DIY Ripole Subs

[Jazzman53]

Here's an interesting sub developed by German speaker designer Axel Ridtahler-- a compact folded dipole with a cardroid radiation pattern. I built a pair of them for my system using Peerless SLS woofers.

Link to parts list, drawings & build pics: Jazzman's Ripole Subs

 

[scotto541]

That looks really interesting. Nice work. I've not heard of this before, what are the benefits and drawbacks of a design like this?

 

[Jazzman53]

That looks really interesting. Nice work. I've not heard of this before, what are the benefits and drawbacks of a design like this?

I like the Ripole's compact size, the seamless blending with my ESL mains, and especially the clean non-boomy sound.

Before I built the Ripoles I was running a sealed box sub with a Dayton RS 12, which sounded like it only played a single note and boomed like crazy. Of course; there was actually nothing wrong with the sealed box sub-- just that its monopole radiation pattern excited my room's resonance; giving the dreaded 'one-note-boom'. In contrast; the Ripole's cardroid radiation pattern nulls the off axis output, and I believe for that reason, it doesn't excite my room's resonance.

The downside is that, while they have good efficiency at mid bass frequencies; the dipole roll off limits how loud they can play on the bottom end, as it doesn't take a lot of amp power to bottom out the woofers at X-max. That's why I built a pair of them, not just one. Another downside is the chamber resonance, which generates sharp, loud peak in the output centered somewhere between 200-300 Hz.

For DIY'ers, it would take some smarts and a bit of trial and error to design a notch filter to tame the Ripoles characteristic chamber resonance. My website lists components and values for a generic passive notch filter which would get you in the ballpark, but it would still take measurement capability and trial and error to fine tune a notch filter. Passive filters aren't my forte so I took the easy way out and just set the crossover below the chamber resonance using a DSP crossover and steep filter slope, and then tuned it by ear with parametric EQ's until is sounded right.

I've grown to love the sound of my Ripoles but I make it a point never to recommend them to others because not everyone likes dipole bass-- which is clean and musical but doesn't pump out chest thumping bass like monopole subs do, and they aren't very efficient either. There was one guy on the DIY Forum who took every opportunity to bad mouth Ripoles, even though many others there liked them. There doesn't seem to be any middle ground opinions.

I have very clean transmission line bass in my hybrid ESL mains and I didn't want the Ripoles stepping on them, so I chose to cross in the Ripoles at a very low 60Hz using a 48db/octave digital filter and apply a 6db/octave shelving EQ to offset the dipole roll off. Most music doesn't have a lot of content below 60Hz anyway so I seldom actually hear the Ripoles playing. But if I switch off their amplifier; the foundation of the music disappears and the Ripoles' absence is then quite apparent.

And if I play a tune with profoundly low bass content, like Bela Fleck's "Flight of the Cosmic Hippo"-- then I go WOW! --that's LOW and CLEAN.

 

[somebodyelse]

This design is very close to the Linkwitz Woofer 3 which has analysis for that Peerless driver. You need to refer back to other pages for discussion of the driver arrangement and more general spaced dipole models including the notch filter.

 

[nm4711]

That looks really interesting. Nice work. I've not heard of this before, what are the benefits and drawbacks of a design like this?

If I remember right, the Ripoles advantages vs a standard W dipole woofer (@somebodyelse mentioned) are the following:
- compact size
- better frequency extension at the low end without equalizing

The advantage of the standard W dipole is lower distortion.

I would prefer the W dipole because of its lower distortion and because I do equalize my speakers with a DSP anyways.

Greetings Niklas

 

[andrew]

I'm considering a Ripole sub as a compact solution for a near-field sub (located right behind the listening position just below head height). How low do these subs go? Are there any (near-field) measurements?

 

[Peas]

I'm considering a Ripole sub as a compact solution for a near-field sub (located right behind the listening position just below head height). How low do these subs go? Are there any (near-field) measurements?

Actually, they do go quite low as resonance is lowered. But depending on the individual design and tuning, they might need some help such as a bass boost at the lower end.

Here is a more simple design, something in-between a ripole and one half of a Linkwitz W-dipole using two 8" drivers:

https://www.diy-hifi-forum.eu/forum...akustik_schulz&p=280674&viewfull=1#post280674

Measurement was made without the passive notch filter. A DSP might be used instead.

In the nearfield, that might be sufficient. But you need to keep some distance from any wall.

Placing it under a table is a good option.

I have to say that Jazzman's report was one of the prime mover to me to build my own ripole subs. I tried 10" and 12" and stacking is a good option when it comes to home theater use.

The sound is not boomy, right, so no earthquake can be expected if it isn't in the soundtrack. Sometimes, there are earthquakes and then they are audible. But often, people mix up room modes with earthquake effects. A ripole excites less room modes, hence less peaks but moreover less dips. A peak can be flattenend by a DSP whereas dips can't. So that's basically the secret behind all these designs that are very similar.

I like the ripole sound when it comes to gun shots or any other percussive effect in action movies. It is a very tactile yet sometimes shocking sound. When John Wick gets beaten with a metal rod by intruders, not only the faint-at-heart are scared.

Having said that, ripoles are perfect for instruments such as drums and bass guitars, electronic kickbass etc.

The inventor, Axel Ridtahler, is quite helpful when it comes to design DIY ripoles. He charges a small fee, recommends drivers etc.

Here are radiation patterns using the same driver in different enclosures / designs: https://www.lautsprechershop.de/pdf/ripol/ridtahler.pdf

 

[D!sco]

Total thread Necro, don't care, this has good content.

So you're telling me I can have--

1: Small subwoofer
2: Deeper bass
3: Less room interference
4: Reverb cancellation
5: A steady cabinet

And why haven't I seen this before? I'm almost ready to dive in, but I'm wondering why there aren't commercial examples of it or more DIY examples. I checked out Jazzman's sub. In fact, I couldn't stop finding Jazzman's sub when I looked for how to build one. It kinda got in the way of digging deeper. Do I have to learn German or something? The 1/4 SD/pair front slot to 1/2 SD/woofer rear slot is easy enough to calculate. In fact, the whole range of Peerless SLS subwoofers works in roughly the same layout, scaled for size. But this is way harder to find info on than any other bass box. Educated guesses aren't worth investing in. I'd be a fool to ask about WinISD on this project, probably.
I really like the idea of building a series of 8's, like a slot loaded open baffle doubling as a stand. In fact, the ripole 8" works out to approximately 300mm width depending on the ply used, perfect width. (110mm*2, plus the 1/4 SD of 55). My problem is I can't read any more of the T/S into how it will work. I just kinda have to hope it would.

 

[Jazzman53]

Yeah I had the same problem after I became aware of some guys on the DIY Audio Forum building Ripoles.
The two people who seem most knowledgeable about them are "Rudolf" and "Calvin" at DIY Audio Forum.
I had no clue how to model mine so I just used Rudolf's guidelines and I'm pleased with the results.

Patent infringement may be the reason we don't see more commercial companies selling Ripoles.
Modal Akustik sells this Ripole sub under license from the patent holder, Axel Ridthaler:

Why the MusikBass plays so precise

The MusikBass was developed for experienced music lovers, who value a precise and deep bass and those, who suffer from room modes/resonances. The MusikBass can also support electrostatic/magnetostatic speakers as well as other speakers that have a tight and precise bass, where common subwoofers...

www.modalakustik.de

 

[tinnitus]

The Patent expired in 2014.

 

[Draki]

Some general info about the RiPol:

Lautsprechershop Daniel Gattig GmbH: Loudspeakers - Newsletter

 

[Jazzman53]

BTW; one of my audio buddies now owns the Ripoles shown in my first post, and I've built myself an even nicer pair. They blend very well with my latest homebuilt ESLs:

 

[D!sco]

I'd feel a lot better about guesstimating if I already had a miniDSP, but honestly it feels like a prerequisite to building a subwoofer these days.
And thanks for emailing me those CAD drawings the other day @Jazzman53. Got me off on the right foot. Would you say, in your experience, there's a maximum rear opening size? In your example it states to go somewhere between "1/2 and 1 Driver SD". I was thinking about flaring it, hopefully deflecting the rearwave off in a slightly oblique direction. This could also slim the front baffle. Not sure what that effect would have yet. Kinda what's driving me nuts about this build and also what's driving me to figure it out.
I had the chance to use my friend's SVS SB3000 Micro recently and the control it had in a slightly less sophisticated frame was awe inspiring. Seeing your design so shortly after I couldn't help but draw comparison.

 

[MinMan]

I always liked the dipole woofer-1 design by a certain Sigfried Linkwitz:

Dipole Woofer

The woofers benefit from even order cancellation of distortion when wired in parallel: