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.)


@golfnutz I’ll take a look. That article was just a primer I ran across; it’s not my bible or anything. The testimony I’ve seen here by some experienced folks has convinced me that it’s helpful, and my own measurements have, too. But my sense is that one need not spend a lot to get the benefits of additional subs; assuming the room is in need of them, even inexpensive (but not cheaply made) subs can help with room modes.

I'd note that what you've said is self-verifying. You said, "the DBA is a complete waist of money on extra subs if they're not needed, or do very little in the difference they make."

Of course a DBA is a waste of money if it's not needed or does little. Same thing is true of literally anything. But if it IS needed or does a lot, well, there you go.

There is a lot of hype about DBA but some good discussion, e.g. here:


Google Tom Welti white paper.

Conclusion from his testing:

Four subwoofers are enough to get the best results of any configuration the best results of any configuration tried. Two subwoofers is very nearly tried. Two subwoofers is very nearly as good and has very good low as good and has very good low frequency support as well.


Problem is, some members are advocating 4 or more subs is the only way to go. It just isn’t true, as well as a complete waste of money - let alone telling everyone that corner placement is essential, which also isn’t true.


621 posts

They are tuned to the room through, Putty Pinching. Perfect integration without digital correction.. Pretty cool actually. 50-100 sand bags worked the best. The slot glued to the floor so to speak.. Ceiling will work too. :-)

oldhvymec, this seems an interesting technique which I know nothing about. Is it possible to explain a bit further or provide a reference or a link to this method? 


There are two approaches to passive radiators. One is a standard cone with a suspension added and conventional butyl rubber surrounds. Then there is a lighter mass version. The cone is lighter and so is the suspension. Normally the surround is foam too. There is a reason.

With a light moving mass the key is to add enough fixed weight to match the port frequency's lowest point with the space and active drivers used. Now to go below that point we add non hardening putty, (Mortite putty is the best) to the point of BOOM in the room.

Now comes the tricky part. You remove mass (putty) the size of a peppercorn at a time until the boom goes away. Your single sub unit has been added and blended to the perfect (Q)uality, with your amp, your mains, you cables and your room. NO electrical correction of any kind, digital or analog. Purely mechanical, just like me.

Now correct your room mechanically. Passive materials. You absorb the bass, you let the bass escape, you control the bass with (Q)uality control. Now you can add just slight correction, vs full blown DSP room killing correction.. I hate it.

Direct coupled subs that use active crossovers and (Q)uality control are pretty amazing. Very close to a DBA servo sub system, SQ wise. 

One of my bass system uses 10-20 drivers, there is a lot of cubic inches of cone material, but perfectly controlled and tuned to any gear, cables or room. GRs servo subs and my SAT Bass columns direct coupled. No crossovers.. There is a small set on my Virtual page..

It's my ways, they work very well. I like the VMPS columns. I wish someone would make them again. I need 20 acres, a wearhouse, and a mule..


Apologies for the title, which should have been, "Try a third sub in the back of the room." 1 AM might not be my best time to write titles. 

@pennpencil   Don't let the naysayers detract from what you hear pennpencil.  That's the only thing that matters.  Glad that the third sub has worked out so well for you.