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Old 14th June 2004, 09:42 PM   #1
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Default Fostex Enclosure

OK-- this is a really dumb one, but its a chance for someone to help a moron in need and openly ridicule him at the same time.

Today, I have been cutting wood for the Fostex 103E cabinets. Since the measurements are in millimeters and we in the USA still cling to the Imperial measurement system, I made all of my measurements in millimeters as well to avoid measurement issues when converting from metric to Ye Olde English.

Here's the problem: the cabinets call for 15mm thick wood and, of course, I only have 3/4", which roughly translates into 19.05mm so... TOO THICK!!

OK, Kofi, this should be no problem, right? All you have to do is add 4.05mm (well, 4mm) to all the thickness measurements and ensure that the inner dimensions stay the same and you're home, right?!?

If I try this, I won't be able to get the internal dimensions to remain the same since some of the wood is laying flat and the thicknesses will increase the size of the box pretty significantly. Also, for me (with pencil and paper) its REALLY, REALLY complicated.

So, I'm a dumbass and here are my dumbass questions:

Is there an easier way to get to the correct dimensions using 3/4" MDF? Does it matter more if the dimensions are proportionally correct (i.e., as long as the inner workings are the same size IN RELATION TO one another, their actual size does not matter) or must they be exactly correct?

I'm thinking one of you has some really cool software that can do this conversion like zzzzzzzzzzzzzzzzzzzing! Please say that's true.

Please help. Please. For the sake of my marriage.

Kofi
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Old 14th June 2004, 09:59 PM   #2
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In my box building experience (which has been riddled with error) I've found that to get it right requires drawing out everything and making a cut list. Don't feel stupid. I know cabinet makers with decades of experience that can't build a simple six sided box without a detailed drawing and cut list.
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Old 14th June 2004, 10:09 PM   #3
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Thanks. I appreciate the encouragement.

I've gotten a few of these RS 1170 drivers and I wanted to try my hand at a variety of enclosures. Dave (Planet 10) was kind enough to clarify the pipe on your website, so I'll be buidling that shortly as well.

Do you think I should keep the dimensions proportional or exact when accommodating the 3/4" MDF?

Kofi
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Old 14th June 2004, 10:26 PM   #4
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Try to stay as close as possible to the internal dimensions described. It isn't a problem if you're off a little bit. The way those Fostex plans are it would be best to redraw them with the front and side plans then make your cut list. I don't know of an easier way to do it. The problem is when you change one measurement it affects all the others. You could always switch to 1/2" birch or appleply.
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Old 14th June 2004, 10:49 PM   #5
sreten is offline sreten  United Kingdom
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Well width wise its as least not an issue.

Side on on its a 8 x 10 block puzzle with 32mm needed
adding to depth and 40mm needed adding to hieght.

If you define each vertical point and horizontal point as part
of this 8x10 puzzle its fairly easy to work out the new sizes,
assuming 4mm for each block crossed.

Of course getting it wrong will be extremely frustrating,
so check and check again you've worked it out right.

sreten.
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Old 14th June 2004, 11:00 PM   #6
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4mm out! thats nothing! you can fill the extra air space with some wadding, i always build the boxes bigger just incase they dont sound right, you can always take fill away but you cant add air space ones its made, unless you know what a tardise is?
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Old 14th June 2004, 11:13 PM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Paradise_Ice
4mm out! thats nothing! you can fill the extra air space with some wadding, i always build the boxes bigger just incase they dont sound right, you can always take fill away but you cant add air space ones its made, unless you know what a tardise is?
I agree 4mm is nothing for one panel but is this case following
the cutting layout for 15mm panels will cause some serious grief.

For example the pointless multilayered mid baffle will be 16mm
out and the section referenced to the rear panel a further 8mm.

24mm out in a tapered horn is nowhere near "nothing".

(not that I think its good tapered horn design, it isn't)

sreten.
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Old 15th June 2004, 12:03 AM   #8
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Quote:
Try to stay as close as possible to the internal dimensions described. It isn't a problem if you're off a little bit.
Yeah... I'll actually wind up off a little bit, but its good to know its a livaeble situation.

Quote:
Side on on its a 8 x 10 block puzzle with 32mm needed adding to depth and 40mm needed adding to hieght.
That's what I camp up with too. Thank God.

Quote:
Of course getting it wrong will be extremely frustrating
I will get it wrong and it will be frustrating when it happens. Fortunately, there's always beer.

Quote:
I agree 4mm is nothing for one panel but is this case following the cutting layout for 15mm panels will cause some serious grief.
Yep. For evey horizonal panel I cross vertically and vice versa, I'll be 4mm off. It would just get worse and worse. Just like life under the Bush administration.

Well, at least you have all confirmed my worst fears. Looks like I'll be calculating and recalculating for a while to get this right. OK, maybe tonight I drink. Tomorrow I calculate.

V-A-C-A-T-I-O-N!!!

Kofi
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Old 15th June 2004, 01:23 AM   #9
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Not sure how much of a shop you have, but I would save the frustration on converting this into 3/4 thickness and opt out for some 5/8 MDF (or better 15mm), Well, actually I would use solid stock and plane it down to 15mm since we have a planer in the shop that would do it, that and I ABORE MDF, its the nasiest stuff i've worked with in 17 years as a carpenter. But finding some sort of ply or MDF matieral of the right thickness might save you a huge headache in the long run.

However, if i were to build this from 3/4, I would scale it up (or down to be precise) on paper and refigure the whole thing for the thickness of the stock I was using. Not an easy task, but not an overly complicated one. i would also approach it from the perspective of looking at each internal 'run' in the horn being a specific size and dimension, reconfiguring the layout so these internal dimensions remained the same. Making a cut list from this would probably be helpful, but I would just note the new size of every piece on the new scaled drawing and cut from that. But, that is just the way that I work. With the way that this horn is constructed you wouldn't really have to mess with the width, only the depth and the height to accomidate the different thickness of the stock.

You might check some of your local lumber yards (ones that supply material for higher end homes) or some of the woodwork speciality stores like WoodCrafters as they might be able to get you MDF or Baltic Birch Ply in 15mm. I actually some some half sheets at a local Mom and Pop woodworking store around the cormer from me.

Good Luck and keep us posted.

-Dozuki
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Old 15th June 2004, 02:06 AM   #10
BrianGT is offline BrianGT  United States
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Default Re: Fostex Enclosure

Quote:
Originally posted by Kofi Annan
OK-- this is a really dumb one, but its a chance for someone to help a moron in need and openly ridicule him at the same time.

Today, I have been cutting wood for the Fostex 103E cabinets. Since the measurements are in millimeters and we in the USA still cling to the Imperial measurement system, I made all of my measurements in millimeters as well to avoid measurement issues when converting from metric to Ye Olde English.

Here's the problem: the cabinets call for 15mm thick wood and, of course, I only have 3/4", which roughly translates into 19.05mm so... TOO THICK!!

OK, Kofi, this should be no problem, right? All you have to do is add 4.05mm (well, 4mm) to all the thickness measurements and ensure that the inner dimensions stay the same and you're home, right?!?

If I try this, I won't be able to get the internal dimensions to remain the same since some of the wood is laying flat and the thicknesses will increase the size of the box pretty significantly. Also, for me (with pencil and paper) its REALLY, REALLY complicated.

So, I'm a dumbass and here are my dumbass questions:

Is there an easier way to get to the correct dimensions using 3/4" MDF? Does it matter more if the dimensions are proportionally correct (i.e., as long as the inner workings are the same size IN RELATION TO one another, their actual size does not matter) or must they be exactly correct?

I'm thinking one of you has some really cool software that can do this conversion like zzzzzzzzzzzzzzzzzzzing! Please say that's true.

Please help. Please. For the sake of my marriage.

Kofi
Kofi,

The easiest solution is to just pick up some 5/8" thick mdf. I happen to know a great place that carries it in Atlanta, called Atlanta Wood Products:
http://www.hardwoodweb.com/company/awpc.cfm

I would call ahead to see if they have it in stock if you are able to go there, as it is quite a far distance for you to travel.

When you get in there, they have a price list that you should pick up to see what is going on. I attached a screenshot of the mdf pricing part of the price list from the last time I went there. They also carry about 4 grades of mdf. I bought the top grade last time for my speakers, and it is much better than the home depot stuff. It was called PanFiberExcelPlus, and was $26.88 for a 4'x8' sheet of 3/4" mdf. I am not sure of the grades they have for 5/8"

Good luck with your project. I would just use the 5/8" mdf and you should almost be able to fully follow the plan with some unit conversions and sanity checks.

BTW: I finally bought a house last week, and it is about 4 miles from this place, and I move in on July 15th. Thanks for the advice.

--
Brian
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