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Old 06-29-2013, 08:09 PM - Thread Starter
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Updated post:

New design:
http://www.avsforum.com/t/1479511/the-cobra-h12-290-horn-build/30#post_23560861

Construction:
http://www.avsforum.com/t/1479511/the-cobra-h12-290-horn-build/30#post_23564492



Original post: So here I go again, this time its going to be pretty awesome. I have a few revisions I want to make, so this is going to be modified a few times before I actually build.. However I have the first iteration posted here.

Goal: Get the most output out of the MFW15, in a more compact enclosure. The cobra's job is high output at 25hz and up, but still maintain decent output at 20hz. My other design is the Gladiator (drawing not done), and it focuses on frequency extension, which brings the corner frequency down to about 19Hz. The Gladiator has identical outside dimensions to the Cobra, however the horn is folded a bit differently.

Cobra = kinda looks like a coiled cobra inside, and I like the ring of it.
H (horn), 12 = 12 cubic feet exterior, 290 = 290 liter horn.

The cutsheet for this is VERY straighforward, no wasted wood. I'm not done with the cutsheet, however I am pretty sure it will fit within 1 and a quarter to 1 and a half sheets.

Approx: 35"7/8 x 24 x 24 7/8






Gladiator:
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Old 06-30-2013, 04:53 PM
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Funny I was just doing something similar and trying to design a 25hz FLH myself. I will be using an 18 but still interested and seeing what your results will be. Also interested in seeing how much better the real world results will be compared to the simulated ones.
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Old 07-01-2013, 04:53 PM - Thread Starter
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Quote:
Originally Posted by chrapladm View Post

Funny I was just doing something similar and trying to design a 25hz FLH myself. I will be using an 18 but still interested and seeing what your results will be. Also interested in seeing how much better the real world results will be compared to the simulated ones.

Yeah I just re-built the Cobra, and will give the Gladiator a try. Looks like the Cobra will take it, but the Gladiator might be the best candidate for a flat to 20hz journey. The Cobra looks like it will be best for higher output and a better balance for HT and Music. Both will benefit from a sealed cabinet loading and should be quite safe to push at their max potential along with a high pass around 10-15hz. Otherwise for the regular joe they wont need the high pass.
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Old 07-01-2013, 04:56 PM - Thread Starter
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Here's a quick pic of a simplified Cobra;

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Old 07-01-2013, 07:06 PM
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Looks like a VERY simple build! A side by side with the F20 would be awesome.

Oppo 103D
Samsung pn64f8500
Pioneer vsx-82txs
And a bunch of DIY speakers and subs.
Coming soon: Dirac Room Correction
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Old 07-02-2013, 12:42 AM
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I think the whole journey of designing something yourself and have a successful response is all the worthwhile. I don't like to compare subs to other DIY because I feel it gives a negative impact on others trying because they can not best another design. My FLH design won't be better than LilMikes f20 but I do enjoy building and creating something on my own. If my design doesn't serve my purpose then I will just build one of his. Great designs and I continue to learn from him. I just hope I can learn more as I go out and design/build my own.

I don't think this will dig as deep as the F20 but I think this is a lot smaller.
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Old 07-02-2013, 05:14 AM - Thread Starter
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Quote:
Originally Posted by Stumbo View Post

Looks like a VERY simple build! A side by side with the F20 would be awesome.

I can do that tonight, just a side-by-side size comparison? That's easy enough, just build a 3D shape the size of the F20..
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Old 07-02-2013, 05:22 AM - Thread Starter
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Quote:
Originally Posted by chrapladm View Post

I think the whole journey of designing something yourself and have a successful response is all the worthwhile. I don't like to compare subs to other DIY because I feel it gives a negative impact on others trying because they can not best another design. My FLH design won't be better than LilMikes f20 but I do enjoy building and creating something on my own. If my design doesn't serve my purpose then I will just build one of his. Great designs and I continue to learn from him. I just hope I can learn more as I go out and design/build my own.

I don't think this will dig as deep as the F20 but I think this is a lot smaller.

Yes, the journey between design and result is what makes it all worthwhile!

Comparing to other DIY is ok, since each DIY is built with its own specific purpose. So its not really about comparing "which one is better", but more about "which one fits my situation best?". The more proven DIY projects are completed, the more is available to people with situations similar to our own. If the design ends up measuring up to its purpose, then it ends up on a sticky and people can also build it. I think the real reward after building and testing is people starting to build your creation.. lilmike probably had a single tear the first time he saw a build thread of his own F20 biggrin.gif
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Old 07-02-2013, 09:15 AM
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Quote:
Originally Posted by diaz View Post

Yes, the journey between design and result is what makes it all worthwhile!

Comparing to other DIY is ok, since each DIY is built with its own specific purpose. So its not really about comparing "which one is better", but more about "which one fits my situation best?". The more proven DIY projects are completed, the more is available to people with situations similar to our own. If the design ends up measuring up to its purpose, then it ends up on a sticky and people can also build it. I think the real reward after building and testing is people starting to build your creation.. lilmike probably had a single tear the first time he saw a build thread of his own F20 biggrin.gif

That sums up my designs in a nutshell, there is always a compromise. For me, the process usually starts something like this: "What can I do with this given these constraints?"

It's both awesome and humbling to see others building my designs, and it is quite satisfying to hear that people are happy with the results.

Honestly though, it's even better to see my work used as a springboard by other DIYers and to see new designs being shared with the community.

Thanks!
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Old 07-02-2013, 09:47 AM
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the spiral fold is a good approach.

be sure to brace it well.
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Listen. It's All Good.
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Old 07-03-2013, 03:30 AM - Thread Starter
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Quote:
Originally Posted by lilmike View Post

That sums up my designs in a nutshell, there is always a compromise. For me, the process usually starts something like this: "What can I do with this given these constraints?"

It's both awesome and humbling to see others building my designs, and it is quite satisfying to hear that people are happy with the results.

Honestly though, it's even better to see my work used as a springboard by other DIYers and to see new designs being shared with the community.

Thanks!

The thanks goes to you sir biggrin.gif
Quote:
Originally Posted by LTD02 View Post

the spiral fold is a good approach.

be sure to brace it well.

It is definitely part of the plan, thanks for the input! smile.gif
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Old 07-04-2013, 01:57 PM - Thread Starter
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Preliminary Hornresp for recordkeeping sake. Will update this post with final hornresp dimensions.

Gladiator.txt 0k .txt file

Updated 300L version
Cobra.txt 0k .txt file
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File Type: txt Gladiator.txt (418 Bytes, 39 views)
File Type: txt Cobra.txt (413 Bytes, 24 views)
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Old 07-04-2013, 09:18 PM - Thread Starter
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Here is the reworked version of the cobra. A bit of bracing here and there, in grey is the previous cobra. Improvement in the 20Hz area, flatenned response. Because of these adjustments, the cobra is now an internal 300L..


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Old 07-05-2013, 10:29 AM
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i kind of thought the other one was a better design.

also, the bracing isn't to keep the wood from breaking at the joints,
it is to keep the panels from flexing during useage.

as such, you want the bracing to be along the horn path to
keep the largish panel centers from vibrating.

there are some examples here: http://www.volvotreter.de/th.htm

Listen. It's All Good.
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Old 07-05-2013, 01:22 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

i kind of thought the other one was a better design.

also, the bracing isn't to keep the wood from breaking at the joints,
it is to keep the panels from flexing during useage.

as such, you want the bracing to be along the horn path to
keep the largish panel centers from vibrating.

there are some examples here: http://www.volvotreter.de/th.htm

Thanks for the link! Yeah I prefer the simplicity of the first horn, but the second one has a flatter response.. what do you think?

Also the bracing isn't shown in this, I just added corners for now thinking it might help reflect the sounds, but I would like some input on that.
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Old 07-05-2013, 06:11 PM
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How big (or small) of a wavelength are you trying to reflect around that corner?
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Old 07-05-2013, 06:37 PM - Thread Starter
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Quote:
Originally Posted by lilmike View Post

How big (or small) of a wavelength are you trying to reflect around that corner?

Well the passband is from ~18hz to ~100hz, so I'm not exactly sure what you mean
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Old 07-05-2013, 06:53 PM
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OK,

How long is a wavelength at 18 Hz?

1126/18 = 62.55 feet

How long is a wavelength at 100 Hz?

1126/100 = 11.26 feet

So - how large is the reflector, say 12 inches?

At 100 Hz, the reflector is 1/11 of a wavelength, so it won't really reflect much. At 18 Hz, the reflector is only 1/63 of the wavelength.

So - the reflectors don't actually reflect much, at least not in the band we operate the sub in. The wavelengths are large enough to where the sound doesn't "notice" the corner if the dimensions are right.

They're used for other reasons though, cabinet strength, filling "dead" space in corners, and as a convenient spot to mount input cups, wheels, handles, and such.
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Old 07-05-2013, 07:07 PM - Thread Starter
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Quote:
Originally Posted by lilmike View Post

OK,

How long is a wavelength at 18 Hz?

1126/18 = 62.55 feet

How long is a wavelength at 100 Hz?

1126/100 = 11.26 feet

So - how large is the reflector, say 12 inches?

At 100 Hz, the reflector is 1/11 of a wavelength, so it won't really reflect much. At 18 Hz, the reflector is only 1/63 of the wavelength.

So - the reflectors don't actually reflect much, at least not in the band we operate the sub in. The wavelengths are large enough to where the sound doesn't "notice" the corner if the dimensions are right.

They're used for other reasons though, cabinet strength, filling "dead" space in corners, and as a convenient spot to mount input cups, wheels, handles, and such.

Ok thanks, then I can keep the two upper ones and make hand/grip holes for transport. Much more convenient that way lol
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Old 07-06-2013, 01:09 PM - Thread Starter
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Here's the size difference between the Cobra and the F20. Keep in mind that the F20 has a good 2-3dB advantage over the Cobra.

Cobra F20 Size Comparison.jpg 34k .jpg file
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Old 07-06-2013, 05:04 PM - Thread Starter
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After careful consideration, I will lock in with the original simpler Cobra design. There is plenty of headroom for adjustments here and there, and its natural curve favors a great blend for either music or HT - but definitely geared for HT.
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Old 07-14-2013, 02:09 PM - Thread Starter
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Here's something I was thinking about - the issue I was running into with the original design was the fact that the speaker is a bit hard to reach from the side. So I came up with this drawing, which would use a top access panel instead and would be easy to install the speaker. What do you think?

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Old 07-16-2013, 02:00 PM - Thread Starter
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Ok, so I called a few lumber yards today, and I found a killer deal on 60x60 baltic birch. I couldn't pass it up, since it would be better quality than the chinese voided birch - and end up with a tighter higher quality box.

THE PROBLEM: I cannot use my original Cobra dimensions, as too much wood would be wasted. So I went and stuffed the Cobra inside a 30x30x24 enclosure using sketchup and horresp, and this is the result:






Is this a good compromise?
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Old 07-16-2013, 02:11 PM
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Hmmm, seems to me that the flare rate gets slower as you go, not faster, which isn't really optimal. I'd personally try to make the mouth a bit bigger, the throat can be a bit smaller yet.
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Old 07-16-2013, 05:45 PM
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Quote:
Originally Posted by lilmike View Post

That sums up my designs in a nutshell, there is always a compromise. For me, the process usually starts something like this: "What can I do with this given these constraints?"

It's both awesome and humbling to see others building my designs, and it is quite satisfying to hear that people are happy with the results.

Honestly though, it's even better to see my work used as a springboard by other DIYers and to see new designs being shared with the community.

Thanks!

Looks like people have actually used the old tutorials.....this is awesome. My old Insubnia prototype (that lilmike topped with his 25Hz version) still rocks out in my house....as well as doing bass guitar work now and then.

JSS
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Old 07-16-2013, 08:11 PM - Thread Starter
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Quote:
Originally Posted by lilmike View Post

Hmmm, seems to me that the flare rate gets slower as you go, not faster, which isn't really optimal. I'd personally try to make the mouth a bit bigger, the throat can be a bit smaller yet.

Yeah that's the problem with a more compact horn, it seems to be difficult to keep an increasing rate without boosting the 50 hz range too much. And the best I can do for the mouth size is about 25% above SD.

Ok here's another stab at it.. this time I bumped the size to 36 x 36 x 22. That curve is SOLID until 20hz, and the schematic looks pretty close to textbook. Will need 3 60x60 sheets for this... I could build it to 24 inches wide too..





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Old 07-16-2013, 09:15 PM - Thread Starter
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Ok, I think I'm done lol... 36x36x24 seems to be what 60x60 sheets like to do..

Here's a refold of the last horn, looks like a better performer (only one 180 fold) , easier to build other than a side hatch. I took my time to make it right - the response is flatter than the last, but mostly due to being 2 inches wider.

This is what I am building unless there is an issue with it.. I'm pretty sure its going to be awesome, the only thing is that its going to be about 12 inches taller than the original cobra lol.. Oh well, bang for the buck.




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Old 07-16-2013, 09:22 PM - Thread Starter
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Old 07-18-2013, 08:21 AM
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Nice. That response looks an awful lot like a THT. When do you make sawdust?

JSS
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Old 07-18-2013, 02:35 PM - Thread Starter
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Sawdust files next week. I get the wood on tuesday-wednesday. I have a feeling 1 will be enough, but I have another speaker coming and it looks like I might end up building two. I have a feeling this will be ridiculous.. I'm probably going to want to upgrade the LCR and surrounds.. lol
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