Mini dsp reverse engineering to make passive crossover

[charlie2]

I would like to build a design of speakers

Eg

Bass /mid/tweet

But using mini dsp and rew for measurements

Be it a a synergy or spendor bc1 design as examples

Using multiple amps of same source ie QSC 1450 rmx bi-ampping or trip-amping initially

But then can I make a passive crossover to fit and forget.

Running from a single stereo amp

How hard is it to do.

Cheers

 

[JShadzi]

I am just now finalizing a set of speakers using a similar process, miniDSP is invaluable for this. I initially measured FR of the raw drivers using nearfield measurements, then modeled a cross over, then began tweaking values until I got the desired FR and sound.

Here is what I started with

And ended up with

Final XO design

MiniDSP was invaluable for testing XO points, lpads and even the effects of Zobel networks. Also testing the effect of different FR on sound quality before making changes to the XO point.

I'll post a detailed wrote up in the next week or two but feel free to ask away.


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[AllenB]

I would measure the amp outputs (or line level response) directly to get the transfer functions. You can then invert these in a crossover simulator, and use measured driver impedance data to aim for a flat response.

 

[Lojzek]

But then can I make a passive crossover to fit and forget.
Running from a single stereo amp. How hard is it to do.
Cheers

It's not hard to do anything if you know how to. I don't see
why would one go through the trouble of getting a dsp
solution and then try to do the same passively. Passive
speakers are trickier to deal with because you have to
work hard to find out a working filter that doesn't involve
an insane amount of parts. Secondly when you cross drivers
over at lower frequencies, the capacitive reactance part of the
woofer is causing spl differences so if this bothers you, then
you should add impedance flattening filters which adds to the
overall costs. My favorite design approach is passive filters
with woofer XO point pushed high enough to escape
the region I don't like without making significant compromises.

A good filter design is a thing of good practice and abbility to
think straight.

 

[critofur]

LspCAD has a crossover simulator which is great for such testing, because at the end, you have your passive crossover design.

You can make changes to a passive crossover design and listen to how it will sound via simulation.

 

[JShadzi]

It's not hard to do anything if you know how to. I don't see
why would one go through the trouble of getting a dsp
solution and then try to do the same passively.

I can't imagine going out and buying a DSP simply for tuning one speaker, but if you're going to use it as a long term tuning tool then it's definitely worthwhile.

In my case I have a 4x10 already and a stack of amps


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