Is this enough power?

Does a 30w per channel 845 SET amp have enough power to drive 88.6 db at 6 ohm speakers at moderate level of volume. room is 14x18x9 and open at one end into the kitchen. mostly listen to jazz and classical.


Happy Listening
speaker and amp specs tell only part of the story and the power needed varies based on design etc...

keeping this in mind, looks like a decent match imo
If the speakers are of moderate phase angle, you're good to go.

Large phase angles or large phase angles at impedance mins will tax the amp.
A key factor is the dynamic range of the music you are listening to (the difference in volume between the loudest and softest notes). You mentioned listening to classical music. Well recorded, minimally compressed classical symphonic music can often require 1,000 times as much power on brief peaks as on soft notes (1000x power = a 30db difference in volume).

So I would expect, for instance, that the system would have problems dealing with the bass drum on many of the older Telarc recordings. Likewise for some (many?) well engineered symphonic recordings on other labels.

Jazz and chamber music I would expect to generally be no problem.

-- Al
My room is a 14x 18x 24 and I drive a pair of Focal monitors (1007Be around 89db) with a Cary SLI-80F1 in Triode mode (40w/pc) to extremely high levels (IMO). I listen to all forms of classical and jazz (vocals) along with classic rock.
I'll add some personal experience to my earlier comment. During the 1990's I was using 90db speakers having easy to drive impedance characteristics. In addition to some high powered solid state amps, I also used several different high quality vintage tube amps in the range of 20W to 60W, including Marantz 2's and 9's among others. This was in a 22 x 13.5 x 8 room, with a listening distance of 11 feet.

Recordings having either narrow or what I would characterize as moderate dynamic range, including many symphonic recordings, could be played with any of those amps at much louder levels than I or most people would want to listen at. However, occasional brief peaks on many symphonic recordings on labels such as Telarc, Sheffield, Reference Recordings, etc., could easily clip the amps that were in the 20 to 30W range. Using the Marantz 2's in triode mode (about 20W, from push-pull EL34's), a few recordings could actually arc the tubes, producing a bright blue flash.

So I guess the bottom line is that you'll be fine with most recordings, but not all.

-- Al
My experience has shown that 30 watts may not be enough if you listen to piano or classical as the amp will most likely clip. I consider moderate levels to be up to 85 - 87db or so. Problem is you need headroom my friend and I really think your going to have problems.

Not all recordings have the same output level as you know and I have found a system like yours will run out of gas with 30 watts (at times). The amp will strain and be pushed with little or no headroom remaining. Perhaps you could "get away" with it and have it sound good most of the time. However, throw in a 100 watt tube amp and you will immediately sense what I am trying to say here.
Your speakers are rated at a nominal impedance of 6ohms but what matters to your tube amp is the real life impedance swings during varying frequencies. If your speakers offer a relatively benign 6 ohms and your amp has a 4 ohm tap, you should be alright. As other posters have mentioned, if your speakers present too much of a load to the amp, dynamics will be affected along with a flat uninvolving sound. I love 845 based amps, but they do require more attention to speaker compatibility.
You will get about 102db max continuous. Add in dynamic peaks and you won't be listing to anything loud. At moderate volumes it should work.
I drive my B&W CDM9NT´s with a Bel canto SETi 40 (845 tubes) which have a nominal impedance of 8 ohms (the impedance curve indicates that about half of the curve stays below 6 ohms!!). I lisen to rock and reggae at a moderate to high volume most of the time with no problems at all. My room measures 10x19x9. IMO you will not have problems with your amp.
Thanks for all the responses.

I found an impedance graph for the speakers.

Between 1k and 20k it is 6 ohms and peaks at 12 ohms at 5k.

From 1k and below it is ruler flat at 4 ohms.

Does this new info alter any of the comments?

the amp does have a 4 ohm and 8 ohm tap. Not sure which one would be the best to use.

Experiment with both the 4 and 8 ohm taps as you cannot hurt your amp or speakers.
Try both taps and use the one that pleases you most! In my set up I found the sound changes a bit been the 4 ohm tap the one I like most because the bass notes are more tigh and the music sound more "relaxed."
Good job getting the impedance data. sounds fine.
However, your job is not done yet! See if you can find some phase data. This IMO is the true test of 'good load/bad load'. Huge phase angles at low impedance will really drain all but the most robust amp. Speakers which are heavily capacitive do not like tubes....or perhaps the other way 'round.

Trying the various taps on the amp? Best idea yet.
Magfan - is there anywhere i can go to find out more about phase angles. that is something i am not familiar with. Does it have something to do with the slope of the impedance curve at a specific frequency?
That does help and the amp will work. I still caution you that more watts would help your system reach it's full potential.

This will be true on all classical recordings that happen to have low output levels. Your room is large with the kitchen figured in and 30 watts won't let you realize the full weight, scale and impact of your music.

I also found this and used google translate. Is the frequency response and/or axel deviation comment related to phase angles? Not sure if the wording is different because of the translation.

"Also by measurement the relationship between S-1EX and S3-EX is unmistakable. The frequency response looks almost like drawn with a ruler and extends down to about 40 Hertz. From five kHz is a slight ripple into play when the axial deviation of 30 degrees (dashed line), however, is negligible. Straightened out into the room, the Pioneer actually sounds a bit faster and more coherent dunk. The impedance is danzverlauf critical, and the jump response is in order, with the enormous time accuracy of their sister, it can not record the S-3 EX bass but because of the delay."

Phase angle is how much current leads or lags voltage.
In a pure resistive circuit they are in sync.

The wiki has some good illustrations.

For stereo / hi fi, this presentation is most useful

The main thing to remember is that any time current and voltage are not perfectly in sync, less power is delivered to the load.

It is pretty much purely electrical. Maggies for example, if you simply look at impedance may be considered a difficult load. This is not necessarily true, since the phase angle is moderate thruout the frequency range. Other low sensitivity speakers which like tubes may be like the Harbeth.

Here is a good example of a fairly large phase angle coupled with a low impedance dip. I don't know if these guys work well with tubes, or not.
The phase angle is not a single number or a set of numbers. The data will be in the form of a frequency response graph, but with + and - phase angle on the vertical axis. Stereophile prints such data on the same graph that plots impedance at various frequencies. What makes a speaker difficult to drive would be an extreme phase angle (e.g. -45 degrees) at a point where impedance is at its lowest point, and particularly if such combination is at a frequency with a lot of musical energy (e.g., 80-200 hz).

Fortunately, reports like that of Stereophile, will not only provide data but an interpretation of its meaning so you don't really have to know how to read the graphs.

My guess is that 30 watts may work, provided you don't play the system at really high levels. For reasons I don't quite understand, I find that distortion from a shortage of power will be most evident on works with a large chorus. At a subjective level that does not seem that loud, a work like Rachmaninov's Vespers may begin to sound distorted if your amp is not fully up to the task (maybe its because human hearing is most sensitive and tuned to the human voice). If you get a chance to try the amp, bring along such works.

One of the advantages of a good SET amp is that they are quite musically satisfying and sound right at lower volumes so you probably would not really need to push them that hard. I personally don't mind trading off the rare times when I really want to play the system at extreme volume in order to get the desirable characteristics of a good amp for 99.9999% of the time.
Good, question--but YOU, are the only person that can answer this question. It works for ME, on paper...but that doesn't mean you'll be satisfied.

Good listening,
Thanks again for the explanations. I finally found a graph with phase.

Looks like the lowest phase angle is approx. -40 degrees at 30Hz where the impedance is 10 ohms. Other than that dip, the phase angle is above 0 degrees.

From what I understand from the above posts, this means this should be an easier speaker to drive and that the 30w of SET should be enough.

Have also found that most tests show that the speaker is 90db/2.83V/1m. Maybe the manufacturere specs are conservative.
Looks like the lowest phase angle is approx. -40 degrees at 30Hz where the impedance is 10 ohms. Other than that dip, the phase angle is above 0 degrees.

From what I understand from the above posts, this means this should be an easier speaker to drive and that the 30w of SET should be enough.

Have also found that most tests show that the speaker is 90db/2.83V/1m. Maybe the manufacturere specs are conservative.
I would still suggest caution before reaching that conclusion. Given that the speaker's impedance is 4 ohms below 1kHz, its efficiency in that region (where most of the power is typically required) is only 87db/1W/1m, because 2.83 volts into 4 ohms corresponds to 2 watts.

Assuming that you are referring to dynamic (non-planar) speakers, it can be calculated that 30 watts into each of the two speakers corresponds to a 95db sound pressure level at a distance of about 10 feet. As I indicated earlier, that should be good enough for most recordings but not for all.

-- Al
If a trial listening period for the amp can be had.. there's your answer.

Go with Al's comments... and later on... get one more amp, or more sensitive speakers..

Maybe you could also enclose that room with pocket doors or a pre-hung one andd a little build up around it... Otherwise, you're actually filling sound into the whole of the total cubic feet of the entire spaces. Listening area, AND kitchen area.

My situation (roomwise) was similar a while back. I've since closed off my room for a more dedicated listening - vviewing arrangement. I had pocket doors separating the kitchen from the living room, and a pre-hung 3/0 closing off the hallway to the rest of the house on the opposite side of the room. the room is roughly 14 x 21 x 8.3 with a gently sloped ceiling.

It helped the bass out tremendously. Imaging and separation too. Night and day diffs for viewing.

I ran some higher eff speakers with about the same sort of imp curve, roughly, off my 4 ohm tap on my 120 wpc monos... making it/them output half of their power at 60 wpc. Never listening to exceptionally high levels (avg low 90s) regularly, with occassions running them at the high 90s and never noticed any issues.

The info Larry and Al have given is key and prudent as well as accurate I'm sure.

the full realization of musical enjoyment comes from having a system which can reveal the honesty of its emotion and it's voice. Meaning, you might want to consider some nearfield listening situations. Getting closer to the speakers with your chair.

Ultimately I reverted back to the 8ohm taps and never looked back. the 4 Ohm taps yielded a warmer softer more romantic presentation... and the 8s showed a brighter, fuller, exceptionally more dynamic face of the music. Including better bass. Much better bass.

So as Larry said, the presentation might be alluring enough to offset a desire to raise the fun knob...

I feel often that we tgotta make compromises or replace things we may not want to in order to gain that which we seek, better. So if you love the amp... or love the speakers ... shuffle off the one you don't love quite so much down the road... as I'm figuring you ain't married to either one... possibly the amp ought not be bought unless the idea of new speakers is on your horizon.

Either way.. good luck.
I had hoped you'd look at the links a little better.

One thing I didn't say and Larry didn't touch on either is that phase angle has 2 aspects. The general measure is 'reactance'. However, there are 2 kinds of reactance.
Capacitive and inductive reactance are both measurable but it is the capacitive aspect which will give tube amps a problem. I believe in the stereophile graphs, that is the part below the 'zero' degree line.

Look at the link i provided to the 'Smith Chart' and go to the 2nd page for the presentation I prefer. It is both impedance and reactance represented by a SINGLE line in a big curly q shape. The distance down the line is frequency so that is tougher to figure out. The tiny curly q's are crossover frequencies, usually
Thanks again.

I did look at the links and found them to be a wealth of technical information that for the most part was over my head.

From these posts and my research into the Pioneer EX speakers, i do have a much better appreciation for their design/charts, etc...

Regardless of the actual specs, the speakers sound amazing. even paired with the SET amp. i do realize that there will be some compromises depending on volume and typed of music.

Once again, thank you for all the information.