Hello all. I've got a slightly unusual situation but it's not too complicated, and I'd like to ask for some input about a passive crossover I'm going to need. Here's the details:
It's a horn-on-box system, right now the horn is a Le Cleac'h (Martin Seddon Azura) 425, playing from 600hz up. The crossover is an active Sublime 241. Of course, this requires two amps, and the horn is driven by a triode strapped EL34 PP tubie and I love the sound. The 15" woofers are driven by E3 class D diy, also great for the application. Here's where it gets slightly interesting...
I'm going to add a little Le Cleac'h to take up the "tweeter" duties, and will cross somewhere between 2k and 4k depending on how the impedances play out. But I don't want a third amp, so I'm going to divide the two horns with a passive network. I want to keep it as simple as possible, and if things measure smoothly enough I'd like to use 2nd order, but confused about whether to use Butterworth or LR. If I read the crossover chapter of LDC one more time I think I'll hemorrhage, I understand it for the most part but it's still not clear what the differences would be except on the screen. Phase isn't such a big deal because the horns are independent on the z axis so offset is easy to adjust.
Does anyone have any advice on this?
Thank you,
Bryan
It's a horn-on-box system, right now the horn is a Le Cleac'h (Martin Seddon Azura) 425, playing from 600hz up. The crossover is an active Sublime 241. Of course, this requires two amps, and the horn is driven by a triode strapped EL34 PP tubie and I love the sound. The 15" woofers are driven by E3 class D diy, also great for the application. Here's where it gets slightly interesting...
I'm going to add a little Le Cleac'h to take up the "tweeter" duties, and will cross somewhere between 2k and 4k depending on how the impedances play out. But I don't want a third amp, so I'm going to divide the two horns with a passive network. I want to keep it as simple as possible, and if things measure smoothly enough I'd like to use 2nd order, but confused about whether to use Butterworth or LR. If I read the crossover chapter of LDC one more time I think I'll hemorrhage, I understand it for the most part but it's still not clear what the differences would be except on the screen. Phase isn't such a big deal because the horns are independent on the z axis so offset is easy to adjust.
Does anyone have any advice on this?
Thank you,
Bryan
There's not going to be a straight answer to your question.
LeCleach horns have a constantly varying directivity. This means that two of them of different sizes aren't going to have a frequency where they match. You need to learn enough about the situation with polar measurements and simulation, or something equivalent, and decide as you go along.
LeCleach horns have a constantly varying directivity. This means that two of them of different sizes aren't going to have a frequency where they match. You need to learn enough about the situation with polar measurements and simulation, or something equivalent, and decide as you go along.
Thanks Allen I hadn’t considered directivity, just basically was assuming the 425 would be getting narrower at 3k, and the little 1100 would be getting wider and was hoping they’d cross well! Definitely not scientific, I’ll see if I can find some polar plots.
Just wondering, why wouldn’t they match anywhere? Isn’t it possible they’re close in directivity at some point?
Just wondering, why wouldn’t they match anywhere? Isn’t it possible they’re close in directivity at some point?
I think I understand. I'll go back to LDC and re-read with this in mind, maybe I missed it because I didn't understand what this meant, but it seems like this would mean the BW has generally broader directivity whereas the LR loses power as we go farther off axis, is this correct? And thanks for the graph above, even interpolating an 1100 in there, I see what you're saying.
Essentially yes, but if you look at a plot of lobing you'll see that it isn't as neat as simply changing the further you go off axis. It's more a case of going in and out as you go higher or lower.. however generally speaking it's the same thing.
Got it, I'm still trying to find some lobing or polars but looks like as usual this is going to take some time, back out into the driveway with the 6 foot ladder......I appreciate your input Allen, this stuff is infinitely complex and it's helpful to get the direct info from more experienced people like you. This is why I presented the question, the "I don't know what I don't know" stuff.