Hey Guys,
Can you please help me understand how you achieve a higher sensitivity from your 3-way than your 2-way? Is the 15H used in the Joule?
Also, can you please help me - and whoever else is interested - figure out how 35 watts from a tube amp will power each speaker? One would think the tube amp would handle the 2-way, as a load, easier than the 3-way. However, the higher sensitivity and the assumption that the bad a$$ AT woofer has a flat impedance curve has me confused what would be handled with less effort.
Any help here? Thank you!!
Joule uses the Audiotechnology Flexunit 10" sandwich cone woofer.
It's all about the baseline sensitivity of the woofer. Everything else has to fall in line. Because the TD15H is a high sensitivity woofer, by definition it doesn't take much power to hit 90dB. In this case, well under 1W will get you there. The TD15H also has a relatively high impedance. Over most of it's range, it's impedance is above 10 Ohm, so it's a super easy load for a tube amplifier.
A two-way like Cirrus has a woofer that is covering the full range from below 100Hz, where baffle step losses occur, up to 2000Hz where baffle step is completely gone. That radiation space at 100Hz consumes approximately 6dB of the baseline sensitivity due to the woofer being away from the ground plane. So in the case of Cirrus, there's more loss of sensitivity than with the Nimbus or Joule due to the woofer's proximity to the floor boundary.
So in this case, the huge Nimbus is actually an easier load for an amplifier than the smaller Cirrus due to the types of drivers employed.
Joule also has the same advantages as Nimbus since the woofer uses the floor boundary to keep some of its sensitivity.
By the way, on Sunday at RMAF, we were filling our 75' long room with Nimbus using the Arte Forma Aida, a 3.5W SET based on the 2A3 output tube. There's certainly something special about a higher sensitivity speaker if you don't mind the larger footprint.
