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Under Seat Subwoofer

19K views 6 replies 4 participants last post by  arcticscythe 
#1 ·
2013 Subaru WRX Hatch, Satin Pearl White
Cobb Tuning SF Intake + SF Intake Box Black Stage 1+ OTS
Whitelines Anti-Sway Bars, Kart boys Endlinks, Back to black bushings.
Cobb Knob, Roof Rack, Gorilla Flaps, LED Light Bars, Bike Rack
91 Octane Shell fuel

Preface
So I am currently and for the next 3 months working on a large project that forces me to come into work and leave at the peak of rush hour traffic. With spring break over traffic has only increased and I am currently spending between 2.5 and 3.5 hours a day sitting in my WRX in first gear inching along my 24 mile round trip. I’ve been exploring audio books and radio stations but I feel like my radio is severely lacking. Especially in the low and mid tones so I set out to find a small subwoofer that wouldn’t take up a huge amount of space. I am also not ready to invest thousands of dollars replacing the factory head unit, amplifier, door speakers and essentially pull up every panel in the car to rewire a new system. It is definitely something I am comfortable with but its currently not in my budget. I am aware that Subaru offers a factory installable unit that fits under the seat but that unit is very pricey, $350 quoted from my local dealership and it is only pushing 64W RMS power on a 6 inch driver.

My criteria for a new subwoofer to fill the mid/low are as follows - Low profile ( needs to fit under the seat like the factory option), Needs a speaker level input ( I don’t want to add a line converter that could add extra noise to the signal or replace my head unit ) Must be phase adjustable ( because it is so close to the front and rear speakers), Needs to be powered ( amp and subwoofer built into one box to keep things clean ), Needs to have removable remote level control.

The Contenders
Sound Ordnance B-8PTD - Kicker Hideaway - Pioneer TS-WH500a - Kenwood KSC SW11

The winner
Crutchfields house brand - Sound ordnance B-8PTD. With the best reviews of all the options I found that would fit nicely under my passenger seat and with the greatest number of positive reviews as well as a 2 year warranty I am pleased to have ordered the B-8PTD. It is 125W RMS 250w MAX 8 inch subwoofer with a decent frequency response and auto-on high level inputs. It comes with a remote level knob and phase adjustment. Coming in at $150 shipped I couldn’t beat the price. for the feature list. The Kicker was over powered for my current configuration at 300W and the Pioneer was a bit too long to fit nicely. The kenwood would have been a nice option but at twice the price there were no benefits other than a slightly higher sensitivity.

The Install
So the intention of this install is to keep everything looking as stock as possible while increasing the low end of the audio system. Everything should be well hidden and run as clean as possible without sacrificing the little audio quality available and without creating unwanted rattles or squeaks. The install was 4 parts, Speaker level wiring, Power line, Ground line and 12v accessory( remote )

For the speaker level wiring I choose to tap into the factory harness rather than use an aftermarket harness adapter because the factory harness is so accessible with the head unit removed. I used 4x 18-22ga squeeze type wire-tap splices to connect the factory front left and front right speaker output I tested Each line with a 1.5V AA Alkaline battery by testing the pinout I found on another website. The pinout I used was from the website Subaru radio and radio wiring harness information. After attaching the first part of the splice I used 18x4 In wall speaker wire from my local hardware store to make a single wiring harness for the high level inputs. I followed th right side of the center console down and out of a factory hole in the carpet under the seat. I did have to loosen my seat rail bolts to get enough room for my hands to fit under the seat carpet but I did not need to completely remove the seat. In hindsight that may have been a better option.



For the Power wire I Used a length of Red 8 gauge boss wire that I had from my old geek squad days. I found 2 unused grommets in the firewall behind the intercooler. When I removed the grommets I was greeted with latex foam and carpet that was very difficult to access. I tried pushing a ball point pen through as to not damage any wires that might be on the other side to no avail. Eventually I decided to use a ⅜ drill bit and turn it by hand to slowly remove the latex and carpet without damaging any components behind the firewall. That was not a position I could take photos but I was able to open enough space in the foam and carpet to feed through my 8 gauge wire. I wrapped the wire in vacuum hose and zip tied it along the top of the firewall with the other harness parts with similar covers I installed a Boss 50A fuse in the 12V line from the battery about 6 inches from the battery. For the 12V accessory I tied into my existing accessory add a fuse power distribution block It was as easy as loosening the existing connections and wrapping a blue 12V remote wire in the connector.







All 3 wires were run down the passenger side of the transmission tunnel under the carpet, they all exit the carpet under the passenger seat and they are all wrapped and awaiting the arrival of the subwoofer. More writeup when the subwoofer arrives later this week.

 
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#2 ·
I have the same unit installed in my 06 and I am quite pleased with it. I wasn't expecting much out of an 8 inch, but being right beneath the seat helps. Only issue I ran into was the underseat vents for the rear passengers forces the sub to stick out from under the seat in the rear an inch or two (don't know if the 13 has a different vent). So far no one has kicked any knobs off though ;)

My buddy had an old HU lying around, so I was able to plug into the internal sub remote connection which was really nice. I have mine paired with some 3 ways in the front doors powered by a small Clarion 4x75W RMS amp mounted under the glove box. (Waiting for the amp to blow the rear doors before I upgrade) Install of all these was a cinch and so far have no complaints!

And now I have some interesting looking desktop speakers! (old fronts)

Can't wait to see the rest of your install!
 
#3 ·
Awesome write up! I will be using this when I finally decide to pull the trigger myself.
What differnece in wireing would be needed if you used two, one under the drivers seat and one under the passengers seat?
I know I dont need one on either side and from a weight distribution standpoint it makes almost 0 difference, but its a symmetry thing for me. Im wierd like that FOL.
 
#4 ·
I share your minor obsessive compulsive tendency. I actually have a tool set under my drivers seat and until yesterday I had a matching socket set under the passenger seat...

If you were to wire this for 2 systems I would run one set of wires to a central "hub" like a distribution block. From there you could split your 2 speaker level inputs, your power and even use the same ground. They are not designed for automotive use but I have used 4 position screw terminals as distribution blocks for a number of projects in the past. they have metal plates and are mounted on nylon so your install should look very clean. Ive even purchased the models designed for sprinkler use and they have nice silicone covers with water tight shielding.

Assuming you choose the same path as me for your power wire you would want to upgrade from an 8-10 gauge power line to a 6-8 gauge line as well. You will be carrying 40-50 amps at max power rather than the 25 amps for a single powered subwoofer unit.

When your ready to do it shoot me a PM and Im glad to help you map it out.
 
#5 ·
** Subwoofer arrived in the mail yesterday **

Unboxing - The subwoofer cam packed in 3 boxes, Each with their own protective material. It arrived very safe. That said the remote volume control knob was scuffed because it was packaged in the same bag as the other accessory hardware. Luckily the only marks were on the top surface and that was going to be taped out of the way anyway.

Remote volume knob - The subwoofer package came with a remote volume/level control knob. It connects to the subwoofer using RJ23 ( 4 pin phone jack ) connectors. I ran the line through the rear of the cubby under the carpet and met with the other wires I had run previously for the install. I used 3M VHB double sided foam tape ( the same tape they use to keep the windows on buildings in dubai ) to attach the remote level knob to the top of the cubby.



Subwoofer Power - Having all the cables run from earlier this week made the actual part install very quick and easy. I began by selecting ring terminals that were the best fit to the subwoofer and trimmed the size one larger for the 8 gauge wire. I attached the ring terminals with wire crimps and heat shrinked the whole installation for my own piece of mind. I used a 22 gauge ring terminal for the 12V accessory line and heat shrinked it blue because i had blue lying around the garage.



High Level HarnessI built the high level harness by soldering the 4 lines that were spliced into the front speakers to the designated wires from the harness. I Head shrinked those wires and wrapped them all in a spare piece of vacuum hose. You can see it complete in the image above on the right side of the subwoofer.



TuningAfter connecting all the lines to the subwoofer ( and putting the fuse back in the 12v line from the battery ) I powered the system up. I set the stereo to 50% volume and the remote level knob to 50% and began tuning the system. I started with all the settings at 50% except the phase selection which stayed at 0. I played one of my favorite test tracks, Caribbean Blue by Enya and it sounded pretty good with everything set to the middle. That said that is no way to tune a system so I grabbed a tone sequence from youtube and handled the crossover first. I have the crossover set somewhere around 140Hz because that is where the door speakers started picking up the signal. above 140 it sounded muddy. I also tested the phase selector back and forth at 140hz and it definitely sounds better at 0. I lowered the Bass EQ ( bass boost ) to 3dB and dropped the level to 0. Now testing with 60Hz tones I slowly raised the level until I could just start to feel the bass. I had a friend lower the remote volume knob to about 25% and raised the level further. It is currently set to about 40% and it is low enough that when the remote volume knob is turned all the way down the subwoofer is totally silent, when the remote volume knob is all the way up it doesn’t get muddy. Just for my own knowledge I ran a few tests with lower tones and the system does not produce tone below 30Hz, It starts working around 35 and sounds fantastic at 40Hz. Time to play with actual tracks.

Music TestEverybody has a different taste in music, I tried to grab a sample of songs to test with so that I could give an accurate review across the spectrum. Following are the tracks I choose and my notes. I started with the subwoofer volume level at 50% and the head unit volume at 20 ( 50% of max ) and increased head unit volume to 75% during the playback. For these tests I left the subwoofer remote volume adjustment at 50% unless it started sounding poor.

Lindsey Stirling - Roundtable Rebel - The electronic bass sounded very clean and the violin was not overpowered by the subwoofer level.
Hanz Zimmer - Pirates of the Caribbean End Credit Some fo the notes were still missing from the very bottom end. Nothing that you would notice if you were casually listening to a track but the large tyco drums were absent. The stock head unit may have filtered them out or the speaker level outputs may not have included notes that low.
Enya - Caribbean Blue - Clean and rich throughout the volume range.
Eminem - Not Afraid - Bass hits hard enough to sound like a real system but not loud enough to rattle windows. It adds a dimension of tactile response. Rather than just hearing a song you can feel the music. The subwoofer was struggling a bit at the top of the volume range
Foo Fighters - Pretender - The subwoofer reproduced the drums well but it needed more punch. Increasing the subwoofer volume level to 60% helped with the speaker levels at 20 increasing the speaker levels forced me to take volume off the subwoofer.
Nuttin But Stringz - Thunder - Low bass notes were clean but the subwoofer volume was very low after adjusting the subwoofer volume to 75% everything sounded great.
Nero - Welcome to reality - The electronic bass notes hit clean and hard with the volume set to 20 on the head unit. When I raised the volume on the head unit it started to get muddy and I needed to adjust the subwoofer level knob down to about 40%. I could feel the notes hitting my chest but it didn't overpower the rest of the track.

Final notes - For the $149 I spent on this setup I could not be happier. My stereo was lacking middle and bass notes and this small under seat subwoofer added the bass that was missing. It is not a replacement for a 12-15 inch subwoofer and it cannot hit the 10-20Hz super low notes but it fits under my seat without taking up any storage space and it sounds great.

TLDR SO B-8PTD powered subwoofer fits under the seats, sounds great and was easy to tune for my tastes.
 
#7 ·
I appreciate it. This forum has been a place for me to learn and spread my knowledge.

You do not truly know anything until you have taught someone else how to do it better than you.

Ill keep the write ups coming as long as there is a budget for the Subaru.
 
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