@erik_squires - Hi Erik, so I asked this directly of Legacy:
What is the minimum impedance of the Signature speaker, is it 2 ohms below 100 Hz?
Their response: "The signature line can go as low as 3.5 ohms"
So, pardon my ignorance, but what does all this mean? Thanks!
Welp, there’s a number of published measurements showing this to be optimistic. As I noted elsehwere, I’ve found a couple of different models shown to be around 2 Ohms for most of the bass. This includes the SE and 20/20. Perhaps I’m misinterpreting the statement or the charts?
For any speaker that goes down this low it means that with many amplifiers the bass output will often be depressed relative to the rest of the range. See the separate thread on the KEF Reference 1 standmount which has exactly this issue.
The solution is a high-current amplifier of which there are many at various price points, but your average integrated amplifier probably wont’ cut it. For sure, almost no tube amp will work here.
At 2 Ohms, an amplifier has to produce 2x the current (Amps) as at 4 Ohms, and 4x the current needed at 8 Ohms.