Hi, I think that work practice has the best chance of making both methods give the same results.

As both key on the first all important step of flattening each driver's mag and phase response with minimum phase filters.

And I agree strongly that delays should be based on acoustic offsets.

I also agree if the correct inverse all-pass filters are added for the full set of IIR crossovers, there would be no need for cascading xovers.

Just made a quick electrical 1D sim using IIR xovers with inverse all-pass on each.

Uses the same xover freqs as my previous sim...100, 280, 750, & 3200Hz. But xovers are LR 24 dB/oct rather than previous 96 dB/oct.

So the sub driver (red) with a 100Hz lp gets a 100Hz inv all pass.

The low driver (dark green) gets 100Hz hp w/ 100Hz inv all pass, and 280hz lp w/280 Inv all-pass.

Ditto process for remaining drivers...each hp or low pass gets inv allpass aplied. (all 2nd order Q=0.707)

Here's the individual sections mag and phase.

And summed mag and phase...the black line across the top.

Each driver essentially has a linear phase xover for itself, just as if linear-phase xovers were being used directly.

Perfect as expected.

View attachment 365971
Now, all the xover hpf's and lpf's are turned off....and just the phase of inv allpass and their summation is left to see.

Nothing but inv allpass, so no magnitude involved.

Each of the sections inv all pass can be seen, along with the wavy black line which is their electrical summation....

The black line is what the FIR file doing the global IIR xover phase linearization will need to replicate.

View attachment 365973
Ok, so what's the point of all this.....

Here's my take...this example is as easy as it gets...simple LR24's that are easily, perfectly matched by a 2nd order inv allpass.

I've been playing around trying to use the technique on higher order xovers, and can't so far.

I can't get the inv allpass's to match up and flatten phase.

Michael, is that something you can do? With Camillia maybe? Directly put several higher order inv all-pass into one FIR file?

I don't fool with IIR much other than system high-pass as discussed.

And really because, it seems kinda like beating my head against the wall, to use IIR xovers and inv allpass, than simply using complementary linear phase xovers to begin with....

All to get the FIR into just one file ???

If I am already multiway active, I already have the channel processing and amps in place. I'm using FIR. Why make it more complicated by not using multi-channel FIR?

I don't get it Lol