Modal behavior/dipole subs

[Jack Gilvey]

Can anyone point me toward any measurements that compare how dipole and monopole differ in how they excite room modes?

[JonMarsh]

There's a lot of discussion back and forth on that; SL's done some studies, too; look on his site.

Setup is very important in evaulating this; consider the Cardas and Wilson techniques for getting monopole systems setup. Most people get no where near there.

The bottom line is how does it sound, in the positions you're likely to be able to use.

Sorry to be so terse, but time limited.

Oh, and in a blast from the past, the newest Sterephile has a review of the Legacy Whisper, a system that Thomas and I "Kloned" about ten years ago, and which convinced me of the desirability of dipole operation in at least the 50 Hz to 300 Hz area.




I even visited the Legacy factory (quite a few years back). Was a bit dissappointed after I saw the component quality in the crossovers, but not surprise after I heard a demo at the factory turned up too loud with obvious core saturation effects in the crossover (think ferrite bobbin inductors, electrolytic caps).

[Jonasz]

Maybe you can find something om John K's site? http://www.musicanddesign.com/tech.html

[Rudolf]

Can anyone point me toward any measurements that compare how dipole and monopole differ in how they excite room modes?

This is in german but it contains measurements done for monopoles, dipoles and cardioids at 3 different positions in a room:

http://www.randteam.de/papers_lf/tmt_22_2002-lf-01.pdf

A word of caution: Since these measurements don´t include different orientations of the dipole and cardioid, the full potential of those principles is not exploited.

Rudolf

[Jack Gilvey]

Thanks, gents.

The bottom line is how does it sound, in the positions you're likely to be able to use.

Indeed. I'm trying to deal with some modes that seem to defy lots of OC705 bass-trapping and positioning, and I didn't recall seeing much on in-room dipole plots. So far, based on a few hours of TrueRTA sweeps, the best positions for my dual DPL-12 sealed workhorses have been at opposite wall-midpoints as suggested by that Welti/JBL paper. Puts them a little close to the couch for my preferred 100hz crossover, though, so I was hoping a dipole "mid-woofer" could work up front/center down to 40hz or so than roll in my IB or other sealed below. I have enough scrap, so I'll throw together a small H-frame and see what happens with a few DPL-12's.