Thanks for all the suggestions. As BMS got so many mentions I went with them and got some 4524's. I set one up on some cheap eminence horn, probably not the best to try but I have a couple spare, and put it on a pile of half finished projects in the garden.
I included a roll of gaffa in the shot to give an idea of size (and point the horn down a bit). It really is quite a small driver.
I had a listen with various music and I am really impressed with it. I have never heard a compression driver sound like this. It's got the top end of a decent bullet and is unbelievable smooth, not a hint of harshness anywhere. I didn't have the equipment on hand to try any eq so used the cd horn eq on the cheap berry crossover, and this did seem like more than was necessary. A quick play with the ultradrive should have it sounding superb.
It's a very efficient driver, I had it on a 75w/4r amp and hardly turned it up. When I did crank it it got too loud too listen to at a few metres but still sounded great.
Time for the next project, diy hf horn.
Kieran

4528ND 1' Neodymium high frequency compression driver, 1' VC, 25 W AES, 113 dB and waveguide 90° x 60° 4540ND 1' Neodymium high frequency compression driver, 1.5' VC, 60 W AES, 114 dB. BMS compression driver H4550 @ 122,- euro's 80 watt's All these have better spec's than the original Paudio drivers and BMS recommends these as low mid drivers in compact cabinets. Anyone got experience with one of these?

Compression

Bms 4550 Compression Drivers For Mac

May 29, 2008  What do people think about a BMS 4550 compression driver with a BMS 2230 horn, with a crossover point at 900Hz, on top of two half MT 122 loaded with B&C12PE32? (I mean to build the MT 122 in three different cabinets, 2x12' + the top section).