Need advice on adding subs


I’m looking for advice on adding subs to my system.

I listen primarily to small combo jazz and classical but I’m disappointed by the classical symphonic reproduction. I can only enjoy symphonic music on my headphones. Perhaps, I could improve symphonic on my main system by adding subs.

I don’t listen at high volume nor am I a bass fanatic. I just want the better sound. This is strictly 2 channel system. I have no interest in HT. I live in an apartment.

My system:

Balanced Power Technology BP-1 Conditioner
Toshiba lap top with JRiver feeding via crossover Ethernet to
Sonore Rendu
Wyred4Sound Dac-2
Warpspeed Optical Attenuator
First Watt J2 Output power 8 ohms30 watts 4 ohms15 watts

Reference DeCapo MM 2-way Monitors

The speakers are a simple 1st order high pass passive 3kHz x-over to the tweeter. I believe the woofer is designed to rolloff naturally at both ends of its band width.

I’m open to any ideas. Lets say up to $2000 budget.


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If you are going used, a pair of Vandy 2WQs would be a bit under your budget.  They are fast, tight and would match well with your speakers since they have a first order crossover as well.  When I had a pair, I set them up just like marktomars.  Dial them back so that you really can't tell that they are on, except when you turn them off.  
There is a good thread currently running elsewhere on the site, under the simple title "Subwoofers" (I think). Duke of AudioKinesis and BDP24, among others, have made some valuable contributions, and it is worth reading. Here’s the link: https://forum.audiogon.com/discussions/subwoofer?highlight=subwoofers

It's a long thread, but worth the time to read through- some thoughtful stuff that I benefitted from. 
I'm not in love with the combo of deCapo and subwoofers.  

The deCapo is beautifully balanced as a stand-alone.  The presence thru treble is gently rolled off to balance the modest bass energy.  As a stand-alone monitor, it's really, really good and IMO one of the best values out there (which is why I bought mine).  When I added a subwoofer (for pretty much the same reasons stated in the OP), I loved the extra weight on the bottom end, but the sound as a whole went dull.  I tweaked it for a long time, but eventually moved on.

I think I'm one of the bigger subwoofer fans on this board and I'm surely one of the bigger deCapo fans, but the combo didn't work for me.  YMMV.
There is no "absolute set it and forget it" answer to subwoofer sound as there is a huge disparity of bass level in music.  I don't like digital room correction devices as they appear to be somebody else's ideas coming into my hifi zone (and my experience as a professional live sound mixer makes my tone ego enormous), so I simply turn the subs (2 RELs) up or down a little here and there…this is easy and works well for me and the room furnishings provide all the "treatment" necessary in my particular listening space.

$2000 will just cover the cost of the most unique, transparent, unboomy sub of which I am aware: The GR Research/Rythmik Audio OB/Dipole Sub. The catch is that it is not a ready-to-play, factory-finished product. But it's pretty easy to do, if one is sufficiently motivated.

1- You buy the DIY kit from GR Research or Rythmik Audio, the co-designers of the sub. It contains four 12" woofers (a pair for each of two subs) optimized for Open Baffle use by Danny Richie of GR, and a pair of Rythmik's dedicated plate amps (one for each sub, of course) featuring Servo-Feedback control of the woofers, along with a shelving circuit to compensate for the acoustic roll-off endemic to dipole designs. The Rythmik amp also features outstanding controls including adjustable cross-overs (frequencies and slopes), three levels of damping, 1-band PEQ, and, most importantly, a continuously-variable phase control (absolutely mandatory for integrating a sub with speakers. Do NOT buy a sub without it!). The kit is about $1500 including shipping.

2- You buy a pair of Open Baffle H-Frame flat packs from a woodworker who offers them on the GR Research AudioCircle Forum for around $500. Don't worry---I bought from him, he's very honest and trustworthy. The frames are sent unassembled, but are as easy to build as an Ikea bookcase (well, almost). Made of 1.5" MDF (!), they are a truly excellent design, and very non-resonant (unlike the W-frame design of Linkwitz). You then simply paint or veneer the frames to suit your taste and style. See the thread about them on the Forum for details. If this sounds like more than you want to deal with, you could have a cabinet shop assemble and finish them for you.

There was an OB/Dipole sub offered by Gradient in the 80's, for use with the Quad 63 ESL's (reviewed by REG in TAS). This is similar in concept, but much more advanced in execution. Higher quality drivers, with Direct Servo-Feedback (patented by Brian Ding of Rythmik) control of their motion. State of The Art in subwoofers!