Rel sub

Yes, I use a single Rel T/7x with mono blocks. My hybrid mono blocks are balanced (+/- referenced to each other and not to ground), so I connect as shown for “Differential (i.e. Fully Balanced)” in the accompanying Rel booklet: Yellow connects to left + and Red to right +. I connect the Black wire to a screw on the power strip which is earth/ground.

This wiring also works for a pair of balanced PP 2A3 amps I built with no global feedback and floating secondaries. However, to eliminate hum with these amps I also had to connect both secondary commons to earth/ground via the same screw on the power strip.

I can’t say if this wiring works for all mono block amplifiers, but it works for me. You may have to experiment to get to get the lowest noise and functioning connection. The Rel documentation says that not connecting the Black wire may work better for some implementations.

Thanks, I'll check it out.

I'm pretty sure Rel recommends using two sub woofers if at all possible They both eliminate so many room issues especially with a two channel stereo system I have two subs along with my tower speakers that have built-in powered sub woofers

There is a really good series on YouTube called " Subwoofer 101" and it covers all aspects of sub woofer setup and he swears by having two sub woofers 

I may have to go with two. Thanks

Why is a single powered subwoofer getting involved with the mono amplifiers?

I have a single powered sub and simply Connect the rca cable to the back of it.  My sub has volume and crossover settings on the back. It's a b&w asw 2000. 

Newer subs require Wi-Fi access to adjust them which is troubling but it's the modern age I guess.

I use the sub output from the processor I have.  My main speakers when I use my preamp for two channel listening don't use a subwoofer. Not really needed.

@fertguy One sub NEVER works well. You wind up with a disturbing modal pattern in almost any room, bass here, none there. Creating accurate bass below 60 Hz Also requires a lot of acoustic power which requires surface area (big drivers) and long excursions. Mono amps for the main speakers has nothing to do with it. The same situation results with a stereo amp. Read my Building Resonance Free Subwoofer thread below. The fact is you are better off with no subwoofer than a poorly implemented one. Aside from at least two subwoofers you also need a complete two way crossover. The low pass filter most subwoofers come with is inadequate. 1/2 the advantage of using a subwoofer is relieving the main speakers from having to produce low bass resulting in lower distortion levels.  If cost is a factor you can always stage your subwoofer system. Subwoofers done right are the difference between a live performance and just another stereo. 

mijostyn

I'll take your word for it but I can't understand why just one sub could cause this:

Just get a second REL sub, I have monoblocks and researched the issue of a single sub, not good for REL subs or any subs for that matter. My present setup with the two REL subs provides me with most coherent low bass I've yet experienced. This vs. various single subs setups via low level outputs and DSP. Mijostyn is talking about room modes, here-https://www.youtube.com/watch?v=TiIIHztRqCA

@fertguy  Yes two. Aside from the modal/room issues a stereo system has a Left and Right channels and connecting one sub only gets you one channel’s worth. The way sound is mixed….one can guess the rest. 

PS Audio says Red to left amp, yellow to right amp, black to ground. I don't know. Two looks better.

Also, I run only a single signal wire out, hot to positive on amps, ground to chassis. With two signal wires, to both positive and negative binding posts I get excessive output, read about this in owners manual and/or forums. And, I run a set of diy cables to the REL's, I use only Neutrik brand, no fakes, and just enough length of Duelund tin plated copper, far superior to the stock cable in any length. The cabling does affect sound quality of REL subs. I'm next going to experiment with VHAudio AirLock, OCC copper/ solid core wire, this vs the Litz wire in stock and Duelund cables. Some claim solid core more impactful, articulate than Litz.

I meant to say Neutrik CONNECTORS, there are inferior fakes out there.

@fertguy now that you’ve settled on 2 RELs, when you get the wiring sorted (floating the ground or not and only requiring 1 hot lead per channel) I suggest ordering a custom set of Speakon cables from designacable.com in the UK

They use genuine Neutriik connectors, and cost way less than RELs premium cables.

Frank at Signal Cable also makes some but I haven’t tried them.

Btw I was surprised that REL doesn’t use Neutrik on their stock cables

@fertguy I'm using Duelund tin plated copper wire on REL's, I'd take easy bet on these diy cables being superior to the two you mentioned, read some reviews on the Duelund wire for speakers. For DIY cables you don't even have to know how to solder, with the Neutrik you can clamp without solder, bare wire at both ends. You don't have to spend big money if you diy, and diy can be superior to any pre-assembled REL cable out there. Just like the amp, cables affect sound quality of REL's, part of tuning these subs for coherence with main speakers.

Thanks for the info but I'll more than likely just buy good cables.

@fertguy I bought my REL neutrik cables from BlueJeans Cable and they're very good. Far better than the cheap stuff that came with the Carbon Specials. They have options also for configuring the ends so you can get what you need for connecting to the amps..

Analysis Plus makes nice cables for REL subs. That's what I use.  

Thanks for the ideas, I'll check em out...