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SET 45 and their (real) required speaker efficiency

Hello,

Gosh, wasn't sure if to post in the speaker or amp sections. But here it is. 

I've got a Finale/Triode Lab F-300B Monoblock amp paired with the Omega Super Alnico monitors stated at 94.5db efficiency. It does very well with this amp and I'm very happy with the pair overall. With classical being 90% of what I listen to, I guess I haven't really pushed the system to its limits, but it delivers plenty of what I like with acoustic instruments. Harmonics (texture and timbre), tone, minor dynamic shifts (musicianship), etc.

My question is for SET 45 tube owners and recommended speaker efficiency. Do the 2 watts from these amps have a 'real world' threshold where they simply can't deliver under a certain efficiency rating? So, for example, my speakers state 2 watts and up are enough. But I've had a few people tell me that 94.5db is not enough for this SET. However, on the Decware site, it does put a pair of Omega speakers on it's site as, what I imagine being a suitable speaker to pair with their 2 watt amps. The amp I'm thinking of getting will have Hashimoto transformers and a 20 watt output transformer. Not sure if that will give a bit more for the speaker to use or not. Also, are speakers w/o crossovers something to consider if I need to go look for another pair of speakers? Finally, what would your experience with the 45 SET amp suggest as far as the optimal efficiency rating for these tiny two watts?

Geesh, it's 5:40 am, no sleep yet, please ask a question if all the above sounds like someone hasn't had sleep yet.

Anyway thanks folks, really appreciate any suggestions to an optimal efficiency.

take care,
rob


vvcv

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,640 posts
 
@vvcv  A nice plan B to consider:

If you are set on the type 45 power tube, why not get an amp that uses a pair in push-pull? I've done direct comparisons; the thing about any SET is that you really don't want to run them past about 20% of their total output power, since higher ordered harmonics start showing up on the transients (where the power is). This causes the amp to sound 'dynamic' as the ear uses the higher ordered harmonics to sense sound pressure- its distortion masquerading as 'dynamics'.

But with the same tube operating in push-pull, but otherwise class A and zero feedback, the total power will be more like 6-7 watts and about 90% of that power will be usable as opposed to 20%. So you will have a much wider range of speakers you can play.

Now to the comparison; side by side it was obvious that the push-pull amp using 45s was more detailed (vocals were easier to make out) and had more bandwidth both in the bass and the highs and every bit as smooth. IOW, no downside except you need a pair of power tubes per channel.
atmasphere's avatar
atmasphere
11,640 posts
 
A type 45 based amp is really only going to make about 0.75 watts or so unless you are using some kind of super-45 of which a few exist.

My 45-based amp uses original RCA output tubes. My speakers are 98 dB and 16 ohms; very easy to drive but simply not enough power and my listening room isn't that big. So this is a very room and speaker dependent issue!
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