Thread: Ripole Subs

I've just finished building a pair of Ripole subs, which 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 drivers in push-push configuration. The name "Ripole" refers to a Ridtahler dipole.

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

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

The center C-section is cut from 7/8" white oak planks, stained a contrasting color and aligned to the woofer cases with dowels. The three-part assembly bolts together with (4) 1/4-20 all-thread rods and button-head cap nuts.

The opposing 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 is that the acoustic impedance of chambers significantly lowers the woofers' resonant frequency (f/s); allowing the speaker to play about 10Hz lower than the woofers' f/s in free air.

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 a CAD drawing if anyone is interested.

Absolute beautiful. Congratulations. How low do you think your subwoofer can go?

Originally Posted by Adyc

Absolute beautiful. Congratulations. How low do you think your subwoofer can go?

That's a difficult question to answer. I can give you a pretty good estimate, but I haven't measured that directly.

I have my DBX Venu 360 crossover applying a brick wall cutoff at 20Hz. Even so; its mic/RTA shows response dipping below 20Hz-- but that could be the room and the usual nearby 18-wheeler truck traffic, and jets flying over (my house is in the approach path for the Savannah airport).

The Ripole patent contends that it can play 10Hz below the woofers' f/s (31Hz in free air), which would be 21Hz in this case-- and I can certainly feel that when I play a tune with profoundly low bass content, like Bela Fleck's "Flight of the Cosmic Hippo".

A Ripole's output is dipolar (although the lobes are more cordoid than figure-eight), so its off-axis output is effectively nulled, and its energy confined within the lobes, and stronger in the near field, as the dipole phase cancellation would progressively reduce the low end in the far field. That being the case; room size and volume settings would be variables.

I cross the Ripoles in at a very low 65Hz using a 24db/octave filter slope, so as not to excite their chamber resonance, which occurs somewhere north of 200Hz. I don't need to play them higher in my setup because the 12" woofers in my hybrid ESL's are perfectly adequate above 65Hz.

At the frequency I have the Ripoles crossing in; they are completely un-localizable, and I seldom even notice they are playing. But if I shut off their amp; their absence becomes immediately apparent, as the foundation of the music disappears.

Originally Posted by a.wayne

Glad to see you still at it Jazzman .. !

Would you happen to have any measurements, would love to see impedance mag and phase along with FR response ..! !!

Regards

Was still at it-- I think I've had enough of speaker building (too much work for an old guy), and this may be my last project.

About measurements; sorry I have none. Maybe I should get with the times and learn how to use REW?

I actually downloaded the REW program but I couldn't figure out how to feed in the test tones without adding a preamp and using a really convoluted path which would be different than the signal path I use for music.

Specifically; I don't use an analog preamp in my system and I don't have compatible inputs for the test tones, as I stream from a Logitech Transporter directly into a DSP crossover, using the Transporter's internal digital preamp.

Originally Posted by nc42acc

Great woodworking skills!

Thanks Marty... I cover up the mistakes pretty well :-)