Effective path difference dipole question

[Mazeroth]

When calculating the effective path difference for a dipole do you take into account the distance from the center of the woofer front to the center of the woofer back, or do you measure from the edge of the woofer? Logically I would think it would be the center but I want to make sure before I finalize my dipole plans and make them bigger than I need to.

Also, seeing how the Orions have a woofer facing front and a woofer facing back, is this to guarantee the cancellations for the woofers are identical? Asthetically, I would rather have them both facing the front and flush with the front baffle. Any negative effects with this?

Thanks!

[JonMarsh]

I usually do it center to center.

For the Orions, the facing in opposite directions is for cancellation of even order distortion, which is high in many drivers. In others, like some Accuton and Aurasound models with very symmetric motors, this doesn't buy you anything.

[Mazeroth]

Thanks for the input, Jon.

My dipoles will be using dual Dayton RS315HF woofers and I would like to have them both flush with the front baffle, facing toward the listening position. Do you feel the Dayton RS315HF has a "symmetrical enough" motor to constitute this alignment? Also, with this kind of alignment couldn't one take the subs up higher in frequency, due to not being recessed back in the baffle? I forget what terminology Linkwitz used on his site for this, but so bear with me :P

[Davey]

When you "shift" the woofers to flush mount on the front panel you're taking away any symmetry the system might have had. You're creating a "U"-frame baffle vice a more traditional "H"-frame baffle. The polar pattern will begin to look cardioid vice the "typical" dipole pattern. Both woofers mounted in the same direction will accentuate this asymmetry even further. However, there are conflicting views on whether these trade-offs are worth it or not.

http://www.linkwitzlab.com/frontiers.htm#L

http://www.musicanddesign.com/u_frame.html

Cheers,

Davey.

[joecarrow]

I believe he called it a "cavity resonance", and it is caused by the enclosed mass of air between the driver and the front and back of the "H" made by the baffle.

I would expect your woofers to be able to go higher if your baffle is wider and shallower- not like a big canyon behind the woofer.