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Old 31st December 2012, 04:39 PM   #161
Pano is offline Pano  United States
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Quote:
Originally Posted by CopperTop View Post
I think it's still more-or-less on topic as long as it wanders back to rephase now and again.
I hope we get back on topic by the end of the year.
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Old 31st December 2012, 06:32 PM   #162
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Quote:
Originally Posted by CopperTop View Post
.......The aim seems to be to mix up the comb filtering between drivers through the crossover region.......
Does it work?!
Design has comb filtering when crossover frequency is too high for driver separation. Fix design, not muddy over. Do something coherent with your convolution setup and work with inverse transfer functions.
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Old 31st December 2012, 10:27 PM   #163
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Quote:
Originally Posted by Barleywater View Post
1ch in, in 1ch out. All measurement points can only be correlated to single input, a design axis is chosen that is representational of design application .....

Design point is 9" from tweeter face. Tweeter axis is angled about 5 degrees up from horizontal, and microphone is placed slightly below tweeter axis.
Presumably you have some clever method to put both your ears at that point.

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Off axis responses and phase are posted how-achieve-coherence-5.html#post3220782and how-achieve-coherence-5.html#post3221038.
Thanks for this Barley. The off axis vertical impulses show loadsa pre-impulse as expected and discussed by Greenfield.

You'll excuse me my old fashioned prejudice as a commercial speaker designer for more than half my life, that finds pre-impulse evil except for certain anti-aliasing filters.

I'm rather surprised at the amount of deterioration on the horizontal plane until I remember Pluto uses a 2" treble.

IMHO, Pluto only works cos the 2" treble and 1kHz xover. Of course a speaker is always the sum of the parts rather than dependent on any single spec of any single component so I'm sure it sounds OK.

You are perfectly right about xover freq. & driver separation. Pluto is the equivalent of my 'zillion dB/8ve' xover for subs at 80Hz.

The problem for a commercial speaker is finding a 2" unit with sufficient power handling. Most 'music' divides its power equally around 1kHz. Which is why its a good frequency for Bi-amping bla bla. I'll shut up about the evils of 2" directivity.

Quote:
Aha! So you might know something about the so-called Stochastic Interleave alignment described here:
http://www.essex.ac.uk/csee/research...ssing%20LS.pdf
One of the papers I was external examiner at Malcolm's request is Rimmel, his ref 12.

Sadly, although Malcolm says the importance of his supa dupa method is "reducing the subjective significance of polar response errors", he doesn't show any evidence of the effect on polar response.

I think Greenfield's paper is a better discussion of this though I don't agree with his solutions.

Surprisingly, Malcolm also shows some very naive digital EQ, eg fig 2b, which Richard Greenfield and I have discussed many times and agreed as verboten!

Malcolm's paper, after you wade through the double integral obfuscation, is mainly about how to pretty up CDS curves by some very dubious methods, eg hiding the excess phase stuff.

The short answer is I dunno whether it "reduces the significance of polar response errors" and I don't think Malcolm knows either.

BTW, most of the Essex stuff was done with units provided by Celestion before I started work for them.

Re-reading "Is Linear Phase Worthwhile?", I can't fault any of my recommendations from 30 yrs ago even with all dis evil 21st digital stuff.
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Old 1st January 2013, 02:33 PM   #164
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an interesting tool in rePhase is the All-pass inverse/All-pass function.

1: generate a inverse All-pass function to remove time,export...
2:generate a All-pass to add delay.export...
3:Import IRs with HOLM do the C=AxB (manual convolution),export as an impulse.wav

check group delay with REW.
it's useful in front of passive filter and a stereo amp,it avoids multi amp channel to delay some driver.
in this case,only middle band is delayed.
of course some FIR EQ are welcome with the time correction IR,no more cost !

Click the image to open in full size.

Last edited by thierry38efd; 1st January 2013 at 02:36 PM.
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Old 1st January 2013, 06:11 PM   #165
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Default rePhasing a BR box

Happy New Year to all!
I've decided to enter a new phase for this year (sorry, couldn't resist)
Been working with rePhase and my woofers. On the chart below you will see 3 plots.
  • RED= Altec 416A woofer in a BR box measured at 5 feet (no crossover).
  • BLUE= Ideal 37Hz, 4th order, Butterworth high pass filter. Basically what the box is doing.
  • GREEN= Woofer and box response rePhased.
What will that sound like? Will I even hear it? Time will tell.
Attached Images
File Type: png BR-rePhased.png (22.8 KB, 213 views)
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Old 1st January 2013, 07:06 PM   #166
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Hi Pano,

are you using linear phase crossover ?
you're correcting only bass reflex delay.
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Old 1st January 2013, 07:23 PM   #167
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I am listening ONLY to the woofers. No crossover. As you can see, it's more or less flat up to 3.7Khz. I want to hear if I can detect any differences just in this very simple way.
So far, yes, I can hear it. It's subtle and not what I expected.

Adding in the mids and highs will be a completely different experience. As we know, our perception of one regiister (low, mid, high) is affected by the others.
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Old 1st January 2013, 08:12 PM   #168
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Michael, when you compare are you listeing w and w/o linear phase through the same convolution engine? I.e. normal it's just a pass through. With linear phase it does the inverse convolution.
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Old 1st January 2013, 08:37 PM   #169
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I don't know John. I just exported the impulse wave from rePhase and plugged it into my player software - JRiver Media Center. I could be that it's upside down, I don't know. Will try to figure it out. I either have convolution turned on or turned off, if that's what you mean.
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Old 1st January 2013, 08:56 PM   #170
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by default rephase linearization is an inverse all-pass.
the IR exported is corrected time

Pano,the HOLM graph you've shown is with a reverse time IR applied to correction,only to match and to check by visual.i think you've used a reverse option (in rePhase or in HOLM).

check your IR with REW,import IR as WAV,and choose "group delay" tab.
time in the lows should be negative.
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