Woven Kevlar cone

Rubber suround

Coated Cloth dust cap

Cast aluminium frame

Vented pole piece

Magnetically shielded motor

High DCR

We selected the woven Kevlar cone as the base cone material because it offers superior resolution through the midrange, yet is very light. The light cone allowed us to make a smaller magnet in the motor, that could be fully shielded with the addition of a bucking magnet and shield cup.

The cloth dust cap is actually made on a die machined for a 38mm dome, providing a wealth of upper midrange detail and together with the slight flare of the cone offers excellent dispersion.

The DCR of the driver is high (6.70 Ohms) so it can be used in the MTM configuration without creating a difficult load for the amplifier.

The motor uses a 38mm voice coil 14.2mm in height. The top plate is 8mm thick and the pole is extended 1 mm to extend the symmetric magnetic field in the gap. This geometry yields a very linear 7.5mm p-p excursion, far more than would normally be required from a 7 1/2"driver in a acoustic suspension or aperiodic enclosure.

The frame is heavily ribbed with a 6-bolt mounting pattern and a wide, tapered edge that can be flush mounted.

Theile-Small parameters are as follows:

Fs = 52.8 Hz

Qts = 0.744

Qes = 0.914

Qms = 3.993

Vas = 34.7 liters

Re = 6.70 Ohms

Bl = 7.61 Tm

d = 18.0 CM

Sd = 153.25cm²

recommended cabinet volume 11 to 14 liters, sealed or aperiodic.

At right is the CM-7 loudspeaker system built by Lee Taylor.