Amp and speaker matching.

When someone asks if a cetain type of amplifier will drive their speaker I am assuming they want to know if the amplifier will drive their speaker properly. I have tried many combinations like driving Maggies with 15 watt Quad tube monos and driving the giant Duntech Sovereigns with a 14 watt single ended amp. Although I was able to play music through these speaker with these tiny amplifiers the speakers did not sound their best. Simple music is ok, but on complex large scale music at high volume, forget it.
Stereophiles favorable review of the Dynaudio Contour 3.0 was with amplifiers like Bryston 4B-ST, Bryston 7B-ST monoblocks and Levinson 331.

Rrog is spot on. The 70 watt tube amp will work and produce nice sound, but the power reserves and headroom will not be there for complex and demanding material at higher volumes. The speakers will not sound as good as they could as they will be dynamically limited in respect to your current amp.

HI Grannyring,
It`s hard to know sometimes,I suspect it depends on the particular tube amplifier. Two amps with the same power rating can in reality be night and day different(transformer,power supply robustness etc.). Jerroot and Ard`s experiences suggest they got great results rather than merely adequate compromise.

It'll work and might sound decent but not an optimal match. Getting optimal amp/speaker match is essential to get the best objective results.

86 db means that you will generate a SPL of 86 db at 1 meter with 1 watt of power.

It is easy to get confused about this! In this case the spec is Sensitivity, not Efficiency. Sensitivity is 2.83 Volts at one meter, meaning that with a 4 ohm load the power is 2 watts. So the *efficiency* of this speaker is more like 83 db (since 2 watts is 3 db more than 1 watt) while the Sensitivity is 86.

There is also the issue of whether tubes will sound OK on the Dynaudios regardless of the power; IMO they will sound OK but the speaker will be the sort of load that has a tube amp at a disadvantage. For more about this see

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

If you really want to get the most out of your tube investment dollar, I would get a different set of speakers! OTOH if you want to optimize these particular speakers you are probably looking for a transistor amplifier or a very large tube amp (+200 watts).