HARBETH: P3ESR “… but this problem suggests that the crossover may be inadequately specified.”

"Stereophile has had reliability problems with several review samples, and the Harbeth was no exception. Toward the end of the review period, I was giving the speaker a workout with some high-level rock when the soundstage lurched to the right and the balance became bright and brassy. "What the . . . ?"

I turned down the volume, checked all the wiring, and played the track again. All was again as it should be. Again I turned the volume up, and again it all went wrong. "What the . . . ?"

I remeasured the quasi-anechoic response of both samples on their tweeter axes. At continuous levels below about 7V RMS (equivalent to 8W into the Harbeth's 6 ohm impedance), the responses of both speakers were the same as they'd been when I'd performed the formal measurements. But at sustained levels above that, the right-hand speaker (serial no. 0472R) developed a severe peak in its low-treble region. This peak disappeared when I backed off the level. I described this in an e-mail to John Marks, who had auditioned these samples before shipping them to me, but he had heard nothing such as this amiss with them.

All I could conclude was that, at the high power level, a crossover component had either opened or shorted, detuning the speaker's balance. Reducing the level apparently brought things back to normal, both with listening and measuring, but this problem suggests that the crossover may be inadequately specified."