Ripole Subs

[Jazzman53]

I just finished a pair of Ripole subs, which I think turned out very nice.

The Ripole design was patented by German speaker designer Axel Ridtahler. Conceptually; it's a dipole speaker with its baffle folded around a pair of opposing woofers in push-push configuration. The name "Ripole", is short a "Ridtahler dipole".

Ripoles have a cardioid radiation pattern which tends not to excite the room's resonance modes, and they blend quite well with my dipole ESL speakers.

The woofer cases are 3/4 AA red oak plywood with quarter-round oak moldings inserted along the box edges.

The center section is 7/8" white oak stained a contrasting color and aligned to the cases with dowels. The three-part assembly is bolted together with (4) 1/4-24 all thread rods and button-head cap nuts.

The woofers are 12" Peerless SLS's wired in parallel and in same phase (i.e. push-push). Allowing the woofer magnets to protrude thru the side baffles is a unique feature which makes the design very compact.

Another unique feature: The acoustic impedance of the chambers actually lowers the woofers' [f/s] resonant frequency by about 10Hz; which allows the speaker to play below the woofers' f/s.

The build was a lot of work but they are unique and I really like their compact size and clean, unobtrusive sound.

The bass notes just seem to rise up from nowhere and recede back to nowhere-- completely un-localizable.

I have CAD drawings if anyone is interested.



A perfect match to my hybrid ESL speakers:

Last edited: Tuesday at 9:39 PM

[Steve Lee]

Gorgeous!

Do you have any build pics to share?

[Jazzman53]

Gorgeous!

Do you have any build pics to share?

I neglected to take photos during the build. The photo below is actually from a previous Ripole sub build, but it's very similar to the new ones I just finished. At least it shows the three-piece assembly. In the coming week I will clean up my CAD drawing, add a parts list and post a screen shot of the drawing here.

[Steve Lee]

Excellent, and that ^ helps in understanding the assembly.

I notice that the magnets are exposed to the exterior?

Are they sealed at that exposure point or vented around the magnets?

Very interesting alignment, sir.

Thanks.

[Jazzman53]

Excellent, and that ^ helps in understanding the assembly.

I notice that the magnets are exposed to the exterior?

Are they sealed at that exposure point or vented around the magnets?

Very interesting alignment, sir.

Thanks.

The woofer magnets are not sealed to the baffle sides, and there is only 1/16" clearance. I thought about modding my drawing to make the opening a bit larger, to allow filling the gap with a ring of 1/8" medium density foam gasket tape. I don't think it matters much either way.

[Steve Lee]

OK, here is a thought concerning ventilation of the voice-coil with mechanical concepts:

Place a flapper vent (reed valve) over the exit vent in the pole piece on its exterior (This could be a folded over and taped above piece of painter's tape to act as a flapper valve).

Now, as the speaker diaphragm moves in and out, so does the flapper valve open and close bringing fresh cool air into the enclosure from around the magnet's perimeter and hot voice coil air exhausted thru the vent in the pole piece.

[Wolf]

I'm pretty certain the SLS line do not have vented pole pieces.
Wolf

[Steve Lee]

Oh, Darn! Another great idea dashed against the rocks of reality . . .

[davidB]

Does Ridtahler's design predate Pass's SLOB, or the Visaton Orgue?

[djg]

Beautiful, impressive presentation. Like a magazine photoshoot.

[Jazzman53]

I'm pretty certain the SLS line do not have vented pole pieces.
Wolf

That's right. The SLS is vented thru (8) holes in the cone, located between the spider and dust cap. Three of the vent holes are visible in the photo below:

[Jazzman53]

Does Ridtahler's design predate Pass's SLOB, or the Visaton Orgue?

I don't know when the Pass and Visaton speakers were deigned. Ridtahler's patent was filed on 7/10/1998.

And here's a later article I found: https://www.lautsprechershop.de/hifi/ridtahler_en.htm

[Jazzman53]

I obtained the SLS Peerless woofers for this project from my favorite supplier; Parts Express :-)
They were back ordered for months but I was patient because the SLS woofers are a good value and perfect for a Ripoles.

However; I recently logged on to order more SLS 12's for another project, and I see that Parts Express has now changed the min-buy quantity to 100 !! I called Parts Express customer service and was told that the manufacturer (Tymphany) imposed the 100 min-buy, not Parts Express.

I don't know if Tymphany is phasing out the SLS 12's, which are still shown on their website, but I did find a source in France who had 28 of them in stock, and I bought 6.

The 2x12 SLS Ripoles are the purest sounding subs I've heard for music. Too bad we can't get the SLS woofers in the US anymore.