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Discussion Starter #1
Hi All,

Sometime in the next 3 weeks I will be making a bass box for my GTV. I intend to install an Alpine SWR-1242D - 12" sub in a sealed cabinet (1 cubic foot volume). The intention is to end up with a flat boot floor (with no spare wheel) and a big fat sub staring up at you, rather like the example in sportsalfa.com's website (thanks for the idea Luke). I'll be using 18mm lightweight MDF (can order 24mm should it be required :wow: )

And now the real reason for the post: As this work is likely to take me half a day to complete, the majority of which is measuring and test fitting, I was wondering if anyone else would be interested in a professionally built sub cabinet for their GTV. I would be more than happy to tailor the enclosure to their sub, or subs, should 1 cubic foot be too modest. Please reply to this post or pm me so I can get a vague idea of numbers.

Just to let you know the boxes will be raw MDF and would require covering to your preference. You may want to place your amp, or amps, on top of the cabinet and carpet around them or wish to carpet the whole box and place your amps on a vanity board. No offence meant but unless I recieve a number of orders (2 or 3) I will only be purchasing the colour and length of carpet I require. If you would like to bring your own carpet then we do have strong laminating glues that could be used without charge.

So far I have estimated the cost at: £135.00 for a sealed box and £155.00 for a ported box, (after begging a very knowledgable friend he has agreed to calculate all dimensions for any and all enclosures (including isobaric, slotted port boxes)).

Cost:
Matterials (half sheet of 18mm MDF + connectors) £35.00
Labour (inc. use of workshop + calculations) £100.00

Additional:
Port and installation (additional calculations) £20.00

Kind regards,


Matt

BTW: I will be posting pictures of the install as and when it is finished if some of the more skeptical audio boffins need evidence.
 

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I want that type of thing, but think ill build it myself for that cost got a mate who does installs for a living he said hed do it 4 £50 uncovered cause ive got the carpet i want to lay on it.

Good luck with youre new venture!!! Post sum pics soon so i can see the finish
 

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Discussion Starter #5
Without a doubt. The recommended enclosure sizes for the sub I'm going to use (Alpine 12" SWR-1242D) is 28.3 litres or 1 cubic foot for a sealed enclosure - this is a common size that most manufacturers recommend. And 56.7 litres or 2 cubic feet for a ported enclosure (port size 102mm diameter X 382mm length). But as these are only recommended sizes a little more science needs to be applied if you want to produce a quality, level response across the lower frequencies.

Try this website for a more concise measurement. It may also lead you in other directions for your box designs: http://www.bcae1.com/spboxnew2.htm

I am now leaning towards an isobaric box which, although being heavy, would sound like the muts.

I bet I sound like a right geek, I really need to grow up. To be honest it's been years since I've owned a car that made me want to apply so much time and effort into improving it (imo). The more I get involved with my Gtv the more I want to push my own limits; be it designing and building a sub cabinet ,fitting the Alfaholics exhuast, or going for the full body respray. Like a little kid I'm now contemplating spending serious money with very little likelihood of seeing any return. And I don't care because the car puts a smile on my face every time I look at it or drive it :rant: .

I think I might be ready for an AA (Alfa Anonymous) meeting.

Anyway Lordpsk, good luck with the design and build of your sub box and sorry about the rant. ;)

All the best,


Matt
 

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I built one of these for my boot based on the design at sportsalfa, I put a 10" MB Quart sub in and I think it's plenty big enough ;)
 

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@ Zegalini - thanks for the web site very helpful to decide wether to port it or not. Ive changed my design now so im gonna have it on a triangular box to one side so i keep the spare wheel just incase (also to keep me dad happy!!!!)
 

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Discussion Starter #8
If you're happy with your sytem Jonno, then that's the perfect result. But the design I am planning will trade off a peak output, at a certain frequency, for level and clear bass reproduction from 12hz to 150-200hz. Normal sub boxes and tuned boxes are like comparing street racers to formula 1 or turning your home stereo up full to hearing a song played on a quality, club sound system (dark rooms and sticky floors not chrome and carpet).

Anyway, the whole system should be finished in a month or so but the box won't take any longer than 3 weeks so should have some step by step pics in the next few weeks.
 

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Discussion Starter #9
Ive changed my design now so im gonna have it on a triangular box to one side so i keep the spare wheel just incase (also to keep me dad happy!!!!)
One idea I toyed with was fibre-glassing a box into the left hand side of the boot. That way you also get to keep the spare wheel. Try searching for bass-box designs in Google, there are so many options for doing the same thing. The only down side to this is that it is very difficult to calculate the volume of the enclosure but it is the most efficient use of the space. You could also spray paint it the same colour as the car body (very Max Power) or just wrap it in Burbery (chav chique).

If you want to continue using your boot, maybe think about mounting your amp or amps behind the rear quarters. Not very convenient but just an idea.

Good luck.


Matt
 

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calculating the volume of your grp shell is easy just fill it up withwater using a 1 litre or similar measuring jug, it will also test for air/water tightness at the same time;)
 

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Discussion Starter #11
just fill it up withwater
Personally I wouldn't put water anywhere near an enclosure - regardless of the material. I've always used sand as it is far safer and much less distructive to most substances.

All that said you could always purposely make the enclosure slightly too big, this would allow you to fine tune the volume by adding little cubes of MDF inside the cabinet. But dont forget to glue the cubes in when you are happy with the output curve, apparently it sounds awful with them rattling around inside, not that I've ever forgotten to do that and broken a sub. :rolleyes:
 

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One idea I toyed with was fibre-glassing a box into the left hand side of the boot. That way you also get to keep the spare wheel. Try searching for bass-box designs in Google, there are so many options for doing the same thing. The only down side to this is that it is very difficult to calculate the volume of the enclosure but it is the most efficient use of the space. You could also spray paint it the same colour as the car body (very Max Power) or just wrap it in Burbery (chav chique).

If you want to continue using your boot, maybe think about mounting your amp or amps behind the rear quarters. Not very convenient but just an idea.

Good luck.


Matt

Fiberglassing aint my thing as i say a bit NOVAish!!!!! if you get what i mean? or as u put it a bit MAX POWER!!!! :lol:

Nah got sum carpet so gonna do in mdf Ill post pics once finish hopefully wont look cheap and tacky!!! To make sure though im in the middle of building a prototype now!!!

Im gonna put the sub on the left and mount the amp on the right atm but might change if i can think of a better way, did think bout mounting the amp in the boot lid?
 

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Discussion Starter #13
did think bout mounting the amp in the boot lid?
The only down side to mounting the amps upside down is that the heat sinks will radiate heat into the amp. Not important if you don't have the stereo up loud for long periods but it could effect the amps rms rating and life expectancy. Saying that, one of the first installs I did incorperated 2 amps; each mounted upside down under the front seats. Sadly in the Gtv there's no chance of finding any space under either seat.

What about the rear quarters? Loads of space behind there - in fact I was thinking of adding a pair of mid-bass or free-air subs in the cavity. The possiblities in a Gtv are endless, God these cars are good. :D
 

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Rear quaters, where bout you mena any pics? Im just gonna replace the set of components in the front door panels nd see wether i could put a 8" sub in the rear ones maybe? or just another set of components. Think the standard ones lack a bit of beef in them!!!!

Yeah but itll look good tho init lol. Maybe even a set of 6x9'S in the boot lid aswell, cause id have to put heavy duty struts on it anyway!
 

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Discussion Starter #15
Rear quaters, where bout you mena any pics?

Either side of the rear seats. Have a look at how much space there is between the inner panel and outside of the car (possibly 10" depth). I still need to remove these myself and investigate.

Im just gonna replace the set of components in the front door panels nd see wether i could put a 8" sub in the rear ones maybe? or just another set of components. Think the standard ones lack a bit of beef in them!!!!

The rears are 16.5cm (6.5"). Most manufacturers produce 3-way components which include 6.5" (16cm to 17cm) mid-bass, 4" (10cm) mids, and tweeters. I am currently toying with the idea of placing a decent 3-way component set into the Gtv. Tweeters and midrange up front and the 16.5cm mid-bass in the shelf. The only downfall I can forsee is that it may be a little too bass heavy towards the rear.

Alternatively you could always amp up the fronts (good set of 2-way components and 50 to 75wrms amp) and use the headunit to power some 6.5" (16.5cm) coaxials in the rear. This is an old trick, and the beauty is you are only using the rears as infill so power and quality is not an issue (15wrms is enough and a cheap set of coaxials) i.e. quality doesn't matter as they will only just be audible.


Yeah but itll look good tho init lol. only if you add some neons bruv, ya get me? Maybe even a set of 6x9'S in the boot lid aswell, cause id have to put heavy duty struts on it anyway!
:)
 

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My brother is actually doing his GTV-V6 at the moment.

He is building a custom enclosure for a JL Audio 10W6 which will sit up on the space to the left of the battery and fire straight into the cabin area. We have moved the main fuses and relays to make room and this gives enough volume for the box size he needs.

Will post up some pics when done.

Also there is very little space behind the quarters as the GTVs have a double skin here, probably helps make the car stiffer I guess.
 

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Discussion Starter #17
Thanks Sudsonic, the info about the rear quarters is very helpful. I won't pin my hopes on installing anything behind there now. Had debated whether to mount the amps behind there or possibly a couple of 8" free-air drivers. Will focus plans on the back shelf providing mid-bass and boot build incorperating the amps.

This week I've been drawing up some plans for a 6th order bandpass design for two 12" JL's or MTX's. But that plan could alter by the end of today :)
 

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Yeah there is only enough space for the soundproofing mat Alfa place behind there, maybe 15-20mm max so forget the quarters.

I would recommend a sealed box if sound quailty is your main criteria, a Bandpass box will give a very peaky ( and loud ) output but wont sound very musical.

Also you mention you are looking at JL or MTX subs, funny enough we were comparing JL Audio w3v3 against the MTX 5500 sub and the JL had a slight edge in output but an astonishing difference in quality so I know what I would use.

Have fun with the medite and saw:)
 

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Discussion Starter #19
I am slowly amassing the ingredience for this audio cocktail. At present it will consist of the Jl Audio 500/1 MonoBlock Amplifier and a JL Audio 12" W6v2 Subwoofer. All placed in their recommended ported enclosure. Simple as that. Now I just have to build it :p

My long weekend just got shorter.

Pics of the testing process coming soon.


Matt
 
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I usually just listen to the engine, gone off sub boxes myself but each to their own. I used to have one in my first car however, but that was only a 1.3 ford escort Mk4 so the engine sounded dire.
 
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