Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: softwarejanitor on November 22, 2010, 07:27:32 pm
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I was planning on using a vintage 1956 Jensen P15R to build a combo with a 20 watt (2x 6V6) Motorola tube amp chassis but I found out that speaker is only rated at 15 watts... Dohh! The original record player console the amp and that speaker came in also had a tweeter, which is probably why Motorola could get away with using that low power handling speaker. That and the fact that stock that amp chassis (HS-475) is totally clean all the way up to max volume. I'm modding it to increase the gain and get some overdrive/distortion as a guitar amp though, so that will no longer be true. A 20 watt guitar signal would probably toast that P15R real quick.
Anyway, instead I will be using a pair of Silvertone labeled Oxford 12" speakers. I think they are model 12J4-2. They should be able to handle the power as I think they can handle 15-20 watts each. Anyone know for sure the rating on these? I can't find anything specific other than that Fender used the 12J series speakers in some of their smaller combos.
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Remember, speaker manufacturers used to rate speakers with two ratings, music power and program
power (or some other such name/nomenclature). I would be willing to bet unless you put a bass
on it, it could take 20W from a guitar for quite a while. I would also bet they called it 15W music
power, 30W program (they do this now in fact).
I would use it first and check it out. If you hear flubbing or pole piece slamming, stop and get another
15". Again, I think it could take it. I have an old ampeg in the shop right now that does 30W with a
"15 Watt" Jensen in it. Been in there for decades.
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Remember, speaker manufacturers used to rate speakers with two ratings, music power and program
power (or some other such name/nomenclature). I would be willing to bet unless you put a bass
on it, it could take 20W from a guitar for quite a while. I would also bet they called it 15W music
power, 30W program (they do this now in fact).
I would use it first and check it out. If you hear flubbing or pole piece slamming, stop and get another
15". Again, I think it could take it. I have an old ampeg in the shop right now that does 30W with a
"15 Watt" Jensen in it. Been in there for decades.
You may be right, but I've already got the pair of Oxford 12" speakers, so I think I'd rather be safe than sorry. I'll probably just build 1 1x15 cabinet for the Jensen and use it with my 5 watt Epiphone Valve Jr. That little amp shouldn't blow it up too easily.
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I have seen vintage speakers just fall apart once the amp is re-built. The ancient adhesives may be long dried up and gone.
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I have seen vintage speakers just fall apart once the amp is re-built. The ancient adhesives may be long dried up and gone.
I think a lot of that may depend on how and where the speaker was stored. Not only do exposure to light and temperature variations probably play a factor, but from what I've seen there is something in cigarette smoke that causes some kinds of adhesives to break down over time.
FWIW though, I've got a number of 1950s and early 1960s speakers I'm using with tube amps that are working great, so far at least.