comparing volume levels with ultiple speakers

[black_labb]

ive started planning for a guitar amp i am planning on making a guitar amp after making some guitars and pickups. im planning on doing a 5e3 now but with a 2x10 cab (the ot i picked up is suitable for an 4ohm impedance, so this should work well). my question is, how would one expect multiple speakers to effect sound volumes compared to a single speaker. ie, a 12" rated at sensitivity of 99 (decibels at a metre at 1 watt) compared to 2 x10" rated at 96 or so? i want a fairly efficient speaker system, but am a bit unsure how 2 speakers will effect the decibel levels.

thanks for the help.

[pdf64]

When you double the number of (identical) speakers, the sensitivity goes up by 3dB, ie 2 x 10" @96dB/watt each will give a combined sensitivity of 99dB/watt, 4 x 10" would give 102dB/watt etc.
A 3dB increase in sound pressure level is also what you get when you double the amplifier power ie a 40watt amp into 1 x speaker will give same effective maximum sound pressure level as a 20watt amp into 2 x speakers (of the same type as the 1 x speaker).
If you need to use a 5e3 at a group gig, especially if you need a cleanish chord now and again, I'd advise a 2 x 12" cab.
Hope that helps - Peter

[MWJB]

Another consideration is how the different speakers disperse the sound. Everything else being equal, 10" tend to be more directional than 12". So 2x10" (96dB each) may match 1x12" (99dB), but you may have to have the 2x10" amp mounted at chest/head height to really appreciate it.

A 5V4 rectifier and a bigger main filter cap will also make the amp more efficient.

[black_labb]

thanks guys, i actually had in the back of my head the 3 decibel increase, hence the 99 and 96 nuumbers. i didnt know where i got it from, may have been my own theorising knowing about the 3 db rise in doubling wattage.

im not so much interested in clean sounds, im more looking for a bluesy overdrive from the 5e3.

i just ordered the 2x 10" speakers from warehouse guitar speakers as ive heard a fair bit about the 12" ones. has anyone tried the 10" ones? it doesnt really say what they're copying. either way im sure ill be very happy with the sound i get in the end, coming from a 100 watt solidstate fender (it sounds great for a fairly cheap 2x12 amp, but a 5e3 should have exactly what im looking for, and i have an obsession with making anything and everything related to my hobbies)

i will be putting some legs on the back of the amp or similar to angle the speakers up, which should help the 10"s get the sound to me