I know we've been through this before. But, is 4 Ohm output into 8 Ohm Heresy speakers OK?

[Fool For A Radio]

I have just gotten a yard sale Voice Of Music 812 amp and preamp from a console recapped. I am burning to use it with the Heresy speakers I have not long ago got to working again. But the amp puts out 4 Ohms, speakers rated at 8. Sounds good, but not all that loud. Is this because on the impedance mis-match? Is this harmful to either the speakers or the amp? Can I do anything at the amp or the speakers to rectify the mismatch, or do I need to? Thanks.

[Deang]

Impedance changes with frequency, and the Heresy swings from 5 to 130 ohms. 8 ohms "nominal" doesn't mean much. You're fine on those four ohm taps of the amplifier. The reason it doesn't get "loud" is because it's a console amp and it probably doesn't have much power. '812' -- maybe the 12 in the model number means it has 12 wpc.

[Fool For A Radio]

I imagine you are right about the low power. It's a 6v6 push-pull design, and I am playing it in a big garage with a high roof, but still I thought it would be louder.

[paully]

Color me surprised but given the effeciency of the Heresys 2 watts should be enough to push them to ear drubbing levels much less 6v6 in a push pull configuration. Something is going on here and it is not the theoretical power of the amplifier which should be around 15 watts. It is either not pushing out enough juice because something is wrong or there is something else in the chain that is screwed up.

[DrWho]

I certainly wouldn't consider 2 watts into the Heresy to be very loud, especially because the 97dB sensitivity is only true when the speaker is in a corner (where you get 6dB of boundary gain).

You also have to consider that music has lots of transients, and some amps handle clipping better than others. If you figure even 10dB of transients in the music (which is very much on the low side), you're talking most of the music being 90dB at one meter with 2 watts of input. The peaks will happen at 2W, which will correlate to 100dB. But even with 20W you're just starting to push 100dB (with the peaks being 110dB). Throw this in a large room and subtract 6dB for every doubling of distance and you end up with not a lot of sound. For example, at 4m you're talking 88dB with 20W of input (and 98dB transient peaks). If your music has more transients, say 20dB (which is more common), then you're looking at 78dB continuous (with 98dB peaks).

If your amp is configured for 4 ohms, then that means at most, you lose 3dB of output, but you also make it easier for the amp to drive the speaker. So in a way, your impedance matching is actually better for the amp, except it doesn't let you take advantage of its full power handling. 3dB isn't going to be the difference between loud and soft though.