Random thought on dipole bass

[JoshK]

So I was thinking (danger will robinson!) about dipole bass, inspired by a though to consider what to do with my 3rd 15" Lambda driver (4th got severly damaged by FedEx). I had also been musing over the trinaural concept trying to see how to sketch out the revectorization. Then I had this thought.

Suppose we have some 15" (or 18" or multiple 12" drivers) that we want to use for dipoles woofers (say 50-200hz). Lets also suppose we are going to be driving them with their own amps. It struck me that a lot of this content in this region is quite likely to have significant overlap from the L&R channels (or am I mistaken?). One could conceivably create a center channel woofer created from the intersection of the L&R channels, low passed in such a way, to help with the 6db/oct dipole rolloff, much like a .5 woofer helps with BSC.

For simplicity sake, we could use opamps, at least initially. I haven't figured out exactly how to create the intersection using subtractive and summing circuits, but I can't imagine it is that difficult. Is this a preposterous idea, or could it be a good use of a 3rd woofer? Amp channels I have an abundance of and building an analog xo like processor is within my reach.

Comments/musings welcome.

[JoshK]

Follow up to my own post....

I realize that this is largely predicated on the thought that most of the left only and right only content will be above the rolloff and not much below or there will be a flaw in lifting only the intersection with a center 'helper' woofer. I guess I would need to study if this is realistic or not. This is why I am asking you all.

Or...or a more complicated processor could be constructed where the left only and right only content is EQ'd for dipole rolloff and not the content contained in the intersection going to each of the l&r channels. That seems much more difficult to achieve, but it does seem possible.

[cjd]

~200Hz is the bottom of a violin... not all that low. Very localisable content and definitely not always centered... there're 3 strnged instruments that go lower.

[Paul H]

~200Hz is the bottom of a violin... not all that low. Very localisable content and definitely not always centered... there're 3 strnged instruments that go lower.

Guitar, cello, piano - there must be more ...

[Mazeroth]

Guitar, cello, piano - there must be more ...

Viola and a double bass.

[cjd]

yeah, I was thinking simply within the "viol" family, so violin, viola, violin-cello, and bass-viol. Having played for so many years, it's a very direct comparison to frequency for me.

C

[Rudolf]

I just have finished two new 15" H-dipole woofers which are crossed in at 200 Hz to some fullrange drivers. Since the old dipole woofers are still mechanically connected to the FR baffle, I had to place the new ones just left and right from the center position for a first listening.

What did I find:
The lowest room mode is definitely more enhanced than with the old dipoles which radiate from normal stereo positions diagonally (?) across the room.

When listening to the dipole woofers without the FR drivers, "left" and "right" information from the woofers can be easily distinguished. But as soon as the FRs come in, all stereo information is pulled to them. As long as you don´t listen to pure 200 Hz sinus test tones but to real music, directional information at higher frequencies will surely dominate the perceived instrument locations.

[JoshK]

So, I think we concluded the complicated processor would likely be needed. That is what I feared/expected. I am not sure its worth the effort, but it was a random thought.

So what to do with the 3rd woofer? Maybe a big ass center!

[cjd]

punch bowl!

[Paul W]

Just 'cause it is really easy to try...

If you want left only and right only, connect the third woofer (and maybe a series inductor and/or resistor) between the positive amp leads of the main L & R woofers. Mono will be a "zero" signal at the third woofer, left or right only will provide a difference signal to the third woofer.

Assumptions are active XO and high-current amps...no whimpy stuff.