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Underseat Ported subwoofer Box

Zero6391

New Member
Joined
Feb 5, 2019
Messages
6
Location
New Mexico
Hello,
      So I got my 2003 avalanche and I wanted to have a subwoofer. I couldn't really find too many installs for underseat applications and everywhere I looked to buy a box already prebuilt were either too expensive (over $200) and didn't cater to the ported design I was wanting so I decided to build my own box and document it here for anyone wanting to have something similar. for audio equipment I settled on Rockford Fosgate P3SD2-10 and for the amp I wanted the smallest amp possible so I will be using a Rockford Fosgate PBR300-2. for this install I will not be removing anything from the truck, not even the insulation under the carpet that so many other sites that build boxes require so lets jump into it. cant figure out how to upload pictures or files onto here so im just gonna have to wing it as best as I can.

L= Length
D= Depth
H=Height
W= Width
(P)= Side With the Port
(S)= Side Where The sub goes
                                           

Here is the box shape and measurements looking down from the top (This is Just a rough shape)

                                                              42" W
                              _____________________________________
                              [                                                                ]
                              [                                                                ]
                    17" D  [    (P)                                          (S)        ]
                              [                  ______21"W______                  ]
                              [                  ]                          [                  ]
                              [                  ] 4"D                    [                  ]
                              [__________]                          [__________]
                                    8.5"W                                        12.5"W


Here is a view looking at it from the front.
       

                                      8.5"W              18"W                  12.5"W
                                __________        __________        _________
                                [                ]____[                  ]___[_________]
                                [                                                                    ]
                        5"H  [                _4"W                                            ]  5.5"H
                                [              ]    [________________                ]
                                [XXXXXXXX]                                    [________]
                           

Notes for this diagram:
      1. The XX's signify where the slot opening for the port will be located
      2. the port will be on the passenger side with the sub being on the driver side
      3. these measurements are just for the front of the box. the underside of the seats slop downward so the top of the box will follow that slope
      4. There will be an additional plate of wood on the driver side for the subwoofer to raise it and gain some depth, for this build I was able to get 5.5" mounting depth (Fun fact: you want at a voice coil depth or free air behind the subwoofer, ex. the sub im using has a 2.5" voice coil so I made sure to have at least 2.5" between the sub and the bottom of the box)


Here is the diagram build the slot port looking at it from the side

                                    Top

                      ---------
                      [          \_______________
      Front        [                    {              ]
                      [___________{____        ]  3.5"H          Back
                      _____________________]
                                        17"D

Notes For this diagram:
    1. The Slot Port will need to be 6"W x 1.5"H x 18"L to be tuned to 35hz
    2. The port will curve inside the box to be able to achieve that length
    3. The Dotted line on the top signifies it will be sloped from the front down to where the solid line begins.


Notes for the whole design of the box:
    1. the notch in the middle of the box will allow it to go up and over the support bar that is under the seat
    2. I used 1/2" MDF and liquid nail for the whole box construction
    3. depending on your needs you can get roughly 1.14 cu. ft of internal airspace before sub and port and after all is said and done you will be left with about 0.95 cu. ft internal airspace
    4. there is only a choke point where the support bar is because the seat has a support brace running along bottom of it so itll create a passage that is about 1" tall and 13" wide which as long as you sand down the corners of the wood there wont be any internal "chuffing"



final words:
    So there is my box that Ive designed and built, its works and sounds great and is still able to be fully removed in case you need to use your midgate. the box is a little complicated in design, just imagine build 3 separate boxes and then joining them together. if you need the maximum airspace available you have to go around a lot of corners and nooks which isn't really that bad, it took me 4 days to finally complete this box. but if u need less airspace of course the box can be modified to be more simple. and port length can be changed according to your personal tastes. a ten inch sub isn't really gonna be hit lows as hard due to the mechanical limits of the driver itself so 35 hz was a good spot for me. but yea there it is, I hope this will encourage or help another DIY installer looking for some light bass without removing anything and keeping the truck as normal as possible. and if anyone can tell me how to include pictures and PDF files I can upload all my sketch work and what the box and sub look like in the truck
 
:welcome: to the club  :wave:

Awesome 1st post
 
Tagging this thread, love builds like this. I plan on modding my Jeff D style under seat sub boxes I built soon. Just don't know when I'll find the time.

Anyhow  :welcome:
 
Hello,
So I got my 2003 avalanche and I wanted to have a subwoofer. I couldn't really find too many installs for underseat applications and everywhere I looked to buy a box already prebuilt were either too expensive (over $200) and didn't cater to the ported design I was wanting so I decided to build my own box and document it here for anyone wanting to have something similar. for audio equipment I settled on Rockford Fosgate P3SD2-10 and for the amp I wanted the smallest amp possible so I will be using a Rockford Fosgate PBR300-2. for this install I will not be removing anything from the truck, not even the insulation under the carpet that so many other sites that build boxes require so lets jump into it. cant figure out how to upload pictures or files onto here so im just gonna have to wing it as best as I can.

L= Length
D= Depth
H=Height
W= Width
(P)= Side With the Port
(S)= Side Where The sub goes


Here is the box shape and measurements looking down from the top (This is Just a rough shape)

42" W
_____________________________________
[ ]
[ ]
17" D [ (P) (S) ]
[ ______21"W______ ]
[ ] [ ]
[ ] 4"D [ ]
[__________] [__________]
8.5"W 12.5"W


Here is a view looking at it from the front.


8.5"W 18"W 12.5"W
__________ __________ _________
[ ]____[ ]___[_________]
[ ]
5"H [ _4"W ] 5.5"H
[ ] [________________ ]
[XXXXXXXX] [________]


Notes for this diagram:
1. The XX's signify where the slot opening for the port will be located
2. the port will be on the passenger side with the sub being on the driver side
3. these measurements are just for the front of the box. the underside of the seats slop downward so the top of the box will follow that slope
4. There will be an additional plate of wood on the driver side for the subwoofer to raise it and gain some depth, for this build I was able to get 5.5" mounting depth (Fun fact: you want at a voice coil depth or free air behind the subwoofer, ex. the sub im using has a 2.5" voice coil so I made sure to have at least 2.5" between the sub and the bottom of the box)


Here is the diagram build the slot port looking at it from the side

Top

---------
[ \_______________
Front [ { ]
[___________{____ ] 3.5"H Back
_____________________]
17"D

Notes For this diagram:
1. The Slot Port will need to be 6"W x 1.5"H x 18"L to be tuned to 35hz
2. The port will curve inside the box to be able to achieve that length
3. The Dotted line on the top signifies it will be sloped from the front down to where the solid line begins.


Notes for the whole design of the box:
1. the notch in the middle of the box will allow it to go up and over the support bar that is under the seat
2. I used 1/2" MDF and liquid nail for the whole box construction
3. depending on your needs you can get roughly 1.14 cu. ft of internal airspace before sub and port and after all is said and done you will be left with about 0.95 cu. ft internal airspace
4. there is only a choke point where the support bar is because the seat has a support brace running along bottom of it so itll create a passage that is about 1" tall and 13" wide which as long as you sand down the corners of the wood there wont be any internal "chuffing"



final words:
So there is my box that Ive designed and built, its works and sounds great and is still able to be fully removed in case you need to use your midgate. the box is a little complicated in design, just imagine build 3 separate boxes and then joining them together. if you need the maximum airspace available you have to go around a lot of corners and nooks which isn't really that bad, it took me 4 days to finally complete this box. but if u need less airspace of course the box can be modified to be more simple. and port length can be changed according to your personal tastes. a ten inch sub isn't really gonna be hit lows as hard due to the mechanical limits of the driver itself so 35 hz was a good spot for me. but yea there it is, I hope this will encourage or help another DIY installer looking for some light bass without removing anything and keeping the truck as normal as possible. and if anyone can tell me how to include pictures and PDF files I can upload all my sketch work and what the box and sub look like in the truck
can you email them to me the pictures and stuff
 
That was a great writeup from 2019, and looks like the OP disappeared in 2021. Will be interesting if you get a response, @mo0n
 
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