Home Amp/Preamp Asylum

Looking for a new Amp or Preamp? If you're after tubes, post over here.

In most rooms this won't work! Here's why:

The speaker **sensitivity** is 89 db. The impedance is 4 ohms.

The amp OTOH makes 20 watts whether its 4 or 8 ohms.

Now here's the tricky bit:

The sensitivity spec is 2.83 volts at 1 meter. 2.83 volts into 4 ohms works out to 2 watts.

So your efficiency of the speaker is only 86 db 1 watt/1 meter.

In my room which is 17' by 21' I would need about 800 watts to really make that fly. I used to have speakers that were 89 db and I found that 200watts was not really enough power if I was pushing it. 400 watts might have been enough in my situation; now imagine that the speaker needs 3 db more power and now you see why I would need 800 watts(!) with a speaker like that.

That is very very inefficient, bordering on criminal as the amplifier power requirements become profound; there really aren't any amplifiers made that sound like music and make that kind of power.

This is not to say that the amp won't play- it will and might sound pretty nice, but you won't be able to turn it up much in an average room.

The fact of the matter is that tube power is expensive; back in the old days when tubes were the only game in town that is why there were so many high efficiency loudspeakers. If you are really sold on tubes, do yourself a major favor and get a speaker that is higher efficiency **and** higher impedance!

Tubes in general will perform better on higher impedance speakers- going from 8 ohms to 4 can cost you an octave worth of bandwidth on the bottom end due to the output transformer. Plus the transformer will be less efficient so it will run warmer. OTOH with an 8 or 16 ohm speaker the tube amp will not only have more bandwidth, but its distortion will be lower and you might have a slight amount of more power.

Good Luck!


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