I have just got another sub and i need to make the boxes 1.75cu ft, 3.5cu ft in total. Trying to fit a box in this size and still allowing for access to the spare tyre is going to be tight so i was thinking of inverting the sub to get a little bit extra volume out of the box.

The basket of the sub doesnt look to bad and was wanting some opinions on what you think.

Also if you have any ideas on what i could do that would a great help aswell.

Inverting the sub's are a good idea. Each 12" sub should be an extra 0.07cu/feet per sub.

Another option, is to just go as deep, as high, and as wide as possible with the box.

Final option, is alter you boot floor, so that it hinges from in front of the sub box, so u still have full access.

i've been looking at it for my next install. from my rough calcs u should be able to get abit over 4cft while keeping it back enuf to get to the spare. u just gotta build it to hug the back of the seat. and u have to cut the masonite cover for the spare and put a hinge on it or something.

i've been looking at it for my next install. from my rough calcs u should be able to get abit over 4cft while keeping it back enuf to get to the spare. u just gotta build it to hug the back of the seat. and u have to cut the masonite cover for the spare and put a hinge on it or something.

Getting the sub box up against the seat may seem logical but the way the 3rd gen boot is designed its not easy to do. I am using as much width as i can get which is about 36" and height which is 15.5". At the back of the boot (the seat end) the sides kick out at 7.5" high and about 5-8" from the back of the boot. Therefore i cant use this space without put some complicated curves in the box.

I already have a false floor in my boot where there is a hinge about an inch in front of the sub in the 3rd picture.


Inverting the sub's are a good idea. Each 12" sub should be an extra 0.7cu/feet per sub.

It would be nice if i got that much. I only gain 0.031cu ft but im trying to save as much space as possible.


Another option, is to just go as deep, as high, and as wide as possible with the box.

The box specs that came with the sub where 22" x 15.75" x 15.5". So with 2 it needs to be 44" wide and my boot being 36" i have to find a lot of space. Obviously being depth.

Thanks for the help. If anyone has any other ideas it would be a great help.

fibreglass :)

Enuf said hehe :badgrin:

Tom

Each 12" sub should be an extra 0.7cu/feet per sub.

Every 12" subwoofer is different and it would be a fairly large subwoofer (eg RE MT to get you 0.7cf.

I'd invert it because the rear of the sub looks better anyway. :)

Do the spec sheets not say how much cu/feet the sub take up internally?

ive got both of mine inverted

SPL for the WIN :D

']ive got both of mine inverted

SPL for the WIN :D

sorry for n00b question but does inverting the subs give u more spl but less sq?

i like my sq, but i also like the looks of the inverted sub....also some manufacturers say dont invert the sub? why is that?

Do the spec sheets not say how much cu/feet the sub take up internally?

The subs are mtx thunder 5512 svc, 300wrms. I only gain 0.031cu ft per sub if i invert it but its something. Eg. More bracing without a larger box.

Does inverting them give you a better SPL? Because i thought that it made no difference.


fibreglass

I would love to do it in fibreglass but im trying to keep the cost down and i dont know how to do it.

How does inverting the sub help? Doesn't it just cut your waves up by putting such a big bloody object in the way? I guess thats going to happen bouncing them off your boot anyway. But still. I know they are low freq waves and fairly non-directional but no point in making life harder no?

Inverting the subs makes absolutely no audible difference in sound.

The only thing you need to keep in mind is flipping the polarity of the wiring + = - and - = +

Otherwise the sub will be out of phase with the rest of your system. (sub will be pushing out when mids are pusing in and vice versa.

As long as you take into accoutn the box size you wont have a problem, even if you didnt take it into account its not going to take up that much space.


sorry for n00b question but does inverting the subs give u more spl but less sq?

i like my sq, but i also like the looks of the inverted sub....also some manufacturers say dont invert the sub? why is that?
Possibly because the terminals and tinsel leads arent built tough enough to handle stray objects hitting them.

Also possibly because the front of the sub isnt designed to be mounted against the box (eg no a flat edge on the front of the sub.

peace

Tim

A few things:

Yes, make sure you check polarity! Very important. Dont want them out of phase. But sometimes, dependent on which way you face your subs, you may try inverting your subs polarity to see if it helps.

When using the same box, inverting the subs can have a dramatic effect because you're literally changing the internal volume of the sub box, therefore changin the back pressure on your drivers. This can be good, and it can be bad, depending on the requirements and specs of the subwoofer.

In this case, 97altera is trying to get as much internal volume as possible from limited space, so inverting the subs will be beneficial to give him more internal volume, without comprimising the subwoofer, or their components.

Thanks Onkytonk thats why i'm asking all these question to do with volume while im designing this box.

I originally said that the volume taken up by the sub was 0.031cu ft. This was the Vd figure which i think i have understood in correctly. I now think that the volume of the sub is .53cu ft. Does this sound correct? If it is inverting the subs are probably my best option because trying to another .5 cu ft per box is going to be difficult.

Vd is:

"This parameter is the Peak Diaphragm Displacement Volume — in other words the volume of air the cone will move. It is calculated by multipying Xmax (Voice Coil Overhang of the driver) by Sd (Surface area of the cone). Vd is noted in cc. The highest Vd figure is desirable for a sub-bass transducer."

So, vd is NOT the cu/feet volume of the rear of your subs.

I had a feeling .03 was too little a value. The following site actually suggests that a 12" woofer takes up 0.07 ft^3. Check it out, its pretty handy:
http://www.bcae1.com/spboxnew2.htm

So you should gain 0.14 ft^3 from both ur subs if you invert them. So if you invert your subs, you will need an internal volume of 3.36 ft^3

The measurements you gave were 36" width, and 15.5" height. Depending on the thickness of the wood, here is what depth you will need for a rectangular box:

For 18mm MDF, the depth would have to be 13.4"
For 16mm MDF, the depth would have to be 13.0"

If you are building a dual chamber enclosure, then you have to subtract another 0.073 ft^3 from the whole internal dimension to account for the wood seperating the two sides.

i had an inverted MTX 15" sub that didnt last long, so i personally wouldnt. but i think i got a dud.

Thanks for the site it should help. I've been using the12volt.com but that has a few different things. I was aware what Vd meant i just misunderstood it until i reread it after noticing a significant size difference in my box compared to the manufactures.

I'm using 18mm mdf. 36" is the total length of the box but i am calculating it in individual boxes which are 18.36x15.5x16.

I am also have to take into account a slot port and bracing.

With a slot port how do i work out how long the back peice of the port has to be to tune it to 38Hz?

theres alot to consider when working out slot ports...

Try the webpage... or give me about one week, i'm waiting on sub woofer enclosure software to arrive.

Wouldnt all the sailors in the sub end up walking on the roof if ya did that. :badgrin:




I dunno nothing about doof doof machines, can ya tell?????? lol :D

theres alot to consider when working out slot ports...

Try the webpage... or give me about one week, i'm waiting on sub woofer enclosure software to arrive.

Yeah thanks that would be great. I think I have worked it out but it would be great if I could compare it to the results you get.

Wouldnt all the sailors in the sub end up walking on the roof if ya did that. :badgrin:




I dunno nothing about doof doof machines, can ya tell?????? lol :D


:bowrofl:

Nah, not at all.... :shifty: