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Can't connect to database, trying again.... RE: "Once you go dipole you never go back." - Dave_K - Speaker Asylum

Home Speaker Asylum

General speaker questions for audio and home theater.

RE: "Once you go dipole you never go back."

I have not heard the LX521. I have heard the Orion and it was very good.

I just don't believe the claim of flat to 20 Hz though. And it seems to contradict Linkwitz's own measurements that you linked to.

I do believe the claim of -3 dB @ 30 Hz in a ground plane measurement. But an anechoic or free field measurement of a loudspeaker is not representative of its performance in the "pressure region" of frequencies below the lowest room mode. For a monopole, the free field response will understate the in-room response in that frequency range. For a dipole, the opposite is true, the free field response will OVER-state the in-room response in that frequency range.

Here's why: In the pressure region, which is the frequency range below the modal region, the longest room dimension is less than one half of the shortest wavelength. Therefore, there is no wave front and no radiation pattern to speak of. The pressure in the whole room just rises and falls. With a sealed monopole subwoofer, the room pressure increases on the outward stroke and the box pressure falls, and the room pressure decreases on the inward stroke and the box pressure rises. With a dipole, with one side pushing and one side pulling there is no net pressurization of the room. If not for air resistance, you wouldn't get any sound at all. The reason why a free field measurement is different is that the volume is infinite so there is no pressure region. In free space, the dipole will radiate a dipolar pattern even down to the lowest frequencies. That doesn't happen in a room.

If you don't believe me, you can see it in Linkwitz's in-room measurements.


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  • RE: "Once you go dipole you never go back." - Dave_K 10:49:06 06/03/16 (0)

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