ML Vista Crossover Bypass

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InterMechanico

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Hi-O. Does anyone know if there is anything special I need to do when bypassing the crossover network for the panel? Should I install a resistor in series in that circuit to lighten the load on the amplifier module? I'm using a pair of MiniDSP PWR-ICE 250s for amplification. I had started off by only going active with the woofer section, but I experienced such a profound increase in performance that I've decided to go all the way with the project.

Thanks, in advance.

Julian
 
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Music sense circuit could potentially be problematic......

Out of curiosity, why would you want to bypass panel xover? It's made out of decent components.
 
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Music sense circuit could potentially be problematic......

Out of curiosity, why would you want to bypass panel xover? It's made out of decent components.

You're right. I was playing around in there, and everything looked to be top quality. However, when I bypassed the woofers crossover, used the Parametric EQs on the MiniDSP PWR-ICE 250 to correct for room issues, the result was, well, astonishing. I have done a bunch of measurements in my room, and have so far been able to get everything up to 500 hz to within 3-5 db @ 90 db spl. I'm still working on that. Above that range is still out of whack, and . I know it sounds silly, but I kind of feel like I've stumbled onto the difference between the $4000.00 ML's and the $10,000.00 models. Besides, I have it on very good authority (RUR) that I'll experience much greater clarity in the higher frequencies by eliminating the other half of the crossover. Given my experience thus far, I'd certainly agree. I have pictures of the crossover if you'd like to see them.
 
Hi-O. Does anyone know if there is anything special I need to do when bypassing the crossover network for the panel? Should I install a resistor in parallel on that circuit to lighten the load on the amplifier module? I'm using a pair of MiniDSP PWR-ICE 250s for amplification. I had started off by only going active with the woofer section, but I experienced such a profound increase in performance that I've decided to go all the way with the project.

Thanks, in advance.

Julian

Julian, your question is unclear. Are you asking if you should install a resistor across the output terminals of the amplifier module? If you did that, you would not lighten the load on the amplifier module; you would increase the load as the amplifier would be seeing a lower impedance.
 
Music sense circuit could potentially be problematic......

Out of curiosity, why would you want to bypass panel xover? It's made out of decent components.


Active is better than passive. With active you gain lower distortion due to optimizing amplified bandwidth by limiting the frequencies the amp amplifies and it is also more efficient in turn, the amp now has direct control over the driver increasing the damping factor, and now the panel is no longer a slave to the bass driver that is in a passive design when the woofer distorts it will force the tweeter (in this case the panel) to distort along with it when otherwise it wouldn't. Passive bi-amping only gains the final point, active gives all 3.

I'd be interested in seeing how you achieve this. Once the warranty runs out on my ML EM ESL's I plan on doing the same thing! Active rules. \m/
 
Yes please.


Love to know how you go. Have you sought input from JonFo? He'd likely have a lot of assistance to offer you.

I haven't bothered him directly....yet. There are few others here who may have the relevant information as well. I'm not in a huge rush, so I'll wait and see if anyone chimes in. I'll do a small write up on the project and the results (my impressions) when it's all complete. Here are some pictures of the crossover :D

IMG_20140920_095154.jpgIMG_20140920_095218.jpgIMG_20140920_095234.jpgIMG_20140920_095255.jpg
 
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An observation:

I would like to note that when I examined the black (negative) conductor that powers the woofer directly, I saw that the copper strands were quite oxidized. The speakers is only 3 years old or so. you can see the oxidization in the picture below. I will be replacing the conductors at a later date with (suggestions?).

IMG_20140920_101117.jpgIMG_20140920_095323.jpgIMG_20140920_095312.jpgIMG_20140920_094200.jpgIMG_20140920_094232.jpg
 
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An observation:

I would like to note that when I examined the black (negative) conductor that powers the woofer directly, I saw that the copper strands were quite oxidized. The speakers is only 3 years old or so. you can see the oxidization in the picture below. I will be replacing the conductors at a later date with (suggestions?).
With any good quality copper wire of the correct gauge, Julian. Solder the joint and then don't worry about surface oxidation.
 
With any good quality copper wire of the correct gauge, Julian. Solder the joint and then don't worry about surface oxidation.

Okie Doke. I have a bunch of good quality 10 awg with silicone insulation. I'll use that. Thanks, Ken. I appreciate your help.
 
I'm guessing the central resistor labeled "(ph)20WR50J" (making it a 20W 0.5 Ohm resistor) is in series with the audio step up transformer and thus should be left in circuit to keep the amplifier happy over 10kHz when you remove the passive HP crossover and EQ.

The series inductor in any passive bass xo is low-hanging fruit easily reached by going active xo there. But for the ESL panel there is not the same easy pickings to be had going from passive to active, so you might want to rein in some of your expectations (although it's still worthwhile). Looking forward to your results!
 
What kind of frequency response do you get if you just run the panel full range with nothing to the woofer? I've always been curious just how well they do or don't do and how low they can go before it's unacceptable.

It has always felt like martin logan arbitrarily raises the crossover the cheaper down the line you go so that you get more panel sound the more you pay; but I question if it's really necessary.

/edit: this is off topic. I'll make a new topic with the question
 
I'm guessing the central resistor labeled "(ph)20WR50J" (making it a 20W 0.5 Ohm resistor) is in series with the audio step up transformer and thus should be left in circuit to keep the amplifier happy over 10kHz when you remove the passive HP crossover and EQ.

The series inductor in any passive bass xo is low-hanging fruit easily reached by going active xo there. But for the ESL panel there is not the same easy pickings to be had going from passive to active, so you might want to rein in some of your expectations (although it's still worthwhile). Looking forward to your results!

Thank you for the insight. Just what I was waiting for. I'm going to order a few different resistors on-line, then I'll pry ;) them open again. For the sake of not wrecking otherwise good crossovers, I think I'll just make two new rear panels with ports and binding posts. Maybe out of 3/4" aluminum plate. Stay tuned!
 
I'm happy to help!

If you can find a schematic (or figure it out yourself) then we can prob strategize some way of bypassing the original xo and eq components, without risk of wrecking them. The PCB looks pretty stout, so it should survive a little bit of unsoldering, if your iron is large enough.
 
I'm happy to help!

If you can find a schematic (or figure it out yourself) then we can prob strategize some way of bypassing the original xo and eq components, without risk of wrecking them. The PCB looks pretty stout, so it should survive a little bit of unsoldering, if your iron is large enough.

I think I could map it out easily enough; all the circuitry is visible. I can remove the board from the rear panel of the woofer enclosure, and add a series resistor very easily. I had a look at Madisounds' website for a few different Mundorf supreme (decent quality?) resistors, in a 20 watt rating, but they only go as low as 1 ohm. Do you think that'll be ok? It certainly won't hurt anything, just rob power from the circuit. They're not terribly expensive anyhow.
 
Julian, your question is unclear. Are you asking if you should install a resistor across the output terminals of the amplifier module? If you did that, you would not lighten the load on the amplifier module; you would increase the load as the amplifier would be seeing a lower impedance.

Sorry, Bernard, I missed your post. You're right, of course. I meant "add in series" but said " add in parallel". I recall a thread (but can not locate it) in which the crossover in the ReQuest model was being discussed, namely its' elimination in favor of active crossovers. A contributor had eluded to placing a resistor in series with the panel circuit (main) to lighten the load on the amplifier.
 

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