help nic design a new sub box

[Nic92]

hey guys

so i am thinking about buidling a new box for my sub

the box i have now is a bit small (3.8cf after port/sub displacement) but it does sound ok. i was looking at getting a bit more out of my subwoofer if you know what i mean.

anyway my friend helped me design a box to fit in my boot and im not sure if it will fit sliding in, i might make it up out of cardboard and see how it fits.

i just want to know what you guys think or have any recommendations or tips?

so anyway the pictures with the dimensions is in attachments (It's somewhere around 6.5cuft@32hz, give or take a little)

here are the sub specs

Enclosure Recommendations:
Compact Optimal
Sealed: Not Recommended
Ported: 5.5@25Hz, 8.0@34Hz

Dimensions:
Mounting Depth: 9.4 inch
Mounting Hole Diameter: 17.75 inch
Overall Diameter: 18.5 inch
Bolt Hole Circle: 17.5 inch
Motor Width: 6.5 inch
Motor Depth: 3.25 inch
Basket Depth: 6.25 inch
Displacement: 0.22 cubic ft.
Weight: 28 lbs (12.7 kg)

T/S Parameters:
Electrical Q Value (Qes): 0.53
Mechanical Q Value (Qms): 6.1
Total Speaker Q Value (Qts): 0.48
Free Air Resonance (Fs): 33.2 Hz
Equivalent Compliance (Vas): 159 liters
One-Way, Linear Excursion (Xmax): 22 mm
Efficiency (SPL 1W/wm): 92.7 dB SPL
Effective Piston Area (Sd): 1210cm^2
DC Resistance (Re): 1.9 ohm
Nominal Impedance (Znom): Dual 2 or 4 ohm
Thermal Power Handling (Pe): 1000 W
Force Factor (Bl): 21

[Nic92]

bump for a reply.

[sweefu]

Are you looking for more volume (Higher SPL at a comp, high dB reading) or nicer bass to listen to? These things are fairly opposite, your bass will be louder around 40 - 50hz but this will sound pretty rubbish if you are listening to music, something lower like 32 or 35hz will sound good to listen to but will not be as loud on the termlab.

What I have said above is very general and broad statement but it more or less applies to what you are considering here.

[Nic92]

Are you looking for more volume (Higher SPL at a comp, high dB reading) or nicer bass to listen to? These things are fairly opposite, your bass will be louder around 40 - 50hz but this will sound pretty rubbish if you are listening to music, something lower like 32 or 35hz will sound good to listen to but will not be as loud on the termlab.

What I have said above is very general and broad statement but it more or less applies to what you are considering here.

im not sure yet, i will talk to my friend about it, but either way the box needs to be bigger. so that is my main concern at the moment. and then lets talk about tuning after i know for sure the box is going to fit into the boot.

[Nic92]

so look at my dodgey atempt of making it out of cardboard to see if it fits. i did the whole height as 40cm because i just didnt bother with the little bit at the top which was 20cm depth, the box went in about half way and got stuck but it wasnt 35cm high. so i rekon it would be pretty close. but it was the wrong way around lol silly me, so when i tried it, the 70cm was at the front and 80cm was on the side. i rekon it would just fit going in even if the sub (cone) gets pushed down as it goes in.

what are your thoughts?

[Nic92]

as for tuning.. its just hard to decide. because i want it loud but i dont want it to sound like poo

[Nic92]

so after having another look the box can go about 4cm wider and it will add about another .4cf so my friend is going to re do the design and it is going to get tuned low (well it is a daily setup). il post up pics when i get the sketch ups. anyway its going to be good because its going to add an extra 3cf to the volume from the old box.

it would also be nice if ppl would show some input

[MAG00]

Are you sure it will fit without damaging the sub? Have you left enough room for the movement of the sub?

[sweefu]

This is a good point, your xmax seems to be 22mm at full bang, so you technically need 11mm room, but I'd want minimum 50mm to be safe, while taking it in and out etc

[Nic92]

there was about 11cm (measured it from the outside rubber bit on the sub to the boot light) for excursion with the old box and this one is only 2cm higher, i left heaps of room just to be safe

[Nic92]

my friend finally got back to me and said

‎7cuft@31.3hz so it'll work out to about 6.9@32hz with the sub in. Is the the tune you want? Theoretically going from 32hz tune to a 35hz tune gives a peak of 2db higher around 40hz. Or Tuning 37hz gives a 3ish db gain around the same area. Upto to you though. The 32hz tune has a dead flat response down to 35hz where as the other 2 peak @40hz like I said.

now i just need to decide

[MAG00]

If you want sound quality, aim for dead flat. If you want loud beats, go for a peaked response.

[Nic92]

yeah man im going for the 32hz tune, since im not really going for a spl setup, its mainly for daily so as soon as i get the sketch up pics of the final design, il post up

[MAG00]

Sounds good, what thickness of MDF are you using?

[Nic92]

18mm and double baffle the top where the sub mounts, also alot of bracing

[MAG00]

Have you taken the volume displacement of the added thickness and bracing into account of the internal volume?

[Nic92]

friend designed it all and told me to do it that way ^ so im guessing yes he did, i get the sketch up tomorro and il show ya how it will be.

since my old box was a bit of a fail with no bracing or anything

[sweefu]

If it were me I would be going with something thicker than 25mm, even though you have bracing for a sub of this size it will be pushing a lot of air, I would go something a little bit thicker. Are you going to seal the inside with polyester resin? Will only cost maybe $15 for 1kg which would do a great job of sealing everything. Be sure to put the box together with MDF glue also or proper wood glue (Selley's aquadhere) Not Liquid nails or any construction adhesive, the MDF glue soaks into the MDF making a very strong join, rather than the Liquid nails which just sits on top of the MDF

[Nic92]

yeah but last time i wanted thicker wood like 1inch for example, they had to order it in and would cost like $100 for postage or something. unless theres another place to buy wood from? other than bunnings hehe, also thicker wood, would take up more boot space/volume, if i were to use thicker wood, i guess i could just fit it in the boot.

what if i get half an inch wood and seal 2 peices of wood together to get 1inch thick for the whole box?

i have never heard of polyester resin and since it will cost under $20 i might aswell do it

thanks for the glue tip

[Nic92]

i finally have the final design here, so it ended up as 6.9cuft@31.5hz and after displacement it is around 6.8cuft and tuning is just under 32hz

so watcha think?

[Monster-VZ]

use thick wood maybe MDF and make sure it is stuck right so theres no vibration make sure its custom to fit ur boot so u can fit anything else in there instead of having a box in the middle of you boot and fit nothing in there

[HCVP]

If your serious about bracing i would be looking to do more than just adding ribs.

[Nic92]

yeah i think he did it so it doesnt take up to much volume

[sweefu]

Bunnings should have something decently thick. Which side of WA are you on? I'll take to some friends and see who stocks decent MDF.

[Nic92]

yeah umm Perth