Try a sub a third in the back

I’ll share something I stumbled upon in the off chance it transforms your listening experience as it did mine. I purchased a rel s/510 while they were on sale to replace a lesser sub. First, the sub is remarkable. I thought it would just add bass extension. I had no idea it would improve the sound stage so much. But now I had 3 subs with absolutely no space in the front of the room to place the third. I planned to sell it. If you like to tinker like me with your system, you probably would have had the same thought I finally did: connect the third sub for the hell of it. In part, the idea was inspired by the long and very good article someone on here linked to about subs: that talks about putting a sub at the back of the room for HT. The lower the frequency, the more non directional the sound. So, having a sub behind me should be okay in a two-speaker setup. The worst that might happen, I thought was that I might shake my house off it’s foundation. But what happened was absolutely unexpected. The sound in the room became amazingly three dimensional. This is not hyperbole. I have a good system and especially with the new Rel sub, there was good width, height, and depth to the sound. But the effect of adding the third sub was to double or triple the depth into the room. I didn’t believe it so I turned the rear sub on and off, repeating the songs. I’ve done this for a week because sometimes new experiences don’t hold up over time—a product of wishful thinking. This one has lasted. I will describe the change this way. Without the rear sub, the vocals were centered, other instruments were placed around the front of the room—some further away than others. Adding the rear sub stretched the centered voice in front of me from 2d to 3D, like someone was in the room, or better, I was in the vocalist’s room. Imagine taking a photo of the singer and stretching it into a 3-dimensional figure in front of you. It’s like that. Although my previous system had good depth before, with the third sub it sounded like I was swimming in the music. there was an exceptional separation of the instruments around and over me not just in front of me. I won’t go on because results will vary. But if you like to tinker and you have a third sub in the house, give it a go. I hope it turns out as holographically for you as it did for me. (Details: I connected the Rel using the line in from my power amp and two RCA outs on my Dac (it also has XLR outs that I use) to connect the other subs.)


I love seeing the excitement people get from adding a second sub. Also surprised though… as DBA is approx. 25 years old.

Seems some still think of it as folklore or a tall tale.

IME if you’ve got a troublesome room from 150Hz & down (like most) going from one to two subs (obviously distributed not co-located) can make a huge improvement.  
If you’re room is a disaster at bass frequencies (mine was) then four subs should  certainly do the trick. My most distant sub was best served 180 out of phase…



I would also like to know how to hook up a 3rd sub.


1. You can split the left or right low level signal out.

2. You can split the low level sub out.

3. You can come off the main speakers or amps speaker terminals with certain plate amps. REL is one.

4. Certain sub plate amps have a RCA/XLR out to daisy chain.

5. Install a 1 in, 4 out, not switched, split and fixed, low level out.

6. Install an active crossover. 2 in 6 out. DCX 2496. Will add everything up to 12 db of gain for any bass contour through a PEQ and or GEQ

7. Wireless

8. Passive. 1 large power amp running 2-4 passive sub enclosures. Debra, or Swarm.

I ran 4 Tallboys on 1 Mcintosh MC2500. They would crumble a house with a single MC2500 power amp. You could fry eggs on that amp, and it just sounded better and better and better. 220/240 vac power supply. It cost 25% more to run it at 120 VAC vs 220 VAC. Heavy piece of $hit. Hated moving that amp (s).

How's that? There is a few way. If you give me a while I can come up with some more.



I use a pair of Whirlwind Split 6 (XLR) out of my DAC. One Split 6 connected to Left Channel, other to Right Channel. I don’t run my Subs in Stereo, instead, I run them in Dual Mono. Out of Split 6 (left channel), one cable to Amp, one cable to Sub on right side of room (5’ out of corner facing opposite wall), one cable to Sub on Left side of room (behind couch) facing opposite wall. Do the same for the Right Channel, connecting the cable to the Right Channel input on both subs and amp.

I tried adding a 3rd sub, and it didn’t make any difference in my measurements (couldn’t hear any difference either).


FWIW, I'm  aware of different ways to do it. I was wondering how OP had done it.


I did go from a Rel Storm III  to two sealed Rythmiks with servo and was a very significant improvement. Learnt to measure the room, identified key issues, treated the (living) room, and have a 4-way active system with advanced DSP. I've ran subs mono and stereo and haven't come to a preference, at least with 2 of them. I was on my way to adding two additional sealed subs, but detoured on dipole speakers (DIY) and now pondering adding 2 sealed vs 2 OB subs, but surely adding a MiniDSP to allow implementing time delays per Toole, and use of Multitude Optimizer. 


Anyway, I was interested in OP's implementation to tie his results to the approach.