Understanding the REL Line | Sound Insights with John Hunter | REL Acoustics 

Thank you for reaching out. At this time we do not publish efficiency specifications for our subwoofers.

Thank you for reaching out. When you have a chance, please write in to contactus@rel.net and our team will be happy to provide a subwoofer pairing recommendation specific to your system.

Thank you for reaching out. Thanks to their ability to product sub-bass output that is fast and articulate while also being powerful and dynamic, the Carbon Special is an excellent choice for both 2-channel music and home theater systems.

Thank you for reaching out. It is safe to connect to your NAD C268 using the High Level input, though since this is a Class D amplifier it will be important to connect the black wire of the High Level cable to the amplifier's ground thumb screw, and to never connect the black wire to a negative speaker terminal. As long as this is followed there will be no risk of damage to the amplifier or the subwoofer.

@@RELAcoustics Thank you very much for the speedy reply - shows what a wonderful company REL is! 🙂 I am very happy to see there's a way of connecting the T0 to the C268. Apologies for troubling you again, but there's just one other point arising from your reply. My current power amp (XTZ Edge A2-300) is also class D, and I have it connected to the T0 via Hi level using its speaker terminals in the usual way -- i.e. not using a ground thumb screw (which in any case it doesn't have). You seem to be saying (forgive me if I'm mistaken) that it is important to use a ground screw for a class D amp, but as far as I'm aware, there have been no problems using the standard method of Hi Level connection with the A2-300. Have I been doing something wrong in the several years I've owned my T0? And what, if any, might the consequences have been?

@@johncallaghan3097 Thank you for your response. Since your XTZ Edge A2-300 uses a Class D output stage design, we do recommend against connecting the black wire of the High Level cable to any of the negative speaker output terminals on the amplifier. This is because the black wire is exclusively intended for connecting to an electrical ground reference point, while the negative speaker terminals on Class D amps do not reference to ground and instead carry positive voltage during operation. In a worst case scenario, connecting the black wire to a negative terminal on Class D amps can result in damage to the subwoofer's input filter circuit, though if this occurred then you would hear a very loud hum from the subwoofer instead of normal audio output. With this amp, I would recommend connecting the black High Level wire to one of the top panel chassis screws on the amplifier, or to a designated ground screw elsewhere in your system if one is available, such as on your preamp.

@@RELAcoustics Well, blow me down. Never realised that. Looks like I got away with it this past few years! Thanks very much for the advice, which I will belatedly apply. Much appreciated! John 🙂

I thought our exchange was over, but once (just for peace of mind) I connected the black wire of the T0's Hi level to the A2-300 power amp (using a case screw in the corner rather than the left black speaker terminal), things drastically improved. The sound of the system through my DIY Decware Zen Master ZF15M Open Baffle speakers has elevated them to performance in a higher tier. It is completely gobsmacking. If I thought they were, say, a 10 before, they are now a 15. The soundstage is bigger in width, depth and height and the location of instruments and voices more precise, not to mention timbrally richer. To some degree, this applies even when the T0 sub is switched off. Apparently, the incorrect earth connection in and of itself seems to have some influence on the quality of system sound. No idea why, but there you go. I checked the T0 manual and didn't seem to find anything that pointed out the desirability for class D amplifiers to be grounded to the case of the sub rather than to the black speaker terminal. Since these days I suspect class D amps have become more commonly used, I'd speculate that such advice could usefully be emphasised in the manual. Not everyone will know (just as I didn't), that that's what should be done for optimal system sound -- as well as avoiding the possibility of damage to the sub's filter circuit. I had been contemplating a change of power amp to the NAD C268 because I wasn't 100% satisfied with the A2-300. But now I know why, and have shelved the notion, saving myself nearly £800. The A2-300's performance has turned out to be more than adequate for my needs -- it appears to have been constrained by the method of connection of the sub. So once again, thankyou for a small piece of advice that took a few minutes to implement but has transformed my listening experience. 🙂

Thank you for reaching out. All of our current subwoofer models are designed in California, and manufactured in China. In terms of subwoofer pairing options for your Klipsch Heresy speakers, when you have a chance please write in to contactus@rel.net and our team will be happy to assist.

@@RELAcoustics Thanks for your response and honesty.... I just upgraded my integrated, from a Rotel to a Luxman, (need time to save 💰) but I do have my eye on your carbon special sub - very bold standing, ready to deliver all genres with ease and smooth punch, just beautiful looking sub!!!! Something to consider, indeed.