MEASURED PERFORMANCE

Our pink noise frequency response shows the Vulkan VIII has an impressively flat frequency response (green) with the measuring microphone vertically aligned midway between ribbon tweeter and midrange unit, putting it at typical ear height. Vertical dispersion of the ribbon is sharply defined so a little higher restores treble above 10kHz, whilst on the tweeter’s central axis treble rose to +7dB at 10kHz (grey trace) – a large rise. Although vertical dispersion is constrained, like most ribbon tweeters, lateral dispersion is smooth and wide, so Quadral’s big ribbon throws quite a lot of treble energy out into a room and this will give the Vulkan VIII a bright demeanour, even though the on-axis response may seem to suggest otherwise (depending upon where the ear is).

At low frequencies the bass unit reaches down to 70Hz and the large underside port takes over below this frequency, peaking at 30Hz our red trace shows. This puts a lot of bass energy into the room, the port being a huge drainpipe affair (large ports produce less distortion). Bass does not peak up and is in good balance our response measurement shows. A decay graph showed low coloration except for an overhang at 80Hz.

Sensitivity was very high, the Vulkan producing 92dB sound pressure level from one nominal watt of input (2.8V). In fact, with a very low impedance of 5 Ohms overall they consumed more power than one watt, but they need little power to go loud all the same, 40W is enough. An infinite DCR value suggests Quadral are using an input capacitor. Our impedance trace shows the loudspeaker is almost perfectly resistive and an ideal amplifier load, so it is not difficult to drive.

The Vulkan VIII is a relatively accurate loudspeaker providing it is listened to just below the ribbon tweeter. It will have a bright character all the same, but should sound quite dry in its bass. NK

FREQUENCY RESPONSE (what it means)

Green - drive unit; Red - port; Grey - tweeter axis

IMPEDANCE (what it means)