48db/oct crossovers causing listening fatigue? - Page 2 - diyAudio
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Old 16th January 2013, 05:22 AM   #11
ra7 is offline ra7  United States
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Originally Posted by pos View Post
The phase coherency is the most important (and most overlooked) part IMHO, and if messed up it can have an impact on the slopes you will prefer: shallower slopes might typically become more "acceptable" in such situations, as it will tend to "blur" any phase issue...
Yes, this is very important. The phase of the two drivers must overlap through the crossover region, and at least until individual driver output has fallen to -24 to -30db.
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Old 16th January 2013, 12:32 PM   #12
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It doesn't help either sometimes that the steeper slopes place greater demands on the driver immediately prior to the XO frequency, which they may not thank you for; a point I recall Zaph also makes a couple of times on his site.
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Old 16th January 2013, 12:34 PM   #13
Bazukaz is offline Bazukaz  Lithuania
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Hi,

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Originally Posted by pos View Post
Bazukaz,
You can try to isolate the amplitude slope issue (your "a" explanation) from the phase shift issue ("b") by using rePhase
Thanks for idea. That is interesting. Now I think a phase shift filter(Q=2, right?) could be used to process some music and listened through headphones for "fatiguing" and "audible" difference in a blind test.
Anyone could suggest a program for that? I have found some but not for 48db/oct slopes, and rePhase can only generate but not re-process existing files.

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Originally Posted by ra7 View Post
Yes, this is very important. The phase of the two drivers must overlap through the crossover region, and at least until individual driver output has fallen to -24 to -30db.
I am using a symmetrical filter, and drivers have adequate dispersion at crossover region. IMO phase should overlap but I did not measure this except for frequency response(to check if drivers are summing properly).
However there will always be variations in phase difference from different listener positions as drivers are offset from each other. Is it important to optimize in the front at 1m?

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Lukas.
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Old 16th January 2013, 01:11 PM   #14
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Optimally driver centers should be located <1/4 wavelength apart to minimize lobing/off axis. Measurement distance should be several times the enclosure's width, and gated/windowed to remove reflections from room.


Quote:
Originally Posted by Scottmoose View Post
It doesn't help either sometimes that the steeper slopes place greater demands on the driver immediately prior to the XO frequency, which they may not thank you for; a point I recall Zaph also makes a couple of times on his site.

I don't recall Zaph on this, but how does reducing out of band signal add to driver demand? This is nonsense.
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Old 16th January 2013, 01:39 PM   #15
Bazukaz is offline Bazukaz  Lithuania
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Originally Posted by Barleywater View Post
Optimally driver centers should be located <1/4 wavelength apart to minimize lobing/off axis.
Yes I understand this well. However quarter wavelength at 2.5 kHz is just ~3.5 cm and this is obviously almost never possible to achieve between driver centers.
Also when the listener is moving in the room phase will be shifting constantly and different depending on frequency; combined with offset drivers this gives phase corrections across a wide range of positions mostly meaningless IMO.
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Old 16th January 2013, 02:29 PM   #16
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Accepting this in design, and assuming vertical driver axis then lobes are vertical too.

Steering main lobe horizontal at listener to +/- 5 degrees requires timing control better than 6 microseconds, regardless of crossover slope and driver spacing.

With DSP each driver may be EQ flat through crossover region yielding better acoustical sum with crossover.
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Old 16th January 2013, 03:20 PM   #17
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Originally Posted by Barleywater View Post
I don't recall Zaph on this, but how does reducing out of band signal add to driver demand? This is nonsense.
Scott was speaking of the demand in amplitude just before the slope. I have read this on the Zaph site as well (although I can't recall where) but he mentions that he decided to go with a second order slope instead of fourth order because the slope started earlier on the 2nd order, as in a lower Q.
I believe it was pertaining to a tweeter.
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Old 16th January 2013, 03:24 PM   #18
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Exactly.

Take, say, LR4 and LR6. Since LR4 begins its rolloff at at a higher frequency, amplitude demands on the tweeter are reduced compared to LR6 which forces it to work harder to a lower frequency. Which is the better tradeoff? YMMV on that score, especially given the host of other factors at work.

Here's the above mentioned example: it's talking LR2 & LR4 but you get the idea: Zaph|Audio


Edit: Finally found it. See the XO section & the remarks on tweeter power handling: http://www.zaphaudio.com/BAMTM.html

Last edited by Scottmoose; 16th January 2013 at 03:37 PM.
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Old 16th January 2013, 03:30 PM   #19
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Thanx for finding that, my OCD wouldn't let me stop looking
Now, I can go about my day!
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Old 16th January 2013, 03:36 PM   #20
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Edited the above with the other link on tweeter powerhandling; LR4 & higher orders. Interesting point. Especially as I currently have a liking for v. low XO frequencies with extremely steep slopes. Jon Marsh's evil influence no doubt.

Last edited by Scottmoose; 16th January 2013 at 03:38 PM.
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