I didn't take this picture, but it's of the Scanspeak 30W/4558T00 12" Subwoofer.
It's featured in my previous sketch,  I think it would make a good replacement for the Yamaha 12" Woofer and add some missing depth to the bass. It's a fairly substantial driver as can be seen.

I think, because it has a low Fs of 17Hz, a reasonably large XMax and power handling, Scanspeak decided to place it in the Subwoofer category, it certainly gets used a lot for that application. But DIY builders including Troels Gravesen have used it as a straight Woofer in a three way. Below is Scanspeaks own frequency sweep for this driver.

Don't be too alarmed by the peaks and troughs in the lower section, Scanspeak plots always look like this. Where most manufacturers use smoothing on the plot, or include nearfield response at the lower end, to make it look better, Scanspeak prefer to give you the true results warts and all, they have to be applauded for doing so.

The thing that struck me about this plot, was how flat it is in the upper bass and how far it extends up the range, definitely a response more like a Woofer than a true Sub, with its typical hump back curve.

This driver has an Efficiency Bandwidth Product (EBP) of 49 making it best suited for a sealed enclosure.

Taking the standard Qtc figure for a flat response of 0.707 this computes as an F3 of 38Hz in an ideal 55L (Net) sealed box.

So, by keeping the same footprint for the cabinet, it would only be around 100mm taller than the 50L NS-1000M. It would probably perform well, if not ideal, in the Yamaha cabinet. Sealed cabinet pairings are less fussy about exact volumes, compared with tuned ported cabinets. It certainly ticks a lot of boxes for the Yamaha's, so not surprisingly, the spec grabbed my attention when I was checking out drivers for my other project.

Note: It's worth pointing out that this is better implemented as an active solution as this driver is 4dB less sensitive than the mid dome and 4ohm compared to 8ohm.

I tried the Scanspeak and Yamaha 12” Bass units in my semi active project, running them with Quad Bookshelf units, so have experienced their different traits under similar conditions.

My concerns about the Scanspeaks ability to perform in the upper bass and crossover region were unfounded and it out performed the Yamaha in every area. Obviously from the specification, it would have deeper bass, but its noticeably a lot deeper, which gives a strong platform to work with. Its faster and tighter, not that the Yamaha is poor in these areas, but the Scanspeak is better and can only improve in a more rigid cabinet. The big surprise was in its upper region, where it is subtle and tuneful, blending seamlessly with the Quad mid range. Comparatively the Yamaha bass is muddy and slow, not that I would ever have said that prior to the comparison, as I like the Yamaha's a lot. The weakest link with the Yamaha is the tweeter, raggy low end and falls off rapid at 15kHz. The Yam mid range is crossed quite high at 6kHz to deal with this. With a shallow filter slope the Mid range driver dominates well up the spectrum, the tweeter contributes little to the program as can be demonstrated by switching it in and out during play.

I'm building a Hypex DLCP/UcD Pre/Crossover/Power unit in another thread.

The plan for my next experiment, is to use this DSP set up to try the Yamaha Mid range with the Scanspeak Bass and Fountek Ribbon Tweeter. It's a modern take on what Yamaha produced and is the NS-1000M revisited. It has great potential, but only trying it will tell and satisfy my curiosity. The Fountek ribbon can be crossed from as low as 2300 Hz 2nd order. It might be nice to move the mid range crossover point down and away from 6kHz, where sibilance lies. 4kHz with a steeper slope might be a good starting point.

Looking at the Fountek Spec sheets, for the Neo X Series, the NeoX 2.0 has the flattest, smoothest response in the range. I was impressed with the NeoX 1.0 used by Quad and the NeoX 2.0 looks a bit better. So my plan is:

  1. Obtain a pair of NeoX 2.0 Ribbon Tweeters.

  2. Make Router templates for the Tweeter and Yamaha Mid Range.

  3. Construct a temporary Baffle to mount the Mid/Tweeter.

  4. Construct a lash up of the active Hypex DLCP to run this set up, using my Nakamichi Power amp.