Sub Box Design / Help

[szmidi 10+ year member]

Hi all,

I'm looking at rebuilding my sub box. My reasons behind this are to 1. hopefully cut some weight 2. cleaner look / moulded fit 3.make it more accessible (even removable)

I have a 1991 Honda CRX. I've got 2 x Soundstream PCW-12 (single voice coils) being run by 2 x Sony XM1502 amps bridged, one amp per sub. I've also got a smaller amp for the front component speakers to squeeze in.

The specs for the subs are in the attached picture. The dimensions I have to work with are about a 90cm width, 40cm depth. There is a sloped front to the boot portion so its about 50cm lenth on top and 70ish on the bottom.

I'll start with a few basic questions and get more into it as it all comes together. Firstly, it recommends 2 sq ft for the one sub. Is two subs just a straight double (4 sq ft) or does it get smaller with each sub added?? How do I work out the space I need without just making two seperate 2 sq ft enclosures??

Next, to cut weight I would like to use fibreglass for the enclosure, just keeping MDF for the supporting pieces. Will this effect anything really? I've only ever worked with full MDF boxes but the weight is a bummer.

I'm also using a program called WinISD to help with this. My subs are not in their database so I have to add them myself. What are the sub specifications abbreviated as 'Z' and 'le'??

I'll leave it at that for now. Thanks for the help guys.

Click to read more...

 

[The_Grimy_One 10+ year member]

Well I am no expert, so I cannot answer all your questions...

But yes if each sub has a recommended 2 cubes, then they together will need 4 cubes, which is more than likely after all displacements (i.e. port area, sub displacement, and any bracing). You can put them in a shared chamber ported box, which is what I assume the recommended 2 cubes each is for. To save even more room, you may want to consider a sealed box, not sure how those subs sound sealed. Fiber glassing will save some weight, but if you are still going to use MDF, its not gonna get you quite where you want. I would suggest either building a box out of BIRCH, or using birch as a skeleton for the fiberglass box. Birch is much lighter and can be just as strong.

 

[disturbed471985 5,000+ posts]

Well I am no expert, so I cannot answer all your questions...But yes if each sub has a recommended 2 cubes, then they together will need 4 cubes, which is more than likely after all displacements (i.e. port area, sub displacement, and any bracing). You can put them in a shared chamber ported box, which is what I assume the recommended 2 cubes each is for. To save even more room, you may want to consider a sealed box, not sure how those subs sound sealed. Fiber glassing will save some weight, but if you are still going to use MDF, its not gonna get you quite where you want. I would suggest either building a box out of BIRCH, or using birch as a skeleton for the fiberglass box. Birch is much lighter and can be just as strong.

^^^ just make sure its TRUE BIRCH...... My new box will be built using birch for the same reason u are to shed some pounds. I am on my second set of shocks in just over a year. Guess the manf did not expect someone to add an extra 400+lbs in the trunk..

 

[szmidi 10+ year member]

Well I am no expert, so I cannot answer all your questions...But yes if each sub has a recommended 2 cubes, then they together will need 4 cubes, which is more than likely after all displacements (i.e. port area, sub displacement, and any bracing). You can put them in a shared chamber ported box, which is what I assume the recommended 2 cubes each is for. To save even more room, you may want to consider a sealed box, not sure how those subs sound sealed. Fiber glassing will save some weight, but if you are still going to use MDF, its not gonna get you quite where you want. I would suggest either building a box out of BIRCH, or using birch as a skeleton for the fiberglass box. Birch is much lighter and can be just as strong.

Awesome. Thank you. Apparently this program will give me the optimum design if I can get all the parameters right. Taking a guess at those Z and le fields it keeps telling me sealed around 84L which is almost 3 sq ft I think.

So looking at my options for the two subs. I have the option of two separate boxes. One massive box with the two in it. Or two boxes ported together??

Or this looks a bit in between the one big box and the ported box. Think its more for strength though.

 

[The_Grimy_One 10+ year member]

^^^ just make sure its TRUE BIRCH...... My new box will be built using birch for the same reason u are to shed some pounds. I am on my second set of shocks in just over a year. Guess the manf did not expect someone to add an extra 400+lbs in the trunk..

How do you know if it is true Birch, and where can you purchase some at?

 

[The_Grimy_One 10+ year member]

Awesome. Thank you. Apparently this program will give me the optimum design if I can get all the parameters right. Taking a guess at those Z and le fields it keeps telling me sealed around 84L which is almost 3 sq ft I think.
So looking at my options for the two subs. I have the option of two separate boxes. One massive box with the two in it. Or two boxes ported together??

Or this looks a bit in between the one big box and the ported box. Think its more for strength though.

It is telling you to do 3 cubic feet for both together? If you are doing sealed, I would not do a shared chamber box. I would add a piece that cuts the box in half, which will also add strength. If you are going ported, also just build one big box, but they can share the same chamber...

Either way, since you are saving space, it makes no sense to build 2 separate boxes.

 

[The_Grimy_One 10+ year member]

Awesome. Thank you. Apparently this program will give me the optimum design if I can get all the parameters right. Taking a guess at those Z and le fields it keeps telling me sealed around 84L which is almost 3 sq ft I think.
So looking at my options for the two subs. I have the option of two separate boxes. One massive box with the two in it. Or two boxes ported together??

Or this looks a bit in between the one big box and the ported box. Think its more for strength though.

Also, did you try just leaving those factors blank? I think you can just leave some of the info out, and it will still calculate the box as best as it can, rather than guessing info. But I am not sure.

 

[szmidi 10+ year member]

Nah, I tried leaving them blank and it wouldn't save / update.

I am pretty sure its 3 for the both, but I;m not sure if I;ve set it up right. Its saying I'll peak at 117db which can't be right.

And I'm not sure if saving space is an option. I dont even know if I'll have 4sq ft once I factor in the width of the wood and an amp rack

 

[disturbed471985 5,000+ posts]

How do you know if it is true Birch, and where can you purchase some at?

Real birch will cost alot. Like $60 a sheet. Look for Baltic. Lowes sales birch veneer which is not what u want.

 

[The_Grimy_One 10+ year member]

Real birch will cost alot. Like $60 a sheet. Look for Baltic. Lowes sales birch veneer which is not what u want.

Alright, sounds good. I will hunt some down.

 

[disturbed471985 5,000+ posts]

Alright, sounds good. I will hunt some down.

I do think lowes sales Birch ply but its in a small section and the sheets are not very big. So you will have to buy a few sheets to make a decent sized box. If it says birch and its cheap then its not what u want. You can also use Arauco almost the same as Birch but a tad cheaper but also a tad heavier but alot lighter then mdf..

 

[szmidi 10+ year member]

OK, so I emailed the guys at Linear who developed WinISD and they have been real helpful.

It looks like I have about 6 (or a touch less) square feet to play with. Should I tone this back to about 2sq per sub as recommended or is more room better if you have it?

Also how I want to have the overall box as a sealed design? But you suggest a port between the boxes. How big should this be?? Should it just be a hole in the dividing wall or should it have some length ie a piece of piping?

 

[szmidi 10+ year member]

Also WinISD makes the optimum size box for the volume that is entered. 84L was just a default setting I had to change. So that's all good now //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[szmidi 10+ year member]

Hi all, I need to re-open this thread to ask a few more questions. Birch looks like it is not going to be an option due to availability so I am going to go with fibreglass. However my knowledge of the subject is limited to 'its like paper mache'. There is strips of fibreglass and a resin and you paint the resin on then let it dry. I have read a few threads / worklogs but they seem to start a few steps past my current lack of knowledge.

So........

How thick does the fibreglass need to be?

Is fibreglass strong enough to hold the weight of the subs if they are mounted with the cone facing out horizontally?

Are there any sound quality issues with fibreglass as it won't be as solid as 3/4 inch mdf?

How much fibreglass will I need per square metre (or sq foot) so I can estimate costs?

If I mould the fibreglass into the stock interior, will it rub and wear away at the original plastics and damage them?

What does a typical fibreglass box weigh (my mdf box, with subs/amps is 60kg)

Do you just use screws into the fibreglass or is there another more suitable way of fixing the subs / amps in?

 

[disturbed471985 5,000+ posts]

I have no experience with glass boxes box based on the price of the materials alone to do a box that size you could order some birch and still save urself money. Do as you do I just have never liked glassed boxes to me they are just to flashy and scream the all show but no go moto. Then again I care more about performance then I do looks. That does not mean glassed boxes dnt perform I just dnt like the look.