Suitable midrange cone, for bandpass mid in Unity horn. - Page 53 - diyAudio
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Old 14th March 2012, 08:35 PM   #521
grec13 is online now grec13  United States
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Quote:
Originally Posted by weltersys View Post
It is possible, though most ribbons require a crossover point higher than the bandpass mids would reach, requiring the ribbon, 2" cone mids, 6" cone mids, and woofers. Getting the crossover to work would be more tricky than using a compression driver.

The ribbon HF vertical dispersion would be more narrow than the rest of the drivers, so the horn would no longer be constant directivity, one of the nice features of a Unity style horn.
thank you.
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Old 14th March 2012, 08:47 PM   #522
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Originally Posted by bwaslo View Post
put my name second on the patent.
It *would* be pretty darn amusing if this works.
You could get wide bandwidth out of a horn, without investing in a coaxial compression driver and an expensive crossover.

Downside is reduced sensitivity, but not a huge deal for the home and car.
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Old 14th March 2012, 09:14 PM   #523
bwaslo is offline bwaslo  United States
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Probably would be a tough thing to tweak up, though, not many knobs (crossover components) to work with. But maybe with some EQ....
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Old 15th March 2012, 01:49 PM   #524
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I'll bet you'll still have to eq it with some sort of network or active eq to get anything close to flat response due to the falling power response of the driver at high frequencies. You're really just replacing the electrical crossover with a mechanical / acoustical one which is way harder to tune especially since you currently have no model of it. I agree it would be cool if you can get it to work but I'd take the increased sensitivity and increased driver cost any day even for home use.
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Old 15th March 2012, 02:24 PM   #525
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Originally Posted by Patrick Bateman View Post

Basically cut a ring of closed cell foam, epoxy it to the waveguide mouth, and then determine if it causes any kind of rubbing or buzzing. If not, it should seal off the cone 100% from the dust cap of the midrange driver.

Basically we've implemented a mechanical crossover; we've physically seperated the highs from the lows, instead of electrically.
If the seal is airtight, (like a foam speaker surround) it will dampen the cone, changing it's parameters completely.
If the seal is not airtight, it will buzz.

Hope you post some on and off axis response curves of what this looks like when you are done!

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Old 16th March 2012, 04:30 AM   #526
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My "faux-axial" unity horn is looking kinda rough, but it makes music.

Click the image to open in full size.
The (semi) finished horn
Click the image to open in full size.
Click the image to open in full size.
I didn't want to wreck my QSC waveguide, so I used it as a mold. I covered it in candle wax that I heated on the stove to keep the fiberglass from sticking to it.
Click the image to open in full size.
Click the image to open in full size.
Here's some detail on the chamber in front of the woofer, which is designed to isolate the edge of the cone from the dustcap.

Here's a video of it playing:

fauxaxial unity horn.mp4 - YouTube

For comparison's sake, here's one of my car audio Unity horns. (Not a good one - or finished.)
johnny cash on unity horn (in a corner).mp4 - YouTube

Here's a JBL array, playing the same song, to give this some context.
3 driver full range-2.mp4 - YouTube
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Old 16th March 2012, 11:20 AM   #527
JLH is offline JLH  United States
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John,

You might want to try that with one of your cone tweeters. With their extremely low suspension compliance and nonexistent Xmax, you might be able to get tighter spacing for better coupling. Cool concept - I like it!
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Old 16th March 2012, 01:56 PM   #528
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John,

You might want to try that with one of your cone tweeters. With their extremely low suspension compliance and nonexistent Xmax, you might be able to get tighter spacing for better coupling. Cool concept - I like it!
After a few months of experimentation, I think I'm leaning towards a setup similar to what you are working on. That is, cone tweeters for midrange, and a compression driver at the apex.

I'd hope the faux-axial would be a low cost alternative to a conventional unity horn. But it's Achilles heel seems to be efficiency. In the video* you may notice that it's not as loud as the others, and that's because it isn't! I'd guesstimate that it's limit is about 10dB lower than the others. Even worse, as it gets close to the limit the highs get a little 'shrieky', like any paper cone woofer does. I'm guessing this is the reason that Thiel got a lil' OCD about cone resonances in their fauxaxial.

In my video with the cone tweeters**, it's surprising how smooth they sound, considering the horn has no mouth termination, the hole size was a guess, and I'm only using two midranges. With four midranges, a compression driver, and better engineering, I think this horn could shine.

Last but not least, here's a video of a comparably sized Unity horn, but with phase plugs! I'd mentioned this one a few months back, basically using phase plugs to extend the high frequency response of the midranges. I think this one is audibly superior to the others. In fact, this one could be the basis for a decent Unity horn as well. I guess I'm leaning towards the cone tweeters because the footprint is smaller.

unity with phase plugs-1.mp4 - YouTube

Here's the video with the faux-axial Unity horn:
fauxaxial unity horn.mp4 - YouTube

** Here's the video with the cone tweeters:
unity horn with cone tweeters - YouTube

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Old 16th March 2012, 04:27 PM   #529
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I knew about you trying the phase plugs, but had not actually seen it until now. I love the look of the Lowther light bulb style phase plugs. In my mind I kept thinking about a more conventional compression driver style phase plug - SURPRISE!

Sometimes I wish I could throw things together like you do. I'm just too analytical and can't bring myself to do it. Only if I could half-a$$ things half as good as you. I commend you on your abilities to knock out quick prototypes for testing. Its more efficient than making it all nice and pretty then have it fail anyway.

I keep coming back to the Misco RDC3T-A. It just works so damn well in a Unity. For the longest time I was fighting it because I couldn't get the thing to turn off in the high frequencies. This was messing up the frequency response of the compression driver and the overall phase response. Finally, I made a breakthrough in my Akabak script and found a rather simple solution. I ended up inserting a series resonance attenuation circuit across the RDC3T-As and it fixed it. It is a 3.3 ohm resistor, 14uF cap, and 0.15mH coil in series placed across the RDC3T-As which are wired for series parallel to maintain 8 ohms. A few more tweaks and I'll be satisfied enough to make a little bit more sawdust. Yeah, I know I'm slow as molasses, but that's the way I'm wired.
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Old 16th March 2012, 04:53 PM   #530
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IA few more tweaks and I'll be satisfied enough to make a little bit more sawdust. Yeah, I know I'm slow as molasses, but that's the way I'm wired.
Join the club... I've got all these great drivers sitting around that just need some horns made for them, but it takes me forever to get around to making them anymore. Currently I'm rationalizing this as just needing a better dust collector and enclosure on my cnc router so it doesn't coat my garage in saw dust when I use it, but that's yet another project. It's a vicious cycle.
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