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Multi-Way Conventional loudspeakers with crossovers

S. Harsch XO
S. Harsch XO
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Old 28th July 2015, 09:54 AM   #21
forr is offline forr  France
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Quote:
Originally Posted by xrk971 View Post
I don't know, I am not familiar with JMLC xo. Do you have a link?

JMLC quasi-optimal crossover

For a crossover frequency normalized for 1 kHz :

hi-pass : 18but at 1.1456 kHz (-3 dB), inverted polarity.
--
lo-pass : 18but at 0.8729 kHz (-3 dB), 220 ÁS time advance
(= 220ÁS time delay in the high pass section).


You'll find details in french here :

filtrage

You can play with this calculation sheet

http://nicolas.davidenko.perso.sfr.f...ltre_simul.zip

Many different quasi-optimal crossover configurations, the JMLC one being the first to be popularized, have been found with it.

There is a huge amount of discussions about them on the forums in France.

The whole idea with quasi-optimal crossovers is to get better group delay curves of the sum of the outputs than those obtained with standard configurations, and this without significantly impairing the axial responses (and preferably, with keeping the phase difference between the two outputs as small as possible).

Quasi-optimal crossovers are achieved by playing with different cut-off frequencies of the ways and a time delay for one of them.
Samuel Harsch's crossover is a typical example, it is known in France since 2009.

Last edited by forr; 28th July 2015 at 10:16 AM.
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Old 28th July 2015, 10:48 AM   #22
xrk971 is offline xrk971  United States
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S. Harsch XO
Quote:
Originally Posted by blakkshepeaudio View Post
In a previous life at a commercial speaker factory asymmetrical (passive) crossovers were the norm. Having said that, the Harsch, and XRK's derivatives, look like a neat and maybe repeatable solution for some applications. Can't wait to try this on my PAudio Coaxs !
Interesting that you bring up coax's: before I ever learned of Harsch's XO, I accidentally ran into a transient perfect step response from my coaxial Beta 8cx with CD in a dipole Z baffle using standard LR2 in an electrically symmetric setup! Acoustically it was asymmetric as can be see below:

Click the image to open in full size.

And here was IR and SR:
Click the image to open in full size.

More info on this alignment here:
http://www.diyaudio.com/forums/full-...dipole-19.html

It had me scratching my head for some time - but now I see that there are a family of asymmetric XO's that when you adjust delay, you can get a right triangle shaped SR.
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Old 28th July 2015, 12:17 PM   #23
phase_accurate is offline phase_accurate
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Coax drivers are a nice platform for several different possible transient-perfect topologies. Many TP crossovers have bad lobing behaviour which is less of a problem with a coaxial arrangement.
The fact that the tweeter is usually a little delayed relative to the woofer can also be of help in this respect.

Here you can see the step response of a Beyma 8cx800Nd with a subtractive crossover with 2nd order HP and 1st order LP. There is an additional delay for the woofer using a Bessel lowpass at some kHz. Because the group delay of the woofer isn't Bessel-like it might be better to use another filter type for the lowpass that gives a better group-delay consistency but that would have to be found by experimentation.
The measurement is inverted however but that doesn't matter.


Here
Regards

Charles
Attached Images
File Type: jpg coax_step_xov.jpg (110.5 KB, 1073 views)
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Old 28th July 2015, 01:22 PM   #24
xrk971 is offline xrk971  United States
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S. Harsch XO
I am going to explore coaxials more now and see how a Harsch XO works on them. I would imagine it will look pretty good. The XO dependent lobing issue will be minimized and that is a bonus. Where is a good frequency for XO on an 8in coax and a 12in coax to have the off axis uniformity in dispersion? Typical recommended XO freq from manufacturer is in 2.5k to 3.5kHz range. Should it be lower?
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Old 28th July 2015, 01:46 PM   #25
BYRTT is offline BYRTT  Denmark
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S. Harsch XO
Quote:
Originally Posted by ra7 View Post
X, great work as always, but I'm not convinced that there are benefits to having flatter phase. Have you done any testing that suggests you can hear the difference between perfectly flat phase and phase changes introduced by, say, LR4 crossovers? Look at rePhase. It will allow you to play with such things.

Most of the differences that people hear in different crossover topologies come from differences in the on- and off-axis frequency response.
Good points in words by your last line and to investigate would need some serious time and setups to put right and admit i haven't studied, but my subjective opinion for exactly the LR4 exercise you mention i can toggle on/off on the fly inside JRiver in the two way seen below and here must say i support X opinion it makes a difference to the better side. Some few tracks can be immune but the rest and most think really shine especially if i listen lets say an hour with and with out the IIR LR4 XO phase neutralized by the RePhase FIR filter. Subjective think it adds warm to the attacks, a little bit same as if my old pure DC coupled Sansui power amp input is feeded from a low offset DC pre sounds a little warmer than if feeded from a AC coupled pre.

(LINK: A Subjective Blind Comparison of 3in to 5in drivers - Round 2)
S. Harsch XO-fast-png


Next stepup for impressive looking SR is those that linearize phase down low even FR fall off as the SR seen at the very bottom this post, this i also tried out and made it with RePhase, it can sound impressive but a thought here is that for old recordings they were probably not mixed with such filter so a little afraid it becomes a effect in that producer probably had more normal group delay when doing his mix. Below captured picture show bwaslo answer to xrk971 regarding the nearly DC coupled looking SR seen at the very bottom this post.

bwaslo (LINK: http://www.diyaudio.com/forums/full-...ml#post4333659)
S. Harsch XO-bwaslo-png




DIYA REAL WORLD STEP RESPONSES WHEN IT GETS CLOSE TO ART :


Barleywater (LINK: FAST TC9FD DSP performace testing platform)
Click the image to open in full size.

wesayso (LINK: http://www.diyaudio.com/forums/full-...ml#post4391729)
Click the image to open in full size.

bwaslo (LINK: http://www.diyaudio.com/forums/full-...ml#post4332804)
Click the image to open in full size.
Attached Images
File Type: png FAST.PNG (88.4 KB, 1468 views)
File Type: png bwaslo.PNG (62.2 KB, 1458 views)

Last edited by BYRTT; 28th July 2015 at 01:48 PM.
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Old 28th July 2015, 02:03 PM   #26
xrk971 is offline xrk971  United States
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S. Harsch XO
Bwaslo's SR seems to go to infinity! That is art! Can you imagine the punch of a tom tom you would feel with this speaker?

Wesayso's, Barleywater's, and Byrtt's SR's - all aided with FIR techniques are all art in my book. I have yet to do the FIR route but may be going there via a hardware route with miniSHARC approach one of these days. For how low cost and easy the IIR route with IIR filters is though, I am having plenty of fun and good listening at the moment with my speakers.

The great thing about all of this is, I am sure MOST (98%) of speakers sold commercially don't even think about trying to achieve this. When you hear it, you know it. If you have not heard it, you won't know you are missing it, but if you do happen to hear it... well all I can say is that your existing speakers that don't have it, won't seem so great anymore

It is not on all tracks, but it is an effect that gives the sense of listening to the actual instrument playing and not that of a good recording and good speaker playing that instrument.
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Old 28th July 2015, 02:31 PM   #27
phase_accurate is offline phase_accurate
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The more artificial a recording is the less important is the transient accuracy. Minimalistic recordings of natural instruments profit the most. I.e. for more than 95 % of available source material it doesn't matter at all.
But since we know how to achieve it then why not try it ?

From the information theory point-of-view every deviation form the original input signal is a loss of information. In other words: An information channel with less phase-distortion has a higher channel capacity. But it is only of value if the whole chain from source to sink can actually make use of it.

Regards

Charles
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Old 28th July 2015, 11:00 PM   #28
xrk971 is offline xrk971  United States
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S. Harsch XO
Quote:
Originally Posted by phase_accurate View Post
The more artificial a recording is the less important is the transient accuracy. Minimalistic recordings of natural instruments profit the most. I.e. for more than 95 % of available source material it doesn't matter at all.
But since we know how to achieve it then why not try it ?

From the information theory point-of-view every deviation form the original input signal is a loss of information. In other words: An information channel with less phase-distortion has a higher channel capacity. But it is only of value if the whole chain from source to sink can actually make use of it.

Regards

Charles
This could be why I really notice the impact on Eric Clapton's "Unplugged" album which appears to be a minimalist produced ambient live recording in a small venue.

Another recording I have "Live at Smalls" which are live recordings from a small jazz club also seem very good.
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Old 31st July 2015, 08:08 AM   #29
xrk971 is offline xrk971  United States
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I am starting to collect data for a comparison between the Harsch XO and an LR2. I will make measurements of the response, impulse, step, and group delay. I will record a couple of sound clips and let you listen to see if you can hear a difference.
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Old 31st July 2015, 08:11 AM   #30
xrk971 is offline xrk971  United States
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For a simple comparison, I will take the data using my ScanSpeak 10F/8424 and RS225-8 2-way FAST speaker. I recently got a new LM3886 amp, so trying that out too.

Click the image to open in full size.

Speakers are described here:
10F/8424 & RS225-8 FAST Ref Monitor

Click the image to open in full size.
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