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JR. wrote:Is your motional feedback bass driver operated full range? Or with a crossover? If there is a crossover you could consider applying the limiting to just the low bass bandpass.
Thanks for your reply JR
Most of your Q's will be answered by the circuit above, it's a 2 way system with a 4th order LR filter in a Sallen Key setup. The subsonic filter is build around a modified substractive filter, I've added an allpass filter in the substractive branch - IC2A - to mirror the phase shift from the primary 70hz lpf - IC1B - so the lpf output at IC2B should display the same 12db/oct slope as the hpf output at IC1B.
JR. wrote: if the motional feedback delivers a 100% servo of the bass driver cone motion, excursion limiting will be simpler.
Tried that exactly, using the MFB signal as input for the RMS detector - output IC5A - but found this to work less optimal then feedforwarding the IC1B output, rationale is that the latter allows the limiter to act before the signal actually reaches the driver.
JR. wrote:There are professional speaker management DSP systems that already deal with some of these considerations, for convention drivers.
Correct, I understand that
Klippel is working on a single chip correction chip - sounds promising.
JR. wrote:PS: While it's true that the derived dividing network in the THAT app note sums to unity when summed at 100%, in use the limited side will be level reduced so not sum perfectly. FWIW
Actually I didn't come up with the allpass trick, just borrowed it from
Douglas Self his filter bible
mediatechnology wrote:Wow Chris. What a beautiful piece of work. Nice build!
Like
yours too, very neat !!!
mediatechnology wrote:I'm curious about the Motional Feedback aspect since I recently posted about my Panasonic MF-800.
Cool ! please check out
this doc ... 1968. I was age 11 when MFB bit me - sounds like we have something in common
mediatechnology wrote:I think generally you'll find a NLC will reduce LF distortion from detector ripple control modulation.
Definitely worth a try then, thanks.
ricardo wrote:horny handed speaker designers.
ricardo wrote:The threshold & frequency really need to be adjusted to fit the speaker.
Right now I'm adjusting the 4315 loop so it limits excursion @ 30 hz and 35 watts, the graphs below are taken from a faital-pro 5 inch driver, this is what the FR looks like without MFB:
And with correction on, the little bump @ 70hz was gone after I increased R16 from 4702 to 8202
ricardo wrote:Waz is das? (NLC)
non linear capacitor - capacitance varies with freq.
love to talk but have to run, sunday, mothersday, you know