182 false floor for sub - box volume

[PinkoCommie]

I've been thinking about this.

I want to build a speaker box the same shape as the boot floor but not very thick. Not stealth, Sub still on show, but flush with the new raised floor.

There seems to have been lots of 172 false floor build because you can recess the sub into the wheel well, but no can do on the 182

Would i be right in saying that the important thing about the sub box is the enclosure volume?

I'm looking at getting a 10 inch infinty. Box volume is 21.24 litres, so being that the boot is about 12cm deep, as long as i have a 50cm*50cm chamber (give or take, after taking into account thickness of box material) then do you reckon this would work.

Will working with the absolute minimum mounting depth for the sub affect the sound? (this sub has a 12.1 cm mounting depth, I'm going for 12.5.)

I'm looking at doing a sealed enclosure.

What sort of material is reccomended to craft the box? MDF? What sort of thickness? 8 to 10mm?

More importantly, has anyone tried this before, couldn't find anything on here, but if anyone has tried and failed, any tips or advice would be greatly recieved.

 

[iimushroomzii]

18mm MDF to make the box, as for Cubic feet im too pissed to work it out, sorry.

 

[PinkoCommie]

18mm? Blimey, that makes it a bit more of a bugger to work with. means the chamber will be shallower and wider.

Oh, I can work out the volumes I need and the dimensions the box would need to be given the minimal depth I'm working with.

the question was more along the lines of would a shallow but wide sealed enclosure sound markedly different from a more cubic one?

Also, if I was to do this, would there be much of a difference in sound between the to following designs (assuming that that is the shape of the inside of the encloses)

Obviously box b has less sharp internal corners, is this better? (if the internal volume is more of a pig to work out )

I'm wanting tight bass, as I usually listen to techno, so it's fast and punchy, and not particularly "boomy"

Current working out is about 30cm deep, 80cm wide and 12cm tall for the main body, and 30cm * 30cm * 4cm for the top bit (so total height in the middle 16cm). With the size of the boot that gives me plenty of working space.

If I could find a sub with a 10cm mounting depth I could probably have a flat boot out of it.

 

[wallop]

Have you considered an 'inverted' sub???

The two designs would sound the same, only consideration with regards internal shape is in relation to air movement around any ports fitted, no ports, no worries....

The only consideration with regards mounting depth is that of cooling, if there is a vent in the centre of the magnate then you should aim for at least a 25mm clearance to allow good air movement....No vent hole, no worries....

With regards MDF thickness, as recommended I would go with 18mm also....any less & output quality would be affected, (MDF resonates & cancels out certain frequencies which results in unnatural sounding bass)....You could use thinner material as long as inner bracing is used to support the larger panels....

I would also suggest 'wadding' the enclosure, this will improve the overall results....

 

[PinkoCommie]

What do you mean by an "inverted" sub?

 

[AlexG]

What do you mean by an "inverted" sub?

http://images.google.co.uk/images?s...B202&q=inverted sub&um=1&ie=UTF-8&sa=N&tab=wi

 

[PinkoCommie]

Ahhh.

I get ya.

I'll wait until I get the sub to see what the back of it looks like before I make that decision

But as my whole idea is to have minimum disruption of my boot and no protusions other than a "hump" I'll probably give it a miss.

I've drawn up some basic plans, and I'm going to have a whole frame for the amp, with proper connecors, then have the boot "floor" as a seperate piece with a cutout for the sub hump that fits over the top and clips onto the frame. In that way I can have a smooth floor, yet still get easy access to the insides.

When it comes to amp cooling, as I'm not going very big, only 3 or 400W, would air gap around the amp be sufficent, or might it be worth me putting some venting in? The cavity will be 10cm deep, so that plenty of air space above the amp(s).

At some point I'll shove the plans up here to see what people think.

 

[Struggler]

definatly put some kind of cooling for the amp,

if you go ahead with this plan, where are you going to hide the amp??

 

[AlexG]

Ahhh.

I'll wait until I get the sub to see what the back of it looks like before I make that decision

You cant just mount the sub the other way. The sub has to be made to be inverted. Are they called free-air subs?

 

[MT AUDIO]

www.rockfordfosgate.co.uk has some great how to's on working out cubic volume,etc

matt

 

[Hutchie]

go for a level floor like mine, think its 182 relivent as i have no spare wheel well either (lpg tank)


boot build mk1

then i redesigned it
put 8" sub in mdf box with baffle inside and port up against rear seats

hole cut out as to not muffle sound

then a shot to show how it sits level

waited a week or two and got delivery of peferated steel

and i like it

and although its just a 8" sub its fecking punchy!!!!!

hope this helps

hutchie

 

[PinkoCommie]

definatly put some kind of cooling for the amp,

if you go ahead with this plan, where are you going to hide the amp??

It's all going to be hidden under the false floor. By my current calculations the sub box will only take up about the centre 1/3rd of it, so that gives me plenty of space on either side for hiding wiring and amps.

Anyone know any halfway decent free CAD software?

 

[wallop]

You cant just mount the sub the other way. The sub has to be made to be inverted. Are they called free-air subs?

You can mount any sub 'inverted' mate....

'Free Air' or 'Infinite Baffle', is mounting on a 'Baffle' with no enclosure as such on each side of the sub, so if you mount a sub in the rear shelf of a saloon or hatchback for example, then that would be considered 'Free Air' or 'Infinite Baffle' because the large volume of air in the cabin or boot area won't have any damping effect on the cones movement....

If going 'Infinite Baffle' then you will require a sub designed to be run in this manner, (when done correctly they sound fantastic)....

Simply mounting 'Inverted' means the sub is 180degrees out of phase with all the other speakers in the system, (sub fires into enclosure whilst all other speakers fire outwards), to combat this you simply switch the 'phase' on the amp, (if the amp supports this), or reverse the polarity of the sub, (+ve becomes -ve & -ve becomes +ve).....

 

[PinkoCommie]

go for a level floor like mine, think its 182 relivent as i have no spare wheel well either (lpg tank)


boot build mk1


and although its just a 8" sub its fecking punchy!!!!!

hope this helps

hutchie

Nice.

I suppose I could go for a pair of 8 inch subs which have a much lower mounting depth. Then I get a flat floor.

I'll have to take a look and see what is available.

Looks good by the way

 

[PinkoCommie]

You can mount any sub 'inverted' mate....

'Free Air' or 'Infinite Baffle', is mounting on a 'Baffle' with no enclosure as such on each side of the sub, so if you mount a sub in the rear shelf of a saloon or hatchback for example, then that would be considered 'Free Air' or 'Infinite Baffle' because the large volume of air in the cabin or boot area won't have any damping effect on the cones movement....

If going 'Infinite Baffle' then you will require a sub designed to be run in this manner, (when done correctly they sound fantastic)....

Simply mounting 'Inverted' means the sub is 180degrees out of phase with all the other speakers in the system, (sub fires into enclosure whilst all other speakers fire outwards), to combat this you simply switch the 'phase' on the amp, (if the amp supports this), or reverse the polarity of the sub, (+ve becomes -ve & -ve becomes +ve).....

Is the any advantage to doing it other than looks or cooling?

 

[wallop]

I assume your asking with regards an 'Inverted' sub....

Advantages;
1, No sub displacement, (allows physically smaller enclosures)...
2, Zero mounting depth, (allows for very shallow enclosures)...

Disadvantages;
1, Possible motor noise, (depends on sub used)...
2, Possible chuffing noise from vented pole piece, (depends on sub used)...

 

[AlexG]

You can mount any sub 'inverted' mate....

'Free Air' or 'Infinite Baffle', is mounting on a 'Baffle' with no enclosure as such on each side of the sub, so if you mount a sub in the rear shelf of a saloon or hatchback for example, then that would be considered 'Free Air' or 'Infinite Baffle' because the large volume of air in the cabin or boot area won't have any damping effect on the cones movement....

If going 'Infinite Baffle' then you will require a sub designed to be run in this manner, (when done correctly they sound fantastic)....

Simply mounting 'Inverted' means the sub is 180degrees out of phase with all the other speakers in the system, (sub fires into enclosure whilst all other speakers fire outwards), to combat this you simply switch the 'phase' on the amp, (if the amp supports this), or reverse the polarity of the sub, (+ve becomes -ve & -ve becomes +ve).....

I didnt know that. Cheers mate.