High Efficiency Speaker Asylum

Need speakers that can rock with just one watt? You found da place.

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RE: like already said Multiple drivers for each pass band.

Posted by Tre' on April 23, 2017 at 08:02:43:
I've always been confused by that.

2.83 volts across 8 ohms is one watt.

2.83 volts across 4 ohms is two watts.

2.83 volts across 2 ohms is four watts.

If you have a speaker that will give 87db from one watt and you add another in parallel you get 90db from one watt. Add three (for a total of 4) and you get 93db from one watt, not 99db.

What am I mis-understanding?

I am going to guess that it's because I think in terms of tube amplifiers.

I think of using the 8 ohms tap for one speaker and the 4 ohms tap for two speakers and the 2 ohm tap for four speakers so the amplifier does not output twice the power just because the load impedance has decreased every time the load impedance is halved. In fact it stays the same because the load seen by the output devices stays the same.

Now that leads me to the idea of series/parallel.

The power output of a transistor amplifier only doubles when the load impedance halves so if the speakers are wired series/parallel, to keep the load impedance at 8 ohms, then four speakers vs. one would be 93db vs. 87db even for a SS amp. You would only get to 99db if all four were in parallel.

Tre'