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Template for drilling HDT ovals (Read 5275 times)
2Sounz
Ex Member



Template for drilling HDT ovals
11/03/05 at 00:23:53
 
I am currently building a set of HDTs.  Should be done soon, can't wait !!!  :D


Since many people have been so helpful to me on these forums (thanks very much !) I thought I would add a little bit and contribute something.

For anyone building the HDTs, one task you have to deal with is drilling the oval openings between chambers.  These are well detailed on the instructions from Decware.  However you have to work out how to drill all the 1/2" holes around the oval, I mean how many and where.  To do this task I used my PC to make a drilling template.  For those of you who would like a copy, I am making it available at the following location:

http://home.cogeco.ca/~rsolda/Audio/HDT/Templates/HDT_Oval_Template_2.pdf

You can print this pdf file out (be sure to print it out at 100% scale) and cut out the template rectangle (dotted lines) then simply draw horizontal and vertical lines through the center location of your oval on your work piece and tape the template using the cross hairs to center the position of the template.  I then used a punch to mark the centers of each of the small drill circles on the MDF, removed the template and used the 1/2" spade bit to drill them out.

To ensure that your oval is the right size when it prints, you can measure the rectangle. It should be exactly 8"x6" to be the right dimensions.

Hope it helps you DIY'ers out.  It is a great project to build but sure takes time to do it all.  Wonder what they will sound like?

I hope to post pictures when I am done.

Rick
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brad
Ex Member



Re: Template for drilling HDT ovals
Reply #1 - 11/03/05 at 00:39:28
 
Hey, that's great! thanks. But if it were me, I'd just use the template to draw the oval and then cut it out with a jig saw.  I seriously doubt it will make any difference and it'll be much faster.
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Chris K
Ex Member



Re: Template for drilling HDT ovals
Reply #2 - 11/03/05 at 01:48:56
 
Actually Brad the hole drilling and then "breaking" out the waste part leaving a jagged edge is an "on purpose" design aspect of the HDT. Steve claims it helps diffract waves and create beneficial "turbulances" as the rear wave enters the side chambers.
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Corey
Ex Member



Re: Template for drilling HDT ovals
Reply #3 - 11/03/05 at 03:30:41
 
2S,

I would check with Zygi to confirm the size of the ovals. It has come up on this forum that the size for the ovals on the plans are bigger than the factory built models. My speakers were built the summer of 2004 by Zygi and the oval cut outs are 5 7/8 inches long at the very extreme. Perhaps the factory built units are different now but mine are smaller than the plans.

Take care,

Corey
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brad
Ex Member



Re: Template for drilling HDT ovals
Reply #4 - 11/03/05 at 05:50:59
 
[quote author=Chris K  link=1130981033/0#2 date=1130982536]Actually Brad the hole drilling and then "breaking" out the waste part leaving a jagged edge is an "on purpose" design aspect of the HDT. Steve claims it helps diffract waves and create beneficial "turbulances" as the rear wave enters the side chambers. [/quote]

I have a hard time believing this given the lack of driver excursion with the FE206.  There isn't much air moving here to create "turbulances", at least ones significant enough to create an audible difference.  It's possible, but I just have a hard time believing  ???
Now with a driver like the MKII it's a (little) easier to swallow.
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2Sounz
Ex Member



Re: Template for drilling HDT ovals
Reply #5 - 11/03/05 at 12:26:29
 
Corey,
I will definitely check on the size of the oval with Ziggy.  I will send him an email with the diagram for him to check.
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Zygi
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Re: Template for drilling HDT ovals
Reply #6 - 11/03/05 at 20:40:10
 
2sounz

  I printed @100% on two computers and 2 printers  and the ovel comes out  to be....3 3/4" X 5 5/8" on both. the linews you have drawen need to be close enough together to be able to break the center out after drilling with a good blow from a hammer. What you've show would be a little two far apart to work.


 The line that marks the centers should be 4" X 6"


   Thanks for your help with this, it'll make the build easier for all if we can get it right. I know when I print from my cad program to Adobe writer and then print on both computers its exactly 4" X 6" but it doesn't even work when I e-mail it to myself.

  I guess with your pattern, if someone was to just take and mark new lines to get the 4" X 6" size they needed, then make the same witness marks all the way around they could make it work just fine.  The division of the oval just needs to be divided in to smaller increments.

  Very good idea,


   BobZ.
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Zygi
Ex Member



Re: Template for drilling HDT ovals
Reply #7 - 11/03/05 at 20:48:57
 
Brad,

 Not turbulance that you would think of as a noisey port on a sub, maybe a better term would  be eddys. Instead of putting hair around it, it's more like hair in it, so both sides of the wave see the hairs.

  If that makes sense, let me know.

      BobZ.
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DirtDawg
Ex Member



Re: Template for drilling HDT ovals
Reply #8 - 11/03/05 at 21:18:16
 
[quote author=Zygi  link=1130981033/0#6 date=1131050410]....... I know when I print from my cad program to Adobe writer and then print on both computers its exactly 4" X 6" but it doesn't even work when I e-mail it to myself.

     BobZ. [/quote]
Just for grins guys, have you tried to email a TIFF instead of a .jpg or .pdf. As we all know compression does terrible things to a signal, and images as well.

Brad,
There are 2 types of "turbulence" to consider in a speaker box: the airfoille type when you are dealing with large amounts of air, like at low frequencies and also the "sonic" type like you have to account for at mid frequencies which are complicated by reflections inside the cab. I think the idea is to break up the mids by causing a sonic turbulence.

I'm sure someone will tell me if I'm FOS, but at the level of spl in most pro cabs I have experience with, breaking up mid freqs with turbulence is very important. Grin
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« Last Edit: 11/03/05 at 21:22:17 by DirtDawg »  
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Chris K
Ex Member



Re: Template for drilling HDT ovals
Reply #9 - 11/03/05 at 23:15:20
 
Actually as a raster (pixel) based image a tiff file would be prone to sizing "anomalies" much more than a PDF file. A PDF file is in Adobe "PostScript™" format and is mathmatically correct and is device independent even pertaining to "resolution". It is like (IS) a "vector" graphic and is universal to any platform it is opened on. In other words PDF's should ALWAYS work. IF they don't then the proper version of the  Adobe "read" engine is not installed on your PC.
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DirtDawg
Ex Member



Re: Template for drilling HDT ovals
Reply #10 - 11/03/05 at 23:43:21
 
Chris,

Of course, you are absolutely correct. My thinking, like yours, is that it should be better to use a vector based format, especially a PDF, for any transfer of graphics. What's going on? I've transfered billboard graphics to printers, 3 or 4 on a floppy before, in Adobe and Corel with no losses or color shifts. I know it should work. Grin

BTW, that's across different versions of each with no anomalies.

MOD:
After re-reading the thread, I removed my silly questions, since I misunderstood the problem to be email related, anyway.
Nice try 2Sounz, just .....  uhh ..... fix it and it will be helpful.
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« Last Edit: 11/04/05 at 00:29:16 by DirtDawg »  
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Jason_S
Ex Member



Re: Template for drilling HDT ovals
Reply #11 - 11/03/05 at 23:46:41
 
Doesn't anyone remember the grade school geometry method of drawing an ellipse with two pins and length of string?

The pins should be 4.472" apart and the circle of string should be 10.472" to get a  4 x 6 oval.   I'd probably round to 4 1/2 and 10 1/2 just for ease.

I'm with Brad: draw the line and use the jigsaw.   Smiley
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DirtDawg
Ex Member



Re: Template for drilling HDT ovals
Reply #12 - 11/03/05 at 23:48:46
 
Maybe you have a better jigsaw, than I do. I have an effortless drill.
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Hrappur
Ex Member



Re: Template for drilling HDT ovals
Reply #13 - 11/04/05 at 00:16:43
 
It´s always good to take advice a)from people who havn´t built the damn thing and b)not listen to some one that has. (how many is it zygi, over a 100?)Of course you could cut lots of corners building like not bothering with the pesky routing of the panel connections and using an old carpet for liner, you can also leave the bafle corners and maybe the ultimate just get a cheaper driver than the Fostex, wether you then call it a HDT or a SLO will be a matter of conscience. But if you were restoring a Mercedes 1957 you wouldn´t put an engine from a 1987 Volkswagon inside and call it close enough.
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DirtDawg
Ex Member



Re: Template for drilling HDT ovals
Reply #14 - 11/04/05 at 00:23:14
 
Is there a "Touche" smiley? Tongue  So true, but what's a/an SLO? I don't think I want one.
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