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]

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]

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]

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.

 

[Racket Scientist]

I'm thinking of trying a speaker location about 15" up from the floor, and offset to one side about an inch (so pretty close to a center location). I also plan to add some bracing to decrease flexing of the baffle, as well as considering cutting "windows" in the side baffles. Finally, I'm thinking of changing the 8" piece that goes on top to a narrower piece that goes all the way across. Any advice on those ideas?

 

[Andrewbee]

Racket, Stop theorizing and build it as shown. Build it in such a way that the braces, wings etc are just screwed on and not glued. This way you can try your ideas and listen for YOURSELF. Make it bigger, smaller, different shapes and you be the judge.

Some people are more sensitive to some things than others. I have tried OB as well and I ended up with a B200 above a Rythmik 12" sub in a much narrower baffle, only thing is the sound was more "pure" without the sub but of course the bass suffered and there was some unbalance without the bass as the foundation. So IOW I had to compromise and every system is going to be a compromise in some way or the other.

Get some OSB or other cheap material and just build it and experiment.

You could try putting some sound absorbent material on the back of the baffle during your trials and see if you can hear / prefer the difference and not put the baffles too close to the side or rear boundries, for me at least 6 feet from the rear walls and 2 feet from side.

As you get ideas just try them out, that way you don't have to "think" about if they will work or not. Cut a window in the baffle and prefer the sound without the window? Fill the window in.

 

[Racket Scientist]

Those of you that have actually heard a version of this OB design - a few quick questions:

Have you heard the same driver in a sealed box, and how did it compare in each?

Other than bass extension and taking up lots of physical space, were there other major limitations of the design, or was it competitive with other "very high end" designs?

If you've moved on to another design, what did you move to and why?

I'm pretty much settled on a minimal or no passive crossover or eq, using the TB 1808s, supplemented by large sealed PA woofers below about 100 to 120 Hz fed by a separate amp from an active crossover. Just trying to make a final decision on whether to try a sealed 1.25 cf box or open baffles. I really don't want to redo it once its done, just listen to it for a long time, so I'd like to get it pretty close to great the first time.

 

[CLS]

Ah ~ contradictions.

According to your questions (which represent your thoughts), I think it's not easy to settle down to a 'great' solution in one shot for you (and almost everyone else in this forum I guess).

We diyers are just obsessing in thinking about a 'better' way to this or that. The thought of "This is my final build" just doesn't work. You'll soon do the next, inevitably. We all are. I am. (How I hate that, sometimes.)

Enjoy

 

[2litre]

Racket Scientist,

I tried the JE Labs OB with a pair of FR125S's soon after they came out.
Good sound overall, couldn't take much power though. You can only get so much out of a 4" driver in OB.
After about a month I augmented them with some P.E. RS225-8's at @150Hz.
The RS225-8's made only a slight difference in the bass but really freed up the FR125s's.
At that time I didn't quite understand the QTS requirements for good OB bass.

I liked the sound either way, but as you can see, they required quite a bit of real estate in my small home. My Wife is cool and I could take over the living room for the weekend every month or so.
I broke them down because they were just too big. No sense owning speakers that always reside in the basement.

I agree with both Andrewbee (stop theorizing, start cutting) and CLS (these won't be your only set of DIY speakers).
Free material makes experimenting sooo much easier. Ask some buddies, they just may have some scrap hanging around in the rafters of thier garages.

R/
Jim

 

[Godzilla]

I got this sim for the 1808 on that baffle (36"x31"). Not sure how to account for the wings but it's all part of the experimentation and fun of diy. The sim is not super smooth but i have given up on smooth response charts and only follow the overall trend bc the room contributes so many variables. It's impossible to sim and expect it to be exact. But the overall trend allows you to build something and listen to see if it's about right... and then you tweak. It's a big speaker but if your room can accommodate them along with the woofers you want to connect for bass support you should be able to blend the two around 100hz.

 

[Godzilla]

Another sim with the Pioneer B20 (BOFU) and the Betsy full range driver. I have all three of these drivers to play with.

I haven't even finished my current project (using the 1808) and already want to build something with these 36" x 32" baffles!

If anyone is interested in taking my 21" x 46" baffles they are free to someone who wants to pic them up. I live on Long Island, New York.