vinylnvalves wrote: ↑Mon Feb 22, 2021 8:47 am
Mark.. need to work back, what have you changed since the horns were sounding good? We’re you previously running then with passive crossovers? As you know the reflected loaded back thought the OPT’s changes the working line.
In the past I would generally have the ribbon tweeter on there as well. On paper it shouldn't affect how the horn sounds lower down, but maybe the extra finesse and harmonics higher up are masking the colouration.
It should be a good load line - I haven't applied any passive crossover to the horn - just run it open, moved from the chip amp ( test ) to the 45 amp ( listening ) , which is set up for 8 ohms.
The colouration is probably just because of running it open to the lower cutoff - but I hadn't noticed it as much before.
The 45 amp does have a high-pass of sorts - around -3dB at 175Hz due to the special output transformers - that will have a small effect at 500Hz, but that should be helpful.
I am also tempted to bring the Azurahorns down and try one with the other drive unit. I know they are a bit better at the lower end of the range, although I found them harsh if run up to 12 or 13kHz. I never tried a low-pass on them when combined with the ribbon. That might work - something around 4 or 5kHz.
"Once you find out ... the Circumstances ; then you can go out"