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Old 23rd February 2014, 12:29 PM   #1
beanbag is offline beanbag  United States
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Default Martin Logan crossover help

Hello folks,

I have a set of Martin Logan Vista speakers, and the crossover diagram looks like this:
(see attachment)

I have a MiniDSP and measurement mic, although so far I have only used them for low frequency room correction stuff.

My first question is "Is it worth it to bypass the passive xo's and do active bi-amping?"

For the woofer section, I have read that you pretty much bypass all the stuff and drive the woofer directly. And then use a 12dB/oct active xo on the signal to the amp. I guess the point is that without the inductor, you get a better damping factor on the woofer?

For the electrostat, I am not sure what to bypass, or if it is worth bypassing anything at all. For example, you probably want to leave the capacitors and resistors on the "red esl" line for high and low frequency protection. Then there is this stuff that parallels the two terminals. It seems like one of them puts a notch in the frequency response. So I guess the question is what to do about the ESL part in terms of active xo?

Also, would it help to use 24 db/oct on the active xo to limit the frequency range each driver has to play?
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Old 28th February 2014, 01:20 AM   #2
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Yes, it's "worth it" to remove the series inductance from the woofer xo. Start with the same 12dB/oct and XO frequency as the stock passive xo. Do you know the XO frequency?

Leave the ESL portion as-is for now. Baby steps!
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Old 28th February 2014, 09:30 AM   #3
beanbag is offline beanbag  United States
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450Hz, according to the manual.
For my miniDSP XO, I can choose LR, butterworth, etc or even biquad stuff. I'm not sure which one...
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Old 28th February 2014, 01:11 PM   #4
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I agree with Andersonix as the ESL side of the crossover has all of the necessary compensation components already built in to it.

Just be sure that you don't use a lower crossover frequency or else you will risk saturation of the transformers core.

jer
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Old 1st March 2014, 03:52 PM   #5
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You would be better off improving the crossover's passive components. You can upgrade the 12 and 18 uf caps ( C1,C2) in the high frequency section to better quality Polypropelene . I've used MIT PPFXS with good results. R1, R2, and R3 can be 100 watt TO 247 power film resistors (Caddock, Ohmite) but mounted on TO 247 heatsinks, the big 2 inch high 1/2 inch thick ones with a good Kerafoil insulator. I have modded ML Request, Cinema, CLX, and Stage with good results.

The problem is C3 - L1 is a notch filter not a crossover. You can easily get rid of the crossover digitaly, the notch filter is more difficult to duplicate, you have to measure it's response with and without the notch filter connected to understand what the notch filter is doing IE - Center frequency, depth, and filter Q.

The woofer crossover is 12 db/octave and the mid range is more complex, but seems to be a moddified 12/db/octave. You can try different slopes such as 12, 18, and 24 and see how they sound, most specifically how well the cell and woofer blend seemlessly... but the notch filter needs to be there too to get it right ....

Last edited by ticknpop; 1st March 2014 at 04:03 PM.
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Old 1st March 2014, 04:04 PM   #6
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Join Date: May 2005
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You would be better off improving the crossover's passive components. You can upgrade the 12 and 18 uf caps ( C1,C2) in the high frequency section to better quality Polypropelene . I've used MIT PPFXS with good results. R1, R2, and R3 can be 100 watt TO 247 power film resistors ( Caddock, Ohmite) but mounted on TO 247 heatsinks, the big 2 inch high 1/2 inch thick ones with a good Kerafoil insulator. I have modded ML Request, Cinema, CLX, and Stage with good results.

the problem is C3 - L1 is a notch filter not a crossover. you can easily get rid of the crossover digitaly , the notch filter is more difficult to duplicate, you either have to measure it's response with and with them to understand what the notch filter is doing IE - Center frequency, depth , and Filter Q
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Old 25th August 2015, 05:39 PM   #7
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Hi

Does anyone have a rest of Vista's shematics? I should includes esl-transformer and high voltage unit etc...


hifijussi@hotmail.com
Finland
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