I've been playing with a crossover simulator called XSim on and off, and implementing the changes using cheap Monacor caps, coils and resistors.
This was with deliberate view to changing the frequency response of the mid range and treble ribbon on the speakers this thread was raised to discuss.
A few weeks ago I decided after a few months of listening that the actual electrical values were good i.e. the target frequency response was met. So I swapped out the cheap components and put about £250 worth of PathAudio resistors, a very hefty Jantzen cross coil, and some Jantzen Alumen Z-Caps in.
What a difference over the Monacor components. This has amounted to a serious uplift in mid range and treble quality that was way beyond my expectations. It is easier on the ear by far, and genuinely sounds really friggin' nice. After various mods to Duettas (both restored and Interstella) including different types of mid range/treble ribbons, and playing with inductor values and gauges in the past too, this is without doubt a genuine leap forward in mid range and treble quality to my ears.
There's a really nice synergy going on with these new components, and it shows just how good Apogee mid range and treble quality can be. The overly etched quality that was there when Marc was here (he described as overly digital but we're talking the same thing here I am sure) and in previous visits by Kedar is much reduced, but not so far that the speakers sound too soft. There's still sufficient bite to sound right when the material contains it.
I may try some
Jupiter copper foil in paper and wax caps later in place of the Jantzen Alumen Z-Caps. I'm not sure that the extra money on the Jupiters will work out as it may upset what seems to be an alarmingly good result.
The Jantzen cap recommendation came from HumbleHomemade Hi-Fi.
The best tube in the Lampizator now appears to be the KR PX4 for mid range and treble. That has really seriously surprised me too. I previously hadn't thought it to be that great in those regions in the sense that it seemed to get too harsh at times.
What a fine balance it is to get things right. Very fine indeed.