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Re: Example please?

Breakup IS minimum-phase. It's a common misconception. It's possible to model the breakup down to the smallest detail and get accurate FR/phase response. I've done that with a 10" drivers modeled to every detail of breakup to 20K. Were the breakup not minimum-phase, the model would fail.

There were a number of detailed threads at the Mad board some time back. One of the posters showed the math derivation that was supporting confirmation of the empirical models.

There is nothing in breakup that prevents a driver from being minimum-phase. It is by nature minimum-phase. More evidence of this is in the Hilbert-Bode transform. A signal has to be minimum-phase to satisfy the requirements for the H-B transform. This is used by CAD software to generate the phase if measured phase is not available or not used. The H-B transform generated phase from the measured FR of all raw drivers, including the breakup area, shows a minimum-phase response.

There used to be a lot of questions about breakup and whether or not it was minimum-phase, but I've used CALSOD for many years and have always been able to model any driver's response and get perfect agreement between measured phase and the H-B generated minimum-phase after accounting for the excess-phase always present in measured phase.

There is an argument that can be made that the breakup and stop-band area prevent a number of true designs from being fully achieved for another reason. The is most true of anything that requires a first order driver response. No driver can ever produce a first order response deep into the stop-band. Drivers are second order passband by nature. This means that at some point, no matter how detailed the crossover, the driver will ultimately revert to 2nd or even higher if a crossover is included. However, this can easily be put into the noise floor making it inconsequential.

That's what one does with breakup. All drivers breakup, not just hard diaphragms. This is WRT to the FR.

WRT to driver excursion, distortion and breakup, all drivers exhibit this. By that definition, no driver could be considered minimum-phase, but that point is moot as the breakup is itself a minimum-phase phenomenon within a driver. The

Now motor distortion is another issue. All drivers also exhibit this and it is non-linear. It doesn't matter what the diaphragm material is made of, although it can exacerbate the issue. Hard coned drivers with their exaggerated breakup certain make its control more problematic.

What is important in this case is to cross the driver at a point, even first order, such that the breakup is well down into the stop-band. I think that Linkwitz discusses this at his site, though his designs are definitely not first order. It's an issue for any design. It certainly limits the usage of hard cones (I'm not a fan of them myself, I like doped paper mostly), but it does not preclude them.

So in the end it comes down to what compromises do you want to accept? All systems are simply different compromises in design. When a driver's Xmax is reached, distortion is going to increase. But this is true of every design.

A first order system has the most compromises, except that there is one that few other systems compromise more. That's the ability to closely reproduce a square wave, the most difficult signal to reproduce (other than a true infinite impulse). With all of its compromises, a first order system will still, even with the breakup, generally reproduce a square wave more faithfully than other designs, the exception being the few higher order crossovers that are also transient-perfect.

Of course, this opens up the whole other discussion as to the audible benefits of any transient-perfect design vs. non-TP designs.

dlr

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