Ripole or other application?

[bluejay]

This speaker seems affordable to me. Can anyone comment on its suitability as an N dipole or opposing W ripole subwoofer? Maybe Moray?

http://www.audiopile.net/products/Sp...1_cutsheet.asp

If not, how about a ported cabinet. I want to build a sub for our home theater. Room dimensions 13'6" x 16'.

[J.R.Freeman]

Nice looking driver - looks kind of like an older JBL.

I know little about the configurations which you mentioned (I'll be watching this thread to hopefully learn more), but as for this driver's suitability as a home audio subwoofer, it poses a few design challenges as I see it.

The specs look to be more of a pro-sound driver. Fs is not that low at 35 Hz, which means low end extension might suffer a little. A ported enclosure tuned lower may get you passed this some what, but I'm not sure how much lower than Fs you can tune Fb. That would be a question for someone else! :P Here I'll make it bold so another can jump in with experience.

Xmax is limited, but sensitivity is very high. That is really nice. Even with small excursions, an 18" driver should displace a nice amount of air for a living room. However, one way around the limited Xmax would be to use multiple drivers. And with that sensitivity you might not need a million watts of amplifier. You'd probably want a good 500 watts rms per driver, I would guess.

If you look at Qts, it is a reasonably damped driver at 0.40. With such a high Qms it looks like most of the damping comes from the electrical component. So to me that sounds like a really strong motor, with a relatively light cone, and a rather compliant suspension. That would explain the high sensitivity. It should be a nice, clean driver. It would be interesting to see distortion measurements but I suspect this driver should be well behaved and controlled.

If you feel like playing around, and you have some test gear, you could try adding mass under the dust cap, close the coil. Of course, you risk wrecking your driver. See what a change a single gram affects. Then extrapolate to your target Fs and see if it sounds reasonable. If you were able to modify two of these drivers for an Fs in the mid-20's, and then add a high-displacement 18" passive radiator, tuned for the low 20's, I bet you would get some nice extension. For passives I've heard the standard is to choose twice the displacement as your active. But with the limited displacement of these drivers, you would likely get away with 1 passive 18 (as long as it is high excursion).

Jim

[bluejay]

JR, thank you very much for your input. You have detailed the good and bad of that driver, technical things I did not understand when I asked.

After a few days of asking around and thinking about it, it seemed to be a consensus that a pro sound driver is not ideal for home theater subwoofing. I have gone on and found something else. I wanted great performance and affordability, (for me at this time). I have ended up ordering a Mach 5 MJ-18m. It should be pretty decent for what I want.

Re. Ripole design,
I have reconsidered this choice and moved on. I will now be building a ported EBS box of about 11 cu. ft. Kind of tried and true with known results.

Someday I plan to revisit the JBL inspired design. I am pretty sure it would have pounded out some serious bass and I would have liked it. For now I will get into the THX inspired stuff and see what that is all about.