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Post by adaboy on Jan 21, 2019 10:54:02 GMT -5
Just to clarify one detail that many people seem to find confusing. A pure resistance remains the same at all frequencies (so, for example, a "4 Ohm speaker" that doesn't exhibit any reactance will be 4 Ohms at 20 Hz, 4 Ohms at 1 kHz, and 4 Ohms at 20 kHz). A load that exhibits capacitive reactance will have an impedance that gets lower as the frequency goes higher; a load that exhibits inductive reactance will do the opposite. Virtually all speakers are somewhat reactive, and most have an impedance that zigs and zags up and down because they actually have a rather complicated combination of inductances and capacitances. However, most "well behaved" speakers are mostly resistive - and most 4 Ohm speakers never fall below about 2.5 Ohms anywhere in the audible frequency range.
Most amplifiers are designed to work best with a purely resistive load. Most amplifiers also work just fine with a well-behaved load (see above).
What we're talking about here is how tolerant a particular amplifier with difficult load. Asking an amplifier to drive a load that drops to 0.5 Ohms at 20 kHz is about equivalent to towing a small house using a consumer pickup truck. It's actually WORSE than Boom indicates. Not only is the impedance at higher frequencies nearly a dead-short, but the REACTANCE is a dilly, too. www.stereophile.com/content/sound-lab-1-electrostatic-loudspeaker-measurementsWhile this is ONE electrostat, these measures follow the typical pattern. The 75 degrees at the highest frequencies is something that FEW amps will work well with and virtually NO HT receivers. Just read the first paragraph of the review. Than have a look at the graph of impedance and phase data. Where the 2 lines cross, if at a low impedance AND high phase angle, spells TROUBLE. Get an old Krell and be done with it. Some persons dont' agree with the Mc house sound. Another POSSIBLE solution would be to use an impedance matching transformer between amp and speaker. I can't find the link right away, but this article might be of some help. www.electronics-tutorials.ws/transformer/audio-transformer.htmlBut they can pull space shuttles 😊  I do throughly enjoy reading your electro-historian post. They offer a great layman's understanding of complicated tech speak. One day when I make it to Franklin would love to hear a lecture or two in person. Now back to the problem at hand, what are your thoughts Keith? |
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Post by leonski on Jan 21, 2019 13:14:20 GMT -5
Do ANY pure resistive speakers exist, even in a laboratory?
Even my original MG-1 panels, were 5 ohms NEARLY pure resistive......and were quite amplifier 'friendly'.
And REAL speaker wires will 'defeat' any mythical pure resistive driver. All speaker wires exhibit some reactance. For example, my speaker wires are
called out at maybe 10 PicoFarads per foot. It all adds up when making long runs. Which I no longer do. I can't find real measurements.
Other cables, with, for example, wires an INCH apart will have a good deal of inductance which can also 'add up'.
So even if you DID have a purely resistive driver? You'll have to deal with real wire. So while any amp will work with that situation, adding reactance to an already HIGHLY reactive load
just May push you over the edge.
I'm waiting for what EMO says about running the DR-3 with the ML 'Stats mentioned by the OP. And what speaker wires they used!
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KeithL
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Post by KeithL on Jan 21, 2019 16:30:39 GMT -5
In terms of what most amplifiers will work with, the capacitance of ordinary speaker wire is negligible. (Some obscure audiophile cables in the past have exhibited unreasonable amounts of capacitance or inductance; enough even to damage an amplifier occasionally.)
In normal speakers, the voice coils in the driver are inductive, and the crossover contains a variety of inductors and capacitors.
In a typical electrostatic speaker, the panels themselves are purely capacitive, and the effect of their capacitance is amplified by the transformer most of them contain. The combination offers a complex, highly reactive, and difficult to drive combination. Magneplanars offer a somewhat what low, but quite benign, and almost totally resistive, load to the amplifier.
Do ANY pure resistive speakers exist, even in a laboratory? Even my original MG-1 panels, were 5 ohms NEARLY pure resistive......and were quite amplifier 'friendly'. And REAL speaker wires will 'defeat' any mythical pure resistive driver. All speaker wires exhibit some reactance. For example, my speaker wires are called out at maybe 10 PicoFarads per foot. It all adds up when making long runs. Which I no longer do. I can't find real measurements. Other cables, with, for example, wires an INCH apart will have a good deal of inductance which can also 'add up'. So even if you DID have a purely resistive driver? You'll have to deal with real wire. So while any amp will work with that situation, adding reactance to an already HIGHLY reactive load just May push you over the edge. I'm waiting for what EMO says about running the DR-3 with the ML 'Stats mentioned by the OP. And what speaker wires they used! |
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Post by KeithL on Jan 21, 2019 16:36:34 GMT -5
Certain Martin Logan electrostatics (and a few others) are both highly capacitive and offer a ridiculously low impedance at high frequencies. In addition to that, some have other unusual circuit characteristics that also make life difficult for an amplifier. In most cases our amplifiers work well with even "difficult to drive electrostatics" - but there seem to be a few exceptions.
Lonnie is working with the folks from ML to figure out what's going on in this particular situation.
Just to clarify one detail that many people seem to find confusing. A pure resistance remains the same at all frequencies (so, for example, a "4 Ohm speaker" that doesn't exhibit any reactance will be 4 Ohms at 20 Hz, 4 Ohms at 1 kHz, and 4 Ohms at 20 kHz). A load that exhibits capacitive reactance will have an impedance that gets lower as the frequency goes higher; a load that exhibits inductive reactance will do the opposite. Virtually all speakers are somewhat reactive, and most have an impedance that zigs and zags up and down because they actually have a rather complicated combination of inductances and capacitances. However, most "well behaved" speakers are mostly resistive - and most 4 Ohm speakers never fall below about 2.5 Ohms anywhere in the audible frequency range.
Most amplifiers are designed to work best with a purely resistive load. Most amplifiers also work just fine with a well-behaved load (see above).
What we're talking about here is how tolerant a particular amplifier with difficult load. Asking an amplifier to drive a load that drops to 0.5 Ohms at 20 kHz is about equivalent to towing a small house using a consumer pickup truck. But they can pull space shuttles 😊 I do throughly enjoy reading your electro-historian post. They offer a great layman's understanding of complicated tech speak. One day when I make it to Franklin would love to hear a lecture or two in person. Now back to the problem at hand, what are your thoughts Keith? |
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Post by leonski on Jan 21, 2019 16:39:10 GMT -5
Excellent answer. Get to 'root' on this.
No shame in not being able to drive some 'Stats.
That's why I suggested Lincoln Electric or Miller.
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Post by garbulky on Jan 21, 2019 17:56:04 GMT -5
The impeadance on a fully balanced amp like the DR-1 is actually half of the real value. So what that means is a 4 ohm speaker is seen as 2 ohms to the balanced amp. And a 2 ohm signal - 1 ohm. And a 1 ohm - 0.5 ohms! So properly engineered balanced amps are designed to handle these ridiculously low impedances. However keep in mind that once you dip below a 1 ohms signal (2 ohm speaker load) you are likely going to be triggerring protection circuits in a balanced amp.
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Post by exnihilo1031 on Feb 4, 2019 15:53:52 GMT -5
Figured I'd update.
Had not used amp since last test. Lonnie requested that I try testing some other configurations (each pair of speakers , rather than individually), since the testing he was doing in house with Martin Logan ESL's and the DR3 was not showing the same problem at all.
So when I got home I tried that, however the behaviour had changed entirely, now the amp faults instantly. SO I repeated the past tests as well, same behaviour, instant fault.
After one more correspondence with Lonnie, he suggested I try the amp connected just to the source, and the amp with no wires (I suspected this was to test if it was just bricked). Lo and behold, the amp still faults instantly.
I have no idea why it kind of worked at the start, and why now it fails so badly, but Emotiva is having me ship back the amp for repair/warranty.
Ill check back in here when I get it back and hopefully can say it works perfectly.
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Post by Boomzilla on Feb 4, 2019 19:32:47 GMT -5
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Post by exnihilo1031 on Mar 23, 2019 16:26:06 GMT -5
Emotiva repaired and returned my amp to me, and it is now working. The apparent cause was that it took some kind of surge (although this did not explain the issues leading up to its final breakage).
Lonnie replied and said they found the ground fuses were blown, and that is usually caused by either a powered speaker back feeding current into the amp or a high voltage surge like a near by lighting strike. However neither of these things had happened, so we were unable to get a full root cause.
In any case, now I have a wonderful working DR3 with my Martin Logans. Just figured I'd update and close out the thread.
Thanks for the help and advice all.
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ttocs
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Post by ttocs on Apr 18, 2019 20:58:27 GMT -5
exnihilo1031, I'm curious to know how you like the DR3 with the ML's now that you've had them sorted for a while? (just came across this thread)
When I saw Emotiva at AXPONA I was intrigued by the HC-1 mono amp, I'm wanting to check into monos for my Expressions, I've never had an opportunity to compare a multi-channel amp to mono amps. The only holdup for this amp is getting the cases into the USA, they're on a boat somewhere.
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Post by iluvboxing on Jun 15, 2022 14:26:40 GMT -5
Directly from Martin Logans website. IMPEDANCE: 4 Ohms (0.6 at 20kHz), compatible with any amplifier Martin-Logan prevaricates. Their nominal and minimum impedance numbers are correct, but what they don't say (and it's equally important) is that the impedance typically CONTINUES dropping above 20 KHz, and that at turn on, the overall impedance is lower until the electrostatic stator becomes fully charged. And now for the misdirection (to put it politely) - The Martin-Logans are definitely NOT compatible "with any amplifier." I've had an Emotiva XPA-1L blow out on startup when hooked up to ML speakers. The OP of this thread is having continued problems with his amps tripping off due to the ML speakers. These are not unique or even unusual occurrences with electrostatic speakers (of any brand). The amplifiers most compatible with electrostatic speakers are: Those with output transformers in series with the speakers' impedance (the McIntosh "autoformer-coupled" amps are in this category) Those with delayed turn-on, allowing the electrostatic stators to stabilize while the amp warms up (tube-rectified amps are in this category) Those specifically designed to be stable into low-impedance loads (Krell and most "pro" amplifiers are in this category) Note that in the Best-Buy/Magnolia kiosks nation-wide, their Martin-Logan speakers on display are ALWAYS paired with McIntosh amplifiers. This isn't to say that many (maybe even most) amplifiers won't work just fine with ML speakers - but it IS to say (emphatically) that ML speakers are not compatible with just "any" amplifier. This isn't an opinion - it's a fact (despite what Martin-Logan claims). Boomzilla Which Martin Logan speakers are you speaking of specifically? I ask because I had a lengthy conversation with ML recently about the XPR, XPL, and current DR line up. Their perspective is that they have not noted compatibility issues with their speakers. Perhaps there was something else in the electronics chain that caused the OP’s and your issue with the XPA-1? |
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Post by Boomzilla on Jun 15, 2022 14:47:34 GMT -5
Hi iluvboxing - I think you are probably correct. The vast number of ML electrostatic hybrid owners note absolutely no compatibility issues with their electronics. This even applies to AVR owners whose internal amps are not known for being robust. An although I think that certain amplifiers are "safer" choices with Martin Logan and other electrostatic speakers, apparently the bulk of my worry was overblown. The amps I'd consider most capable of handling electrostatic loads without issue include: Pro amps with low impedance electronic protection Transformer-output-coupled amplifiers such as tube amps (or McIntosh products) Amps with 2-Ohm ratings for driving low impedances. Boom |
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Post by KeithL on Jun 15, 2022 15:56:23 GMT -5
First note that all of this only applies to Martin Logan's electrostatic models. Their "Motion" series are totally conventional speakers with folded ribbon tweeters. (I'm pretty sure most of their more modern electrostatic models are better behaved as well.) I would also caution one thing you said... McIntosh's amplifiers are well known for being very stable... But I would NOT bet on a tube amp with an output transformer "playing well" with the transformer in an electrostatic speaker. You're looking at a very complex and unusual load impedance... (a transformer, connected to another transformer, connected to an almost pure capacitor) Some may work very well... but some may not... and if not they could become unstable. I think I would ask the manufacturer of the amp if they'd actually tried it... or were sure it would work... Or look online for reviews or comments from someone who'd already tried it... Hi iluvboxing - I think you are probably correct. The vast number of ML electrostatic hybrid owners note absolutely no compatibility issues with their electronics. This even applies to AVR owners whose internal amps are not known for being robust. An although I think that certain amplifiers are "safer" choices with Martin Logan and other electrostatic speakers, apparently the bulk of my worry was overblown. The amps I'd consider most capable of handling electrostatic loads without issue include: Pro amps with low impedance electronic protection Transformer-output-coupled amplifiers such as tube amps (or McIntosh products) Amps with 2-Ohm ratings for driving low impedances. Boom |
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Post by iluvboxing on Jun 15, 2022 16:21:13 GMT -5
Hi iluvboxing - I think you are probably correct. The vast number of ML electrostatic hybrid owners note absolutely no compatibility issues with their electronics. This even applies to AVR owners whose internal amps are not known for being robust. An although I think that certain amplifiers are "safer" choices with Martin Logan and other electrostatic speakers, apparently the bulk of my worry was overblown. The amps I'd consider most capable of handling electrostatic loads without issue include: Pro amps with low impedance electronic protection Transformer-output-coupled amplifiers such as tube amps (or McIntosh products) Amps with 2-Ohm ratings for driving low impedances. Boom What are “pro-amps”, Boom? Personally, I’m considering the DR series to power my Aerius i’s, Logos, and Scripts. I haven’t yet decided on whether to get two DR-1s for the L/R with a DR-3 for the C/RS/LS or a DR-3 for the L/R/C. The lengthy conversation I had with Martin Logan included them advising to purchase as much power as the budget allowed; looking at the purchase as a investment because I don’t know with certainty which speakers I will upgrade to after the Aerius i’s. |
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Post by omuracada on Jun 15, 2022 16:28:46 GMT -5
Not sure if it helps anyone, however last year when I got my ML 13a's I ended up landing on 2x XPA HC-1 Mono blocks and will say I have not had a single issue with them running my 13a's (especially for the price). One day I may give McIntosh a try (Non Tubes). Please note I use my speakers for 95% movies. I like it loud and again never been a issue they sound great.
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Post by iluvboxing on Jun 15, 2022 18:02:08 GMT -5
Not sure if it helps anyone; however, last year, when I got my ML 13a's, I ended up landing on 2x XPA HC-1 Monoblocks, and I will say I have not had a single issue with them running my 13a's (especially for the price). One day I may give McIntosh a try (Non Tubes). Please note I use my speakers for 95% movies. I like it loud and again never been a issue they sound great. Yes, it actually helps me a lot because the HC-1s are on my consideration list. I’m not sure if you saw my last response to Boom, but I’m considering the HC-1s against the DR series and I’m having a tough time deciding between them. The 13A definitely don’t need the power that the DR series put out, so, I can definitely understand why you went with the HC-1s. Andrew Robinson did a great review on them recently and said the they would serve the needs of the vast majority of end users. I’m not sure if 13A’s are in my upgrade path. Short term, it’s mostly like the Classic ESL 9s which is why I’m considering the power output of the DR series. Sealed subs need lots of juice to make them hit right! |
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Post by Boomzilla on Jun 15, 2022 19:07:05 GMT -5
What are “pro-amps”, Boom? Personally, I’m considering the DR series to power my Aerius i’s, Logos, and Scripts. I haven’t yet decided on whether to get two DR-1s for the L/R with a DR-3 for the C/RS/LS or a DR-3 for the L/R/C. The lengthy conversation I had with Martin Logan included them advising to purchase as much power as the budget allowed; looking at the purchase as a investment because I don’t know with certainty which speakers I will upgrade to after the Aerius i’s. Pro amps, or "professional amplifiers" are those intended for maximum power output over sustained times and under physically difficult conditions (outside, in the rain, in 100+ degree heat, etc.), and with occasional lower than desired impedances and possibly short circuits. In order to survive such challenges, the amplifiers usually come with a variety of tools: - Cooling fans
- Short-circuit monitoring and disconnection circuitry
- High output wattage
- Load ratings (often) down to 2-Ohm loads
They often also come with two other frequent features: Built in (but not usually very high quality) Digital Signal Processing (DSP) and a tantalizingly low price per watt. Some brands sound significantly better than others. |
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Post by leonski on Aug 30, 2022 1:33:58 GMT -5
I used the word "impedance" intentionally and the power at 20 kHz and above is very low for any reasonable source. The problem I see is that the ML 11A is in the middle of ML's speaker line and many people are driving them with much less than a DR-3 with no problem. Sensitivity is rated at 91 dB/2.83 Vrms/m so not horrible (better than my current conventional speakers and much better than my old Magnepans). A quick look through some of the on-line reviews reveals a number of different integrated and power amps were used and nobody had problems driving them. If amps were routinely shutting down there would be all sorts of posts on the various audio fora and ML would be dealing with it. I really think something must be wrong with the amp or the speaker. By 'much less', donh, do you mean power? If so, that's a non-starter since virtually all amps are measured into a resistor. If you started measuring into a difficult, highly reactive AND low impedance at points load, than some more powerful amps would drop out I think a good chance exists of the combination of very low impedance at higher frequencies and a phase angle of who knows what....(but high) is making an otherwise decent amp very unhappy..... |
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Post by donh50 on Aug 30, 2022 22:47:05 GMT -5
I used the word "impedance" intentionally and the power at 20 kHz and above is very low for any reasonable source. The problem I see is that the ML 11A is in the middle of ML's speaker line and many people are driving them with much less than a DR-3 with no problem. Sensitivity is rated at 91 dB/2.83 Vrms/m so not horrible (better than my current conventional speakers and much better than my old Magnepans). A quick look through some of the on-line reviews reveals a number of different integrated and power amps were used and nobody had problems driving them. If amps were routinely shutting down there would be all sorts of posts on the various audio fora and ML would be dealing with it. I really think something must be wrong with the amp or the speaker. By 'much less', donh, do you mean power? If so, that's a non-starter since virtually all amps are measured into a resistor. If you started measuring into a difficult, highly reactive AND low impedance at points load, than some more powerful amps would drop out I think a good chance exists of the combination of very low impedance at higher frequencies and a phase angle of who knows what....(but high) is making an otherwise decent amp very unhappy..... Bit of a "zombie" post, leonski! "Much less" power, yes, partly, and generally less capable in terms of ability to drive low impedances and such. ESLs in general dip low at very high frequency, well below 1 ohm in many cases, but the signal content way up there is also very low so most amps deal with them OK. Not like Apogees that are around 1 ohm over their entire frequency range (gack!) The low energy at very high frequencies is what saves most amps, I am thinking, though modern amps handle reactive loads much better than those around a few decades ago, for sure! (Cue sound of my old Blaze Linear 700 blowing up again...) Most manufacturers test into pretty reactive loads but the results rarely make it into their data sheets. I have sometimes asked and sometimes gotten answers (heck, I asked back ca. 2007, and Emotiva provided useful data about my Gen1 amps). An ESL is basically a big capacitor, but since the signal is transformer-coupled, the HF phase angle tends to be inductive (positive) rather than capacitive (negative). That helps a lot as amps tend to dislike large capacitive (negative) reactance moreso than large inductive reactance, though large voltage spikes could cause problems. They usually have a capacitive dip someplace in the upper midrange or so (transition region for the transformer L and panel C) that can be challenging. I know and have read a number of folk driving ESLs with all sorts of amps so stand by my statement that their impedance does not seem to represent a problem for most folk and most amps. But I am sure there are some bad ones around... FWIWFM - Don |
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Post by leonski on Aug 31, 2022 2:06:04 GMT -5
Was it the 400 or 700 that had .......problems?......I thought it was the 400, and I know I've seen 'kits' of repair goodies...new boards and such of a newer design t 'fix' them. Heard it first many years go in a Pacific Stereo driving BOSE speakers.......The 901 from an early series.....Hung from the ceiling, of all things. I agree it SHOULD be in an amp manufacturers best interest to test into a real speaker. And I've seen many proposed 'dummy loads' online, but NO standards of which I'm aware. I suspect further that such a test would be for 'internal use only'......since nobody else publishes. I would suggest thee Audiograph System......Please see link... www.audiograph.se/wp-content/uploads/2018/10/PowerCube_12p_brochure_complete.pdfAs for 1 ohm Apogee? That would be the Scintilla. I think later they came out with one of a more reasonable impedance. The only amp capable of the original was from Lincoln Electric or Miller. I'm well aware of how awful many 'Stats can be. I'm not sure the very low power demand is not a red herring. After all, it is basically using your amp to charge a capacitor and by the time you do the power factor calculation, your amp is really not happy or in some cases.....capable...... |
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