The rising response of the Peerless HDS tweeter needs attention, from memory, certain tracks would have just too much at the top end and this seems to be the consensus of opinion, so it wasn't my system at the time being too bright or anything like that.
Several examples of waveguides that accomplish this have been circulated on the Internet.
I have chosen the simple version produced by "dlneubec" on htguide.com. Its only 12mm deep and has a full quadrant 12mm radius entry, so is easy to produce from 12mm MDF with a 12mm radius router bit. The mounting method needs a little more thought at this point.

Rather than reducing the response peak, the waveguide raises the level of the lower frequencies to give an almost flat response and by doing so, increases nominal sensitivity to around 96dB.

The following two plots (Courtesy of dlneubec) show first, the stock tweeter with its face plate mounted flush to the baffle front, and second, the face plate removed and the tweeter body pressed up against the rear of the wave guide, which was also mounted flush to the baffle.




The Stock Tweeter displays the typical rising response from around 7kHz to 17kHz.






The Waveguide lifts the low end and creates an almost flat on axis response from 4kHz to 18kHz.



Tweeters have been ordered from Falcon Acoustics so that critical dimensions can be checked, before construction of the wave guide begins.

As neither the mid or tweeter needs to be in an enclosure, I'm going to mount them on a separate baffle for testing. While waiting for the tweeters, I measured the mid range drivers flange and produced a routing template for it. I did a trial cut on some scrap MDF to make sure it was a good fit, as below.



As for the Scanspeak
bass driver, I will use it in the 55L sealed cabinet I used for my semi active project. Its only constructed from 18mm chipboard and is definitely a temporary look-see item, but in practice works well.




So the next stage of this project, is to finish the construction of this lash up and to use my Hypex DSP crossover, to dial in the drivers and see if they work well together.