Wharfedale Diamond loudspeaker Lab Report

Lab Report

If there's one thing more remarkable than the test results posted by the Diamond – which, in most respects, a modern alternative could be proud to emulate – it's that this test pair has survived 30-odd years in what looks to be as-new condition. You'd expect such diminutive speakers to be insensitive, of course, but our pink noise result of 85.1dB SPL at 1m is significantly better than I was expecting, and would have matched many larger speakers of the early 1980s. What's more, this is achieved without resort to low impedance or a severely curtailed bass. With a minimum modulus of 6.6ohm the Diamond rates a genuine 8ohm nominal impedance, and the phase angles between voltage and current are sufficiently well controlled that the EPDR (equivalent peak dissipation resistance) falls to a minimum of 3.6ohm at 207Hz – double what we measure from many modern designs.


Forward response is impressively flat in trend with a gently rolled-off bass in free space conditions


Cabinet modes are well contained and there are only a few resonances in the high treble (>10kHz)

The forward frequency responses, measured on the tweeter axis at 1m with the grilles removed, are remarkably flat, with errors of just ±2.8dB and ±2.7dB respectively [see Graph 1]. Over the same 300Hz-20kHz frequency range the pair matching error is a little high at ±1.8dB but reducing the upper limit to 18kHz brings it down to a creditable ±1.0dB. Diffraction-corrected nearfield measurements show the bass output to be shelved down gently below 500Hz, until it's about 4dB down by 75Hz. But the bass extension is 59Hz (re. 200Hz), and using the Diamonds close to the wall behind will flatten out the shelf. The CSD waterfall [Graph 2] reveals some resonances in the high treble but the low treble and upper midrange are very clean. All that lets the side down a little is the high-ish THD at 100Hz, which is not unexpected given the driver size, and at 1kHz. KH

Sensitivity (SPL/1m/2.83V – Mean/IEC/Music): 85.4dB / 85.1dB / 84.8dB
Impedance modulus: minimum & maximum (20Hz–20kHz): 6.6ohm @ 413Hz / 20.2ohm @ 105Hz
Impedance phase: minimum & maximum (20Hz–20kHz): –63° @ 20Hz / 16° @ 20kHz
Pair matching/Resp. error (300Hz–20kHz): ±1.8dB / ±2.8dB / ±2.7dB
LF/HF extension (–6dB ref 200Hz/10kHz): 59Hz / 33.4kHz / 39.1kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m): 2.1% / 0.8% / 0.1%
Dimensions (HWD) / Weight (each): 240x186x191mm / 5kg