Active - How to Simulate Phase Matching

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eriksquires

eriksquires

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Joined 2013
#1
Hi Everyone,

I just realized something. In the passive world there are several tools that help us simulate the crossovers and driver phase matching. I'm thinking of course of XSim and the like.

Like, I can look at this graph and compare the phase matching:

LM-1_FR.jpg


and I can adjust my crossover until the phase angles match up. How do you do this in the DSP world? Is this something I should do in OmniMic or REW instead?

For instance, on a flat baffle, 2 driver speaker. I'd like to do an active 2nd order symmetrical crossover. I now have control over driver delay in addition to crossover slopes.

How do I know that this inter-driver alignment is optimal without going back and forth inverting the tweeter? 🙂

Best,


Erik
 
#2
eriksquires said:
I can adjust my crossover until the phase angles match up. How do you do this in the DSP world?
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There is no difference in the actual design process unless you go the brute force FIR approach (measure, invert and convolve with target --> done... just that most often it does not work to cut corners this way).

Define target responses (the most important aspect).
Stack filters and "bend" filter parameters until you driver gets where you want it to be, both phase and magnitude.
Then synthesize these filters into analog circuits or a set of digital filter coefficients.
It all depends on what software tool you use. I'm a big fan of LSPcad, notably the pro version with real time emulator.
 
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#3
I use Charlie Laub's ACD, Active Crossover Designer, to create/define IIR filters with output that can be cut and pasted into MiniDSP. It has an extension for phase tracking, another spreadsheet that plots both drivers phases and the relative phase angle.
 
#8
eriksquires said:
So with XSim I can adjust my crossover components and get instant phase/amplitude simulations.

Does ACD or LSPcad do the same??
Click to expand...
For LSPcad: Yes. Change of any parameter or component value is very convenient and the effect is always displayed immediately, plus the changes can be listened to in real-time in the pro version which of course is the key feature. Rapid prototyping at its best.
There is sort of a clone of LSPcad which is quite good and freeware, I just don't happen to remember its name right now. Written by some guy from Finland I seem to remember... gotta check my notes...
 
#12
nc535 said:
I use Charlie Laub's ACD, Active Crossover Designer, to create/define IIR filters with output that can be cut and pasted into MiniDSP. It has an extension for phase tracking, another spreadsheet that plots both drivers phases and the relative phase angle.
Click to expand...
DITTO ACD. It also shows group delay and since it is excel you can customise it if you want. I added an absolute magnitude difference to the relative phase angle sheet like HERE.
 
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