Can the KEF LS50 rock?

I totally agree with Bob's excellent response.

"I would like to know how they perform with rock music and if any deficiencies would be cured by pairing a sub."

Yes, the deficiencies would be cured by pairing a sub, but only with a high pass crossover as Bob described. Your Rel T5 has a low pass crossover for its input signal, but this has no effect on the main speakers. They would still be playing full range. Also, with the Peachtree Nova 125se, there is no way to use a line level (RCA connection) high pass crossover, separate box or built into a different sub. With the current equipment, your only option would be a speaker level high pass crossover.

Keep in mind that this is not just an issue with the LS50, but any small speaker.

Hi,

I am using a speaker level connection as per Rel's recommendation. 

From the manual:

  The HIGH LEVEL, unbalanced, dual-channel (stereo) input is via a Neutrik Speakon connector which is connected to the power amplifier’s left and right channel speaker terminals. This has the advantage of ensuring that the REL receives exactly the same signal as the main speakers. This means that the character of the bass from the main system is carried forward into the sub-bass. This is a very important point and together with the REL’s Active Bass Controller (ABC) ensures far superior system integration of the sub-bass with the main system.

This is how I have connected the sub.

brimel1974,

I'm sure the recommended connection from Rel is the best for the T5, however this has no effect on the main speakers. They are still playing full range and the issue remains. As I previously stated, with the current equipment, your only option would be a speaker level high pass crossover inline between amp and main speaker to solve the issue.

The signal from the speaker terminals to a REL is replete with whatever crap is on that line, primarily back-EMF. Thus the sub is seeing the same signal as the speakers especially given the 100k+ input impedance of the REL's high level inputs. I have owned five RELs over the years. They work as advertised. I have no connection whatsoever to the company (or any AV company for that matter). They simply work, and in ways you wouldn't think a sub would work. They RAWK!