I've never been happy with the three way speakers I have owned in the past, or, baring a couple of exceptions, those that I have heard. I found them sibilant, which I partly put down to the crossover point for mid/ tweeter being generally at 5 to 7kHz. This is at a very sensitive point for reproduction of human voice, as this is where sibilance lies and I was guessing that it might be part of the problem. Two way systems seem to suffer less from sibilance and I attribute this to the crossover point being much lower, at around 3kHz. One afternoon, I tried an experiment and sat an old pair of Tannoy M20 bookshelf speakers on top of my now active Yamaha NS-1000M speakers. I used a 2-way active filter I had, which crossed at 300Hz and fed the 12" Yamaha bass driver the low frequencies and the Tannoys got the higher frequencies, I kept the Tannoys passive crossover in place for mid/upper frequency separation. I was amazed at the results, the Tannoys were great at voices, but now they had a bottom end. This discovery is what kick started this project, my reasoning, when trying to predict what causes the sibilance, could be completely off track, but the results certainly aren't. I started to search for a pair of modern bookshelf speakers that were good with voices and which I could mate with a 12" Woofer or Sub driver. My idea was to use the drivers and crossover from the bookshelf speaker as part of a 3-way Semi Active Project (SAP), in a large sealed enclosure. After a lot of searching I settled on the Quad S-1 bookshelf speakers shown above, they got good reviews and I liked them when auditioned, preferring the way they handled midrange, to their larger Quad S-2 sibling. The specifications are as follows:

Description:                2way Ported
Mid/Bass Driver:         4" (100mm) Woven Kevlar No D-1100
Treble Driver:             12 x 45mm True Ribbon Model - Fountek NeoX 1.0
Sensitivity:                   84dB (2.83v@1m)
Peak SPL:                  96dB
Amplifier Power:         25 - 100W
Nominal Impedance:   8 Ohm
Response:                   58Hz - 20kHz (+/-3dB)
                                     (Tweeter is actually flat to 40kHz on Fountek's response plot)
X-Over Point:               3.2kHz
Cabinet Volume:          6.65L Gross 6.0L Net, Compleatly filled with stuffing
Cabinet Walls:              16mm
Dimensions:                 H285 x W156 x D240mm (Outside)