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Multi-Way Conventional loudspeakers with crossovers

"Quasi-optimal" crossover for high-efficiency loudspeaker system
"Quasi-optimal" crossover for high-efficiency loudspeaker system
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Old 16th September 2013, 12:03 PM   #51
marco_gea is offline marco_gea  Italy
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Originally Posted by marco_gea View Post
Thank you Jimbee!

So, to recapitulate, here are the simulations of three of the crossovers discussed in this thread:

(1) JMLC's original Butt 3 + Butt 3
(2) My TAD-derived LR 6 + Butt 3
(3) Jimbee's tweaked LR 6 + Butt 3

It seems as if (1) and (3) present the smoothest phase and GD curves, with (3) affording a double offset vs (1); (2) gets one the most offset, but at the cost of a relatively bumbier phase and GD...
...and (4) Jimbee's LR 6 + LR 4:

as good as (in fact, slightly better than) (3), and with a slightly larger offset - bravo!

Marco
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Old 16th September 2013, 12:08 PM   #52
PierreQuiRoule is offline PierreQuiRoule  Canada
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"Quasi-optimal" crossover for high-efficiency loudspeaker system
jmbee - Your latest filters looks like what I was looking for: offset length between the TAD and JMLC filters; well-behaved group delay; and filter orders that the drivers should work well with. It looks like a good starting point for testing.

Marco and nAr - Your hands-on experience and the side-by-side comparison of the filters are most useful - and a source of inspiration.

A question: Is anybody using Spice for their simulations? I'm entertaining the idea of simulating the effect of the driver and horn after the crossover. I have Marshall Leach's papers and files (basic simulations and his paper on simulation of the Salmon's family of horns.) Such simulation must have been done already by someone...

Another question: Is there a Spice model of the JMLC horn's profile available?

Many thanks
Pierre
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Old 18th September 2013, 05:55 PM   #53
nar is offline nar
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Quote:
Originally Posted by PierreQuiRoule View Post
jmbee - Your latest filters looks like what I was looking for: offset length between the TAD and JMLC filters; well-behaved group delay; and filter orders that the drivers should work well with. It looks like a good starting point for testing.

Marco and nAr - Your hands-on experience and the side-by-side comparison of the filters are most useful - and a source of inspiration.

A question: Is anybody using Spice for their simulations? I'm entertaining the idea of simulating the effect of the driver and horn after the crossover. I have Marshall Leach's papers and files (basic simulations and his paper on simulation of the Salmon's family of horns.) Such simulation must have been done already by someone...
I don't, but I use SPW with .zma and nude .frd for simulating real life response vs targets. It is quite predictible on the direct radiation speakers, for SPL target but phase in real life (not minimal) will be different; with the horns it can sometimes differ for SPL result in the low part of the medium curve. Phase prediction is quite precise, but not absolute.
I have seen some people using Spice and they seem to quite like it. So go for it
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Originally Posted by PierreQuiRoule View Post
Another question: Is there a Spice model of the JMLC horn's profile available?

Many thanks
Pierre
It should exist. Maybe jmmlc will help ...

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Old 9th October 2013, 07:42 AM   #54
cradeldorf is offline cradeldorf  United States
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Originally Posted by AndrewT View Post
I wonder if reading this Thread three times will get me close to fully understanding the topic?
Keep going I'm all ears.
I'll second that.
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Old 9th October 2013, 10:04 AM   #55
PierreQuiRoule is offline PierreQuiRoule  Canada
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"Quasi-optimal" crossover for high-efficiency loudspeaker system
My progress has been slow, but I will post my findings in due time.
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Old 17th October 2013, 03:19 PM   #56
marco_gea is offline marco_gea  Italy
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Default UPDATE: real measured results

Quote:
Originally Posted by marco_gea View Post
...and (4) Jimbee's LR 6 + LR 4:

as good as (in fact, slightly better than) (3), and with a slightly larger offset - bravo!

Marco
...Finally, here's the measured response of my newly realized filter of this kind (Woofer LP 36dB/oct LR + Horn HP 24 dB/oct LR à la Jimbee ), with Fx = 900Hz (as you can see, the horn is also low-passed at 7kHz, as in my case a Tweeter then takes on the last 1.5 octaves after that).

Please note the excellent ensuing linearity of the overall (Woofer+Mid) phase response till almost 3 kHz (second attachment): indeed, a "quasi-optimal" result!

Kind regards,
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File Type: png Woofer+Mid_cross.png (35.1 KB, 678 views)
File Type: png Woofer+Mid_result.png (26.7 KB, 671 views)
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Old 17th October 2013, 08:39 PM   #57
KSTR is offline KSTR  Germany
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Slightly different context, but probably worthwile to mention here :
http://www.diyaudio.com/forums/multi...ml#post2970292
The idea there was to design like no offset were present but then add a correction lowpass that delays the woofer (and filters it higer up, too) as needed, slightly adjusting some XO params in the process to get the best phase fit and amplitude flatness.
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Old 17th October 2013, 11:38 PM   #58
PierreQuiRoule is offline PierreQuiRoule  Canada
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"Quasi-optimal" crossover for high-efficiency loudspeaker system
Quote:
Originally Posted by marco_gea View Post
...Finally, here's the measured response of my newly realized filter of this kind
Wow ! This just confirmed this is a filter I want to try. Many thanks!
How does it sound?
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Old 18th October 2013, 07:53 AM   #59
marco_gea is offline marco_gea  Italy
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Well, it sounds real good to me :-) (But then, "beauty is in the eye of the beholder" - or the listener in this case, isn't it? ;-))

...more seriously: it does seem to me to produce a commendable cohesiveness in the sound across the whole frequency spectrum (in fact, rather impressively so, given the visual discontinuity between the large 15" woofer and the relatively small 1" horn). It also gives a very focused virtual image, not unlike that of a good full-range driver.

In the end, I think those who still think that systems like these (large woofer + horn) inevitably force you to renounce coherence and imaging for the sake of sheer dynamics, should do themselves a favour and give one of these "quasi-optimal" crossovers a go!

Marco
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Old 20th October 2013, 03:13 PM   #60
marco_gea is offline marco_gea  Italy
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Default To recapitulate

For the record, here's a list of "approved" “quasi-optimal” crossovers in order of increasing offset:

3rd order Butterworth Low Pass, -3dB @ Fx*0.87 (+)
3rd order Butterworth High Pass, -3dB @ Fx*1.15 (-)
Offset = 0.22*c/Fx

4th order L-R Low Pass, -6dB @ Fx (+)
3rd order Bessel High Pass, -3dB @ Fx*1.4 (-)
Offset = 0.29*c/Fx

4th order L-R Low Pass, -6dB @ Fx (+)
4th order L-R High Pass, -6dB @ Fx (-)
Offset = 0.31*c/Fx

6th order Bessel Low Pass, -6dB @ Fx*1.25 (+)
2nd order Butterworth High Pass, -3dB @ Fx*1.3 (-)
Offset = 0.40*c/Fx

6th order L-R Low Pass, -6dB @ Fx * 1.06 (+)
3rd order Butterworth High Pass, -3dB @ Fx* 1,13 (-)
Offset = 0.445 c/Fx

6th order L-R Low Pass, -6dB @ Fx * 1.07 (+)
4th order L-R High Pass, -6dB @ Fx * 0.92 (-)
Offset = 0.465 c/Fx

Marco
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