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Old 6th August 2010, 12:53 PM   #7021
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Now, keep the end of the window where it is (red line) and move the start to just before the main impulse. Then we will have something I think will be meaningful.
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Old 6th August 2010, 01:10 PM   #7022
mige0 is offline mige0  Austria
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In case some might like to look at the CSD of that „cut out“ reflections :

Full dampening
Click the image to open in full size.



Less dampening
Click the image to open in full size.



Zero dampening
Click the image to open in full size.



Last CSD plot (zero dampening) tells us that the peak at roughly 1kHz is building up after some time :

Click the image to open in full size.

Michael

Last edited by mige0; 6th August 2010 at 01:14 PM.
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Old 6th August 2010, 01:31 PM   #7023
mige0 is offline mige0  Austria
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Quote:
Originally Posted by john k... View Post
Now, keep the end of the window where it is (red line) and move the start to just before the main impulse. Then we will have something I think will be meaningful.

Ok – here we go:


Full dampening

Click the image to open in full size.
Click the image to open in full size.


Less dampening

Click the image to open in full size.
Click the image to open in full size.


Zero dampening

Click the image to open in full size.
Click the image to open in full size.




Michael
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Old 6th August 2010, 03:45 PM   #7024
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Quote:
Originally Posted by john k... View Post
Now, keep the end of the window where it is (red line) and move the start to just before the main impulse. Then we will have something I think will be meaningful.
I can't see where have more room reflections make anything more meaningful. Just me I suppose,
Dan
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Old 6th August 2010, 06:37 PM   #7025
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I was really scratching my head about this wiggle of the TD15M. Looked up half a dozen responses of 12" & 15" drivers at Brandon's Driver Measurements - drivervault and all had that same thing more or less.

I think it is a delayed damped back-bounce from the shockwave through the type of spider used for that sort of pro drivers, isn't it? Or is that too simple?


If it were stable (linear) and predictible in character pre-distortion of the driving current (per FIR-filter in the digital domain) should be able to correct for this, trying to terminate the reflection mechanically. Essentially the same strategy that digital room-equalization tries to use, but this time the dimension of the problem is 1, it's 1D and therefore much better suited to impulse response correction techniques, to the extend that the effects are not too non-linear (drifts included).

Ony may argue though if it's worth the effort, or favorable at all, besides the "digital stuff" involved. Well, maybe that delayed wiggle is part of the trademark sound of this class of drivers...

Last edited by KSTR; 6th August 2010 at 06:47 PM.
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Old 6th August 2010, 07:30 PM   #7026
mige0 is offline mige0  Austria
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Quote:
Originally Posted by KSTR View Post

I think it is a delayed damped back-bounce from the shockwave through the type of spider used for that sort of pro drivers, isn't it? Or is that too simple?
.

Delay time of 2.3ms seems to be too long for that to enter the picture IMO

*If* its in the driver itself, I'm rather with John K that it may be from cone modes in break up.
There is another reflection to be identified earlier on (and slighty higher in frequency) but not exactly half of that 2.3ms - so it might or might not be part of the mechanism - for sure its *not* a simple looped reflection, otherwise time would be pretty exactly halved and also we should see pronounced subsequent reflections later on.

There is also a specialty with those speakers in general - the are more of a horn . actually a moving horn - than other speakers, as they have no dust cap and hence more "horn length"
It could well be we see an interference (beat) of the sound created at the throat+ "amplified by the horn" with the sound created at the rim.

Michael

Last edited by mige0; 6th August 2010 at 07:37 PM.
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Old 6th August 2010, 07:48 PM   #7027
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Micheal, check back a few pages for my graphs on a pro 12" driver and the effects of damping the cone on both the impulse and break up.

Dan
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Old 6th August 2010, 07:49 PM   #7028
KSTR is offline KSTR  Germany
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Yes Michael, seems you are right. I've gone through the recent posts more thoroughly and have to agree that it most likely is breakup (and not a cabinet reflection either... Ockham... now I got it). Anyway, interesting how it sounds in slow-mo and how long the delay is...
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Old 6th August 2010, 08:12 PM   #7029
mige0 is offline mige0  Austria
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Quote:
Originally Posted by dantheman View Post
Micheal, check back a few pages for my graphs on a pro 12" driver and the effects of damping the cone on both the impulse and break up.

Dan
Are you referring to this one ?

Beyond the Ariel

Beyond the Ariel

Beyond the Ariel


If so - what are you telling us ?
I didn't got the point and also how its related to Dan's measurements ?

Michael
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Old 6th August 2010, 10:57 PM   #7030
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Quote:
Originally Posted by mige0 View Post
Ok – here we go:


Full dampening

Click the image to open in full size.
Click the image to open in full size.


Less dampening

Click the image to open in full size.
Click the image to open in full size.


Zero dampening

Click the image to open in full size.
Click the image to open in full size.




Michael
I think just the full 5 msec window tells a lot. That thing is nasty above 1k Hz. Time to look at a measurement with a 500 Hz 4th order LP filter.
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