plan, is to incorporate the Quad drivers and passive crossover, into a
sealed chamber within a much larger cabinet, designed for a 12"
Woofer. An active x-over will split the signal at around 300Hz and
amplifiers will power the Bass Driver and the assembly from the Quads.
The Quads are a 6.7L ported design, so the T&S
parameters of this small midbass driver are needed, to calculate the
volume of a suitable sealed chamber.
These results were measured for the two drivers.
Piston Dia: 83mm 83mm
SPL: 84.78dB 1w/1m 84.99 1w/1m
Re: 3.389 ohm 3.419 ohm
Fs: 80.08 Hz 82.1 Hz
Qts: 0.583 0.583
Qes: 0.716 0.737
Qms: 3.154 2.805
Le: 0.175 mH (10k) 0.176 mH (10k)
M(ms): 6.00g 5.67g
Vas: 2.707 L 2.718 L
A screen shot of the impedance sweep + T&S parameters for driver "A", can be seen on the next slide.
Using the figures for "A" and maintaining a Qtc of 0.707 this calculates as a Net sealed box volume of 5.8L (without filling) with an F3 of 97.1Hz. This is more than an Octave below my planed crossover frequency and with the active filter having a steep slope (24dB/Octave), this should work well. A sealed box of 4.0L will give a Qtc of 0.755 and an F3 of 97.6Hz. The higher Qtc of the smaller chamber could possibly benefit the mid range, conversely a well stuffed 4 liters will give a virtual volume of up to 4.8L, so there is a lot of scope for maneuver with the design of the sealed chamber.