Anybody here try the OB from the '96 "Stereo Sound" article?

[Racket Scientist]

This design is described here:
Open Baffle
along with related links. Looks to me like it might be a good design with a bit more bracing and moving the speaker off to the side a bit. A variation of this will probably be my new OB design for my Tang Band 1808s unless somebody here talks me out of it.

[CLS]

A lot, already.

And I think there are many other better designs.

[Racket Scientist]

Care to share which you think would be best to consider for a single 8" full ranger to go down to about 120 Hz using no crossover?

[TerryO]

I have a pair of JE Labs OBs and I think they're just fine. I would cut a larger diameter hole to allow replaceable driver baffles and allow for different placement (and drivers if you wish). I'd also recommend a full width connecting panel to run across the top from one upright brace to the other. It would make them a bit more solid and you'll pick up a bit of bass extension as well.

Best Regards,
TerryO

[djn]

I would also model the OB in the EDGE program to see what more offset would offer as far as flattened response.

A friend of ours has these speakers and built them when the article came out. They sound very nice....but....not as good as they could be with a better baffle design.

[TerryO]

Originally Posted by djn

I would also model the OB in the EDGE program to see what more offset would offer as far as flattened response.

A friend of ours has these speakers and built them when the article came out. They sound very nice....but....not as good as they could be with a better baffle design.

I'll second Dennis on the use of Edge. I've used it myself, but it is possible that, as happened to me, I kept getting an exact center location for the driver. Knowing that this couldn't be, I talked to Dan Wiggins and his final conclusion was that "sometimes" the center location is the best. Who would have thought!

Best Regards,
TerryO

[CLS]

Originally Posted by djn

I would also model the OB in the EDGE program to see what more offset would offer as far as flattened response.
...

Did that and got pretty good results - myself and a friend once made baffles of the same size, but with different driver positions. Mine was close to the side, while his was close to the top. Both ours were very offset - far from the center, and both sounded smooth.

Wide range OB design is full of dilemmas. Size, flatness of response, bass extension, directivity... It's almost impossible to harmonize them. You have to have priorities sorted first.

The original design of that in the 1st post, IIRC, is for fullrage (even without EQ?). That is a pretty big (wide) baffle, and with the very low position of driver. These factors, I believe, are aiming for compensating bass. However, I can imagine it's overall performace in midrage purity, natural sound stage and imaging won't be very good...

From the most picky view of OB obsession, the side wings might cause some resonances (plus the equal distance both side). Also, the driver is already very close to the largest 'wing' - the floor. Early and severe reflections are inevitable.

Tradeoffs, tradeoffs....

I think, re-target the bass response one octave higher (about 160Hz), and add some 'tolerance' to EQ, then the possibilities will open up immediately, and vastly. And overall it might bring many other benefits, too.

[TerryO]

Originally Posted by CLS

Wide range OB design is full of dilemmas. Size, flatness of response, bass extension, directivity... It's almost impossible to harmonize them. You have to have priorities sorted first.

The original design of that in the 1st post, IIRC, is for fullrage (even without EQ?). That is a pretty big (wide) baffle, and with the very low position of driver. These factors, I believe, are aiming for compensating bass. However, I can imagine it's overall performace in midrage purity, natural sound stage and imaging won't be very good...

From the most picky view of OB obsession, the side wings might cause some resonances (plus the equal distance both side). Also, the driver is already very close to the largest 'wing' - the floor. Early and severe reflections are inevitable.

I'm not sure that the drawbacks are as problematic as you've described. In the first statement listed above, I'm not sure what you mean by harmonize, if this is actually a specific reference to the JE Labs design or an overview of OB's in general.

I'd say, in light of your second and third statement, that I would maintain that midrange purity, natural soundstage and imaging are not automatically being sacrificed at all, although Imaging may suffer a bit. The floor is an infinite dimension and will lower the dipolar frequency step a fair amount as well. The driver's proximity to the floor improves the overall bass in that the time interval (and cancellation modes) of the floor reflection is reduced to the point that it's not easily discernable at all.

As far as the side wings I believe that the bracing that I've mention in my prior post largely eliminates any resonance, at least mechanically. Driver offset may indeed prove to be beneficial and, as I've mentioned, the option of the use of replaceable baffles can allow a fair amount of latitude in positioning.

To the OP: I'd go for it, you will have functional speakers and can then use them as a reference during further experiments.

Best Regards,
TerryO

[djn]

"To the OP: I'd go for it, you will have functional speakers and can then use them as a reference during further experiments."

I agree. Also, with OB, you can get corrigated cardboard and make all the mockups you want. You will lose some low end due to flex in the CB baffle, but it is cheap and you can test the different locations on the baffles.

[CLS]

'Harmonize' might not be a good wording for my intention. My main point is all the dilemmas.

To maintain good bass, the baffle should be big. Then it's automatically weakened in construction and the energy store is increased. And the directivity suffers - off axis response in higher range does not maintain dipole (messy lobings all over instead). The bigger the baffle, the lower it happens. These factors would degrade the overall mid-high performance.

Wings strengthen it of course. However it also adds resonance acoustically. Some very picky OB lovers claim they don't like any wings, and I tend to agree. I can hear wings down to 10-15cm in width coloring the lower mid to midbass. Similar effect is commonly found on open back cabinets for guitar amps.

120Hz target is not that hard to get (sorry I misread that in the previous post), if some EQ is acceptable. Since there'd be helper woofers, so I tend to make such baffle smaller to get better mid-high response. Or, you might even consider just hanging it nakedly. For a 8", you'll get 300-some with some help of EQ.