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Old 2nd May 2013, 01:52 PM   #1
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Default 3way 2way speakers

A standard 2nd order 2 way crossover has the drivers connected out of phase, because this makes them in phase acoustically at the crossover frequency.

I was looking into a speaker (Beovox S 45-2) and it had an interesting design feature that I have never come across, and wondered what your views on it are.

This design has is the 2 drivers connected IN phase, which of course means there is a suck out at the crossover. However a 3rd driver is used to fill in just the frequencies of the suckout. I think this uses a 1st order band pass crossover.

The intended benefit is a phase coherence over the whole frequency range.(because of course 2 way 2nd order drivers are acoustically out of phase except at the crossover)

Any thoughts?
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Old 2nd May 2013, 04:09 PM   #2
fpitas is offline fpitas  United States
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(because of course 2 way 2nd order drivers are acoustically out of phase except at the crossover)

Except they're not. You're ignoring the phase shift from the crossover networks, which reverses the relative phases everywhere. In the stopbands of the lowpass or highpass filter, you'll have 180 degrees phase shift; in the passbands, 0 degrees. At the crossover, each is 90 degrees with the lowpass lagging, the highpass leading.

Last edited by fpitas; 2nd May 2013 at 04:20 PM.
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Old 2nd May 2013, 05:21 PM   #3
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Could be that the hole of silence between the tweeter and woofer could not be patched up, no reach, and a third driver was needed. Do you own these speakers? What do they sound like? Muddy? Harsh? Painful? Welcome to main stream audio on planet Earth.

If you are going to listen to 2-way speakers face on, bad idea, it doesn't matter what polarity the drivers are. The drivers are reversing the phase on their own by the difference in distance of the magnets to your ears. But only at one frequency. Then, if you switch the polarity of one driver and believe you have the right solution, again the difference of distance to your ears will undo what you did, but at other near-by frequency, and you are back to fail. This is if you listen to them face on.
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Old 2nd May 2013, 06:09 PM   #4
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Hello fpitas

It would seem that my source material is wrong: "An Introduction to Loudspeakers and Enclosure Design" V. Capel, in which he states, if the tweeter connection is reversed in a 2 way 2nd order crossover then "A further effect is that all the high frequencies are in an opposite phase relationship to the low, compared to what they were in the original signal".

Also it would seem that the explanation of the design by GordonW on Audiokarma is complete crap, and furthermore that B&O are bonkers, creating a problem by connecting the main driver and tweeter in phase to only solve the FR dip by using a 3rd driver (the non crossover frequencies now being 180 degrees out of phase as you say). Are all these people idiots?
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Old 2nd May 2013, 06:22 PM   #5
fpitas is offline fpitas  United States
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Quote:
Originally Posted by midrange View Post
Hello fpitas

It would seem that my source material is wrong: "An Introduction to Loudspeakers and Enclosure Design" V. Capel, in which he states, if the tweeter connection is reversed in a 2 way 2nd order crossover then "A further effect is that all the high frequencies are in an opposite phase relationship to the low, compared to what they were in the original signal".

Also it would seem that the explanation of the design by GordonW on Audiokarma is complete crap, and furthermore that B&O are bonkers, creating a problem by connecting the main driver and tweeter in phase to only solve the FR dip by using a 3rd driver (the non crossover frequencies now being 180 degrees out of phase as you say). Are all these people idiots?
No idea. What I said is simple filter theory, take it or leave it.

Look about 1/4 down the page for 2nd order filter phase vs. frequency graphs:
http://www.analog.com/library/analog...relations.html

Last edited by fpitas; 2nd May 2013 at 06:41 PM. Reason: Added clarifying link
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Old 2nd May 2013, 08:49 PM   #6
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Hello again

This has been very interesting, and because I started from a position of ignorance, very educational. But that Beovox S 45-2 design sure is unusual.
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