Sub Box Plans
OK, heres the deal...does ANY ONE know the spific demintions for each chamber for the dual 12" sub box for the mm12's im having a hard time finding out the specs on it i have the over all demintions from the polk sight but id doesnt give it depth demintion for the chamber 1 and 3 wall posision, so if any one knows how many inches the sub supose to sit in side each chamber it would a big help.
Sub box plans
call polk? that looks way too complicated to guess (and bandpass is way too twitchy to estimate)
should be about .88 cubic feet
nope, .88 is for sealed, bandpass is much different.
I'm not sure if you've figured it out yet, but I'll give it a shot since nobody has responded yet. Seems like the Polk Team would have helped here to help everyone else trying the same.
Tip#1: The dimensions are only slightly forgiving, so be as exact as possible.
Tip#2: Take note, no fancy plexiglass or angled dividers until you get real good.
Tip#3: Do not obstruct the ports at all.
I've only built the bandpass box for an old EX08 single and people thought I had a pair of 12's :rolleyes: , so yours will be very impressive to say the least :cool: .
Looking at the dual Bandpass for the MM2124, we have:
Sealed Chamber 1=1.13CF
Ported Chamber 2=1.63CF w/3 ports
Sealed Chamber 3=1.13CF
The dimensions for the overall box shows to be 35 and 41/100 Width by 16" Height and 17" Deep. If you consider what the internal dimensions would be for heighth and depth (14.5" x 15.5") it should make figuring the 1.13 CF that it shows for chamber 1 and 3 easy.
1 Cubic Feet =1,728 Cubic Inches (12"x12"x12")
1.13 CF=1,952.64 CI
Then 1,952.64 divided by 14.5, then divided by 15.5=8.69" (just under 8-3/4")
So your sealed sections should be 14.5"x15.5"x8.69" internally since they say to use 3/4" material for building the box.
Tip#4: Draw the straight measurement lines on the walls of the box internally before assembly and it makes lining up the panels so much easier and rewarding. Later on with more experience, you can cut a dado groove to accept the panel, but that's another discussion.
To figure the ported section, just subtract the wall thickness of your boards and the sealed chambers. If you started out with 35.41" wide, you should end up with 15.03" left or a ported section of 14.5"x15.5"x15.03" internally.
Tip#5: Recess the PVC or ABS ports into the hole slightly from the inside and use a router with a round over bit to smooth the outside transition for the air to flow over. This will help quiet the air noise generated. If you buy aero dynamic designed ports, you will not have to do this. When there is a sharp edge, you'll hear them badly as the air whooshes in and out of the hole. Not bad sounding from a distance or through a trunk, but in a hatch back, it's terrible.
Get the TS parameters and put it into a nifty lil program... there's a bunch out there that'll work it exactly for you.
can anyone tell me how to build a sub box for the db124DVC 12" sub that is single band pass i cant find enough info on it on the website
the best way is to learn just start building.
As long as you know the volumes of the chambers and the tuning frequency, you can customize the rest of a 4th order bandpass.
Struby, if you can find the specs(vas, qes, qms, fs) for that speaker, send me a PM and I'll run some designs.
Please, never guesstimate a bandpass box. If you're way off, the sound will suck. Not to mention some speakers have horrible bandpass performance to start with.