Since my second article back in February, I’ve done some re-thinking on drivers. I got a sample of the Vifa, but it my mind it was just too small. And too expensive for what it was. After finding and pouring over plans, I concluded that I could move to a 5″ class driver. After hours studying the Zaph Audio 5.5″ Driver Comparison page along with countless other resources, I decided try the SB Acoustics SB15NRXC30-8-UC for my prototype. For about $55, the distortion measurements are very close to the $200-$300 drivers he surveyed. On paper, it looks like the best 5″ value around. We’ll see how it sounds.
For the tweeter, I’ve had two ideas. One is to abandon the Tweeter-Super Tweeter-Tweeter arrangement completely and use a single tweeter with exceptional off-axis response instead. That is the reason Wright really went to the T-ST-T arrangement from what I can tell, to get good off-axis (the way the speaker was intended to be used) high frequency extension, not to extend on-axis response to 35K. The tweeter capable of crossing over at around 2K and yet having flat response at 20K @ 30 degrees off axis? Why the Seas SEAS 27TBCD/GB-DXT of course. The published data sheet shows the response 30 degrees off axis is only 1-2 dB down from the on-axis response. Wow!
This would be a major break with tradition though, which is disturbing to me. The center column then becomes a “regular” M-T-M. I wonder if Wright were alive today though if he would not do the same thing.
To take a more traditional approach, I’ve decided to change from the Scanspeak D2608/9130 that I had originally had my eye on to the SB Acoustics SB29RDCN-C000-4. This will allow me to keep the original driver spacing. I’d originally shied away from it due to the 4 ohm impedance, but with 94 dB sensitivity, I’ll have all sorts of room to manipulate the impedance in the treble. The M-T-ST-T-M configuration (I’m still using the NE19VTC-04 for the supertweeter) will look something like the picture to the left.