Tractrix Horn Help

[Sootshe]

I'm considering a timber tractrix horn with a GPA 399. It will have an Fc of 250Hz & the mouth dimensions will be 23" wide X 9" high x 16.87" deep with a 1" motorboard. It will be similar to the attached pic.

There's plenty of info to determine the lowest frequency that the proposed size horn will go to, the program used to generate the dimensions will calculate this & many other things. My problem is determining how high this horn will go to.

Would anyone know if it will go up to the upper limit of the driver? That is, to 15K?
Thanks,
John
:confused:

[Maron Horonzakz]

Yes I,m famallier with that Martinelli horn,,,And its owner,, With the proper driver it will go to 18K

[Lee in Montreal]

Yes I,m famallier with that Martinelli horn,,,And its owner,, With the proper driver it will go to 18K

Interesting. And what would that proper driver be? Anything JBL? TIA.

[Sootshe]

Yes I,m famallier with that Martinelli horn,,,And its owner,, With the proper driver it will go to 18K

To clarify, the picture of the horn is not mine, I just used it as an example of what it will look like.
Would one similar to this, with the specs given above, go all the way to the limit of the 399, that is, to 15K?

I've read some reports that horns of this type sometimes only go to 6-7K & therefore will limit the frequency range of the driver, regardless of how high the driver goes.

Thanks,
John

[Maron Horonzakz]

Not so,,,,But the polor response would suffer,,Verticle Vs Horizontal

[spkrman57]

That will change the math somewhat.

Ron sends...

[stephane RAME]

http://www.greatplainsaudio.com/downloads/399series.pdf

Stéphane

[Lee in Montreal]

http://www.greatplainsaudio.com/downloads/399series.pdf

Stéphane

Thanks for the link Steph.

"Frequency Response: 500 Hz - 15 kHz at rated power."

If the above rating doesn't include "within X db" it is a meaningless info. It might very well be 800Hz- 8Khz within 3db ;)

Manufacturers usually include a grah to back-up their claim.

[stephane RAME]

At the same Altec

http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/drivers/399-8A%2016A%20HF%20Driver.pdf

Stéphane

[Sootshe]

That will change the math somewhat.

Ron sends...

Sorry, the motorboard is 1" thick, not 1" in diameter.

The throat diameter is 1.25 inches.

[Sootshe]

At the same Altec

http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/drivers/399-8A 16A HF Driver.pdf

Stéphane

Thanks Stephane....haven't come across this before.
Looks like the response is already going to be down at least 6db at 6K anyway.

[Lee in Montreal]

I looked a bit closer at the Altec driver. It seems more like a 1Khz to 6Khz driver. With some CD correction it might go up to 10Khz where most horns will break-up.

Here's the enlarged response graph in an Altec horn.

http://img.photobucket.com/albums/v668/Lee_Vuong/JBL%20parts%20factory/Altec399.png

[Sootshe]

I looked a bit closer at the Altec driver. It seems more like a 1Khz to 6Khz driver. With some CD correction it might go up to 10Khz where most horns will break-up.Here's the enlarged response graph in an Altec horn.http://img.photobucket.com/albums/v668/Lee_Vuong/JBL parts factory/Altec399.pngThanks Lee,You can easily get hoodwinked with some of these components & their claimed responses. I would agree that the response would only be flat to 6K after viewing these graphs & from there starts to fall away. This at least gives me a starting point to determine where to bring the tweeter in.Makes you wonder what the real response of the GPA 390 driver is......they claim 300-7K, but again, no parameters of the response deviation within this range. Whatever the case, looks like the 399 will be suitable if I run 3 way & cross over around 6-7K, so I'm sure the horn will cope with this OK.Thanks,John

[cosmos]

If you build it, it's going to look pretty much or exactly like these.

[louped garouv]

what's up with the phase plug on that woofer?

to help with "beaming" of higher freqs?


looking good, nonetheless!

[Jim Hodgson]

Thanks Lee,You can easily get hoodwinked with some of these components & their claimed responses. I would agree that the response would only be flat to 6K after viewing these graphs & from there starts to fall away. This at least gives me a starting point to determine where to bring the tweeter in.Makes you wonder what the real response of the GPA 390 driver is......they claim 300-7K, but again, no parameters of the response deviation within this range. Whatever the case, looks like the 399 will be suitable if I run 3 way & cross over around 6-7K, so I'm sure the horn will cope with this OK.Thanks,John

I'm fairly certain that GPA isn't out to "hoodwink" anyone. They have a pretty impeccable reputation, actually. And most people seem to think that their drivers improve upon Altec originals in just about every instance. Just give Bill Hanuschak there a call and he'll tell you everything you want to know -- and more. I do agree (and he has said) that some of the GPA product literature is not as complete as it could be.

[Jim Hodgson]

If you build it, it's going to look pretty much or exactly like these.

OMG ... gorgeous!

(I admit this response does not add a lot to the technical discussion here. :p )

[Sootshe]

I'm fairly certain that GPA isn't out to "hoodwink" anyone. They have a pretty impeccable reputation, actually. And most people seem to think that their drivers improve upon Altec originals in just about every instance. Just give Bill Hanuschak there a call and he'll tell you everything you want to know -- and more. I do agree (and he has said) that some of the GPA product literature is not as complete as it could be.

Jim,

Sorry, didn't mean to throw any slight on GPA. I have the utmost respect for them & the products they produce. It's amazing they are producing the original Altec drivers for us to enjoy. Just meant that the specs don't always tell the full story.

As I've already said, I'll be going with the GPA drivers when I get the horns finished, so you can't get a better recommendation than that. ;)

Thanks for your input,
John