PDA

View Full Version : Designing The Right Box! Help!



Cali_Screw
08-13-2008, 06:43 AM
Hey every one, I would like help from you experts out there on designing a box for two RE Audio SE 12's Sealed. The subs will be placed in a truck under that back seat. Will be up fired!

Here is the space available to give you and idea:

http://i35.photobucket.com/albums/d174/weazel_32/6178-10407-150064.jpg



Now I have thought about up firing them in a box like this, but of course much larger for the specs of the sub:

http://i35.photobucket.com/albums/d174/weazel_32/100_1632.jpg


Now my BIG question is, is this box design going to create issues with the sub performing the way they should? Such as not creating bass notes it should be due to design or not getting the output it should from design......


any help is very much appreciated!

Bun-Bun
08-13-2008, 12:53 PM
Sealed boxes there is only one factor... volume. Make it big enough (but not too big as to loose power handling) and your golden! You can use WinISD Pro

Someone correct me if I am wrong...

EDIT: Here are some formula's you can use to calculate your box volume

http://www.diysubwoofers.org/sld/sealed1.htm

KHARPS
08-13-2008, 12:56 PM
As long as you have the correct volume and the surround doesn't hit the bottom of the seat during excursion you should be fine.

Bun-Bun
08-13-2008, 01:06 PM
Looking up the T/S Paramaters...

SE
12"
Electrical Q Value -Qes: 0.49
Mechanical Q Value -Qms: 4.5
Total Speaker Q Value -Qts: 0.44
Free Air Resonance -Fs: 25.1 Hz
Equivalent Compliance -Vas: 72.9 liters
One-Way, Linear Excursion -Xmax: 18 mm
Efficiency -SPL 1W/1m: 86.1 dB SPL
Effective Piston Area -Sd: 480 cm^2
DC Resistance -Re: 2.8 ohm
Nominal Impedance -Znom: Dual 2/4 ohm
Thermal Power Handling -Pe: 600 W
Force Factor -Bl: 17.7

Thus

Qr = Qtc/Qts
Vr = Qr^2-1
Vb = Vas/Vr
Fb = Qr*Fs

Qtc typically 0.7 (or so it says thats a good value to start with)

Qr= 0.7/0.44 = 1.5909
Vr = (1.5909)^2 - 1 = 1.5310
Vb = 72.9/1.5310 = 47.6162
Fb = 1.5909*25.1 = 39.9

So your box should be 1.6816 ft^3 and will have a resonant frequency of 39.9Hz. If you want it to go lower then use a lower then use a lower Qtc (0.6 would result in 34.2Hz resonant frequency) but that will decrease power handling.

EDIT: I am an idiot! that is for one sub... x2 for both. So 3.3632ft^3.

Cali_Screw
08-13-2008, 04:36 PM
actually they say 1.0 optimal for a single 12" so for 2 i would need 2.0 cuft.


also do you guys know if these are a SQL woofer?

Bun-Bun
08-13-2008, 05:55 PM
Manufacturer's recommendations are not the only way to go though. It depends on what you personally what. However there reccomended 1ft^3 per gives is a Qtc of .832 and a resonant frequency of 47.5 hz. If tuning that is ok for you then do it!

Other then that... build the box and takes lots of pics ;)

Cali_Screw
08-13-2008, 06:12 PM
Manufacturer's recommendations are not the only way to go though. It depends on what you personally what. However there reccomended 1ft^3 per gives is a Qtc of .832 and a resonant frequency of 47.5 hz. If tuning that is ok for you then do it!

Other then that... build the box and takes lots of pics ;)

im not to educated in the hz, but the larger the box, the lower your saying it will be able to go sealed?

what is QTC?

Bun-Bun
08-13-2008, 06:17 PM
im not to educated in the hz, but the larger the box, the lower your saying it will be able to go sealed?

That is correct. However with sealed there comes a trade off. Smaller box gives higher tuning but better power handling (hence why manufacturer recomends a smaller box) and a larger box will let you go lower but decrease power handling.

Using the forumla's above you pick a Qtc between .6-1.0 to calculate the size of your box. Lower Qtc will give you a bigger box where a higher Qtc will give you better power handling.

However there are other factors to consider such as cabin gain, car resonant frequency, and the sweet spot for those subs... none of which I have enough experience with to offer any advice. But I thought I would give you a push in the right direction should you desire to take your design that one next step farther ;)

GL!

Cali_Screw
08-13-2008, 06:43 PM
That is correct. However with sealed there comes a trade off. Smaller box gives higher tuning but better power handling (hence why manufacturer recomends a smaller box) and a larger box will let you go lower but decrease power handling.

Using the forumla's above you pick a Qtc between .6-1.0 to calculate the size of your box. Lower Qtc will give you a bigger box where a higher Qtc will give you better power handling.

However there are other factors to consider such as cabin gain, car resonant frequency, and the sweet spot for those subs... none of which I have enough experience with to offer any advice. But I thought I would give you a push in the right direction should you desire to take your design that one next step farther ;)

GL!


**** you know way to much, Does the shape of a sealed box matter as shown in the picture? Or is it fine? Also if the recommend 1.0 per sub think 1.25 would be a nice size making it 2.5 total?

Bun-Bun
08-13-2008, 06:58 PM
**** you know way to much, Does the shape of a sealed box matter as shown in the picture? Or is it fine? Also if the recommend 1.0 per sub think 1.25 would be a nice size making it 2.5 total?

Can never know enough...

And everything i've said can been found with a quick google search and the search button on your screen here.

1.25 per sub will give you a Qtc of .77 and 43.9Hz resonant frequency. Probably would be fine. I have no expereince building sealed enclosures but I would think that would be good. Just watch the power you put to it so that you dont push it past its mechanical limits.

Also I can not see your pic but I am pretty sure shape does not matter for sealed enclosures.