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An incorrect way to do a Synergy horn
An incorrect way to do a Synergy horn
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Old 26th November 2014, 02:30 AM   #1
unaHm is offline unaHm  United States
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Default An incorrect way to do a Synergy horn

Click the image to open in full size.

Made from cardboard, glued together with Gorilla glue.

Using Bill Waslo's spreadsheet. The only thing I changed was the throat size for the compression drivers I have.

Drivers = Eminence Alpha 8a, Pyle PDS521.

So far, sounds good, but needs some minor tweaking. The left compression driver sounds quieter at the moment, but that might be poor wiring.

AV receiver is doing the EQ for each driver.

I will also paint and finish them, and make a 16 litre box for the Alpha 8a.
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Old 26th November 2014, 03:02 AM   #2
xrk971 is offline xrk971  United States
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An incorrect way to do a Synergy horn
Nice! Foam Core would work better next time.
What was the design horn frequency and angles? You will have cardboard wall vibrations that will reduce the sensitivity and add harmonic distortion. Use latex caulking liberally to act as damping material and put on second layer of cardboard. You will gain about 6 to 9dB in spl and reduce HD by 10 to 15dB. Big changes for a little more work. The absorber panels can be smaller than real horn wall panels and be rough cut.
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Old 26th November 2014, 03:30 AM   #3
unaHm is offline unaHm  United States
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Thanks X. I was thinking of doing a ribbing-style of brace system, but yes, I'll get some caulk and add some constrained layer damping.

The reason I say that it's not correct is because it's only two drivers. But, recently I've been lost in the maths. I'm using my ears again, and they are pleasant and accurate.

Another reason for cardboard was that I had numerous boxes with folds, and so where the second stage of the horn starts, the fold would exist there. It saved on gluing 8 main panels, only 4.

I had a quick look at the spreadsheet, and I left everything default except for the size of the throat...0.972 inches (1.375" * 0.707). Probably wrong.

I'll try foam core next time. The bandsaw did a good job, and I essentially cut everything in one pass from two templates by stacking the cardboard up.
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Old 26th November 2014, 04:15 AM   #4
winslow is offline winslow  United States
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Even like that, I bet you can see why people love them so much.
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Old 26th November 2014, 05:13 AM   #5
unaHm is offline unaHm  United States
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To add to that, I've found that having a stereo pair makes all the difference. Even with the 90 degree horizontal dispersion pattern, panning positions at naturally obvious. Anything in a mix that isn't panned blends together from both sources very evenly. I feel like I'm listening to an expensive pair of speakers in a well-treated room.

The picture shows otherwise...

X, I think I'm going to make a pair that have pattern control to 250Hz, but maybe with a 60x45 (w x h) pattern, so I get more of the sound at my listening position (and not going where it's not needed).

I'll fiddle with Bill's spreadsheet tomorrow, but I had one question for you: does PVA glue work with foam core board? The gorilla glue is quite quick, and allows me to work inside (hence the speed), but it's probably overkill...
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Old 26th November 2014, 09:35 AM   #6
natehansen66 is offline natehansen66  United States
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Cool experiment! Any measurements?
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Old 26th November 2014, 02:44 PM   #7
weltersys is offline weltersys  United States
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Quote:
Originally Posted by unaHm View Post
Drivers = Eminence Alpha 8a, Pyle PDS521.

So far, sounds good, but needs some minor tweaking. The left compression driver sounds quieter at the moment, but that might be poor wiring.
It also could be the left driver, cheap HF drivers often are inconsistent from unit to unit.

If you swap them you will find whether the difference is due to "poor wiring" or crappy driver quality control.
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Old 26th November 2014, 04:19 PM   #8
unaHm is offline unaHm  United States
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Good point, and one worth remembering. I know this pair match well, so I might have wired them out of phase, or am using a particularly bad wire. I'll check shortly.
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Old 26th November 2014, 04:24 PM   #9
xrk971 is offline xrk971  United States
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An incorrect way to do a Synergy horn
Yes, PVA works well with FC - use hot melt glue to tack pieces in place (or glue entire thing in hot melt) the use PVA and your finger to make a fillet. It seals and makes nice radiused fillet at seams.
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Old 26th November 2014, 05:20 PM   #10
unaHm is offline unaHm  United States
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Ok. I just wanted to make sure as I've tried another type of glue that refused to stick to the surface...or the foam inside.

Well, that HF problem has gone away. I ran the auto calibration procedure on my receiver, and now everything is even. I think it had to tame the Alpha 8a channels a bit, as they were very 'present'.

Measurement-wise, RTA on my phone doesn't show much, except that the frequency response is relatively level. It's also interesting to see how 'lively' dynamically the mid range in music is!
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