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Multi-Way Conventional loudspeakers with crossovers

A little addition to multiway crossovers a la Linkwitz: multi-cascading
A little addition to multiway crossovers a la Linkwitz: multi-cascading
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Old 15th January 2019, 11:08 PM   #41
KSTR is offline KSTR  Germany
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Quote:
Originally Posted by scottjoplin View Post
I'll try one more time Are some people talking about phase matched across all the drivers at all frequencies?
Yes, this is the goal and can be perfectly achieved (I'll post an example later -- 2.5-way with delay compensation for a slighty forward tweeter, curently I'm on a Linux machine, need to install WINE and LSPcad on this first). Of course inter-driver phase is not relevant anymore once the targeted response of a driver is down some 30dB or so.
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Old 17th January 2019, 09:23 AM   #42
KSTR is offline KSTR  Germany
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... here we go.
2.5-Way target with 100% coherent phases. Shown is
- synthesis circuit
- SPL responses (with total phase)
- Phase responses (which are all the same and identical to the total phase)

System highpass is Bu5@40Hz, Butterworth 5th order (equivalent of ported bass with 1st order protection).
Woofer roll-off is LR2@500Hz, Linkwitz-Riley 2nd order.
Mid-to-tweeter XO is LR4@2000Hz, Linkwitz-Riley 4th order.

This would be a usable target for a small 2.5-Way with 4"...5"-midwoofers and a nice, low-Fs 1" dome.

The key point is that the woofer low-pass (WfLP) phase contribution is mimicked in the allpass cell (WfLP-comp) in the midrange and tweeter paths. The total phase contribution of the XO is that of a 3-way with LR2@500Hz and LR4@2000Hz, so this is where the (small) penalty is. But excess phase can always easily be removed with FIR-phase-unrolling applied to the source signal.

Of lesser importance here (because the Mid-Tweeter XO is high) is that the system highpass is applied to all ways.

Last edited by KSTR; 17th January 2019 at 09:27 AM.
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Old 17th January 2019, 10:52 PM   #43
Dave Bullet is offline Dave Bullet  New Zealand
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In SL's pictures - why for both bandpass driver networks (W) and (M) - is W lower in amplitude vs. M when both are direct from source (not cascaded)? Why is W automatically lower? Shouldn't M suffer the same fate being a bandpass also? or is SL's argument the longer wavelengths provide more opportunity for destructive phase lowering output between SW - W - M?
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Old 18th January 2019, 09:00 AM   #44
KSTR is offline KSTR  Germany
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The drop in level is going with the inverse of the distance of surroung XO point freqs because phase mismatch is larger and the sum (which is a vector sum, then) drops. With 90 phase mismatch, for example, the sum of two equal sound pressure magnitudes is only sqrt(2)=1.41 times the magnitude.
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Old 18th January 2019, 01:18 PM   #45
Boden is offline Boden  Netherlands
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Probably I am misunderstanding something here, but if we go back to Robbin’s original VituixCad picture in post 1, we have a (sub) woofer, crossing over at 120hz with 24 dB octave. Now this driver is further rolled off at 1000 Hz and 10000 Hz.
At 1000 Hz this (sub)woofer is already 62 dB down, then rolled again with 24 dB/octave. Then, again, when this (sub)woofer is below -100 dB relative to its passband, it is rolled off again with 24 db. So final steepness above 10000 Hz is 62 dB/octave
If I understand it all correctly, the idea is that that introduction of further phase shift in the stopband, way past any reasonable level ( past -40dB!) would contribute to better system integration.
To be honest, I do not see that immediately. In a twoway-system, yes, its is relevant.
But here, in a 4 way? Would not the passband phase characteristic of the “active” driver in question determine system phase behavior only, whereas the drivers in their stopbands do not contribute anything to system behavior below minus 40dB?
It also raises the interesting question as to how much attenuation in the stopband of a driver would still affect any system contribution. In other words: are driver anomalies below, say, -40 dB, irrelevant?
Maybe Robbin and KSTR can shed some light on this.
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Old 18th January 2019, 01:43 PM   #46
ILikeFoodz is offline ILikeFoodz  United States
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I think that's a good question Boden, and it has relevance to other aspects of speaker design as well. For instance, 3rd order harmonic distortion of drivers is often in the -50 to -70 dB range at 2.83 V. Does a -65 dB driver sound better, all else being equal, than a -55 dB driver? Does the THD of your electronics that run your speakers actually matter below .1% or so?

These questions have been debated long and hard on this and other forums
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Old 18th January 2019, 03:16 PM   #47
KSTR is offline KSTR  Germany
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Quote:
Originally Posted by Boden View Post
In other words: are driver anomalies below, say, -40 dB, irrelevant?
Yes, if you get phase tracking down to -40dB points this is a most excellent result, actually -30dB may be considered as sufficient.
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Old 23rd January 2019, 11:41 AM   #48
Robbintip is offline Robbintip  Netherlands
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ILikeFoods has understood the point of the theory. In practice, Boden has a valid point. How many layers of cascading you are willing to add depends on the listener, and the setup.
A friend of mine has now implemented multi-cascading in his three-way consisting of SB WO-24, SB MW16, DXT tweeter. Stereo-imaging improved greatly, driver integration improved. He does not ever want to switch back to non-cascaded. His friends in turn commented on the stereo image and are asking about how it was achieved.

I would really like it if people try it. You can always revert to the old situation if you don't like it.

An analogy I can compare it with is making a picture. If you zoom in, you can see what's there in the distance. If you then focus, the image suddenly becomes clear.
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Last edited by Robbintip; 23rd January 2019 at 11:46 AM.
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Old 23rd January 2019, 04:35 PM   #49
Davey is offline Davey  United States
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Robbin,

What you've proposed here is identical to the "improved topology" (cascaded) as shown by Linkwitz in your first post.

Do you see it? (Look closely.)

Dave.
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Old 24th January 2019, 09:31 AM   #50
Robbintip is offline Robbintip  Netherlands
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It is only the same for the tweeter.
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