bypass crossovers, run panel full range - what frequency response do you get?

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akm3

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I've always thought Martin Logan was very arbitrary in their panel crossovers; the more you pay, the lower they'll let the panel play. I've always wondered if it's necessary and how well or poorly the panels actually perform on their own.

Has anyone taken something like, say a Vista, and eliminated the crossovers, and ran full range on just the panel (and then took measurements?)

How low could it actually play? Would this be bad for the panel and/or amplifier driving it?
 
Broadly speaking, any ESL panel has a main resonance frequency, below which it makes excessive distortion. Also the audio step-up transformer needs to be very good (expensive) to play low frequencies. So it's a good compromise allround to cut off the ESL somewhere above its resonance and pass the bass off to a cone woofer.
 
Plus, the ESL panel's inherent dipole cancellation at lower frequencies makes producing bass an uphill battle...
 
Yes acoustic cancellation and transformer saturation are the issues. Make sure to use proper high pass filter (xover frequency depends on panel properties) to avoid problems and ensure sufficient sound quality.

Passive xover likely has some kind of corrections for resonance and/or acoustic cancellation so you will need to implement those in your parametric eq as well high pass filter.
 
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It should be fairly easy to measure the performance of the existing, passive high-pass for the ESL panel down to, say, 2-3 octaves below notional Xover and then to duplicate this, if and as desired, using the active xover DSP. Disconnect the woofer and measure anechoic (as in outdoors) @ a meter or so.

Also, I'm unclear as to what resonances we're worried about. The only ones I know of are those at the high frequencies, as reported in the various Stereophile ML reviews. But Jonathan's the wizard at this, not me. I'll see if I can't encourage him to lay some wisdom on us all.
 
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I've always thought Martin Logan was very arbitrary in their panel crossovers; the more you pay, the lower they'll let the panel play. I've always wondered if it's necessary and how well or poorly the panels actually perform on their own.

In a free market it is unlikely that Martin Logan could hold back and go "ca-ching" by letting a little more bass out for more bucks. With the CLX they attempted to make a full range electrostatic in a two panel speaker. They were only able to get down to 56 Hz at -3dB. At least the CLX got comfortably into the range for adding a sub or 2 or more. I will second Ken's plea for some input from Jonathan. BTW Ken (RUR) is one of this sites most knowledgeable contributors on bass. When he speaks bass, I listen.

Gary
 
Hola Gary...we have to think that the CLXs, as it is a model that needs a sub(s). On the other hand, the value 56Hz, it is just a merely figured number, because you still have 40Hz info at your CLXs. If you play with the back wall, you even can get outstanding deeper bass notes. But, we must think that the CLXs are designed in mind to have one or two subs, as a part of the whole speaker. You can buy the CLXs alone, but the truth is that they do lack the organ bass notes, and these bass notes are only archived with a sub(s). I have musician(s) friend(s) that had said to me, that they do prefer the CLXs without the sub, unless you are going to listen big orchestra heavy bass content or instruments that have very strong deep notes, like a big drum or similar. My liking is to have the stage wide, with the sense of good 3D, and clean...too much bass energy messes with the stage and makes it to have the bass player next to your seat, and not at the stage. Because our ears are not too good for bass notes, we usually use more energy bass of what the instrument(s) can produce. Dynamics are other thing. As I always say, sound it is a matter of liking. And what I do like, not necessary must be your liking. I do respect all the member(s) who like this bass energy of course. It is our privilege to play our system the way that we like it. And yes, we are fortunate to have very dedicated members with outstanding knowledge and great ears, and always are sharing it with us. People, trust your ears and try to listen unplugged musical instruments on the stage...and you will realize that we still are in dippers regarding sound quality. The good think, we are getting closer every day. Regards from Costa Rica!
 
Roberto, good to hear from you. I agree with everything you said. I use 4 subs to even out the bass in my room. And I agree with your musician friends sometimes it is best with the subs off and let the CLX's sing a cappella.

Are you coming to CES this year? If so let me buy you a beer.
 
Yes, four subs will make a big huge stage. It is not for the quantity of bass, but the quality! I know you Gary, always seeking for the best!...

I am doing my best for the Show...business is very slow here in CR...but I hope to see you too!...and of course I am already tasting that beer, hahaha, the next one is on me! Warmest regards my dear friend!
 
Tosh, MPS and RUR have all given great responses, so I'll only add a bit here to share what I documented when building out my SL3XC center.

I measured (indoors at 2m) the raw panel with zero crossover, and also tested a 1ohm in line resistance, which as you can see from the dark blue trace, significantly lowered the HF output.

attachment.php


Note that the response drops like a rock below 200Hz, and I can vouch for the fact that it loses headroom as well.
 
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Ken, regarding resonances, I don't have the plot accessible right now, but I recall modeling the SL3 panel at different levels and the distortion in the low end (<220Hz) rose significantly with power. I have a goal of 105dB Spl with <1% THD, and the only way that panel would do that was to crossover at 400Hz. If you limited your max or were willing to live with more distortion on peaks, then it works fairly well down to 315Hz, but I'd never go lower.

The panels also have other resonances at different frequencies (and that's why the spars are there to mitigate them), but none as bad as the low end when pushed.
 
Hi JonFo!

Always pleased to hear about your experiences!
Your goal of 105dB, is that at the listening postion?
In your plot in post 10, that was through the stock audio step-up transformer, right? Have you done have a frequency response / distortion test for the SL3 transformer alone? It is my sense that it is a very good quality transformer, but do you have an opinion?
 
Hi Tosh, yes, the plot is the amp driving the audio step-up transformer directly, no other elements in between, except when I added the 1 Ohm resistance to test its impact.

I have not done an independent test of just the transformer by itself to model it. But supposedly they are good, but there are better ones out there (Amplimo). I plan to update the ones in the Monoliths one of the days, but just have too many other projects going on. I need to retire and tinker, but that's 15 or more years in the future. ;)

The goal of 105dB is at 2m (fully integrating the length of the panel + mid-bass drivers). The finalized SL3XC center yields a THD of 0.6% at 90dB!
 
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