From Nelson Pass: Slot Loaded Open Baffle Project

[diy speaker guy]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Nelson's design isn't a ripole since the rearwave is open. Ripoles have a slot for both the front and rearwaves

AFAIK there is not a specific unique name for Nelson's design. As such, I think it's fair to call it a ripole with a very large back slot as a matter of general description, even though the back slot is rather large.. Or you could call it an H (or more accurately, an N) with a very small front slot. It would also be fair to call it a bandpass (especially since all speakers are essentially bandpass devices).

Semantics are not important. While it's true that this isn't the type of ripole you usually see, there is no rule prohibiting the use of unsymmetrical front and back slots (although admittedly, the slots are usually fairly small). The reason I said "Historically these are known as ripole..." was to illuminate the fact that small slotted OB alignments are nothing new, and ripole is as good a name as any for this creation. But of course, feel free to call it whatever you like. (I notice you didn't suggest what you think it should be called.)

[cixelsid]

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.

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.

Nelson's design isn't a ripole since the rearwave is open. Ripoles have a slot for both the front and rearwaves

[dlr]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

btw John... those are nice looking speakers!! I like... wish I had a bigger listening room!!!

IMO you don't need a big room. This picture is from DIY NE last year at my place. It will give you an idea of the size.



dlr

[rmeinke]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

btw John... those are nice looking speakers!! I like... wish I had a bigger listening room!!!

[johnk...]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

How would one calculate the resonance?

I would look around the 1/4 wave frequency based on the depth of the slot.

[greywarden]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Probably with either an Impedance sweep or a huge peak/dip in the FR

[honfatboy]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

The down side is that there will be a cavity resonance in the slot. If you crossover sufficiently low then that will not be a problem. But otherwise it is just a wide baffle dipole. Mine as well nix the cavity resonance and flat mount the woofers. Simpler and cleaner perfromance. If you want to hide the drivers add a grill.

How would one calculate the resonance?

[johnk...]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

The down side is that there will be a cavity resonance in the slot. If you crossover sufficiently low then that will not be a problem. But otherwise it is just a wide baffle dipole. Mine as well nix the cavity resonance and flat mount the woofers. Simpler and cleaner perfromance. If you want to hide the drivers add a grill.

[johnk...]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

The 9dB increase of the front over the rear in the near field is misleading. It is a result that the slot area is 1/3 of the cone area. Same volume velocity front and rear but at the front the "area" is 1/3 so the velocity is 3x. As the front wave radiates out into free space it will spread just as any other source, into full 4Pi space. You should get a hint of this form the applied equalization. It is pretty much typical of dipole eq or gradient woofer eq.

If the front were truly 9dB higher in the free field at low frequency the radiation pattern would pretty much be a monopole at 6dB (3 -1 =2 = 6dB).

[Paul Ebert]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

What is all the fuss? If anyone but NP had presented this it would not even be a topic of discussion.

Well, if you (or SL) had presented it, there would be a discussion. But, then, neither of you would have, I guess. ;)

I like the idea of using a slew of smaller drivers. Of course, they then have to be cheap to make the system at all affordable. I also like the idea of turning the driver(s) sideways - anything to make it less wide (and increase WAF). I can envision 8 of the 10" drivers linked to above, some tweeter, and a pair of the 835004s I have stored away configured thus (sort of - the MTM would not extend down to the third woofer from the top):

WMW
WTW
WMW
W W

resulting in a 1 square foot by 4 foot tall dipole speaker for not much cash. Heck, one might even get away with doing it all passive.

The fact that the loading has no significant benefit (if I'm understanding you correctly) is fine with me. Now, if you said that it was detrimental, well, that would be a different story.

Still seems like a fun experiment to me.

[rmeinke]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Thanks John, I am just trying to find if there are true advantages over a H/U frame. Mainly... does it have a efficiency advantage over the H or U framees?!? The +9db vs. +6 front side?

If not, then its mainly an aesthetic thang it would appear yes? I would be cool with that... the slot loading somewhat hides the drivers...

many thanks!

[johnk...]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

What is all the fuss? If anyone but NP had presented this it would not even be a topic of discussion. Fold both sides back and you have a W frame, or, depending on how it is folded a "side by side ripole". There is nothing here to get excited about.

Last year there was a dual, asymmetric slot loaded woofer presented that was supposed to be a cardioid.

http://musicanddesign.com/dipole_cardioid_woofer.html

There was such a fuss about it I built one and measured it to show it was just a dipole. The same thing applies here. The slot loading will have little affect the volume velocity out of the slot just as a port has little affect for a ported woofer. It may affect the symmetry of the response between front and rear at higher frequency, just as you can see in the tests I made for the "dipole-cardioid woofer". But at low frequency, in the far field, both the dipole-cardioid woofer and this slot loaded device will be dipoles. As you move closer to the front or rear source things change because you are closer to one source or the other and the slot loading also distorted the source strength in the near field.

[greywarden]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

yeah but then you'd end up with something like the Linkwitz Pheonix.

[Face]

Re: From Nelson Pass: Slot Loaded Open Baffle Project

Couldn't you fold the sides back like in the ripole link above?

[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?!?!