The 60 Ohm Speaker Tweak

Recently I examined a pair of high end, very popular, speakers. I was caught off guard when I saw what appeared to be an impedance compensating circuit to dampen the peak at the crossover point.

A circuit like that takes at least 3 parts, and needs to be executed carefully, but there's another similar idea, which I'm going to call the 60 Ohm resistor tweak.

The idea is extremely simple. If you have a speaker with a reactive impedance, which is no less than 4 Ohms at any given point, put a 60 Ohm (or higher)  resistor in parallel with it.

What this will do is flatten out the impedance so that the peaks are a lot lower compared to the rest of it. For instance, in my own speakers, there's a 40 Ohm and a 25 Ohm peak which are brought down to 23 and 18 Ohms, respectively.

Resistors are cheap, if you have tubes, or reactive speakers you might want to try it. Of course, if you decide to keep it, make sure the resistor wattage is about 15% of your maximum power.



Good idea.  

I prefer the actual impedance compensation circuit, but a large value resistor in parallel with everything, as you describe, is a much simpler approach, and can probably make a worthwhile net improvement in speaker compatibility with a tube amp.  (I say "probably" only because I haven't tried the resistor-only approach you described, but it looks promising "on paper".)

And I echo your caution to keep the thermal power handling of the resistor fairly high.   I was advised by an engineer who designs prosound woofers for a major driver manufacturer to down-rate resistor wattage specs by 50% for high-duty-cycle applications, which imo would include being paralleled with a fullrange loudspeaker system.