• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

What speakers to go with tubes ??

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Tubes amps have trouble driving some ultra low-impedance speakers, usually electrostatics, in the sub 4 ohm range. Any speaker with an average impedance near or above 8 ohms should work well. My own preference (I have a small house) is for mini-monitors such as the old BBC LS3/5a and its many variants, but to each his own - there are dozens of nice sounding designs and telling an audiophile what speaker to buy is like arranging a marriage.
 
Bill*B said:
Tubes amps have trouble driving some ultra low-impedance speakers, usually electrostatics, in the sub 4 ohm range.

Technically true, but ironically, ESLs driven by tubes is a sonic marriage made in heaven. In the upper registers where ESLs drop down low in Z, the energy levels in music are much less, so that tube amps often can work better than expected.
 
Your valve amps are going to be less "load invariant" than mainstream solid-state amps. Mainstream solid state stuff (Pass is exempt from this) usually incorporates very high internal gain, and then wraps a high-order feedback around it. This helps deal with the odd-order harmonics, stabilizes the gain, and reduces the output impedance and THD to vanishingly low numbers. The end result is that modern mainstream solid state amps can pretty much push any loudspeaker’s impedance. Unfortunately, loudspeaker manufactures know this, so they don't take care of carefully tailoring the impedance curves. It's not on their list of things to worry about, because big amps can compensate.

You should look for a tube friendly loudspeaker, a speaker that reduces aberrations in the complex impedance. You can see this on impedance curves (found in Stereophile and occasionally from the speaker manufacturer). Look for two things: the impedance dropping below 4-6 ohms and the phase angle. If anywhere on the graph (usually low frequencies, correlating to a resonance, crossover, or port) the impedance droop occurs at the same frequency as a large negative (capacitive) phase angles, your valve amplifier will fumble. So look for a loudspeaker with stable impedance, no severe droops, and no low impedances that correlate to large negative phase angles.

You won't need a "load invariant" amplifier with this speaker, so your amplifier selection becomes much larger: valve amps, SET, amps with no global feedback, Pass Zen (discussed elsewhere on diyAudio), etc.

Big horn speakers are good candidates, although I haven't researched any. It seems that the smaller French and British makers are also cognizant of tailoring impedance curves. Focal is an exception, as their speakers need hordes of power and low output impedance to drive properly.

I have a “short list” of speakers. The classic Rodgers speaker is a good tube-friendly design. New designs are (listed in order of preference, in my opinion):

- Coincident Technology. Their monitor-sized speaker runs about $2k. Can work with SET.
- Triangle Acoustics. You can pick up a Comete for less than $1k. Larger models are more expensive, but equally suitable. Some work with SET.
- Opera Callas ($3k). Excellent reviews, but expensive. Needs more power than SET.
- Living Voice (such as the IBX-R).

There are others that I suspect are good, but I haven’t researched them yet, such as the Joseph Audio, Revel Concerta F12, and Spendor.
 
I babysat a Concident Triumph Signature and they sound fantastic driven by my 2A3 and 300B amps. Too bad, not affordable for me.

Other speakers I tried-

1. Omega from Luis- not much bottom end. These are the earlier generation. But Luis is a very nice guy!

2. Spendor S3/5- very good sounding indeed but needs power. Makes my 2A3 amp clips (expected) but sounds very good with Anthem Amp 1 (at least). My friend bought this pair on my recommendation.

3. Triangle Comete 202- the bass of the comete 202 is a bit more solid and punchier compared to the eric-1 which will make r&b and rock fans even happier. however, on blue man group's rod and cones both speakers sound equally great in my room.

4. Opera Audio Eric 1-
big sounding. these speakers are kinda small, with front port, and a little heavy but not as heavy compared to my Infinity Kappa 200. it may have something to do with the enclosure or the drivers. the soundstage is beyond the speakers, and into the room.

5. Various version of Brines' speakers

6. A couple of versions of the huge Voigt

etc.

In the end, I settled for a DIY and I'm happy.

Please do note that I'm a SET guy, type 10 to 300B 😀
 
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