GJALLARHORN Re-Fold ?!?! - AVS Forum
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post #1 of 153 Old 09-23-2013, 04:46 PM - Thread Starter
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Hey Fellow Bass-heads!
I was wondering if any of you had any interest in doing a GJALLARHORN re-fold?

Being a horn lover, I know this can take some time and effort. I just don't have the expertise/knowledge to do it. I guess I could eventually learn hornresp or other variants but with everything on my plate it would probably never happen and I would be back here making a 1000 posts looking for assistance.

Anyway, I love the GJALLARHORN design...using a bad ass driver and getting much extension with the modest power demands. cool.gif I am grateful that the DIY community is so generous and is willing to share designs like this! smile.gif
The only problem I have with design are the dimensions. I was about to pull the trigger and start building, but the fit would be less than ideal in my room. I would really like to throw a couple of these behind my couch where they would blend in and there just are not a lot of placement options for me.

The length is not a problem as the couch is very long. It is the height that I need to be roughly 32"or less.

So, I am wondering if there is anyone out there that may want to take on this challenge? I am quite sure that others would benefit from an alternative low-profile design as well.

Ideally, we are talking: 24 x 32 x ??? where ??? can be 60,70, whatever takes to get the needed enclosure volume.

Any takers??

I realize there are other designs to choose from that are more behind the couch friendly, but there is not much out there that can match the GJALLARHORN at present.

Thanks in advance!


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post #2 of 153 Old 09-23-2013, 05:11 PM
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Those dimensions could potentially open up for opportunities.
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post #3 of 153 Old 09-23-2013, 05:28 PM - Thread Starter
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Quote:
Originally Posted by gpmbc View Post

Those dimensions could potentially open up for opportunities.

That's what I was thinking. There has to be many situations where an LP version would be desirable...and a ~32" height makes for a great behind the seating position application for that great tactile feel.wink.gif

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post #4 of 153 Old 09-23-2013, 10:32 PM
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it's just geometry.

you don't even have to know hornresp to fold a horn. ricci used a program with very detailed calculations, but you probably won't miss anything using this approximation (I think these were his latest numbers).



any way, s1-s5 are cross sectional area. s1 is where the horn path starts. s2 is right in front of the driver. units are sq cm. the "par" values are simply lengths in cm.

for a horn that is 2 feet wide in between the wall panels, that is 61cm approximately, so to calculate the height of the horn at each point along the way simply divide the cross sectional area by 61

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post #5 of 153 Old 09-23-2013, 10:47 PM
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post #6 of 153 Old 09-24-2013, 05:56 AM
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I have been wanting to do something like this for some time now. Only I was thinking something like the format of lilmike's lil wreaker (simple, minimal panels) but with a major dimension of 7'6" or so so that it could be stood up in a corner of a room with 8' ceilings. If I have a spreadsheet showing the flare rates and lengths I think I could do it, but I cant seem to find that information, or maybe I don't know what I am looking at in hornresp.
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post #7 of 153 Old 09-24-2013, 08:12 AM
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"If I have a spreadsheet showing the flare rates and lengths I think I could do it, but I cant seem to find that information, or maybe I don't know what I am looking at in hornresp."

see post #4.

first, pick a depth, let's say it is 2 feet. that is 61 cm.

s1 is 82 cm^2, so the height of the horn at the start is 82/61 = 1.25 cm, which is almost nothing.

s2 is 308 cm^2, so the height of the horn at that point is 308/61 = 5 cm, so the height inside the horn in front of the driver is 5 cm. the distant from s1 to s2 is 23.6 cm.

travelling down the horn it is the same thing.

s3 is 1075 cm^2, so the height of the horn at that point is 1075/61 = 17.6 cm and the distance from s2 to s3 is 487 cm.

s4 is 2118 cm^2, so the height of the horn at that point is 2118/61 = 34.7 cm and the distance from s3 to s4 is 104 cm.

the driver is also in front of s4.

the final length extends to the mouth of the horn.

s5 is 2250 cm^2, so the height of the horn at that point is 2250/61 = 37 cm and the distance from s4 to s5 is 63 cm.

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post #8 of 153 Old 09-24-2013, 08:16 AM
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alternatively, print out the gjallarhorn and cut it into pieces, then just like a puzzle rearrange them into a shape that you like. not every horn will fit into every shape and that is the pain in folding a horn.

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post #9 of 153 Old 09-24-2013, 01:25 PM - Thread Starter
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Hmmm, I am not much for geometry. So, it may sound easier than it is, or at least to me.

I would be willing to make a donation to help that cause if someone can re-fold and post some simulations that would hopefully translate into real world performance.

I am sure others would be willing to donate to the cause as well. Again, I think it is a design that many would use and appreciate.

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post #10 of 153 Old 09-25-2013, 10:52 AM - Thread Starter
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It is just too much wood/money and time to assemble something based on my calculations.
I need plans that I can follow...

That is why I would rather pay someone for their time than waste mine experimenting.

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post #11 of 153 Old 09-25-2013, 11:40 AM
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But, if you refold it, it won't be the Gjallarhorn any more.

The folding of a complex tapped horn is not a trivial undertaking, I know, I've folded a few. It is not impossible though, I managed to figure it out, though I did have a little help along the way. I've tried to share my techniques as I have refined them, there is no magic tapped horn folding machine - at least not one that I have found yet. All my folds are done via trial and error, on an iterative basis. I generally know what I want something to look like, but I rarely get the layout correct on the first try.

Start with a sketch, see if things will fit. As LTD02 pointed out, it is simply a geometry problem. L stands for length, and is presented in centimeters. S is sectional area at that point of the horn, in square centimeters. A spreadsheet will help with the math, and the free version of Sketchup is a perfectly adequate tool for drawing plans.
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post #12 of 153 Old 09-25-2013, 12:03 PM - Thread Starter
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Perhaps , the GJALLARHORN SE or LP or 2.0 or ??biggrin.gif

I hear ya, I just don't think I am capable.
I am stupid, but smart enough to know it. I fully realize and agree that it is not trivial. And if it is not trivial for you, then it is nearly insurmountable for those of us that are mathematically challenged.
I know I would have something screwed up and end or up wasting a boatload of wood.

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post #13 of 153 Old 09-25-2013, 12:50 PM
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there's a fire starting in my heart...reaching a fever pitch, bringing me out the dark...

well, let's not call it a gjallarhorn because we are a LONG way off from that, but would something like this get you rolling in the deep?

30" high x 72" wide" x 24" deep



edit, 6 feet wide not 60", sorry about that!

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post #14 of 153 Old 09-25-2013, 12:55 PM - Thread Starter
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Yes! That would be perfect!

That is exactly what would do the trick! I would like to build two and unload my DTS-10 so I don't have to see that huge box in the corner of my otherwise very appealing room.

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post #15 of 153 Old 09-25-2013, 01:26 PM
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Quote:
Originally Posted by LTD02 View Post

there's a fire starting in my heart...reaching a fever pitch, bringing me out the dark...

well, let's not call it a gjallarhorn because we are a LONG way off from that, but would something like this get you rolling in the deep?

30" high x 60" wide" x 24" deep


Wouldn't that reduce the internal volume slightly?
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post #16 of 153 Old 09-25-2013, 01:54 PM
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ricci ghallerhorn hornresp approximation:





my schlock:











the black area in the fold is unused space...yeah, i just cheated.

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post #17 of 153 Old 09-25-2013, 01:58 PM - Thread Starter
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That is starting to look promising!

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post #18 of 153 Old 09-25-2013, 02:02 PM
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original (black line) vs. my schlock (gray line) rescaled to help provide detail.

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post #19 of 153 Old 09-25-2013, 02:07 PM - Thread Starter
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That's pretty damn close...and a little smoother 20-50!

You mention you cheated with the unused space. I am assuming that this is where things get complicated in trying to pin down the proper fold and maximize the available volume?

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post #20 of 153 Old 09-25-2013, 02:09 PM - Thread Starter
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Quote:
Originally Posted by lukeamdman View Post

Wouldn't that reduce the internal volume slightly?

I would gladly go longer, up to 70" if necessary and if that makes things easier.

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post #21 of 153 Old 09-25-2013, 02:24 PM
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frequency response is pretty much on.

the 60" length is interesting as that is the length of baltic birch ply.

this one could be stood on end too, so not sure if it is a low profile or a tallboy. :-)

i just went through the numbers again and i think it is right. just over an hour from post #13 to post #16...pfa.

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post #22 of 153 Old 09-25-2013, 02:38 PM
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Looks sorta like the LilWrecker...

If L45 is 25 cm and the throat is another 25 cm, that eats up 20", so there is not a lot of room left in that 32" for the panel widths (about 4.5") and the needed horn area (about 14" or so, depends on internal panel widths).
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post #23 of 153 Old 09-25-2013, 02:46 PM
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"If L45 is 25 cm and the throat is another 25 cm, that eats up 20", so there is not a lot of room left in that 32" for the panel widths (about 4.5") and the needed horn area (about 14" or so, depends on internal panel widths)."

i'm not sure what you are saying.

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post #24 of 153 Old 09-25-2013, 05:29 PM - Thread Starter
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Quote:
Originally Posted by lilmike View Post

Looks sorta like the LilWrecker...

If L45 is 25 cm and the throat is another 25 cm, that eats up 20", so there is not a lot of room left in that 32" for the panel widths (about 4.5") and the needed horn area (about 14" or so, depends on internal panel widths).

That is what I had in mind from the beginning, a more potent Lil' Wrecker tat can use the mighty 18s, and maybe a little shorter on the length.

I am not sure on the measurements you referenced.

Now, is there any way to simply the project by eliminating the empty space?

I never bought any 5x5 sheets,but I see the point in the 60" length. We seem to only have 4x8 sheets around here.

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post #25 of 153 Old 09-25-2013, 05:40 PM
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"Now, is there any way to simply the project by eliminating the empty space?"

part of what creates the dead space is that the long bottom section has a much greater expansion rate than the long path before it. it may be possible to design something completely different, but within the rough idea of this design...the answer would be a...no...or i would not have it there. :-)

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post #26 of 153 Old 09-25-2013, 05:41 PM
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i am actually REALLY surprised to have gotten as close in response as we got given how different of a form factor it is.

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post #27 of 153 Old 09-25-2013, 05:48 PM
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it turned out very similar to the lilwrecker! http://www.avsforum.com/t/1451519/lilmikes-lilwrecker

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post #28 of 153 Old 09-25-2013, 05:51 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

"Now, is there any way to simply the project by eliminating the empty space?"

part of what creates the dead space is that the long bottom section has a much greater expansion rate than the long path before it. it may be possible to design something completely different, but within the rough idea of this design...the answer would be a...no...or i would not have it there. :-)


I see, thanks for the clarification and your willingness to share your expertise!
Now, if we can get a guinea pig to load it into Sketchup!

If the design can be finalized into a drawing, I am willing to bet there will be more than a few takers for this design.

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post #29 of 153 Old 09-25-2013, 07:04 PM
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i don't know sketchup, but the drawing is pretty close to scale. i can try to get it as precise as possible if folks are actually going to build it.

the internal depth that i used was 24" by the way.

AH BIG EDIT! it is 2.5 feet by 6.0 feet long, not 60 inches. sorry about that!

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post #30 of 153 Old 09-25-2013, 07:10 PM
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"Wouldn't that reduce the internal volume slightly?"

you are right...i had the dimensions confused and was thinking 60" initially, but it is 6 feet, which is 72" of course.

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