Jeff Hedback designed acoustical panels

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Jeffrey Hedback

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Re: Jeff Hedback designed acoustical panels
« Reply #20 on: 24 Jun 2011, 01:00 pm »
Well it seems that possibly our friend McTwins has an ax to grind.  However, I'm pleased that you've commented and btw have enjoyed your posts. 

On the panels in Mikes room, please read post #3 of this thread for a proper description and you would quickly find the majority of your comment resolved.

As for the freq response, attached in the black curve is the "both speaker at LP LF response" with no smoothing (relative value with Y-axis set to arbitrary value) and the TEAL curve is the same impulse response gated to 65ms.  This TEAL curve is the SPEAKER/BOUNDARY contribution of the overall response.  The value of this study are A) to see if the room's resonances are still affecting the room response (and obviously they are not) and B) to focus on possible adjustments to speaker/listening positions.  A quick study of the differences shows a slight dip at ~57Hz and a rise of ~5dB at 36Hz.  So your comment of the lack of control at 35Hz has some merit in terms of absolute control, but this clearly shows excellent control at that range.  The net of this graph is that the LF response is indeed smooth in it's contour as shown in this graph with no smoothing.

Mike's speakers and system employ the Spatial speaker correction system http://www.6moons.com/audioreviews/spatial/1.html

These measurements are with no EQ.  I have discussed with Mike that in my opinion his LF range shows too great a rise.  However, with EQ this is much less.  The results of this treatment effort have yielded objective and subjective results that are right on target.  To improve the response as desired, Mike has the opportunity to adjust speaker positions & LP and revoice the speakers via the Spatial system.


Jeffrey Hedback

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Re: Jeff Hedback designed acoustical panels
« Reply #21 on: 24 Jun 2011, 01:28 pm »
...also I should mention that the diffusors are not Phase Grating devices but Amplitude Grating.

McTwins

Re: Jeff Hedback designed acoustical panels
« Reply #22 on: 25 Jun 2011, 11:54 am »
Hi

Why are you showing measurments below 100 Hz when this thread subject is about diffuser panels?

Those panels can't take resonances below 100 Hz and you can never convince me otherwise, because I can clearly see that on the spectrogram plot.

You are using the easy way of adjusting the low freq response by adjusting the speaker and listening pos and to minimize the low freq peaks and dip by adding some EQ. This I can buy, but you can never reduce the resonance and Q-value in the room.
The resonances will still be present in the room, period.

Those panels by construction can never by it's small internal volume and it's low Q-value take any specific resonances below 100Hz despite the vinyl membrane in place. I know this because I tested this method by myself.

As I understand, your ARTA measurements is showing the changes before and after EQ, and it's not due to the DIY diffuser panel that has changed the low freq resp.

There is no ax to grind here :D

What is it you are trying to show here? :scratch:

Thanks


Jeffrey Hedback

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Re: Jeff Hedback designed acoustical panels
« Reply #23 on: 25 Jun 2011, 12:34 pm »
Good day McTwins,

The thread was started by my client to share his build process (through completion) of my design.  Although the panel assembly has an amplitude reflection grating element, this thread is not about diffusors (that is another thread in this circle).

The ARTA graph is an overlay of the very same impulse response (not EQ'd, not pre/post): Teal is gated to 65ms and the black is gated to 200ms.  The Speaker Boundary Interference Response (SBIR) component of the LF response occurs within ~65ms (room size depending) and after that room resonance (modal peaks/nulls) kick-in.  I hope this additional clarification addresses your review of that graph.  You stated a prediction that there would be great peaks and dips in the lower regions.  This graphs offers resolution of your contention and validates the acoustical devices (based on minimal contribution of room and the +/-4dB 30Hz-100Hz unsmoothed response).

The LF response and spectrogram data are Mike's system with no EQ, although he normally listens with EQ (again, reference the Spatial correction system).

As for mlv (mass-loaded vinyl)...I will fully and respectfully disagree; although, I'd be glad to discuss any systems you have tried.  I have two manners of use that have worked and worked well.

At some point in time in the near future, the Spatial system will be re-calibrated and I would think Mike and I would engage in some type of final in-room with system calibrated measurement.  Should that happen as expected, I will gladly share the wrap up data.


McTwins

Re: Jeff Hedback designed acoustical panels
« Reply #24 on: 25 Jun 2011, 01:30 pm »
Hi

Know I understand your ARTA measurement.

You are saying that there is no resonances under 65ms and after 65ms the resonances kicks in.

How do you know this or see this?

And why the magical number 65ms?

You can never see this in CSD because it will truncate at 65ms. You have to show the whole spectrum to be able to see the resonances in CSD.

You are not showing if you have resonances in CSD measurements in ARTA. You are showing another programs spectrogram plot.
I want to see this CSD in ARTA, please.

Showing the 65ms plots is totally missleading and irrelevant, if you ask me.

About your mass loaded vinyl, I would like to see if you can take a resonance at 25Hz with high Q-value.

My point is that if you fix the resonances and the Q-value in a room thus lowering the reverb time in low freq time domain you can put the speakers and sit where ever you want in that room. And this is the hard way to treat a room acoustically. :D

Thanks

Jeffrey Hedback

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Re: Jeff Hedback designed acoustical panels
« Reply #25 on: 25 Jun 2011, 03:53 pm »
Please reference the foundational work by Russ Berger (furthered by Syn-Aud-Con and RPG) nearly 30 years ago now on the topic of SBIR and related time aspects.

As for your final statement...100% agree (well 98% agree...you cannot expect to place speakers/ears "anywhere"...but yes, great flexibility would be had in your context)..

That in no way means that "Mike's design" is not fully effective or appropriate.

Nice exchange McTwins.

Update: Mike will soon do the re-EQ process with Clayton of Spatial.  So final updates may appear as early as next week.

MaxCast

Re: Jeff Hedback designed acoustical panels
« Reply #26 on: 25 Jun 2011, 05:40 pm »
Thanks for keeping this civil guys  :thumb:
I probably speak for most of us here in that I didn't think there was much difference in the graphs either.
Plus, I'll have to re-read the last few posts 5 more times to get the difference.  :icon_lol:

Jeffrey Hedback

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Re: Jeff Hedback designed acoustical panels
« Reply #27 on: 25 Jun 2011, 07:06 pm »






This may help MaxCast.  I'm looking forward to the final measurements and results and as mentioned will share.

Jeffrey Hedback

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Re: Jeff Hedback designed acoustical panels
« Reply #28 on: 25 Jun 2011, 07:12 pm »




or this...this graph is an Excess Group Delay study that utilizes a minimum phase version of the impulse response to show...reflections.  Deviations + or - from "0" are room reflections. 

McTwins

Re: Jeff Hedback designed acoustical panels
« Reply #29 on: 26 Jun 2011, 09:17 am »
Hi
Just for clarification....
Is this waterfallsplots from Mikes room before and after the panel treatments on the wall?

Thanks

McTwins

Re: Jeff Hedback designed acoustical panels
« Reply #30 on: 26 Jun 2011, 03:55 pm »
Hi
Ok, I asume it is Mikes room.

What has been done between Pre and Post measurements??

As I see it, from those two waterfallsplots you have still several severe resonances beyond 300ms under 150Hz, that you have not treated.
That's is as I was suspected.
You haven't done ANYTHING in this room.

You have a strong resonace at around 30Hz and now build a vinyl membrane resonator and come back with measurement when you have reduce that resonance, Good luck.

Looking at excess group delay and other things is totally overkill when you are still not adressing the resonances in a room.

I have nothing further to add for the moment. :D

Thanks