Interesting find when pulling out my Summit back plates...

[Hocky]

I pulled out one of me Summit backplates for inspection yesterday and noticed something interesting. As far as I can tell, the ESL panel actually has no crossover - it is run full range directly off of the binding posts on the back of the plate. There are no PCB connections to this signal at all. Are all MLs designed like this? If this is the case and there is not some sort of method of attenuating the signal at the panel, I am very surprised that a panel as large as this rolls off so high in the frequency range.

 

[spectral]

Can you post pictures? Sounds like something is amiss - never mind the crossover, it sounds like there is no step-up circuitry either; this sounds too good to be true... a panel that works on a few volts coming out of the amplifier...

 

[beek]

I guess Roberto needs to chime in here, can you see where those 2 wires go right to the stat panel?

 

[beek]

My thoughts exactly,as far as I know electrets don't need additional power but that's not the case here.

 

[JordanD]

Yup, that is one of the allures of ML ESL speakers. No crossover! Yay! Unlike the Maggies... haha but I digress.

You will actually find this fact on all of ML ESL models.

This is a good thing due to that fact that crossovers, as good as they can be, are not perfect and CAN loose some detail. I like to liken them to a drunken traffic cop trying to get the right cars (frequencies) onto the right roads.

But if you remove the 'traffic cop' then you dont have to worry about the errors or loss in fidelity.

 

[Hocky]

Can you post pictures? Sounds like something is amiss - never mind the crossover, it sounds like there is no step-up circuitry either; this sounds too good to be true... a panel that works on a few volts coming out of the amplifier...

The step up transformer does connect to the panels, too. It is just that the incoming signal is unmodified and sent straight to the panel, thus actually playing the full frequency range and not just over 200hz. I do have a picture - I will try to post it up tonight.

 

[Hocky]

Yup, that is one of the allures of ML ESL speakers. No crossover! Yay! Unlike the Maggies... haha but I digress.

You will actually find this fact on all of ML ESL models.

This is a good thing due to that fact that crossovers, as good as they can be, are not perfect and CAN loose some detail. I like to liken them to a drunken traffic cop trying to get the right cars (frequencies) onto the right roads.

But if you remove the 'traffic cop' then you dont have to worry about the errors or loss in fidelity.

Yea, I can definitely understand that. I just would think that the panel playing full range would add additional problems, too, down under the bass section crossover point. And I am really surprised that such a large panel rolls off so fast around 200hz or so.

 

[repman]

Using a precision Vojtko Voiced™ crossover network to apply variable phasing near the crossover point, Summit X's Controlled Dispersion PoweredForce™ technology provides seamless blending with the XStat™ transducer.

from the Martin Logan website , Martin Logans use crossovers from the woofers to the panels.

 

[Hocky]

Using a precision Vojtko Voiced™ crossover network to apply variable phasing near the crossover point, Summit X's Controlled Dispersion PoweredForce™ technology provides seamless blending with the XStat™ transducer.

from the Martin Logan website , Martin Logans use crossovers from the woofers to the panels.

But based on the hardware that I am looking at, no crossover is applied to the panels. A crossover is definitely applied to the woofers.

 

[Hocky]

I forgot I had a picture on my phone. In this picture, you can see the large red and black wires - these two wires go directly to the panel. If you look closely on the PCB, there is a circle around both of these connections - no traces come into or out of that circle. On the outside of the plate, those bolts that the red and black wires are connected to are actually the binding posts.

 

[JordanD]

Using a precision Vojtko Voiced™ crossover network to apply variable phasing near the crossover point, Summit X's Controlled Dispersion PoweredForce™ technology provides seamless blending with the XStat™ transducer.

from the Martin Logan website , Martin Logans use crossovers from the woofers to the panels.

Yeah but I think there is a bit of a misunderstanding. The way (or the I was thought by someone at ML) the ML speakers work is that the panels get their signal straight from the posts meanwhile splitting the signal path and running the same signal to the 'sub' and actually using more of a filter more then a crossover but basically the same thing.

Of course it is far more complex then that, but its just a quick overview for understanding purposes. And for these reasons it became a differentiating factor for ML against competition and an explanation as to why they sound so good, because of the lack of a 'crossover.'

 

[Peter Soderberg]

ok guys, we did not reinvent physics. what everyone is forgetting is that there are two chambers on a Summit as both woofers have their own air volumes. The back panel is the active electronics and the passive xover and transformer are in the other chamber. I had a cutaway once showing that, but no more. there is a slope for the panel and another for the bass on the xover. where we stress lack of xover is in the critical mid to lower treble where virtually everyone else has one which also happens to be where most ears are sensitive to distortions. At lower frequencies, ears are simply less sensitive so we do our best to create a real world speaker that will fit into rooms, play loud, be smaller footprints, etc.

 

[miljac]

I don't believe that there is not even a transformer in the signal path to the panel.

In this case the amplifier should produce kilovolt level voltages which is certainly
not the case (at least with "normal" amplifiers)

[edit] cross posted with Peter. Thanks for the explanation.

 

[RUR]

ok guys, we did not reinvent physics. what everyone is forgetting is that there are two chambers on a Summit as both woofers have their own air volumes. The back panel is the active electronics and the passive xover and transformer are in the other chamber. I had a cutaway once showing that, but no more....

http://www.martinloganowners.com/fo...-Summits-Buzzing&p=33268&viewfull=1#post33268

 

[Hocky]

ok guys, we did not reinvent physics. what everyone is forgetting is that there are two chambers on a Summit as both woofers have their own air volumes. The back panel is the active electronics and the passive xover and transformer are in the other chamber. I had a cutaway once showing that, but no more. there is a slope for the panel and another for the bass on the xover. where we stress lack of xover is in the critical mid to lower treble where virtually everyone else has one which also happens to be where most ears are sensitive to distortions. At lower frequencies, ears are simply less sensitive so we do our best to create a real world speaker that will fit into rooms, play loud, be smaller footprints, etc.

Ah.... this make more sense. ;-) So the two leads coming off of this board actually go to another board closer to the front driver in which they pass through a crossover.

 

[roberto]

Hola Hocky. From the opened bottom board, there are two cables, red and black that go inside to another PC board that it is located at top, next to the other woofer, and which it is the hi-pass crossover. Then from that P.C. Board, we have three cables that go to the primary windings of a transformer. From the transformer secondary windings wires, sides cables go to the stat panels metal sheets, front and rear, then the center tag goes to HV power supply. This is as I recall. Happy listening,
R.

 

[wallacefl]

There would be some big problems with the natural roll-off below the frequency set by the width of the panel if the panel was run full range...but I would certainly like to see if ML could lower the crossover frequency to less than 200hz.

 

[roberto]

It is not full range...from that point, goes to the upper chamber and there is the crossover.