Irish

iTrader: (3)

ok, i need some help from the audio junkies. ive built two custom boxes in the past.1 sealed and 1 vented. im selling both. now i am building a vented to be tuned to my new sub. the sub is a DA M6D2. no can anyone help me with a UNDERSTANDABLE yet detailed and informative instructions on how to determine the box size, where to place the vent, how long to make the vent( across the inside of the box). i was wanting to know the formulas and ther info for making this box. i know factory specs of the sub are ran most of the time off of 14.4 volts, so i dont know how to determine what to use if my battery doesnt run that high, cause i know it doesnt. im trying to do this right and make it loud at the same time. what i will be running is

12" Diamond Audio M6D2
Diamond Audio D51200.1
all in a tuned,vented box(custom built by me)

so please help

-irish-

Robert_J

The voltage of the battery has nothing to do with the specs of the subwoofer. Here are the specs that I found:
Impedance: Dual 4ohm
SPL 1w/1m: 86db
Qes: 0.55
Qts: 0.49
Fs: 31.0 Hz
Vas: 30.3L
Cms (mm/N): 0.087
Mms: 311g
Sd (M2): 0.0497
BL (T-M): 19.0
Re: 3.3
Xmax: 15mm

There are a lot of complex formulas for this. Like this:
Vas = Equivalent air compliance (litres)
Qts = total Q of the driver at its resonant frequency
Fs = resonance frequency of the driver (Hz)
Dv = internal diameter of port (cm)
then,

Vb = 20*Qts^3.3*Vas
Fb = (Vas/Vb)^0.31*Fs
F3 = (Vas/Vb)^0.44*Fs
dBpeak = 20*LOG(Qts*(Vas/Vb)^0.3/0.4)
where,

Vb = net box volume (litres)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak or dip in system response

If this is too much, download WinISD.

Any place that is has room to breathe.

It sounds like you are talking about a slot port. WinISD has this option but doesn't take into account end-correction. There is a tutorial at the JL Audio site that should have this formula. Just make sure you have enough port area so that you don't get any port noise at high volumes. WinISD will give you a good idea of this.

-Robert

kcidmil

DA's site list the air space and port sizes on their website. http://www.diamondaudio.com/Files/pr...M6sub_rev2.pdf
All the dimensions are listed at the bottom.

This is one reason why I like Memphis Audio. They hired Audio Enhancers to make boxes for Memphis, based upon Memphis's specs. But of course, it does take all the fun out it.

Robert_J

That's easy. 1.5^3ft tuned to 31hz.

-Robert

kcidmil

ahh, but with the wrong port size, it'll sound like crap.

Maxima Dan

It's really easy to calculate port dimensions, all you need is the Vb and Fb. There are about a dozen port length calculators on the net. I would still download WinISD and use it to calculate the port length and model the air speed in the port to make sure it has enough area.

Robert_J

Based on the PSP Site, the 18" long, 4" diameter port will tune the box to 32.85hz. That's less than 2hz difference.

Please elaborate on what will be wrong with the sound.

-Robert

kcidmil

you can make the port to the right specs, but if you get the opening wrong inside the box (used to making square ports) and you'll end up with it sounding like crap.

Robert_J

If you wrap the port along an outside wall, all you have to do is apply end correction. That usually involves making the port slightly shorted than is called for by the simulations. If you make a square port (or round) that isn't near any side of the box, then make it the required length. Flared ports (like PSP makes) need to be an inch longer to take into account the flared ends. The flared ends also help reduce port noise at high volumes.

-Robert