Can I drive a pair of CD horns from one side of PV-4C

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Can I drive a pair of CD horns from one side of PV-4C

Post by soccerman58 » Thu Dec 17, 2020 2:43 pm

I am building a little mono PA with a JBL sub being driven by a bridged Crest amp, 1 15" mid per side being driven by a bridged Crown and 1 CD horn per side.
Crossover duties by a Rane 3-way Mono crossover at 120 Hz and 1800 Hz.

I have a pair of 2-way seakers with a BW 15 and an unknown horn. I say it's an unknown horn because they have the original JBL horns but there is a generic diaphragm on both of them - so I can't get any Thiele-Small parameters for the horn. However, the box used to be a pair of JBL MR series 2-ways rated at 250 watts. So I think we are safe to assume that the replacement diaphragm will handle however many volts it would see if the original JBL enclosure was being driven to rated RMS voltage (250 Watts).
The BWs will be driven by a bridged Crown amp with a maximum of about 300 watts to each speaker. The crossover uses 24 dB per octave slopes, so the horns are going to be much more protected at the crossover point (1800 Hz) than with a passive 12 dB crossover.

I have no idea what the impedance of the 2 horns would be at the crossover point given that impedance rises with frequency, but I need to figure out how much power I need for the 2 horns. I measured the electrical resistance of the horns at around 5.2 Ohms each, but I was icily reminded on another forum that electrical resistance is not the same as impedance. I was planning on using one side of a PV-4C, which is 200 Watts at 4 Ohms and only 120 watts at 8 Ohms, but I have no idea about triamping a system in this way. I do know that horns are much more efficient than speakers of course.

I can't really see it being necessary, but I do have a spare air of Sonic horns (also blown) that I could fix on top of the 2-ways to help out with the highs. But that could be problematic, because they have a deeper and wider horn lens than the CD horns so that might lead to problems with time alignment (although the Sonic horn is only maybe 4 inches behind the CD horn) or comb filtering or other stuff I have no understanding of.

FWIW, the diaphragms are new and with fresh ferrofluid in em.
Opinions about the horn amp situation please?
Thanks very much

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