Martin Logan SL-2 Panels....help! - diyAudio
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Old 19th January 2008, 04:38 AM   #1
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Default Martin Logan SL-2 Panels....help!

All,

I have an opportunity (nice friend!) to get a pair of Martin Logan SL-2 panels, but without power supplies, etc.

I intend to build the power supply/audio transformer subsystem to match the SL-2 panels. Can anyone advise what voltage these panels might take? (I haven't had the opportunity to measure the spacing between the stators yet). In addition, I will be driving these amp in a bi-amp configuration (transmission line 15" woofers yet to be built), using one Onkyo Integra solid state M-506 amps (160 watts/channel) per speaker. Can you advise of a good audio transformer (turns ratio, power capacity) that would be acceptable? I'm planning to build a low-pass/high-pass filter prior to the Onkyo power amp, and I'm guessing a low pass, 250-hz filter (with 6 db?) roll-off would work with this configuration.

Sorry for these (probably "newbie" questions), but I am an ESL newbie! LOL..... any help/comments would be appreciated.

Ken
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Old 19th January 2008, 06:15 PM   #2
AVWERK is offline AVWERK  United States
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Keep your eye on Ebay as sometimes the complete boards come up. also check out the ML forum. A post there might give you what you need.

Also, are you sure the panels are good ?

Regards
David
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Old 20th January 2008, 09:30 AM   #3
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David,

I was able to check them out in the SL-2 enclosures. They were clean, with no signs of arcing or film damage. THe also sounded excellent with several music sources. Volume was equal from both, as far as my ear could tell. Dispersion patterns were equal. I also ran a sweep sine wave against each, through the amps, 200 hz-18 kHz, and there were no unexpected sounds, buzzes, shakes, rattles, resonances, etc.

I'm getting them for free. They're about three years old, and come out of a home with a good HVAC system, and no pets. I friend has top-line components (Krell, ec) and he takes good care of his audio components. If worse comes to worse, I'll build up the filters, power supply, and transformers, and if the SL-2 panels don't pan out, I'll break out the perf aluminum, mylar and graphite, and whip up some new ones. (I've built curved 4' panels before--just couldn't resist the price ($0) of these ML ones.....

Ken
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Old 21st January 2008, 02:32 PM   #4
Calvin is online now Calvin  Germany
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Hi,

I donīt know the SL-2, but beeing a ML it will probabely have a d/s of ~1.5mm. You can drive such a d/s with trannies ranging from 1:50 up to 1:75, with the larger values for smaller panels and the lower values for larger panels. I have made good experiences with standard power toroids, which give much better results than the older trannies ML used (those were just cheap and crappy). Still though You should know that a simple highpass doesnīt work with an ESL-panel of ML-type.
You need a high pass with high Q, together with a high-Q-Notch (placed on the panelīs Fs) and probabely some more equing around 2kHz and 10-20kHz.

jauu
Calvin
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Old 22nd January 2008, 03:58 AM   #5
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Calvin,

Guten tag! Thanks for the info. I have a dBx 1/3-octave equalizer (31 settings per channel) that I was going to use for overall equalization in my system. Each equalizer range gives me +/12 dB range. I had planned/hoped I would be able to equalize the panel's response over their operating range with this equalizer. I'm not certain it will be sufficient to "notch-out" the fs resonance of the panel; I thought I would try this first, and if it was not sufficent, I would try a higer-Q filter in the transformer output.

I have not constructed my ESL yet (power supply and transformers still pending....), so I have not been able to try to tune the panels with my equalizer. Do you think the 1/3-octive, with a -12 dB cut, be sufficient to overcome the fs peak?

Ken
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Old 25th January 2008, 01:54 PM   #6
JonFo is offline JonFo  United States
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Having done several ML-based customizations, including totally replacing the crossovers in SL3’s and Monoliths, I can tell you, the graphic EQ you have will not do it.

You need something like the DBX DriveRack 260 speaker processor to do the job right.

Read up on my custom center channel, featuring a totally reconstructed SL3 electronics and front ended by a DriveRack.
http://www.martinloganowners.com/~td...ead.php?t=2018
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Old 27th January 2008, 09:28 AM   #7
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Jonathan,

Thanks for the posting. I did discover your custom center channel construction thread about two nights ago, and I was very impressed--gave me some good insights.

I'm using a dbx Driverack 4800 on my home theater system, so I'm familiar with it's capabilities. I probably should have mentioned in my earlier post that I freed up a raft of other dbx components when I instaled the Driverack and theater system. I still have the 2231, 31 Band Eq; a 120-X-DX Subharmonic Synthesizer, a 3BX-DS Dynamic Range Controller, and 234XL Crossover. I hope to reuse these components with my "rehosted" Sequel panels. I also have a good collection of audio test equipment (lab white noise generators, audio sweep generators, tracking spectrum analyzers, data loggers, etc) that I will use to tune the systems once I can get the ESL panels fired up. If I have to build a suitable notch filer to tame the Fs of the ESLs, I should be able to build a variable-Q, variable-notch frequency active filter to do so. I realize this is a "knob and LED happy" collection of components, but I'm building this system for my study, and hope to reuse what I have. If, all told, I'm not content, I probably will opt for another Driverack for this smaller system.

Again, congrats on your center channel construction--very impressive!

Ken
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Old 27th January 2008, 04:01 PM   #8
JonFo is offline JonFo  United States
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Hi Ken,

Thanks for the feedback on the Center build, it sure was fun, and man does it work like a charm.

I see, so it's all about reuse. While the 234 crossover should do fine, I still wonder if the 31 band give you the fine enough grained control. But as you note, with the tools you have, you should be able tell if it's doing the right things or not.

As a DriveRack user, I'm sure you understand how one gets spoiled pretty quickly by the level of control they provide.

I'm about to get a DriveRack 4820 (no need for on-unit UI) to replace the DR 260's I use across the front. I'll re-use one of the DR's on the rear (and retire the DCX2496).


Let us know how sourcing the parts for the panel electronics goes.
I have a couple of spare Monolith and Sequel panels lying around and I'm getting ideas
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Old 27th January 2008, 04:57 PM   #9
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Eeeerrrr, well. ya know, Jonathan..... if you don't have an immediate and compelling need for those "surplus" Sequel panels, let me know.... a man can never have enough audio projects....(!).

In the summertime, I tend to focus on auto (not audio) construction, restoring Jaguars (XK-Es) and tuning and drving a vintage McLaren Mk 8 Can Am car I race (hence my screen name).

But during the winter, I turn to (warmer) audio construction projects inside the house. So..... we're expecting a long winter here--and I could find good use for those Sequel panels of yours!

Ken

Again, thanks for the info exchange......
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Old 10th February 2008, 09:27 PM   #10
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Jonathan (if you're out there......)

I've been much impressed with your center channel design using a ML Sequel panel. I'm now considering cloning your design for a contentional stereo (Left, Right channel) listening cove in my study.

Your thoughts--would you consider such a configuration (ie., two of your "center channel" systems) for stereo audiphile use? Good idea, or not?

ALsol the Adire Extremis is no longer available. I can get Mpyre 65M midwoofers, but they have a considerably higher Fs than the Extremis 6.8. (37 v. 25 Hz, respectively). They also have a lower Xmax, and higher Vas (25 v. 11). Your thoughts--if I use two 15" transmission line subs with this configuration, do you think I'd still have a satisfactory/successful speaker selection? I'm thinking more and more about going with another Driverack to tune this system, should I go this route......

Thanks,

Ken
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