Hello, I have a pair of Martin Logan SL3 with an Advance Acoustic Map-407 amplifier. The problem begins with my old Technics SU-V9 amplifier when at reasonably high volumes when a high frecuency was played the amplifier instantly made clipping and shut itself down being an extremely dissatisfying problem. So I thought that it was power handling problems so I bought a monstrous Advance Acosutic Map-407 (400 watts per channel in 4 ohm) (ML SL3 have 4 ohm) so I was happy then I’ve put a song that i always use for testing speakers (Private Investigations from Dire Straits) and when the best part of the song begins with the cymbals and drums are punches AGAIN! the amplifier get clipped and shuted down the sound at the same volume that the Technics made.
It’s extremely frustrating and I can’t find the problem so I’m begging for help to solve this problems.
My question is.. Where the hell is the problem??
It’s extremely frustrating and I can’t find the problem so I’m begging for help to solve this problems.
My question is.. Where the hell is the problem??
As AVWERK said, the speaker is a tough load, as are many electrostatics. You need an amp that can handle low impedances and large phase angles. If your amp isn't rated at and able to happily drive a 2-ohm load, it's more likely to have issues with your speaker. A 2-ohm rating isn't a guarantee of compatibility, but it's a good starting point.
Your shutdowns are likely about current, not just the power spec into 8 ohms. Not all high powered amps are able to deliver large currents into low impedances. Some don't like a very low impedance, no matter the frequency where it occurs.
Looking for amps others have used successfully with older Martin Logans is a good place to start.
Measurements and commentary here about the load.
MartinLogan SL3 loudspeaker Measurements | Stereophile.com
"Though the impedance drops to 1.5 ohms at 20kHz, there isn't much musical energy present up there, meaning that the amplifier will not be taxed too much. In addition, as is typical, the lowest impedance magnitude coincides with a phase angle of 0 degrees.
However, there are three problem areas at lower frequencies, both where the music has a lot of energy and where the SL3 features a combination of low impedance and high phase angle, something that asks a lot of an amplifier. At 50Hz, 4.5 ohms impedance is coupled with a capacitive phase angle of -47 degrees; at 1kHz, a magnitude of 5 ohms coincides with a phase angle of -42 degrees; while at 8.2kHz, a magnitude of 3.8 ohms combines with a phase angle of -57 degrees. In each case, the amplifier's output stage will be maximally stressed."
Your shutdowns are likely about current, not just the power spec into 8 ohms. Not all high powered amps are able to deliver large currents into low impedances. Some don't like a very low impedance, no matter the frequency where it occurs.
Looking for amps others have used successfully with older Martin Logans is a good place to start.
Measurements and commentary here about the load.
MartinLogan SL3 loudspeaker Measurements | Stereophile.com
"Though the impedance drops to 1.5 ohms at 20kHz, there isn't much musical energy present up there, meaning that the amplifier will not be taxed too much. In addition, as is typical, the lowest impedance magnitude coincides with a phase angle of 0 degrees.
However, there are three problem areas at lower frequencies, both where the music has a lot of energy and where the SL3 features a combination of low impedance and high phase angle, something that asks a lot of an amplifier. At 50Hz, 4.5 ohms impedance is coupled with a capacitive phase angle of -47 degrees; at 1kHz, a magnitude of 5 ohms coincides with a phase angle of -42 degrees; while at 8.2kHz, a magnitude of 3.8 ohms combines with a phase angle of -57 degrees. In each case, the amplifier's output stage will be maximally stressed."
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The parallel combination of ESL with 10 inch woofer is a difficult load for some amps at loud volume.
You could try to passively bi-amp those SL3 to confirm if it's the ESL or the woofer giving the amp trouble. And try one channel at a time to narrow it down? I would expect a bad crossover cap to only affect one speaker...
You could try to passively bi-amp those SL3 to confirm if it's the ESL or the woofer giving the amp trouble. And try one channel at a time to narrow it down? I would expect a bad crossover cap to only affect one speaker...
You might consider looking at a class D amplifier for that (ICEpower or Hypex based). Class D amps usually handle capacitive loads better because a significant capacitor at their output is already part of their circuit. Do be careful, though, they tend to be pretty powerful amps and often can happily deliver a good amount of current into the capacitive ESL.
Hi,
used class-D for my old prototypes (see on my website).
While the class-D amps led the ESLs on a very short rope, i.e. very tight controlled, the sound was anemic, technoid. Quite impressive regarding dynamics and good for Rock/Pop but a nogo for natural instrument and voices.
The amps were regarded rather well and goodsounding ... and at lest with dynamic speakers they were ... but I wouldn´t choose them for ESLs again.
The class-D amps were of the self-oscillating post-feedback-filter design.
Since the output filter is not included in he feedback loop with this design, the output filter forms a resonating filter together with the ESl´s impedance.
In my case resulting in a massive peak around 15kHz which required a rather high-Q notch filter in the xover.
Tests with other class-D amps - with output filter within the feedback loop- reduced the hf-peak, but didn´t improve the sonic character.
I´ve good very experiences with the LJM L12-2 class-AB modules.
They drive my stats with utmost stability and sound very well under all circumstances.
jauu
Calvin
used class-D for my old prototypes (see on my website).
While the class-D amps led the ESLs on a very short rope, i.e. very tight controlled, the sound was anemic, technoid. Quite impressive regarding dynamics and good for Rock/Pop but a nogo for natural instrument and voices.
The amps were regarded rather well and goodsounding ... and at lest with dynamic speakers they were ... but I wouldn´t choose them for ESLs again.
The class-D amps were of the self-oscillating post-feedback-filter design.
Since the output filter is not included in he feedback loop with this design, the output filter forms a resonating filter together with the ESl´s impedance.
In my case resulting in a massive peak around 15kHz which required a rather high-Q notch filter in the xover.
Tests with other class-D amps - with output filter within the feedback loop- reduced the hf-peak, but didn´t improve the sonic character.
I´ve good very experiences with the LJM L12-2 class-AB modules.
They drive my stats with utmost stability and sound very well under all circumstances.
jauu
Calvin
Does the CLS have a protection circuit? When both of these amps show exactly the same behaviour, logic tells you to look at the speaker.
Is it always one channel that cuts out? If you switch the speakers, does the problem move with the speaker or stay at the same channel?
Jan
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There are a bunch or reasons why an ESL might cause trouble for an amp.
Capacitive loads can cause an amplifier with a small phase margin to burst burst into song - resulting in large increasing voltage and current swings.
With a pure resistor load, some of the power is dissipated in the load and some in the amplifier. With a capacitive load of the same impedance, all of the power is dissipated in the amp - more heat, higher temperature.
Perhaps most difficult problem from the amplifier design point of view is that capacitive loads have the the peak in load currents when the output voltage from the amp is zero - that means the output transistors have the maximum current at the same time as the maximum voltage across them - which pushes them to the extreme of their safe operating area and secondary breakdown.
There are also differences between ESLs. The usual DIY ESL made as a single large panel will have large capacitance which requires the amplifier to have a low output resistance and inductance to get a wide bandwidth - and tends to limit transformer step up ratios to 60 or so. With such low impedances involved, fault currents when they occur can be massive.
The ESL 63 style ESL with the annular segmentation and connected as an LC transmission line means that the ESL impedance behaves as a pure resistance - the friendliest of loads for amplifiers.
The line-source segmented ESLs connected as an RC transmission line has an impedance midway between the resistive and capacitive load, but at the high audio frequencies - 20 kHz say - then the load capacitance is about 1/20th of the single segment ESL - so a much easier load than the single segment ESL - even with a higher step up ratio on the transformers, the impedance is still a bit more favourable.
Capacitive loads can cause an amplifier with a small phase margin to burst burst into song - resulting in large increasing voltage and current swings.
With a pure resistor load, some of the power is dissipated in the load and some in the amplifier. With a capacitive load of the same impedance, all of the power is dissipated in the amp - more heat, higher temperature.
Perhaps most difficult problem from the amplifier design point of view is that capacitive loads have the the peak in load currents when the output voltage from the amp is zero - that means the output transistors have the maximum current at the same time as the maximum voltage across them - which pushes them to the extreme of their safe operating area and secondary breakdown.
There are also differences between ESLs. The usual DIY ESL made as a single large panel will have large capacitance which requires the amplifier to have a low output resistance and inductance to get a wide bandwidth - and tends to limit transformer step up ratios to 60 or so. With such low impedances involved, fault currents when they occur can be massive.
The ESL 63 style ESL with the annular segmentation and connected as an LC transmission line means that the ESL impedance behaves as a pure resistance - the friendliest of loads for amplifiers.
The line-source segmented ESLs connected as an RC transmission line has an impedance midway between the resistive and capacitive load, but at the high audio frequencies - 20 kHz say - then the load capacitance is about 1/20th of the single segment ESL - so a much easier load than the single segment ESL - even with a higher step up ratio on the transformers, the impedance is still a bit more favourable.
Reading this again, are you saying that BOTH amplifiers are equipped with a shut down system and BOTH shut down the same way? Again, is it not logical to assume that the CLS shuts down?
Jan
The SL3 xover has a 'music sense' and 'high voltage detect' circuit which could cause issues, especially since it happens with different amps all the same.
The 'music sense' appears to switch the HV supply on and off, could mean normal and lower volume.
Does the LED change intensity when it shuts down?
Any other ideas?
Jan
The 'music sense' appears to switch the HV supply on and off, could mean normal and lower volume.
Does the LED change intensity when it shuts down?
Any other ideas?
Jan
Attachments
Exactly, that is the weridest thing, considering that both amps are completely different, one from 2008 and the other from the 80s, and the same problem
I find very weard that a speaker have a protection system
My crossover is exactly the same as the one in the last photo (right one). So is the new one. That transformer that you have in that crossover is for 220 volts? because I have the same one in my crossover and my outlets are 220 volts
Thanks for your answer!
I'm going to check the red led light, thanks for you help! and if the speaker have that system, how can i solve this problem?
thanks for your help
I had two low-current receivers from different manufacturers I previously used for testing. Both of them exhibited the behavior you describe when driving difficult electrostatic speaker loads. They behaved normally at low to moderate levels, but playing too loud tripped their protection circuits.
Of course I can't say for certain it's your problem, but what you describe isn't that abnormal.
What I was wondering, do both channels do exactly the same at the same time? Or is it a single channel that shuts down?
If both channels do the same at the same time, that would point to the amps.
I looked for some info about your amps regarding protection circuits, whether they are actually included, but there's no mention of it I could find.
Jan
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USA models of SL3 (and other MLs) have a gray-market discouraging (private exporting) mains frequency-sensing circuit which wants to see the actual 60Hz, or it acts up....(and I think you have 50Hz in Chile?)
Bolserst discussed it in one of our threads and how to defeat it. Here:
https://www.diyaudio.com/forums/pla...is-power-supply-board-help-5.html#post6117458
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