Advice from anyone with Tangent RS4 speakers?

Well, I woud not be surprised if I am the only one that knows anything about these. They were made in England circa 79-81. They used drivers by Audax of France. An 8" bextrene woofer mid and the ubiquitous 1" soft dome tweeter that almost everybody was using at this time. The Bextrene driver was a nice sounding unit but was very inefficient at around 84 db and also did not handle much power, around 40 watts rms was it. So the RS4 is a very British sounding speaker, if memory serves, warm and full in the bottom and slightly rolled on top. Because it is so inefficient and very limited as to how loud it can play it is definitely not for headbangers. I would say that you need an amp with a little grunt to drive these. The NAD would probably do it. I would go with an amp that has a neutral balance rather than overtly warm simply because the RS4's are already on the warm side.

Good. That's just the sort of advice I was looking for. Thanks. I'll audition the NAD.

I guess you already bought your amp, but I can't resist sharing a few comments on these lovely old speakers.
I am listening to my RS4s as I type this. Bought them in December '78 and have never found a reason to get rid of them. No - they're not the ultimate audiophile loudspeaker, but incredibly difficult to tire of. Very warm, comforting, BBC sound. Not good for high levels (the crossovers tend to melt, leading to 1/2 hour's soldering to put everything back into the PCB) and not efficient - I have had best results driving them with something around 80-100W RMS. Currently they are playing MP3s from my PC via a 100WPC Crimson Elektrik (circa 1980) power amp. A couple of decent stands (shot-filled is good) to lift them about 18" off the floor tidies up the bottom end. Just don't drive them with anything that's woolly in the bottom end - my worst ever mistake was a Velleman valve amp - sweet at the top, but utterly suffocating in the bass. Get the amplification right and enjoy!

Just to add to this legacy thread. The RS4 were my first set of speakers, purchased in August 1978, after comparative demos agains the likes of Bose (301s!), Swallow, KEFs etc. They offered very pleasant tonal balance with subjectively a slightly recessed midrange and superlative imaging. I started off driving them with just the original A&R A60 integrated amp and ultimately ended up with a Naim 42/Hicap preamp and an Audio Research D70mk2 power amp (which by itself cost 10x what the Tangents cost). With the Audio Research they had a gripping and totally immersive sound that was near impossible to beat. I tried to upgrade them and did home demos of Gale 401, Magneplanar SMG, Linn Kans and Saras and possibly a few others too, but none of them came even close to what the RS4s were doing.

For a while I used them as a guitar speaker, plugging the guitar in to a cassette deck with the record gain set to the max turning it into a clipping fuzzbox. These waveforms and the volumes I put through them did causes some crossover thermal damage...the foam next to the power resistors was melted and scorched, but they never stopped working.

I also found the RS4s to improve enormously when the 6 inch high castor wheeled stands were replaced by some heavy duty spiked HB1 stands at 18 inches. I also rewired the innards with Naim NACA 4 speaker wire which was a modest improvement.

I sadly sold them to close friend in 1985 as I was moving continents. Had I stayed there I may well have been using them to this day. I can only imagine what they would sound like if the crossover was assembled with 2012 audio grade components.