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GJALLARHORN Re-Fold ?!?! - Page 5

post #121 of 153
Thread Starter 
I fully plan on proceeding with the build as soon as possible. I just have a lot on my plate at the moment so I am delayed longer than anticipated.
I have not tried to put together a cut sheet for it. That would be helpful for sure.

Yes, you can do it with a circular saw. I have built several horns making freehand cuts with a circular saw. If you take your time you can get reasonably accurate cuts, more so if you clamp a guide board down for the long ones.
PL does wonders in sealing up any minor deviations in panels. Just run a bead down each panel joint for extra insurance.

You can always have the home store pre-cut the largest panels for you to save some time as well.

MDF would be VERY heavy and is more prone to screw blowouts and more easily damaged when moving the cab(s) around.
I would avoid it for such a large enclosure and use plywood.
Edited by jpmst3 - 10/9/13 at 8:18am
post #122 of 153
"I would avoid it for such a large enclosure and use plywood."

+1
post #123 of 153
I've did some math WRT the possibility of using .704 Acura (sp?) ply but then, this made the dimensionality of the thing start to move, including minor volumetric additions. At one point I had calculated a .0035% increase in one area based on just the decreased thickness. That was revealing. The 3/4 sanded ply was $5 a sheet more than the .7 etc. however, in the course of building 2, an extra $50-75 or about 2 or 3% for this ROI in quality, as we like it in the world of DIY, is negligible.
I've begun laying this out in full size and the 3 internal long guides are about 60 inched each. AT 23 & 15/16 wide I can see that just 1 build will need about 6 sheets.
If you 're good with Kreg joinery, you could conceivably join "assorted parts" into some of the larger panels.
I would plan to use 3/4 for the bracing but figure a long enough "windowed" center brace for each panel should suffice .
AT 60 inches per interior panel or so, how much of that length should the brace be?
And reviewing my THTLP instructions, I can see this as even easier with the 3/4 and close quarters placement.
Shopping list so far: 2 speakers, 1 Inuke 6000 and a minidsp 2x4 advanced, balanced.
Any other amp suggestions? Could a Europower 4000 drive this and have the headroom?
BAck to the procedure.
edit: speaker break-in by iST.
Edited by asarose247 - 10/10/13 at 11:04pm
post #124 of 153
all of the long panels are just rips down the middle of a 4x8 (the red blue and yellow, purple are corner pieces). this is a very crude cut strategy. first two are the sides 30" x 72" (green), which waste a lot of wood. well, leave lots for bracing. :-) seems like a 5 sheet build. I think.

post #125 of 153
Nice LTD.

Looks to be a 5 sheet build no matter how you cut it. If it wasn't for that long yellow piece I could see the possibility of getting it down to 4 sheets.
post #126 of 153
need lots of bracing though...so probably not as much waste as it appears.
post #127 of 153
Quote:
Originally Posted by LTD02 View Post

need lots of bracing though...so probably not as much waste as it appears.

What!? You mean to tell me that you didn't include all of the bracing cuts in your cut sheet?

Bit lazy in your 2am posts these days LTD. Gotta live up to that Avatar man!

wink.gif
post #128 of 153
Thread Starter 
Quote:
Originally Posted by asarose247 View Post

Any other amp suggestions? Could a Europower 4000 drive this and have the headroom?

Sure. The EP4000 will give you gobs of output with this design.
post #129 of 153
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

need lots of bracing though...so probably not as much waste as it appears.

+1

The bracing will eat up those scraps in a hurry. Shouldn't be bad at all with 5 sheets per.
post #130 of 153
I've been lurking on this thread and was curious if either the Dayton or SI 18's would work in this horn...if so, I think I'll have the perfect place for this behind my couch.
post #131 of 153
Quote:
Originally Posted by whoiswes View Post

I've been lurking on this thread and was curious if either the Dayton or SI 18's would work in this horn...if so, I think I'll have the perfect place for this behind my couch.

In this horn, no. But, I think LTD02 whipped up a FLH for the SI driver in another thread.
post #132 of 153
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

all of the long panels are just rips down the middle of a 4x8 (the red blue and yellow, purple are corner pieces). this is a very crude cut strategy. first two are the sides 30" x 72" (green), which waste a lot of wood. well, leave lots for bracing. :-) seems like a 5 sheet build. I think.


Thanks for posting this John! Another bonus bit of info to help with build strategy.

I can't wait to get started.
post #133 of 153
just a back of the envelope scratch to get some sense of what would be required...no biggie.

"I've been lurking on this thread and was curious if either the Dayton or SI 18's would work in this horn...if so, I think I'll have the perfect place for this behind my couch."

a front loaded horn would be better for those drivers. I forget if lilmike's f20 could work with one of those drivers. maybe we should check on that. we threw together a plan for a GIANT horn called submaximus, but that isn't what you are looking for...
post #134 of 153
a VERY quick check suggests that the Dayton may actually work in something like the f20 punched out wide enough to fit the driver. have a look at that one and see if something like that might work if we modify it a little. or...we can design a whole new one. nothing better to do. :-(
post #135 of 153
Thread Starter 
I am inching closer!

It looks like I have my DTS-10 tentatively sold.

So, now I just need to decide on drivers.eek.gif

I love the LMS-5400, but it is hard to justify almost double the price and only 10% more performance. And in a horn I am not sure that the 10% isn't more like 5% or less.

Decisions....mad.gif
post #136 of 153
Thread Starter 
OK, DTS-10 is officially gone and in the HT of its new owner. I sure do miss her!

Question for the horn buffs; is there any guide on how to size the reflectors and does it matter?

post #137 of 153
i would take a centerline down the horn path. from there don't go over about 60% or so from the opposing wall or you will begin to choke off the corner.

if a compass is placed on the inside corner and a circle drawn, you don't want to be inside that circle, more or less, or the horn will be a little choked off.
post #138 of 153
Quote:
Originally Posted by LTD02 View Post

from there don't go over about 60% or so from the opposing wall or you will begin to choke off the corner.
There is no choke off, the wave adheres to Bernoulli's Principle.
post #139 of 153
Thread Starter 
OK, so, would there be a negative effect if there is a small deviation from what "looks" right?
post #140 of 153
Quote:
Originally Posted by jpmst3 View Post

OK, so, would there be a negative effect if there is a small deviation from what "looks" right?
You want to leave a minimum exposure of flat surface that can reflect the wave back, possibly resulting in cancellations. But if the bend to bend distance is less than 1/4 wavelength within the passband there wouldn't be cancellations anyway, so you wouldn't need them at all in that case from a response standpoint, though you might still want them for structural stability.
post #141 of 153
"There is no choke off, the wave adheres to Bernoulli's Principle."

why confuse the matter?
post #142 of 153
"You want to leave a minimum exposure of flat surface that can reflect the wave back, possibly resulting in cancellations. But if the bend to bend distance is less than 1/4 wavelength within the passband there wouldn't be cancellations anyway, so you wouldn't need them at all in that case from a response standpoint, though you might still want them for structural stability."

here is a horn with no deflectors. 1625mm long. according to what you say, there should be a cancellation where 1625mm is 1/4 of a wavelength. that corresponds to a 6.5 meter long wave, which is 52hz.



measured response:


where is the cancellation that you are talking about?

http://www.cowanaudio.com/th.html
post #143 of 153
Thread Starter 
OK, now I am confused.

Are we saying they are totally unnecessary? But, they can be added to give extra rigidity anyway.
post #144 of 153
Quote:
Originally Posted by jpmst3 View Post

Are we saying they are totally unnecessary?
They are with bend to bend paths of less than 1/4 wavelength, in a sub that is. At shorter wavelengths they're always necessary, though above roughly 500Hz flat reflectors become less effective, and rounded bends should be used.
Quote:
But, they can be added to give extra rigidity anyway.
Yes, so if in doubt use them, they can't hurt, and they reduce the area of large panels, which need to be braced one way or another.
post #145 of 153
Thread Starter 
Gotcha, thanks for the clarification.smile.gif
post #146 of 153
I see that the op is still exploring other possibilities in another thread,
however, I myself am still unclear about dimensioning the inside corner "reflective"/ structural braces.
As I read it, None are really needed from the actual physics/acoustic principle point of view.
Are there any recommendations for reasonably effective/realistic actual sizes, should one opt to include them?
I ask this because I see this build as very easy using the Kreg system.
Spacing the screws a "bit closer " together with usage of PL should solve any structural strength issues. (Pencil it out and do extensive " visualizing" before even cutting a board - like an einsteinium " gedanken experiment"
Or from instructions in other builds, do the whole thing in your head unitl you can do the whole thing in your head
Of course, the internal longitudinal bracing. well "vented" 3/4 ply is a given, and for the given width, 2 per fold should(?) suffice . . .
Could the braces be segmented? that is 3 6 " braces in one corner and may 2 8' in the next corner with an eye to applying some lateral symmetry/spacing between braces and the sides.... just askin!

And an exploratory related question:

The announcement of the 18" ultimax by PE

I tried comparing its available (seeming abbreviated) specs with those (very complete) specs of the uxl recommended for this build and I just don't have the chops WRT to determining driver suitability..
Constructive (pun intended) comment/guidance appreciated.

thank you
post #147 of 153
Thread Starter 
Yes, before I make the dust fly I decided to revisit the space where the next bass solution will live.
I am still 90% leaning toward the LOWARHORN, but wanted to make sure before I spend $250 on wood per cabinet.

I would say just guesstimate the size that makes sense based on the dimensions in the diagram.

Braces can be in any form that you desire to do. Just make sure the internal panels have the majority of the center braced. If you want to use multiple pieces, so be it.
There should be enough scraps to make plenty of bracing.

I would stick with the UXL and LMS for this build.
Edited by jpmst3 - 11/19/13 at 2:43pm
post #148 of 153
"I would say just guesstimate the size that makes sense based on the dimensions in the diagram."

+1 there are some measurements that you want to try to get dead on, such as the spacing of the panel directly in front of the driver, but there are other measurements that will have little effect. if the corner deflectors are a little small, no problem. i don't have enough understanding of fluid dynamics to model the differences. they may not even be necessary, but i still suggest putting them in there.
post #149 of 153
Thanks for the timely KISS advice.
post #150 of 153
There is now a date up for the LMS to be expected back in stock. 1/15/2014 not much longer now smile.gif
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