Headphones

I wrote in our recent test of the Meze Empyrean [HFN Dec '18] that, 'In recent years a new generation of isodynamic (aka planar magnetic) headphones has overturned this design principle's earlier reputation for low sensitivity'. Well, the Dekoni Blue is a planar magnetic to remind us of the old days! Its specified sensitivity of 92dB SPL for 1mW corresponds to a voltage sensitivity of 105dB for 1V at its nominal impedance of 50ohm. This is over 10dB lower than we measured from the class-leading Audeze EL-8 [HFN Oct '15], which would be a large shortfall in itself – but our measurements recorded 99.7dB sensitivity for the Blue, putting it over 15dB behind the planar magnetic state-of-the-art. It is so insensitive, in fact, that even at full volume it wasn't loud enough when used with the headphone output of my desktop computer. Proper headphone amps should be up to the task of driving it [up to and including the 4300mW/25ohm Benchmark HPA4 – HFN Nov '18], but other devices may struggle.

As with most planar magnetics, the Blue's impedance is almost constant over the audible frequency range so it will not suffer significant frequency response modification with any (preamp) source impedance it's likely to encounter. But zooming the impedance versus frequency graph (not shown) reveals low-amplitude ripples which suggest the presence of midrange and low-treble resonances, and this was borne out by cumulative spectral decay measurement. Uncorrected frequency responses [Graph 1, above] are characterised by a rising output below 500Hz to a peak at 80Hz, after which the response rolls off, and by a 'proper' peak around 3kHz whereas planar magnetics are often reticent here. The effect on the corrected responses [Graph 2] is a large peak in the upper-bass – more typically, planar magnetics have better-extended LF response – but well maintained output through the presence band (2-8kHz) where competitors are often lacking. KH