Open Baffle offset

[PeteMcK]

Hi Guys,

I'm planning the layout of my OB, It'll be a half-ellipse shape,
and was wondering how important it is to offset the mid & tweeter? (I think it would look best if they aren't offset).

I was also wondering whether I should put the tweeters below the mid, rather than above? I turned my usual speakers upside down (on top of my subs) last week just for the hell of it, and found that having the tweeters in the middle seemed to give a more 'integrated' sound.

cheers,
Pete McK

[Nuuk]

I'm planning the layout of my OB, It'll be a half-ellipse shape,

This is one of those questions where you need to post a picture.

If the half-ellipse is cut vertically, your drivers will effectively be off-centre unless one is placed exactly half way between top and bottom.

If the cut is horizontal, I would ay yes, place them slightly off access.

As regards the relative placement of the mid and tweeter, build a test baffle first and listen to that for a few weeks before building your finished baffle.

[Svante]

Originally posted by PeteMcK
Hi Guys,

I'm planning the layout of my OB, It'll be a half-ellipse shape,
and was wondering how important it is to offset the mid & tweeter? (I think it would look best if they aren't offset).

cheers,
Pete McK

Try to simulate the baffle with my program "The Edge" before building! I'd say that the placement is pretty important for the resulting frequency response.

An example would be this, where the green curve has the driver centered and rather low on a half elliptic baffle, the red curve has the driver high up and slightly off-centre. I'd choose the red curve.

[goudey]

The symmetrical layout may work (the varying distance to the edges from the elliptical shape will help prevent dramatic diffraction effects). Or it may not. Too much symmetry is generally not good, even for an open baffle.

I would recommend building a prototype. Inexpensive material can be used. I have built an open baffle prototype using thin hardboard, two layers laminated together. The prototype needn't be ridgid, but may need to be supported by hanging it from a frame of some sort.


I recommend against using "The Edge" simulator since the results obtained for the open baffle case do not relate well to measured results. The simulator does not appear to implement the Generalized Multipole Technique that I would use for such a simulation. Such a simulation would distribute dipole sources of sufficient quantity/location to match the boundary conditions. It is far easier to build the prototype.

[Svante]

Originally posted by goudey

I recommend against using "The Edge" simulator since the results obtained for the open baffle case do not relate well to measured results. The simulator does not appear to implement the Generalized Multipole Technique that I would use for such a simulation. Such a simulation would distribute dipole sources of sufficient quantity/location to match the boundary conditions. It is far easier to build the prototype.

Could you give a reference on "Generalized Multipole Technique" so I can read up on this. I admit that the directivity of the edge sources is not very advanced in The Edge, but I had thought that the results would be reasonably accurate straight in front of the speaker.

Are you suggesting that the edge sources should be dipoles?

Also, would you have some measurements to share for comparison with The Edge?

[PeteMcK]

I'll try offset the first time then, (it's a horizontal cut),
and see how it works out...

Pete McK