Passive Crossover accepting 16 or 4 ohm load on highs

[Trainmj]

I'm building a high pack cab with one 12" mid-bass and two 1" 8 ohm compression drivers. I'm trying to find a passive xover that will let me use either a 16 ohm or 4 ohm load on the highs. Any help would be appreciated.

[billfitzmaurice]

It can't be done, passives must be configured to work with the load impedance, among other things.

[Chris Roemer]

The Fc of odd order XOs (like 1st or 3rd) will vary w/load, but even orders (like 2nd or 4th) have the Fc fixed by the component values.
What DOES change though (with different impedances) are the "Q"s of the filter rolloffs, which may or may not be acceptable to you.

[DrewsBrews]

I have used a DPDT switch and two different input connections to switch between two different circuits. In my case I was using a fullrange driver and switching between (A) A crossover circuit with tweeter, or (B) A response shaping circuit that just ran the driver fullrange by itself. But I imagine it could be adapted for your use. Two different highpass circuits connected to two separate output connections for 4ohm and 16ohm. The switch would connect the input to whichever highpass circuit is needed and totally isolate the unneeded circuit.

[DrewsBrews]

Yeah well, just trying to offer a potential solution to the question asked. It is up to them to decide if it is worth it.

[Trainmj]

I'm sorry I wasn't clear enough on what I'm looking for. The high on the xover can be 16 ohms. I'll just wire my compression drivers in series for 16 ohms. Forget 4 ohms. The only thing I see commercially available is for an 8 ohm driver but I want to run 2 Compression Drivers and I already have 8 ohm drivers. I don't want to have to buy 16 ohm drivers to wire in parallel.

[billfitzmaurice]

Commercial off the shelf crossovers typically come in 8 ohm only, and don't work very well. Roll your own, preferably either 2nd order LP/3rd order HP or 2nd order LP/4th order HP.

[DrewsBrews]

Ok so you didn't want the option to do either config in one circuit, just generally want a crossover for two CDs. I understand now.

I'd agree 16ohm would probably be the better choice as the CDs are typically much higher efficiency and that would naturally give a head start to reduce the output closer to the cone drivers. Even then they are probably still too much so could use a parallel resistor to bleed off power and bring the resulting nominal impedance back down (as seen by the amp/crossover). But it is all a guessing game unless you have measurements...

There aren't many premade options for passive crossovers because they are generally a poor choice. The passive components are reactive to the driver's impedance (which changes depending on frequency) so the same crossover can work very differently depending on the driver they are attached to. To properly design a passive crossover you would need to get the impedance plot and response graph of the drivers in the specific horns. Plug them into software and design the crossover from there to achieve the desired crossover point.

Would you have a setup for measuring and EQing at a venue? That might make things a little easier to just design a highpass with resistor padding for driver protection and some rough initial level matching. Then can shape the output response later. But you still want the drivers reasonably crossed over between each other so they aren't getting a bunch of phase cancellation due to them playing the same frequencies at similar levels.