Can I get away with this?

[GregN.]

Well, while my Egnater Tweaker is down, I'm looking into my other amps for upcoming gigs. I have a Marshall 50 watt Plexi reissue (no master volume) that I was wondering if I could use w/ my Tweaker 1-12 cab which has a Celestion G12H30 in it? This, if I use my Weber Mass Lite attenuator? I don't run the Marshall's volume wide open. More like around 1 o 2 o'clock. I usually use a 2-12 cab w/ this setup but this is a really small stage I'll be on. And fwiw, I don't need much volume here. Just enough to hear myself over the drumkit. Thanks for any advice.

Greg

[GregN.]

In case I was unclear, my question is whether I can safely use the 1-12 cab w/o blowing the speaker.

[MWJB]

By rule of thumb, I'd say it is a bad idea.

Even running the Plexi at 1-2 o'clock means that it will still probably make in excess of it's clean rated power.

You might "get away" with it setting the mass for 9bd attenuation, as to how "safe" it will be will depend on how hard you drive the amp, or whether you turn the attenuation down (ideally, you wouldn't). So it's possible, if not sensible. I wouldn't do it.

[printer2]

Sure why not use it. The speaker is rated for 30W and the amp puts out 50W. 3dB down from 50W is 25W. You should be able to control your volume enough if the gig does not ask for a lot.

[MWJB]

A 3db drop from 50W clean is 25W, overdriven the amp may make over 50W, 3db drop is borderline IMHO. If the speaker blows it will take the power tubes with it...

[printer2]

So I guess a 50W speaker would not be good for a 50W amp because the 50W amp can put out more than 50W. I think. So the 30W speaker will not take a 30W amp that is overdriven and puts out more than 30W?

I think what is missing here is the volume control. As long as you use it it really does not mater what the wattage of the speaker is. I was using my Yamaha PA amp 250W amp with home speakers that might take a 20W amp at most. Twenty years latter I am still listening to the same speakers, funny how I have not blown them. The gig is a low volume affair, why would you turn up the amp till it screams?

[MWJB]

"I think what is missing here is the volume control. As long as you use it it really does not mater what the wattage of the speaker is."

The power test for a JTM/5F6A amp describe setting the volume control to 50% rotation for max clean power under test conditions. GregN has already stated that he typically sets his volume control beyond this point. Also, given the variation in pot tapers a volume pot is typically a very bad parameter by which to judge anything.

Rule of thumb with tube amps is to use a speaker that has twice the W rating of the amp. If your home speakers have been regularly disspating more than 20W each, then by definition, they are not 20W speakers.

[GregS]

The power test for a JTM/5F6A amp describe setting the volume control to 50% rotation for max clean power under test conditions. GregN has already stated that he typically sets his volume control beyond this point.

I think what was confusing was the 1 to 2 O'Clock. I initially read that as 1 to 2 meaning 1 to 2 on a scale of 10 which probably wouldn't be too bad. However, past 50% rotation I would expect the amp to at least be at the point of clipping (full power).

Even if the intention is to have the volume way down there are still hazards: forgetting to turn the volume down before turning on and playing, a very large signal input to the amp caused by the power to a pedal being turned on.

[J M Fahey]

We are comparing apples to oranges here.
In a Home environment using a 2KW amp with 20W RMS speakers is possible , because even 5W RMS is LOUD and the extra power *available* (which does not mean *used*) provides transparent headroom and sound cleanliness.
The "Power Limiter" is your Spouse or Neighbours' tolerance.
And you listen to your music clean.
Even if Punk or Heavy Metal, the guitars will be distorted, but voice, drums,the whole mix will not.
Playing Rock Guitar, specially with a Tube amp *invites* you to overdrive the amp, simply because it sounds *good*.
Creamier sound, more sustain, bite, presence, you name it.
Besides that, rather than on your Living Room you probably are playing in a Rehearsal Studio (if not Live) or at least in the garage or basement.
The instant a Drummer starts doing his thing, your ears are not "regulated" anymore to a 60/65dB background noise level (the usual home/office level) but 90 to 100dB, depending on your distance to said drums.
Unconsciously youŽll try to match him.
Poof !!!! goes the speaker.

[printer2]

I also took the 1 or 2 as the number on the knob as where the amp is usually played, different story at one or two o'clock. That being said the gig was suppose to be a low volume affair. Do you guys not know how to use your volume control? I have worked with musicians that did not automatically crank their amp in a coffee shop. Not sure how they managed that since the amp would sound so much sweeter there. Different breed back then I guess.

[GregN.]

Well, thanks for the input guys. I ended up not using it. I didn't want to take the chance of having a speaker blow in the middle of the gig. In regards to the volume, on a non master volume (i.e. no preamp gain knob), I like to push it to the point of the sound having a hair on it. I hit the guitar hard and I get a crunch tone, I back off and it cleans up. That's why I run that amp up around 1 or 2 o'clock ( or 6 or 7 in volume increments for those of you that were confused). That IS quite loud and more volume than I need. Thus, the attenuator. Anyway, I really thank you for the advice. I don't think I'll take the chance in the future. : )

GregN