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Old 19th October 2012, 11:55 AM   #531
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Originally Posted by markus76 View Post
Near field configuration increases sub efficiency by a whopping 10dB.
Modal ringing is minimized.
Now you are just repeating what I said may post ago and showed at my web site years ago.
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Old 19th October 2012, 12:11 PM   #532
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John, could you please post the promised impulse responses?
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Old 19th October 2012, 02:35 PM   #533
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John, could you please post the promised impulse responses?
Hi Markus,

You know, I set the woofer up again, took all the data, made jpegs of the FR, Impulse, Burst waterfalls and sonograms. All sitting nicely in my photo editor. Then, before I had saved all the jpegs, the power failed and I lost it all. I haven't had the desire to do it a third time. I will tell you that you won't learn anything by looking at the impulses. They all looked similar in structure and had about the envelop for the decay rate.

It's raining today so if I get around to it I may give it another shot. But honestly, I'm not real motivated because I won't think it will really tell you anything.
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Old 19th October 2012, 02:46 PM   #534
lolo is offline lolo  France
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Originally Posted by Wavebourn View Post
And since bass without higher frequencies does not exist in nature it has to be phase coherent.
phase coherence from top to bottom.. that's not easy to get.. how do you manage?
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Old 19th October 2012, 02:56 PM   #535
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Originally Posted by john k... View Post
Hi Markus,

You know, I set the woofer up again, took all the data, made jpegs of the FR, Impulse, Burst waterfalls and sonograms. All sitting nicely in my photo editor. Then, before I had saved all the jpegs, the power failed and I lost it all. I haven't had the desire to do it a third time. I will tell you that you won't learn anything by looking at the impulses. They all looked similar in structure and had about the envelop for the decay rate.

It's raining today so if I get around to it I may give it another shot. But honestly, I'm not real motivated because I won't think it will really tell you anything.
Sorry to hear that. You don't have the old ones anymore? I'm more interested in how your room behaves compared to mine.
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Old 19th October 2012, 03:34 PM   #536
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Originally Posted by markus76 View Post
Results for different near field configurations are in:
Markus - nicely done

Unfortunately its not a universal solution. I can't do it, just like I can't do the bass array cancellation technique. I have two rows of seats, and a door on the rear wall. With the multiple sub layout it can always be made to work and I suspect that the differences in sound quality will be minimal.

The fact is that DSP has changed the world of LF reproduction and I really think that all the techniques will be far closer to each other than any of them are to the "old way". The point is that if you are still using a single sub, or subs without EQ, then get with the program.

PS. in your writeup you say that you did 3 averages but all at the same mic position - 1. Whats the point in that?
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Old 19th October 2012, 03:40 PM   #537
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Markus:

In post #530

What are microphone distances?

Windowing for spectrograms is too large and 30dB range is too small; can't get much from this view.

Here is 10" Peerless driver suspended 30" from carpeted floor, and >5ft. from walls and ceiling. Microphone is 30" above floor, and 30" from driver:

Frequency response:

1 raw spl.jpg

Impulse response:

1 raw ir.jpg

Spectrogram:

2 raw spectrogram.jpg

Spectrogram windowing is 60ms, Blackman-Harris 4


Inverse transfer function is generated from IR, band limited with FIR and minimum phase version generated of this inverse.

These inverses are applied to measurement sweep by convolution, and used to measure driver. Microphone and driver are undisturbed from initial measurement. Sound of sweeps during response recordings are smooth, audibly there is no reverberant/echo effects produced by inverse functions.

Results of linear phase correction filter:

Frequency response:

3 lin spl and phase.jpg

Impulse response:

4 lin ir.jpg

Spectrogram:

5 lin spectrogram.jpg

Results of converting linear phase filter to minimum phase filter:

Frequency response:

6 min spl and phase.jpg

Impulse response:

7 min ir.jpg

Spectrogram:

8 min spectrogram.jpg

REW has nice group delay feature; overlays of GD for raw, linear phase EQ, and minimum phase EQ:

9 gd overlay raw lin min.jpg

As usual, minimum phase filter is ruinous to group delay performance.

Regards,

Andrew
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Old 19th October 2012, 03:42 PM   #538
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Originally Posted by gedlee View Post
Markus - nicely done
Thanks.

Quote:
Originally Posted by gedlee View Post
in your writeup you say that you did 3 averages but all at the same mic position - 1. Whats the point in that?
I didn't want to introduce additional variables by Audyssey doing any "fuzzy clustering magic" but wanted it to behave like a single point equalization. 3 measurements are minimum for Audyssey.
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Old 19th October 2012, 03:52 PM   #539
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Unfortunately its not a universal solution.
I believe it's THE solution for everybody that wants really good bass and doesn't have a dedicated listening room with proper acoustic treatments. It's also limited to a few seats within one row but is stereo/multichannel anything more than a one seat solution?

Near field subs can probably also made to work with the typical couch at the back wall layout. Would have to test it though.

Last edited by markus76; 19th October 2012 at 04:01 PM.
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Old 19th October 2012, 03:55 PM   #540
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The fact is that DSP has changed the world of LF reproduction and I really think that all the techniques will be far closer to each other than any of them are to the "old way".
I'm wondering how the source-to-sink principle could be exploited more by taking lots of measurements within a room and placing/processing sources accordingly.
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