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Author Topic: Anyone willing to look at a design for me?  (Read 8441 times)

Jared Scott

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Anyone willing to look at a design for me?
« on: December 03, 2008, 03:47:45 am »

I've been working on designing my own folded horn sub (more or less because I have nothing better to do with my free time at the moment).  I have modeled up both the response and the physical design.  I am curious if anyone would be willing to take a look at my design and offer their opinion as to whether they think it would be worth it to try to build or just chalk it off as a learning experince.

I have stuff available in both CAD viewable files and jpegs, as well as the driver specs.
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Art Welter

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Re: Anyone willing to look at a design for me?
« Reply #1 on: December 03, 2008, 12:46:21 pm »

Jared,

Post it up! JPEG works for me.

Art Welter
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Iain_Macdonald

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Re: Anyone willing to look at a design for me?
« Reply #2 on: December 03, 2008, 12:50:07 pm »

Jared,

Have you modeled it in Horn Response? If you have, please post a jpg of the input parameters page. Lots of people use it, and you are likely to get a reply.

Iain
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Jared Scott

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Re: Anyone willing to look at a design for me?
« Reply #3 on: December 03, 2008, 04:43:38 pm »

Alright here goes:

External cabinet dimentions are 45"x45"x20"
Estimated program power rating will be 2000-3000 watts rms.
Driver: http://www.diycable.com/main/product_info.php?cPath=24_93_15 0&products_id=681

Modeled number, impedence, phase, and group delay
http://i4.photobucket.com/albums/y136/Parasitic_Whim/hornnumbers.jpg

Wire-frame side view
http://i4.photobucket.com/albums/y136/Parasitic_Whim/18inchhorn.jpg

3-D model
http://i4.photobucket.com/albums/y136/Parasitic_Whim/18hornassembly.jpg

Predicted output for 1, 2, 4, and 8 horns at 2.83 volts
http://i4.photobucket.com/albums/y136/Parasitic_Whim/horn283v.jpg

Predicted output for 1, 2, 4, and 8 horns at 2000 watts rms per cabinet
http://i4.photobucket.com/albums/y136/Parasitic_Whim/hornprogrampower.jpg
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Marjan Milosevic

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Re: Anyone willing to look at a design for me?
« Reply #4 on: December 03, 2008, 05:52:41 pm »

Hello Jared,

First of all you have to learn which drivers are suitable for horn loading.

That one is not!

That driver is more suitable for a car subwoofer or a home cinema.

It has too low Fs, too high Qts and too low BL and way too low db/1m.

Also i dont think it will survive the compression made inside the horn and will tear apart in mater of hours (if not minutes) with 2000W applied to it.

As for the box it self. Your idea in general is ok but the firs part of the throat is too complicated for build. That is totally unnecessary.

For 360 US$ you can find much better drivers that are made for horn loading.

What is you final goal with this?

Marjan Milosevic

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Re: Anyone willing to look at a design for me?
« Reply #5 on: December 03, 2008, 05:54:06 pm »

One mora thing.

How did you come up with a same number for ATC and VTC?

Jared Scott

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Re: Anyone willing to look at a design for me?
« Reply #6 on: December 03, 2008, 07:12:06 pm »

I'm treating this as more of a learning experience than anything.  I basically posted this because I wanted to know if I was on the right track, which obviously, judging by your response, I'm not.

As for the ATC/VTC thing, my picture doesn't include one part that would be inside the throat chamber (too hard to see it inserted in the model).  With the piece installed, it would provide 1182 square centimeters of chamber area.  And I designed the chamber so that when the driver is at peak outward excursion there is 1182 cubic centimeters between the driver and the chamber walls.  I'm guessing this was an incorrect assumption on how to calculate those numbers.  And just curious as to why it would tear itself apart so quickly?  The construction materials are also almost identical to the LAB12 driver.

As for the driver, I selected it because of it's similarities to the LAB12 driver.  I assumed the Fs wasn't the best. But the Qts is almost the same as the LAB12 driver (0.40 vs 0.38), it's got 3.6T-M more BL than the LAB12, and only 0.8 dB less sensitivity.  To me, it looked quite capable in comparison to a driver that I know performs very well in horn loaded situations.

As for the complexity of the enclosure, I designed it with ideal curvature/angles.  To build it, I would obviously modify the design to use flat panels instead of so many complex curves.

This isn't meant to be argumentative, just an explanation of where my thinking was coming from.
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Elliot Thompson

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Re: Anyone willing to look at a design for me?
« Reply #7 on: December 03, 2008, 09:52:51 pm »

Jared Borchardt wrote on Thu, 04 December 2008 00:12



As for the driver, I selected it because of it's similarities to the LAB12 driver.  I assumed the Fs wasn't the best. But the Qts is almost the same as the LAB12 driver (0.40 vs 0.38), it's got 3.6T-M more BL than the LAB12, and only 0.8 dB less sensitivity.  To me, it looked quite capable in comparison to a driver that I know performs very well in horn loaded situations.



The size of the driver makes a huge difference when you are comparing QTS numbers.

For an 18-inch driver it is a QTS ranging from 0.2 - 0.3 that is needed for horn loading. The Maelstrom is 0.4

The Tesla meters should also be around 35 - 24 whereas, the Maelstrom is only 18. That is 1 TM lower than the JBL 2241. That is not a large motor for an 18-inch driver in terms of Horn-Loading. However, 14.9 TM is huge for a 12-inch woofer. Remember, you need a strong motor for you firing through a small opening in which a lot of air pressure build up will occur between the cone and the wood or should I say compression chamber.

If you are in need of an 18-inch driver that is focused on horn loading, you can visit www.speakerplans.com for that's all the designers focus on (18 inch drivers/Folded Horn bass cabinets) over there. And they know lots of them.  

I was actually looking for an old Lab 12 response chart so you can compare your design to the Lab Sub since both designs share the same outer dimensions. Maybe a Lab Sub user can compare their simulation to your design.

Best Regards,





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Elliot

Art Welter

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Re: Anyone willing to look at a design for me?
« Reply #8 on: December 04, 2008, 01:33:55 am »

Jared,

The first throat area “funny looking” part of your horn will end up being a band pass lossy thingy, rather than extending your horn length.  Eliminate all that rounded stuff and mount your speaker to the first portion of the horn, and extend that to the front right of the cabinet internally.

Your speaker cone should be as close to the upper right hand side of the cabinet as the magnet structure will allow. You may want to have the horn go a little Hypex at the throat end, particularly if you are only planning to use one or two.

Having tried a throat area like you drew to get a little more length, after comparing the much simpler to build, slightly shorter path length, the shorter version had more low end output.

No curved corners are needed, flat panels approximating the curves will be good.
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Jared Scott

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Re: Anyone willing to look at a design for me?
« Reply #9 on: December 04, 2008, 06:24:55 pm »

Lets see if I'm heading in the right direction.

Would an 18" driver with these numbers be a better fit for horn loading?:

Fs: 30.8
Qts: .28
BL: 27.1
SPL: 97.3dB

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