Anyone build a custom down fire sub box

[tsdahc]

I am planning on doing a small upgrade to the audio. I’ve seen Marks thread and a few others but has anyone built a down fire sub enclosure for the back? I have an Alpine SWRT-10 that I made for under a seat in an old f150. It has a 3.25 mounting depth and can be in an enclosure as small as .25. I ran 600w to it and it slams, will probably run a JL XD/700/5 to it as I have one and the other channels running the door speakers. Any thoughts on the downfire configuration for the Mach E? Pretty sure I can make it 5” tall which will allow for almost 2” of movement on the sub and still should be able to use the floor in its low position?

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[markboris]

I am planning on doing a small upgrade to the audio. I’ve seen Marks thread and a few others but has anyone built a down fire sub enclosure for the back? I have an Alpine SWRT-10 that I made for under a seat in an old f150. It has a 3.25 mounting depth and can be in an enclosure as small as .25. I ran 600w to it and it slams, will probably run a JL XD/700/5 to it as I have one and the other channels running the door speakers. Any thoughts on the downfire configuration for the Mach E? Pretty sure I can make it 5” tall which will allow for almost 2” of movement on the sub and still should be able to use the floor in its low position?

Yes 5" is about as tall as you can go to allow the cargo floor to be used in the lower position. I don't see anything wrong with using a down fire sub.

 

[tsdahc]

Thank you Mark for the reply. I went through your entire thread. Trying to figure out the rest of the install and would like to use stuff I already have. Will need the PAC or May try and get my lc6i to work. I’m going to hopefully look at the area this weekend when I get back in town see what I can come up with in the back with the sub and amp rack. What did you end up doing with your tweeters in front?

 

[markboris]

Thank you Mark for the reply. I went through your entire thread. Trying to figure out the rest of the install and would like to use stuff I already have. Will need the PAC or May try and get my lc6i to work. I’m going to hopefully look at the area this weekend when I get back in town see what I can come up with in the back with the sub and amp rack. What did you end up doing with your tweeters in front?

I changed the crossover capacitor from a 6.8 to a 3.3 reduced some of the lower end harshness and then added some foam to the little enclosure it is in to reduce the bounce and reflection of the sound coming off the window. I'm not big on reflective sound. The tweeter already is pointed towards the listener and I don't want a secondary reflective sound coming from the same source.
https://www.macheforum.com/site/thr...em-harsh-high-end-tweeters.41879/#post-902387

 

[Okuma]

I built the attached sub that can be used in up or down firing applications. To use for down, just add spacers to the ends to raise it off the floor more than the rated speaker travel. The attached PDF shows most of my steps but doesn’t include measurements. There are lots of box calculators out there to help with dimensions.

 

[iexiak]

@tsdahc I managed to fit a Kicker TRTP12 which is 6-1/8" tall while looking factory. With the rubber mat it was <1" above the bottom of the lift gate, but without it no one would be able to tell. I did lift the floor a bit at the front with a 2x4, but that was mostly so I could carry heavier things in the trunk without worrying about the floor.

https://www.macheforum.com/site/thr...nd-base-select-model-audio-information.33647/

If you do not have the B+O you will want this - https://pac-audio.com/products/lphfd31
and probably this - https://pac-audio.com/products/lphext17?_pos=1&_sid=9d93122ef&_ss=r
Harness hooks in below the glovebox to the left, remove the 2 kick panels and you'll find the spot.
If you have B+O - https://pac-audio.com/products/ap4-fd31.


I don't see any reason why the LC6i won't work....except that the speaker signals have bass roll off at the bottom end to protect them from over-excursion. If you find this annoying, it's not something that the accubass on the LC7i really helps with unfortunately. Music I listen to had this problem but you might find that music you listen to doesn't, so I'd say go with the hardware you already have.

 

[tsdahc]

I built the attached sub that can be used in up or down firing applications. To use for down, just add spacers to the ends to raise it off the floor more than the rated speaker travel. The attached PDF shows most of my steps but doesn’t include measurements. There are lots of box calculators out there to help with dimensions.

Does the floor hit the speaker at all? Looks like a good job on that box! I be built a couple, last one was the contour of an f150 rear seat, that was a pain. Square ish boxes are so much easier to build, no angles. I’m going to get some measurements this weekend I hope to start planning a box.

 

[tsdahc]

@tsdahc I managed to fit a Kicker TRTP12 which is 6-1/8" tall while looking factory. With the rubber mat it was <1" above the bottom of the lift gate, but without it no one would be able to tell. I did lift the floor a bit at the front with a 2x4, but that was mostly so I could carry heavier things in the trunk without worrying about the floor.

https://www.macheforum.com/site/thr...nd-base-select-model-audio-information.33647/

If you do not have the B+O you will want this - https://pac-audio.com/products/lphfd31
and probably this - https://pac-audio.com/products/lphext17?_pos=1&_sid=9d93122ef&_ss=r
Harness hooks in below the glovebox to the left, remove the 2 kick panels and you'll find the spot.
If you have B+O - https://pac-audio.com/products/ap4-fd31.


I don't see any reason why the LC6i won't work....except that the speaker signals have bass roll off at the bottom end to protect them from over-excursion. If you find this annoying, it's not something that the accubass on the LC7i really helps with unfortunately. Music I listen to had this problem but you might find that music you listen to doesn't, so I'd say go with the hardware you already have.

I have the B/O, I’m contemplating getting the pac system for the b/o because I think it has all the harnesses to connect to factory which makes life so much easier.

 

[Okuma]

Does the floor hit the speaker at all? Looks like a good job on that box! I be built a couple, last one was the contour of an f150 rear seat, that was a pain. Square ish boxes are so much easier to build, no angles. I’m going to get some measurements this weekend I hope to start planning a box.

Thanks! No the floor does not hit the sub. I used a JL Audio 10W3-D4, which is low profile, and I was able to do a thinner box.

 

[DanoiZ]

I built the attached sub that can be used in up or down firing applications. To use for down, just add spacers to the ends to raise it off the floor more than the rated speaker travel. The attached PDF shows most of my steps but doesn’t include measurements. There are lots of box calculators out there to help with dimensions.

Nice custom build! Do you know what the max width and length a box can be in that space?

 

[Okuma]

Nice custom build! Do you know what the max width and length a box can be in that space?

Thanks, @DanoiZ . I took the foam piece out an measured it a while back but I don't have those measurements anymore. There are a lot of angles in that space, so you can get really creative on its use, but I just went for simplicity with my box. Measurements also depend on if you want the trunk floor to be at the upper or lower position. What I like best about my box is that I can install it under the trunk floor or above.

 

[DanoiZ]

I'm wanting to do a build with a 12" Hertz MPS 300 S2. It has similar space requirements as your TW3. I always keep the floor in the upper position and that is not going to change.

 

[Okuma]

I'm wanting to do a build with a 12" Hertz MPS 300 S2. It has similar space requirements as your TW3. I always keep the floor in the upper position and that is not going to change.

Good sub choice. A solid performer, a slim profile, and it's not hard on the wallet. You will need to be creative when using anything larger than a 10" sub due to space limitation but it's definitely possible. You just need to make same angled cuts to allow for a larger hole cutout but I don't think it will be difficult, no matter your skill level. There is less space at the bottom of the trunk when the foam is removed, so I'm guessing you'll need to build for a top-firing sub. It will sound great. I used this site for my box design: https://subbox.pro/en/design/

By the way, I used to live in Layton and Millcreek. Have you had any issues with windshield pitting when trucks lay salt/sand in the winter?

 

[DanoiZ]

Good sub choice. A solid performer, a slim profile, and it's not hard on the wallet. You will need to be creative when using anything larger than a 10" sub due to space limitation but it's definitely possible. You just need to make same angled cuts to allow for a larger hole cutout but I don't think it will be difficult, no matter your skill level. There is less space at the bottom of the trunk when the foam is removed, so I'm guessing you'll need to build for a top-firing sub. It will sound great. I used this site for my box design: https://subbox.pro/en/design/

By the way, I used to live in Layton and Millcreek. Have you had any issues with windshield pitting when trucks lay salt/sand in the winter?

Thanks! Yeah, it will be top-firing. I will check out that site.

Funny. I live in SLC and work in WV and just got a little chip on my windshield right before Xmas while driving on the 201. LOL! I need to get it filled but I park in a garage at night and under an awning at work and luckily it hasn't spread, yet.

 

[markboris]

Nice custom build! Do you know what the max width and length a box can be in that space?

I have a JL 12" Powerwedge+ and it is a very tight fit. Dimensions are 21"W x 13.5"D x 6.75H but with the grill which you would want to keep on, 7.75H. You could go 8"H but that's about it. I do have Dynamat and 1/4" Dynaliner foam over it on the cargo floor and then the OEM carpet on top of that so if you removed all of it, you could probably gain another 3/4" in height. Mine is facing up.

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