Help with building a sub enclosure

[acarmody]

Hi all, I am looking at building some sub boxes for some 12" L7's. I want to build some boxes to participate in some SPL comps (only for a bit of fun). The kicker manual says that for the maximum bass you need a 3.25ft³ box (these are per sub) and also .77ft³ extra to build the port, so in total I'll need 4.02ft³ per sub and a grand total of 8.04ft³ (230 Litres). Now thats a crap load of enclosure. And that still doesn't take into effect the building matter size and internal bracing.

So i've done some initial calculations and I have discovered that a dual box just won't be able to be lifted into the boot, due to the lip of the boot being considerably less than the metre I need to box to be. So I have decided to use 2 single boxes. But basically each box will be 50cm wide, 38cm tall and 67cm deep.

So is there any problem with having a box that is deeper than wider?

Also I was planning on using metal corner brackets in each of the eight corners and 3"x3" triangle shaped bracing on each joint, so 12 in total. Is this enough bracing?

Also is 3/4" MDF strong enough? The guy at WOW who is very good says that these L7's blow apart pre-fab boxes easy.

Thanks everyone.

[holdenboy]

Alrighty, ive built a fair few enlcosures for SPL and thats a very big box for 2 12s. I would go with a maximum of 6 cubes, minimum of 3. To much box volume and you risk bottoming out the subs (cooking voice coils), too little and its quiet and sounds like sh*t.

Message me with the details of your boot dimensions and i'll do some maths and come up with an ideal SPL orientated enclosure.

3/4" MDF will be OK but 1" is going to be better, basically the thicker the better, but you sacrifice enclosure volume. As far as those braces go, i wouldnt worry about the corner ones. The main sections that will flex will be the middel sections of the panels. If you want bracing threaded rods are the go...but if you use 3/4" to 1" MDF and are using less than 3kw you should be right.

[acarmody]

I know thats big but thats what Kicker says, see attachment.

And my boot is a normal VX. 105cm between boot struts, lowest point is below the middle seat belt bolt 40cm, and the boot is 80cm deep that I can use. But the boot lip is only 80cm across at it smallest point.

And I know that this enclosure is massive but I want the loudest type enclosure I can get because I'm only feeding 1400WRMS into these subs.

[acarmody]

Heres the whole document http://www.kicker.com/sites/default/...aricL72006.pdf

And yeah these are the 2006 model but you can pick these up for dirt now. And all the places i've been to say they are exactly the same just different colour scheme, been the same for 6 years.

[And_ROOS]

As someone looking to build an enclosure in a VT with 2 12" subs ill be keeping a careful eye on this.

Are there any recommendations for the wood to use for a subbox etc etc?

[acarmody]

Depending on the power of the sub(s) 3/4" or 1" MDF is the go. And every enclosure will be different. Have a look at the subs manufactorers specs.

[holdenboy]

Alrighty when i get the time (probably tonight) i'll work one out for you.

Fair enough about the 1400wrms, but still i would go much over 6 cubes, plus you have gotta have room for loading, which means the box should sit between 5-10" from the tailights/rear of boot.

And_ROOS - Do you want it for SPL or just normal music, a properly designed and orientated SPL box wont sound very good with music.....some songs may sound good but in general it will not.

[acarmody]

It doesn't matter how much boot space this SPL box will take, because I only intend it to be in my car when I am going to comps. I'm also going to build some sealed boxes for everyday use (about 1.5 cubic feet for each sub).

But thanks a heap Holdenboy your a champ .

[holdenboy]

OK, well its abit too hot to work at the moment so ive come in and designed an enclosure for you. Just double check those dimensions and make sure theres plenty of room for air to flow around the box and into the car. Its made to sit on the flat part of your boot (where the spare is).

Ive based the dimensions and box volume on using 1" thick MDF, as i dont think you can get 3/4" ? The only MDF i know of is 6/12/16/18/25mm. Basically the thicker the better, as any flex will hurt your score.

Tell me what you think, i would try all three port lengths (should be able to change them easy enough) but i'd say either the 30cm one or maybe the 25cm one, all depends on the car and where the peak is

[And_ROOS]

Alrighty when i get the time (probably tonight) i'll work one out for you.

Fair enough about the 1400wrms, but still i would go much over 6 cubes, plus you have gotta have room for loading, which means the box should sit between 5-10" from the tailights/rear of boot.

And_ROOS - Do you want it for SPL or just normal music, a properly designed and orientated SPL box wont sound very good with music.....some songs may sound good but in general it will not.

Just for music, and to occasionally open the boot to stir my mates who basically have their subs duct taped to the car

[acarmody]

Thanks a heap Holdenboy, your a champion and legend all rolled into one.

[holdenboy]

No worries, here to help.

Do you access to a termlab spl meter?

I say this because its invaluable to test little things that may or may not increase your score. For example i open my glovebox and i gain 0.3db, i know its not much but if you can find 3 or even 4 of these little things then theres atleast a db right there. Things like glovebox, front seat all the forward and tilted all the way forward, sunvisors up or down, back seat up or down and vents open or shut on the dash all are worth a try.
Heres a link from a good friend of mine who was kind enough to write up a tutorial on SPL competitions, worth it to take some notes.....he knows what hes talking about and has tought me 80% of what i know about SPL.

Technical - Beginners Guide to SPL, Competing & Testing - Mobile Electronics Australia

And_ROOS - Yeah i know what you mean....a proper enclosure can make ALL the difference to how much bass output you get. That box i designed is SPL orientated, but if you were to make the port say 35 x 10cm and about the same depth it should play nice and low, which means it'll play most music.

[VQXTC]

Just for the record you can get 3/4 inch mdf also known as 18mm.......

cheers

[acarmody]

I was hoping to get at least one box made up by Friday so that I can go to a competition at Autobarn Capalaba. But my dad said there was no way it would be complete by then. So we have decided to build some sealed enclosures first, these are for everyday use.

Kicker recommends 2 cubic foot filled with 50% stuffing. And yeah I am using 18mm MDF for the sealed enclosures. But I will use 1" fot the ported box.

Do you access to a termlab spl meter?

I wish I did. Maybe WOW down the road has one. Or at least a dedicated car audio store should have one.