Yeh, I'm not talking about sensitivity matching, it's the impedance.
If the power amp has an input impedance less than x10 that of the output impedance of your Pre Amp. You will get an anaemic thin sound with rolled off bass.
Pre amps like the Rogue RP-7 which looks like it has low output impedance, actually needs an amp with at least 20k input impedance 50k would be better.
This is because its impedance rises dramatically as frequency falls.
For the RP-7 its 5.6kohm at 20kHz. yes 5600 ohm.
Many active speakers fall into the 10 to 20kohm range. I was just wondering if anyone knew what the input impedance of the Opals were, to help me match a Pre Amp to them.