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100Hz two-way synergy project
100Hz two-way synergy project
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Old 22nd August 2019, 12:26 AM   #61
bwaslo is offline bwaslo  United States
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100Hz two-way synergy project
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Out of curiosity, for what size CD, and cone drivers, did you make the final version?
And what horiz and vertical pattern were you after?
That was for a 1"D tweeter driver (like DNA360 or DE250 it was cloned from), mids were the Celestion sealed back TF0410MR . I was going to use Eminence 2512 for woofers (mounted on the boards). Exit angles of the stub are 90 and 65 degrees, extending with plywood would be the same angles. Didn't plan on secondary flares (for simplicity) but those should probably be added for performance and to make the gargantuan thing a little less room filling.

There were supposed to be some 50mm dia, 5mm deep volume reducers in the center of the midrange mounts, I forgot those before printing. But they could be printed separately and glued in there.

Quote:
So it sounds like the secondary flare is more about lower frequency control, than what's going on say above 1kHz?
The portion of a horn that controls directivity for a given frequency depends mostly on how far out it is (further out for lower frequencies). The HF is determined pretty fast in the first few inches provided it doesn't bounce off anything on the way out.
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Last edited by bwaslo; 22nd August 2019 at 12:31 AM.
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Old 23rd August 2019, 07:46 PM   #62
mark100 is offline mark100  United States
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Thanks Bill

I get the general idea of where the HF and Lf are controlled.
But dang the HF sure seem sensitives to well past the throat, all the way to mouth.

For example, the first yellow/orange trace below is with circular petals attached to the mouth of the 60x60, at the same flare as the horn. Look at the crazy dip at 2.4kHz. I was just spit-balling stuff.



I took the 60x40 apart, cutting back the apex, and fitting it with CD exit transition plates that worked well for the 60x60.

The plates didn't work nearly as well for the 60x40.
So I tried the foam triangles/trapeziums. (Thx again freddi and billcowan, any further info appreciated...)

Anyway, the foam out at the mouth helps. But only on the vertical walls. They hurt placed anywhere on the horizontal walls.

Second trace is the dcx464 CD on the 60x40. yellow is without foam, and then with foam is purple.
Learning, but damn these synergies are touchy beasts...
Attached Images
File Type: jpg petals on 60x60.JPG (108.1 KB, 197 views)
File Type: jpg dcx on 60x40 foam compare.JPG (70.3 KB, 204 views)
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Old 23rd August 2019, 08:48 PM   #63
bwaslo is offline bwaslo  United States
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Maybe I'm seeing your graphs wrong.. Is that the response from the mids or the HF driver? 600Hz to 8kHz doesn't seem like tweeter. That 2ish kHz dip looks a lot like a midrange reflection notch (quarterwave between mid apertures and the tweeter diaphragm). The reflection notch in a Synergy horn determines the upper limit of how high the midranges could play there, the reason why a lot of people try to get the mid apertures as close as possible to the tweeter throat.
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Last edited by bwaslo; 23rd August 2019 at 08:50 PM.
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Old 23rd August 2019, 11:46 PM   #64
mark100 is offline mark100  United States
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Sorry for any confusion...
The project has been about mating a bms 4594HE with a pair of 12"s.

When referring to the bms coax CD, I've called the lower section 'HF' (up to 6300Hz), and the high section 'VHF' (>6300Hz).
When referring to the dcx464, folks have been calling the lower section of the dcx464 'mid' (up to 3200Hz), and the higher section 'HF' (>3200Hz).

I've been flip-flopping terminology, my bad.

Anyway, maybe the following might help clarify..
The pict is the 60x60 deg with one "petal" as previously described, attached to the horn. (albeit drivers removed)
The transfer function graph green trace is that of one petal, as shown in the pict.
The brown trace with the deep notch at 2.4kHz, is with the same sized petals attached to both sides of the horn in addition, so three petals total.

I can't see how the notch has anything to do with 1/4 wave reflections.
It seems to be completely about mouth termination.
I surely need help understanding !!!!
Attached Images
File Type: jpg one petal.jpg (84.7 KB, 198 views)
File Type: jpg petal compare.JPG (111.8 KB, 200 views)
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Old 24th August 2019, 02:30 AM   #65
bwaslo is offline bwaslo  United States
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So that's with a coax driver at the throat (yeah, quarter wave reflection notch not an issue then like you say). I would try covering the woofer/midrange ports with duct tape, though, to make sure you're looking at just the horn walls during troubleshooting.
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Old 24th August 2019, 12:31 PM   #66
mark100 is offline mark100  United States
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Quote:
Originally Posted by bwaslo View Post
So that's with a coax driver at the throat (yeah, quarter wave reflection notch not an issue then like you say). I would try covering the woofer/midrange ports with duct tape, though, to make sure you're looking at just the horn walls during troubleshooting.
Yep, I even tried / measured the 60x60 before putting the woofer/midrange ports in, to see what changes the ports would make.
Not much change really...maybe the ports amplified the pattern anomalies a little, but not enough to make me think the ports are a problem.

Biggest problem continues to appear to be either internal reflections in the straight sided conical horn, or mouth termination.....
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Old 24th August 2019, 05:17 PM   #67
weltersys is offline weltersys  United States
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Quote:
Originally Posted by mark100 View Post
Biggest problem continues to appear to be either internal reflections in the straight sided conical horn, or mouth termination.....
Mark,

From the picture, can't tell the angle of the "petal" to the horn side wall. If the "petals" are at the same angle as the horn wall, they shouldn't affect the horn performance much at all other than controlling dispersion to a lower frequency.

However, the portion of the turntable (and pool table) on the bottom of the horn is reflecting off axis response back across the center of the horn, definitely a bad thing as far as response linearity is concerned.

Unfortunately, the turntable must be rather small to avoid interfering with measurements, requiring a lot of rear weight to counterbalance the horn- below is an example of what happens when a gust of wind came up while checking out the prototype for the secondary expansion on the SynTripP. Later tests used a lot of bar clamps...

Art
Attached Images
File Type: jpeg Bounce.jpeg (803.4 KB, 153 views)
File Type: png Humpty Dumpty.png (942.3 KB, 61 views)
File Type: png Termination.png (378.2 KB, 68 views)
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Old 24th August 2019, 05:45 PM   #68
mark100 is offline mark100  United States
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Quote:
Originally Posted by weltersys View Post
Mark,

From the picture, can't tell the angle of the "petal" to the horn side wall. If the "petals" are at the same angle as the horn wall, they shouldn't affect the horn performance much at all other than controlling dispersion to a lower frequency.

However, the portion of the turntable (and pool table) on the bottom of the horn is reflecting off axis response back across the center of the horn, definitely a bad thing as far as response linearity is concerned.

Unfortunately, the turntable must be rather small to avoid interfering with measurements, requiring a lot of rear weight to counterbalance the horn- below is an example of what happens when a gust of wind came up while checking out the prototype for the secondary expansion on the SynTripP. Later tests used a lot of bar clamps...

Art
Ouch, damn wind ! Bummer...

The 'petals' had the same angle as the 60x60 horn. So it's really just a 60x60 with 3 sides having the rounded mouth. That's why I don't understand the deep 2.4kHz notch.

The pict on the pool table was just to show a petal. I'd never measure like that.
The attached pict shows where/how I've been measuring, both for this thread and the dcx464 thread.
The modular 12"/ dcx464/xt1464 rig is on the turntable, with the CD's acoustic center on top of turntable center.
When I put either of the synergy protos on the table, with the CD's center over turntable center, the mouths extend over the fence rail.
Fortunately the synergies are heavily rear weighted enough to allow this.
Attached Images
File Type: jpg turntable.jpg (180.0 KB, 93 views)
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Old 24th August 2019, 06:11 PM   #69
weltersys is offline weltersys  United States
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Quote:
Originally Posted by mark100 View Post
The pict on the pool table was just to show a petal. I'd never measure like that.
The attached pict shows where/how I've been measuring, both for this thread and the dcx464 thread.
Oh well, nevermind
Nice set up!
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Old 24th August 2019, 06:27 PM   #70
mark100 is offline mark100  United States
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Quote:
Originally Posted by weltersys View Post
Oh well, nevermind
Nice set up!
Thx Art

The almost too easy speaker correction available using FirDesigner led me to the test setup.
After correcting waay too many reflections waay too many times, it became obvious I had to find a quicker way to make at least half decent measurements.
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