Pyle PH714, McGee HL 1018, DAP HP 4 and Karma PT 208 horn - diyAudio
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Old 25th February 2014, 09:23 AM   #1
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Default Pyle PH714, McGee HL 1018, DAP HP 4 and Karma PT 208 horn

This is about the Pyle PH714, McGee HL 1018, DAP HP 4 and Karma PT 208 horn. Outside dimensions 465 x 245mm, cut out: 415 x 155 mm, lenght 305 mm. 1 3/8"TPI screw on connection.

Although looking quite usefull, the buildquality of this horn is awfull. The TPI inserts are +- 10 degrees of axis, comapring two off them, the insert depth differs 3-4 mm.

Click the image to open in full size.

Hopefully this will prevent some dissapointments. It's a cheap, good looking and widely available horn.

Last edited by Phenoholic Anonymus; 25th February 2014 at 10:10 AM.
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Old 25th February 2014, 09:40 AM   #2
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I've just bought a pair which I will try to modify a bit.

This is the plan:
1. Cut away the threaded insert part of the horn.
2. Expand the 1 3/8" thorat to 1.5", by sanding. (1 4/8") to try them with my JBL 2450-SL's.
3. Dampen the larger plastic surfaces to reduce ringing.

Hopefully I can improve the drawbacks mentioned do to the offset threaded insert and report the results, good or bad. At 12€ each I think it's worth a try.

Do you have any high-res pictures of the inside of the horn to give a good idea about the horn contour and the horn entry?

Regards, Fredrik
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Old 25th February 2014, 10:00 AM   #3
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It's almost impossible to have enought light in the throath and make a good picture at the same time. To add injury to insult there is another 3 mm step all around the 35mm (TPI) throath. And then the hornflare starts.

Click the image to open in full size.

You are right about the price. I am not that much dissapointed if price is considered But for a few dollars more they could have made it a proper nice horn. The choice in bigger mid horns with TPI thread is not that great. Your idea with the 1.4 or 1.5 driver might work.

Does anybody know the metric equivalent of 1-3/8" - 18 TPI thread?
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Old 25th February 2014, 10:01 AM   #4
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Just realized they are 1 3/8 threaded inserts, and 1" entry.

That would be too much of a difference to be able to sand to a 1.5" entry. Even if there was enough plastic at the throat there would probably be a discontinuity from the mouth to the horn walls.
Too bad.

Anyone that knows of a similar looking horn with 1,5 or 1,4" entry?
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Old 25th February 2014, 10:08 AM   #5
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With the extra 3mm plastic around the 35mm opening 1.5 (38mm) might just fit. If you get the insert out of the horn without destroying it...The flare, mouth area and all these things are nice on this one...

Last edited by Phenoholic Anonymus; 25th February 2014 at 10:11 AM.
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Old 25th February 2014, 10:13 AM   #6
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But isn't the opening seen from the inside of the horn just 1"? (25,4mm). +6mm = 31,4mm.

The plan was like you said but even though the insert is close enough in terms of dimensions the horn throat itself (the inside part coupling to the horn walls) is just 1" + the 3mm gap that you mentioned. That would mean a 1,5" entry would cut into the walls of the horn leaving a nasty diffraction edge which I don't want...
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Old 25th February 2014, 10:23 AM   #7
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The opening of the inside of the horn is 35 mm. That's the TPI thread. This widens to 41mm inside the horn to meetup with the square hornwalls / flare and then the flare starts.

Click the image to open in full size.

So if you have for example a Monacor KU 516 driver, with a 19 mm throat exit, the difference is 2.83 cm2 > 13.2 cm2. For a midrange horn it is not such a big deal i believe (wavelength is great compared to a 1mm edge). I am new to horns and all the throath format's. Maybe some more experienced members can help out to exactly define these differences and there effects. To be honest i expected a 35mm thread for the driver, and a round 25mm opening of the horn.
Don't know if this big gap is standard on 1-3/8" - 18 TPI thread horns.

Last edited by Phenoholic Anonymus; 25th February 2014 at 10:40 AM.
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Old 25th February 2014, 10:28 AM   #8
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Even though the thread is 1-3/8" the normal thing to do is to have the horn entry at 1" since the 1-3/8" drivers are all 1" exit.

Seems like they did such a horrible job that the 1.5" conversion might work. Thanks Phenolic!

I agree that in it's original form this horn should not be recommended to anyone
Not saying my conversion will be successful, but I'll give it a shot.
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Old 25th February 2014, 10:44 AM   #9
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I am not sure if we both are bringing the N back in Noob. Or this is standard for the TPI thread horns . Google has no answers to these seemingly obvious questions. I hope the conversion works out!

Last edited by Phenoholic Anonymus; 25th February 2014 at 10:46 AM.
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Old 25th February 2014, 10:49 AM   #10
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This is not normal. I've owned several 1-3/8 TPI horns and if they are decent they should have a flush transition to a 1" exit driver using the 1-3/8" TPI format.

The 1-3/8 is a standard for fastening the driver to the horn. Not a standard throat size.

Here is a typical 1" exit driver using the 1-3/8 threads:
Overview

Here is a typical 1" horn using the same 1-3/8 screw on format:
Dayton Audio H6512 6-1/2" x 12" Waveguide 1" Threaded | 270-318

EDIT: I see your example with the Monacor driver. And that is a very special compression driver with a smaller than normal 19mm exit, even though it uses standard 1-3/8 threads. This would require an adapter to get a good transition to most standard horns, or a custom made horn with 19mm entry and 1-3/8" threaded insert.

Last edited by FredrikC; 25th February 2014 at 11:06 AM.
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