Speaker Power Rating

[Gordon Bellerose]

I own an old Music Man amp with a ton of power. 130 watts.

If I was to replace the two speakers, what kind of power handling capabilities would the replacements need to be?
As with most things technical, I come to this forum to get real answers.

[Peter Wilcox]

First need to know the impedance of the speakers that are now handling the 130 watts. And what kind of watts are those 130 - RMS, peak or "music power."

The model # of the amp would be helpful, or a link to the owner manual.

[Mark Swanson]

Music Man did not make that many different models of amps, and if you have a 130 watt model, it's probably the Twin Reverb clone they made, with 4 6L6 output tubes and two 12" speakers. I can't be sure until you tell us more about the amp but if that is true, any set of speakers that would work in a Twin would work in your amp.

[David King]

I'd suggest going with the driver that sounds the best and not worrying too much about power ratings. You aren't likely to drive it that hard anyway. If you want bulletproof then all bets are off and it will probably sound like a wet blanket.

You might want to read through this fellow's opinion on the subject: http://fenderguru.com/amps/twin-reverb
He makes it clear that the Twin is design to play really loud and clean. If you need some driver breakup at moderate volume you'll probably want to choose a different driver than stock Jensen C12n.

[Gordon Bellerose]

I guess I should rephrase my question.

The Music Man amp is a:
210 HD-130
It has 2 - 10 inch speakers, and has 130 watts, R.M.S.
It also has a switch to go either 4 or 8 ohm. There is also a 1/4 inch out, for an extension cabinet.

The speakers are original, and are in pretty good shape.

I am wanting to build an extension cabinet with 2 - 12 inch speakers.
I'm not sure if I would go straight into the extension cab, bypassing the regular speakers, or go tandem.

So at peak power, would the power be equally divided between all 4 speakers, or both if I only use 2?
And if so, would the speakers have to handle 35 watts each? Or if only two are used, 65 watts each?

[David King]

Again I would say don't get too hung up on speaker ratings as unfortunately they don't mean very much. You can burn up a 100W voice coil with a 15W amp if you send just the wrong signal through it. Focus on what you want to hear. Do you need more volume? More cone breakup at a lower volume? More overdriven output section at lower volume? A darker sound to fill in the mids on a thin strat or a brighter sound to overcome the mids on an overwound neck humbucker?
My distant recollection of that amp is that it's an earbleeder. It's one of several on my blacklist of guitar amps I will never try to compete against as a bass player.

[Peter Wilcox]

Gordon - it looks like you can use any speaker rated at 35 watts or above. The speaker jacks are wired in series, so if the main speakers have a total impedance of 4 ohms (two 8 ohm speakers in parallel) and you add a cabinet with two 8 ohms in parallel (another 4 ohms), you will have 8 ohms total impedance. From a schematic (I don't know if it's the correct one) https://docs.google.com/viewer?url=http ... 00-130.pdf the impedance switch is connected to the center tap of the output transformer for a 4 ohm load (and I presume 65 watts), and across the whole secondary for 8 ohms, I presume for the whole 130 watts. So if the switch is set correctly for the speaker load, each speaker should only have to handle 35 watts. Also, I don't know if the amp could tolerate max power across 4 ohms on the 8 ohm setting - I would make sure this is set correctly.

You might want to use higher rated speakers, such as these http://wgs4.com/g12c as a fudge factor, and also in case you might want to use the cabinet in the future with a higher rated amp. The relative perceived volume of the different speakers will depend on their sensitivity (SPL rating) - the higher the louder.

I am no expert, so if anyone has any additions or corrections to this, please advise.

[Gordon Bellerose]

Thanks for the replies guys.
Peter. I learned that I should be operating the amp on the 4 ohm setting when using only the two speakers in the amp.
If I build the extension cab, I will make sure to wire correctly.