Magnetar thinks it sounded bad on dipole and sent it back.

Thought of crossing it @ 300hz@24db (for under 300hz).

I don't know transient response of dipole, but I would think it would be lousy due to high qts as not much qms to control driver (down low on this baffle)

perhaps the ringing @2500 can be fixed also.........

Any experience ??????????

Personally, I think Alpha 15's have a nostalgic sound, probably due to their their relatively small magnet and their cone shape. Reminds me of what was in console stereos in the fifties. Also, they aren't electrically damped as much as most drivers, and so they are ideal for sound systems that can't provide much electrical damping - such as low power tube amps. They already have very high Qes, so low damping factors are pretty much "water under the bridge."

All-in-all, they're an interesting part and very popular for Eminence. The most popular 15" woofer here is probably the Delta 15, but the nostalgic sound of the Alpha 15 makes them pretty popular too. Just be sure that you use a Zobel with them and don't run them "wide open." For subwoofer use, crossover below 200Hz; As a midwoofer, don't go above 1.6kHz. And when used as a midwoofer, the Zobel becomes extremely important. This is the configuration for the Thermionic Series four and seven π speakers, which when combined with a nice tube amp, will take you right back to the 1950's, just like "American Graffiti."

Do you leave that spike in there ????????

Your concerns about driver QTS in dipole applications are understandable, but unnecessary. Anything with a qts below .8 (in some cases even 1) is considered qutie reasonable in closed box/dipole design. These drivers are not ideal for use in ported enclosures, but do fine in infinite baffle or dipole subwoofer configurations.

After all is said and done, qts has little to do with the sound quality of a driver (to a certain extent).

Having said htat, I don't feel the Alpha is a good option. It's unusual set of characteristics may give it a sweet sound for vocals and midrange, but it doesn't have the stuff to be a subwoofer. It also has very little xmax which is bad for a dipole setup, particularly if you are introducting low frequency EQ (which is generally what is done).

Possibly check out thise driver.
http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=12695537&St=2137&St2=-81964001&St3=69117267&DS_ID=3&Product_ID=118185&DID=7

Adam

One thing you'll notice about the Alpha 15 is that all sealed and vented alignments for cabinets smaller a house generate some peaking. It is within +/-3dB when the cabinet is larger than 10ft3, and if it is tuned very low or sealed. I know the rule of thumb about high Q speakers in sealed cabinets, and 0.7 to 1.0 are a good range for them.

But I'd rather run this one ported, and tuned very low, to like 15Hz - and let me tell you why. Take a sealed 12ft3 box and one the same size, ported for tuning at 15Hz. That's what the Thermionic four π and seven π cabinets are, by the way. The sealed cabinet has f3 of 40Hz, f10 of 30Hz, and output falls below that as you might expect. There is a 3dB peak between 50Hz and 100Hz, a direct result of the high Q of the driver.

Now take the same size cabinet, and port tune it to 15Hz. You have almost the exact same curve down to 40Hz, so the ported cabinet hasn't increased the amount of peaking between 50Hz and 100Hz by an appreciable amount. But below 40Hz, you have a lot more energy because of the port. Both f3 and f10 are shifted lower in frequency, and you have usable output down nearly to 10Hz. At 15Hz, output is down 12dB. There is a sort of -10dB shelf in the 10Hz to 30Hz range which then rises to 40Hz f3.

This is absolutely subterranean response for these low power tube guys. That's why I've suggested it as an inexpensive solution for SET owners. It is a viable subwoofer option for them, and one that is actually perfectly suited for low damping factor amps. With Q this high, the additional series resistance from the amplifier is only adding more of what is already largely there. And in a very large box tuned down deep, you can literally get bass response in the teens from a 2 watt SET amp. I don't know of many other solutions that will do this, and certainly none for such low cost.

Adam