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Multi-Way Conventional loudspeakers with crossovers

LXmini: i see an issue
LXmini: i see an issue
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Old 22nd May 2020, 05:06 PM   #1
Jabbejokker is offline Jabbejokker
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Default LXmini: i see an issue

I'm a big fan of Linkwitz. Just now some commercial speakers are beginning to play with solutions to the cardioid dispersion question.

Here is my hangup: I understand that the omnidirectional nature of the horizontal driver combined with the dipole creates a cardioid response. What I don't understand is that they are crossed over at 700hz and as such will only exhibit cardioid dispersion patterns close to the crossover frequency. Above the x-over being a pure dipole and below an omni. I'd imagine one would have to run two full range drivers in that same physical config crossed over to a woofer in order to gain cardioid dispersion characteristics throughout the frequency range above woofer crossover.

Am I missing something?
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Old 22nd May 2020, 05:28 PM   #2
kevinahcc20 is offline kevinahcc20  United States
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Have you auditioned LXmini? I am listening to mine now and the sonic signature, although not able to go as deep or as loud is quite comparable to the Orion 3.3.1 in my other listening room.
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Old 22nd May 2020, 06:44 PM   #3
Jabbejokker is offline Jabbejokker
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Quote:
Originally Posted by kevinahcc20 View Post
Have you auditioned LXmini? I am listening to mine now and the sonic signature, although not able to go as deep or as loud is quite comparable to the Orion 3.3.1 in my other listening room.
I haven't. I'm not really that concerned with bass extension but more interested in the concept of cardioid dispersion. To me it would seem like that the isn't much cardioid dispersion going on based on what I wrote above. Linkwitz is a much smarter man than I so I was hoping for someone to clarify that for me.
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Old 22nd May 2020, 08:00 PM   #4
DampedAndDriven is offline DampedAndDriven  United States
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Default LX mini

Without going back & looking at Linkwiz's webpages, IIRC the upper driver has a gapped "absorber/diffuser" structure behind it which would lessen the effective rearward radiation. So maybe roughly approximating cardiod outlay for some range above the XO.
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Old 22nd May 2020, 10:35 PM   #5
kevinahcc20 is offline kevinahcc20  United States
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You are correct, the FR driver is magnet mounted in an open back PVC tube lightly filled with acoustic fiber stuffing and there is a significant gap between the mounting flange of the driver and the front edge of the PVC tube.
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Old 22nd May 2020, 11:20 PM   #6
DampedAndDriven is offline DampedAndDriven  United States
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Default LX mini per DA MAN

Found SL's explanation in the design page for LX mini:
LXmini design

The page shows measured responses but here's the text:

"If a dipole point source is added to a monopole then unidirectionl or cardioid radiation is obtained when both sources contribute equally to the total sound. Here I use a 700 Hz LR2 crossover between monopole and dipole. The dipole consists of a small full-range driver mounted above the woofer section. Due to the transition from monopole to dipole radiator the cardioid polar response is only obtained around the crossover frequency. At higher frequencies the dipole radiates equally well to the rear as to the front.

"The rear radiation from the dipole must be attenuated or scattered and diffused in order to minimize the influence of a large reflecting surface behind the dipole radiator. The cylindrical body behind the dipole driver serves that purpose as its dimensions are in the fractional wavelength range of the frequencies concerned. There is a small gap between the magnet and the inside of the pipe. The rear is open and stuffed with absorbent material for very high frequency attenuation. ...."
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