single vs duo speaker combo amps

[donnellbw]

Is there any real sonic difference between say a 50 -100 watt tube combo with 1 X 12" speaker vs. the same amp with 2 X 12"s? Is it "louder" or just more widely dispersed? Same thing with a single 12" combo adding an aux 12" speaker. What's the deal. I like 2 X 12 combos for the "cool" factor, but is a single speaker combo doing the same job with less?

It seems to me that more speakers doesn't do more loud. Am I wrong? Also how does more than a single speaker affect the sound of a drive channel. Does solid state make any difference besides the way it creates its sound? Just curious.

Thanks, Forumites.

[beatlefreak]

It seems to me that more speakers doesn't do more loud. Am I wrong?

It depends on the impedance of the speaker(s) in question. If, for example, the speakers are all 8 ohms, connecting two of them would give a 4 ohm load to the amp, as they'd be connected in parallel. In theory, this would double the output power of the amp, but it never quite works out like that in reality. But it will be louder.

[sharkboy]

I have actually tried doubling the speakers at the same load and perceived greater volume. This is partially a psychoacoustic effect, but I did measure a slightly higher number on a db meter (contrary to what I've read, which suggested that sound pressure doesn't change, but is perceived higher, but this may also have to do with non-scientific methodology- speakers were not all individually measured for sensitivity.) I believe that true or not, about 3db is what would be believed by the ears as the bump of doubling identical speakers (at an identical overall load.) Think of it as two sound pressure devices doing the same thing: pushing sound waves. Doubling the sources will have an effect on the receptors (ears) since they are radiating at different locations.

This is before we get into what happens with different loads or using speakers with different sensitivity ratings, which will make a difference from an electromechanical standpoint.

[jps]

I have actually tried doubling the speakers at the same load and perceived greater volume. This is partially a psychoacoustic effect, but I did measure a slightly higher number on a db meter (contrary to what I've read, which suggested that sound pressure doesn't change, but is perceived higher, but this may also have to do with non-scientific methodology- speakers were not all individually measured for sensitivity.) I believe that true or not, about 3db is what would be believed by the ears as the bump of doubling identical speakers (at an identical overall load.) Think of it as two sound pressure devices doing the same thing: pushing sound waves. Doubling the sources will have an effect on the receptors (ears) since they are radiating at different locations.

This is before we get into what happens with different loads or using speakers with different sensitivity ratings, which will make a difference from an electromechanical standpoint.

Identical drivers that are close coupled will, in fact, produce a 3dB increase in SPL. Now if said speakers were hooked up to a solid state amp that can double it's output with the load impedance halved, then you get 6dB more output.

[donnellbw]

Thanks, guys. I had read that some tube amps that add a speaker raise the percieved output. Your remarks have helped clarify what is going on to achieve that.

Happy Spring.