DIY Under Seat Amplifier Install

[kyle2222]

I was looking for an inexpensive way to install an Amplifier into my 2008 Smart 4two so I could purchase the 8" under-dash sub from 4smartcar.com. This thread will describe how I accomplished this under $200 and less than a couple hours of work.

For some reason this forum won't let me post links or images until I post at least 3 times. This seems silly. Anyway, I'll go post some random stuff elsewhere and post the rest of my message shortly.

[kyle2222]

I was looking for an inexpensive way to install an Amplifier into my 2008 Smart 4two so I could purchase the 8" under-dash sub from 4smartcar.com (Smart Car Under Dash 8" Subwoofer Bass Solution).

I didn't want to mount behind the seats because I didn't want the Amp to be visible and didn't want to restrict seat movement. I didn't want to spend the $450+ for the Alpine PDX 4.100 so I went in search for small, low-cost 4 channel amplifiers. I came across the Sony XM-4S (Sony XM-4S Slim Series 4-channel car amplifier 50 watts RMS x 4 at Crutchfield.com) that was small and cost $135 w/free shipping from etronics.com. It is a class D amp with more than enough power for the smartcar.

Everything I used for this project:

Sony XM-4S Amplifier from etronics.com ($135)
1000W Amplifier install kit from Fry's ($29) [see picture below]
6' 14 gauge speaker wire from Ace Hardware ($4)
25' 18 gauge speaker wire from Radio Shack ($6)
Scrap mounting plywood from Home Depot ($1)
.5" L brackets from Ace Hardware to mount amp to plywood ($2)
Pack of buttmount crimp connectors from Radio Shack ($3)
Pack of wire taps (connect into 12V aux without cut) from Radio Shack ($2)
14" Industrial strength velcro from Ace Hardware ($4)
1 can of black spraypaint from Ace Hardware ($3)


I didn't want to remove the passenger seat after reading bad stories about airbag lights getting activated. I also didn't want to damage the car in any way -- I was able to do this entire project without drilling or cutting carpet. The only change I made to the car was cutting and splicing the speaker wires behind the stereo. After getting all the material it took about 2 hours to install the amp.

Amplifier mounted to a reverse pyramid plywood structure so it fits flat and snugly under the passenger seat:





Industrial strength velcro to hold it from sliding or otherwise moving:



Amplifier hookup kit purchased from Fry's:



How the cables are run under the passenger carpet:



Picture after install:



You can find information about how to splice the radio speaker connections over at Evilution UK Evilution - Smart Car Encyclopaedia:

(tap) A3 Black Grey 12v Switched
(splice) B3 Orange Speaker Right +
(splice) B4 Brown Orange Speaker Right -
(splice) B5 Green Speaker Left +, Sub pin4
(splice) B6 Brown Green Speaker Left -, Sub pin1

One cool feature of the XM-4S is the "speaker-level inputs with high-level sensing turn-on" which means the amp automatically turns on if the radio is turned on (without the ignition key).

Thanks to Evilution and all the other posters with information that made this possible!

Email me if you have any questions about this project.

[nonuro]

Excellent! I am going to change the radio myself but I don't have the confidence to do the amp.I think I can do it but I don't want to mess with the electronics.I have an MTX 702 amp and all the wiring kits etc. I am just waiting for the headunit(Kenwood dpx-503) to show up.

[vpkb1998]

Great install and finding of the amp. I'm looking for an amp that fit underneath the seat too, this Sony amp appears to be a great choice. What sub are you running, the JL that comes with the box?

[kyle2222]

Yes, I should have mentioned the other components used for my audio system are:

- Polk Audio DB675 front speakers Door Speaker Installation -- Shortcuts and Recommendations ($90)
- JL Audio 8W3V34 8" sub Smart Car Under Dash 8" Subwoofer Bass Solution (see above)
- LiquidAux to connect iPhone/iPod iphone and Smart? connected through/behind glovebox ($55)

The stock radio AM/FM receiver pretty much sucks (seems to be lacking midrange). I've never tried the CD player. However, using an iPod as the audio source (via LiquidAux), my audio system is very good at reproducing quality sound.

[headless]

Nice install there buddy, looks a neat job.
I too installed a Sony explod amp in my smart roadster, but there is no room under the seat as it is right on the floor, so I did the same as you and put velcro on the underside but put it upright on the bulkhead behind the seat, as I am a shortarse I don't need the seat all the way back anyway, so it is no problem, and I installed 2 10inch Sony explod subs in the rear trunk, sounds awesome.
the standard smart ICE is only good for throwing in the trashbin.
Ellis

[Jet Pod]

Is there any reason why I've not seen an installation with the amp under the drivers seat? Seems if you removed the premium sub you'd have the same amount of space. Is it a wiring issue?

[cubefx]

Originally Posted by wblumberg97

Is there any reason why I've not seen an installation with the amp under the drivers seat? Seems if you removed the premium sub you'd have the same amount of space. Is it a wiring issue?

There is much less space under the driver seat then under the passenger.

[AcePlatero]

very clean install!

[NeWave]

Originally Posted by Jet Pod

... Is it a wiring issue?

Plus, it's less hassle to run the wires under the carpet directly between the amp and the sub. And the battery is right there in the passenger footwell where you'd need to connect to anyway.
The only thing I have left to (still) do is secure my amp down so it doesn't go flying when I slam the brakes.... Sounds great though.