I need help with Speaker Theory!

[stien]

Currently I'm running a 1965 Bandmaster into an Avatar 2x12 with a V30 and a G12H. With my tele, it breaks up wayyy late. I know the speaker sensitivity of the V30 is 100 dB and the G12H is around 99 dB, would less sensitive speakers allow more noticeable breakup than before at the same volumes? I was thinking maybe greenbacks (96 dB sens.), but they are 20 watts right? My Bandmaster is 40, is it alright to have those two ratings match as long as I don't run it on 10 all day? I do occasionally bring it to 10 and bring the rawk.

I know that 3 dB change = 2x or 1/2x change in volume, but does that work with speakers? So basically I could get some real nice early break up out of my amp if I got greenbacks or similar.

[TheOtherDave]

I know that 3 dB change = 2x or 1/2x change in volume, but does that work with speakers? So basically I could get some real nice early break up out of my amp if I got greenbacks or similar.

3dB corresponds to double/half voltage (I think it's voltage... might be something else), but perceived volume doubles every 10dB.

[jhuse]

Ok, I'm certainly not a speaker expert, but, a less efficient speaker (i.e. lower sensitivity) will produce less preceived volume per watt of power, so, theorhetically you should be able to drive the amp harder for the same amount of volume. That said, if I don't think sensitivity is the deciding factor for speaker breakup - I could be wrong, though. (Note, I'm assuming the break-up to which you're referring is speaker break up, and not power amp break up; the speakers have nothing to do with the latter.)

You're a bit off with the dB metric: doubling the wattage of the amp is roughly an increase of 3 dB, all else equal. To the best of my knowledge, this does not really amply to speakers.

The G12M's rating of 20 Watts is not the same as an amp's power output; it's more of the amount of "abuse" the speaker can take for sustain lengths of time. Since your Bandmaster rolls at 40 watts, if you outfit your cab with 2 Greenbacks, the speakers should hold up just fine.

Hope this helps. It's possible I got something wrong here, but if so, hopefully someone will be to correct or add-on to it.

[riff1006]

Ok, I'm certainly not a speaker expert, but, a less efficient speaker (i.e. lower sensitivity) will produce less preceived volume per watt of power, so, theorhetically you should be able to drive the amp harder for the same amount of volume. That said, if I don't think sensitivity is the deciding factor for speaker breakup - I could be wrong, though. (Note, I'm assuming the break-up to which you're referring is speaker break up, and not power amp break up; the speakers have nothing to do with the latter.)

You're a bit off with the dB metric: doubling the wattage of the amp is roughly an increase of 3 dB, all else equal. To the best of my knowledge, this does not really amply to speakers.

The G12M's rating of 20 Watts is not the same as an amp's power output; it's more of the amount of "abuse" the speaker can take for sustain lengths of time. Since your Bandmaster rolls at 40 watts, if you outfit your cab with 2 Greenbacks, the speakers should hold up just fine.

Hope this helps. It's possible I got something wrong here, but if so, hopefully someone will be to correct or add-on to it.

I am thinking that an amps power rating is based on power at maximum clean. That would mean it really does more than 40 watts a breakup and beyond. Generally they recommend you double your speaker wattage, i.e. 80 watts of speaker power for a 40 watt amp. Can anybody confirm that?

[Franktone]

At one time I had a 1978 Marshall 50 2x12 combo which came used with a 25W celestion and a 30W celestion. Typically at the time with the band, the amp was run by myself full up most of the time with both Gibsons and Fender, and couldn't blow the speakers, no matter how hard I tried.
The Celestion web site quotes the Greenbacks as 25W each. If that's the speaker you want, they should be OK, because it seems that you are not going to be as rough on them. But of course, it is assumed that they make em like they used to.

[walterw]

speaker sensitivity will indeed make a big difference in how much you can crank the amp. those greenbacks would likely sound good for that application.

[stien]

Well I read somewhere you're supposed to have 1.5x the wattage handling in speakers, which Greenbacks are not. I doubt that I would blow them as I don't crank it all day every day. I can't get it past 4 with my drummer though, which really irks me. I want some drive.

WGS sells some cheap greenback copies, might look into it.

I was referring to getting more amp OD since I could turn it up more and have less volume because of less sensitive speakers.

I could also just suck it up and buy an overdrive pedal :D

[jhuse]

I am thinking that an amps power rating is based on power at maximum clean. That would mean it really does more than 40 watts a breakup and beyond. Generally they recommend you double your speaker wattage, i.e. 80 watts of speaker power for a 40 watt amp. Can anybody confirm that?

You're correct that the 40w rating is supposedly "clean power." From what I understand, a fully driven amp can throw about 1.5x "clean power" rating, so in this case ~60w. That said, I believe speaker power handling ratings are done in a similar manner, that is the speaker can exceed the published rating. So, you should be OK matching 1:1 the speakers with the amp.

As an example, think of the AC15 with 1 15w Celestion Blue, or the AC30 with 2 15w Blues.

Now, all of that said, I prefer a high speaker rating to amp output. According to Weber's website, all else equal, the higher the speaker rating-to-amp output ratio, the warmer and bassier the tone; the lower the ratio the brighter and more aggressive. Obviously, just rules of thumb, but this has helped my approach in refitting cabinets.