Custom Box for Truck; Size constraints - Help & Tips needed

[Memnoch]

Hello, this is my first post here! I am trying to build a sub box for my sons truck. It is his first truck, and we got him his first sound system for Christmas. There is of course size restraints on the box dimensions and I just want to get some feedback before I start cutting anything to build his box. The previous owner had some sort of subs installed, and the wiring is all still intact. The line to the battery is there, the ground is there, and the connections and remote line for the amp are all ran and connected to the deck already. I did purchase a wiring kit though in case but it doesn't look like I will need any of it except for the speaker wire to wire the subs themselves to the amp.

The 2 sealed boxes that the audio place sold us cut out the holes too big, and we won't be able to return them for a while (time and distance from us). So I purchased an 8x4 MDF sheet and the screws, glue etc.. to put one together myself. He would prefer a single box to 2 boxes if that is possible. Details are in the list below for the vehicle and subs etc.

Vehicle : 2001 Dodge Ram 2500

Location in the vehicle: Behind the seats

Space available (Length x Width x Height): 63 1/2" L 8 3/4" W 30" H

Subwoofer make and model: Massive UFO 12" shallow sub

Subwoofer Size: 12

Number of Subwoofers: 2

Type of Port (Kerfed, Slot, Aero, etc.): (unsure)

What type of music do you like?: He listens to pretty much everything but probably heavier on rap

Is your goal SPL or Everyday Music?: Everyday

Tuning Freq (Hz): Unsure

Volume : Unsure

Questions:

Recommended air volume is 1 Cubic Ft per sealed box per 12" sub. The only other recommendation I can find on the spec sheets for the sub is a dual ported box which is 3.11 cubic feet. But the dimensions of that box will not fit his space due to the limited depth of 8.75".

I have come up with a simple rectangle design for the box as follows:

34" long
18" tall
8.75" wide

with the .08 displacement of each sub that would give me roughly 3.13 cubic feet of air space, which is pretty close to the ported recommendations but there is no port on this. Would I add a port or would I need to adjust the dimensions of the box to reduce the air space? Should I add braces inside the box (which would further reduce the cubic space); if so would the dimensions need to be adjusted further?

Would it be better to seal in each sub on the box (ie adding a wall for each sub or a wall between them)?


Please let me know if I am missing anything or if there are any questions. Any help is greatly appreciated!

Click to read more...

 

[Memnoch]

Or pick up a couple of these. Take a piece of 5" square leftover MDF, cut a 4" hole in it, mate up and glue the PVC to the back (to required length), good to go, neat and sweet!

Amazon product ASIN B071CLLVYK

Thanks for that. That is actually what I was looking at now. I don't have access to a Rabbet bit router to make an inner ring for the pipe, so was just looking into how I would mount it or make a flare to reduce that chuffing.

I am fairly sure he (brother in law) is not using anything other than he used to install some radios 20+ years ago so he knows best information. I may let him just build his box and build mine this weekend and then let my son decide which sounds better lol...

 

[Doxquzme Premium Member]

Those can be used at both ends if you really want to do it right. Keep the length at 20 as I already allowed for a 5% margin of error. As for the sealed versus the port, awesome as it is always subjective and in the end, your son gets to be the judge. I've been wrong in assuming what someone will prefer but not off on the design of this ported box. I'm confident in my assessments and ultimately the choice, but you never know, right?

Make sure to get some of your sons favorite low bass heavy music, play the same songs, at the same volume, same bass settings. I think your hard work will pay off.

 

[Doxquzme Premium Member]

Meant to ask, is there a subsonic filter on the amplifier you are going to use?

 

[Memnoch]

Meant to ask, is there a subsonic filter on the amplifier you are going to use?

I dont know to much about that side of it yet. It's a 2200w Diablo Class D monoblock sub. 1 Ohm stable DB-2200

 

[Doxquzme Premium Member]

I know plenty, but can't find any information on that amplifier. Do you have a manufactures link for it?

 

[Doxquzme Premium Member]

I dont know to much about that side of it yet. It's a 2200w Diablo Class D monoblock sub. 1 Ohm stable DB-2200

Does It Look like this? What is the total combined fuse rating?

 

[Memnoch]

Does It Look like this? What is the total combined fuse rating?

View attachment 55839
View attachment 55840

 

[Memnoch]

 

[Doxquzme Premium Member]

Okay, so it does have a subsonic crossover. You'll want it to be on and set to around 9o'clock. The LP filter to about noon. Once you have the sub plugged in, you can play some music, heavy on the bass, move it to the left and to the right sightly to see where it sounds best. My guess is about 10-11.

The two 12s should be wired to 1 ohm. That amp should give you about 550 watts at 1 ohm. That's based on a 50 amp fuse rating at 80% efficiency. You will need to wire the subs in parallel as follows:

Keep in mind that the amp is rated at 1 ohm, but may not like playing at that level all the time, hopefully, it plays nice and does not get overly warm.

in the even you;re able to change things up, look at getting something like this instead.

It [uts out 650 watts at 4 ohms which will allow the amp to run much cooler, control the woofer better and in general, provide better output and sound at a very reasonable price.

To wire the woofers to 4 ohms:

You could wire at 4 ohms to the Diablo too but at 4 ohms power output will only be about 250 to 300 watts from the Diablo.

 

[Firewalker]

I doubt even that for power. Everything I've seen online says those are about the same quality as Boss if not worse.

 

[Doxquzme Premium Member]

I generally don't use the bass boost at all. That unit has a fixed frequency boost and I don't know what it is set at, probably 40, 44 or 50 hz would be my guess. Set it all the way to the left while setting the LP filter and gains, then play with the boost to see if you like it turned up or not. I can't find the literature on the amp to see if that remote bass knob is for the boosted frequency or a volume control. It's a 6 pin wire so it could be either. My guess is it is likely just a volume knob to attenuate the overall output of the amp. Remote (gian style) is generally set all the way on when you set the gains so that when you use it to attenuate, it is never going to exceed the gain you set initially and overdrive the am into clipping.

 

[Doxquzme Premium Member]

I doubt even that for power. Everything I've seen online says those are about the same quality as Boss if not worse.

Granted, thus the suggestion for that recoil, pretty decent output for $102 and I'm sure a bit more productive (stable) than the Diablo.

 

[Doxquzme Premium Member]

Another really great reasonable amp that would give you a true 400 watts at 4 ohms or 700 at 1 and is an in house design from Stinger

 

[audiobaun 5,000+ posts]

NDA103 2000W Peak (1000W) RMS N-Series Class-D 1-Ohm Stable Monoblock Amplifier

Product Details: Class D 1 ohms Stable Monoblock Amplifier RMS Power Rating: 4 ohms: 390 watts x 1 channel 2 ohms: 660 watts x 1 channel 1 ohm: 1000 watts x 1 channel Total power output: 1000 watts CEA-2006 Compliant Amplifier Pulse Width Modulated MOSFET power supply Wired remote bass level...

nvx.com

 

[Memnoch]

Thanks for the feedback. Unfortunately we are stuck with that amp for now. I have been slammed with work so have not been able to do any research on amp side yet. The brother in law said something about bridging the speakers basically connecting all 4 sides of each speaker, but the parallel diagram above shows it skipping a + and - on each speaker. Stupid question, but is one side of the speaker the voice coil and speaker on the other side?

I will do my due diligence when I have some time to research it further. It is quite confusing when the amp states 2200w, 1 Ohm stable, but parallel would only net about 550w. I will get a better understanding of this soon.

Watching a video now, and interestingly in one of the videos they show the wiring and testing the resistance to see what the speaker is reading at which ohm level. I am pretty sure we did that with these and each side of the speaker was reading at 2 OHM. In the video a 4 ohm speaker was reading at 4 OHM from the one side tested. My brother in law said that the 2 OHM from either side added to get 4 OHM. I did not think that was correct. So is the speaker a 2 OHM speaker but listed as 4 OHM or is he correct that the 2 sides are adding together to reach 4 OHM?