So the ohms match, how important is it that watts match?

[Steve G]

Hi folks

Ive now accumulated a few cheapo amp heads, Epi VJ and a couple of crate powerblocks.

Ive also made a few cheapo and serviceable cabs. All running 8 ohm speakers. My latest has a celestion tube 10 (rated 40w).

If I run the crate through this thing am I going to destroy it? The crate is 150w but obviously thats dimed, if I keep it at fairly sensible levels will I be OK? I realise theres no guarantees here, but does everyone match their watts from head to cab?

As I play fairly clean surely speaker distortion will kick in and tell me Im in the danger zone, or is a high powered head putting more strain on a speaker even at low levels?

(Can you guess Ive always been a combo guy up to now )

[e-merlin]

Well, you have to remember power rating is before amp distortion. So if it's 150 watts, thats 150 clean watts. I'm not sure how much distortion a solid state amp will give you, but you also have to remember that just because the amp isn't dimed doesn't mean the speaker won't get the amp's full power at times. Most manufacturers pair their amps with a speaker compliment that excedes the power rating of the amp by quite a bit. IIRC, most of 'em will use speakers that can handle double the amp's power.

Anyhow, this is IMO and YMMV.

[blue metalflake]

It would be much safer the other way around. I'm sure you can use it as a bedroom amp with no problems, but I wouldn't like to trying gigging that set up.

[beep.click]

Originally Posted by Steve G

My latest has a celestion tube 10 (rated 40w).

If I run the crate through this thing am I going to destroy it? The crate is 150w but obviously thats dimed, if I keep it at fairly sensible levels will I be OK? I realise theres no guarantees here, but does everyone match their watts from head to cab?

As I play fairly clean surely speaker distortion will kick in and tell me Im in the danger zone, or is a high powered head putting more strain on a speaker even at low levels?

I believe in playing it safe, and having the speaker watt rating at LEAST match the amp watt rating -- I feel safer having the speaker rating HIGHER than the amp.

That being said, I have run various amps, including the PowerBlock, through underrated speakers... or speakers where I just don't know the rating. I never do it for very long, and always at very, very low volumes; like 1 or 2 on the amp volume.

I don't know whether you'll get a warning or not. I always ask myself, "What will it take to fix or replace what I blow up?" That keeps me cautious!

[tele12]

Originally Posted by e-merlin

Well, you have to remember power rating is before amp distortion. So if it's 150 watts, thats 150 clean watts. ....

Actually the Crate PowerBlock's rating is at 10% distortion. I don't know how much clean power that would translate to, but I do know that the 1x12" cabinet that Crate sold as a match to the Powerblock head had a Celestion speaker that was rated at 100 watts.
From what I see on Celestions website the Tube 10 is rated at 30 watts and
only has 94dB efficiency. It is probably not the best speaker to use with the Powerblock, low power handling combined with low efficiency sounds like a recipe for disaster.

[Steve G]

Thank you people.
Can anyone explain the 10% distortion thing to me?

[Dacious]

It means the Crate's power rating is mostly illusory. It's probably more like 100 watts. The rating 'RMS' as it is mostly used means root-mean-squared, and takes into account peaks and troughs in power delivery. There's no rule that says you can't qualify power as before clipping (distortion) but that's the convention.

I still wouldn't run it through the Tube 10. You have to remember, an amp running on 100 watts RMS can spike to 3-400 watts, especially if you're driving it with gain-increasers. A speaker rated at the amps'' RMS figure will cope with that - that's called the 'peak' figure. Your 40 watter - maybe, maybe not.

You have no way of knowing that power, without a watt meter, or if you can calculate power by neasuring it at the speaker terminals; that even on 1/3rd volume it isn't producing 80 watts RMS. Amps aren't linear devices. It might work for a week or a month. The speakers' life also might be measured in months instead of years.