The Nightingale

By Lars Mytting
02 Nov 1996

ScanSpeak 8565-1

The cone on this driver is made from coated paper, made with a new technique that has given a extremely stiff and rigid result. When tapping on the cone, it answers with a quick, stiff "click"; not the slow, lazy "tap" often heard from standard, softer cones. This is a very rough, but useful indication of low energy storage, and the measured impulse response of the driver also looks promising. The sound is fairly light and clean up into the lower midrange region, making it possible to use in a 3-way system with a passive crossover. But do not cross high; this driver har a +10dB peak at 2000 Hz... not exactly easy listening.

More important with this driver is the extremely low resonance frequency. I measured the samples to 18,5 and 20,5 Hz! This, together with sympathetic values for Q and Vas, make a linear response down to the very lowest octave available without going to the very extremes in box volumes.

The frequency response and impedance of the ScanSpeak 8565-1 shows adequate consistency. Worth noticing is that this driver has a +10dB peak at 2000 Hz.

On the two samples, there are some differences in their respective Thiele/Small parameters. This is rather common from many driver manufacturers, and in this case, the values summed up so that there was no practical difference in response in a standard cabinet. But it still something to be aware of. Again, the discriminating speaker builder should demand from a good dealer that they deliver individually measured speaker drivers in reasonably matched pairs. This driver is expensive, and if you want to save money, you could try the Vifa PL26WR-09-08, which share many qualities at half the price.

Then the Thiele/Small parameters. The values given beneath should not be used for final box calculation. The Clio system is extremely precise on Thiele/Small parameters, but I had not available a test box that was 100% appropriate for the drivers. However, both drivers under test met exactly the same conditions, and the values are true with respect to the differences between the samples.

Sample A        Sample B
Fs      20.5 Hz         18,5 Hz
Vas     167 l           209 l
Qts     0.37            0.32
Qms     4.25            3.99
Qes     0.41            0.34
Mms     49.49g          48.50 g
Cms     1.21            1.51

The differences in parameters may appear to be significant, but in real life, the values interact so that the total difference in behaviour is very small when placed in a cabinet. A "perfect QB3" cabinet for sample A is 112 litres and a 8 cm port of 21 cm length, giving -3dB of 24 Hz. For sample B it is 88 litres with a port of 8x26 cm, yielding a -3dB of 27 Hz.

The official Scan-Speak parameters of this driver is Qts 0.33, Vas 222 l, and Fs 19 Hz. If we use these values when calculating our QB3 box, we get a recomended cabinet size of 103 litres, and a 8 cm port of 22 cm length. And when we place sample A and B in such a cabinet, they both yield a -3dB response at exactly 25 Hz.

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