Great points by Ralph, as usual, with which I agree.
09-25-14: Charles1dad
Ralph, there's something that doesn't make sense concerning your comments about speaker designers. These designers have to have at the very least a rudimentary understanding of science and engineering. Something as basic as Kirchoff's law has to be easily comprehended and applied. They have the equipment available to confirm that concept and its effect. I just don't understand why you would be met with such resistance to something so plain and fundamental. How do these designers counter your point/position?
Charles, pending Ralph's answer, as I see it the key to reconciling that is the fact that the majority of speakers are designed with solid state amplification in mind. And with a few unusual exceptions, nearly all solid state amps (in contrast to tube amps) are designed to provide an output voltage which does not vary significantly as a function of load impedance, as long as the amp is operated within the limits of its voltage, current, power, and thermal capabilities.
Therefore, as a consequence of Ohm's Law and the definition of power, while of course not all solid state amps will double their rated MAXIMUM power capabilities into halved load impedances, nearly all of them WILL double the amount of power that is delivered into a halved load impedance (albeit perhaps with some increase in distortion), as long as they are operated within those maximum limits.
So when Ralph says:
If you have a single woofer and put one watt into it, it might make 92 db at one meter. If you have two of the same woofers in either parallel or in series and put 1 watt into the array, the result will be the each driver will have 1/2 watt on them- and the output will be exactly the same 92 db.
... Note that he refers to an input of 1 watt.
If he had referred to an input of a given number of volts, say 2.83 volts (which corresponds to 1 watt into 8 ohms, as he indicated), applying that voltage to two identical woofers in parallel (which together have half the impedance of a single woofer) would cause twice as much power to be delivered as if the same voltage were applied to only one woofer. Resulting (everything else being equal) in a 3 db increase in SPL. And conversely, applying that voltage across a combination of two identical woofers in series (which together have twice the impedance of a single woofer), would result in half as much power being delivered as if the same voltage were applied to only one woofer, resulting in a 3 db reduction in SPL.
Basically, the speaker designers Ralph referred to are thinking in voltage terms, rather than power terms. Which is arguably reasonable in the context of most solid state amplifiers, but can be very misleading when it comes to tube amps.
ZD, thanks for the nice words.
Best regards,
-- Al
