Speaker resistance question

Can't remember how to work out speaker resistance.....

If I have 2 speaker cabs both of which have 8 ohm drivers is the total 4 or 16 ohm. And how can I make a double loaded cab with 2, 4 ohm drivers be an 8 ohm cab ? ? ?

2 4 ohm drivers in series will give you 8 ohms.

B.P.Sound wrote: Can't remember how to work out speaker resistance.....

If I have 2 speaker cabs both of which have 8 ohm drivers is the total 4 or 16 ohm. And how can I make a double loaded cab with 2, 4 ohm drivers be an 8 ohm cab ? ? ?

If you have a number of speakers in parrallel, and they are the same resistance, then divide the resistance by the number of speakers.

ie 2x 8R in parallel = 4r
4x 8r in parallel = 2r
2x 4r in parrallel = 2r

for series simply add them together
2x 8r = 16r etc...

What if the resistance of each speaker is different? (I came across a diagram which someone had 'wrote' the same as above, but with different resistance's)

Just want to make sure

I think it works out at a quarter of the sum total of the two if in parallel?

8 and 4 would give 3 ohms

Happy to be shot down by electrical bods though, what is the actual answer?

Also why are 3 x 8r 2.66 not 3?

Answer. 8 divided by 3 is 2.66.
One other configuration not mentioned. Series Parallel. 4- 8 ohm speakers =8 ohms. each pair of speakers wired in series to give 16 ohms then parallel each pair to give 8 ohms. or visa versa.
also you cannot bump up impedance by slipping a high one in. e.g. 8+8+8+16.=1.5 ohms. etc.etc.etc.

Scuba wrote: What if the resistance of each speaker is different? (I came across a diagram which someone had 'wrote' the same as above, but with different resistance's)

Just want to make sure

easy .. lets say you had a 2, 5 and 7 ohm speaker ... just to make the example interesting

in series:

2+ 5 + 7 = 14 ohms

in parallel:
1 / ( 1/2 + 1/5 + 1/7) = 1 / 0.842 = 1.186 ohm.

quick sanity check: when in parallel the final impedance will ALWAYS we lower than the smallest impedance, so in this case it MUST be under 2 ohms.