Tube amps and speaker ohms

40 watts into 89db is pushing your luck. Anything loud or dynamic may over-tax your amp and distort. Also, if you are new to tubes, 845's are not necessarily the best way to go. They are pricey and difficult to "roll" when compared to EL34's or KT-88's.

From what I know, lower impedance may run at slightly higher distortion levels. Many tube amps can handle 4 ohms or less but 8-16 ohm speakers are usually much more tube friendly.

Bartokfan, you seem to be asking the same, albeit worded differently, question over and over. If you are doing so because you are cautious, then it is a good thing. If you do so because you don’t like the responses you have been getting, it a bad thing.

I am going to disagree with Ralph on both speaker impendence and the power that is required to drive them.

A speaker with a nominal load of 4 ohm should not be a problem for a tube amp. The vast majority of tube amps will have 4 AND 8 ohm output taps, so 8 or 4 ohm rated speakers is not an issue. You simply use the appropriate tap off the back of the amp. Of course, all bets are of if your amp does not have this feature.

Secondly, 40wpc is plenty for an 89db rated speaker. I use a 12wpc SE amp on 88db speaker and the bass is tight and it can pound the walls down. I also use a 22wpc 6C33 based SET amp now and again, and if I had to turn that up my ears would bleed.

My speakers (Meadowlarks) happen to be well suited to tube amps, so much so that I get the best out of my amps. I am sure I get way higher distortion free SPL levels from my speaker than I could, had I been using speakers that are not tube friendly.

Your speakers are going to make or break your tube system, and the choice should not be made based on looking at rated sensitivity and nominal impedance only. I would suggest you talk to the manufacturers of your speakers and get their opinions regarding the use of tube equipment on their products. I doubt any manufacturer will advise you on an amp that will make their product sound bad.

Regards
Paul

Anytime you are investing in tube amplifier technology, that investment will be best served by a speaker that is at least 8 ohms or more.

Tube amps, with rare exception, have reduced performance into four ohms.

Given that you have satisfied that part of the issue, the next is efficiency. 40 watts with a speaker that is only 86 db is not going to be a lot of power unless you happen to listen nearfield, regardless of the type of amp.

SETs in particular have certain advantages of low level detail over conventional push-pull, but to tap that advantage you will need a speaker that is a good 10 db more efficient if your amp is 40 watts! Otherwise although it might work 'OK', it certainly will not be meeting its design goals.

Hi ...I like my solution to the same situation you have. I like the SET tone but I want to be able to use a wide selection of speaker. The answer for me was the TAD 60 power amp. It is very flexable in that it is rated at 30 watts in triod and 60 watts in UL mode using kt88 or 6550 powers tube. Using el34 , 6ca7 and the like has a little less. However the neat thing about this amp is that you can bias it into Class A and it sounds very much like an SET