help w/amp demo

On Friday, Sounds Real Audio of Golden, Colorado will be coming to my home to demo its Dehavilland 50a 40w tube amp w/my Aerial Model 9 speakers (full range, 90db sensitive, 4ohm). Given how good the 50a sounded at RMAF, I am very excited.

Nonetheless, while the 50a is designed to drive a bigger load than its specs would suggest, I am a little skeptical that it will be a good match w/the 9s (although I am hopeful). Thus, I have been doing a lot of reading on how to determine whether an amp is a good match w/a speaker and has enough power. In general, I think I have a handle on it.

One thing I don't understand is mention of a speaker making the amp "work too hard" as opposed to drving it w/"ease". I only understand that in the most general sense. My question is, how will I be able to tell if the amp is having to "work too hard" in driving my speakers? What should I look/listen for? Also, more generally, if people have ideas for how to decide if the amp is a good mate, I would love to hear them.

Thanks much.
Listen for controlled, detailed, and extended bass.

Listen for extended highs.

Turn up the volume and play some music with wide dynamic peaks and valleys. Are the peaks reproduced fully, or are they constricted?

Frankly, unless you've heard your speakers with an amp that's a good match, it may be challenging to know what they sound like when properly matched.

Is there an experienced audiophile or two nearby who could come listen with you?

DeHavilland showed with 88db Wilson Benesch Curve loudspeakers at RMAF. The speakers were 6 ohms nominal with a 4 ohm minimum specification. They did sound quite good in a smallish room with a nearfield set-up.
Thanks Tvad. I think my current power is a good match-Classe CAM 350- I am just interested in the richer sound a good tube amp can provide (at RMAF, I always gravitate to the tube gear). A friend of mine will attend the demo as well, but he is no more experienced in this area than I am.

How can I determine if the amp is being strained? Or, should I just listen for bass and dynamics?

How can I determine if the amp is being strained? Or, should I just listen for bass and dynamics?

Shredder (Answers)
Just compare it to what you're used to hearing with the Classe amp on dynamic material. You'll know if the music sounds right or not.

BTW, I was impressed with the 50A amps. In fact, I contacted Kara yesterday, but I don't think the situation is going to work out for me (no local audition, etc).
What a way to go. Wish a had a 'Sounds Real' type dealer in my area, one that comes to your system. That is the best way to determine whether a significant improvement in your system sound can be achieved.
Excellent suggestions by Tvad, as usual. The one thing I would add, with respect to your question about having enough power, is that a key variable is the dynamic range of the music you listen to.

I also have 90db speakers, in a 13 x 20 room, with the listening distance being about 9 feet. I am currently using an 80W tube amp (keep in mind that is only 3db more than 40W). On well recorded, minimally compressed, wide dynamic range classical symphonic music (which I listen to a lot) I find that the 80 watts is adequate, but just barely. A small nudge on the volume control above the position I normally set it to will result in slight but noticeable clipping.

On virtually all other kinds of music, listening at loud but sensible levels, the 80W is very easily adequate. A possible exception being things like some of the 1980's Sheffield Labs direct-to-disk LP's, some of which have dynamic range that is not likely to be encountered elsewhere. I haven't listened to those yet since I replaced my 200W solid state amplifier, which could handle them easily with the 90db speakers.

Best of luck!
-- Al
Additionally, the sensitivity rating of the speaker can be less of an indicator than the impedance curve or consistancy. Tubes do best with a fairly flat (or certainly not wide fluctuations) with the impedance load. I don't recall off the top of my head how the curve on the Ariels is. If it is a fairly flat curve, you are probably okay. Of course, for $450 you can look into a Paul Speltz autoformer which is supposed to help to address this (at least from what I understand of it).
Thanks a lot everyone. Very helpful.

BTW, I listen to a wide variety of music from Rock to Jazz to Funk to World. But, no classical. I get the impression that the dynamic limitations of a less powerful amp may be less of an issue for non-classical music, which is less dynamic?
Oh, and I just looked at the Speltz autoformer (I use his anti-cables and ics and think very highly of them). Anyone have any experience using such a device?
I get the impression that the dynamic limitations of a less powerful amp may be less of an issue for non-classical music, which is less dynamic?
Yes, with some isolated exceptions here and there, well recorded classical symphony orchestra will have much greater dynamic range, and therefore require greater amplifier power, than pretty much anything else (including other forms of classical music, as well as the types you mentioned).

A particularly dynamic recording of classical symphony can easily have occasional brief peaks that are 30 db or more greater in volume than soft passages (30 db being a factor of 1,000 in terms of watts). Since it is typically the lower volume levels within that range that comprise most of the music, the volume control will be turned up to a much higher position for that kind of music than for, say, rock, most of which is compressed such that its volume varies over a range of only a few db.

So the occasional brief peaks in a well-engineered symphonic recording will demand much more power from the amplifier than pretty much anything else.

-- Al
Take advantage of your willing dealer and reward him with a sale after you figure out what sounds good to you. I home demoed a well regarded 35WPC integrated amp with my PSB Synchrony One (88db sens) speakers and it was a complete disaster since it didn't have enough power for my speakers/room/preferences/whatever. Even acoustic piano notes distorted at "moderate" levels. I am accustomed to a bunch of SS watts. Sounds like you have a great dealer so let him do his job and give him the biz'.
The autoformer did not help when I purchased a tube amp to drive my previous speakers that had a very uneven impedance curve. The device has an overall affect but does not fill in the gaps. My 35w p/p amp does drive my 89db speakers pretty well - but, they have a fairly flat curve.
tube or ss, youre gonna need 'juice' for those speakers. atmasphere, arc and mac make some beefy units that match well eith your speakers....that said , your classe is a class act.
Thanks all, I will report back. And, yes, I agree, Jim Ridell at Sounds Real is great.
BTW, I love Classe amps. The 350 is my second. I previously owned a CAP 150, which is a terrific integrated and a great value. I am not looking elsewhere because I don't think highly of Classe, I just want to explore a different direction and at least at audio shows, the tubes always float my boat.
Shredder-Did you talk with the speaker or amp manufacturer to get their point of view?
I spoke with both Aerial and Dehavilland. Both said, "maybe it will work, you should give it a listen". Kara at Dehavilland then hooked me up with Jim at Sounds Real for a demo.
Thanks for all the input, really helped with my audition, which ended up lasting the entire weekend (Jim kindly let me keep the amps over the weekend.

Fot those interested, the combo was a much bigger success than I had expected. I will post a detailed review later in the week when I have more time.