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Old 7th May 2009, 07:46 PM   #5421
ScottG is offline ScottG  United States
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I wonder with Earl's data:

..is there a filter (physical and/or electrical) altering phase and therefor time at the lower end of the pass-band?
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Old 7th May 2009, 07:48 PM   #5422
mige0 is offline mige0  Austria
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Quote:
Originally posted by soongsc

Hi Michael,

Is it possible to reduce the time scale range to simething like 1ms or less (preferably something like 0.5ms)? No smoothing?
Could do but I doubt there is enough information left in the result to allow for serious discussion.
1ms is only very few samples magnifying by 10 or so - is reading tea leaves (even more as already )



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Old 7th May 2009, 08:04 PM   #5423
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Quote:
Originally posted by xpert

Hi,

that is exactly the common misconception about CSD. From that all that insane overemphasized interpretations follow. CSD -is- group delay and amplitude over frequency and absolutely nothing more. Mathematics simply doesn't has space left for any other. You might hold me as a fool. CSD is -nothing- else than that.

This for CSD can merely be replaced with more handsome group delay and amplitude values. From these one knows which values might be critical and which not. That simple, take it for granted.

by
Hey, hey! Enough with the name-calling! "You might hold me as a fool" goes over the line. You are imagining a motive from another poster where none exists. You cannot read their mind, and neither can I, or anyone else.
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Old 7th May 2009, 08:07 PM   #5424
mige0 is offline mige0  Austria
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Quote:
Originally posted by Retsel
"CSDs can be compared to each other. But what does a difference tell about sound quality?"
...
Perhaps there is information that speaker designers can glean from such plots, but I am in the same camp as yourself. I look at them but I am not willing to make any conclusions about sound quality based on those plots.

Retsel
I'm with you - to a certain point.
First of all we have to gain sort of feeling about CSD *without* Cassandra yelling "its no science you do!" - as it certainly isn't used enough to having found a consensus among people.

And - its not that much used as it tells some "truth" about what's happening *after*.

I find it interesting to look at things that are not completely determined in its meaning - this basically is the curiosity / obsession of the scientist as well as of the busybody...

Low decay in CSD is certainly high on the list as otherwise we better would craft bells or something.
*But* if we look at the decay "generated" by radiating areas that are not infinitely small (point source) due to filters that optimise IR at a certain point well *that* could become interesting!


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Old 7th May 2009, 08:40 PM   #5425
gedlee is offline gedlee  United States
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Quote:
Originally posted by ScottG
I wonder with Earl's data:

..is there a filter (physical and/or electrical) altering phase and therefor time at the lower end of the pass-band?
No, nothing at all.

A waveguide/compression driver is going to ring below "cutoff" because the transition is very sharp. You have two mechanical HP filters in series.
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Old 7th May 2009, 09:39 PM   #5426
ScottG is offline ScottG  United States
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Quote:
Originally posted by gedlee


No, nothing at all.

A waveguide/compression driver is going to ring below "cutoff" because the transition is very sharp. You have two mechanical HP filters in series.
Bummer.

(..I understood the contribution of the waveguide and primary resonance for the driver, I just thought there might have been an additional contribution.)

The result doesn't look good to me. It isn't bad, (and certainly far better than most large sd drivers up that high in freq.), but it isn't good either. At least in this respect, most *good* tweeters will exceed this level of performance. (..you can toggle through Zaph's tweeter "mishmash" for comparisons.)
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Old 7th May 2009, 09:41 PM   #5427
pjpoes is offline pjpoes  United States
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can such a comparison be made given that they weren't measured in the same fashion?
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Old 7th May 2009, 09:47 PM   #5428
ScottG is offline ScottG  United States
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Quote:
Originally posted by pjpoes
can such a comparison be made given that they weren't measured in the same fashion?
Yes. However its degree of accuracy, (as a comparison), is the major question. I would not be surprised if Zaph were to test it just has he has done with the tweeter grouping, that a fairly similar measurement would be the result. (..the same, no.. broadly comparable, yes.)
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Old 7th May 2009, 09:51 PM   #5429
BudP is offline BudP  United States
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Since my OX is being gored here, as an example of something that introduces more "distortion" that is pleasing, let me point you to a blink comparison of the same aluminum cone, treated and untreated, by John K himself.

I trust Johns work and all of you should wander over to this particular spot and blink the results. Please look carefully at the resonant node and how it decays, not that it takes the same time, but that the EnABL'd driver shows the actual ringing of the major node at 9 kHz.

http://www.diyaudio.com/forums/showt...31#post1461231
or here http://planet10-hifi.com/johnK-test/
For the rest of the information in these two plots, interesting as it is, they provide me with NO information that would be useful in determining what else to do to these drivers to remove the noise in and thus from the driver, that veils information 60 db down, that is also first arrival signal, in real music reproduction circumstances.

For me, a real exploration of what all of the driver altering technologies provide and the need to alter the design of or even create a driver design, I need a much deeper look than just this surface view. Is it possible to perform this sort of layered signal test and extract the data Michael?

Bud
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Old 7th May 2009, 09:58 PM   #5430
pjpoes is offline pjpoes  United States
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I'm basing my comment on Zaph's on cautions about comparing data in his graphs. Every time he makes some change in how he measures things, he talks about not comparing the old to the new.

I personally think that Zaph focuses too much on the wrong things in tweeter measurements, and not on what really counts. He focuses a lot on things like distortion, smooth response, etc. However, a smooth response can be had with Dr. Geddes tweeter, as is evident from his system response, so while the tweeter, with no crossover, might not be completely smooth, it will be in the end. As for distortion, I don't think the kinds that get so focused on matter. A waveguide and compression tweeter offer far greater sensitivity, and as a result, are capable of far greater output without distortion to a far lower frequency. This allows designs like Dr. Geddes, which can play at realistic levels, without a crossover at 3khz. Then there is what Dr. Geddes will tell you as the most important factor, the power response. Most of those tweeters with better CSD's are direct radiating designs with terrible power responses. As you look more and more off axis the response becomes more and more "yucky". The power response of the waveguide/compression driver allows a very smooth and even repsonse over a wide listening area.

While my experience is just that, my experience, and my views are based on limited experiences, It has been my experience that direct radiating tweeters can not play at realistic levels without audible compression, unless crossed over fairly high. Speakers with crossovers over 2khz have, in my experience, not had as deep or holographic a sound stage as speakers crossed below that point. I can give no technical reason why that is, so while very subjective, its all I got for crossover point. However, power response issue is very important for both qualitative and technical reasons. Again, speakers using direct radiating tweeters have, in my experience, had a less smooth power response when measured over a wide enough angle, and it creates issues in what you hear at the listening position. I really like the ability of controlling smoothing the off-axis response, and avoiding 1st reflections that way. I much prefer the sound of a speaker whose sweet spot is that much wider and smoother as well.
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