Could you share some more info about the ripole woofer.
Yes, of course,
Ripoles have the unique characteristic of actually lowering the free air resonance of the woofers by about 10Hz. No other enclosure can do this.
They can be thought of as a folded baffle dipole except the radiation pattern is a cardioid with a pronounced frontal lobe, rather than the classic dipole figure-8. Like a dipole, the off-axis response is nulled, making them less prone [than monopoles] to excite the room resonance.
I would describe the Ripole sound as quality over quantity-- very clean and unobtrusive; seeming to rise up from nowhere and recede back to nowhere. Great for jazz, not so much for home theater effects. I love them!
Mine use Peerless SLS 12 woofers wired in phase for push/push (not push/pull, as in the similar Linkwitz sub).
The Peerless SLS drivers are excellent for Ripoles and fairly inexpensive, although they are no longer sold in the US. I recently purchased several pairs from a company named "TLHP" in France, for about $100 each, including shipping.
The Ripole patent is in German and the math is over my head anyway so I just relied on general guidelines posted on the DIY Audio Forum by a respected Ripole guru there (user name "Rudolf"). They aren't very efficient, so two is better than one, and they need a bit of EQ boost on the bottom end to compensate the dipole roll off, so I apply a 6db/octave boost from 65Hz down.
The general guidelines for enclosure size are:
- Area of the front chamber opening should be 1/3 to 1/4 the combined piston area (s/d) of the two woofers.
- For woofers with >10mm X-max; set the front chamber opening area at 1/3 s/d. For <10mm; use 1/4 s/d.
- Area of rear chamber openings can be 1/2 to 1 s/d.
- The chamber height & depth need not be greater than required to accommodate the woofer diameter.
- The front chamber will have a resonance peak somewhere between 200Hz - 300Hz (higher for smaller enclosures & visa versa).
Hence; it's necessary to either notch out the resonance with a filter or cross the sub in low enough and with a steep
enough slope that the resonance isn't excited. I avoid this resonance by crossing mine in at 80Hz using a
24db/octave filter slope.
Mine are 3/4 red oak plywood with rounded edges (after gluing up the plywood, all edges were notched on a table saw and oak edge members glued in, then rounded over on a router table with a 3/8 round-over bit.
The enclosure is a 3-piece assembly with the center piece located with 1/4 oak dowel pins. The woofers must be installed before mating the 3-piece assembly together. The assembly is held together with four all-thread rods with cap nuts. I built a pair of them for my system. It was a lot of work but they turned out nice.
BTW; I have cad drawings and a parts list for the ones shown below and also for a simpler version with exposed plywood edges. PM me and I will send both drawings in DXF format.
