From Nelson Pass: Slot Loaded Open Baffle Project

[edlafontaine]

http://www.enjoythemusic.com/diy/0911/slot_loaded_open_baffle_speaker.htm

[SHYNOLA]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Or this http://www.visaton.com/en/bauvorschl...gue/index.html

[DjDisturbed]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Those would be interesting to take a listen to.

[evilskillit]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

I'd wondered when you do that with your woofers how "open baffle" they are still considered. Don't get me wrong it looks like an awesome idea and I'm no open baffle connoisseur but it seems like when you do that its not technically an open baffle anymore, its somewhere between a box and OB with its somewhat resistive properties in the woofer cavity. Anyways, I'm certainly looking forward to trying it at some point.

[diy speaker guy]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

...it seems like when you do that its not technically an open baffle anymore, its somewhere between a box and OB ...

Historically this alignment has been called "ripole" - a good example of this the Visaton speaker in the second post. Even with the smaller chambers providing some loading ripole is still considered OB.

It looks like Pass just changed it up a bit, making the front chamber much much smaller than the back chamber, effectively moving away from OB and into cardiod territory.

[winslow]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

I've seen the term ripole but thought it was a keystroke error in the spelling of dipole since the d and r are close on the keyboard.

I need to learn more about this ripole thing.

[bearberry]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Here are some informative links:

http://www.diyaudio.com/forums/subwoofers/86466-drivers-parameters-ripole-subs.html

http://www.audiocircle.com/index.php?topic=54844.0

http://www.diyaudio.com/forums/subwoofers/50964-ripoles-honey-i-shrunk-dipoles-1-a.html#post568430

The Petit Orgue looks interesting but nobody in N. America seems to carry the drivers.

bearberry

[Paul Ebert]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

It would be cool to try the AMT-3 prototype configuration out with something like 8 of these per side:

http://www.parts-express.com/pe/show...number=299-284

I could envision building something like that with an open-backed mid and a tweeter in the middle section. Be an interesting experiment, if nothing else.

[honfatboy]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

It would be cool to try the AMT-3 prototype configuration out with something like 8 of these per side:

http://www.parts-express.com/pe/show...number=299-284

I could envision building something like that with an open-backed mid and a tweeter in the middle section. Be an interesting experiment, if nothing else.

I absolutely had the same thought; I've been thinking about it all day.

Anybody know why these wouldn't work well?

[Taterworks]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Unfortunately neither Pass Labs nor ESS can build these for sale, because once ESS abandoned the design, somebody else (a German) came along and grabbed the patent for the Ripole.

What Nelson says about velocity, however, grabbed my attention. In a conventional dipole loudspeaker, we're told to use bass drivers with a large radiating surface and lots of displacement, and we can expect a nice figure-eight radiation pattern from the speaker. However, what the ESS and Pass designs do is monkey with the velocity of the air exiting the front of the speaker, relative to the velocity of the air exiting the rear of the speaker. Acoustic impedance is a ratio of acoustic pressure to a term called 'volume velocity', which for a wave traveling in a duct is the product of the particle velocity in a thin sliver taken along the length of the duct, and the cross-sectional area of the duct itself, though this relation also applies in free space for an expanding acoustic wave. If you decrease the cross-sectional area of the exits of the dipole chambers, you increase the acoustic impedance 'seen' by the driver slightly, but you also increase the velocity of the traveling wave at the exit, which actually decreases the acoustic impedance in the direction of the velocity (which is really a vector unit). This causes the radiation pattern to not be the idealized 'figure-eight' of a dipole. Instead, the radiation lobe out the front of the speaker looks more like a focused candle flame, and the radiation lobe at the rear of the speaker is broader and less focused. The result is that the bass is literally being fired at you with greater velocity because of the narrowed forward lobe, but the output will drop off more quickly as you move off-axis.

Apparently the Pass-designed bass unit for the ESS AMT was a real air mover. With twelve 12" drivers between the two speakers, plus the velocity effect of slot-loading, it ought to have been, and I think that in spite of the ESS sales manager's objection, and the physical size of the module, the original Pass bass unit could sell very well today because today's audio consumer is more exposed to alternative technologies like this.

[winslow]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

So this is something similar to what Emerald Physics is doing in their latest speakers?

[rmeinke]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Nelson's OB used 12 - 8 inch woofers actually Rory. So that thing was actually quite reasonable in size. Perfect for a nice little OB mid/monitor atop. I want to build!!!

[rhubarb9999]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

I am seriously considering this as well.

To build just a super woofer, use 8 of these and a sheet of 1/2" MDF. By making it 4 foot tall, you can get an entire cabinet out of a single 4x8 sheet.

Any idea how high a crossover point you could go with something like this?

Perhaps the Grand Orgue with an Econo-wave crossover and horn in the middle (only because I have them).

[dwigle]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Would a high qts or lower qts driver be better in this application?

[rmeinke]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

I think we need a OB expert to clearly explain the benefits compared to, say, an H frame design.

Outside of sound quality (reported by Neilson), I assume the advatages are its more efficient: +9db instead of +6db in front side (probably the same db loss in the back -10 to -15db?!?).

I would also like to know if the baffle can be made smaller in combination with high QTS and high efficiency woofers... like Martin King's H frame passive sub design does. Seems like it would work very similiar... just the front-side loading is different(+3 db gain over H frame). I'd probably make it look like an H frame but the common slot area (the middle of the H) face the listener.

If this is on the right track, the Peerless India 8 inch buyouts appear like they would would well. Would be very efficient so the freq. resp. drop off in the lowest freqeuncies would be compensated for by the high efficiency of the muti-woofer arrangement/wiring. Could make this a passive xover design like Martin's.

OB experts... where are you?!?!