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Old 4th December 2007, 04:27 PM   #1
NED 209 is offline NED 209  Ireland
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Default boombox re-build

hi there, i thought id better start a new thread rather than jacking Saturnus's Boominator thread. im planning on building a replica boombox from wood or some other suitable material. following V-bros advice im going to build one from scratch. this is the model im copying, its basically a pretty simple shape

the big one -

Click the image to open in full size.

ill take off the adornments from the original radio (chrome, stickers etc.) and fix them onto the copy. i intend it looking identical, but want it to sound better. im getting no bass with the plastic.

weight is critical. i cant stress that enough. the whole thing has to be as close to 8kg as i can get it. (i dont have a car!) so the amp32 and 41hz series are a real blessing for me. i bought the killer drivers for this project, 1.5kg and 99db, im in love. - http://www.musicgear4u.com/bass-gui...l10150-neo.html
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Old 4th December 2007, 04:28 PM   #2
NED 209 is offline NED 209  Ireland
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so id like advice, on what type of wood to go for? probably plywood ill go for, im tempted to go as thin as possible, quarter inch, and brace it. but im open to advice or suggestions. the bbx is huge, id say about 36lt.

heres some pics of a previous radio at night, i got all car hi-fi on it, and sanded down the fins on the p-audios for a more dramatic effect

http://i23.tinypic.com/9r36mh.jpg

http://i8.tinypic.com/6z6ckfr.jpg
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Old 4th December 2007, 04:29 PM   #3
NED 209 is offline NED 209  Ireland
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so far ive been advised to go for a minimum 1/2 inch plywood, but given the size of
the radio (33 1/2" wide, 18" tall, 8"deep) it would be to heavy to carry.

also recommended which im currently looking into ->

*Seems that some sort of high tech sandwich material would be best.
Like epoxy and carbon fiber/glass skin with foam or hexagonal cell or balsa core. Not cheap but I'll bet you can get sheets of stuff like that somewhere.. maybe 1/2" thick. Boats and airplanes use it.. Celestion used the stuff with metal skin for the SL6 speakers I believe..

Like here,

http://www.acp-composites.com/acp-lp.htm

or here,

http://www.cstsales.com/fiberglass_sandwich_panel.html


ooooh too pricey*

like the sound of that stuff. had heard balsa was quite brittle.
any other avenues or input appreciated !
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Old 4th December 2007, 08:50 PM   #4
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Here's a view so you can see an example of what I did to reduce weight in mine. I also reduced the centerbrace from it's original 12mm to 8mm, and made cardboard ports instead of the original ones made of wood.
Attached Images
File Type: jpg boominatoriirouting.jpg (27.3 KB, 787 views)
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Old 4th December 2007, 09:19 PM   #5
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You might consider a cheaper sandwich material like Gatorfoam. Not sure if it's available where you are, but I'm guessing it should be--try an art supply store. For how light it is, it's unbelievably strong.

It will be well-suited to larger, flat areas, and not for things like speaker cutouts, Still maybe for the back and some of the sides, it'll save you a bunch of weight compared to any kind of wood product. Gluing is probably going to better with it than mechanical fasteners.

For my boombox, I used fiberglas/carbonfiber/nomex aerospace panel scrap I got on ebay. No lighter than plywood, but you could just about drive a tank over the stiff.

--Buckapound
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Old 4th December 2007, 11:43 PM   #6
NED 209 is offline NED 209  Ireland
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Saturnus nice, ilike it. with a router, yeah? i figure ill have to buy one of them, and a tablesaw. its amazing how much money you can plow into a hobby/passion/obsession

Buckapound, you box looks wicked

Click the image to open in full size.

do yuou have any newer pics of it? ill research the materials you mentioned, thanks
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Old 5th December 2007, 03:12 PM   #7
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Btw, if you want to experiment with aerospace materials, it's relatively easy to make yourself cheap. Yes, ironically, making aerospace materials isn't rocket science.

Basically you need some glassfiber cloth which can be found in any paint shop for around 2 for 10 meters in 1m wide rolls. Some epoxy and polyurethan glue. Some wood and some kitchen oil, eg. olive oil. Something heavy like phone books.

Make some frames to strech out the glassfiber cloth on. Paint the cloth thinly on both sides with epoxy glue. Let it dry and harden.

Soak a wooden work area and a pressure piece of wood which depending on the size of sheets should at least 18mm thinck with olive oil. Place two of the sheet of glassfiber you've made on the work area. Paint these sheets with polyurethan glue mixed with 1/10th of water. Place some spacers in the corners, I'd suggest some matches with the sulphur broken off. Place one sheet over the other with the glued sides facing eachother. Put the pressure peice over the whole thing, and something heavy on top of that. Wait till it dries, and hardens.

That's it. Now cut the glassfiber-aerogel-glassfiber laminate you've just made for less than a 1 per square meter to the sizes you want.

If you want even thicker and stronger pieces, just take two laminate pieces and laminate those.

Simple really. Though it will take a few tries to get it right.
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Old 5th December 2007, 07:32 PM   #8
NED 209 is offline NED 209  Ireland
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sounds interesting. im in my final year of college though and i reckon ill just about get the time for the build. if i had more time id be itching to try it.

the gatorfoam sounds very interesting. Buckapound just how rigid is it, would i get away with half inch sheets?

thought id post up these speakers for anybody interested in making a simple boombox. the first two are pyle car speakers, both are rated at 95db, very high for car speakers. the third was shown to me today, 97db

http://cgi.ebay.com/NEW-PAIR-PYLE-PL...QQcmdZViewItem

http://cgi.ebay.com/NEW-PAIR-PYLE-AU...QQcmdZViewItem

http://cgi.ebay.com/2-New-6-1-2-In-W...QQcmdZViewItem
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Old 5th December 2007, 08:10 PM   #9
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The Gatorfoam is amazingly rigid for how light and cheap it is. I made my boombox prototype out of two layers of plain old Foam-Core, and even that sounded pretty good. If you wanted a little extra strength, you could use two layers of 1/4" Gatorfoam laminated together with urethane caulk, which has great damping properties as a bonus. Two layers means more stuff to cut, but if you do it right, you can stagger the sizes of the sheets (the equivalent of a rabbet joint in woodworking) so the inside panels are smaller than the outside, and then you have this stairstep joint that glues up a lot stronger than just two plain pieces, plus leaves less of the soft foamy middle exposed.

Another material to consider as part of this project is modelmakers styrene (or ABS). You can get it wherever model railroad supplies are sold. It comes in a variety of thicknesses, and would be great for adding little ribs and other details to mimic the original mold of the box you're copying. Also for reinforcing edges and corners. Cuts by scoring w/an X-acto and snapping. Paints well and glues up very strong w/cyanoacrylate (Superglue) or model airplane cement, and should glue well to the Gatorfoam. I also use it for subchassis parts inside, to hold boards, caps, batteries, etc. By gluing together lots of parts and pieces, and drilling, tapping, etc., you really can make the same kind of internal structures that are found in the boxes you're copying. The benefit is that you can put things together very compactly, saving space for the resonant chamber you need for the speakers.

I'll snap some pics of my box to show you the internals in the next day or so. All the amps, caps, etc are on a squarish structure that surrounds the central port and pot.

--Buckapound
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Old 5th December 2007, 10:56 PM   #10
NED 209 is offline NED 209  Ireland
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thats a big one, the resonant chamber. ive never approached anything like this before. i know i can build it, im just not sure about the math. math scares me! ive emailed celestion about the recommended enclosure volume for the woofer. im looking forward to getting this right.
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