[Ultralight]

Curious with OB speakers.

What happens if with traditional speaker box, saw 12 inches wide and 10 inches deep, and there's a driver in the front and one in the back, playing out of phase.  What happens to the OB sound?

Why this query?  With a simple jumper cable, one can disconnect the rear speaker and simply play it as a traditional box speaker and if hook up, have the OB sound.  OR with another change, can have a bi-pole where both speakers are in phase.  This gives three alternatives in one box - monopole, dipole, bipole. 

Just curious if this would work - pros and cons?   Am I completely 'wacky'....?   

Thanks!
UL

[FullRangeMan]

It already made by a builder from east europe w/2 Alpha15A.
Iam search the link now.

[Angaria]

You could disconnect the rear woofer, but then you'd have a passive radiator (or similar).  Emerald physics, along time ago, made an OB sub which is somewhat similar to what you describe, but was basically two baffles, one behind the other, separated by about a foot.

[FullRangeMan]

Dont locate the link but the photo is this:

Also pickup this w/12'' woofers dont know where:

[bladesmith]

at what point does it go from OB design, and change to a speaker with a really big port ?

[Vapor Audio]

What will happen for sure with that midrange is a nasty tunnel resonance.  I doubt it'll have much if any impact on bass, but the midrange will definitely be impacted negatively.

[Tyson]

What will happen for sure with that midrange is a nasty tunnel resonance.  I doubt it'll have much if any impact on bass, but the midrange will definitely be impacted negatively.

Very true.  And at some point the speaker starts acting like a U Frame instead of a true OB, and you'll have to watch out for cavity resonances.

[Ultralight]

Vapor & Tyson, I assume you are responding to the picture?  No probs.

But what about with a enclosed speaker box where there are one drivers on each side?  And then one is either turned off, or two driven either as a bipole (in phase) or dipole (reverse phase)?   What impact would that have? 

Thanks
UL

[bladesmith]

Very true.  And at some point the speaker starts acting like a U Frame instead of a true OB, and you'll have to watch out for cavity resonances.

Exactly....

[mcgsxr]

I think what happens in the case of what you describe is that you end up with a boxed speaker with a specific radiation pattern - monopole, dipole or bipolar according to how it is wired.

There are many examples of commercial speakers wired as you suggest.  Paradigm, Energy, Definitive Technology all made versions of what you are talking about.  Omega too I think.

Unless you are asking about a custom speaker,that you could alter the wiring of?

In any case it would do not be OB by the very nature of being boxed.

[MJK]

What will happen for sure with that midrange is a nasty tunnel resonance.  I doubt it'll have much if any impact on bass, but the midrange will definitely be impacted negatively.

I doubt it. If the baffle is 4 - 6 inches thick the first quarter wavelength standing wave would be predicted above 400 to 500 Hz. If the circular opening at the back of the baffle is big enough in diameter so that the acoustic impedance is mostly resistive the sound wave coming off the back of the speaker will just continue out into the room. No reflections means no cavity resonances. I modeled something like this a few years ago and it worked very well as an OB speaker.

[JohnR]

But what about with a enclosed speaker box where there are one drivers on each side?  And then one is either turned off, or two driven either as a bipole (in phase) or dipole (reverse phase)?   What impact would that have? 

As others pointed out, running just one driver would likely lead to odd results, if they shared the air space. It would work with just one driver if there was a divider (i.e. effectively two boxes back to back).

The answer to your question does depend somewhat on the frequency range. At low frequencies, there is no difference between the "monopole" and the "bipole" (other than output level). At higher frequencies, the "monopole" is not actually a monopole. The "dipole" is not really a dipole either...

There's also another option, which is to delay the rear driver by the propation time between them, which will (in theory, never got around to trying it) give a cardioid radiation pattern. Below some frequency that is.

As for the "OB sound", with the drivers out of phase the radiation pattern is (in theory) much the same as an open baffle, but there are differences i.e. if you have a divider the drivers are loaded by the box, and in either case there is energy inside the cabinet that might (might, just speculating here) affect what you hear above some frequency.

I think a number of answers were distracted by the title, which isn't what you described in your post. The short answer to your question is if you put a divider in, you can do what you describe. In fact, you don't need to build anything to try it/experiment, just put two speakers back to back.