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Making R33 Fibreglass Sub Box, Anyone Interested?

loftyfang

By loftyfang,
in Car Audio & Electrical

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loftyfang

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Hi all, I am making a fibreglass sub box to fit in the unused space behind the right hand side boot trim. It is a fibreglass shell with a mdf front. If there is enough interest, I will look at making a mould of it and producing them to order. Let me know if you guys are interested and I will post some pics when I get home next week.

Pics finally, sorry for poor quality pics as they were taken on my mobile. keep in mind front will be carpeted and shell will have black gel coat.

post-36856-1203314954_thumb.jpgpost-36856-1203314994_thumb.jpgpost-10804-1124086364.jpgpost-36856-1203315074_thumb.jpgpost-36856-1203315108_thumb.jpg[

ttachment=144164:Image052.jpg]

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post-36856-1203315139_thumb.jpg

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loftyfang Contributor

loftyfang

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Hi All, I have just got back home so will finish off the box and take some pictures. As far as moving the battery, you may aswell leave it where it is, mount your amp next to it and have your sub on the side of the boot. Will get some pics up as soon as I can and I'll work out a price based on cost of materials and time to make. Please be patient as I still will have to make a mold yet.

loftyfang Contributor

loftyfang

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Hi All,

The first fibreglass shell I made was going to be too difficult to make a mold of, so I've started again. This time I put a lot more effort into the taping of the inside of the boot. It wouldn't have bothered me but for making a mold I needed smoother, straighter lines, so this time I used more cardboard and spent about 5 hours getting it right.

The first gelcoat is going on tonight, so in a few days I should have the original made. Making the fibreglass mold will take a few more days but when that's done I should be able to get a couple done each week.

The MDF front is 16mm and I am fitting a 12 inch sub in mine. The front of the box could fit a larger sub, and there is plenty of depth. My plan was to pre-cut a 10 inch hole, that way people can choose what size sub they want to put in and cut the front to suit. This will also enable me to fibreglass the front on from the inside as well as from outside.

The wire connectors will be hidden in the top of the side facing the front of the car. This way wiring can be neatly concealed behind the boot trim and run to your amp. I have my amp next to the battery.

I have made space between the shell and the panels of the car and will look at either carpeting the front or the whole thing later on, for the boxes made from the mold, I plan to add pigment to the gelcoat so it will look nice carpeted or not.

I will measure the volume of the box when it's done but at this stage it looks like there will be plenty.

Any suggestions or questions, just let me know. I will endeavour to get some pics up as soon as possible.

loftyfang Contributor

loftyfang

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Shell is done, just need to attach mdf front. Will take pics of completed box in car but will not be carpeted as I still need to make the mold. Just so everyone knows and doesn't get antsy, my work keeps me away for extended periods of time and over the next two months I will be home for about 6 days, all of which I will be putting into reproducing these boxes. If I have enough rubber left to make a second mold, this will speed up the process a bit but please be patient.

Cheers

Ben

loftyfang Contributor

loftyfang

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Hi All, Sorry to say the project is on hold for the time being, received a phonecall from work(NAVY) and are heading north on deployment, read between the lines. This means I will not be home for a period of time that I'm not sure of and will attempt to give updates of my return date if possible. Sorry to all who are waiting for these, but these things happen. I will be picking up where I left off when I get back.

Cheers

Ben

mikel Community Regular

mikel

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Can't wait to see it - odd shaped boxes are superior to a normal box as they damp standing waves inside the box - just make it as rigid as possible.

If anyone is interested I have a great spreadsheet for modelling what the response will be like depending on the driver.

You will need to know the volume of this enclosure and key parameters of the driver you'll be using (Fs, Vas and Qtc).

Assuming it's a sealed box a driver with a large excursion is preferable (Xmax should be >8mm), as the cone excursion on a sealed speaker is bigger than a ported speaker.

The very best 12" driver for a sealed woofer I've found to date is the NHT1259 - do a search on the web for the specs and plug them into the spreadsheet. It blows just about anything on the car audio sub woofer market away. Unfortunately the only source I've found is Madisound in the US.

For a sealed box look for woofer drivers with low Fs (say lower than 35Hz), high Qtc (say greater than .4), large Xmax (say greater than 10mm) and reasonable efficiency (pref >90dB for 1W @ 1m) so you don't need a power station to run it.

I also have some simple rules of thumb equations for when a driver is better suited to a ported enclosure than a sealed enclosure

pm me if you'd like the spreadsheet and/or the rules of thumb.

cheers,

Mike

Ionos Community Regular

Ionos

Posted
Posted
Can't wait to see it - odd shaped boxes are superior to a normal box as they damp standing waves inside the box - just make it as rigid as possible.

If anyone is interested I have a great spreadsheet for modelling what the response will be like depending on the driver.

You will need to know the volume of this enclosure and key parameters of the driver you'll be using (Fs, Vas and Qtc).

Assuming it's a sealed box a driver with a large excursion is preferable (Xmax should be >8mm), as the cone excursion on a sealed speaker is bigger than a ported speaker.

The very best 12" driver for a sealed woofer I've found to date is the NHT1259 - do a search on the web for the specs and plug them into the spreadsheet. It blows just about anything on the car audio sub woofer market away. Unfortunately the only source I've found is Madisound in the US.

For a sealed box look for woofer drivers with low Fs (say lower than 35Hz), high Qtc (say greater than .4), large Xmax (say greater than 10mm) and reasonable efficiency (pref >90dB for 1W @ 1m) so you don't need a power station to run it.

I also have some simple rules of thumb equations for when a driver is better suited to a ported enclosure than a sealed enclosure

pm me if you'd like the spreadsheet and/or the rules of thumb.

cheers,

Mike

Mike - so from what you're saying, these Jaycar subs would run alright then?

http://www.jaycar.com.au/productView.asp?I...=&SUBCATID=

I was always anti-sub because I didn't want to lose my boot space, but this method looks good. I might make a project out of this and try to do the same thing.

mikel Community Regular

mikel

Posted
Posted

depends on the box size

a back of the envelope calculation based on my memory of how big the space is in the back of my R33 says I could fit something around the size of 30cm tall x 20cm wide x 20cm deep - this could be way off but gives a volume of 12 litres.

plugging that volume and the specs for the 10" driver from the Jaycar web site into the spreadsheet gives a response of:

post-33161-1203052227_thumb.jpg

The F3 (or 3dB cutoff point) is around 48 Hz, not exactly sub woofer territory but not bad.

The efficiency is ordinary, and you'll need a big amp to drive this speaker. The Jaycar 12 " is 2dB more efficient, which means it would need a bit more than half the power for the same volume (every 3dB more efficiency means you need half the power to make the same volume or SPL)

I'm happy to send the spreadsheet to anyone who wants it - I didn't create it.

I'll need your email address, as I can't upload an excel spreadsheet.

Mike

ps I'm not a car audio guru - my knowledge is all in home audio, but the principles of speaker, amplifier and crossover design remain the same

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