Re: Optimal amp load for SHL5
The two impedance charts have to be read together. What they tell is that the electrical resistance never drops very low (the left chart) and that as the electrical phase angle (right chart) hovers around zero degrees. This says, taken together, that the speaker presents a very benign load to the amplifier.
I demonstrated to Walter Swanbon (of Harbeth USA) when he was here last week that during the design of a Harbeth speaker crossover on my simulator I keep two screens open simultaneously. One shows me the predicted frequency response of that crossover plus those drivers and box and the other shows me the two electrical impedance charts. So, every time I change a component in the crossover model I can instantly see if it has an unwelcome effect on the load presented to the amplifier. If it does, I abandon that line of design, and find another solution even if that takes much longer and a lot of head banging.
As I have said before, it is of paramount importance to me that all Harbeth speakers present a relatively benign electrical load to the amplifier. We are a commercial business with the desire to sell more and to avoid after-care issues relating to amplifiers. That means, quite simply, Harbeth speakers will work with any and every credible hifi amplifier that exists.
The Monitor 40 is a rather special case. The load was more difficult but the new upcoming M40 has been comprehensively redesigned to be no more difficult than the SHL5.
Alan A. Shaw
Harbeth Audio UK