Some cannot see the forest for the trees.
Martin Logan ESL Montise sterophile review, driven by Audioplax 80w tube monoblocks, also by ProLogue tube Premiums, and then by Simaudio Moon Evo 7's solid state.
Quote from the measurements by JA:
"The shape of the impedance trace will result in the Montis's top octaves shelving down when the speaker is driven by a tube amplifier having a high source impedance. This is why Robert Deutsch found that his Audiopax amplifier sounded too soft and lacking in definition."
Quote from the Robert Deutch review:
"The other tube amp I had on hand was the Audiopax Model 88 Mk.II. The Audiopax driving the Avantgarde Uno speakers is a "magical" combination: detailed and transparent to the source while minimizing the "electronic" artifacts of the reproduction process. The Audiopax-Montis marriage was not a happy one. Although the Model 88 Mk.II's rated output is 30Wpc—not that much less than the ProLogue Premium's 40Wpc—the Audiopax was dynamically on the subdued side even at moderate levels, and the sweetness and liquidity that had been so appealing with the Avantgardes now came across as too soft and lacking definition.
Next up was the Simaudio Moon Evolution W-7, a 150Wpc solid-state amp. The sound of the Montis driven by the Moon W-7 was vastly different from its sound with the PrimaLuna or the Audiopax. It now had dynamics in spades, evident as an ability to play much louder without strain, as well as more clearly present the ebb and flow of music at moderate levels. Bass was more extended and better controlled; the double-bass passages in Sylvia McNair's Sure Thing: The Jerome Kern Songbook (CD, Philips 442 129-2) were more distinct."
I have asked Roger Sanders to come to this disscusion he has cred both in ESL's and amplifiers to drive them with, so I hope he will respond. It's was posted here that he of course is biased towards his own S/S amps for esl's, but that was quickly edited out, why was that????
Cheers George |
"EPDR (equivalent peak dissipation resistance)." Que'est ce se mon amies??? [What does it mean my friends?]"
It is used by technical measurers like Keith Howard of HiFi news & Record Review, and John Atkinson of Stereophile when they review and then measure speakers. Because just a low impedance measurement does not reveal all that the amplifiers is seeing as a load.
The lowest EPDR (combind resistance and phase angle) of say the Wilson Alexia when measured by Keith Howard of HiFi News was a low impedance of 1.8ohms at 65hz and a lowest phase dip of negative -40degrees also at 65hz. These two measurements combined gave the Alexia a load to the amplifier of .9 of an ohm at 65hz. Big difference to just 1.8ohm resistive load.
You can read all about it here.
http://www.absolutesounds.com/pdf/main/press/WA%20Alexia%20HFN%200313-4web.pdf
Cheers George |
Yes Twb2, unless your prepared do your homework to get the right amp with ELS's, they will be a comprimise at the low impedance + difficult phase angles frequencies, as Roger Sanders ( in his White Paper http://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors ) and I have outlined a few times above, that many tend to be blind to.
Here are two more and there are many more on all brands of ESL's
Martin Colloms from HIFI Critic Report on the Quad ELS-2805:
"Amplifiers with more
than 0.6 ohms output impedance (which most tube amps can be) will cause shifts in tonal
balance, namely recessed over-sweet treble, and some
degree of lower midrange boom and bloom."
And also Keith Howard from HIFI News report on the Quad ESL-2912
" Impedance phase angle at low frequencies
is high enough to lower the EPDR (equivalent peak dissipation resistance)to a minimum ohm of 1.4ohm at 69Hz, but as the ESL- 2912's impedance will be level-dependent at LF the dips to 3ohm modulus at 7.5kHz and to 1.6ohm EPDR at 11.lkHz are more relevant and suggest a moderately difficult amplifier load."
Cheers George |
"That, coupled with the normal brightness associated with solid state amps'
That is a massive overgeneralization, and should be totally ignored.
"its easy to see why- it is common that the amplifier will be trying to make nearly 10x more power at 20KHz than it might be at 50Hz!"
Doesn't mean it's giving 10x the spl at those frequencies, it means it's staying linear and a have a flat frequency response into those load/s and frequencies.
If that were the case nearly every Solid State amp with good current ability would blow ESL's sky high at high frequencies, get real!
Cheers George |
Frogman: You know I hope that most SS amps have a lower output impedance than most tube amps.
Here is a quote from Roger Sanders of ESL fame a white paper on Solid State v Tubes for ESL's.
"This impedance problem is relatively minor when dealing with conventional, magnetic speakers. But an electrostatic speaker is an entirely different animal. An ESL is a capacitor, not a resistor like a magnetic speaker. The impedance of a capacitor is inversely proportional to frequency. Therefore the impedance of an ESL typically varies from around 150 ohms in the midrange to about 1 ohm at 20 KHz.
A tube amp will be able to drive the high impedance frequency bandwidth (the midrange and lower highs) of an ESL with linear frequency response. However, at higher frequencies, the impedance of the ESL will drop below the impedance of the amplifier and the amp will then roll off the highs to some degree depending on the exact impedance mismatch and the frequencies involved.
I think you can now see why I prefer very high power, solid state amps without any protective circuitry for driving ESLs. This is because they can drive ESLs with linear frequency response, while tube amps roll off the highs."
You can read the whole White Paper here:
http://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors
Cheers George |
Rodman999999 You mis-read my statement on I vs R.
I said "that can almost double", the app word being "almost" you read what you wanted to see.
And here is the advertised specs of an Australian amp called and ME1500 and yes it can "almost" double all the way down to 1ohm 220-8 430-4 800-2 1500-1. And thats both channels driven at the same time!!
http://www.me-au.com/ME_1500_data_1.jpg
http://www.me-au.com/ME_1500_data_2.jpg
And even the smaller ME amps do the same amount of "almost" doubling. Show any Mosfet that can do these kind of figures, and like I said I'll show you a case for false advertising.
Cheers George |
Sorry but Mosfets can't do current like BJT's can. They can do watts no problem though.
Show me published specs on a Mosfet amp that can almost double it's "tested" watts output all the way from 8 to 4 to 2ohms and I'll show you a case for legal action.
Cheers George |
Frogman: "original Quads driven by Levinson ML2 sounded very good."
And what you would have also heard was a more defined and extended treble because those quads and these (ML's Acustats and other els's) go below 1ohm in the treble and start that impedance dip at 10khz.
Tubes I aggree with these speakers still sound good but they are definately subdued in the treble compared to a GOOD s/s amp that is BJT output and that can do current into low impedances. Like you found with the ML2 which can almost keep doubling it's current down to 1ohm for each halving of impedance.
Cheers George |
12-10-13: Bombaywalla: RE: Stereophile review of Green Mountain Speakers driven by OTL:
They may have given the speakers themselves a good review, but not when it's driven by an OTL amp. And it's those impedances/phase that cause it to act like a tone control.
Stereophile: Listening review of the Green Mountain Diamantes, half way down the page.
http://www.stereophile.com/floorloudspeakers/694green/index.html
And then the measurments by JA to back up what SS heard, first paragraph:
http://www.stereophile.com/content/green-mountain-audio-diamante-loudspeaker-measurements
Cheers George |
"increased emphasis of the upper treble"
Not right, "emphasis" is the wrong word it will give a flat response through the audible frequency range and cannot boost at these frequencies thus will not be effected.
And yes it will have more presence than an amp that is curtailed in these harder to drive areas because they cannot deliver the constant voltage because of limited current.
Just read and try to understand Roger Sanders WHITE PAPER on the subject.
http://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors
Cheers George |
Mapman: "Over sweet treble and midrange bloom"
You forgot to include the word "recessed" you guys are just too much.
Cheers George |
Beside Roger Sander answer above in my last post which the non believers are conveniently blind to.
Here is and excerpt from the Stereo Times review of the difference when driving the Quad ELS2805 (while still hard to drive are easer than most ESL's) using tube then good solid state. Which also backs up everything Roger said in his White Paper and I've been saying and heard.
Stereo Times:
"The Quads are not as easy a load as one would be lead to believe by how good they sound with tube amplification. The Magtech further revealed the tube shortcomings (which I had already noticed) by expanding the peak performance range of the Quads. The “sweet region” grew to the limits of the speakers themselves. Meaning they suddenly didn’t have extended bass but what they did have was tighter and more refined. The top end was not more extended, just smoother and less brittle. The Magtech amplifier did not create new loudspeakers; it just let them be all that they could be."
Cheers George |
"12-09-13: Bifwynne
George, I did a web search for an article that explains EPDR."
Good to see someone is starting to grasp it, I posted (link) 2 graphs of the B&W802D one that shows the impedance and phase angle as separate measurement lines, and the other graph in red that shows them combined to give the actual EPDR load the amp is seeing.
Note the big difference at 60hz and at 700-800hz where the load the amp sees, drops to almost 1 ohm (EPDR) from 3ohms (non EPDR)
http://www.stereo.net.au/forums/index.php?/topic/59228-class-d-amplification-explanation/#entry1010538
And look at the Wilson Alexia comment as well.
Cheers George |
I recieved an email from Rodger. (below in parentheses)
Roger Sanders ESL and amp guru is not one to get into heated debates on forums, this is why he has presented his white paper on the subject as simply as he knew how, so it can do the talking for those who can understand it.
So if this is wrong by anyone, a white paper should be done by the "one" who has the so called "knowledge" to oppose it. So he can also be then be also laid bare for all the audio community to view, like Roger has done with his white paper.
"Hi George,
I completely agree with your assessment of the tubes vs. transistors controversy among audiophiles.
Transistor amps are the only type that can produce linear frequency response and high output when driving ESLs. But getting audiophiles to understand and believe the technical reasons why this is so is difficult. You have your work cut out for you -- but I support you 100%.
I hope that posting my white paper will help some audiophiles gain a better understanding of amplifiers. I do not have the time to post on forums. And in any case, I am not interested in getting into arguments with audiophiles. So I will not be making any posts.
However, any interested individual may feel free to contact me directly if he has any questions."
Great listening,
-Roger"
Cheers George
|
These links will get you there better
B&W802D EPDR load
http://www.stereo.net.au/forums/uploads/monthly_12_2013/post-106386-0-82896500-1386705003.jpg
B&W802D non EPDR load
http://www.stereo.net.au/forums/uploads/monthly_12_2013/post-106386-0-58273700-1386705013.jpg
Cheers George |
Bifwynne
EPDR is not simple to work out you need Matlabs program that cost + the equipment to measure both parameters, unless you know the resistance and phase (which Stereophile do give) then all you need is the program.
Here is a link to the EPDR discussions on Stereophile with John Atkinson editor who's not using it yet and Keith Howard who does uses it from HiFi News & Record Review.
http://www.stereophile.com/content/epdr-wheres-formula-footnotes-1
Cheers George
|
No he didn't he, used the word "increased emphasis" where he should have used the word "linear", as in flat in regard to frequency response.
Cheers George |
Mapman, most Class D's I know off and some I have tested are greatly troubled by loads that go under 3-4ohms, and ESL's can dip to below 1ohm.
Cheers George |
"Frogman: Georgelofi, thanks for the link and I am glad that you found what works for you."
Like I said, I even liked the sound of tubes into ESL's, but when you hear the extension and dynamic presence that's missing with tubes once you've heard a "good" solid state BJT (bi-polar not mosfet) output stage amp into them with lots of watts and current, you will think hard about what's missing, but then maybe you like that subdued rolled off top end.
It's not what works for me, it's fact, and electronic maths made up of Ohm's and Kirchoffs Laws, there is no voodoo involved.
Stated by one of the masters of ESL's design Roger Sanders that I quoted from the white paper I gave the link to. Here again in case you didn't fully read it.
http://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors
Cheers George |
You forgot to mention Dhcod that they also dive down to below 2ohms as well. And don't go by the Stax published impedance graph, it's fudged quite a bit, we measured it and it's far from what they pictured. Add to that it's capacitive loads and you have a speaker that is easy to drive at some frequencies and a down right pig at other frequencies.
And a quad esl 57 is even worse. And other ESL's are just as bad if not worse again, look at the Martin Logan Montise crazy amp impedance load and add to that the nasty phase angle, amps with current need only to apply.
http://www.avsforum.com/t/1454033/amp-for-electrostatic-speakers post number 12
http://www.stereophile.com/content/martinlogan-montis-loudspeaker-measurements
For over 40 years I've only used ESL's
Quads, RTR's, ML, Acustat, Stax. Sure some of my big tube amps will sound good into them, but nothing drives them like a strong current bjt output stable solid state can. Direct drive esl's can also sound good but that's getting into the deadly territory
Cheers George |
Play yes Atmasphere, but really you and I both know they were not able to give a flat 20hz to 20000hz into those hard loads.
They acted more like they had tone controls in them and made the FR look like a dogs hind leg.
I have a old friend that has two pairs of Stax F81's and not even his mighty Rogue Magnum 150 monoblocks drives them as well and with flat FR with a vice like grip as a good stable BJT amp can, like the big Krells and such.
Cheers George |
Just the Quad ESL57 impedance curve, my ML's and Acousats are even worse when I measured their impedances.
http://www.quadesl.com/quad_main.html
and add to this the highly capacitive nature of ESL's, and you can see why Roger Sander says Solid State is better than Tube or OTL Tube for ESL's
The only tube amp which is great match and is not worried by these impedance drops is High Volatge direct drive tube amps (up to 5000v at the speaker terminals). For ESL's like the oringinal Acoustat X. But these are difficult and hard and make safe. As you can imagine.
Cheers George |
Frogman hi, the Moscode 600 you mentioned not being able to drive the ESL's very well.
I believe that the Moscode 600 is a hybrid employing Mosfet output stage, even though it has a lot of watts!!, mosfets don't do current like a BJT (bipolar)output can
This is why it wouldn't drive the ESL's, as with ESL's the impedance curve can dive to below 1ohms at places and very capacitive as well, and for this a solid state amp should have a BJT (bipolar) output stage that is high current and be very stable into capacitive loads.
Cheers George |
Here are just two speakers that are not a good match with tube amps the Infinity Kappa 9 and an Acoustat not shown is the phase angles which can make them even worse as seen by the amp.
http://www.rageaudio.com.au/index.php?p=1_12
Note the low impedance dips (left scale) at 2ohms and down to .5ohm and at what frequency (across the bottom), this is where tube amps will have trouble. (right scale is the phase in degrees not plotted) when this goes into the minus figure with low impedance together then it can become an amp killer at that frequency.
Like this graph of the the Genesis 5.2
http://www.stereophile.com/content/genesis-advanced-technologies-52-loudspeaker-measurements
And this one of the magico Q5
http://www.stereophile.com/content/magico-q5-loudspeaker-measurements
This one of the Sonus Faber
http://www.stereophile.com/content/sonus-faber-cremona-elipsa-loudspeaker-measurements
Cheers George |
I need to point out to you Bombaywalla that this Green Mountain speaker is far from being a hard load, if fact it's quite easy.
As it's a 6ohm average with a not so bad phase angle of -30degrees.
The worst load frequency for an amp happens where they cross at 100hz where the impedance is 6.5ohms with -25degrees phase angle.
So this speaker can be regarded as quite an easy one for amps to drive.
Cheers George |
