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Quote:
Originally Posted by mtg90  /t/1475674/the-great-waveguide-shootout/150#post_23749840


Yeah but switched early on from a baffle that rotates and mic stays put to a mic that rotates while the baffle stays put. That way I did not have to glue in the fiberglass waveguides which don't have mounting holes. If I hang the mic it will always point strait down while it rotates instead of always pointing at the center of the baffle.

I think that confirms it... it must be the wood strip on which the mic is mounted. That is why the dip is at the same frequency at all angles. If it was from the baffle, then the distance to the baffle would change with angle, producing different time delays at different angles.
 

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Quote:
Originally Posted by tuxedocivic  /t/1475674/the-great-waveguide-shootout/150_50#post_23749847


I would expect a waveguide to have less diffraction than a diffraction modeler suggests. Very odd.

The SEOS doesn't have a particularly large end radius.


I is curious ha something with high directivity is so sensiive o his, but Geddes makes a big deal over it.
 

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Quote:
Originally Posted by mtg90  /t/1475674/the-great-waveguide-shootout/150#post_23749840


Yeah but switched early on from a baffle that rotates and mic stays put to a mic that rotates while the baffle stays put. That way I did not have to glue in the fiberglass waveguides which don't have mounting holes. If I hang the mic it will always point strait down while it rotates instead of always pointing at the center of the baffle.

I looked again at your setup in the first post. Maybe put a bunch of OC 703 rigid fiberglass or foam on the wood crossbar as well as the posts, which should knock out any reflections.


Also, measure a waveguide at 0 degrees first with the mic holding jig, then a measurement with the mic just hanging from its cable at 0 degrees with the wooden mic jig rotated completely out of the way. You could also do one with the jig set to 0 degrees with fiberglass/foam. Compare all three and see what you get.
 

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Discussion Starter · #185 ·
This thread is long overdue for an update...


Well it has been determined that the wooden mic support jig is at fault for the ragged response while mounted on the baffle.


It was almost three weeks ago Pitviper33 (another Matt
) came over for a few hours during the evening and we measured the response with the mic mounted in the jig vs. the jig moved away and the mic on a normal mic stand/boom. The mic stand measurement was free of the lumpiness exhibited with the wooded jig so the wooded jig must have been at fault. We then tried all sorts of different amounts and styles of damping material to knock out the reflection in almost every position or combination possible. Nothing worked to completely eliminate that reflection, not even coating the whole wooden jig with full 3-1/2" thick R-13 batts of recycled denim insulation!!!


Matt might have some pictures of our feeble attempts.


Here is a measurement comparing waveguide free air, waveguide in baffle with mic in stand, waveguide on baffle with mic in jig. Spaced 5db apart:




So at this time I am going back to the first idea which was to have the baffle rotate and the mic remain in a constant position which will allow me to use the mic stand which I know has no detrimental effects on the response. Matt did suggest an excellent way to setup the baffle so that I do not need to glue in the fiberglass waveguides to keep them from falling out and that is to measure my 0 with the baffle angled at 45 degrees on way then I can move the baffle in the opposite direction so that 45 degree measurement angle will have the baffle flat and at 90 degrees the baffle will be in the opposite 45 degree position.


The real problem now becomes how much time is left to take outdoor measurements. With my trip to Erich's next week I don't think I am going to get a chance to do much more work on it this season.



Back when I started this I thought I could knock this out in a week or two, look how that turned out



So unless I get everything out sometime this next week or Chicago has some really nice weather this November/December I think this project might go into hibernation till spring rolls around.
 

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could the whole thing be salvaged by mounting a triangle shape to the jig arm so that it doesn't reflect?
 

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something like this cut into strips and attached to the jig?




if the problem is something else, then just ignore me. :)
 

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Quote:
Originally Posted by mtg90  /t/1475674/the-great-waveguide-shootout/180#post_23849303


Back when I started this I thought I could knock this out in a week or two, look how that turned out



So unless I get everything out sometime this next week or Chicago has some really nice weather this November/December I think this project might go into hibernation till spring rolls around.



Yep...I always think the same thing. That's just how it goes.
 

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Quote:
Originally Posted by mtg90  /t/1475674/the-great-waveguide-shootout/180#post_23849303


This thread is long overdue for an update...


Well it has been determined that the wooden mic support jig is at fault for the ragged response while mounted on the baffle.


It was almost three weeks ago Pitviper33 (another Matt
) came over for a few hours during the evening and we measured the response with the mic mounted in the jig vs. the jig moved away and the mic on a normal mic stand/boom. The mic stand measurement was free of the lumpiness exhibited with the wooded jig so the wooded jig must have been at fault. We then tried all sorts of different amounts and styles of damping material to knock out the reflection in almost every position or combination possible. Nothing worked to completely eliminate that reflection, not even coating the whole wooden jig with full 3-1/2" thick R-13 batts of recycled denim insulation!!!


Matt might have some pictures of our feeble attempts.
I do have a picture!


I've been pretty swamped this summer/fall, so I haven't kept up with threads all that well. I should have posted this weeks ago.


We tried at least five different setups of absorbing material on that rig, and somehow we still never got a clean measurement. I don't have pictures of all of them. But the good news is that I think we settled on a method that should work when you next have time to test. The tilting table +45 to -45 should let you use the boom stand without worry of waveguides falling out.


Glad to hear you're heading down to Eric's. I'm sure with the two of you guys in one place, lots of interesting speaker things will happen! Let me know when you're back and find a reasonably warm day. I'd love to come over and help again for the real test!
 

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Quote:
Originally Posted by mtg90  /t/1475674/the-great-waveguide-shootout/180#post_23849303


This thread is long overdue for an update...


Well it has been determined that the wooden mic support jig is at fault for the ragged response while mounted on the baffle.


It was almost three weeks ago Pitviper33 (another Matt
) came over for a few hours during the evening and we measured the response with the mic mounted in the jig vs. the jig moved away and the mic on a normal mic stand/boom. The mic stand measurement was free of the lumpiness exhibited with the wooded jig so the wooded jig must have been at fault. We then tried all sorts of different amounts and styles of damping material to knock out the reflection in almost every position or combination possible. Nothing worked to completely eliminate that reflection, not even coating the whole wooden jig with full 3-1/2" thick R-13 batts of recycled denim insulation!!!


Matt might have some pictures of our feeble attempts.
I do have a picture!


I've been pretty swamped this summer/fall, so I haven't kept up with threads all that well. I should have posted this weeks ago.


We tried at least five different setups of absorbing material on that rig, and somehow we still never got a clean measurement. I don't have pictures of all of them. But the good news is that I think we settled on a method that should work when you next have time to test. The tilting table +45 to -45 should let you use the boom stand without worry of waveguides falling out.


Glad to hear you're heading down to Eric's. I'm sure with the two of you guys in one place, lots of interesting speaker things will happen! Let me know when you're back and find a reasonably warm day. I'd love to come over and help again for the real test!
Did the tests get resumed or moved to another thread?
 

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Did the tests get resumed or moved to another thread?
This was really Matt's (@mtg90) project. I just lived close to him, so I was helping out. I've now moved away, so I'm not going to be able to help in person anymore. I have no idea whether he's watching this thread. If I can figure out how to "mention" him in this post, I will to draw his attention.
He'll have to give the official word, but I believe that testing has not resumed. I spoke to him a couple weeks ago, and it sounded like he'd been kept busy by other projects and never got to it over the summer. It's already getting cold again in his neck of the woods, and I don't blame him at all for choosing not to do this kind of testing in the winter!
 

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Discussion Starter · #194 ·
That is the EOS-6 waveguide, and I believe the extension of directivity control you are seeing is in part due to the diffraction off the speaker cabinet.

I believe this is the cabinet I used for that test:
 

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Discussion Starter · #196 ·
Bringing this thread back from the dead for 2021!

I had recently purchased a couple different horns to test. I was doing my usual method of taking some quick on axis measurements of the various driver/horn combos by laying the driver flat on a little stand with the waveguide pointing upwards towards my mic. Not very scientific but it gets the job done when all I want is a basic idea of how it performs.

I though this is good and all but I would really like to get some off axis / polars in a fashion where it was quick and easy to setup and measure. I thought back to this thread and the mess that my original rig turned out to be, a massive thing that took forever to setup, could only be used outdoors and still had lots of problems I never worked out.

Then I had a major light-bulb moment and realized I have everything I need to make a simple, compact, fully adjustable waveguide/horn mounting/measuring rig that can be used indoors. If this works I'm sure I'll be dumping hundreds if not thousands of measurements here so stay tuned.
 

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Bringing this thread back from the dead for 2021!

I had recently purchased a couple different horns to test. I was doing my usual method of taking some quick on axis measurements of the various driver/horn combos by laying the driver flat on a little stand with the waveguide pointing upwards towards my mic. Not very scientific but it gets the job done when all I want is a basic idea of how it performs.

I though this is good and all but I would really like to get some off axis / polars in a fashion where it was quick and easy to setup and measure. I thought back to this thread and the mess that my original rig turned out to be, a massive thing that took forever to setup, could only be used outdoors and still had lots of problems I never worked out.

Then I had a major light-bulb moment and realized I have everything I need to make a simple, compact, fully adjustable waveguide/horn mounting/measuring rig that can be used indoors. If this works I'm sure I'll be dumping hundreds if not thousands of measurements here so stay tuned.
Well heck man I’ll just send all mine stacked up for testing to you


Sent from my iPhone using Tapatalk
 

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Discussion Starter · #198 · (Edited)
I've slowly been assembling this rig over the past week or so, I had to design and 3d print a few different parts and while I had it mostly assembled the past couple days I finally got around to taking a few preliminary measurements with it today.

So what I came up with is basically a simple structure of 2020 aluminum that allows me to adjust the width of the rig to conform to the waveguide being tested so no need to make baffles for every waveguide. I am currently using some 8" diameter sonotube that I had ripped into quarters and covered with acoustic foam as wings on the outside to minimize any kind of diffraction when moving off axis. Though I do plan on picking up some 16" sonotube, ripping it in half and testing it with/without foam as well. So far it seems to be working well, though I've only tested that JBL HM17-25 waveguide which I have mounted. The measurements are clean without any noticeable diffraction ripples out to 90 degrees which is what I was shooting for.

There is only one small issue which is that I am getting some kind of consistent SPL falloff at lower frequencies (below where the waveguide pattern control stops). I'm not 100% sure of what's causing it, but it's one of the reasons I wanted to try the larger sonotube roundover wings on the sides. I may also try using some flat sections on the sides before the large roundovers. It's still easy to see where the pattern control of the waveguide ends (espeically in the polar sonogram) but it would be nice to have the traces converge better at low frequencies.

Here are some initial photos and graphs:
IMG_2026-sm.jpg
IMG_2028-sm.jpg
HM17-25 Horizontal Off Axis.png
Normalized Plot:
HM17-25 Horizontal Off Axis Normalized.png
Polar Sonogram
HM17-25 Horizontal Polar.png

Edit:
I took vertical measurements of this horn as well but rather then clutter up the thread with what will likely be a ton of the different measurements for all the different waveguides and horns I've just decided to create a page and upload the measurements on my own website so everything is better presented and easier to navigate.
Link to that here.

Obviously more will get tested and added soon.
 

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Discussion Starter · #200 ·
Some electronics fun, should make taking the measurements a little easier/faster:

I also just updated my REW installation (I was still using a version from a few years back) and realized I have been missing out an whole bunch of interesting stuff. I especially like the ability to keep the measurement name and automatically add sequential numbers to further measurements.
 
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