Were they given to you by Satan?
I have used a pair of second-generation Pentagram P10's as my main speakers for the past 26 years. They are excellent all-around performers, with no major weaknesses. They cost $1800 in 1983, iirc.
If the woofers on your speakers are truly 8 inches, they may be a smaller model which I believe they also produced, called the P8. My P10's have a 10 inch woofer, a 4 inch or so dome mid-range, and a one-inch or so ribbon tweeter (it was claimed to be a ribbon, but I don't recall if it really was one, the alternative possibility being an etched voicecoil leaf tweeter). It also has a 15 inch mechanically tuned passive radiator on the bottom. "Mechanically tuned" means in this case a large rubber band-like thing attached between the center of the cone and a wooden cross-member within the speaker, which holds the cone under a certain amount of tension.
There was an early version and a late version of the P10. They can be distinguished by the fact that the early version had a smaller dome mid-range (around 2 inches, instead of 4), and a mica top. My later version has the 4 inch or so mid-range, and a painted wood top.
Mine is finished in a beautiful light oak veneer.
Specs are as follows:
Power handling 35W minimum, 200W continuous
Sensitivity 90db (1W, 1meter)
Frequency response 24 to 20000 Hz +/- 2db
Impedance 7.2 ohms nominal, 5.7 ohms min
The truncated pyramid design serves two purposes: It time-aligns the drivers with each other, and results in there being no parallel surfaces internally, which eliminates the need for internal damping.
They are a fairly easy speaker to drive, and I've had excellent results with both tube and solid state amplifiers. Their bass is deep, loud (when it should be), and tight. The rest of the spectrum is very well balanced and integrated. Imaging is very good, especially with tube amps. There are no particular colorations in any part of the spectrum, and I consider their weaknesses to be subtractive, i.e., a lack of the kind of detailing that good planar speakers can provide.
I recently had the surrounds redone on the woofers and passive radiators by Bill LeGall of Millersound.net (not .com), who did a wonderful job. They were not rotted or disintegrated, just torn, I suspect due to a combination of age-related loss of flexibility coupled with being driven hard.
The company only existed for around 3 years or so in the early to mid-1980's. Its president was a youngish fellow named Michael Levy, who was the designer, and the speakers were assembled in the garage or basement of his house in Queens, NYC. The cabinet was custom-made to his specs by an outside cabinet-maker, and the drivers were from well-regarded companies such as Seas.
Hope you can get them restored to good shape -- they are excellent performers, especially if they are P10's in the later version, and I feel that you would have to spend perhaps $5K or more to duplicate their combination of bass performance, dynamic range, and overall balance and accuracy with today's speakers.
Thanks VERY much for the info! I just measured, my woofers are indeed 10" with a 4" midrange. I was able to get one speaker playing today, and I was very impressed by the highs and mids, although the woofers may be a lost cause - the previous owner tried "refoaming" them with, if you can believe it, a strip of foam (like, couch cushion foam) and white caulk, lots of it. But the cabinets seem to have a lot of integrity and I think they could be easily re-veneered. The crossovers are probably the most substantial I've ever seen.
Your post raises a few questions which I hope you don't mind answering: Do your speakers contain any damping material, and if so, what kind and about how much? And, any ideas where on earth could I get a passive radiator that would be a suitable stand-in for the original?
I wonder if this Michael Levy fellow is still around? It'd be interesting to get in touch with him...
Thanks again, and best regards!
The Pentagram's were unusual in that they contained no internal damping material whatsoever. That was made possible by the five-sided truncated pyramid design, which has no parallel surfaces (you'll note that each side is opposite a corner edge).
I'm sure Bill LeGall can effectively repair the damage the other person did to the woofers, for reasonable cost. He is the best in the business at re-coning and repairing surrounds. His phone number and email address can be found at http://www.millersound.net. The main downside would be the time and effort required on your part to remove, pack, and ship the drivers, and reinstall them subsequently.
Before sending him my drivers for repair of the tears I mentioned, I spoke to him at length on the phone (he is a delight to talk to, and very informative), and he actually recalled having listened to the P10's, and commented that they were "very, very musical."
If your passive radiators simply need cone replacement, I'm sure he could do that as well. If they are completely missing for some reason, I have no suggestions to offer other than asking Bill for his advice.
Not sure what became of Michael Levy after his Pentagram days. I haven't seen his name come up ever since in any of the numerous audiophile publications I subscribe to.
Best of luck with them!
Some good additional background and information on the Pentagrams is provided in post no. 49 of this thread.
Among many other things, he notes that the P10's were the reference speakers of a reviewer at "Audio" magazine.
I used to build these for Mr Levy. The P-10 is a 3 1/2 way, incorporating a 15 inch "passive damper" that crossed over mechanically at about 60Hz and was 3db down at 16Hz or so. The woofer was made by Becker. Any 15" (preferably paper) passive can be used to replace the original, but it must have an added 16oz weight hot glued to the center and be suspended from an internal support in the middle of it's linear excursion with 1/4 inch rubber bands, such that it returns to center when flexed. It was attached with t-nuts, so it's easy to remove and install. If you have the original damper you might use the original weight. We used heavy washers and eye bolts. The tweeter is a Panasonic leaf, quite good for it's time. Replacing it will probably require adjustment to the crossover. The speaker sounded best at the time placed 1/3 into the (preferably large) room and driven by high power push-pull amps like the CJ Premier 1 and Quicksilver M190, or really good sand like the Bedini 25/25. Its strengths were great imaging and bass equivalent having two subs. Tonality could be adjusted slightly by toeing them in, but your best bet was to be VERY accurate in placing them, relative to the listening position. In an equilateral triangle with the speakers the base and the listening position the apex, they would disappear.
The cabinets use high quality wood veneers and black Formica tops. Finishes included walnut, light oak, and Brazilian Rosewood, and we made a few with 10 coats of black lacquer painted by a car painter. We had a lot of fun back then, but they were very expensive to make, since Mike used high quality parts, including the best caps and resistors, and parallel leads composed of Kimber Kable and Live Wire, equating to 10ga internal cabling, which required one BIG soldering gun!
That's all folks!