Estimating Speaker Ratings

[Chappy]

Can alnico speaker ratings be determined by the dimensions of the magnet and endcover?

Here are the details:

I gutted a Conn 710 organ. The speaker cabinet had 2 x 10" and 2 x 15". All speakers were wired in parallel with 2 x 4uf caps acting as a crossover filter for the 10" speakers. The output amp has 4 x 6L6G in a cathode biased config. The service manual calls it a 40W amplifier. Unfortunately the manual has no info on the speakers.

One 10" speakers has the code K56744
The other has 232823, 791701, 583949

magnet is 1 3/8" in diameter and 1" high. The metal surrounding the magnet is 2 3/4" square.

I've hunted long and hard on the net and I have determined that the speakers are Magnavox, but I can't find any details on their ratings.

They are the same as these ones on the bay.

http://cgi.ebay.com/Pair-1956-Vintage-M ... 286.c0.m14


So can the power rating of these speakers be determined by comparing the size of the magnet and cover to that of a known speaker? Say a Jensen P10R?

Chappy

[billyz]

I don't know the exact wattage rating of your speaker, but it is probably around 10W. The old Jensens were rated lower than the modern Jensen replacements. It has to do with the adhesives and voicecoils used. The old ones were mostly paper voicecoils which do not disapate the heat as well. And the modern adhesives hold better than the old types.

In your organ the 15" were more powerful and took the bulk of the load. The crossover directed the lower energy highs to the tens. Your speakers would be nice in Champ or Tweed Princeton, Tweed Vibrolux. A pair would probably go good in a Tweed Deluxe,or Blackface Princeton reverb, if you like the speaker breakup. I doubt a pair could handle more than the output of a pair of 6v6's or 6bq5's.

[Chappy]

BillyZ

Thanks for the reply. Based on the tubes I pulled I suspect this organ was made in late 59 or 60. I'm guessing the speaker with the manufacturer code 232823 was made in the 23s week of 1958.

I was hoping to use these in a future low power tweed super build with a pair of 5881's cathode biased. If you are correct about the 10W rating then I guess I'm out of luck.

Thanks
Chappy

[jaysg]

I would say no, unless you're very conservative. The rating is all about the size of wire, turns, and heat dissipation.

[billyz]

Chappy,
The 10 watt I suggested is really a guess. The might very well work in a cathode biased tweed super. But I would bet they would not be the best choice. Try them and see.

[Bob-I]

Another concern for older speakers is that the glue holding the voice coil together may have dried out lowering it's ability to handle heat. I've opened up a few older stereo speakers to find winding hanging off the coil and the glue flaking off. I'm not an expert but I'd guess it's some type of hyde glue or varnish. Some of these speakers can still sound really good but I'd be careful about driving them hard. JMO

[Chappy]

Thanks for the info fellas. I''ll give them a try in my 18W clone and see how they hold up. I'll probably just go ahead and buy a few reissue P10R's so I can get an idea of what original Alnico guitar speakers are supposed to sound like. After that I can decide if the Magnavox speakers are of any use in a guitar amp.

Chappy