Phase Linear Andromeda Bob Carver Speakers & Subwoofer

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... ORS%3A1123

I am watching these puppies.I will be more than willing to take a road trip for these. Stop by and visit Toy Maker.

They look really interesting. A PCB crossover! Hardly ever see that.

[DaveS]

Today I talked to the guythat sold them this weekend. I gues the new owner is out to make some money. I was going to buy them and match the sub section up with a pair of the pannels that I found up here in NY that are all refoamed and in excellent condition but if you notice ther is no mention of the sub modual, because he hasn`t got it.

The Craig`s List ad and and the e-bay are very close, so it`s the same guy or someone out to make a buck.

Vintage pair of Phase Linear Andromeda speakers with subwoofer - designed by Bob Carver. You get 2 large 24" x 63" x 5" speaker panels and a subwoofer module. The speaker panels each hold two 8" midbass drivers, two 4" midrange drivers four 2" cone tweeters and a 1" soft dome tweeter. The subwoofer module has two floor-facing 12" bass drivers. The frequency response was 24Hz to 20KHz. They play and sound pretty good but do need some work - mids have some foam that needs to be replaced, there are some cracks on the plastic baffles above the tweeters, and grills have been attacked by a herd of cats! Otherwise they need a good dusting. Power rating was listed at 350 watts RMS. $325.00 OBO Obviously, local pickup only - these things are huge!

The antithesis of the "KISS" principle. Pass....

That sheds a whole new light on the subject.

They may have been good back in the day, but if they were THAT GREAT... Carver would have make something close no ??

Notice all of those large power resistors on the x-over board? yuck!

But Ed, you need resistors in combination with inductors and capacitors to make bandpass filters.

But that many!? Can also do a filter with just a cap plus the "natural" inductance and resistance of the driver coils! I know; I copied this from EPI's for my AOS's! No "parasitical" resistors needed.

It is doable if the drivers provide enough resistance, and you are satisfied with the rolloff points they dictate. It looks to me that the crossover has only two resistors. The stacking is to make one resistor out of a few in parallel to get the right resistance, I would think.

I don't know why you are so against resistors. At least their impedance is constant and they don't throw phase shift into the pot.

I thought it was interesting to note that...

- the 4 drivers, that at first look like little horns or baby butt cheeks, are actually up firing open drivers that fire into a little cone that would throw an equal omni field!

- the speaker design is an open baffle!

- the center pair of small drivers with rear cups, one fires forward and one back.

So the system is very much pointed towards the open baffle, dipolar kind of design. This with the special eq module which sounds like it has some kind of version of the sonic holography. The whole system is likely to be a bit inefficient and need some power. Enough cone area to probably do at least ok or better for dynamics.

In a lot of ways, certainly some relationship in the design to the ribbon series. Much like them, point angle and distance would be critical to get the best stage, space behind a good thing, not too fussy about side walls and a really open spacious soundstage! Boy, they'd be fun to hear!!

Mark

Kind of makes a mockery ("parasitical" x-over resistors) of folks who spend a fortune for "garden hose" size speaker cables (partly) to minimize resistance losses/effects, only to have hulking big power resistors in the speaker ITSELF 100's of times the resistance of their wires; that's all! And in Rich's posted article on bi-amping, the author of that article points this out as (another) benefit of bi-amping!

as to "At least their impedance is constant and they don't throw phase shift into the pot":

The Crossover
One of the more complex problems in designing an accurate sound reproducer is that of matching woofer and tweeter performance. This is normally done with the assistance of an electrical crossover, which presumably properly divides, attenuates and apportions the electrical energy from the amplifier into the respective woofer and tweeter. The important considerations are that the slope of the frequency response at the crossover frequency be very steep and exactly reciprocal so that both woofer and tweeter are producing power at half the normal rate at the crossover point. When they are added together, flat frequency response is then maintained. These objectives are achieved in the EPI basic module by a combination of mechanical and acoustic principles.

Putting it another way, the woofer stops working at the same point where the tweeter starts - all by itself, without any help from external electronic elements. Since woofer and tweeter are perfectly matched in efficiency, all that is needed in the way of electrical crossover elements is a small capacitor. This is certainly the most economical solution (some crossover networks run as high as $50 - '74 $'s-Ed), but it is also the one which produces the best performance - by eliminating phase shift problems around the crossover frequency caused by complex inductive and capacitive networks.


(from circa 1974 EPI brochure; probably penned by a "young" Winslow Burhoe!)

I'm certainly not in any sense defending passive crossovers as the end-all to music reproduction. Indeed, I believe active crossovers are a better choice. However, that said, there are some things that young Winslow Burhoe failed to mention about running speakers out to their limits — namely nonlinearity. Normally, you want to take the section of the speakers performance curve where it is the flattest, and truncate the parts near their resonant frequency and their naturally occurring breakup. With one capacitor, you can, using the inductance and inherent resistance of one of the voice coils, create an RLC circuit using that one capacitor that will attenuate frequencies below a certain point. With only one capacitor, I don't know how you keep the speakers in phase, unless he means "one capacitor per speaker set". Before I changed the crossover in my Minimus 7's, it was essentially a capacitor and inductor on the tweeter.

You lost me on a couple of points there BillD:

1. "..about running speakers out to their limits — namely nonlinearity."
Where did he say anything about "running speakers out to their limits"? You don't need to driver a speaker into non-linear range to get it to "naturally" roll off in response (and this roll off occurs at ALL power levels; it is due to the mechanical/acoustic properties of the driver - basically - just being "too massive", etc. to respond to FF frequencies above the x-over freq (1800 Hz in the case of EPI woofers). EPI speakers, if known for anything , were/are known for their extreme linearity (which to some is not always desireable mainly because they not used to such linearity!).

2. "With only one capacitor, I don't know how you keep the speakers in phase, unless he means "one capacitor per speaker set".
Are you referring to the phasing of the tweeter vs woofer @ x-over point? Beyond this (and even @ 1800 Hz!), it matters (IMO) very littlle. And is in fact meaningless to talk about the "phasing" of say a 5000 Hz tweeter signal relative to a 1000 Hz woofer signal. Minute changes in listener location will change "phasing" of the various frequencies relative to the HF's all day! And he means one cap (10 uf high voltage NP re EPI "basic module" models) per speaker enclosure (to filter/protect the tweeters from freq's below 1800 Hz).