This is either very wrong or I have still not understood diffraction from baffle edge

[AllenB]

Two LeCleach horns won't meet up when back to back, an attempt to force early termination means a reflection. Not that this is the worst option, it's more that they're just so clean to begin with.

The downside is that the sliding parameter that allows them to have such good specs is the directivity. This directivity goes from one extreme to the other.

 

[gedlee]

Thanks, I think I understand, but I'm not sure. Regards a dipole, the short time delta of the diffractions at an abrupt baffle edge causes the relatively narrow, deep null, and by comparison the null is spread wider around the curve of the torus baffle due to the longer time delta, the peaks are likewise spread and thus diminished?

I'm not clear on what you are saying. When a circular baffle is used in a dipole there will be on axis ripples from the edge diffraction, which will move lower as the radius of the baffle gets larger, going away for an infinite baffle. With a torus there won't be any significant diffraction (a small amount at LFs) so there won't be any axial aberrations. The directivity will change however - from an infinite baffle.

 

[scottjoplin]

I'm not clear myself. I meant the off axis null. I'm trying to understand what you said in the context of what I've seen in the sims. I'm not sure I'm using the term "time delta" correctly, is it the length of time over which the diffraction happens?

 

[gedlee]

Symmetry requires an in-plane null off axis.

The time delta is the time for an impulse from the source to reach the diffraction point. Basically the distance from source to diffractor.

 

[scottjoplin]

When a circular baffle is used in a dipole there will be on axis ripples from the edge diffraction, which will move lower as the radius of the baffle gets larger, going away for an infinite baffle. With a torus there won't be any significant diffraction (a small amount at LFs) so there won't be any axial aberrations. The directivity will change however - from an infinite baffle.

I still don't understand why there appears to be no on axis interference nulls with the torus, are you saying it's because there's no significant diffraction?

 

[454Casull]

I still don't understand why there appears to be no on axis interference nulls with the torus, are you saying it's because there's no significant diffraction?

It does appear that's exactly what he's saying. Possibly for the same reason that doing a wide, gentle radius on a typical baffled speaker would also reduce on-axis interference.

 

[scottjoplin]

It's what the sims have shown, yet some are adamant it can't be so, which adds to my confusion.

 

[AllenB]

I'd have thought it was clear, the reduced effect of the diffraction takes away the source that causes the null.

As you spread energy, pressure drops off quickly.

 

[scottjoplin]

I didn't understand why the effects of the diffraction was dismissed so readily by Charlie Laub https://www.diyaudio.com/forums/full-range/361790-siegfried-linkwitz-miss-trick.html#post6381180 It made me wonder if I'd missed some other explanation or fundamentally misunderstood the meaning and nature of diffraction.

 

[AllenB]

I have a number of problems with that post on a technical level. (Not to mention that I don't believe Earl decided against going dipole based on it having 'double diffraction'. That doesn't sit right on a couple of levels.)

 

[scottjoplin]

I also wonder if I'd misunderstood what Earl meant about it's effect on the polars as it seems Don did here, ie, from the baffle edge? https://www.diyaudio.com/forums/full-range/361790-siegfried-linkwitz-miss-trick-7.html#post6384911 and here? https://www.diyaudio.com/forums/full-range/361790-siegfried-linkwitz-miss-trick-7.html#post6384911

 

[scottjoplin]

Sorry, screwed up above re the links, I should have posted this quote first to show what I mean about possible misunderstanding https://www.diyaudio.com/forums/full-range/361790-siegfried-linkwitz-miss-trick-7.html#post6384776

 

[digitalthor]

Culcrum acoustics says they can counteract internal reflections in a compression driver, with FIR ��#2 - Temporal Equalization (TQ) - an overview - YouTube
As far as I know.... No one can change or correct a response in more than one location at a time. Same goes for baffle, throat and internal reflections. I think Earl referred to this as a filter being a 1D , It could never solve a 3D problem.

 

[gedlee]

It does appear that's exactly what he's saying. Possibly for the same reason that doing a wide, gentle radius on a typical baffled speaker would also reduce on-axis interference.

I still don't understand why there appears to be no on axis interference nulls with the torus, are you saying it's because there's no significant diffraction?

That is correct.

I didn't understand why the effects of the diffraction was dismissed so readily by Charlie Laub. It made me wonder if I'd missed some other explanation or fundamentally misunderstood the meaning and nature of diffraction.

I have a number of problems with that post on a technical level.

I read those posts and had a problem with them as well. I didn't like the tone of the thread so I avoided it.

 

[scottjoplin]

Thanks Earl, I understand