Speakers and Tube Amps

The idea that an amplifier has to double power as the impedance is halved is problematic. I say this because **in general** tubes sound better than transistors and tubes do not double their power. Instead, they will (or they will attempt) to put out constant power (transistors will seek to put out constant voltage; if you do the math this is why they double power as the impedance is halved).

I know that there are many who will object to my statements above, so I want to be clear that while on the face of it, it appears to be the tube/transistor debate, it really isn't, see:

http://www.atma-sphere.com/papers/paradigm_paper2.html

for more information.

If you read the above article, then you know that all you have to do to find a speaker that works with tubes is to look at the speaker designer's intention: is he using tubes in the design of his speakers?

Audiokinesis, Classic Audio Reproductions, Quad, Lowther, nearly all horns except for the Avantgarde Trio, Coincident, High Emotion Audio, PHY, Feasterex, Audio Machina, ZU, Wilson, Vandersteen, Tonian Labs, Reference 3A... the list is extensive!! I would not worry about finding a speaker that will work for you, regardless of the tube amp you ultimately settle on.

Duke said it better than I can. FWIW Wilson has shown with Audio Research a good deal in the past and ARC has Wilson speakers in house. So despite the dips in impedance, Wilson's are 'tube friendly'.

The Wilson Watt has long been an example of the phenomena that Duke presented above. The speaker had a reputation some years back for being bright- around 2KHz. There was a tweeter resonance at that frequency, which anyone with a transistor amp would tell you was uncontrolled. The tweeter did in fact have a resonance, but Wilson controlled it with a 'band reject' filter, tuned to 2KHz, which caused the speaker to have a 2 ohm impedance at that frequency. The rest of the speaker was about 8 ohms; transistor amps would dump power into that filter, and tube amps would not make any power due to the filter. As a result the speaker sounded great with good tube amps, bright with transistor amps.

Cleaneduphippy, you can also have the case where the impedance goes high and the tube amp will put out constant power. This is OK if the designer expects that. Impedance dips are usually not a problem too, as you have to sometimes shut down the output of the amp right at the area of the dip, as in the case of the older Wilson Watts.

Electrostatics can have low impedance at high frequencies and very high impedance in the bass- tube amps will often play that with constant power at all frequencies and actually get the speaker to play bass, where a transistor amp will make way too much power in the highs (so it will be bright), and not be able to make any power at all in the lows.

Really, the best way to find out is to look at the designer's intent- what he uses for reference, what manufacturers are using his product, who he shows with at shows.