This beautifully made driver was designed from its inception be used in MTM applications in both main and center channels. It is also well suited for 2-way monitor applications when used as surround or with a subwoofer.

Because the 19W will often be used in MTM's, we felt it essential that the DCR be high enough that most amplifiers would be comfortable driving two of them in parallel. We therefore specified a DCR of about 7.0 Ohms, so in practice the MTM's pair impedance would not drop below 4.0 ohms.

High DCR's generally mean low sensitivities, so for the 19W we selected woven Kevlar cone as the base cone material because it is very light, and also offers superior resolution through the midrange. The light cone allowed us to make a motor with a smaller magnet, which could be fully shielded with the addition of a bucking magnet and shield cup. The driver's overall sensitivity is 86.3dB, perfect for an MTM.

Because we required smooth response to 2.5kHz, we specified a treated cloth dust cap. The dust cap is actually made on a die machined for a 38mm dome midrange, providing a wealth of upper midrange detail and together with the slight cone flare offers excellent dispersion. The North 19W exhibits a remarkably smooth frequency response of +-2dB from the box tuning frequency up to nearly 3kHz.

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 lengthen 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. For monitor applications, the recommended alignment is an aperiodic cabinet, volume 15 liters (0.53 cubic feet), with a single high-QL Scan-Vent. For stand-alone applications, an MTM is suggested with internal volume of 30 - 40 liters and a standard Scan-Vent. The target Qtc is between 0.9 and 1.2, easily adjusted and optimized by ear by adjusting the Scan-Vent QL.

Theile-Small parameters are as follows:

Fs = 51 Hz

Qts = 0.75

Qes = 0.92

Qms = 4.0

Vas = 38.2 liters (1.35 cu. ft.)

Mms = 22.8 gm

Bl = 7.5 Tm

Reference SPL = 86.3dB @ 2.83V, 1 meter