Macca's Lash Up 2: Lash Harder

[Barry]

For what area of panel? Which Quad etc? A comparable area to the panel I posted HAS to be more than 0.1g.

According to Wikipedia it is 3mg, but it is not clear to which panel (treble, mid or bass) that figure refers. https://en.wikipedia.org/wiki/Quad_E...ic_Loudspeaker

My quoted figure of 100mg was from a reference that I now cannot find. The only other references state the mass of the diaphragm is very similar to the mass of the air to which it couples - but that is somewhat ambigious.

Whatever the true figure is, it will most certainly be less than 1g.

[walpurgis]

The ESL 57 diaphragm is Melinex I believe. It has very low mass so will not need electrical damping at audio frequencies. However, it can resonate like a drum skin when stretched taut, as in the Quad electrostatics. I've always noticed this slight 'drumskin effect' (colouration) when listening to them. Doesn't detract from their enjoyablilty though.

[DSJR]

So are you disputing the figures that Duncan posted earlier then, Dave? Also, to your knowledge, has the Krell ever been serviced/re-capped?

Marco.

The ONLY person to delve inside was ME! I removed a film of dust here and there, took some pics which may have been posted here once until Photobucket removed them and the top was put back on. Apart from some slight heat discolouration on the boards around the input transistors (daily-chained in a current-output formation I understand - this topology apparently being a D'Agostino 'thing'), the caps were fine with no bulging I could see and were original. Unlike the earlier models, this amp only gets really hot when worked hard and when idling, it's as cool as any other more normal amp. Macca told me the bias lights hardly ever came on in his usage, where here even with the Spendors, I had the intermediate ones coming on and half an hour in the cupboard at this level the case was rather hot (I only had two sessions of forty minutes using it this way), so I scuttled back to my geriatric Crowns with no loss in sonics *on my particular stereo!* I'm not in the slightest saying anyone else would agree with me here and I'm no longer at all able to even begin to claim 'golden ears.'


I can only state how the amp worked for me under my 'real world' conditions and loosely quoting your own 'vibes,' people can quote as many figures as they like, but how does the bloody thing WORK in practise? I used my old and less old sources first with a (*** P50) passive preamp (10k Log pot) and then with a 'single ended' active one offering up to 10V clean into a typical amp load (5V into a 600 ohms load), my usual geriatric amps requiring around a Volt at 20 - 25k input impedance.

[Marco]

The ONLY person to delve inside was ME! I removed a film of dust here and there, took some pics which may have been posted here once until Photobucket removed them and the top was put back on. Apart from some slight heat discolouration on the boards around the input transistors (daily-chained in a current-output formation I understand - this topology apparently being a D'Agostino 'thing'), the caps were fine with no bulging I could see and were original. Unlike the earlier models, this amp only gets really hot when worked hard and when idling, it's as cool as any other more normal amp. Macca told me the bias lights hardly ever came on in his usage, where here even with the Spendors, I had the intermediate ones coming on and half an hour in the cupboard at this level the case was rather hot (I only had two sessions of forty minutes using it this way), so I scuttled back to my geriatric Crowns with no loss in sonics *on my particular stereo!* I'm not in the slightest saying anyone else would agree with me here and I'm no longer at all able to even begin to claim 'golden ears.'

No problem, but it would be prudent to check the caps, and most likely replace them, on any 20-year old SS amp, not just the Krell. Therefore, aside from anything else, I suspect that there will be some mileage in that for Martin, if he decides to go there.

I can only state how the amp worked for me under my 'real world' conditions and loosely quoting your own 'vibes,' people can quote as many figures as they like, but how does the bloody thing WORK in practise?

Indeed, but that's precisely what Martin is doing: commenting on how the amp is working in practice, in the context of his system, and observing that he hears a lack of 'excitement' in the sound, which the Krell *could* be responsible for, or more likely IMO, it's sub-optimal combination with his passive preamp, due to the low input sensitivity of the Krell.

Nevertheless, all will be revealed when, those of us present at Martin's forthcoming mini-bake off, use our EARS (not any figures) to assess what the issue is, and whether an active preamp solves it - or if it's simply a compatibility issue between the Krell's high damping factor and Martin's speakers, which a change of power amp should resolve

Marco.

[Barry]

The ESL 57 diaphragm is Melinex I believe. It has very low mass so will not need electrical damping at audio frequencies. However, it can resonate like a drum skin when stretched taut, as in the Quad electrostatics. I've always noticed this slight 'drumskin effect' (colouration) when listening to them. Doesn't detract from their enjoyablilty though.

The electrostatic forces acting on the inner electrode (the conductive Mylar film) are such that the diaphragm is made exceptionally rigid: the forces won't allow for break up, and the diaphragm moves as a planar whole. What you might be hearing (and what some call a 'credit card' colouration) is that due to the less than rigid outer frame of the speaker. This is most noticable at around 10kHz. Also some colouration is caused by the clamping of the diaphragm at the edges, where obviously it cannot move as a whole.

[User211]

According to Wikipedia it is 3mg, but it is not clear to which panel (treble, mid or bass) that figure refers. https://en.wikipedia.org/wiki/Quad_E...ic_Loudspeaker

My quoted figure of 100mg was from a reference that I now cannot find. The only other references state the mass of the diaphragm is very similar to the mass of the air to which it couples - but that is somewhat ambigious.

Whatever the true figure is, it will most certainly be less than 1g.

Hm no I think for an equivalent area to the panel I posted it would weigh over 1g. For an ESL bass panel of equivalent area I believe you'll find a thicker diaphragm is what you would need. I don't think we could find an ESL with as large a bass diaphragm as the mid of the Apogee range Duetta, though.

I do think it will be less than 46g by a factor of 10 or more, though, at a guess. Most of the mass in mine is aluminium.

I am not totally sure. So don't quote that anywhere as some sort of truth anyone please Not that you would anyway LOL.

[DSJR]

No problem, but it would be prudent to check the caps, and most likely replace them, on any 20-year old SS amp, not just the Krell. Therefore, aside from anything else, I suspect that there will be some mileage in that for Martin, if he decides to go there.




Marco.

Good luck to him at nineteen or so electrolytics a side from memory

By the mid 90's, caps had improved I think and I also believe Krell had *possibly* learned their lessons from earlier models which baked their amps hard continuously. If the voltage of the caps is a goodly margin over the voltages they need to deal with and they're not thermally stressed, it's my current belief that they shouldn't go off unduly in domestic use, and this particular amp had had an easy life as a secondary item, according to the chap who passed it to me. Always happy to be proved wrong though and that amp isn't the easiest to strip down and as it was working, no way would I needlessly ruin any value in it by attacking it with gusto. No hums or nasty noises (their transformers are SILENT too despite the size) and as far as I could ascertain, both channels 'sounded' the same and the bias lamps worked together, so I assume the amp was behaving itself.

I also believe it depends on the make of caps used. The very old US amps I use a lot originally had sealed caps which appear to have a very long life. the chunky looking alternatives they went over to in the mid 70's don't seem as long lived, despite showing no external issues - I'm about to experiment with one of my preamps from this firm, as the particular phono stage has a slight background high pitched 'hum' not noticed in the other one, which is reminiscent to me of a failing supply cap and this preamp sample has had a hard life in storage as well as much use when it was newer.

[DSJR]

I don't think we could find an ESL with as large a bass diaphragm as the mid of the Apogee range Duetta, though.

My D'Agostino/ML owning friend had Duetta Sigs for many years, driven by a Krell KSA80 and I think a KRC-2 mostly, although the power amp was changed to a KSA250 I think later on. When he flogged them, the bass panels were wobbling almost uncontrollably on any kick drum thwack. They sounded great in his room when they were newer though and vocalists had proper 'height' which conventional boxes aren't so good at.

[User211]

My D'Agostino/ML owning friend had Duetta Sigs for many years, driven by a Krell KSA80 and I think a KRC-2 mostly, although the power amp was changed to a KSA250 I think later on. When he flogged them, the bass panels were wobbling almost uncontrollably on any kick drum thwack. They sounded great in his room when they were newer though and vocalists had proper 'height' which conventional boxes aren't so good at.

As a general rule by the ribbon manufacturer anymore than 8 years is a warning sign for a pair of Apogees. Some will last a lot longer if they are played infrequently and at low volume. Some will sound fine for far longer unless you pair them with an optimally broken in set, in which case you'll know they are far from optimal..The same is true of ML panels, though they can fail far sooner, and after owning ML panels for 17 years I know which I think is the more robust solution, and it isn't ML

The trouble with the ML solution is the stat coating is directly exposed to the air. It is a plus over Quads in terms of performance but it isn't in terms of longevity.

[Marco]

Good luck to him at nineteen or so electrolytics a side from memory

By the mid 90's, caps had improved I think and I also believe Krell had *possibly* learned their lessons from earlier models which baked their amps hard continuously. If the voltage of the caps is a goodly margin over the voltages they need to deal with and they're not thermally stressed, it's my current belief that they shouldn't go off unduly in domestic use, and this particular amp had had an easy life as a secondary item, according to the chap who passed it to me. Always happy to be proved wrong though and that amp isn't the easiest to strip down and as it was working, no way would I needlessly ruin any value in it by attacking it with gusto. No hums or nasty noises (their transformers are SILENT too despite the size) and as far as I could ascertain, both channels 'sounded' the same and the bias lamps worked together, so I assume the amp was behaving itself.

I also believe it depends on the make of caps used. The very old US amps I use a lot originally had sealed caps which appear to have a very long life. the chunky looking alternatives they went over to in the mid 70's don't seem as long lived, despite showing no external issues - I'm about to experiment with one of my preamps from this firm, as the particular phono stage has a slight background high pitched 'hum' not noticed in the other one, which is reminiscent to me of a failing supply cap and this preamp sample has had a hard life in storage as well as much use when it was newer.

Well, as us subjectivists always say: 'The proof of the pudding is in the listening'! So if Martin does decide to get the amp recapped at some point, we'll find out if your theories are correct, or not

Marco.