New Member - long time ML owner

[Robert D]

I've been racking my brain trying to figure out how ML could use the high-level output from the owner's amp as an input for a DSP, which seemed impossible to me.

I couldn't find any info on the ML 11 but I found a PDF of the ML ESL 11a Owner's Manual, wherein the following excerpt explains [almost] everything:

"PoweredForce™ bass technology results in immense bass dynamics
and precision beyond the reach of traditional passive box systems.
Additionally, room correction and low-frequency equalization capa-
bilities allow precision calibration for optimal room integration.
Featuring an advanced crossover topology, each crossover uses preci-
sion audiophile-grade polypropylene capacitors, toroidal transformers,
and high-purity air-core and iron-core coils."

So now we know that the crossover is indeed passive, and only the bass band receives line-level DSP room correction, which is applied to the low-level signal feeding the built in bass amps.

The mids/highs receive no DSP correction.

Toroidal transformers would not typically be used in a passive crossover, which leads me to believe the setup works like this (no line level input from the owner's preamp required):

A passive crossover splits out the bass and mid/treble bands, and routes the mid/treble band power to the ESL panel.

The spit-out bass band then feeds into dual transformers which steps down the signal voltage (in two steps) to provide a line-level input for the DSP. The DSP then applies room correction and feeds the corrected singal to a pair of Class D bass amps powering the dual 8" woofers.

This setup likely improves any issues with bass/room interactions, and also provides plenty of power for bass output. This is a pretty goon compromise which allows using the owner's amp to power the panel.

However, this setup is less effective or desirable than a fully active setup, insofar as the already-amplified music signal is pushed through a power-robbing passive crossover, and there is no real-time tuning capablity (you have to live with what the passive crossover gives you).

Yeah, that's what my guess was. That's too bad. The Sanders speakers sold have active crossovers. He knows it's superior. Right now my Prodigies sound great, but I feel confident using active crossovers will improve the sound.
How pronounced is the change when you switch over? The speakers end up getting a stronger signal also, so more volume?
Would running active crossover on the 11s or higher end up causing problems, since the woofer is already going through an active crossover? I guess you'd need to bypass it too?

 

[Jazzman53]

Yeah, that's what my guess was. That's too bad. The Sanders speakers sold have active crossovers. He knows it's superior. Right now my Prodigies sound great, but I feel confident using active crossovers will improve the sound.
How pronounced is the change when you switch over? The speakers end up getting a stronger signal also, so more volume?
Would running active crossover on the 11s or higher end up causing problems, since the woofer is already going through an active crossover? I guess you'd need to bypass it too?

Actually, I can only compare the sound of my fully active speakers to other hybrid ESLs which use passive crossovers.

My speakers were always actively bi-amp'd, and never used a passive crossover.

For a DIY speaker builder, it's much easier to use an active crossover rather than spend months trying to dial in a passive crossover, and an active crossover sounds better anyway.

Initially I used a vintage Carver C1 preamp feeding an op-amp driven DBX 223 active analog crossover upstream of a pair of Carver TFM-25 power amps.

Later I added a pair of RiPol subs and a third amp, changing my system to 6-channel stereo. I also replaced the analog crossover with a Behringer DCX 2496 digital crossover, and added a Behringer DEQ2496 digital EQ. This setup sounded really good but the Behringers' user interfaces were so outdated that I had to use the front panel controls because their computer interfaces used obsolete serial ports.

I eventually replaced the Behringer's with a DBX Driverack Venu 360, which sounds fabulous and uses a very sexy Ipad control interface.

Four friends I built speakers for all use a DBX Driverack PA2, which has basically the same features as the Venu 360 except without the digital inputs (balanced analog XLR inputs only), at half the price. They all love the PA2.

The Venu 360's added digital inputs allowed me to omit the analog preamp and use my Logitech Transporter's digital preamp instead. I'm feeding the Transporter's digital out to the digital in on the Venu 360. In this way, multiple D/A & A/D conversions are elminated and I have only a single D/A conversion, at the output of the Venu 360, to the amps.

LOVE IT!

 

[Robert D]

Actually, I am only comparing the sound of my fully active speakers to other hybrid ESLs which use passive crossovers.

My speakers were not changed from passive to active, as they have always used an active crossover.

I initially bi'amp'd them-- feeding the analog out from a Carver C1 preamp into an op-amp driven DBX 223 analog crossover, upstream of a pair of Carver TFM-25 power amps.

Later I changed my setup to 6-channel stereo, by adding a pair of RiPol subs and a third amp. I also replaced the analog crossover with a Behringer DCX 2496 and added a Behringer DEQ2496 digital EQ. It sounded really good but the Behringers' user interfaces were seriously outdated. I couldn't use their computer interfaces becuse they used a serial ports, which newer laptops don't have, so I had to use the clunky front panel interface. Additionally, the DEQ's auto-EQ used obnoxious pink noise, and it wasn't at all user friendly.

Finally; I replaced the Behringer's with a DBX Driverack Venu 360, which sounds fabulous and uses a very sexy Ipad control interface.

Several of my friends who I built speakers for use a DBX Driverack PA2, which has basically the same features as Venu 360 except for digital ins (balanced analog XLR inputs only), and the PA2 is half the price. They all love the PA2.

I opted for the Venu 360 because it allowed me omit an analog preamp and use my Logitech Transporter's digital preamp instead. I'm feeding the Transporter's digital out to the digital in on the Venu 360. In this way, multiple D/A & A/D conversions are elminated and I have only a single D/A conversion, at the output of the Venu 360, to the amps.

LOVE IT!

I'd like to hear it!

 

[Jazzman53]

I'd like to hear it!

Well Robert, you have a standing invitation to drop by my place in Savannah, GA for a jam session anytime.

BTW; I haven't been advertising this, but;
I happen to have a new/unused pair of my Jazzman MkIII hybrid ESL speakers, which I would let go at a bargain price.

These speakers do not include a crossover, and must be bi-amplified using an active crossover upstream of the power amps. I recommend a DBX Driverack PA2 DSP crossover with matching DBX microphone, for tuning.

I completed these speakers in the spring of 2022, just to use up my remaining materials stock after retiring from speaker building, and they've been sitting idle in the back room of my house ever since. They need to sing!

These hybrid ESLs are red oak in satin finish, with state-of-the-art, tailored-dispersion, symmetrically segmented wire-stators, 12" open baffle woofers, and include acoustically transparent front & rear magnetic grills, as shown on my website here.

I back them with a 90-day full-refund satisfaction guarrantee and a 5-year parts & labor warranty (same as a ML). BTW, I'm 72, so the warranty is 5 years or my lifetime, whichever expires first

The caveat is that shipping would be prohibitive so buyer would have to pick them up in Savannah, GA.

Enjoy your day.

Charlie

 

[Robert D]

Well Robert, you have a standing invitation to drop by my place in Savannah, GA for a jam session anytime.

BTW; I haven't been advertising this, but;
I happen to have a new/unused pair of my Jazzman MkIII hybrid ESL speakers, which I would let go at a bargain price.

These speakers do not include a crossover, and must be bi-amplified using an active crossover upstream of the power amps. I recommend a DBX Driverack PA2 DSP crossover with matching DBX microphone, for tuning.

I completed these speakers in the spring of 2022, just to use up my remaining materials stock after retiring from speaker building, and they've been sitting idle in the back room of my house ever since. They need to sing!

These hybrid ESLs are red oak in satin finish, with state-of-the-art, tailored-dispersion, symmetrically segmented wire-stators, 12" open baffle woofers, and include acoustically transparent front & rear magnetic grills, as shown on my website here.

I back them with a 90-day full-refund satisfaction guarrantee and a 5-year parts & labor warranty (same as a ML). BTW, I'm 72, so the warranty is 5 years or my lifetime, whichever expires first

The caveat is that shipping would be prohibitive so buyer would have to pick them up in Savannah, GA.

Enjoy your day.

Charlie

That's great, thanks. Those speakers skund good i bet.

 

[Jazzman53]

I've been racking my brain trying to figure out how ML could use the high-level output from the owner's amp as an input for a DSP, which seemed impossible to me.

I couldn't find any info on the ML 11 but I found a PDF of the ML ESL 11a Owner's Manual, wherein the following excerpt explains [almost] everything:

"PoweredForce™ bass technology results in immense bass dynamics
and precision beyond the reach of traditional passive box systems.
Additionally, room correction and low-frequency equalization capa-
bilities allow precision calibration for optimal room integration.
Featuring an advanced crossover topology, each crossover uses preci-
sion audiophile-grade polypropylene capacitors, toroidal transformers,
and high-purity air-core and iron-core coils."

So now we know that the crossover is indeed passive, and only the bass band receives line-level DSP room correction, which is applied to the low-level signal feeding the built in bass amps.

The mids/highs receive no DSP correction.

Toroidal transformers would not typically be used in a passive crossover, which leads me to believe they are there to provide a line level bass signal for the DSP engine (eliminating the need for a line level input from the owner's preamp).

I think it works something like this:
A passive crossover splits out the bass and mid/treble bands, and routes the mid/treble band power to the ESL panel.

The spit-out bass band then feeds into dual transformers which steps down the signal voltage (in two steps) to provide a line-level input for the DSP. The DSP then applies room correction and feeds the corrected singal to a pair of Class D bass amps powering the dual 8" woofers.

This setup likely improves any problems with bass/room interactions, and also provides plenty of power for bass output. This seems to me an OK compromise and good market strategy targeting owners who prefer using their own amp to drive the panel.

However, this setup is less capable than a fully active setup, in that an already-amplified music signal is being pushed through a power-robbing passive crossover, and it provides no user-tuning capability for the ESL panel.

I've just learned from a source who actually knows the layout of the ESL 11 crossover, that the low-pass output from the passive crossover is stepped down to line-level voltage by resistors, not by the transformers mentioned in ML's crossover description.

That being the case; those transformers can only be the step-up transformers that power the stators in every ESL.

My definition of “crossover’ tripped me up here, as I have always considered the step-up transformers as separate from the 'crossover'.

Now we know

 

[liffy99]

For the benefit of anyone unfamiliar with active bi-amping, and how crossovers work;

A passive crossover splits the high-level (already amplified) signal into separate bass and mid/treble bands, which then separately drive the woofer and ESL panel.

A low-pass filter, consisting of a series inductor (a coil of small diameter wire many feet in length) with a resistor in parallel, blocks high frequencies and passes only low frequencies to the woofer.

(as an aside; it kills me how audiophiles spend huge money on big fat speaker cables, only to connect them to a passive crossover where the signal has to pass through a 120' coil of small diameter wire-- it's like coupling a fire hose to a soda straw).

A high-pass filter, typically consisting of a series capacitor and a parallel resistor, blocks low frequencies and passes only mid/high frequencies to the ESL panel.

When passively splitting an already-amplified signal (downstream from the amp), significant signal power is lost to heat as the signal is pushed through the filters. Also, the amplifier's ability to control driver motion is somewhat impaired by the passive components between them.

Whereas; an active crossover splits the line-level music signal coming out the preamp (upstream of the amps)-- sending bass frequencies to a separate amp powering the woofer, and mid/treble frequencies to a separate amp powering the ESL panel.

In this case the amplifiers are directly coupled to the drivers, resulting in practically no power loss, and more control over driver motion. This is particularly noticeable in the bass band.

Additionally; active crossovers can use steeper slopes (up to 24db for op-amp analog types or 48db for digital) without introducing significant distortion. This allows greater flexibility in selecting crossover frequencies, and allows playing to higher volume levels before there is risk of driving the diaphragm into a stator.

Passive crossovers are typically limited to 12db/octave of slope, as steeper slopes done passively would incur excessive power loss and audible distortion. The upside is cost, as a single stereo amp can then drive a pair of multi-driver speakers.

It should be noted however, that passive crossovers often include shelving and/or notch filters to tamp down resonances and/or tune the speaker's frequency response, and if so, this tuning would be lost when bypassing the passive crossover. Accordingly; EQ'ing may be required when changing from a passive to an active crossover.

Most active analog crossovers lack EQ capability, in which case a separate graphic or parametric EQ may be needed for tuning.

A DSP crossover resolves all problems, and most have Auto-EQ capability, which plays test tones through the system that are picked up by a microphone, and the DSP then automatically overlays parametric EQ's to bring the frequency response to whatever pre-selected curve the user chooses.

Provided the speakers have the basic capabilities, a DSP can make them sound anyway one likes...it's bloody marvelous!

Brilliant explanation. I’ve been actively bi-amping my Quad ‘stats with some passive woofers ( driven by a second amp) with good results. But wife wants smaller speakers. Loved the 11As but tempted by the 9s due to their passive setup. Two questions;
Does anyone have a guide as to how to bypass the ML crossover ? Presumably I need to still go through an audio transformer to connect to the panels.
And does my DSP amp (Lyngdorf) have enough flexibility to dial in an appropriate crossover ?
I can change; crossover frequency, type (LR or Butterworth), slope up to 48db/oct, relative level between high and low frequency amps. In addition there is a parametric equaliser enabling a range of ‘voicings’ and, after all that, Roomperfect room correction software.

 

[Jazzman53]

Brilliant explanation. I’ve been actively bi-amping my Quad ‘stats with some passive woofers ( driven by a second amp) with good results. But wife wants smaller speakers. Loved the 11As but tempted by the 9s due to their passive setup. Two questions;
Does anyone have a guide as to how to bypass the ML crossover ? Presumably I need to still go through an audio transformer to connect to the panels.
And does my DSP amp (Lyngdorf) have enough flexibility to dial in an appropriate crossover ?
I can change; crossover frequency, type (LR or Butterworth), slope up to 48db/oct, relative level between high and low frequency amps. In addition there is a parametric equaliser enabling a range of ‘voicings’ and, after all that, Roomperfect room correction software.

Possibly someone on this forum has bypassed the passive crossover in a ML speaker but I haven't, and I don't want to speculate on which wires you would need to clip.

All I can show you is a schematic of my DIY speaker (link below) which never had a passive crossover so its interface is minimal and simple--- just a tandem pair of transformers and a simple HV bias supply with it's ground side center tapped between the transformers. Nothing more is needed. https://jazzman-esl-page.blogspot.com/

The woofer portion is easy enough--amp outs to woofer terminals. As for the panel portion; if you have a schematic of your speaker you can probably figure out how to bypass everything but the step-up transformer and bias supply.

The choice of DSP crossover filter type is a matter of personal preference. I prefer a symmetric Linkwitz-Riley filter with either a 24db or 48db slope. A 24db slope makes tuning a bit easier but a 48db slope minimizes the overlap bandwidth, which allows playing the panel lower and louder (before there is risk of driving the diaphragm into a stator).

I like the LR filter because its essentially phase-perfect.

 

[Russr]

Brilliant explanation. I’ve been actively bi-amping my Quad ‘stats with some passive woofers ( driven by a second amp) with good results. But wife wants smaller speakers. Loved the 11As but tempted by the 9s due to their passive setup. Two questions;
Does anyone have a guide as to how to bypass the ML crossover ? Presumably I need to still go through an audio transformer to connect to the panels.
And does my DSP amp (Lyngdorf) have enough flexibility to dial in an appropriate crossover ?
I can change; crossover frequency, type (LR or Butterworth), slope up to 48db/oct, relative level between high and low frequency amps. In addition there is a parametric equaliser enabling a range of ‘voicings’ and, after all that, Roomperfect room correction software.

I'm not sure I have seen any posts about performing crossover surgery on the current models, but there are several threads about "going active" on the older ones. Below is a link talking to Aerius, but there are similar posts on Requests and SL3s.

https://www.martinloganowners.com/threads/how-to-active-bass-section.19237/

Hope this is helpful!

 

[JonFo]

Does anyone have a guide as to how to bypass the ML crossover ? Presumably I need to still go through an audio transformer to connect to the panels.

Not a guide per se, but this thread following my SL3XC build details what I did to bypass it in an SL3.
I guess that in the current lineup, it is not that different, with one board for the 'music sense' and AC input, which is connected to the panel feed, then a separate board with the passive XO elements that feed the step-up-transformer for the panel. Models >ESL9 have a DSP board and amps for the woofer.

And does my DSP amp (Lyngdorf) have enough flexibility to dial in an appropriate crossover ?
I can change; crossover frequency, type (LR or Butterworth), slope up to 48db/oct, relative level between high and low frequency amps.

Yes, that sounds like you can use one stereo amp to perform the crossover and power both the woofer and the panel. So you'd need two amps for stereo.

I'd guess a high pass at 380Hz using a 48dB/oct slope for the panel and a low pass at 380 using a 24dB/oct LR would work well. The gentler slope on the low pass means the woofer reinforces a bit more of the upper bass frequencies that see the most impact from dipole cancelation on the panel.