[Jazzman53]

After pondering which Circle would be appropriate for my Ripol sub build, I concluded the design is dipolar and more akin to an OB that folds around the woofers, than a box speaker, so the OB Circle seems to be the best fit.   

A Ridtahler dipole (i.e. Ripole) isn't a true dipole though, because its radiation pattern isn't a figure-8 but a cardioid.

My latest Ripol subs are similar to my previous builds except more compact-- I’ve reduced their height and depth by 1/2”  and their width by 1/8".   The woofers are the same 12” Peerless SLS’s.  I'm anxious to hear them and I really like the compact size. 
 
I think the smaller center chamber should actually extend the low-end response slightly, and also expand the frontal lobe of the cardioid radiation pattern, relative to the rearward lobe.  This will be at the expense of slightly reduced efficiency but I've got amp power to burn so I’ll just feed them a bit more.   
 
The cabs are 3/4 red oak plywood with oak edge members inserted and rounded over, which looks much better than exposed plywood edges but is a LOT MORE work.   The center section is solid brown oak, indexed to the cabs with oak dowel pins.  The cabs and center section are held together with all-thread rods and cap nuts. 
 
The subs are almost finished; ready for stain and paint.   More to come but for now; enjoy the pics. 
 
Below:  Rabbit cut plywood cab pieces self-locate for gluing.



Below: Cab glued and clamped.



Below: Cab with edges notched on the table saw to accept edge moldings. 



Below: Red oak edge members held in place with painter’s tape while the glue sets.



Below: Cab with edge moldings glued in.



Below: Three-piece sub assembly (cabs and center section).



Below:  Rear view of assembled cabs with edges rounded to 3/8” radius on a router table.


Below:  Front view, both subs ready for stain & satin clear coat.

[aldcoll]

Another of your epic builds. Is your day job a engineer or like backround?

Alan

[Jazzman53]

Another of your epic builds. Is your day job a engineer or like backround?

Alan

I'm retired from Gulfstream Aerospace where I worked as a manufacturing engineer for many years. I was an aircraft mechanic before that, but my first profession was auto-body repair. 

[Jazzman53]

Update Monday 12/12/22

All pieces were stained yesterday and this morning sprayed with the first coat of clear satin polyurethane.

[Jazzman53]

Update 12/14/22

Waiting for the finish to cure a while before installing the woofers--- I think the new/smaller Ripoles will look very nice

[Jazzman53]

Update Thursday 12/15/22:

My new Ripole subs are finally finished and I've been playing some very demanding bass tracks this evening...from Malia & Boris' album Convergence to Bela Fleck's Flight of the Cosmic Hippo-- and they sound ridiculously good. 

As with every Ripole I've heard; I can't localize them in space-- their notes arise from nowhere and recede back to nowhere.  And it's astounding that dipole subs this small can play this low, and their tonal quality is tight and clean and beautiful !
 
Very happy !

BTW; I have a dimensioned CAD drawings and parts list if anyone wants it-- no charge.. just PM an email address.







They match up perfectly with my hybrid electrostats:

[jandrews]

Very impressive and intriguing project.
Curious...Where does the cardioid pattern eminent from? From the slot outwards with the null part of the pattern in the back of the sub?
thanks
JS

[Jazzman53]

Very impressive and intriguing project.
Curious...Where does the cardioid pattern eminent from? From the slot outwards with the null part of the pattern in the back of the sub?
thanks
JS

The forward/single lobe of the cardioid is projected from the front chamber opening and the smaller, rearward lobes are projected from the two rear chamber openings.  And a cardioid has a similar axis null as with a dipole.     

[Early B.]

This is awesome!!! 

You've probably received this question a hundred times already, but how does the sound of your ripoles compare to dual OB servo subs? Can you use your ripole design with servo woofers?   

[Jazzman53]

This is awesome!!! 

You've probably received this question a hundred times already, but how does the sound of your ripoles compare to dual OB servo subs? Can you use your ripole design with servo woofers?   

Actually, I've never been asked that question and I don't really have a good answer because I've never heard a servo sub and I know exactly nothing about them.  The term "servo" leads me imagine some sensor loop which compares the cone's movement to the input signal and generates an error-correcting feedback to the driving amplifier (?).  I figure a servo woofer could be used in a Ripole even though the woofer would behave differently in a Ripole.  Just speculating....

[artur9]

Update Thursday 12/15/22:

My new Ripole subs are finally finished and I've been playing some very demanding bass tracks this evening...from Malia & Boris' album Convergence to Bela Fleck's Flight of the Cosmic Hippo-- and they sound ridiculously good.

Beautiful! I'll take 4   What are their dimensions?

Do you use them in stereo bass or room mode correction configuration?

[SteveFord]

Beautiful work as always.
Did you sell those speakers that you built some time back?

[Jazzman53]

Beautiful work as always.
Did you sell those speakers that you built some time back?

Two pristine pairs of my Jazzman MkIII ESL's, completed in the spring of 2021, are sitting in the backroom of my house, unused since they were built and tested except for showing them at the 10-day Carverfest in Sept. 

I haven't been advertising the ESLs but I will part with at least one pair if anyone makes me a decent offer.  I may keep one pair, in case I ever need to do warranty service (replace a panel or power supply) for one of several pairs I've built for friends. 

Last year I built a pair of Ripoles for a friend in NC and I liked them so much better than my originals that I had to build myself a pair like them.  Same deal here: I intended for a friend in FL to buy the smaller pair I just completed, but I like them so much I don't want to part with them.  So, I will either build yet another pair for my friend in FL or offer him an exceptional deal on the ones I built for myself last year, whichever he prefers. 

If I end up building yet another pair, I will be left with the pristine pair I built for myself last year.  Those I would sell at a really good price.  They can't dirt-cheap though-- the materials alone were north of $700, and then there's my labor....   

[Jazzman53]

FYI:




I recently learned of a German company, Modal Akustik, marketing a Ripol subwoofer in collaboration with the inventor, Axel Ridtahler. And it happens that the Modal Akustik sub and my sub use the same Peerless SLS 12 woofers.

Six Moons Audio reviewed the Modal Akustik sub and said this about it:

"For music-first listeners who prioritize speed, articulation and enunciated clarity, it's the long awaited messiah."
Srajan Ebaen, 6moons.com

I share that sentiment.

The Ripole design principal is not well known or understood-- I'm still struggling with it myself. Modal Akustik explains it as follows:

"The RiPol-principle explained:

The dispersion pattern of regular bass principles is, below a certain frequency, omni-directional. A dipol is physically clearly defined and shows a typical 8-shaped dispersion. The RiPol is a special kind of bass-dipol.

Its special enclosure gives a RiPol not that exact symmetrical dispersion. Because the intensity radiated from the front in relation to the back is different, a RiPol has an asymmetrical dispersion pattern, which leads to a beneficial in-room frequency response. Because the dispersion of a RiPol does not follow the classic 8-shape, a RiPol is not a typical dipol but one of its own kind. Dispersion diagrams show clearly the difference compared to a classical dipol, which justifies its own name, RiPol (as a combination of "dipol" and the last name of its inventor, Axel Ridtahler).

The RiPol-enclosure has a strong effect on its dispersion pattern. It prevents, that the air produced by the chassis movement gets out of the way too quickly, so that the radiation resistance increases. The natural resonance of the drivers is lowered when mounted in a RiPol-enclosure, which improves the reproduction quality of the lower bass region the smaller the enclosure gets (!!). There is however a limit, that is why the dimensions of a RiPol-enclosure have to be iteratively optimized, calculated and simulated. The arrangement of the two drivers opposite of each other in addition realizes a benefitial impulse compensation. At the same time the enclosure has a very small footprint.

A RiPol disperses low frequencies in certain directions, to the front and ,with different intensity and 180° revered phase, to the back. This attribute reduces harmful standing waves in the room. These are energy-retention effects within a room, also called room modes. In a listening room standing waves can cause the impression of inertial bass energy that does not fade away. Bass-heavy speakers float the room with bass energy and leave the impression of a slow or sluggish bass. A RiPol, through its rear chambers, produces "antimatter" at low frequencies, that prevents this effect to emerge. A bass impulse is created and, through its counter-wave that comes from the back, the continuance of the standing wave is prevented. As a result the signal is not blurred by its own overlay. These attributes make the RiPol one of the most musical bass-principles on the market.

And there is another effect of note: Because of the directed bass dispersion, to the left an the right side of a RiPol there is no deep bass. These areas are a good spot for placing sensitive components like turntables, amplifier, CD-players etc. Placed next to a RiPol these electronics are not disturbed by deep bass and can do their work without interference!"

[artur9]

Your builds are better looking, Jazzman53.

Are they the same size as the ModelAkustik ones?

[Jazzman53]

Your builds are better looking, Jazzman53.

Are they the same size as the ModelAkustik ones?

Thanks, I've built several pairs and I'm getting better at it.  For example; I tried to book match the front L/R & top L/R panels to the extend that's possible with plywood, and orient their grain directions at +/- 30 degrees.  This looks very nice so I will repeat that on any future builds. 

I don't know the dimensions of the Modal Akustik sub and I didn't attempt to model mine after it, so it's improbable that their respective dimensions would match.

[dayneger]

This is awesome!!! 

You've probably received this question a hundred times already, but how does the sound of your ripoles compare to dual OB servo subs? Can you use your ripole design with servo woofers?   

I'd be very interested to hear whether anyone has tried a ripole servo sub as well!  I'm currently playing with a design that leverages the GR Research/Rhythmik Audio components in a ripole-similar layout... basically trying to create a slightly smaller speaker that's still OB top to bottom and with serious bass output.

[77SunsetStrip]

I built Ripole Sub after finding information on your first build.  Had a couple Infinity 10" sub drivers looking for a home.  Built around those using the guidelines for front and rear opening size.  Except, did not cut a hole for the magnet structure planning a piano black finish all around.  Within minutes of listening heard deep, clean bass like never before.  After a few months, installed Underhung drivers resulting in stronger bass down to 30Hz. 

If I did another build, how would the front and rear opening sizes impact response?  Does damping material make a difference?  Thanks.