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Multi-Way Conventional loudspeakers with crossovers

Crossover and time delay/offset, for horns particularly.
Crossover and time delay/offset, for horns particularly.
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Old 22nd November 2019, 06:52 AM   #21
Dave Zan is online now Dave Zan  Australia
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Originally Posted by Dave Zan View Post
...The point is that it has half the excess phase of a similar filter without offset...
It occurs to me that this depends on what it means to say "similar" filter.
The excess phase is low for a similar 8th order lo-pass.
But more or less identical excess phase to the not-very-steep hi-pass.
So no real improvement if the constraint is the hi-pass, and it usually is.
Simpler to just put in an all pass delay in the woofer and be done with it.
Have to think if the idea can be saved.
Otherwise, phase linearization could be done with rePhase as an option, to learn if it makes any difference.

David
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Old 22nd November 2019, 08:04 AM   #22
phase_accurate is offline phase_accurate
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Its group delay is approximately 70% less than that of an LR 4 @ 1 khz. If a high order on the lowpass plus lower group delay is your concern then go for it.
I use some topology myself that would have about 50% more group delay than yours but which is 3rd order on the highpass and whose group delay is slowly dropping (like two cascaded 2nd Order Filters with a Q of 0.4). But it is only 2nd Order LP doesn't compensate for the delay of the horn offset. That one I do with an additional Bessel LP on the woofer path.

Regards

Charles
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Old 22nd November 2019, 09:42 AM   #23
marco_gea is offline marco_gea  Italy
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Originally Posted by Dave Zan View Post

...

4. The hi pass is 3rd order, probably the practical minimum when both acoustic and electrical roll-off combine.

...
With a typical real-world horn, you'll find that even a 3rd order high-pass is not achievable in practice. What you'll end up getting, invariably, is a non-standard acoustic slope, with two separate "knees", one at Fx (crossover freq.) and one at Fc (horn cutoff). The result is a higher slope below Fc, AND more phase shift at and below Fx than predicted by a "simple" ideal high-pass.

The best way to approach this kind of simulation is not to try and simulate any combination of textbook HP & LP filters (even if asymmetrical) applied to ideal infinite-bandwith drivers.
Rather, it is to start with a simulated horn driver (with a 4th order or often even 6th order "natural" high-pass at Fc), and then superimpose the electrical HP on that.

Marco
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Old 22nd November 2019, 10:12 AM   #24
AllenB is offline AllenB  Australia
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Yes, a horn can cut off sharply with a lot of phase changing. A waveguide has much less group delay and can more easily be manipulated through this region.

I feel that it might be better once delay goes up as frequency drops, that it should stay on this new level. Feel free to set me straight if that's not true.
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Old 22nd November 2019, 10:39 AM   #25
marco_gea is offline marco_gea  Italy
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I feel that it might be better once delay goes up as frequency drops, that it should stay on this new level.
Your blue trace is not achievable in real life. That was my point.

No idea what you mean by "that it should stay on this new level".

Marco
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Old 22nd November 2019, 10:49 AM   #26
Boden is offline Boden  Netherlands
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A reasonable starting point for any simulation here would be at least 6th order highpass imo.
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Old 22nd November 2019, 11:23 AM   #27
AllenB is offline AllenB  Australia
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I did show a real world example in post #5

You are right, but I don't think it matters. The first point of this exercise was to show that you can use electrical manipulation to take a delayed driver and sufficiently bring both phase and response into line at the same time.
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Old 22nd November 2019, 11:25 AM   #28
AllenB is offline AllenB  Australia
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Originally Posted by marco_gea View Post
No idea what you mean by "that it should stay on this new level".
That the plot should shelve up, rather than peak.
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