REL Carbon Limited SUB - precursor to the REL Carbon Special


BOB’s Review Series - No 48 – REL Acoustics Carbon Limited Subwoofer (Carbon Special review to follow)

Introduction – I usually make a point of only reviewing products that are still in production at the time of writing, but I decided to make an exception with this the REL Carbon Limited Subwoofer. The reason for my change of heart is that although the Carbon Limited was, as the name suggests, a limited edition run of I believe just 200 units it was at the time a test concept by REL that evolved into the Carbon Special. When released the Carbon Limited retailed at £2,799 and was an experiment in wonder at REL who wanted to see if inserting the carbon diver from further up their range into a Series S cabinet would be a worthwhile experiment. I think it surprised REL at just how good it performed and quickly gained a reputation and selling out fast. REL then had their answer to their concept and set about refining it and building it into a new and slightly larger bespoke cabinet but this time the standard down firing ABR driver used in the Carbon Limited was replace by a Carbon ABR giving all-round enhancement.

The Carbon Special is now available at the increased price of £3,799 and I hope to review one soon.

Technology – The Carbon Limited has a 12” carbon fibre main forward-facing driver with a full 4” travel (2” forward and 2” backwards) and is mated with a 12” non-carbon passive down-firing driver taken from their 212/SE subwoofer. To further distinguish the Carbon Limited from other similarly sized REL speakers all the chrome brightwork is finished to an exceptionally highly polished state including the feet, side handles and the top plate REL logo. A wireless Longbow receiver is built into the Carbon Limited but to take advantage of this users would need to purchase separately the corresponding Longbow transmitter. I used the Carbon Limited hard wired to my power amp using RELs standard cable and the high-level connection. The Carbon Limited is driven actively by a 550w built in amplifier, the Carbon Special has a 1,000w amplifier built into the cabinet.

System Components used in this Review:

Pre-Amp: Gryphon Essence Pre

Power Amp: Gryphon Essence Power

Streamer: Innuos Statement

Compact Disc: Shanling SCD-T200 CD Player

Music Streaming: Tidal, Qobuz, Roon

DAC: Gryphon Zena DAC Module fitted inside the Essence Pre

Analogue Sources: Sansui TU-719 Tuner

Speakers: Marten Mingus Quintet

Cables: Jorma Cables throughout

Performance – As usual setting up a sub in a stereo system is different from using one in an AV rig and can be more challenging to get it just right. AV cinema systems can be more forgiving of set up because they are looking for slam and dynamics whereas stereo based systems and looking more for engagement and enhancement. In a stereo system its easy to think you have set the sub up just right then along comes another track and the bass can be overwhelming, so lengthy experimentation is usually required but don’t get fooled into the mantra that subs should be seen and virtually not heard, what’s the point of that. However, as I have noted with other sub reviews don’t turn the crossover dial on the sub too high because it will just compete with your speakers, a mistake that REL tell me many customers make. So, turn the crossover down a bit but then turn the volume up a bit. I settled on 9 clicks for the crossover and 13 for the volume control.

Subs are not as directional as your main speakers and although the Series S cabinets are by far not the largest made by REL the Carbon Limited is still an imposing box and not wanting it to be too much on show I didn’t locate it in a corner (probably the best location for full room loading) nor did I want it on full view sitting between my speakers so I set it up to the side where it wasn’t so visible but still very effective, we all have compromises to make.

And then I just left it in the system for a couple of weeks before making any further setting changes but even then I ended up back at 9 and 13 as noted above but it was worth a final set up check after living with it for a while.

Having not so long ago listened to a pair of RELs T9/x subs in my home system I was wondering what a larger single sub could bring, especially one with a main carbon driver and I wasn’t disappointed. The Carbon Limited is, as you would expect, a fast and dynamic sub which is just what you need in a stereo system where it needs to keep pace with the drivers in your main speakers and where music tends to demand the speed and accuracy in a sub that cinema systems are less demanding of. This happened with all types of music but of course a sub really shows its prowess with the volume turned up to sensible listening levels, sensible meaning not too low that the sub may as well not be there but also not so high you are annoying the neighbours several houses away. Setting up subs in a stereo system demands patience to find what for you is the Goldilocks setting, note I say you and not me because almost certainly my Goldilocks is not your Goldilocks because equipment , room size and music choice are all different!

Conclusion – Subs in stereo systems are often mistakenly used with small standmount speakers as a way of trying to make up for the lack of deep bass that is generally beyond the reach of such speakers and I can understand why this seems attractive, but it’s not generally the right approach. For subs to work effectively they need to be partnered with decent sized floor standing speakers that are already capable of generating good bass but where bass can still be enhanced by working alongside a decent sub that integrates without dominating. I guess many will disagree with this train of thought but please remember that word ‘enhance’ when considering using a sub in a stereo system because there must already be some bass there for the sub to enhance.

That’s what a good sub should do and the REL Carbon Limited is more than capable of enhancing a suitable equipped main speaker system. I guess that’s whey REL tend to call their products integrated sub bass systems.

My review of the REL Carbon Special will follow soon and if the now discontinued Carbon Limited is anything to go by it should be a cracker. I’m already seriously contemplating placing and order for one without even hearing it first.

Bob – Team Reference Audio