What is the correct layout of potato masher screens, LE-175 DLH175 acoustic lens horn

[donsof]

Hi all
Has anyone ever looked at what is the best layout of these screens inside the potato masher horns?
I searched the forum, and also scratched my head on this one for a few weeks.

It seems like someone could get crazy and try to optimize what we have in the 1217-1290 / HL87 / 2305 / horn.
I have two sets of these, because I like the LE-175 driver, and wish to keep the original look of my C36's.
I know you can get a better sound with a Smith style horn, but I want to make these optimal.

So I studied these, and measured the hole patterns and placement, and drew them in autocad, and started the overlays.
To me, it looks like every other screen should rotate 15 degrees, from the screen below it.
I tried 5 and 10 degree rotations, but the outer diameter has more blocking at 12-15 degrees.

I am going to attach two pictures to look at, in case you want to join the discussion.

I understand the technical paper on the acoustic lens theory, and that you want to slow the sound wave on the outside, and allow the inner to pass through faster.

I hope you understand what I am seeing in the 3 pictures.
I am seeing a hex pattern to the holes, and looking at alignment of each hex pattern on each screen.
I say the pattern should rotate a certain amount on each screen.
I can't find a factory spec on what this is.
The first picture is looking at an example.

The second picture is an autocad screen shot of what I think should work.

The 3rd screen shot is just screen one and two overlayed in autocad. You don't want to see all holes on at once... unless you need the trip!


Maybe that was too much for the assembly people to fuss with, when these were made?
or
maybe it doesn't matter a whole bunch.

The worst possible case would be no rotation, and no blocking.

any thoughts? Don

6299462995

[ivica]

Hi all
Has anyone ever looked at what is the best layout of these screens inside the potato masher horns?
I searched the forum, and also scratched my head on this one for a few weeks.

It seems like someone could get crazy and try to optimize what we have in the 1217-1290 / HL87 / 2305 / horn.
I have two sets of these, because I like the LE-175 driver, and wish to keep the original look of my C36's.
I know you can get a better sound with a Smith style horn, but I want to make these optimal.

So I studied these, and measured the hole patterns and placement, and drew them in autocad, and started the overlays.
To me, it looks like every other screen should rotate 15 degrees, from the screen below it.
I tried 5 and 10 degree rotations, but the outer diameter has more blocking at 12-15 degrees.

I am going to attach two pictures to look at, in case you want to join the discussion.

I understand the technical paper on the acoustic lens theory, and that you want to slow the sound wave on the outside, and allow the inner to pass through faster.

I hope you understand what I am seeing in the 3 pictures.
I am seeing a hex pattern to the holes, and looking at alignment of each hex pattern on each screen.
I say the pattern should rotate a certain amount on each screen.
I can't find a factory spec on what this is.
The first picture is looking at an example.

The second picture is an autocad screen shot of what I think should work.

The 3rd screen shot is just screen one and two overlayed in autocad. You don't want to see all holes on at once... unless you need the trip!


Maybe that was too much for the assembly people to fuss with, when these were made?
or
maybe it doesn't matter a whole bunch.

The worst possible case would be no rotation, and no blocking.

any thoughts? Don

6299462995

Hi,
may be I am wrong, but as I can see You have 5 layers one over the other. so after 60 degs. the paterns repeated, so I think 60 devid by 5 is 12, so I would expect that 12 degs difference in the patern plates would be OK, but may all of that is not so important, just to slow downa the sound spead, or to produce longer sound travel path, so to introduce a phase delay in the outer wave front, bending the whole sound inphase surface.
regards
ivica

[donsof]

Hi
Yes the 15 degree rotation would repeat itself on the last plate.
The last plate is not quite so important, as its .3" wide, and only has two radial rows of holes in the stream.
Some examples of real life horns show a mixed bag on rotation.

I thought the one picture I used, was probably a pretty good example of how they should be.
I wonder what audio testing would show about these horns?
Has anyone ran the CLIO tool on them?
I don't have access to awesome testing gear.
Can these horns deliver, with a crossover below 1200HZ on an LE-85? or LE175?

Don