Drivers, Drivers, Drivers

Bob Brines

2003-01-31 10:11 pm
I had an opportunity to compare a few drivers. I had to tear down my electronics to take to the Dallas LSAF show, so I had to rebuild when I got home. That gave me the opportunity to swap out some speakers.

Alpair A7P, A10P, A12P: It finally dawned on me why these drivers are generally preferred to the metal equivalents. All of these drivers have a huge 2nd order harmonic distortion centered on 600Hz. This is the tube sound -- 2nd order distortion. Makes for a sweet sound, but very annoying acoustic instruments.

Alpair A7.3, A10.3: My favorite metal drivers in that order. A7.3 needs to be used as a sat/sub. I'm not a bass head, but I like clean, undistorted bass to at least the low 30's. No 4-5" driver is going to get into the 30's without a boatload of distortion. The A10.3 in a MLTL works pretty well, but not to the absolute bottom. At low volume ([email protected]') sounds great. Much louder, or at HT mains, it needs help. I cross it to a sub @150Hz. With the bottom removed the A10.3 can go loud and clean.

Fostex FF165WK: What a disappointment! I had remembered this driver as being nice and well balanced. I have them in BR's that had been sitting in a corner untouched for a couple of years. I drug them out and ran a sweep. I EQ'd out that nasty spike at 7kHz and gave them a listen. No top, no bottom. Slightly bloated in the midrange. Devoid of any depth or detail. The last time I had any Fostex speakers out were FF225WK's with tweeters. I don't have those speakers any more, but I remember them as being much better than that.

Alpair P7.1: I bought a pair of these when Madisound first got them. They had been living in the test mules for the current iteration of my TL for the A7.3's. I cleaned up the cabinets and wrapped them in some babinga I had laying around. Gorgeous little speakers. Anyway, the P7's are not A7's! The P7 is more honest than the A7, but lacks the detail and precision of the A7. Well worth the price, though. I would like to see Mark put the A7 guts in the P7 frame.

Scan-Speak 10F/8424: Ah, yes! This driver is as well behaved as the spec sheet indicates. No bad habits, no coloration. Leave the gently rising response alone -- That gives the right balance when the speakers are squared with the walls in an equilateral triangle with the listening chair. However, this is not a full-range driver. It is a mid-tweet. If you use it below 300Hz or so, you will be wasting its good qualities for distorted bass and high IM distortion. I crossed it to a carbon fiber 8" woofer at 300Hz and the integration was seamless.



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Bob Brines

2003-01-31 10:11 pm
I appreciate and respect your evaluations but could you please explain what you mean by "The P7 is more honest than the A7"?
The P7 has an overall flatter response than the A7.3. Of course if you are willing to use DSP, it is trivial to get the A7.3 dead flat. You get what you pay for.

Also, would you say that for mid-tweet application that the 10f is your favorite among these drivers? Thanks!

There are a lot of choices out there that I have not tried. However, the 10F is a seamless match fro the Audax HM210C0.

-----Fostex FF165WK: What a disappointment! --------

Oh Bob, I've convinced myself that my FF165WK MLTLs are satisfactory. Now they're going to sound lifeless and shallow. Don't say anything, it's too late, the seed is planted and sprouting:p.

I've been really intrigued by FAST speakers. Thanks for the rationale.

Cheers, Mack
Ah, I wondered what had happened to the old Lyeco units. Good to know they're still around. They never did get much traction -IIRC the 8in was the most interesting of the bunch. Dave & I won a pair of these 4in models about 10 years back. I never did hear them as they were stolen in transit to me along with a bunch of other drivers & turned up on eBay a month later. Dave wasn't overly impressed by this particular unit at the time, although the larger ones apparently fared better.
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I have an Alpair 7 Moap version in bass reflex box. I got it from a guy who brought it directly from Markaudio.
Does it take forever to burn in as currently the balance is a bit tilted to the treble side.

I don't think burning or breaking in is going to improve the bass treble balance enough. Maybe try a baffle step compensation? I don't know if any bass reflex speaker on a narrow baffle that doesn't need it. Probably 1mH and 5R is a good place to start. Add or reduce R to taste.

Bob Brines

2003-01-31 10:11 pm
Bob, did you get a chance to revisit the MA12P design?


No I have not. I was sufficiently disappointed with the A12P when compared to the A10P and especially the A10M that this is well down the list of things to do. The Audax/SS FAST is number 1, then I want to look into the TB W8-2145 and possibly redo the W8-1772. The 1772 is my best seller for plans.