Power and volume test

[gwEm]

I was thinking about your gigging with that 2w amp during all this testing Ben.

At the back of a 200 capacity room (10 or 12 meters away I guess) I measured 109dBa during the other band. Obviously that was mostly projected from the PA.

In a pub last night I measured 101dBa from about 4m away.

[Plenum n Heather]

The downside is that all of your headroom goes right out the window when you are playing an amp pushed that hard; I actually used my Strat and turned off all of the pedals going into my amp last night to get something close to a clean sound; it still have plenty of hair on it!

[gwEm]

some sums:

Apparently the relevant law is that sound pressure level drops by 6dB when you double distance.

so that 101dB(a) 4 meters from the pub band would be 113dB 1 meter away (+12dB), on the stage itself.

the Vox AC10 I played produced 109dB 1.5 meters away, which would be 112dB 1 meter away. so you would need a little speaker upgrade there to be comfortable for a pub gig.

speaker sensitivity is measured per watt, per meter. so a speaker with 100dB sensitivity would produce 100dB 1 meter away from a 1 watt amp. Ben uses a 103dB speaker and a 2 watt amp, so that would be pushing 106dB 1 meter away. this would be bone clean, so you'd have to have plenty of hair as Ben says for a small gig.

the AC10 produced 112dB 1 meter away, but that was with a medium crunch tone. If it was 10watts clean with a 95dB speaker (approximate number taken from Celestion datasheets), we'd in theory see 105dB 1 meter away. Very similar to Ben's number. We actually saw 112dB when crunchy though, 7dB more.

[gwEm]

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.

I've read some formulas which state if you double the number of speakers, you add 3dB to the SPL (edit: but only for lower frequencies where phase cancellation isn't an issue).

I wonder if this would work out in practice.

[gwEm]

This study is about to get a whole lot more serious.

I've ordered a more accurate sound level meter and also a sinewave generator.