Pure Audio Project open baffle speakers

douglas:

Well I decided to build my own active XO, based on a class A discrete op amp design (a modified Spectral design using a Pass Labs type JFet output stage). Took quite a while to build and test due to the number of amps involved. Also had to procure two more JC-1s. I substituted the Voxative midrange driver for the Horn, and cross the bass drivers over at 400 Hz with 4rth order Linkwitz Riley slopes.

Resulting sound is amazing. Best my system has ever sounded. Considerably better than the Horn 1 with the passive Leonides XO. I have yet to try the horn with the electronic XO (400 Hz is probably a bit too low and would have to alter my XO point to 800 Hz), but the Voxative sounds so good I may not bother with the horn. Gone is all the stridency in the vocals and the symbols and bells are wonderful. 

douglas:

As an addendum, since you mentioned VH Audio. I am using their teflon caps in the critical low pass and high pass filters.

dhl93449, congratulations on advancing your system! It's obvious you had a goal and know how to achieve it. This supports once again the conclusion that an active x-over holds the potential to outperform a passive. The addition of two more amps completely changes the game with any speaker; properly, you have done upgrade to speaker and to amplification. The power delivery and crossovers have changed, and that is a radical upgrade to a system - as is evidenced by your obvious pleasure with the result.  

Just because the results are fantastic doesn't mean it can't get better. Why not try the horn to get it to the same, and perhaps higher level of sound quality? If you have the driver available, I strongly suggest you do. Try all permutations. If it were me, I would work to achieve the absolute best with both, then have the option of swapping them out for variety. Especially since you have put in a fair bit more money in buying two additional JC1's, I would want as much result/performance as possible.  

Doug:

I know its been quite a while since your last post to this string but here is my update to your suggestions. I tried the horn again and lowered the XO point to 400 Hz. Still was not that satisfied as there appears to be something missing at the very top end. Sold them (the PAP horns) and the new buyer confirmed the same observation. Many have added a "super tweeter" to the horn to fix this, but since that requires yet another XO point, I decided not to pursue this complexity as my current active XO is two way only. My in room pink noise measurements confirmed a drop off in frequency for the horns at about 10-11K Hz so this explains a lot. The Voxativ AC 1.5 reaches up to 15-16KHz in the same setup. The Voxativ is nice and flat with the main speaker chassis pointed straight ahead (as the off axis response is flat). They have a slight peak at 10KHz on axis, so I listen to them straight on (an not towed in as with the horns).
One additional advantage I have found with my active XO. I can tune the upper frequency response (to the Voxativ) by 0.5 dB increments and this really helps in tweaking certain recordings. I also built in an old school Yamaha (80's era) high frequency "tilt" control which tilts the HF response by variable degrees ( 1 through about 6 dB at 20KHz; hinged at 800 Hz). Don't really care for this much as the fixed shelving response works better for me.

One additional addendum. Looking to perhaps upgrade to the Voxativ PiFe. This is the driver similar to the AC 1.5, but with wood cones and phase plug. Cannot find any comparisons between these two drivers, except from Ines at Voxativ, who claims the wood makes the driver smoother and more detailed. Comes at quite a cost as these are about $5K a pair. 
It would be a plug and play replacement for the AC 1.5 as far as the XO goes, which makes life simple. Another suggested tweak is to replace the Al metal phase plugs in the 1.5 with a wood version from the upper end drivers, but I'll be d'mned if I cannot get a grip on those plugs to remove them.