Pair of Rel S510’s or Carbon Special’s?

@nyev I have a pair of REL T/9x's paired with Harbeth 30.2's and I'm really happy, they just add a little bottom end energy. My comments are set up related only...

- Placement close to each main speaker is desirable. They are acting as extended bass drivers not surround-sound sub-woofers.

-Based on the above, phase is irrelevant. Set to 0.

-The high-level Speakon cable connection is recommended to reduce support calls because EVERY amp can support this method. The way to go is a line level rca stereo sub-out but obviously not all amps have this feature. This was a significant consideration when I recently upgraded my amp, I went with Raven Audio. All you need is a good quality pair of stereo RCA interconnects that come as a separated pair (E.g. Raven's). Don't waste money on overpriced subwoofer cables.

-If you have to use the supplied Speakon cables, trim them. If you still end up with a hum after floating the ground (or not), feel free to private message me for an easy fix.     

Thanks @macg19. My amp does in fact offer RCA connections specifically for subwoofers. However Rel claims that the high level inputs are better because then the subs are in perfect sync with your speakers, as they are getting the same signal…. Also, I’d think the low level RCA run would not be good for a low-level signal vs a high level speaker signal? My perspective is 100% influenced by marketing and things that sales guys have told me for many years in HiFi shops. Sadly I don’t think I can recall any good advice from a well-meaning but misguided sales person.  Many years ago a salesman told me that the high level Rel connection offloads your main speakers thereby improving performance, while automatically adjusting to a seamless crossover point for utterly perfect integration. I always remembered how passionately he was telling me this, which I always thought was BS!

@nyev My pleasure. Good news on your RCA sub-outs. The high-level input driven from the speaker binding posts passes through a resistor that essentially turns it into a low-level input anyway. Note that gain control on the REL is the same for both high-level (Speakon) and low level (RCA) inputs. (There is a dedicated RCA input with it’s own gain control but that is only for low-level .1 surround sound). There are zero issues with using the RCA low-level inputs unless your RELs are really far from the amp.

I a/b tested high and low level when I got the new amp and there is no question that in my system the RCA/low level sounded better.

Miller Carbon would buy 6 more subs.

This has been a very helpful exchange.  I have resisted subs for for more than 40 years (since they started?) and am still doing so, but every now and then I am tempted in to have another look, as here.

@nyev , all the little details about power cords, which sub model, high vs. low level connections, phase control, etc. are all secondary to proper subwoofer positioning.  If your subwoofer position is wrong, then the other stuff won't even matter.

A simple test would involve moving your current loudspeakers to the proposed subwoofer positions and run a series of bass tones to evaluate.