SET 45 and their (real) required speaker efficiency

@vvcv You have asked a number of good yet different questions.

On your primary question of pairing a 45 SET with your 94.5 dB sensitive Omegas, you will likely receive feedback from most that will say the 1.5 to 2 watts from a 45 SET will not cut it, especially so since 90% of your listening is Classical.

However, you haven't described the type(s) of Classical you listen to? For example, if it is small scale and leans towards solo or small group / venue performance and with instruments that have ~narrower~ 'frequency range,' then you may receive different feedback.

I suggest reaching out to members like @charles1dad @almarg @atmasphere and others on your questions.

Thanks David, I literally just finished re-reading segments of an 'article'(?) I had intended to include in my question that relates to your statement. You are most indeed correct, Classical/Contemp. Classical can run the full gamut of dynamics. But, I rarely listen to full scale symphonic pieces on speakers, and if I do it is on headphones. I've just found it easier that way overall -for orchestrations. So, yes, small ensemble to solo performances/recordings is my lifeline. But, even then, dynamics can come into the picture pretty quick. Surprise 'attacks' during a Feldman piece or two anyone? :D

But, I'll go ahead and post a quote that I keep running over in my head. And I just can't figure out if this guy is pushing his 100db drivers or giving honest good information. Here it is:

"No wonder even classical musicians are complaining about damage to their hearing. And by the way, there's not a whole lot of deep bass, even from a full orchestra with 4-6 bass players.
Now, recreating a live musical event from 2 watts take serious measures and I won't recommend anything less than 97-98 dB sensitivity, preferably 100 dB/2.8V. Some day I'll try to make a ~100 dB system from my Supravox drivers" http://www.troelsgravesen.dk/HES.htmhttp://

So, my main question with this quote is whether he is referring to a full-blown symphony when he states 'recreating a live musical event from 2 watts'? Surely, I have heard classical guitar recordings (which I once played prior to destroying my wrists), as well as violin, for example, that may not be whizzing past the 2 watt limitations. 

I've been looking at Fostex drivers, which seems to be one 'go to' for efficiency, and not finding many beyond my current speakers db. Is it the complicated looking cabinets that add to the efficiency? Not at all unfamiliar with the likes of some Lowthers cabs.  

I'm quickly getting the idea that a horn speaker of some sort is the way. I only wonder if there are any small enough for a smaller room. That's another thing I forgot to mention in my post. My listening range is near-mid field. About 3-4' from the speakers. Would this help at all with a 95-98db range? 

Sorry for another long ramble post guys. Just a lot I've been thinking about, and unfortunately, have forgotten many of my writing class strategies regarding the quick and coherency approach. :D

thanks,
rob

I have a SET 45 (1.75 wpc). Built by Will Vincent on a Dynaco ST70 chassis. It has only 5 tubes total: a 5V4 rectifier, two 6C6 pentodes as input tubes and two 45’s ouputs. Encron output transformers. Will did a beautiful job of powder coating the Dynaco chassis in white gloss and adding high-quality input jacks, speaker connectors and an IEC power inlet.

I bought a pair of vintage Heresy's (100 db/1 meter) to use with it. You will need something similar to make use of all the 1.75 watts of a single 45! 

Hi vvcv, I have a pair of 300B and 45 amps. (Wavelength, both bought here) with Magnequest transformers. I had no prior experience with such amplification, but felt with speakers, the higher the better. When a pair of Beauhorn Virtuoso' (Lowther DX4,single driver, @106) came up here here also at a very nice price, I grabbed them! Btw, of this was unauditioned but well researched by users experiences and reviews etc. You hear of those having lower efficiency speakers whom say the match is good, of which I haven't personally heard it, but more always can't hurt, and DOES make a difference, I'm sure. Actually, when I move to larger quarters (a room) I have a pair of JBL 4676 (4550 bottom cab) also @106, which I plan to try bi-amping with both pairs of amps. That will be another story for another time. Good luck.

Hello Isochronism,

Thanks for that. I had not idea a single driver could get there. Curious, after having made a great gold find, have you done any post research to see if there are any other Lowther, or perhaps Fostex, drivers/cab pairing that give the same performance as far as db? I would enjoy having those I'm sure, just too much for my limited space. 

On a separate topic, how would you rate the Lowthers, as far as tonality, paired w/your amps? Say, starting at neutral on acoustic instruments? 

Hey roberjerman,

Yep, I've considered those just for the size aspect. I don't want crossovers, but hey, at 100db, with the bonus of that size for my room. All win win. 

Yep, I've considered those just for the size aspect. I don't want crossovers, but hey, at 100db, with the bonus of that size for my room. All win win.

I did run across a thread where the original Heresy is around 96db. Do you have the original, II, or III?

thanks

vvcv, I have no other listening experience with Lowthers nor with the others you mentioned. I did read a review, I'm sure easy to find, where the reviewer felt the Virtuoso was the best cabinet design tonally (etc) for that driver, and had experience with many. Some complain that they (all single driver, I supposr) don't go low or high enough. I have always been very satisfied. No crossover (of course) so very immediate and dynamic (?)  Small scale music Jazz, Chamber, they excel at.(imo) But not only, of course. Female voices sound like they are there! 

... well Men's voices as well, I suppose. Although, I don't invite them over much 😄

Thanks for that extra bit isochronism, gives a bit more to check out. It's starting to look like I'm going to find the speaker before I order the 45. I do have a 2a3 shipping any day now, so that will help with the speaker choice. As it's not quite as much drive as my 300B. 

Exactly, people do seem to have a love/hate thing going on with their no cross-over 1 driver pair of speakers. I hear these drivers as a great extension of the amps' electronics. My cable of choice is directly from what a majority of studios use. Mogami cable. And I'm working on finishing all my cables with KLE connectors. Then I'll change to KLE for my speaker terminals. So, as much as I can use the same wire/connectors to get the amps signal to the driver, the more I at least feel like I'm trying. So far, it's paid off very well. I am not exaggerating when I finally had 90% of my cables/connectors from all the same make and the difference was immediate. t's funny, many big name 'audiophile' companies will claim to get the speaker first, "speakers are everything". I guess it's true to some point. But if you talk with Louis over at Omega, he states that it's the amps sound which is everything. His speaker is only there as an analog electronic extension, of sorts, of the amp. As there is not much between. A very well respected SET designer has mimicked almost the exact same words. Makes me wonder. But yeah, I save a lot of money with this cable/connector thing due to making my own. I'm anal about it all. Thermal wire cutters, Cardas solder and taking care of my best solder tips. Saves me so so much cash. The next move will be to repeat it but all with KLE copper connectors. 

Thanks again. I'll look up the Virtuoso for size and performance. Maybe I can use the size of this cab. 

I have an Oliver Sayes 45 SET (1.5 watts) and Omega Super Alnico monitors in an 11 x 18 room and listen to mostly small ensemble classical but also some full orchestral pieces. I have more than enough power to play at comfortable listening levels.

For what it's worth, my speaker cables (Tempo Electric, solid single-core silver) have bare-ends. 

I really like my 45 SET and Omega Super 3 High Output XRS. Very musical combo. 

Hello ricwa,

such great news thanks man. I think i'll call Louis for sure on Monday to try and get his honest opinion on the amp I'm looking at, and what he thinks. I just realized the new Super Alnico tower is 97db. Looks like two exact drivers w/one w/o the tweeter. May be interesting to try a get a demo pair to listen to. 

Thanks jmolsberg. Another declaration of confidence in my amp of choice and current speakers. 

Finally, what would your experience with the 45 SET amp suggest as far as the optimal efficiency rating for these tiny two watts?

As with all things audio, it depends. It depends on your ears, your expectations, your gear (listed), the size, shape and construction of your room, how loudly (or softly) you typically play music and, mostly, your ears.

I ran a pair of Omega Super Alnico 6 monitors as my main speakers for a couple of years, paired most often w/ both a 2W 45 SET mono blocks or a 5W SE EL34 amp. I loved them and thought they were great for most non-headbanging music but weren't quite cutting it with large orchestral and opera pieces. Maybe it was the single driver or maybe it was the whizzer cone. I ended up replacing them with something completely different that isn't low-powered tube friendly. That's not to say I don't miss the Omegas - I do.

But to answer your question, 2W is enough when it's enough. And it's not when it's not. If you like the sound of the Omegas but you can't play loud enough, get an amp that puts out more horsepower. I had a McIntosh MC225 (25 W PP) and it really changed how the Omegas sounded. Not better or worse, just very different. If you don't like the sound of the Omegas then changing amps probably won't make you happy. My motto is speakers first: find a speaker you love and will work with your music and your room and then find the right amp to optimize the speaker. Others here may have a different opinion.

I just got a pair of 45 mono blocks and am pleasantly surprised with how they compare to my 300b amps. To my ears, my 45 set amps can play subjectively louder than my 300b's with less distortion. I often don't realize how loud the volume is when I am listening. Maybe the first watt is better?

All that aside, impedance is just as important as high sensitivity in matching set amps with speakers. The 8 ohm rating of your Omega speakers would be good for a 45 set amp if it is a flat 8 ohms with no major dips. A sensitivity of 94.5 db, while not ideal, would work okay too if that is truly the sensitivity of the speakers. Actual sensitivity measurements are usually lower than what the manufacturer provides (see, for example, the recent Stereophile review of the Volti Razz speakers). The bottom line is that I would try to get some real world speaker measurements before proceeding, as your speakers are perhaps on the cusp of what would and would not work with a flea watt amp.

In my limited experience my enjoyment of flea powered amps increased whenever I paired them with speakers of higher sensitivity.  I have a low powered 2A3 (3W) and kt88 (8W).  The sound was good when paired with Zu Omens and got much better with Rethm Maargas.  Greater dynamics and presence, and they could go much louder and with great ease.  As good as the Rethms sound, I’m getting the best sound yet from my Altec 604e.   Now these Altecs have the Werner Jagusch crossovers while the Zu and Rethm are stock and are both rated at approximately 96dB, while the Altecs are probably around 100dB.  
I would pair very low powered amps with very sensitive speakers.     Good luck.  

Like much with hifi, it’s largely a matter of expectations.

Low power SET amps are a very special case though.

To get the most out of just a couple watts of power, you need not just the most efficient speakers to pick up the slack, likely horn loaded, but speakers that are also easy to drive as indicated by phase and impedance charts. Otherwise that will impact the sound quality at all volumes and the speakers may go loud enough but with significantly more distortion as volume increases.

Additionally to get fully extended bass out of just a couple watts, if that matters to you, you need larger speakers.

If you do not have need to go loud and room is smaller, and you are willing to pass on the lowest octaves, that opens up many more possibilities for lower cost.

There is no getting around physics.   The good news however is most music happens in the midrange.......

@vvcv Just a quick comment regarding switching binding post terminals. If you're getting in there and modifying the speakers and amplifiers, you might consider just replacing with wago lever clips instead (I use 221s).

Why spend all the work energizing a big metal piece with a sloppy mechanical connection when you can just switch to a high tension, small piece of pure copper that can take a 4kV surge?  Less likely to come loose than most binding posts and about as close to direct soldering as you can get. They don't look as fancy, but highly preferred in lieu of terminals for me...

https://www.wago.com/us/lp-221

I have had many SET amps with both Avantgarde Trios and Lamhorn speakers. I still own a 45 amp that I sometimes use with my Lamhorns, I have to say there is a big difference in saying enough power to play a system loud and enough power to play a system effortlessly. Also, SET amps change drastically in sound when they are pushed even a little. This is what many people like about them though. 

With my Trios using both a yamamoto 45 amp and wavelength cardinal 300b it was not even close to the powerful 30 watts from my 845 Viva amps. I wouldn't say they were under powered, they did play loud. These speakers are 107 db efficient. Both the lower powered amps seemed to sound  slow in comparison. 

Even with my Lamhorns that I still own: which are single driver crossoverless speakers and 15 ohm,  my push pull amp performs at a higher level with regards to dynamics and prat than with my 45 amp and Art Audio PX-25. Same thing, not even close. 

A speaker that is 100 db efficient, a 45 I would say is being pushed to its limit. I have to say though that these low power tube amps do have a quality that is attractive that's why I still own two. But nothing is a substitute for power.

A good analogy is, is a  50 horse power engine enough to move a car around town. Yes. But not in a high performing way. I remember people giving their opinions about his to me before just as I am now. I recommend to go ahead and try. All part of the hobby and learning experience. 

I've got a pair of backloaded horns using Fostex 208 E Sigma drivers available for local pickup in SoCal, if anyone is interested.  I just want to see them go to a good home  Estimate about 98dB efficiency and worked well with my Moth S45 (45 or 2A3).

I know how you feel about wanting to see gear go to a good home. I’ve had a couple of limited production amps that I purchased for the investment. Wow, and did I ever get a great trade with one of them. I’m still shaking my head. But, I did start to enjoy the amp a lot. But, they promised to keep it in the family for a very long time.

Anyway, great people of Audiogon. I just want to thank all of you for all the great information (my favorite audio source of information). I’m now traversing page after page and getting speaker choices narrowed. But, thanks to you guys, I feel much more comfortable making the right decision in pairing speakers with this certain amp.

Take care!

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!

See what John Kalinowski can make for you. Below is a fair idea of what you'll need:

http://www.bd-design.nl/contents/en-us/d132_John_Kalinowski.html

Or maybe one of these:

http://classicaudioloudspeakers.com/cgi-bin/index.pl?fs=2&upper=25&content=26

Or assemble your own but choose the right drivers:

https://greatplainsaudio.com/enclosures/

Most 45 SET amps are about 1.5 watts output and 2 watts is really stretching it. Distortion of the amps gets very high near their max power. So really, with a 45 amp, you want to not exceed 1w and preferable at 0.5 watt or less.
94.5dB even with 8 ohm and impedance friendly speakers are not efficient enough for your 45 SET amp to do serious listening. Can it be satisfying? Of course. Likely in a small room and with small ensemble classical music, you're listening at between 85-88db. The question for amp/speaker matching is really about headroom.
Here is how you can look at it. for every 3dB of speaker output, you will need to double the amp power e.g. if your speaker is 94dB/1watt/1meter efficiency.  Then for 97db, you need 2watt. for 100db, you will need 4watt. For 103db, you will need 8 watt.
Since you amp is only 2 watt, them your Omega speakers can only hit 97.5dB max and that's almost at clipping level. so your effective listening range is between 85-97dB i.e. 12dB of headroom.
But imagine if you have a 100dB speaker. Then your 2watt amp can generate 103db i.e. a listening range from 85db to 103 db which is 18db headroom. This is 6dB more than your existing Omega speaker i.e. 4 times more power.
So really, what it boils down to is that 45 SET amps should ideally be matched with speakers with a minimum of 100dB (in the correct impedance as your amp out impedance). Just my 2 cents.

I have three SE amps: a 45, a 2A3 and a 6BG6. 1.75, 3.5 and 6 watts respectively. And a pair of Heresy's. The 6BG6 has enough (barely) to work. The other two are only good for headphones. 

Hey,

In looking around, I keep checking out Decewares' site to compare how their rated efficient speakers stand next to others. I've been looking at a lot of Lowther cabs. I guess at this point I should move this over to the speaker section, but since you guys are here I'd like to throw out a quick question regarding one speaker on Decs site. I ran across a small read regarding how new technologies are allowing for better sounding larger drivers. I then remembered a 15" 100db driver over at Deceware. It's the Model: ZF15L (open baffle)
Have any of you run across anyone that has perhaps heard this speaker? And as a general question, can speakers at Decs site be considered good enough to stand on their own sold at Deceware or elseware? I can almost answer this question as they have an Omega speaker. I think I've scratched anything under 98db off my list, even though I'm listening @4' to tweeter and under 90db 90% of the time with solo to small ensemble classical. Don't shoot me, but I'll leave a YouTube link to the speaker. What got me curious was the piano and cello sound. Both of these instruments of course sound very large, and they seemed to sound just about good enough in this demo. Speaker tone, and all the rest aside. 
https://www.youtube.com/watch?v=byhqlewpQQY

thanks

VVCV, There are several factors that determine the speaker sensitivity needed to use 45 tube amps. Many have already been stated. Room size, music density, max SPLs for dynamic peaks, average listening volume, etc.Keep in mind that many manufacturer's speaker sensitivity ratings are for one central frequency. As ddriveman suggested the lack of headroom for dynamic peaks is often the limiting factor. Speakers without crossovers can help. Passive crossover can sometimes be a more difficult load and can consume power. A flat impedance curve and minimal phase anomalies help.

I use mostly low power SET amps to demo our speakers which have a sensitivity of 105 dB. We have two pair of 45 mono amps, a pair of 2A3 mono amps, a pair of 300B mono amps and a few other amps of various types. Our showroom is 21 feet by 31 feet with a ceiling that starts at 9 feet high and goes to about 14 high feet at the rear. Our speakers have separate powered woofers so the SET amps don't have low bass duty. The main towers go down to about 100 Hz but we typically set the active crossovers to 120 Hz. The amps are directly coupled (no passive crossovers) to the drivers. The 45 tube amps, to me, sound the best and have no trouble driving the towers to high volumes with no compression. In our setup the 2A3 amps are a close second. Our speakers are a line source so the dB loss per distance is less than a point source speaker which helps. 

Our speakers are unique in many ways so maybe not the best example but typically for a medium size room, listening to reasonable/enjoyable volumes a minimum sensitivity of 100 dB should work. With so many variables you should audition the potential combos.

@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.

From a great deal of experience listening and comparing different amp types on 2 way 12 ohm 96 db speakers I couldnt even live with the output of a parallel single ended 300B amp. Ralph (Atmasphere) is 100% correct in that these amps fool you into thinking that the output is adequate when it is actually colored as hell. What you are hearing is not dynamic nor do I think it is correct. This at least has been my experience over several hours of comparisons per day over several days with numerous amp designs. On high impedance speakers the clear winning design has always been an OTL. 

Had a pair of LaScalas powered by Don Allen's 300B/ 2A3 SE switchable amp. Also a Don Allen SE EL84 amp.They could rattle the windows in the LR. And play nice and sweet and quiet as you would like.

Put a higher wattage OTL on your LaScalas and see if you feel the same way. Of course the presentation will be much more linear and much less colored which I appreciate and others dont.

Is the 45 SET you are considering also from Triode Lab, and if so have you reached out to Frank Ng at Triode for speaker recommendations?  He is very helpful in that regard, he's heard his amps with lots of speakers and knows what his customers are using.

I have a EL84SET-FFX from Triode Labs, about 5-6 watts.  My experience has been higher sensitivity means louder but not always better.  I prefer my Triode Lab amp with my Coherent Model 10's which are about 94 db, over Zu Druids which are 101db (there are other amps where I prefer the Zus).  Every amp/speaker/ear combo is different.  Your Omegas may be fine.

My listening range is near-mid field. About 3-4' from the speakers.

I wouldn’t call this nearfield to midfield; I’d call this extreme nearfield—more like a desktop system. And I’m not sure that any of the advice you’ve received so far has taken this into account.