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

Thanks Atmasphere and elevick for clear concise answers. I can finally grasp the issues. I will be dealing mostly with huge orchestral music and though I do not listen to loud vol, never more than 10 oclock on my JOR, still for a 845 tube the load may be too much for a 86 db speaker. The fact that its 8 ohms helps, but not much. With me speakers come first and so hope my 6550 tube will do the job. Next week will be the first time I will hook her up. Also i realized (was unaware of the ohm issue)the Tyler Lin Sig Sys is a 4 ohm speaker, so my dream of owning that model has changed now to Tyler's Lin Super Towers which is a 8 ohm and offers 4 W18's midbass per cabinet, which actually suits orch better as most cello, trombone notes fall in the range, not much in the below 35 hz. I see its important to research well before making any decision.

Bartockfan, FWIW, while you are doing your research factor in a couple of more issues, or at least possibilities....

1) Its not some much whether it's 4 or 8 ohms for a well made PP tube amp, its about the impedence curve and the minimum impedence. Some tube amps do quite well down into the 2ohm area and even come with 2 ohm taps. Its much more about the design of the actual tube amp than anything else generically speaking. Its also important to understand the actual output impedence curve of the amp and its synergy on the impedence (curve of the amp).

2) Be sure that the bass below 35 hz is unimportant to you by what you actually hear in your room, not just by looking at the supposed frequency response of instruments. If for example your room has a null in the 35 - 40 hz area your going to have nothing below 35hz to reinforce the bass which even starts to resemble the deep bass you would hear in a hall. Now if you room is flatish down to 35hz and you have a node at 30 hz the Towers may be more than enuf.

Perhaps its just because I don't listen to the Sig Systems at ear bleeding levels but I have no problems with tube amps with 40 to 80 watts in my medium sized room. In my room the Super Towers would not work due to room acoustics.

FWIW.

Newbee's first point on the impedance curve of the speaker is taking you to where you really need to be. I'll add in phase angle as well.

One other parameter I think that should be discussed is the crossover topology. How simple or complex the crossover is makes a tremendous impact into whether the loudspeaker presents an easy or difficult load. Tube amps like first order crossovers better than second order crossovers, and second order crossovers better than third order crossover, and on and on. On top of that, things like Zobel networks, trap circuits, and the like can turn things completely on their head. Take some famous loudspeakers, such as Thiels, with first order crossovers that so many compensation circuits - a total bear to drive.

The best generality I can offer is that you want the crossover as simple as can be. The opinions on single driver loudspeakers being a good match with a tube amp is true - because there is no crossover to suck up the power. Of course, you do give up frequency response.

Far too often, sensitivity and nominal impedance give such an incomplete picture that you simply need to walk away from what people will tell you, and give it a try. THAT is the only way you'll know...