Help Tannoy XT6F with Primaluna

Hello all.
Just got a pair of Tannoy Revolution XT6F speakers. They are supposed to replace KEF LS50s. I'm driving them with a Primaluna Prologue Premium power amp. The new Tannoys sound awful with the Primaluna. Very peaky upper midrange and not much bass. Pretty unlistenable. Tried them with my old Rotel RB990 solid state power amp and they sound much much better. Tried the 4 and 8 ohm taps. Tried the stock Primaluna tubes and some KT 150s. No good. The Primaluna sounds great with the KEFs. Any ideas? Thanks in advance.

The Tannoys have a 90db sensitivity rating so the Primaluna should drive them fine. Have they had time to break in? I would play them for at least 50 to 100 hours before critically listening. Also, cables make a big difference, what are you using? Some speakers just don't like tube power. I would never use tubes in the power amp section to drive my Dynaudio speakers. They do not like tube power. So I use tubes (10 of them ) in the pre amp section to inject that tube quality I love.




P.S. I would do what ever, to get those Tannoy's sounding right, great choice!

Give them a month to break in. Hopefully, they will sound much better. Mine did -- not the same model, though.
I had used a Japanese Triode integrated 300B amplifier with a pair of Tannoy DC 8's and that sounded really really good.
I had used a Japanese Triode integrated 300B amplifier with a pair of Tannoy DC 8's and that sounded really really good.
Ben, I agree with the earlier poster that additional breakin may very well help. However, although most Tannoy speakers that I am familiar with have tube friendly impedance characteristics, unfortunately I suspect that the root cause of the problem in this case is that yours do not.

I suspect that the impedance curve of your XT6F speakers is similar to the one shown for the XT8F in the graph at the very end of this review. As you'll see, the impedance of that speaker, despite its 8 ohm nominal rating, is around 3 ohms in much of the bass region, rising to around 10 ohms in the mid-range, followed by a sharp rise to more than 40 ohms at about 4 kHz, followed by a decrease to around 10 ohms in the upper treble.

As a zero feedback tube power amp, your PrimaLuna undoubtedly has a fairly high output impedance, corresponding to a very low damping factor, although neither parameter appears to be specified. The interaction of a high amplifier output impedance with the speaker impedance characteristic shown in the graph will result in EXACTLY what you have described -- weak bass and an over-emphasized upper mid-range.

If the sound continues to be unsatisfactory following additional breakin, I suspect that among tube amplifiers a much better choice for use with the XT6F would be a medium powered Audio Research model, if you can find one used at a suitable price point. ARC designs tend to have significantly lower output impedances/higher damping factors than many other tube amps, in part due to the use of moderate amounts of feedback. Also, they tend to have robust power supplies, which may also be helpful with respect to the low impedance of the speakers in the bass region.

Good luck. Regards,
-- Al