False Floor and inverted mounting

[smokeyjoe03]

Right so I have a 5 door punto and we like to go camping, A LOT.
However I also like my ICE but as you know adding ICE to the car takes up space and can be a hastle to remove.

So I have thought about making a false floor (putting my sub and amp on a board with a connector block)

Also I want to mount my sub arse out or inverted if you like From what i have read the only trick to inverting a sub is reversing the polarity by wiring it back-to-front. Is this all there is too it? That and making sure the speaker has enough space?

Which brings me on to my next question, I know I will need a sealed space the same volume as my current box but does it matter how I achieve this volume?
SEE BELOW?

 

[Eklipze3k]

Only thing I have to add to this - as I don't know for sure about "free airing" a standard sub - is that whoever told you to invert the polarities is a numpty. If you connect the positive and negative terminals backwards on a battery it plain won't work, regardless whether it's upside down or inside out. Same applies here - red to red, black to black - always!

 

[smokeyjoe03]

Only thing I have to add to this - as I don't know for sure about "free airing" a standard sub - is that whoever told you to invert the polarities is a numpty. If you connect the positive and negative terminals backwards on a battery it plain won't work, regardless whether it's upside down or inside out. Same applies here - red to red, black to black - always!

Been reading a few other (less educated) ICE forums and noticed it said it on there, havn't seen it mentioned anywhere else so I did start wondering. thanks for clearing it up.

The other thing I have seen mentiond a lot is "Motor Noise" I take it this is vibrations from the magnet? I am new to all this so bear with me please.

 

[Eklipze3k]

Motor noise is something my brother and I both experienced, the source I'm not 100% sure of and I'll probably get slated for my solution, but instead of earthing to the chassis we ran the earth cable back to the battery and it stopped.

 

[chaos]

Only thing I have to add to this - as I don't know for sure about "free airing" a standard sub - is that whoever told you to invert the polarities is a numpty. If you connect the positive and negative terminals backwards on a battery it plain won't work, regardless whether it's upside down or inside out. Same applies here - red to red, black to black - always!

Wrong type of inversion. It's the speaker polarity you would want to change NOT the power polarity. Basically you are changing the phase of the sub. It is also not a hard and fast rule.

 

[smokeyjoe03]

Wrong type of inversion. It's the speaker polarity you would want to change NOT the power polarity. Basically you are changing the phase of the sub. It is also not a hard and fast rule.

So if I do want it mounted inversed I don't have to swap the + and - wires over from the amp? Its just recomended?

Also what about my 1st question?

 

[volxstu]

Shape of airspace doesnt really make any difference in short.
When inverting a sub (i presume you are not having it free air but the front of the woofer is firing inside the enclosure) usually you need to swap the Phase so it it pushing and pulling at the right time so you dont get bass lag or early hitting.
But as has been said this is not set in stone but you will be able to tell by swapping the polarities over and listening to the difference.
Speakers dont really have a given Phase they will work both ways, for example some speakers if you switch the Phase will try to produce more bass a well set up quality speaker will like this a cheaper and badly setup speaker may just distort.
I actually have my left mid woofer out of phase to even out the sound stage for the driver (of the car not the speaker lol). Im not sure if it is related but i am currently having some problems with that particular speaker and it requires taking the speaker and running it off Axis (changing phase) to kick start it back too life. This is also not recommended to do if you have speakers that you like.

 

[smokeyjoe03]

Just took my sub apart to look at the speaker itself. Looks ****e tbh so I think i'm gonna mount it back the way it was (i.e. in a box). However at the minute its in a huge ported box thats finished in some weird plastic.

So my plan is something simple like this:


Except that the depth will be 500mm not 400mm. This will make the volume of the box 1.3 cubic foot. Thats what the current box is, so it should work properly. The sub will be facing the amp.

So as far as I can see I need MDF for the base and box? Some decent mastik type stuff for sealing? And some carpet to cover it all?

The base will be hollow underneath to allow me to run the wires under from the sub to the amp.

Also I want to add a connector block to the corner of the base so I can pull out the base without having to take the wires out of the amp.

Can anyone see any problems with this design?

 

[smokeyjoe03]

Ok so I have the materials and time, gotta have some minor surgery soon and can't work so I'll have some spare time......

I have given up on the inverted mounting, the back end of the sub looks crap and I can't be bothered to buy a cage or whatever. Its just gonne be as above: A sub in a box, a mounted amp with a kinda cover over it (probably drilled perspex) so I can still use the bootspace. And mount the lot on a false floor for easy removal.

The only problem is making the box, I understand about volume etc.....however I have hit a snag. The sub was origionally is the following box :



As you can see it is ported, the whole right hand side is a port. Now my new box will be sealed. So when I create my new box do I work out the current volume (by measuring the outside of the box) which would include the port?
Or do I measure the inside of the box and exclude the right hand side where the port is?

So the outside of the box measures 435mm across (inc the port)
and the inside measures 340mm across (exc the port)

Which measurement do I use?

 

[volxstu]

Can you not find the manual for the sub they are normally online somewhere. I would say that you will need around 1.5-1.7cu ft for a 12" sub. Will that box not just fit in the spare wheel well it actually looks quite well made and it looks like its tuned to around 35hz so the sealed box will sound very very different.

Use this to work out your air space.
http://www.the12volt.com/caraudio/boxcalcs.asp#rec

 

[smokeyjoe03]

Can you not find the manual for the sub they are normally online somewhere. I would say that you will need around 1.5-1.7cu ft for a 12" sub. Will that box not just fit in the spare wheel well it actually looks quite well made and it looks like its tuned to around 35hz so the sealed box will sound very very different.

Use this to work out your air space.
http://www.the12volt.com/caraudio/boxcalcs.asp#rec

Its an old sub 2nd hand from a mate. No stamps or numbers anywhere on the enclosure or driver itself.


Plus I want my spare wheel still

 

[smokeyjoe03]

Gave up on the whole inverted mounting and stuck to the origional drawing.

Here are some WIP pictures of the enclosure under construction.....





So I came out of hospital yesterday and me being me couldn't stand lying around doing nothing so I was up early this morning and this is what I got so far......





All I need now is a car to put it in. It was designed for my 1.2 Xreg 8v But i'm getting a slight upgrade on Thursday. A 53reg 1.2 16v Active Sport Hopefully it will fit straight in, if not I can cut it down a bit.

I have tested the enclosure before it was carpeted and it doesn't leak anywhere and sounds a lot deeper than the old one, And a lot less BOOMY, due to there being no port.

Quite pleased for my 1st attempt. Just need to sort out the connections as all the yellow electrical tape looks rather unsightly.

(and yes I know its Mutant equipment, I have heard all the flaming before so please, there is no need to go there.....)

 

[volxstu]

Na thats a good little build as long as the car has the same no of doors it should fit fine.

 

[smokeyjoe03]

Na thats a good little build as long as the car has the same no of doors it should fit fine.

Erm going from a 5 door 8v to a 3dr active sport, why would that make a difference?

Surely the internal space of the car would be the same?