[Jazzman53]

OK, they aren't planars but they are dipoles and I'm using them with planars... 




The speaker building psychosis got the best of me again after becoming intrigued by Ripole subs. I see a Riplole as basically a compact folded-baffle dipole that plays very low (below 20hz) and because it projects a “figure-eight” sound pattern that nulls the output off-axis, it should excite fewer of the room resonances that can give bass the dreaded “one-note boom”. Ripoles are reported to be clean and musical but, being dipoles, they can’t pressurize a room with the kind of chest-thumping bass that’s preferred for HT sound effects. 

I chose the Peerless SLS 12” woofers for their optimal Ripole parameters and nice price.  The Ripole patent by Axel Rithadler is in German and the math is over my head anyway so I just followed some basic guidelines gleaned from posts by some smart guys over at the DIY Forum:

·   Area of front chamber opening should be 1/3 to 1/4 of woofers’ piston area  (SD). For woofers 
        with > 10mm X-max, use 1/3 SD minimum. For woofers with <  10mm X-max, chamber area
        can be 1/4 SD.

·   Area of Rear chamber opening should be 1/2 to 1 SD.

·   Chamber depth need not be greater than necessary to fit the woofer.

·   Expect a chamber resonance of up to 20db to develop between 200hz-300hz, so either test 
        and build a compensating *notch filter or choose a crossover frequency and slope that keeps
        the output below the chamber resonance. 

 *Approximate values of notch filter for 4 ohm subs:
 L serial 3.3 mH, 0.4 Ohm
 Parallel LCR: 365uF, 1mH, 0.28 Ohm

The boxes are 3/4 MDF sheathed with 5mm red oak plywood and edge-trimmed with quarter-round oak molding to match my other living room furnishings.  The box center section pieces are solid white oak planks stained in a contrasting color for effect and indexed to the mating box halves with (4) 1/4 oak dowel pins on each side. The box is assembled with 1/4-20 all-thread rods and cap nuts as shown in the photos.

Sheathing and trimming the boxes is probably more work than most people would want to endure so I’ve attached a drawing and cut list for a simpler box using only 3/4 MDF or plywood.  The woofer cutouts in the baffle boars are cut with a bit of extra clearance to allow the woofer magnets to center themselves in the holes in the outer panel.  The holes in the side panels allow .090" of clearance for the speaker magnets and I used foam speaker gasket tape to seal around the woofer magnets.  Of course, I also have a CAD drawing of the box with the oak sheathing and trim if anyone wants it.  I also have more photos but I guess I reached the limit on this post.
 
The woofers are wired in parallel for 4-ohm load and I’m using a Behringer DCX2496 crossover and TFM-25 amp.  For the initial setup I’m using a 48db L-R slope and experimenting with various X-over frequencies.  Some people prefer to play their subs into the midbass region and others take the view that subs should never actually be heard, only felt.  Certainly the latter view is best for subs that have heavy woofers but the SLS’s are lighter than most so would offer a wider clean-operating band.  I will likely opt for a low crossover point so the subs aren't stepping on the TL woofers in my hybrid stats (which have a gorgeous tone).
             
I prefer to wait until I've had more time to experiment and tweak the setup before I comment too much on the sound of my new Ripoles.  For now I will only say that they are “unobtrusive” and play really, really low.  I confess that I’m a little taken aback by how much they move the diaphragms in my electrostats sitting next to them!
 
Parts List for two Ripole subs with connecting cables:
(4) Peerless SLS 12" woofers (Parts Express)                                      $320
(2) Pair binding posts (Parts Express 091-1245)                                   $18
(1) Sheet 3/4 MDF (Home Depot)                                                      $25
(4) 1/4-20 x 36 all-thread rod (Home Depot)                                       $7
(16) 1/4-20 furniture cap nuts (Home Depot)                                      $16
(8 ) 1/4-20 threaded wood-inserts (Home Depot)                                 $8
(8 ) Speaker spike feet (Parts Express 249-727)                                   $4
(1) 1/4 x 36 oak dowel                                                                    $2
(32) #8 x 1” cap screws (Parts Express 081-425)                                $3
(1) bottle yellow wood glue                                                             $4
(8 ) Banana plugs (Parts Express 091-356)                                          $11
(1) Roll speaker gasket tape (Parts Express 260-542)                           $6
(1) 50ft- 14ga flat-braid copper speaker cable (Rat Shack)                   $25
                                                                           Total               $443
 
Tool List:                                                                                         

skill saw for first cut on MDF sheet
table saw
router with circle jig
3/4 Forstner bit for counterbores               
1/8 & 1/4 drill bits               
clamps for gluing

[sfox50]

What a cool project! I love the look with the oak sheathing. If anyone tries these with Maggies I hope they let us know.

[jk@home]

Excellent job on the sub, and the how-to building info also! 

I have four AE IB15 drivers that I want to use in some sort of open baffle/dipole sub (two of them). Either flat baffle, H frame, or this style, for my MMGs, in a music only system. I will also be using a DCX2496 as EQ/x-over.

What are the driver parameters needed for a ripole? I'm thinking I read something...somewhere (probably at DIY audio) that disqualified my drivers from this design, although I really like the compactness of it.

[SteveFord]

You really could go into business with your handiwork. 
If so, I would like to be your first paying customer, please.

[Jazzman53]

Excellent job on the sub, and the how-to building info also! 

I have four AE IB15 drivers that I want to use in some sort of open baffle/dipole sub (two of them). Either flat baffle, H frame, or this style, for my MMGs, in a music only system. I will also be using a DCX2496 as EQ/x-over.

What are the driver parameters needed for a ripole? I'm thinking I read something...somewhere (probably at DIY audio) that disqualified my drivers from this design, although I really like the compactness of it.

I would go with the following guidelines (click the link and refer to post #26 therein): 
http://www.diyaudio.com/forums/subwoofers/86466-drivers-parameters-ripole-subs-3.html#post1009781

I would add that low moving mass is an advantage.  Also, since woofer excursion is significant in a Ripole and the chambers will magnify any chuffing noises from the driver, you want a woofer with lots of open area in the basket and very good venting around the pole piece.  The SLS woofers are great in all these respects: they are light weight, the cone itself has venting holes below the dust cap, venting under the spider and a progressive suspension to prevent damage from over excursions. 

[Jazzman53]

You really could go into business with your handiwork. 
If so, I would like to be your first paying customer, please.

Thanks but I conclude that I would certainly starve if I had to do this for a living.

[Russell Dawkins]

 I confess that I’m a little taken aback by how much they move the diaphragms in my electrostats sitting next to them!

This got me thinking - a conventional planar dipole sub would have a null off the edges of the plane, wouldn't it? and if the diaphragm of the electrostats were in that null, they wouldn't move much. So, I am wondering if the null of these ripoles is skewed quite far forward due to the fact that the output vent facing forward is just barely over 1/2 the area of the rear vents, which are double (same size but one for each driver). I would think front-back symmetry would be a useful thing and could be achieved, perhaps, by increasing the size of the front vent - or has this already been discussed in the DIY thread?

[Jazzman53]

This got me thinking - a dipole sub would have a null off the edges of the plane, wouldn't it? and if the diaphragm of the electrostats were in that null, they wouldn't move much. So, I am wondering if the null of these ripoles is skewed quire far forward due to the fact that the output vent facing forward is just barely over 1/2 the area of the rear vents, which are double (same size but one for each driver). I would think front-back symmetry would be a useful thing and could be achieved, perhaps, by increasing the size of the front vent - or has this already been discussed in the DIY thread?

Hi Russell,
Your thoughts on a possible imbalance in the front/back symetry makes sense and I think you're likely correct.  From the discussions I've read on the DIY Audio Forum, the logic for making the back chamber larger is that a portion of its volume is taken up by the convex volume of the cone plus  motor structure while the concave volume of the cone adds to the front chamber-- thus, the actual front/back volumes would not differ by much; however, the area of the chamber openings are quite different. 

I purposely designed the Ripoles with easily removable center sections to allow modifying the size of the front chamber if needed.  While I was building them, I even went ahead and built a second pair of center sections (and cut longer all-thread rods) that are 5/16" wider than the center sections shown.  One of my issues is that I'm not a puter geek and I don't really have or know how to use any measuring software..  I suppose I need to get myself qualified to do that if I want get the most out of my speakers.  Now that you mentioned it, I figure that even if the Ripoles front/back outputs were perfectly symetrical, I would still need to move them a few inches forward of their current position to align the stat panels to the lateral centerline of the woofers.   Anyway, that was an astute observation you made there.
Charlie         

[jk@home]

I would go with the following guidelines (click the link and refer to post #26 therein): 
http://www.diyaudio.com/forums/subwoofers/86466-drivers-parameters-ripole-subs-3.html#post1009781

I would add that low moving mass is an advantage.  Also, since woofer excursion is significant in a Ripole and the chambers will magnify any chuffing noises from the driver, you want a woofer with lots of open area in the basket and very good venting around the pole piece.  The SLS woofers are great in all these respects: they are light weight, the cone itself has venting holes below the dust cap, venting under the spider and a progressive suspension to prevent damage from over excursions.

Thanks for the link!

[Jazzman53]

Update:

I've deferred judgment on my new Ripoles until now; mainly because I've had a hard time learning he use the new Behringer DEQ2496 EQ and DCX2496 crossover and in getting a good blend between the subs and mains.  My friend Martin (audiophile buddy from the CarverSite) dropped by with some deep bass tunes and we spent an entire evening tweaking the new EQ and crossover and getting some power into the Ripoles without stepping on the mains.  Finally I can say that these Ripoles are sounding very good and are now playing with authority.  It's incredible how deep these compact Ripoles can play without booming.  Sub bass notes are very clean and now just seem to come from nowhere on the attack and return to nowhere on the decay with practically no room interaction.  This bass has a completely different character than what I'm accustomed to hearing from conventional sealed or ported box subs.  Ripoles are not known for efficiency but they play clean and loud enough for my jazz needs.  I have them setup as pure subs; crossing over at 40hz with a 48db LR slope, +12db gain on the low channel (relative to the mid/high channels) and a 6db/oct low-pass on the PEQ from the crossover point down.   Finally, I'm pleased to report that I LIKE these new Ripole subs.

Jazz