eric Desart » Mon Jan 17, 2005 11:50 pm

Aren't you the one claiming always to stay on topic?
This is not about opinions or finding but about facts, measurement techniques and acoustics.
Neither absolute, NOR relative is this page correct.

Anyhow interested people can read the thread, including real and substanciated arguments.

Thanks for showing yourself.
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Re: window behind monitors.... best way to treat this??

Postby bert stoltenborg » Tue Jan 18, 2005 12:05 am

But they do have cool smileys here
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Re: window behind monitors.... best way to treat this??

Postby Ethan Winer » Tue Jan 18, 2005 1:17 pm

Eric,

> This is not about opinions or finding but about facts, measurement techniques and acoustics. <

You are correct. It is about science. It's about finding solutions to long-standing problems. It's about getting repeatable results. It's also about cooperation and sharing resources for the mutual benefit of all.

Elsewhere you complimented acoustician Angelo Campanella for his great attitude when you wrote, "Angelo is very gentle, he encourages anyone and lots of things when he believes someone is learning and searching."

That's an admirable trait indeed, and you would do well to take a lesson from him.

--Ethan
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Re: window behind monitors.... best way to treat this??

Postby Brian Ravnaas » Tue Jan 18, 2005 1:51 pm

Ethan Winer wrote:

One of these days I plan to measure the comb filtering off my large thermal-pane patio door, using ETF and my Carver Sunfire subwoofer that outputs solidly down to below 25 Hz. I think that's the best test of how much a glass door may reduce acoustic interference.

--Ethan


i think that is a marvelous idea. i wonder if you'd be able to separate the reflections/comb filtering process from the general modal behavior in the room?

i do very much think this phenomenon is worth exploring, and i'll join ethan in volunteering some time. I'll pony up a day of time in the reverb room pair in our labs to assesss the impact on modal behavior of an unimagineably bad wall - probably to be a single layer of 1/4" drywall (plasterboard).

it would be very valuable to the general goal, i think, to utilize an accelerometer and a simple impact (tap with a rubber mallet should suffice) to determine resonant points of the structure under test - then any absorption peak that may be noted could be correlated to the resonant points, etc.

Brian

PS: as i mentioned above, i also think that it is incorrect to tout poor transmission loss as beneficial to room modal behavior. Per the math and presentation above. But, then, a good unbiased test should be worht much more than a calculation or an oft-quoted, probably ancient and somewhat haphazard sentiment, no?

should be fun.
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Re: window behind monitors.... best way to treat this??

Postby Eric Desart » Tue Jan 18, 2005 4:04 pm

Ethan Winer wrote: It's also about cooperation and sharing resources for the mutual benefit of all.

"Angelo is very gentle, he encourages anyone and lots of things when he believes someone is learning and searching."

That's an admirable trait indeed, and you would do well to take a lesson from him.


You're good, REALLY good...

What was the topic again????

I was involved in several topics here:

1) Minitraps and its membrane effect versus other solutions: diverted to non-related measurement techniques and suggested malice and deceit by others.

2) Validity of RAL measurements: An exact final acoustic question which could give a final answer diverted with a reference to discussions with third parties behind the scene, and reference to the distastfulness of continuing the argument in function of the "end of year" holidays.

3) The wrong use of the non-existing concept (not word or notion) "crossover frequency" (in the used context) and the energetic content of sound "outside" a room diverted to absorption in the room.
And just repeated here as if this thread never existed:
http://tinyurl.com/6wg3x

4) The current wrong misleading comparison related to density and FRK in function of corner absorption. Data published at the expense of others searching for help diverted to complete non related quotes, and advice indeed applicable to yourself.

But I agree: you're good, REALLY good.
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Re: window behind monitors.... best way to treat this??

Postby Ethan Winer » Tue Jan 18, 2005 4:49 pm

Brian,

> i wonder if you'd be able to separate the reflections/comb filtering process from the general modal behavior in the room? <

I'm not so worried about that as much as assessing by how much the reflected energy is reduced. A wall that's 100 percent reflective will create a null that's infinitely deep 1/4 wavelength away from the wall. (Assuming a straight angle of incidence.) Reducing that reflection by only 1 dB raises the null from infinitely deep to only 19 dB deep. Reducing it another dB makes the null only 14 dB deep. Reduce it again to -3 dB and now the null is only 11 dB deep. Once you reduce the refection by 6 dB the null is now only 6 dB deep. So reducing the reflection even a tiny bit can make a huge response improvement in the room. This seems to me the main issue.

> utilize an accelerometer and a simple impact <

I figure that using a subwoofer with a solid output down to 20 Hz and the ETF software will show the comb filtering and the extent of the nulls. But if you know a better way that measures the same thing, go for it. I have a large glass double door to the outside, but it's 40-50 feet from my home theater receiver. My plan was to measure the comb filtering with the glass door open, with the door closed, and with the door closed and 3/4 inch sheet rock in front of the door. Besides having to find a 40+ foot RCA extension, or cobble one from a bunch of adapters, I'd also need to buy a big piece of 3/4 inch sheet rock and schlep it upstairs without getting powder all over the floor. That's why I haven't yet done this test myself. :lol:

> i also think that it is incorrect to tout poor transmission loss as beneficial to room modal behavior. <

Again, I'm not thinking in terms of modes as much as the problems caused by simple acoustic interference. Yes, I realize they are related. But as I showed above, if the reflections can be reduced even a little, the nulls (and peaks) will be greatly improved in the process.

--Ethan
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