2x12 speaker impedance question

[postjob62]

If a 2x12 combo speaker setup (TR, Pro, etc.) , consisting of 2 eight ohm speakers wired in parallel for four ohm total impedance suddenly blows a speaker, is the amp suddenly seeing 8 ohms, still seeing 4 ohms, or something else?

If we follow the advice often given here that 2 speakers are not louder than 1, they just disperse the sound differently, I'm trying to figure out why my SFTR got a lot louder when I had a blown speaker repaired. Based on what I know about stereo amps, if the impedance suddenly went from 8 ohms to 4, that would explain it.

[Wally]

Well, I am of the school that believes that two speakers move more air than 1 speaker and therefore do create more apparent volume, given proper imepednace match and equal efficiency of speakers. I also subscribe to the school of thought that an amp produces best sonics at the rated impedance match. When your amp went to 4 ohms, you lost a bit of volume and the sonics got a bit darker sounding due to the mismatch. You also were moving only 50% as much air. When you got the repaired speaker back in the circuit, the impedance match created more output, a better frequency response, and the amp was moving more air.
To my way of thinking, that is more volume and better sonics.

[IronJoe]

I believe the circuit will still see the 2 speakers as a 4 ohm load. The fact that the speaker is not working properly does not mean that the amp won't "see" the load. After all, you still have 2 giant magnets wired in parallel whether the paper is moving or not.

It stands to reason that 1 speaker will be audibly quieter than 2 speakers because you have 12 fewer inches of speaker blasting rock and roll in your face. Volume and power are another issue altogether.

[Wally]

Originally Posted by IronJoe

I believe the circuit will still see the 2 speakers as a 4 ohm load. The fact that the speaker is not working properly does not mean that the amp won't "see" the load. After all, you still have 2 giant magnets wired in parallel whether the paper is moving or not.

It stands to reason that 1 speaker will be audibly quieter than 2 speakers because you have 12 fewer inches of speaker blasting rock and roll in your face. Volume and power are another issue altogether.

It is not the magnet that creates the resistance/impedance but the coil.
In a parallel wiring scheme, if one speaker coil goes 'open', that speaker is removed from the circuit and the impedance will revert to that of the other speaker/s...in this case to 8 ohms. In a series circuit, the entire circuit is interrupted and the impedance is infinite. EX: There is an Ampeg B-25 in the shop with one 15" Eminence with an open coil...infinite rsistance. The other speakers is an 8 ohm showing the proper 6.8 ohms resistance. When wired to the 'dead' speaker in parallel, the circuit still reads 6.8 ohms resistance and will reproduce signal from the head. If wired in the OEM series, the circuit is dead because the resistance is infinite.