Budget/Low-tech way to secure a sub box in a Civic Si Coupe

[rhuel]

I pulled my amplifier and subwoofer box from my 350Z last year when I bought my 2019 Civic Si Coupe and am just now getting around to installing them.

One of the hold-ups was trying to figure out a way I could secure the box yet still allow me to remove the sub if I needed all of my trunk space.

So, an idea came to me the other day while chatting with a friend...an interior door hinge from a house.

I attached one side to the back seat and the other to the back of the subwoofer box. When I need my trunk space, I can either lay the rear seat down with sub box still attached or pull the hinge pin and remove the box altogether.

The box is dusty from sitting on a shelf for a year and the hinge needs painted black. Otherwise, it fits, it's secure, and works exactly as I hoped.

Easy on the flames on the box size for the sub and all the rest. I know it's too small. If you've ever seen a 350Z stock Bose Sub location, this is the max size box that would fit in that space, even after some modification to the space. I'm not looking for SPL competitions here, just reusing some old gear on a new car. It'll be fine.

I haven't yet mounted the amp or finished the wiring. I just have the power cable run into the trunk from under the hood (wired to battery and fuse holder mounted, but no fuse installed as I don't want a hot wire in the trunk just yet) to the trunk until I figure out exactly where I'll put the amp. thinking about carving some of the "spare tire area" foam to make the amp fit.

 

[IByrdl]

I haven't yet mounted the amp or finished the wiring. I just have the power cable run into the trunk from under the hood (wired to battery and fuse holder mounted, but no fuse installed as I don't want a hot wire in the trunk just yet) to the trunk until I figure out exactly where I'll put the amp. thinking about carving some of the "spare tire area" foam to make the amp fit.

Do you plan to use an LC2i or just the high level inputs from the front speaker on the M500?

Please post an update when you finish the install! I have the same amp and going to be doing my install next month with a buddy. Curious where you end up putting it and if under the false floor like that would cause overheating or melting of the foam.

My box is significantly bigger for my ported 12" so I'm going to try extreme strength velcro to hold it in place.

 

[rhuel]

Do you plan to use an LC2i or just the high level inputs from the front speaker on the M500?

Please post an update when you finish the install! I have the same amp and going to be doing my install next month with a buddy. Curious where you end up putting it and if under the false floor like that would cause overheating or melting of the foam.

My box is significantly bigger for my ported 12" so I'm going to try extreme strength velcro to hold it in place.

This amp has built-in sensing for remote turn on using high level inputs and I used the factory subwoofer wiring for those high level inputs. I'm not an audiofile with test equipment to see what frequencies are being sent/filtered through the rear sub wiring.

I cut back the factory loom a couple inches and then cut the pink/white wires for the sub and soldered in two new wires, shrink wrapped, and added loom to those and routed to the driver's side of the car along the rear seat latch pull cable and then down behind the driver side trunk panel, zip tying a few places along the way.

I ran this same setup in my 350Z for almost 7 years and the amps (had a 4ch as well) would get warm, but never clipped or cut-off. The amps were installed in a pretty tight space in that car.

I've only run this car for maybe 30 minutes total with the music up pretty loud and the amp never cut out. It hasn't melted the foam at all so far and I don't expect that it will for as much as I use the car and crank the music.

I ended up using a circular saw and medium sized pocket knife to cut out a section of the foam closest to the trunk latch area to make room for the amp. I had the deck set a bit too low and nicked the foam on my first cut. You can see that line in the one picture.

The holes didn't drill nicely through the foam, it pretty much just tore out little bits as I drilled, but it's hidden and I'm not that concerned.

I used the "spare tire" center tower bolt hole as my ground. You will need to cut some foam to accomodate any wires that are left under the foam or just know that the foam will not sit 100% flush in the spare tire well.

I had to adjust the amp's gain down from how it was set in my Z. Not sure if that's because I ran RCAs from the Z's H/U vs. taking the high level inputs in the Si, but it was waaay too boomy for my taste. Gain is right at 50% and I can adjust up or down using the H/U's Subwoofer slider from the Menu>Sound option.

Hit me up if you have any other questions. Good luck on your buddy's car.

 

[IByrdl]

This amp has built-in sensing for remote turn on using high level inputs and I used the factory subwoofer wiring for those high level inputs. I'm not an audiofile with test equipment to see what frequencies are being sent/filtered through the rear sub wiring.

I cut back the factory loom a couple inches and then cut the pink/white wires for the sub and soldered in two new wires, shrink wrapped, and added loom to those and routed to the driver's side of the car along the rear seat latch pull cable and then down behind the driver side trunk panel, zip tying a few places along the way.

I ran this same setup in my 350Z for almost 7 years and the amps (had a 4ch as well) would get warm, but never clipped or cut-off. The amps were installed in a pretty tight space in that car.

I've only run this car for maybe 30 minutes total with the music up pretty loud and the amp never cut out. It hasn't melted the foam at all so far and I don't expect that it will for as much as I use the car and crank the music.

I ended up using a circular saw and medium sized pocket knife to cut out a section of the foam closest to the trunk latch area to make room for the amp. I had the deck set a bit too low and nicked the foam on my first cut. You can see that line in the one picture.

The holes didn't drill nicely through the foam, it pretty much just tore out little bits as I drilled, but it's hidden and I'm not that concerned.

I used the "spare tire" center tower bolt hole as my ground. You will need to cut some foam to accomodate any wires that are left under the foam or just know that the foam will not sit 100% flush in the spare tire well.

I had to adjust the amp's gain down from how it was set in my Z. Not sure if that's because I ran RCAs from the Z's H/U vs. taking the high level inputs in the Si, but it was waaay too boomy for my taste. Gain is right at 50% and I can adjust up or down using the H/U's Subwoofer slider from the Menu>Sound option.

Hit me up if you have any other questions. Good luck on your buddy's car.

Looks clean! Thanks for the update man. It's also my car haha. He's a huge car audio nerd so he's gonna make sure I get everything set up correct and cleanly.

 

[rhuel]

Looks clean! Thanks for the update man. It's also my car haha. He's a huge car audio nerd so he's gonna make sure I get everything set up correct and cleanly.

Do note, the tray does stick up just a bit as the amp is a bit taller than than the surrounding foam. I debated using the area I did knowing the amp would sit too high vs. using the more forward area to the left which was much deeper. I figured the ease of cutting the area I did and living with the "too high issue" was a better solution than trying to hack through a much larger section toward the front or having the amp sit at an angle.

The easiest solution would be to use the cubby where the tire inflator lives. The downside to that was the adjustment screws are not easily accessible and where to put the inflator? I didn't want the inflator sliding around behind my seat and I didn't want to take it out of the car, so it stayed put and I cut the rear section out.

Mods are usually all about compromises...cost, effort, fitment, time...

Oh and a 12"...that is going to be eyeball shaking for sure.

Back in the early 90s I had a 1981 Civic 1300DX with two 12s (Pyle) and then moved and upgraded the system to a 1985 VW Golf hatch with a pair of 12s (Orion XTR - still have the subs in a different huge box) and it was thunderous. Too much boom for my old ears (and head) now. I just like a bit more bass/hit than the factory sub provides.

Best of luck to you on the install in YOUR car...missed that bit the first read.

 

[IByrdl]

Do note, the tray does stick up just a bit as the amp is a bit taller than than the surrounding foam. I debated using the area I did knowing the amp would sit too high vs. using the more forward area to the left which was much deeper. I figured the ease of cutting the area I did and living with the "too high issue" was a better solution than trying to hack through a much larger section toward the front or having the amp sit at an angle.

The easiest solution would be to use the cubby where the tire inflator lives. The downside to that was the adjustment screws are not easily accessible and where to put the inflator? I didn't want the inflator sliding around behind my seat and I didn't want to take it out of the car, so it stayed put and I cut the rear section out.

Mods are usually all about compromises...cost, effort, fitment, time...

Oh and a 12"...that is going to be eyeball shaking for sure.

Back in the early 90s I had a 1981 Civic 1300DX with two 12s (Pyle) and then moved and upgraded the system to a 1985 VW Golf hatch with a pair of 12s (Orion XTR - still have the subs in a different huge box) and it was thunderous. Too much boom for my old ears (and head) now. I just like a bit more bass/hit than the factory sub provides.

Best of luck to you on the install in YOUR car...missed that bit the first read.

How thick is the foam where you have it mounted? Thick enough to cut out a drop so the amp sits lower?

 

[rhuel]

How thick is the foam where you have it mounted? Thick enough to cut out a drop so the amp sits lower?

I think it is thick enough, only need about 3/8" - 1/2" to make it flush, but I wasn't sure how I'd neatly get a flat surface that didn't look terrible - the foam doesn't cut smoothly like wood.

 

[IByrdl]

I think it is thick enough, only need about 3/8" - 1/2" to make it flush, but I wasn't sure how I'd neatly get a flat surface that didn't look terrible - the foam doesn't cut smoothly like wood.

Gotcha, I wonder if an aggressive sandpaper on a sanding wheel would work to shave it down? We'll try and figure out something.

 

[rhuel]

Gotcha, I wonder if an aggressive sandpaper on a sanding wheel would work to shave it down? We'll try and figure out something.

Wanted to let you know the specific amp I used. Not sure if yours is the same one. Alpine MRV-M500 wiring/features might be different.

 

[IByrdl]

Wanted to let you know the specific amp I used. Not sure if yours is the same one. Alpine MRV-M500 wiring/features might be different.

Yeah that's mine too.

 

[Conika]

Hey guys, quick question for someone who is about to add an Alpine MRV-MR250 and sub to my stock Si System. I plan on upgrading the 4 6.5 speakers and running them off the factory amp, however I was planning on using my Alpine 250 and a kicker sub that is rated for it. My main question is it appears the MR250 does not have auto remote turn on signal sensing from the speaker level input like the 500 model. I wanted to know if anyone with the factory amp knows if there is a remote turn on wire for the factory amp, or do i have to run a remote turn on wire ALL the way to the head unit. From what I understand the factory amp is in the back seat near the trunk and that would be far easier to tap into.

 

[IByrdl]

Hey guys, quick question for someone who is about to add an Alpine MRV-MR250 and sub to my stock Si System. I plan on upgrading the 4 6.5 speakers and running them off the factory amp, however I was planning on using my Alpine 250 and a kicker sub that is rated for it. My main question is it appears the MR250 does not have auto remote turn on signal sensing from the speaker level input like the 500 model. I wanted to know if anyone with the factory amp knows if there is a remote turn on wire for the factory amp, or do i have to run a remote turn on wire ALL the way to the head unit. From what I understand the factory amp is in the back seat near the trunk and that would be far easier to tap into.

You shouldn't need the 12v remote wire. I checked your manual and it says the same thing as ours for the remote wire. But, it's easy enough to add if necessary.

The factory amp uses fiber optics to get it's signal from what I've read here so no chance of tapping a remote from the HU, and it's also behind the passenger door kick panel I think. It's easy to run a 12v wire along with your amp power cable. I used an add-a-fuse in my old car for the 12v. Just tap into one of the accessory fuses with that, I am currently using the bottom left 'ACC' one for my radar detector. It doesn't send signal when the car is off.

Here's the one you'll want, https://www.amazon.com/Circuit-Blade-Style-Profile-FUSETAP/dp/B00K17A2E6/

This amp has built-in sensing for remote turn on using high level inputs and I used the factory subwoofer wiring for those high level inputs. I'm not an audiofile with test equipment to see what frequencies are being sent/filtered through the rear sub wiring.

I cut back the factory loom a couple inches and then cut the pink/white wires for the sub and soldered in two new wires, shrink wrapped, and added loom to those and routed to the driver's side of the car along the rear seat latch pull cable and then down behind the driver side trunk panel, zip tying a few places along the way.

Were you aware that on the amp the HL inputs are only specced up to 10V? Another thread said the factory sub can see well over that, I wonder if that's what's causing the boomyness you described. They recommended tapping into the front speakers instead of the subwoofer to use HL inputs on our amps.

My plan is to tap into the front L/R next to the factory amp and run it down the passenger side to the trunk. The subwoofer adjustment in the HU won't work but I installed the Alpine RUX knob in the blank switch next to the steering wheel.

 

[rhuel]

You shouldn't need the 12v remote wire. I checked your manual and it says the same thing as ours for the remote wire. But, it's easy enough to add if necessary.

The factory amp uses fiber optics to get it's signal from what I've read here so no chance of tapping a remote from the HU, and it's also behind the passenger door kick panel I think. It's easy to run a 12v wire along with your amp power cable. I used an add-a-fuse in my old car for the 12v. Just tap into one of the accessory fuses with that, I am currently using the bottom left 'ACC' one for my radar detector. It doesn't send signal when the car is off.

Here's the one you'll want, https://www.amazon.com/Circuit-Blade-Style-Profile-FUSETAP/dp/B00K17A2E6/

Remote turn on would just require any switched power if the amp won't turn on with HL inputs (looks like it should, though). My amps (had a 4ch Alpine, too - left in the Z) both came with that pigtail for the HL inputs. Check your box, it's probably in there.

Before I finished my install, I ran wires outside the car from battery for power and ground and made some pigtail wires I could connect to the sub's OEM connector then ran wires to the sub just to ensure everything would work as I expected before I started cutting/soldering/hiding wires. Everything worked perfectly, so I finished the install, buttoned everything up and hit the ignition. It all worked perfectly.

I used the blade-type add-a-fuse when I installed my auto dimming rearview mirror with compass and it worked great. You probably won't need to do that, but if you do, it's very simple to connect.

I wasn't aware of the voltage difference. I had the door panels off the weekend prior doing a chrome delete (pulled mirrors and window channel - made it sooo much easier). Oh well, it sounds fine as-is. I hope there are no negative consequences down the road. I'll cross that bridge when I get there

I considered the RUX knob in my Z, but found I didn't really need it. The H/U sub control does the job when I do want to adjust.

 

[Conika]

You shouldn't need the 12v remote wire. I checked your manual and it says the same thing as ours for the remote wire. But, it's easy enough to add if necessary.

Dude awesome catch. That is a relief. Im trying to do as little work as i can so if this is true with the speaker level input then that amazing. I will update you once i get it all installed. Thanks again for your help.

 

[rileyj98]

I have a 12” sub with an enclosed box for it chilling in the trunk, slapped some Velcro on the bottom so it doesn’t slide and then a blanket in between the sub box and the top of the trunk and it holds it perfectly! Before I would go for a spirited drive and it would be on its side and in right against the trunk lid lol thank god I had the audio installer leave a lot of slack in the cable otherwise it would have ripped itself free lol

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