speakers with a "smooth" impedance curve

I'm not really sure any of the above loudspeakers have a "smooth" impedance curve.

What's more, I'm less an adherent of this mantra than most. Tube amplifiers prefer higher impedances, and most tube friendly loudspeakers have far more wild impedance curves than the conventional wisdom of smooth impedance curve thinking would ever lead a person to believe.

Why? With most loudspeakers (multidriver and parallel crossover network), the requisites (a bevy of crossover correction/compensation circuits) to produce this desired smooth impedance curve do a lot more harm than good in terms of making the loudspeaker more friendly to a tube amplifier. Put it this way, in order to attain this smooth impedance curve, more crossover parts are required, and crossover parts act as speed bumps in terms of a tube amplifier putting power into a loudspeaker. Beyond that, such "correction" circuits rob the music of life, vibrancy, and immediacy, even if the partnering amplifier seems up to the challenge of blowing through those speed bumps.

As an alternative to seeking a smooth impedance curve, look toward loudspeakers that offer as simple a crossover topology as one can find, and several of the above loudspeakers mentioned above fit that paradigm.

Totem Forests are a possibility if you find their sound to your liking. I believe they don't dip below six ohms and are priced well under your $5000. mark. This will leave alot of dollars to cater to the system with cables, etc. I am getting beautiful, magical sound from the 8 ohm taps of 15 watt mono amps. And yes, the system will play loud and rock when needed.

So now your mantra becomes "a smooth impedance curve above 8 ohms with a first order crossover ."

Good luck.

Most Tannoy's are very easy to drive.

Having used a particularly load-sensitive tube amplifier in designing fairly high-efficiency loudspeakers, in my experience smoothing the impedance curve via additional crossover componentry does not have a downside. Electrically, the amplifier sees the net impedance curve (including its phase), rather than seeing numerous individual components. Smoothing the curve (and reducing its phase angle) is beneficial.

Let me give an example. A friend of mine has speakers whose impedance curve wouldn't work well with an OTL tube amp, so I designed an outboard filter to smoothe the impedance curve. Not only did this work with the OTL amp, but he also reported a significant improvement even with his solid state amp - which is what his speakers were originally designed for.

You can read his account here:

http://www.audiocircle.com/index.php?topic=56415.0

If the additional circuitry was somehow detrimental, but just happened to synergize well with the tube amp, then surely that detriment would have been revealed by my friend's high-resolution class-A solid state amp. What he said:

"...also mentioned even my current SS amp's performance might improve w/ this filter. Sound quality was indeed improved: smoother, more ease, less tension, less grain, tighter focus + increased musicality, image/stage improved a lot...etc. The difference can be heard even in the next room."

I think the effect he describes comes from the reduced phase angle of the impedance curve; at any rate, there was no detriment reported.

Duke
dealer/manufacturer