Has Rel fallen out of favor with audiophiles?

artemus, for clarification here's some additional info: Rythmik Audio and GR Research have a unique working relationship and marketing arrangement. Brian Ding and Danny Richie are both located in Texas, and pooled their talents to design some of their products.

Brian Ding of Rythmik is the designer (and Patent holder) of his Direct Servo-Feedback circuit, which is included in all versions of his plate amps. He also designed and builds all the Rythmik factory-finished sealed and ported subs, also designing and having built his aluminum-coned woofers (as well as the paper-coned woofers found in his budget subs).

Danny Richie of GR Research is a speaker designer, focusing on drivers and x-overs for open baffle loudspeakers, for the DIY speaker builder. He offers kits only, no finished loudspeakers in cabinets, though he does have a few guys making enclosures for GR Research customers, built to Danny's specs. Danny is responsible for the paper-coned 12" woofer offered in the Rythmik F12G (he prefers the sound of a paper cone, and feels his provides low-level resolution and musical timbre superior to the aluminum version), the non-G version having an aluminum woofer.

Brian and Danny both sell the Rythmik DIY sub kits, while Brian is the marketer for the finished subs. The sub flat pack enclosures offered by both DIY Sound Group and Parts Express are one and the same, PE buying them from DSG, marking them up a little, and reselling them. There is both a 3cu.ft version and a 4cu.ft. one, the larger intended for 18" woofers, but recommended for the Rythmik 15" woofer as well.

The DIY Sound Group flat pack enclosure is an okay design, but could be better. Adding more internal bracing is a real good idea (Jim Salk's enclosures for the Rythmik subs are absolutely incredible!), as is adding a second layer of MDF to the single 3/4" panels, which are barely sufficient. I designed my own 4cu.ft. double-walled sealed enclosure, drawing up the plans and having a flat pack cut by a cabinet maker in my locale. Assembly with wood glue and braces is not too difficult, and the MDF can be veneered or painted in any way one wishes. I chose "Hot Rod Black" by John Deere, intended for their farm tractors. Looks real cool, like a 50's custom car---not glossy, not flat, more of an eggshell type low sheen. No flames, though!

Artemus, there are two reasons some Rythmik customers choose to get a DIY kit version of a sealed or ported sub (ignoring for now the OB/Dipole Sub that Kenny chose, as it is available only as a kit) rather than a factory-finished version.

1- Yep, of course a kit is cheaper than a finished version. The kits come with a driver, plate amp, and acoustic material to stuff the enclosure with---everything but the enclosure. There are detailed diagrams of the suggested enclosure (see No. 2 below), and the user can either make it or have it made by a local cabinet shop. There are also DIY "flat pack" enclosures available from both Parts Express and a Rythmik/GR Research owner who has had 1-1/2" thick (!) MDF panels cut on a CNC machine.

2- The other reason is that the optimum enclosure size for the 15" Rythmik driver is 4cu.ft, but the factory enclosure is only 3cu.ft. Rythmik owner/designer Brian Ding is a rather frugal guy, and wanted to keep the cost to ship reasonable, so decided on the smaller enclosure size. The 4cu.ft allows the DIY Rythmik F15 sub to slightly outperform a factory-finished one, in terms of efficiency/sensitivity and maximum volume.

In addition, speaker designer Jim Salk offers both the Rythmik F12 and F15 subs in his own, custom-made enclosures, finished in beautiful natural wood veneer. They are more expensive, of course, but look really, really good. Jim makes the F15 with a really well-braced 4cu.ft enclosure. Details available on the Salk website.

The Rythmik/GR Research OB/Dipole Sub mentioned above by Kenny and myself is a completely different animal, and a very special, unique design. It’s not for everyone, but is THE sub for planar speakers (ESL, ribbon, magnetic-planar), as well as high-resolution dynamic speakers. Details available on both companies websites (the sub is the result of a collaboration between Brian Ding and GR Research’s Danny Richie), and has been discussed on the AudioCircle GR Research Forum quite a bit.