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Multi-Way Conventional loudspeakers with crossovers

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Old 24th April 2020, 05:01 PM   #1501
454Casull is offline 454Casull  Canada
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Originally Posted by mabat View Post
As for this experiment with the convex side of the diaphragm, my whole reasoning was that it must be easier to get a spherical wavefront from that side than from the concave one (via phase plug and OS throat). I think I will at least give it a try in the simulator to see what I can get. Just in case someone wrote that it's completely silly and why, I would save some effort.
Well, the further parts of the diaphragm will be out of phase with the center since the sound has further to travel. You'll get cancellation as wavelengths get shorter and more out of phase.
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Old 24th April 2020, 05:05 PM   #1502
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The BMS4550 ring radiator compression driver has a conical throat. Being a ring radiator, there is no radiation from the center to be out of phase with and the driver is reputed to produce a spherical wave front.
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Old 24th April 2020, 05:06 PM   #1503
mabat is offline mabat  Czech Republic
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454Casull
Sorry, I don't follow.

Quote:
Originally Posted by nc535
...and the driver is reputed to produce a spherical wave front.
Would be nice to have it measured. That reminds me that a PWT for this is waiting to be "calibrated".
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Last edited by mabat; 24th April 2020 at 05:09 PM.
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Old 24th April 2020, 05:23 PM   #1504
454Casull is offline 454Casull  Canada
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454Casull
Sorry, I don't follow.
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Old 24th April 2020, 05:29 PM   #1505
mabat is offline mabat  Czech Republic
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Hmm.. Are you sure it works like that?
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Old 24th April 2020, 05:44 PM   #1506
454Casull is offline 454Casull  Canada
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Hmm.. Are you sure it works like that?
Yes

Phase Plugs

For what it's worth, it's a lot easier to design an effective phase plug for a concave diaphragm than it is for one that is convex, simply due to the geometry. Unfortunately, concave dome tweeters are extremely rare. The only ones I know of (that might still be available) are the Focal Utopia tweeters which I'm not even sure are great tweeters to begin with.

Last edited by 454Casull; 24th April 2020 at 05:46 PM.
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Old 24th April 2020, 05:48 PM   #1507
mabat is offline mabat  Czech Republic
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That would make absolutely no difference here, right?
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Old 24th April 2020, 06:24 PM   #1508
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Originally Posted by mabat View Post
Fair enough. I see a typical axial hole that I also see in the sims when the mouth termination is too abrupt and that goes away when the mouth flare is more gradual. That's all I can say...
Let me understand your point. Do you claim that there is a curve C, from a fixed angle T, on an OS waveguide to some outer radius R that is ideal in that there is no hole on axis? By far the easiest to design, but not the smoothest transition I will admit, is a simple radius, which I used. Now is there a known curve C between those two constraint that eliminates the hole? If this has been reported then I must have missed it.

I can see some improvement in the hole via a different curve C, but I cannot see how it could be eliminated.
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Old 24th April 2020, 06:34 PM   #1509
gedlee is offline gedlee  United States
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OK. In the end, the whole loudspeaker won't have a constant DI, that's for sure. It will rise and then (say) stays constant. Thus there is no reason why one should be using the waveguide only in the range where it has a constant DI since a good waveguide won't have an erratic DI below this range - it will fall gradually. So, some portion of the raising DI part can be left to the waveguide. That lowers crossover point and also the DI values at this frequency. And from my experience (don't have the plots at hand), this is then a lot less critical than say at 1 kHz. Partly due to the better C-C.
If the underline is true then I understand completely.

But this is not true in all cases for sure. I mostly see the waveguide DI rise before it drops, it's not a smooth transition. If you operate below that point then you are building in that aberration.

Do you have examples of a waveguide whose DI drops in a "smooth" way. That's not how I remember things.
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Old 24th April 2020, 06:43 PM   #1510
454Casull is offline 454Casull  Canada
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That would make absolutely no difference here, right?
Which part?
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