Yet another DIY Ripol sub project

[Jazzman53]

Hi All,

I'm building a new pair of Ripol subs for a friend. I've built several pairs previously but these will be a bit smaller/more compact. Height and depth are reduced by 1/2” and width reduced by 1/8". The woofers are the same 12” Peerless SLS’s.

Ripol physics seem counter-intuitive at first but the configuration actually lowers the woofers resonant frequency by as much as 10Hz. In this new pair, the smaller center chamber should slightly extend low-end response and perhaps expand the frontward lobe of the cardioid radiation patten, as a result of the higher chamber pressure. This will be at the expense of slightly reduced efficiency but my friend has amp power to burn so... not a problem.

And I think my friend will like the compact size!

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 cabs will be oil stained with a mixture of 1/3 golden oak to 2/3 natural with a bit of powdered turmeric root added to give a yellowish tint. The brown oak center section will be stained with a red oak, for contrast. After staining; two coats of satin polyurethane will be applied, with a #320 sanding step between coats.

More to come but for now; enjoy the build pics.

Below: Rabbit cut plywood cab pieces self-locate for gluing.



Below: Cab glued and clamped.



Below: Cab with edges notched on table saw, to accept the oak edge members.



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



Below: Cab with mitered edge members glued in.



Below: Three-piece assembly (woofer cabs & center section).



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



Below: Frontal view with all woodwork completed / ready for stain & satin clear coat.



Below: When completed the new subs will look something like one of my personal subs shown here:

 

[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 Wednesday 12/14/22

Waiting for the woofers to arrive--- I think the new/smaller Ripoles will look very nice

 

[DasguteOhr]

Looks beautiful , really good choice peerless

 

[Jazzman53]

Looks beautiful , really good choice peerless

I'm quite impressed with the Peerless SLS woofers, which just seem to do everything well. That is; they have a very low FS with good excursion needed for subs, yet they still play cleanly to 1KHz. They also have progressive suspension that prevents them from being damaged when they bottom out at X-max. And an excellent value at their cost point too!

Believe it or not; I use the same SLS woofers for the mid-bass drivers in my hybrid electrostats and they even blend well with the ESL panels!

 

[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

Very happy !

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



Back view:


A good match with my hybrid electrostats:

 

[Ron Resnick]

They look beautiful!

 

[DasguteOhr]

I'm quite impressed with the Peerless SLS woofers, which just seem to do everything well. That is; they have a very low FS with good excursion needed for subs, yet they still play cleanly to 1KHz. They also have progressive suspension that prevents them from being damaged when they bottom out at X-max. And an excellent value at their cost point too!

Believe it or not; I use the same SLS woofers for the mid-bass drivers in my hybrid electrostats and they even blend well with the ESL panels!

Peerless are excellent woofers for ripol have fun with them. Nevertheless, I would recommend you to cut it off at 150hz from there the frequency response becomes very wavy. higher than 200hz, a ripol produces pronounced chamber resonances (housing)

 

[Jazzman53]

I am aware of the Ripole's characteristic chamber resonance, which is rather loud and peaks at around 250Hz in Ripole the size of mine.

Some builders add a passive notch filter to tame the chamber resonance but I prefer to avoid exciting it by crossing mine over at 80Hz using the 48db/octave LR filter in my DBX Driverack Venu 360 DSP crossover. This works quite well.

 

[Salectric]

Beautiful woodworking! Thanks for sharing the build photos.

I have a question about your main woofer setup with the stat panels. Is that woofer open baffle?

 

[Jazzman53]

Yes, but it's perhaps better described as s modified H-baffle, insofar as the ESL's triangular-H base is integral to the baffle.

Here's a video from a few years ago of my Jazzman MkIII ESLs playing with my first/much larger Ripole subs:

 

[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!"

A side note:
Now that I have the new Ripoles, I'm wondering what to do with the pair I built last year (shown below) and no longer need. They are in pristine condition, sound equally fabulous, and are same as the new ones except 1/2" taller and deeper.

Food for thought...

 

[Jazzman53]

I've received requests for an easier-to-build version of my Ripole sub so I've drawn one up that omits the rounded edge members; living the plywood edges exposed. Below is a screenshot of the drawing. If anyone wants the CAD drawing just PM me an email address.

 

[Gooch]

Those are very nice boxes well done

 

[JGlacken]

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!"

A side note:
Now that I have the new Ripoles, I'm wondering what to do with the pair I built last year (shown below) and no longer need. They are in pristine condition, sound equally fabulous, and are same as the new ones except 1/2" taller and deeper.

Food for thought...

 

[JGlacken]

So are you saying you would like to sell your last years pair?

 

[Jazzman53]

Yes, I will sell them at a good price but shipping would likely be quite costly. You can PM me for the price. I can't quote shipping but in the US, the materials cost for a pair of these subs is $868, not including labor.

 

[japan-audio]

I used this ripol I recived from Axel Ridtahler when he started this idea some years ago with my ESL 57. This was my first impression with this great subwoofer. used them also in other combinations as Mini Onken and always a pleasure to get a low end.