Your Mytec below measured by Stereophile, could even get it up into 2ohms at all. Stereophiles JA’s summation, "practical use with speakers whose impedance doesn’t drop below 3 ohms."
No good at all with the OP’s speakers we are talking about here.
245W into 8 ohms
315Wpc into 4 ohms
when I tried to measure the clipping power into 2 ohms, the Mytek went into protection mode at 310W (18.9dBW),
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My original point George was that you never accept anyone's experience with Class D as valid
And why should I, if you search I've listened to plenty, I will go with what I hear and what independent measured results show about their ability into these sorts of loads, before I ever believe your subjective opinion on them, you've probably never used on on this sort of "evil load" speaker. As history shows you keep starting Class-D threads to get some conformation or reco on what you hear yourself, because "maybe" your not too sure about Class-D |
Please don’t post your own misguided words and say they are mine, your just showing your own stupidity, and this sort of thing is not called for on these forums
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@georgehifi ,
Can you just drop down the level of sarcasm and argumentativeness a couple of notches?
Bob
I would if it wasn't warranted, and usually do. |
George who holds up the Levinson ML2 as the paragon of excellence for technical specs.
This Stereophile’s JA’s statement, is the typical case where a 25w amp like the ML2’s with doubling capable wattage current will drive a pig of a load like these Alexia’s and the OP’s speaker "to a given level" with perfection better than any 3000w class-d can. John Atkinson Stereophile Test
This speaker will play loudly with just a few watts. However, it demands quite a lot of current from the partnering amplifier. |
We finally got him to install a pair of ZERO This is just trying to save face. Of course you did, an expensive band-aid fix, that will never get the best from the Alexia, instead of pointing him in the right direction for the right amp even at the cost of maybe an OTL sale. This Wilson Alexia "customer", was sold totally wrong amp for these speakers that have a pig of a load. That with the right amp eg: Gryphon Antilion and similar current pushing demons, will make them sing at all levels. I know as my friend Edgar Kramer owner of Soundstage Australia, owns a pair, and we’ve tried many amps on them, believe me "NO OTL" will drive them anywhere near their full potential, even with a Zero autoformer. https://www.soundstageaustralia.com/index.php/reviews/84-wilson-audio-specialties-alexia-series-2-loudspeakers John Atkinson Stereophile Test
This speaker will play loudly with just a few watts. However, it demands quite a lot of current from the partnering amplifier. HiFi News Lab Report
The impedance and phase angles falls to a scary 0.9ohm!! in the lower bass Now back on topic to the OP’s problem of driving his Thiel CS5’s which maybe an even worse/similar load as these Wilson Alexia’s. "Here's a thought!! maybe the OP needs some OTL’s"??????????? |
Our OTLs do a nice job on the Alexia, You’ve now got to be joking!!, out of courtesy I didn’t mention which OTL’s wouldn’t drive these 89db JBL’s 1400’s, but now you leave me no option, they were a pair of your M60’s!!!!! and now your saying they’ll do a nice job on Wilson Alexia!!! ???? Probably the hardest speaker know to man to drive. This is just getting too ridiculous for words https://forum.audiogon.com/posts/1803629https://forum.audiogon.com/posts/1804702 |
All I’m talking about is the OP’s Thiel CS5’ speakers and today’s similar speakers like nearly all Wilson Alexia ect ect and what will drive them the very best into those varying low impedance’s they have. And that would be one of the linear bjt output brutes, with a power supply big enough that can power Lower Manhattan, ( read that in Stereophile somewhere sounded good). And no Class-D I know could as do it as well not even the 3000w!!! Behringer. The old Mark Levinson ML2 (BJT monoblocks) at just 25w would slay it for sound quality and control "to a given volume". https://ibb.co/X5rfnXLCheers George |
mcreyn
You are treading on thin ice, publicly questioning moderators decisions, I've seen one other removed from these forums for this. All submissions, whether they be questions or answers, are subject to moderation. Any designated moderator will have to the right to remove content that he or she deems inappropriate.
As for your other question, go listen to a pair of 25w ML2 monoblocks, doubling is your key to which sounds better at the 2ohms "to a given level". Not which sounds louder, a PA amp at 3000watts will do this, such as the Behringer NX3000 will do it for just $299 go buy one!!!. https://www.parts-express.com/behringer-nx3000-ultra-lightweight-class-d-3000w-power-amplifier--248-7012
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Give up Ralph, a good BJT amp will always drive into these sub 2ohm low impedance’s and do the wattage doubling act better than a Mosfet Class-D even GaN based one The best linear amps that can do it are all BJT M.S Electrical Engineering, University of Southern California (2017) Pros for BJT:
BJT’s are capable of handling higher output currents for signal outputs and can have lower output impedance in amplifiers intended to drive a low input impedance load or deliver significant amounts of power, this is a huge advantage.
Cons for MOSFET:
Can’t drive a low-impedance load very well. And there’s plenty more, I’ll posting them till the cows come home. Please show just one from any great known amplifier designer (beside you) that says the opposite! |
Wow! your really pushing it, think it's time to zip it. |
Why oh why would anyone make a speaker with a 2 ohm load? It makes no sense. Some of the best speaker ever, have loads like this and even worse, that’s why they are some of the best. EG: Wilson Alexia 0.9ohm in the bass and many others. I couldn’t even be bothered to tell someone like you any more because you’d be deaf to it, as all your interested is selling your own Class-D IcePower 1200AS2 modules that have a woeful phase massive shift of 70’ degrees!!! between 7 to 15khz!!!! No wonder Class-D detractors complain about the uppermids/highs so much. https://ibb.co/JdrgGBH |
And you believe all he says, I believe my own findings and an Electronic Institute before any manufacture spruiking and trying to make a buck. Once again here is one main difference why a Class-D with Mosfet will not drive into a hard speakers load like the OP’s Thiel CS5’s like a good linear amp like the ones I have suggested with BJT (bi-polar) output stage. And Class-D’s don’t come in BJT From Electronics Foundations: Semiconductor Devices [Lecturer] BJTs tend to have better, more linear gain characteristics…and can give you a lot higher voltage gain than MOSFETs.…They’re also able to handle higher output currents…and have a lower output impedance.…That gives BJTs a huge advantage over MOSFETs…for building amplifier circuits…that need to provide a significant amount of output power…and or drive loads that have low input impedance.…MOSFETs are going to have a harder time…driving a low impedance load…because they have a higher output impedance.… |
Your defiantly not worth the time or effort, I said search and you find out. |
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Well you have just made yourself look like a total ? Read again and take it in, I didn’t say I built Peter’s amps who is a long time mate, and not at all in a good way. I said it’s what I’m using at the moment, mcreyn get a life, really!!! |
George so you are a vendor? I thought you weren’t promoting anything I manufacture a product that I don’t mention unless asked about. Doesn’t mean I can’t talk about anything else or suggest other products. Are you genuinely interested or maybe just ****-stirring. |
find out whether the phase shift has any relevance in your listening. If you believe there nothing to hear when you have 70 degrees phase shift at 5khz and still 50 degrees at 2khz!! then there’s no hope for you. https://ibb.co/JdrgGBH I have heard class D amps that sound euphonic/rolled off in HF, and others that sound harsh. All because of the setting of the switching frequency output filter and where it acts, either "too high" or "too low" "rolled off in HF" (too low) , and "others that sound harsh" (too high), with today’s 500khz switching frequency. Raise that switching frequency 3 x to 1.5mhz as you can with GaN, and you’ve got rid of the problem because the output filter can then also be raised 3 x higher, and then you don’t get that phase shift so low down into the audio band or the problem of as you say ("rolled off in HF, and others that sound harsh"), because the filter then can be set to do it’s job fully and rid the switching frequency completely and not effect the audio band with phase shift. It’s that simple, even the most technically inept should be able to understand, maybe! Or you can believe the ones that are trying to tell you it doesn’t matter. From day one Class-D has had this problem, because of it’s low switching frequency/filter. |
design your own amp, send it to me
You just need to search buddy, I’ve built some of the biggest pure class-A solid state that were water cooled, one that was a three man lift, explained in great detail in Audiogon and other forum pages if you could be bothered looking.!! This is what I use at present https://ibb.co/zNMMnpThttps://ibb.co/8XqKvJd |
Are you serious! You buy it and drive the Op’s speakers then
You are really in a world of denial. if you think this Class-D can out drive the 25w ML2’s "to a given level into these OP’s speakers."
I’ll lay money on it also that those watts are not real or RMS, would be nice to see some independent test, at 8,4,and 2ohms
You buy it and live with it, because you obviously think 3000w can sound better than 25w into the OP’s extremely hard to drive speakers.
It’s like saying a 1/4mile dragster with 8000hp can get to the top of Pikes Peak hill climb faster than a 100hp rally car, delusional is the only word, even the most technically inept on these forums would think so.
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joysjane That’s right, it doesn’t matter how many watts you have, if you don’t have the current to back it up all the way down into 2ohms and less, with speakers like the OP has in the bass, you got s**t. Like I said the "puny" 25w Mark Levinson ML2 monoblocks will slay them "to a given volume level" Cheers George |
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1. Get a Class D amp.
2. Find some Kappa 9’s.
3. Set the the switch in the rear to Extended.
4. Crank up the music.
5. The Class D amp that doesn’t shut down will drive a 2 ohm load.
I can say this after completion of the above five steps,
This is gonna be one very short list of Class D amps Crude way, but effective. Better to just see how they behave in tests not understated into 8,4, and 2ohm and see if they can do "close" to the doubling act for each halving of the impedance. My answer to the posted question,
Stay away from Class D amps to drive low impedance speakers. Excellent advice. Many manufacturers just under specify the 8ohm rating to allow their product to be in spec for the lower loads. Yes this must be observed, as many "cheat" by understanding the 8ohm or the 4ohm watts, just so the 2ohm look better. If all above is not taken on board, just buy a 3000!watt Class-D for just $400 and see how you go. https://www.storedj.com.au/behringer-nx3000-ultra-lightweight-3000w-class-d-power-amplifier Cheers George |
Keep it up Ralph, your not doing your Class-D venture any good service, by trying to pull the wool over people's eyes.
There are far better linear BJT amps around than Class-D's for driving sub 2ohm impedances, all one has to do is look what happens to the Class-D's Stereophile tests when they do 2ohm load testing, some times they don't even try because they know it cant take it. |
George’s arguments are irrational. For him doubling down power is more important that the absolute power and current the amplifier actually gives. Sorry but this is wrong, have you ever listened to a pair 25w Mark Levinson ML2’s on a pair of hard to drive speaker like the OP’s? "to a given level" (because they are only 25w after all) they will annihilate any 500w or 1000w Class-D. This proves that doubling down (current) to below 2ohms into this kind of speaker load is the most important factor for sound quality, not wattage!. ( otherwise we would all own $400 3000W! Behringer NX3000 Class-D’s )
https://www.storedj.com.au/behringer-nx3000-ultra-lightweight-3000w-class-d-power-amplifier
Although if you want to go louder then wattage becomes a factor also, so then the same kind of amp that can double with more watts is needed then. So you my friend are the irrational one not me. BTW You’ll never see a pair of ML2’s for sale used as owners die with them! |
Wake up and smell the roses. This is it for me, as this thread has just become a hand full of manufactures/retailers trying to make some $$ from their new ventures into Class-D Just look at any of the many Class-D test in Stereophile, when they test bench a Class-D with 2ohm loads, they either crash and turn off, goes backwards in watts compared to 4ohm, or it just current limit and s***s themselves. BYE BYE https://www.sccpre.cat/mypng/detail/275-2758889_emoji-world-bye-bye-emoji.png |
This statement is false. The ability to double power as load impedance is halved has nothing to do with how well the amp will play bass Of course it does when it demands current into low impedance to do it, get over it.! Ralph you’re so transparent. Stick to what your good at, super efficient easy to drive horns that you heavily promote and your OTL’s, that can’t drive these kind of sub 2ohm inefficient speakers that you have no love for. But then yet in the same breath, promote the use of your OTL’s with them, with expensive Zero autoformers, saying that their great and the perfect answer for your OTL amps to use on these hard to drive speakers, just to make some more dollars from the gullible. All your doing here, is to branch out into the Class-D gravy train $$$’s (so transparent) without any loyalty to where you came from, OTL’s and horns. But then they are both a dying breed. |
I did unfollow, but I got this one before. definitely gone now.
Look at complimentary BJT’s with massive power supplies that I’ve been suggesting for these loads, then look at your Class-D Mosfets usually not complementary as the P channel stinks, then the 8th grade maths don’t mean ****.. |
Put the shields up Scotty, we’re being attacked save the Enterprise at all costs.
On these OP’s speakers with the minuscule 25w ML2 monoblocks will do bass and everything better to a given level, than any Class-D can, and that’s because of the current it can keep supplying down to 1ohm
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George, the quote above suggests that you do not understand how a voltage source works Yes you use this old chestnut everytime as it suits you to bring it out every time your OTL’s are brought into question doing the same thing. So it’s simple for all, instead of doing war and peace to confuse everyone as he usually does. dsper OP here’s is the proof, Thiels CS5 that have impedances that reach down to below 2ohms will get "driven" and sound far better "up to a given level" with the 25w!!! Mark Leveinson ML2 monoblocks, but certainly not louder than 1000w, 2000w or even 3000 watt Class-D amps, because the ML2’s can do the doubling act into lower impedances right down to 1ohm |
what’s wrong with efficient easy to drive horns? If you need to ask that, you should delve into the measurements of both a bit To have that efficiency and easy load ability. Measurement tests show they are always compromised when compared to a highly tuned speaker eg Wilsons ect ect, that will be far more inefficient and much harder load, that yes need far more serious drive characteristics from the amp/s Bit like comparing a high octane highly tuned multi cam/valve Ferrari V8 motor, to a low octane V8 Ford iron slug from the 60’s. Cheers George |
dsper OP
I emailed, to both Nord and Appollon, the Stereophile measurements for the Thiel CS5’s and both suppliers said that their amps would drive them. (Without seeing any independent tests) Of course they did, they want a sale. No one disputes that they can’t drive the Thiel CS5’s to a point, just if they don’t try to double from 8 to 4 to 2ohm, you won’t get the very best out of them, they will be compromised in the bass, if you don’t mind that that go ahead. But not if you drove them with amps like the ones I have described, that can come close to doubling wattage all the way, from 8, 4, and 2ohms, I believe the Thiel’s are worth the right amp to make them sing top to bottom, don’t you?? it’s up to you. Cheers George |
Sorry but what you get is a good PA amp. Hypex suck in, they purposely put things backwards to confuse at glance. Look again, and that’s peak watts and amps, also the wattage go backwards as the impedance goes down, it gets severly current starved. Nowhere in this universe can this thing come close to doubling into 2ohms The NC400 of theirs is a far better module as far as current delivery into low impedances it actually goes up in watts instead of down. Data sheet download here https://www.stereo.net.au/forums/applications/core/interface/file/attachment.php?id=480207Cheers George |
Our preamps can drive such low input impedances-
Of course it can, how did I know that was coming, stick with tubes, your good at it, and built your rep on them. The fact is this amp without buffer it has around 15db of gain around the same as the Nelson Pass First Watt F5 and with today’s high output sources and preamps, in most cases you don’t need another soul destroying opamp buffer in the signal path with or without gain. Here is the comments from a manufacturer of these Purifi’s Class-D amps when I queried him on the unnecessary low 2.2k input impedance. I think it could be because of the use of bjt input stage instead of fet, I’ve yet to suss that one out. Yes you are absolutely correct that you can use a high output DAC directly into this module. "That would be the ultimate solution"
And I am considering a buffer bypass mode. However most power amps will have gain in the region of 26dB to account for sources down to 2 Vrms. A typical DAC straight in is a good solution with digital volume Most digital sources today have far more than 2v and owners preamps can certainly have enough for the Purifi without another buffer. As Nelson Pass with his F5 said " If you need to turn the gain up on your preamp, then do so." Cheers George |
Whatever Ralph.
Seems like this could be the module your using, as you've turned up the force shields a notch higher on this one, if so just go with the buffer by-pass switch. |
Custom buffer adds gain and increases impedance to 47k ohms. There’s no need for it in many cases, as sources and preamp have enough gain these days. It’s just "another opamp in the signal path" that’s not needed in many cases if the input was high enough instead of 2.2k, who wants that in hi-end if it can be taken out and one less opamp yay!!! gotta be good for the sound, and the business. I think that’s a very legit observation or "complaint" as you would put it.. |
Purifi 1ET400A has no buffer, so it is expected to a manufacturer to add a custom buffer, and add more gain as needed. It also has a disappointedly low 2.2k input impedance, so the use of most capacitor coupled (unless >10uf) preamps, tubes, or solid state or passive preamps direct in are out of the question if no extra gain is needed, which with today’s sources giving so much higher output, no extra gain is needed, so then neither would be an opamp buffer. And if more gain is needed then a direct coupled opamp smd buffer is the only obvious option, again not capacitor coupled, solid state or tube buffer otherwise a massive 10uf coupling cap will be needed into that 2.2k input impedance. WHY!! they keep making low input impedance amps these days is beyond me, go back to 48k (the once recognized industry standard) or even 100k like it used to be with tubes, makes for a whole better range of preamps ,tubes SS or passive able to drive them properly. Cheers George |
I did see this:
Output Power, Short Term
8ohm, 1% distortion = 227 watts
4ohm, 1% distortion = 450 watts
2ohm, 1% distortion = 450 watts with a footnote stating "Power is limited by overcurrent protection system (OCP) and highly dependent on thermal conditions."
Not sure what the footnote means. Amps goes self into destruct mode if current limiting doesn’t work, no other reason for it to be limited, unless purposely done to sound bad into those low loads? Cheers George |
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the Bryston 14BSST would go into protection mode from overheating due to the impedance. With these sorts of speakers like the CS5 ect it’s no wonder, these tested figures show it was definitely no current master into low impedances 8ohm load 690w 4ohm load a reasonable 1000w 2ohm load it barely got off the 8ohm mark at 720w, very sad. Cheers George |
We all know George will be first in line.
Having a dig are we? well at least you’ve got that one right sunshine. I’ve never been against Class-D, just it’s two Achilles Heels I have a big problem with, switching frequency and dead time. Which gives it that " Plate glass transparency" that you call it, I call it "sterility" and missing harmonic decay. I’ve always said, ever since I started the the debate about the new GaN technology here way back, that when the GaN Class-D amp becomes affordable to me, with what Technics has done with the SE-R1 with using 1.5mhz switching speed, I’ll be the first in line to get one, and ditch my inefficient hot boat anchors, door stops if you don’t live by the sea. he’s able to make them reasonably priced since I get the feeling I’m going to be a future customer. Judging by his offsider Tweak1 by another maker here, that’s going to cost you far bigger than it should. https://forum.audiogon.com/discussions/which-class-d-amplifier-ps-audio-ghent-nord-merrill-or-other/... |
At 10Hz it is approximately .6 ohms.
That when the vinyl warp frequency will tax an amp, or even a bit of dc servo flutter when the mains chucks a slight wobbly.
It's been reported that Jim Thiel ended up using Krell 600 Watt'ers.
Correct type of amp, that will almost double down to 2ohms without breaking a sweat, though the 250 or even 150 watt'ers would do, they all can do the Krell doubling act. There are many other brands that do the Krell doubling act also, all use Bi-Polar (bjt) output transistors, just like the Krells. Cheers George |
Theta Digital Prometheus -
8 ohm - 250 W
4 ohm - 500 W
2 ohm - 850 W Yes another one beside the Spectron (which is yet to be independently tested) that "can" get the watts up into 2ohms, but this is at a cost. JA’s Note: " However, the distortion rises considerably into 2 ohms" BTW: Note! Both use Linear power supplies that’s why they’re big/heavy for a Class-D >20kg. No smp power supplies here, that’s a good thing. Cheers George |
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I have driven my 1 ohm Scintilla’s with the NC400 mono blocks from hypex.I use them sometimes in the summer months when it gets to warm for my Krell KRS100 mono blocks My friend also has the Scintilla’s, what a great speaker when driven right. With this https://ibb.co/mSV04BPhttps://ibb.co/m6LhhPc 1st post, bet you can’t wait for winter, otherwise you wouldn’t still own the Krells. It must be because they sound and drive the Apogee’s better by quite a margin, otherwise you would get rid of them? Also there are cooler running Krells, that would sound almost as good as the 100 mono’s, and still blow away the NC’s on these great speakers.. Cheers George |
it does not double the power when halving the impedance - but it is apparently stable at 2 ohm
No it’s "not bad" for a class-D, nowhere near doubling still, at least it goes up as the impedance goes down, too many either don’t go up at all at 2ohms or go backwards. "Could" be ok for the OP’s speakers if it's to be believed, and "may" get the best out of the low impedance bass they have. 600 Watts at 8 Ohms 800 Watts at 4 Ohms 1400 Watts at 2 Ohms It will be interesting to see with independent tests if they give it to someone like Stereophile, if they have "underquoted the 8ohm and 4ohm" to make the 2ohm look as good as it is. As many manufacturers are doing that now, that you can see that on Stereophiles bench tests, it one way of making the amp look to be doubling, and it’s wrong (lying) and should be stamped out. Sorry - the specs above are for stereo single amp - the power is considerably more in mono block configuration If these are bridged stereo’s into mono’s? (probably as they give no specs) if so they won’t even do as good as the stereo amp in doubling down. Cheers George |
What I’ve learned lately on this thread is to avoid using speakers that present loads to the amp of less than 2 ohms. What can be the case, is these speakers can be the best measured/sounding ones, why drive them with amps that can’t do them justice. As for flipping the bird to amp manufacturers, only when it’s warranted because of not saying how it is, or recommenders of them that have no idea what they’re on about. Because they the manufacturers/recommenders would have "you" believe if an amp with 800w can drive a speaker that’s "inefficient" and with a "average impedance loading". Then that same amp can also drive a speakers that are "even more efficient" but with a "very hard impedance loading". |
why can't discussions of audio stuff, hifi stuff and music listening stuff, be non confrontational ?
really you have to ask this?? Because there's way too much BS and Voodoo in hi-end audio Mr D Cheers George |
Spectron Musician III mk2 mono blocks - I believe they will provide around 300 watts at 1 ohm - or it might be at 0.5 ohm - Once again this means nothing, give us the clipped wattage at 8ohm 4ohm and 2ohm and 1ohm, only then will you know if it's being current starved (sagging). Cheers George |
and can handle speaker impedance loads under 2 ohms, dsper That statement it’s should tell you something, they "can handle" a 2ohm load. My car "can handle" being reved to 8,000 rpm. My hands "can handle" 60c on a Class-A heat sink for a few seconds! Your speakers are at 1-2ohms for nearly 3 octaves in the bass "JA which means that the amplifier with which it is used must have ample—to say the least—current capability if the sound is not to become anemic." Like I said above " find yourself a Krell type ect linear amp/s with BJT (bi-polar) output stage, with high bias Class-A used somewhere to get the best from your highly regarded speakers." Read these amps that were tried and you’ll get an idea of what’s needed to get the best from your speakers. . JA Stereophile.
" The best one I heard was the Krell KSA-250 (their latest product—though by the time you read this there will be a KMA-600), followed not too far in second place by the older Krell KSA-200.
The newly arrived Threshold SA/12 monos had plenty of overall power, but lacked the drive at the low end possessed in such quantity by both Krells, and had a refined, neutral upper range that seemed to leave the Thiels lacking in sparkle.
Until now, my favorite overall amplifier has been the Mark Levinson No.20.5, but it simply didn’t have the low-end punch necessary to bring the CS5 to life" Cheers George |
