The Nightingale

By Lars Mytting
02 Nov 1996

Seas W17EX002

The most extraordinary with this 6,5" driver is the cone material, which is made of magnesium. It also utilizes a phase plug of solid copper, and a copper ring in the magnet system to reduce distortion. Seas' own measurements shows impressive low coloration and low distortion, and this is really something which is hearable. Subjectively, it is very distinct and clean in the whole midrange region, with less grey curtains than similar Seas drivers with polypropylene cone. In the range from 100 to 500 Hz, it really is ahead of most drivers, with measured distortion 10 dB less than a standard polypropylene cone. This is definitely hearable.

The driver uses the standard Seas chassis, and has four mounting holes. What may be of interest is that on the latest series of these chassis; there are pre-drilled four additional paths for mounting holes. Just grab your drill and you have eight mounting holes. I guess that in time; Seas will supply four holes for the British market and eight for the American. (The French will probably demand five).

Back to facts. The main concern with this driver is that the magnesium cone has a natural resonance that creates a large peak (approx. 20 dB) at 5000 Hz. This calls for special attention in the crossover. If it is not corrected, it will cause a "ringing" sound. Success or failure with this driver is tightly correlated to the damping of this peak. From the waterfall plot, we may also notice that there is a resonance at 1800 Hz, but otherwise the response is very clean Fig. 3. Seas W17EX002 waterfall.

The two samples showed good consistency, and both frequency response curves were very tight. (See measurement section for graph). What was most exiting with the measurement was the impulse response. It has truly exceptional symmetry. The extreme "oscillation" is probably correlated to the 5000 Hz peak and its implied ringing. The "oscillation" is gone when applying the proper crossover Fig. 4. Seas W17EX002 impulse response.

For comparement, this is the impulse response of the W17EX001, which is essentially the same driver, but with glass fibre cone. This one is also measured without crossover Fig. 5. Seas W17EX001 impulse response.

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