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Multi-Way Conventional loudspeakers with crossovers

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Old 26th October 2013, 08:17 PM   #6211
gedlee is offline gedlee  United States
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I was not too impressed with the Dirac guys.

Optimizing a number of points in space will optimize all points, but one cannot say that there is any solution which will improve all points simultaneously, that's quite a different thing, and it would be impossible.

Are we talking about the steady state field or the direct field here? Completely different situations. I was talking about the polar response and hence the direct field if we are talking about room acoustics. Since this thread is about "waveguides" consideration of a rooms steady state response is not appropriate.
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Old 27th October 2013, 01:20 AM   #6212
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I think one could be too focused on the technology of audio and forget about music. The only way you can tell whether they match up is to listen to the resulting system. I think we should really listen to a system based on Dirac technology.
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Last edited by soongsc; 27th October 2013 at 01:22 AM.
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Old 27th October 2013, 01:32 AM   #6213
Pano is offline Pano  United States
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Originally Posted by dumptruck View Post
Holm works fine on my Win7 laptop, for whatever that's worth.
Also FWIW, HOLM runs great for me under Windows XP. With 7 it crashes from time to time. Under Win 7, I save frequently.
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Old 27th October 2013, 02:31 AM   #6214
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Markus,

Earl is right on here. Diffraction and real radiation of driver is not one dimensional. Degree to which it is one dimensional is degree to which EQ may be used to correct overall response.
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Old 27th October 2013, 06:41 AM   #6215
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I have no problem being wrong but did anybody actually try an EQ based optimization approach and looked at how good or bad it performed?
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Old 27th October 2013, 10:38 AM   #6216
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We're looking at a multitude of linear systems (each point in space). If they are minimum phase and similar enough, EQ can be used to improve things. Isn't this useful?

I tend to agree with this with "improve" being the operative phrase. As Earl points out diffraction effects vary in the polar sense, so no universal correction is available. Still, improvement from one vantage point is likely to be in the right direction from surrounding vantage points. This is a matter of using good judgment and not over correcting deep flaws.

We do the same for LF room correction: if response is measured over a broader listening area then the best correction becomes milder and less individually perfect, but gives general improvement for most seats.

As to baffle step, I would certainly assume this was minimum phase and can and should be totally corrected.

Its worth noting that nonminimum phase issues might benefit from correction as well as minimum phase issues. In the end you will have an all pass function (residual phase issues) but the system will be flat. That seems smarter than throwing up your hands and leaving response errors because a system is not minimum phase. Shouldn't let "the perfect be the enemy of the good".

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Old 27th October 2013, 10:43 AM   #6217
soongsc is offline soongsc  Taiwan
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Originally Posted by markus76 View Post
I have no problem being wrong but did anybody actually try an EQ based optimization approach and looked at how good or bad it performed?
Click the image to open in full size.
Click the image to open in full size.
The above measurements are measured about at 1M, one EQed based on the 1M measurement, the other EQed based on near field measurement. So one EQs the diffraction effects, the other does not. I have also tried EQing near field at center of dust cap, at the voice coil, and midway.
While not conclusive, the 1M EQ did sound a bit fuzzier than near field EQ in the transients, overall sound had darker background with 1M EQ. Ultimate Equalizer software EQ was used.
After this test session, the amp was improved to provide best performance without software EQ, and also implemented hardware EQ till most auditors felt it was optimum.
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Last edited by soongsc; 27th October 2013 at 11:07 AM.
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Old 27th October 2013, 03:36 PM   #6218
gedlee is offline gedlee  United States
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Originally Posted by speaker dave View Post
As to baffle step, I would certainly assume this was minimum phase and can and should be totally corrected.

David
David

If baffle step is a diffraction issue, as I understand it is, then even if it is Minimum Phase, it cannot be corrected globally.
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Old 27th October 2013, 04:12 PM   #6219
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Originally Posted by soongsc View Post
The above measurements are measured about at 1M, one EQed based on the 1M measurement, the other EQed based on near field measurement. So one EQs the diffraction effects, the other does not. I have also tried EQing near field at center of dust cap, at the voice coil, and midway.
While not conclusive, the 1M EQ did sound a bit fuzzier than near field EQ in the transients, overall sound had darker background with 1M EQ. Ultimate Equalizer software EQ was used.
After this test session, the amp was improved to provide best performance without software EQ, and also implemented hardware EQ till most auditors felt it was optimum.
We're talking about an effect that is spread in space so looking at a single point is useless.
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Old 27th October 2013, 05:19 PM   #6220
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Quote:
Originally Posted by soongsc View Post
The above measurements are measured about at 1M, one EQed based on the 1M measurement, the other EQed based on near field measurement. So one EQs the diffraction effects, the other does not. I have also tried EQing near field at center of dust cap, at the voice coil, and midway.
While not conclusive, the 1M EQ did sound a bit fuzzier than near field EQ in the transients, overall sound had darker background with 1M EQ. Ultimate Equalizer software EQ was used.
Why would you try EQ'ing the drivers near field response close to the dust cap ?

A near field measurement is not even remotely valid at high frequencies even if the cone were a perfect piston and there were no baffle diffraction effects, let alone when there are cone breakup effects.

You need to be at least 3x the diameter of the cone away before high frequency data starts to become valid just for the driver by itself. To include baffle diffraction you need to be further away again. (In theory 3x the largest baffle dimension)

Automated EQ made at a single point in space is never going to work very well anyway because it can't tell what response aberrations are spatial (diffraction etc) and which are not (cone resonances etc)
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Last edited by DBMandrake; 27th October 2013 at 05:25 PM.
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