The big Krell current wattage doubling grunt is not really fully utilized here, great sounding amp still with these speakers just a bit of overkill. Apogee Duetta 2 is one speaker that doesn’t need so much an amp that can "nearly" double all the way down to 2ohms from 8 and 4 ohms. Because it’s load impedance is very benign lowest at 5ohms, https://www.stereophile.com/images/archivesart/Duetfig1.jpgBut as you say it’s efficiency is only 80db and this just needs lots of watts, even high wattage Class-D and or linear Mosfet poweramps will suffice into these speakers. Cheers George |
Like I said, impossible to exactly double. And understating the 8ohm wattage figure
But these are better "close to doubling" figures down to 2ohms than any Class-D’s or even linear Mosfets with complimentary push pull output stages can achieve.
The Momentum comfortably exceeded that rating, clipping at
405W into 8 ohms
640W into 4 ohms
1115W into 2ohms
And yes Dan D’Agostino’s Krells, and the Momentum’s are powerhouses, that others claiming to be and can’t should try to mimic.
Cheers George
|
invalid, georgehifi,
Please show/indicate to me where the ’incorrect’ or ’misleading’ information is.
No need to get your knickers in a knot, the only way to prove it is with independent testing, and not believing the manufacture Like I said bet the 8ohm is under quoted just like his Progression Monoblocks are below. Progression Mono: D’agostino specs 8ohm- 500w 4ohm-1000w 2ohm-2000w Stereophile tested specs 8ohm-595w 4ohm-943w 2ohm-750w (went into turn off protection mode) It’s impossible to double exactly there are always losses, if it did it would be saying it’s like inventing perpetual motion. Cheers George |
Better amps have very robust power supplies that can provide the extra current required to double the power. As I said before it’s not just the power supply, but the output stage as well. Especially the use of BJT (bi-polar) output stages in complimentary NPN/PNP push pull configuration over using complimentary Mosfets as the P channel is Mosfets weak one the N Channel is fine. My krell has a 5kva transformer and 260,000 uf of capacitance and 56 output devices but it even can’t technically double down on power with halved impedance. But it comes close Cheers George |
I have a krell amp that claims that spec but it can’t technically do it What a lot are doing is to underquote the 8ohm wattage to make the 4ohm look like it doubled. You see it all the time now in the Stereophile spec bench tests, where the manufacturer says it’s 150w into 8ohms and 300w into 4ohms the gullible see this as doubling. Then Stereophile show the 8ohm is actually is 200w measured and the 4ohm remains still as 300w, nowhere near doubling then. It’s not illegal, but also not honest either. I’ve been asking Stereophile to "call them out on it" now for ages in the measurements section, but at least they measure and show it for the reader to make up his own conclusions about it. Suppose they have to be careful where there advertising dollars are coming from, and not to rock the boat too much. Cheers George |
Story time!! Absolute Sound: One of the Ten Most Significant Amplifiers of All Time Stereophiles John Atkinson: HQD LOUDSPEAKER SYSTEM and ML2’s I first heard the Mark Levinson HQD loudspeaker system some ten years ago, at the Festival du Son in Paris, in the days when it was a real hi-fi show. Perhaps even more so than by the speakers, however, impressive as they were with their stacked Quads, Decca ribbon tweeters and Hartley 24" woofers, all in beautiful beech woodwork, I was bowled over the amplification used: six Mark Levinson ML-2 monoblock power amplifiers. Capable of just 25W output each, these class-A monsters were the first true high-end amplifiers I had ever heard. The memory of effortless low-frequency reproduction, coupled with a magically liquid midrange, lingered on. The ML2’s drove these double stacked Quad 57’s with Decca Kelly horn loaded ribbon tweeters from 10khz up, and used 2 x 24" Hartley bass units from I think it was 80hz down. http://www.kaponk.com/2019/08/15/hqd-loudspeaker-system/ A friend Otto Major (rip) Quad 57 restorer guru. had this very speaker system, except the amp used was my own built 150w Class-A water cooled self contained mammoth of an amp, 2 preferable 3 man lift. This system, it was something to hear. The Harley’s were mounted in the brick wall behind the Quads and they used the next room!!! as the speaker box. the FS was I think 16hz. Linn LP12 Black Widow arm with the best cartridge I’ve ever heard a Stax CP-X Electrostatic cartridge. https://www.vinylengine.com/turntable_forum/gallery/image/11682/source?sid=eefee7d56ce857f513c305e4e...https://www.vinylengine.com/turntable_forum/gallery/image/11675/mediumThat used a tube HT power supply. Here one dismantled for repair. https://www.vinylengine.com/turntable_forum/gallery/image/15730/mediumhttps://www.vinylengine.com/turntable_forum/gallery/image/11679Cheers George |
I would still think the ML2 would be more than 25 watts into 8ohms They are, when keeping respectable 8ohm distortion figures, losses, as they only have 20v or 25v rails for memory. Cheers George |
I doubt any amp can really double it’s power with halved impedance. If you take literary then no, it would like perpetual motion then "impossible" "Almost" double, it’s wattage is the operative word, 8 to 4ohms, 4 to 2ohms and in the ML2’s case 2 to 1ohm Cheers George |
This statement is false
This ’doubling down’ thing is mostly marketing and **waaaaay** overplayed. This is the false statement, and is the typical statement of amp manufacturers that can’t double down with their amps. However, if the supply line starts collapsing under the extra load, it will never be able to deliver the extra power, no matter what other parameters are tweaked. Not just the supply, but the whole output stage as a well. Use this comparison analogy A 3000w Behringer https://djcity.com.au/product/behringer-nx3000-power-amp-with-smart-sense/?gclid=EAIaIQobChMIsLTX0viJ6wIV3sEWBR0v2w9eEAQYASABEgK3DvD_BwEVerses Old 25w ML2 monoblocks, https://img.usaudiomart.com/uploads/large/2229206-5c605986-mark-levinson-ml2.jpgBoth into a pair of the worst speaker loads known, the Wilson Alexia, but still very efficient at 90db, just a horror load. To a given volume level the 25w ML2 will walk all over the 3000w Behringer for sound quality, control, image and depth. Cheers George |
n80 OP
I see the Parasound Halo 2.1 here on Audiogon for around $1700. Will consider it. It isn’t small or compact but no larger than the NAD . John Curl design, it’ll be better than the Nad. Has ESS dac in it, also has phono stage if you ever need it, sub outputs and an active xover, HT bypass, it’s the Swiss Army knife of integrateds TMR Audio, good reputable retailer. They have make an offer, offer $1500? The legendary Parasound John Curl Halo JC1 monoblocks can drive anything, even Wilson Alexia without breaking a sweat. These JC Halo Hint and Hint 6 integrated, are from the same stable as the JC1 monoblocks. Cheers George |
n80 OP
George, the amp I was referring to is the Proceed HPA2. Should be a great amp for the 7T’s linear amp and dual power supply, 12 x bjt output transistors per channel. Don’t listen to anyone here keep what you’ve got with this Proceed, it’s will be a very good amp with the 7T’s. 250w-8ohm and said to be 500w-4ohms https://i.ytimg.com/vi/LgnrqKWmaoA/maxresdefault.jpg
n80 OP
I’m looking for an integrated with DAC
The 6T’s "could" be just as difficult to drive the only integrated with dac I can recommend is a used John Curl Parasound Halo "Hint" or a new "Hint 6" Both these have ESS Sabre dacs in them, but are normal size not mini or small https://parasound.com/hint.php Cheers George |
@georgehifi I have a Levinson, well, Madrigal, dual monaural amp
I would keep it, just have it serviced up to factory spec. Which model BTW? Cheers George |
n80 OP
Get an amp like I said for your Aerial 7T's and you'll be happy. Your 7T at 84db and 4ohm "nominal" you need 100w-8ohm and close to 200w into 4ohms because you can bet they dive to 3ohm or less with epdr somewhere. From Keith Howards Measurement Labs https://ibb.co/7JrRXX8This is the Wilson Alexia 90db and Wilson spec 4ohm nominal. You would think that just about any amp could drive it. But no. The Wilson Alexia is said to be one of the hardest speakers ever to drive. And that because just in a small band of the low to mid bass it has an EPDR (combination of low impedance and high - phase angle) which to the amplifier seems like .9ohm!! and it sucks the life out of an amp. And a 3000watt Behringer amp won't do it justice, but 25w ML2 will, to a certain volume level
because they can double down to 1ohm,
, it's all about the current, being able to double wattage 8ohm to 4ohm and 4ohm to 2ohm if you can do it for speakers like the Alexia and there are many like it. Cheers George |
By tested do you mean what the manufacturer will publish (some don’t give 4 ohm numbers) or do I need to look for an independent test? Test is to me an independent "test" like Stereophile, Soundstage Measurments, Miller Audio Research etc etc. As amp manufacturers "specs" sometimes/mostly fudge their specs. If they don’t give the 4ohm wattage numbers, then either the amp doesn’t look good doing them(like the heading of the thread) or goes backwards even from the 8ohm, or it simply can’t handle it at all, and turns off or blows a fuse. Look for reviews that give bench test also Cheers George |
n80 OP I’m not saying to get the ML2’s, it was used as an example of what does drive speakers. Your 7B’s drop to 3ohms around 150-200hz not too bad but still needs needs a bit of power there. But! they are specified as 86db by Aerial, but actually tested by Stereophile at only 84db!! I would look for a >100w-8ohm amp that can do tested doubling those watts into 4ohms and you should be fine. Or you can get the $400 3000w Behringer and listen to that, probally not for long.👎 Cheers George |
n80 But I’m seeing a number of respectable mid-fi integrateds with the same wpc for both 8 and 4 ohms. Severely current limited either on purpose for damage protection (maybe by autoformer) and/or by bad design, these amps are not ideal to have with 4ohm nominal or less speakers Because 4ohm nominal speakers can go down even lower than 4ohms, maybe 2ohm, and even lower again as seen by the amp if there is >-50 negative phase angle involved at those low impedance’s. Good place to learn, study Stereophiles speaker bench testing, usually the first 3 or so paragraphs with graphs will give you far better insight than just words do here. Classic example is the 90db efficient Wilson Alexia, which is manufacturer spec’d at 4ohm nominal, yet tests show it goes down to 1.6ohm in the bass and has some -45 degrees phase angle which they say calculates to and presents as 0.9ohm! EPDR (equivalent peak dissipation resistance) as seen by the amp in that bass area. This is heavy reading 3 pages, so skip it if you want. https://www.stereophile.com/content/heavy-load-how-loudspeakers-torture-amplifiers-page-2 If watts is all that matters with no current ability, we all own these 3000w $400 Class-D Behringers, and we wouldn’t need an "Amplifier" forum section in Audiogon https://www.storedj.com.au/behringer-nx3000-ultra-lightweight-3000w-class-d-power-amplifier These 25w yess!! just 25w ML2 Mark Levinson monoblocks would slay the 3000w Behringer into the Wilson Alexia’s to a given level. https://www.hifido.co.jp/photo/05/504/50446/c.jpghttps://img.usaudiomart.com/uploads/large/2229202-mark-levinson-ml2.jpgCheers George |
