Do not even try your tube amps with SL600!

The SL600 is very low sensitivity and if you drive it with more or less powerful SET amp then you will ruin SL600. I have destroyed 6 (six) of SL600. A 5 minutes  of driving SL600 with 8W-10W SET as reasonably high volume and you will never get proper HF from SL600.

What happens is that low power SET will unavoidably clip driving this type of load. Even if some people can’t hear the negative auditable consequence of clipping but the act of clipping itself creates a huge amount of HF harmonics (over auditable range). Some tweeter and crossover can hold it but the SL600 can’t. No, you will not burn you tweeter but you will overheat it once and then the speaker will always gave a very idiosyncratically -bad HF.

What you drive SL600 then stay above 80-100W into 8R. If you drive SL600 with an amp over 2W and sub 50W then NEVER make SL600 to play loud.

manisandher wrote:

As I alluded to before, I'm at risk of becoming a DSET convert - it's all very well having a nice low-powered amp, but what the hell do you use with it? Are there any decent high-sensitivity FR speakers out there? Or is this simply physically impossible?

I do not know. My local guy told me initially that Zu Druids are 110dB sensitive and high impedance. Hearing it I lent to him my full-range Melquiades to try. He has a few other PP and SET amps, so I thought with 110dB sensitivity and high impedance my no-feedback Milq will be running the show. He kind of liked Milq initially but what he reported was not what I expected and it in my view it was confusing.  Another day I visited him; we did some changes in Zu Druids (more need to be done) and tried a few different amps. It was clear the Milq was not the best candidate as it was dynamically straggling to drive Zu Druids. He has some kind of 30-40W tube PP that did much better job. That made me to do only and to learn that Zu Druids are 101dB. In really it might be even less as those hi-fi companies lie for am few dB and it become a common practice. Furthermore in LF the Zu Druids have perhaps 90dB efficiency as then use port and what the port begin to become affective the no-feedback SET would die.

I still, can’t figure out Zu Druids. I would heavily highpass it to use with SET or drive it with 50W SET, preferably with feedback. Something the level of Lamm ML1 might be a good candidate for them to try. If you look out there then you will see anybody promote Zu Druids as some kind of wonder that might be perfectly used with flea-power amp. This is why people attracted to them I guess. However, I do feel that it is a bit stupidity to promote Zu Druids as a SET friendly loudspeaker. It might be a good speaker for the money but not for use with SET. In 2006-07 the industry whores created a lot of hype about Zu Druids. I do not know if it was worthy or not but I know that fact that they were pushed as “$3000 solution that can be driven by SET full-range“ was very inaccurate.

Romy the Cat wrote:

I still, can’t figure out Zu Druids. I would heavily highpass it to use with SET...

manisandher wrote:

Do you think 150Hz is too low with a 7W SET? In all honesty, I think I was heavily influenced by the Zu Druid 'hype' myself. I had bought the Berning (without really thinking too much, really - it seemed like a good idea at the time!) and was then stumped as to what to use with it. I didn't have space for horns (although I do now), and the Druids seemed, from what I had read, to fit the bill. But now that I've got the Berning and the Druids, I feel obliged to at least try making them work together...

I do know, Mani, it is hard to say. My crossover strategy is not to cross where is it necessary from logical point of view but where it necessary from sonic point of view. In practical terms it means that you need to look at the quality of you complimentary upperbass section and to listen what acoustic system and amplification cases the octaves of your interest better. Also, you have that freaky Berning  Siegfried. I mean “freaky” because it is not a regular amp that is more or less predictable to a degree but Mr. Berning‘s own OTL switching creation. It is god or bad – it is know only for the people who use it – and it is much unknown to me how it behaves driving the Zu Druid’s port. I have local guy with Berning  amp but he has a conventional  non- freaky Berning. In your case it is hard to predict anything.

OK, I see.

Actually, I was planning on using the Druids with their ports sealed. Bad idea?

FWIW, I have a pair of Wilson Benesch Chimera speakers (the UK-based manufacturer, not to be confused with the 'famous' US one) that I'm hoping to use for upper and lower bass duties, i.e. disgarding the HF driver (and the built-in passive x-overs). I've just got a feeling that the ABR-loaded upper chamber might work very well from 70-150Hz or so. I intend to block the downward firing ports of the lower chamber, and push these drivers 'hard' <70Hz.

The Chimeras have average sensitivity, so I'll use the amplifiers that I currently have knocking around - a Pass Aleph 4 for upperbass and a couple of Hypex class D amps for the lowerbass.

Hopefully, I'll manage to get something half-coherent coming out of this hodgepodge. If not, DSETs and horns will be on the agenda sooner rather than later.

Mani.

Romy the Cat wrote:

Romy the Cat wrote: ...To substitute SL600 original tweeter with anything else, would it be Revelators, Diamond or made from Faberge Eggs is like to make a movie with Humphrey Bogart and ask busboy form a nearby Chinese restaurant to re-record the Bogart’s dialogs. The SL600 tweeter with pure copper dome and phenolic suspension was probably the most perfect tweeter even was made (sonically), with only disadvantage in sensitively department.

Romy can you tell us what you thought of the Zu loudspeakers, I spent an afternoon in their company recently, they were being used with a 25 watt PP Luxman, I believe.

Keith.

You have an opinion on most things ( whether you have heard them on not ) I thought you would jump at the chance to pronounce on the Druids, seemingly not.

Hi Paul,

Could you help me understand what you mean?

Are you saying that even without a high-pass filter, a <8" driver has an imbalance of 'harmonic development' above and below 150Hz... and that this is not the case above and below 400Hz?

If we go for a <8" driver high-passed at 150Hz, could we not compensate for this phenomenon by having a >8" driver low-passed at 150Hz?

In any event, the Druid has a 10" 'full-range' driver that I'm hoping will be quite 'happy' down to 150Hz. Strangely, my upperbass driver will be a 7" driver (the one in the WB-Chimera's upper chamber)! Perhaps not the best solution for 70-150Hz duties... but I'm just working with what I have. Although no doubt challenged, the 'harmonic development' will presumably at least be even between 70-150Hz.

Mani.

Romy the Cat wrote:

manisandher wrote: As I alluded to before, I'm at risk of becoming a DSET convert - it's all very well having a nice low-powered amp, but what the hell do you use with it? Are there any decent high-sensitivity FR speakers out there? Or is this simply physically impossible? I do not know. My local guy told me initially that Zu Druids are 110dB sensitive and high impedance. Hearing it I lent to him my full-range Melquiades to try. He has a few other PP and SET amps, so I thought with 110dB sensitivity and high impedance my no-feedback Milq will be running the show. He kind of liked Milq initially but what he reported was not what I expected and it in my view it was confusing.  Another day I visited him; we did some changes in Zu Druids (more need to be done) and tried a few different amps. It was clear the Milq was not the best candidate as it was dynamically straggling to drive Zu Druids. He has some kind of 30-40W tube PP that did much better job. That made me to do only and to learn that Zu Druids are 101dB. In really it might be even less as those hi-fi companies lie for am few dB and it become a common practice. Furthermore in LF the Zu Druids have perhaps 90dB efficiency as then use port and what the port begin to become affective the no-feedback SET would die. I still, can’t figure out Zu Druids. I would heavily highpass it to use with SET or drive it with 50W SET, preferably with feedback. Something the level of Lamm ML1 might be a good candidate for them to try. If you look out there then you will see anybody promote Zu Druids as some kind of wonder that might be perfectly used with flea-power amp. This is why people attracted to them I guess. However, I do feel that it is a bit stupidity to promote Zu Druids as a SET friendly loudspeaker. It might be a good speaker for the money but not for use with SET. In 2006-07 the industry whores created a lot of hype about Zu Druids. I do not know if it was worthy or not but I know that fact that they were pushed as “$3000 solution that can be driven by SET full-range“ was very inaccurate. The Cat

KLegind wrote:

Initially I thought the Zu might be an interesting speaker in the context of tube amplification, however I tried the fullrange driver approach and I have misgivings about it... Anyhow, the industry rag Hifi World (with whom I have a hate/love relationship) did a review of the Zu a few years ago. The content of said review I think is irrelevant, however there were measurements of the speaker done by Noel Keywood and they showed a much lower sensitivity than advertised. I believe it to be in the low nineties. The frequency response also looked suspect. I see if I can find the review when I get home from work. best PS. I do not express any opinion on Zu sound as I am unfamiliar with it. In a certain context it might be good.