Adding 8" sub & amp to B&O

[colinl]

EDIT: adding parts list to the original post so it's easy to find. The box dimensions are perfect *without the plastic insert*. If you want an 8" that fits inside the plastic insert check other threads. If you really want a 10" your best bet is fiberglass and you will want to watch the box volume carefully- I would put a high performance 8" against a shallow mount 10" any day. If I melt the voice coils on this sub I will buy a dual 4 ohm model to replace it, but so far it's working awesome with 500wrms at 1 ohm. I am honestly amazed by the sound quality and volume at this price point.

EDIT #2 11/29/22 ** I had to move to fuse #3. #3 and #6 are the only confirmed (at this point) switched in the cabin fuse panel. I was originally using #20 and my truck was fine a month, then started going into Deep Sleep almost immediately after the ignition was off. After switching fuses, I have only seen Deep Sleep twice and once was definitely after getting in/out of the truck a lot at a campout. **

You'll of course need a table saw, jigsaw, workbench, electrician pliers, double stick tape, spray glue, zip ties and other common tools.

(original post)
This is a work in progress, but someone asked me for dimensions so I decided to post now and update as I get it completed over the next 1-2 weeks. This is not a show truck. Let's just start with that, if you can do shop-quality work on your own you don't need this thread, and if you want a shop-quality finished product you should probably just have a shop build something custom for you.

Build components (added parts & pieces 10/11/22)
- Alpine R2-W8D2 8" sub $250
- Kicker Key 500.1 $270 (auto-gain and dsp at this price point blows my mind)
- Kicker CXARC remote bass level knob $40
- Metra Line-Out Converter and 1' RCA male-male cable $25
- Stinger dual 4/8 ga distribution with 8/10 ga output, - 1' Stinger red & black 8ga, local shop $50
- Scosche 4ga wiring kit w/60A blade fuse $25 (crazy good deal on Amazon)
- Stinger 10ga speaker wire already on hand but call it $15
- Recoil Add-on Fuse Holder 10A & 20A blades (I used 10a/10a in fuse #3) $10
- 4x8 sheet of 3/4" MDF $55 Lowes (this is enough to make 3-4 boxes at least)
- 40"x40" subwoofer carpet $15 (watch this video to install)
Honest total: $755
Quotes from shops ranged between $1800 and $3200, of course, their builds varied.
Time required: 16-20 hours (I'm a rookie, expert probably 4-6 hours)

I'm taking speaker-level input from the B&O 6x9, which I'll be disconnecting and removing. (EDIT 10/11/22 I disconnected it, but put it back because there's a big hole in the truck, see pic below.) The 6x9, bracket and plastic enclosure are considerably larger than the Kicker 500.1 so I'll be mounting the amp in that location. The amp does 150w @ 4ohm, 300w @ 2ohm, and 500w @ 1 ohm. Obviously, the sane thing to do would have been to buy the dual 4ohm sub and run it at 2ohm, but YOLO. If you don't have B&O the best way to interface is to get a harness adapter that taps into the ACM. And then you'll want a multi-channel amp but you could use another Kicker. The 200.4 and 500.1 together would be great and they're very small. If you don't have the B&O you may not realize how much depth is available at the bottom of the rear seatback. It's easily 4-5" deep.

My design goal was to not modify any metal and if I'm honest, I'm not an awesome carpenter so instead of building a trapezoid like Ken did over here I wanted to make it a very easy rectangle. There are numerous 10" woofer builds out there and if you look at them and make some of your own measurements you'll see that it's very, very tight trying to fit a 10" sub and grille even if you remove the plastic tray insert. There are a lot of high performance 8" available, I chose this one because of specs vs cost. Ideal sealed enclosure is only 0.3ft3 (gross excluding woofer volume), I'm actually slightly larger than that around .35.

There's 4 parts of the underseat inserts and you will want the outer pieces because otherwise it's very ugly and you would have a hole under the seat edge. But... do you really need the center piece? I built several cardboard mockups to find out what's workable.

With the tray (Ken's box and my mockup agrees) the bottom is only 7" wide because of the FITS inserts and the tapered trapezoid shape. If you pull the insert you can fit 10.5" wide at the bottom. In order to get it in there without cutting metal, I chose to make the box only 6.5" deep (tall). You could make it less than 10.5" wide and deeper, but I want the largest possible surface on the top side so that the woofer is not near the edge of the box. I noted that Ken's box is 16" long but due to the width of mine at the bottom (10.5 vs his 7) I shortened mine to 15".

More to come...

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[colinl]

Got the box built last night and it fits great as expected... carpet is next. I'm in my 40s and I've had systems in a number of vehicles, all done by shops. This is literally the first box I've ever built.

 

[MikeyG]

Looks good! Are you just going to trim the plastic around where the box will be?

 

[colinl]

Looks good! Are you just going to trim the plastic around where the box will be?

The 3 options I'm considering are:
1. Trim the plastic insert around the box, as you just said.
2. Cover the front of the bench with subwoofer carpet so that it's less noticeable where the navy plastic used to be visible when the bench is down. (See pic.)
3. Make a cover out of wood or plastic and cover with subwoofer carpet. This will look best, but I have no illusions about making something that looks professionally done.

 

[Thagh0st]

Are you going to add any cld for vibration and resonates or are you going to try and use the mass of the mdf for that?

 

[colinl]

Are you going to add any cld for vibration and resonates or are you going to try and use the mass of the mdf for that?

I've got a few sheets of dynamat on hand but definitely not enough to cover that whole area. Also a bit concerned about clearance, so I'll carpet the box first and then test the fit again.

 

[Thagh0st]

I've got a few sheets of dynamat on hand but definitely not enough to cover that whole area. Also a bit concerned about clearance, so I'll carpet the box first and then test the fit again.

I honestly don't think full coverage will be needed so much especially since it's dynamat, 60% should be enough if you got that much. Is it the dynamat extreme? Hoping you can fit it though as that's most important

 

[MikeyG]

The 3 options I'm considering are:
1. Trim the plastic insert around the box, as you just said.
2. Cover the front of the bench with subwoofer carpet so that it's less noticeable where the navy plastic used to be visible when the bench is down. (See pic.)
3. Make a cover out of wood or plastic and cover with subwoofer carpet. This will look best, but I have no illusions about making something that looks professionally done.

Yea that’s a tough call. I think if you just cut the plastic around the sub box so it still looks factory while the seats are down then maybe you can make a trim piece out of 1/4 wood and carpet to match the box to finish off under the seats so you don’t see what was cut.

 

[colinl]

I followed a video of a guy carpeting a box with spray adhesive and it worked pretty well. The fit is spot on.

I'm finishing the amp install and wiring tomorrow.

 

[Thagh0st]

I followed a video of a guy carpeting a box with spray adhesive and it worked pretty well. The fit is spot on.

I'm finishing the amp install and wiring tomorrow.

You did a absolutely beautiful job on that!

 

[colinl]

Hole-y crap. When the b&o sub is removed there's a hole straight through under the bed. Options are covering the hole with plywood or putting it back.

My amp fits in the center with one cable bracket relocated so I'm probably putting the 6x9 back.

 

[colinl]

Done and running. I like it a lot but I've never had an 8. Last system was a first gen JL 12W3 and this is not like that of course however, the system is very clean sounding.

I'll post up a full list of parts and get the cosmetics done the next week.

 

[colinl]

I honestly don't think full coverage will be needed so much especially since it's dynamat, 60% should be enough if you got that much. Is it the dynamat extreme? Hoping you can fit it though as that's most important

I'm still tuning and playing various music I'm familiar with, but so far there is little to no resonance from the rear under the seat or against the back wall.

There is resonance in the doors I'm noticing at very high volume playing bass guitar, probably 80-200hz or so. I have a set of Focal RCE Auditor 6.5 and I will probably buy more dynamat and take the door panels off again to cover everything I can. I think it's mostly the exterior panel, and not the inner plastic shell that covers the window mechanism and makes it all weatherproof. There's no resonance in the doors at moderate volume, luckily.

 

[Thagh0st]

I'm still tuning and playing various music I'm familiar with, but so far there is little to no resonance from the rear under the seat or against the back wall.

There is resonance in the doors I'm noticing at very high volume playing bass guitar, probably 80-200hz or so. I have a set of Focal RCX Auditor 6.5 and I will probably buy more dynamat and take the door panels off again to cover everything I can. I think it's mostly the exterior panel, and not the inner plastic shell that covers the window mechanism and makes it all weatherproof. There's no resonance in the doors at moderate volume, luckily.

That's definitely a great thing about the rear seat and back wall. Im not surprised about the doors, I had quite a lot of resonance when I had the audiofrogs in mine with higher volume. Nothing some cld and ccf foam didn't take care of though

 

[PDM33]

Great install man! Did you leave the factory amp in there for the front speakers? I thought about upgrading the 6x9 with something better but this seems like a better option.

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