Is There a Formula?

[jtc_hunter]

In comparing volume and presence, is there a formula for volume comparisons, lets say for example:

A. one 212 cab 4 ohms powered by a 400 watt head (4ohm)

now how would the volume and presence difference be compared to:

B. one 212 cab 8ohm, plus a 210 cab 8ohm powered by the same amp.

To set the field, lets say its all good quality equip. Is there a formula or a % rule of thumb?

 

[billfitzmaurice]

There are formulas that can predict combined responses, but they are quite complex, and they would require an accurate SPL chart of the cabs in question, which no manufacturer of 2x12s and 2x10s provides. Rough rule of thumb in your scenario is that you might get an additional 3dB or so with four drivers versus two with the same impedance load on the amp.

 

[jtc_hunter]

3db is really not that much , is it?

 

[A9X]

3db is really not that much , is it?

Nope. But it might make a significant difference to you as the drivers will be excursing half as far for the same SPL, hence lower distortion (depending on preference this could be good or bad) and less thermal compression.

I personally wouldn't bother with a 3dB increase. To get my money, 6-10dB is required, whatever the means of obtaining it.