DIY Ripole Subs

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Jazzman53

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I've just finished building a pair of Ripole subs for a friend who liked mine. These are the second pair I've built, and they turned out very nice.

As far as I know; you can't buy them from any manufacturer, but they are gaining popularity on the DIY Audio Forum.

The Ripole design came from a German speaker builder named Axel Ridtahler. Hence; the name "Ripole" is short for a Ridtahler dipole. It's basically a dipole with its baffle folded around a pair of opposing drivers in a push-push configuration.

Ripoles project a cardioid radiation pattern which blends quite well with ESL's, and their off-axis null makes them less prone to exciting the room's resonance modes, compared to conventional subs.

The pair shown below has woofer cases made from 3/4 AA red oak plywood with quarter-round oak moldings along the box edges.

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

Each sub uses a pair of 12" Peerless SLS woofers, wired in parallel and same phase (i.e. a push-push).

The build was a lot of work but they are unique subs 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.

Ripole Front.JPG


Ripole rear.JPG
 
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ttocs

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Very cool! Nicely done!

I experimented with cardioid setup using multiple subs, but it takes up too much room so wasn't good for the amount of space I have. So this design is very interesting.
 

Jazzman53

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Very cool! Nicely done!

I experimented with cardioid setup using multiple subs, but it takes up too much room so wasn't good for the amount of space I have. So this design is very interesting.
They are so compact; the woofer magnets protrude thru the side baffles, lol. These were built for a friend but I have a similar pair (below), and they blend really well with the open baffle woofers in my hybrid ESL's.

image.jpg
 

Jazzman53

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Nice job, I'm sure your friend is very happy.
Yes, my friend is quite happy with the Ripoles; especially since he' using them with a pair my hand-built, symmetrically segmented wire-stator ESL's shown below. The ESLs' woofers are on open baffles, so the system is fully dipolar-- a seamless and amazing combination.

grills off _jpeg.jpg
 
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I've just finished building a pair of Ripole subs for a friend who liked mine. These are the second pair I've built, and they turned out very nice.

As far as I know; you can't buy them from any manufacturer, but they are gaining popularity on the DIY Audio Forum.

The Ripole design came from a German speaker builder named Axel Ridtahler. Hence; the name "Ripole" is short for a Ridtahler dipole. It's basically a dipole with its baffle folded around a pair of opposing drivers in a push-push configuration.

Ripoles project a cardioid radiation pattern which blends quite well with ESL's, and their off-axis null makes them less prone to exciting the room's resonance modes, compared to conventional subs.

The pair shown below has woofer cases made from 3/4 AA red oak plywood with quarter-round oak moldings along the box edges.

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

Each sub uses a pair of 12" Peerless SLS woofers, wired in parallel and same phase (i.e. a push-push).

The build was a lot of work but they are unique subs 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.

View attachment 22107

View attachment 22108
Very interested in your cad drawings. I am building out my audio room, 25' × 17'×10'. I would love to build a pair for my ML ReQuests.
 

Iansr

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Jazzman: very professional build. How do you seal the gap around the protruding magnet ? Silicone?

BTW have you seen the speakers XRK has built on DIYA using SLOB bass section?
 

Don Camillo

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Nice! These were on my plans list for a while, and now with the purchase of CLS higher on the to do list.

But I was also thinking about a true IB (infinite baffle) sub.
And then use 15" or 18" subs... or maybe those in the Ripole.

Have you tried IB too?

How low would you think the Ripoles go...
 

Jazzman53

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Nice! These were on my plans list for a while, and now with the purchase of CLS higher on the to do list.

But I was also thinking about a true IB (infinite baffle) sub.
And then use 15" or 18" subs... or maybe those in the Ripole.

Have you tried IB too?

How low would you think the Ripoles go...
A unique feature of the Ripole push/push alignment is that it actually LOWERS the woofer's resonance frequency by as much as 10Hz. So; subtract 10Hz from the woofers FS and that's the near field low end response. Transitioning into the far field however, the dipole roll-off becomes significant, pushing the low end response upward.

The Ripoles tend to bottom out the woofers at X-max before reaching really high volume but a pair of them are certainly adequate for most listening tastes. And they are very, very clean. I'm gonna say they're wonderful for jazz but not so much for home theater sound effects.
 

Don Camillo

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A unique feature of the Ripole push/push alignment is that it actually LOWERS the woofer's resonance frequency by as much as 10Hz. So; subtract 10Hz from the woofers FS and that's the near field low end response. Transitioning into the far field however, the dipole roll-off becomes significant, pushing the low end response upward.

The Ripoles tend to bottom out the woofers at X-max before reaching really high volume but a pair of them are certainly adequate for most listening tastes. And they are very, very clean. I'm gonna say they're wonderful for jazz but not so much for home theater sound effects.
Ah cool, I didnt know it lowered the FS with 10hz.
But I believe with IB it also plays a lot lower than its original FS.

Yeah thats what I noticed too when I heard open baffle subs at a show. It is extreme clean... also fast and no boxy at all... For me I dont want a box speaker again. Although of course some are very good... But OB sounds more real to me.

With the true Infinite Baffle IB sub I have to cut a whole in my floor... so it can vent into the space under my room...
But its a rental house... So perhaps better start with a Ripole sub... 😁

There are also versions with one driver if I remember correct...
Perhaps one 18" dual vc. would be enough for my room (8x4 meters)...

It would be easier to place it compared to 2 W-frame Ripoles. That would use 4 15" drivers....

What do you think?

Greetings from Holland
 

Brandon Hartwick

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I sent you a message last night, I'd love to get a copy of those drawings if you're sharing them. It looks like an interesting build for sure.
 

Brandon Hartwick

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How do these do close to walls? They kind of look like they should be pulled into the room, I'm just curious.
 

Jazzman53

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How do these do close to walls? They kind of look like they should be pulled into the room, I'm just curious.
Pulled into the room is best but most living spaces (and wives) would add some constraints on placement. They can be placed close to a side wall but they need a couple of feet or more of breathing space behind them. Visualizing a Ripol's radiation pattern might add some insight.

A Ripol has chamber openings on both front and back but it's not a true dipole in that its radiation pattern isn't a symmetric figure-8.

The woofers being push/push into a [smaller] front chamber accelerates the frontal wave front which creates a cardioid pattern with a larger frontal lobe, a smaller /opposite-phase rearward lobe, and off-axis nulls on either side.

A conventional sub located anywhere in the room will excite an ESL's diaphragm and potentially even drive it into a stator. But at least with a Ripol you can mitigate this by placing the ESL in the Ripol's off-axis null. And if you're using a turntable, it's best to locate it in the Ripol's off-axis null as well.

I'm using a pair of Ripoles and my living room has doors on the rear wall and other constraints on placement, but I have the ESL's directly beside the Ripoles and it works fine:

Grill off 2022.jpg
 
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Jazzman53

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Jazzman: very professional build. How do you seal the gap around the protruding magnet ? Silicone?

BTW have you seen the speakers XRK has built on DIYA using SLOB bass section?
The cutout has just enough clearance to add a layer of 1/8" thick x 1/2" wide foam rubber gasket tape to the inside edge and then squeeze the magnet thru. I would not advise using silicone as that would bond the magnet to the cutout and make woofer replacement difficult, if you ever had to.

Really though; with the woofer chamber being fully open on the back, I don't think it would matter much if you didn't seal the gap at all, provided the gap is minimal/not excessive.

One bit of advice though: The inside woofer cutout (the big hole) should have a bit of extra clearance because it's unlikely that, after glue up, the two cutouts will be perfectly concentric.
 

Tosh

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With the true Infinite Baffle IB sub I have to cut a whole in my floor... so it can vent into the space under my room...
But its a rental house... So perhaps better start with a Ripole sub...
Don, another space-saving and clean sealed bass (maybe second to IB) is an isobaric box, and if you buy 4 woofers suitable for a Ripole, those should(??) also suit an isobaric, so you could try both.

Jazzman, another nice project of yours!
What determines how high up in freq those will play?

This reminds me of playing my SL3 (ESL w 10in sealed woofer) with the back covers off (as I was temp powering both HV from same transformer), and while there was no low bass, the bass that was there was so clean being free of the inside-the-box barking (that's why they're called woofers after all) that I left them that way quite a while...
 

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Jazzman53

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Don, another space-saving and clean sealed bass (maybe second to IB) is an isobaric box, and if you buy 4 woofers suitable for a Ripole, those should(??) also suit an isobaric, so you could try both.

Jazzman, another nice project of yours!
What determines how high up in freq those will play?

This reminds me of playing my SL3 (ESL w 10in sealed woofer) with the back covers off (as I was temp powering both HV from same transformer), and while there was no low bass, the bass that was there was so clean being free of the inside-the-box barking (that's why they're called woofers after all) that I left them that way quite a while...
The upper frequency is limited only by the woofers' response. However; the front chamber, like a jug or any other cavity, has a cavity resonance which is excited when the input frequency matches chamber's resonant frequency. In a Ripole the size of mine, the chamber resonance peaks at around 250Hz, and it's rather loud.

With a hybrid ESL, you wouldn't need to play a sub that high up anyway. But if you did, the chamber resonance could be notched out with a passive filter or an active parametric EQ.

My system mates hybrid ESLs' with a pair of Ripole subs, and it's tri-amp'd with a digital crossover bringing the subs in at 80 Hz using a 48db/octave crossover slope (a 24db slope would be sufficient). In this way, the chamber resonance is entirely avoided.
 
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