HELP advise PLEASE - Focal Sopra 2 Speakers - I want a tube amp but " Min 2.6ohm @ 104Hz "


HELP PLEASE advise bought a pair of Focal Sopra 2 Speakers that I absolutely love.

I want to use an integrated tube amp with them but the measurements worry me even though many Sopra owners say they happily use tubes with these speakers.  


HERE IS THE ISSUE:

  From HiFi News September 2015, lists Minimum impedance is around 2.6 ohms at 104Hz. Combined
with high impedance phase angles at low frequencies this results in a minimum EPDR (equivalent peak dissipation
resistance) of 1.1ohm at 85Hz – challenging to the partnering amplifier.

Can I used an integrated tube amp and hope for success? 


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From HiFi News September 2015, minimum impedance is around 2.6 ohms at 104Hz. So the amplifier should be capable of approximately doubling its 8 ohm output power into at least 4 ohms and preferably again into 2 ohms.
Min 2.6ohm @ 104Hz. Focal claims 91dB sensitivity for the Sopra No 2 but our measured pink noise figure of 88.2dB falls almost 3dB short of this. Low impedance is a factor in achieving this figure: Focal specifies a minimum impedance of 3.1ohm (which would indicate a 4ohm nominal rating rather than the specified 8ohm) but we measured a dip to 2.6ohm at 104Hz. Combined with high impedance phase angles at low frequencies this
results in a minimum EPDR (equivalent peak dissipation resistance) of 1.1ohm at 85Hz – challenging to the partnering amplifier. The forward frequency response [Graph 1, below], measured on the tweeter axis, is essentially flat in trend with just a mild presence band dip.




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The VAC has assorted output taps, so that is nice in your situation. I would experiment with a SS amp as another data point/ reference if practical.  
Been thinking about SS and tube preamp. I wasn’t but a few of you guys mentioned the idea and it has started to stick with me. I want the Linear power and control from SS but now need that tubes sound. The hybrid integrated I’m now borrowing is so good it’s tough. Wish I could afford it but I can’t. What do you think of GamuT D-200 MKIII and a Alnic L4000 combo. The transformer coupled output on the Alnic provide nice lower output impedance and Gamut is a little tuby on its own so was thinking good match for Focal Sopra 2? Think this would be better then a hybrid like a Mac 352?
Checkout Convergent Audio Technology (CAT) or ARC for tubes driving a tough load.

VAC has 2 ohm tap ... found one VAC 200IQ had trouble driving Wilson Sabrina so probably need 2 running in Mono.

You can get the flavor ot tubes with an Hybrid  which then has a high current sold state output stage

We have the suberb unison research unico 150 a fantastic italian made tube Hybrid with 180 watts on top you Will have no problens driving your speakers

Dave and troy
Audio intellect Nj
Unison research dealers