Power and volume test

[gwEm]

I got myself a cheapo dB meter and did some measurements on all my amps. The results were interesting to say the least.

I used an attenuator on all the amps set to the same setting, which may have influenced the results. I used the same 1x12 cab with the dB meter offset from the speaker, about 2m away to try and simulate a gig. I set the valve amps as loud as they would go and the solid state just below where they started to clip.


Mesa Boogie Mini Rectifier 87dBa (25w)
Hughes and Kettner CF100 91dBa (100w)
Marshall JCM1H 85dBa (1w)
Marshall JMP50 87dBa (50w)
EHX Magnum44 90dBa (25w)

I didn't expect the solid state amps to be as loud as they were. It looks like 'valve watts' are not louder after all. I wonder what the results would be without the attenuator, even though they were all set to the same setting for each of the amps, it may have had an effect.

[gwEm]

I should say I dialled in as close a tone as I could on the amps - a medium crunch. On the solid state amps I used a pedal. I might make a similar test with a clean tone. I would expect different results of course.

[AndyR]

I'm watching this with interest.

Last night I did find myself wondering - you've got a range of 85-91 dBa there... my understanding (limited!) is that there wouldn't be a big difference in actual "volume" over a range like that? But I could very easily be completely wrong about that.

[gwEm]

I should also add the JMP50 sounds by far the best. The Mesa and JCM1 sound about as good as each other. Then the H&K sounds decent and the Magnum 44 is just about satisfactory.

The JMP50 has a lot of lowend balls which is hard to quantify in these numbers.

The CF100 is definitely the loudest of the bunch (slightly). All the rest do sound about the same volume, except for the JCM1 which sounds about half as loud.

[gwEm]

Myself I am a bit concerned by the numbers, if they make sense. I expected the JMP50 to be by far the loudest. But I measured very carefully. Perhaps the speaker configuration makes more of a difference to actual volume in the room.

[Dave Sloven]

Jesus, I have never run my Peavey 6534+ above 5 on the lead channel.  I usually run it at 3 and that's with ear plugs in.  I wouldn't attempt full volume without chainsaw ear muffs on.

That said the clean volume is a lot lower.  With crunch switched off and the pre-gain down low to get a good clean 5 on the post-gain would seem to be as loud as 3 on my lead channel.

My old Peavey Classic 30, on the other hand, was hard to hear properly over the drummer even when cranked.

[gwEm]

Jesus, I have never run my Peavey 6534+ above 5 on the lead channel.  I usually run it at 3 and that's with ear plugs in.  I wouldn't attempt full volume without chainsaw ear muffs on.

That said the clean volume is a lot lower.  With crunch switched off and the pre-gain down low to get a good clean 5 on the post-gain would seem to be as loud as 3 on my lead channel.

My old Peavey Classic 30, on the other hand, was hard to hear properly over the drummer even when cranked.

Yeah, I used an attenuator which may have made a difference.

My JMP50 doesn't get much louder after 6 anyway. I have used that cranked unattenuated in the house. It was very very loud, but not painful.

I also question the accuracy of the sound meter (though I didn't think it was completely wrong)

But I've been thinking about this - as long as you are around the same volume as the drummer that's all you need.

I'm expecting different results with the clean test.

Edit: did you play the classic 30 and the 6534 through the same cab?

[Dave Sloven]

No, the Classic 30 was a combo and I never connected it to a cab.  It did replace the Blue Marvel with an Eminence Wizard and that made it considerably louder, but it was still not loud enough in a band context

[Dave Sloven]

I have heard a really stupid band with two 5150s that were so loud that I couldn't stand being in the same room WITH EARPLUGS.  I had to stand out in the alleyway.  I did get a look at their settings before I ran off, and they had the post gain on the red channel around 7.  Peaveys can go stupid loud.  These guys really needed a good slap around the head.  Here's a video of them to give you an idea of the style.

https://www.youtube.com/watch?v=pezeyZoYQ1c

[gwEm]

Measured 110dB(A) last night at rehearsal which is another good data point. I have the feeling we play a bit quieter live.

Off for a little tour tomorrow. I'll do the clean tests when I get back.

[gwEm]

No, the Classic 30 was a combo and I never connected it to a cab.  It did replace the Blue Marvel with an Eminence Wizard and that made it considerably louder, but it was still not loud enough in a band context

I have the feeling speakers make a large difference to sound level in the room. I'd like to research this more.

For example if you have the same 50w head, would the SPL be the same through a 1x12 vs an 8x12 full stack? Same speakers loaded in all the cabs. This question has always bothered me.

[blue]

interesting stuff.  I think a lot of us have trouble equating a Db reading to how loud something actually is, and it being a logarithmic scale doesn't help. 

[gwEm]

I agree Blue. And I think the power in watts and speaker sensitivity quoted by manufacturers can be taken with a pinch of salt.

I'm on tour right now and tried a Vox AC10 combo (2xEL84, 1x10") in a music store. Managed to get 109dB(a) out of it (crunchy rock tone) about a meter and a half away. So definitely fine for rehearsals, and perhaps a small unmiced gig with a speaker upgrade.

[gwEm]

111dB(a) on stage tonight. Didn't really feel like it though(!)

[Plenum n Heather]

About 100dB for a normal sized gig from a guitar amp is about right for rock music. What would be interesting to know is at, say 100dB, how much headroom is left in each one of those amps?

I know that I have to use VERY sensitive speakers to get my 2W Studio 2 near that level; through your standard V30 loaded 4x12 it can't keep up with the drummer. But it's much better through my Wizard-loaded 2x12 (103dB sensitivity).

Last night we played a medium sized stage and I used my Bumbox (rated at 35W by the builder) into the house 4x12. Turned up 2/3 and my BB Preamp set at unity gain, it was L O U D. Probably about as loud as you got, gwEm -- had to be around 110dB.