Audio Build: Kicker 6.75" Subwoofers in Rear Doors

I've been upgrading my car audio since I was sixteen (almost a quarter of a century ago) and have been looking forward to improving the sound of my Tacoma. Have read most of the Premium Audio for < $250 thread, but one of the things I really wanted to try and create was tight bass you can feel in your chest. Not sloppy, nothing rattling, just punch that accentuates the low end of music (which for me is mostly rock and alt. country). So $250 didn't seem possible. Also, while I have done all my own installations in the past, including designing and building my own subwoofers, that was all in the pre-kid era, and I have the good fortune of living in Charlottesville, Virginia, the home of Crutchfield. So, for this one, I had someone else do the build.

The biggest dilemma for me was what to do about bass, which is really a problem unique to pickup trucks. Everyone on TW seems to put a box behind the seats but based on my experience, that's not going to sound very "clean" - there has to be distortion as the low frequency sound waves penetrate the back seats (and in my case, the car seats as well). I thought about building a box and just dropping it on the ground behind the driver seat but would rather not because my kids will trash it. Then I stumbled upon these Kicker 6.75" subwoofers and wondered, could I remove the back door speakers and replace them with subs?

Before everyone tells me I'm an idiot, I know - a subwoofer is designed to be in an enclosure of a specific volume, and I strongly prefer sealed enclosures (tighter, cleaner sound, albeit less volume) over ported enclosures. But I talked to the guys at Crutchfield and they said they've done this before - apparently with appropriate placement of Dynamat as well as possible use of a mounting gasket (in my truck they didn't need it, for Nissan Titan HD they apparently do), you can get a SOMEWHAT air tight seal around your rear door speakers. So I decided to do a science experiment - I asked them to install these Kicker subs in my rear doors using the methodology they proposed. If it sounds great, I will be done. If it's inadequate, I'll bite the bullet and build a removable, kid proof subwoofer to sit behind the seat (95% of the time I drive alone anyway), and will just turn the gain down use these for fill.

Here is everything I went with and why:

Front Doors / Dash: Polk Audio DB 6502 component speakers with silk dome tweeter. I think the metal coated tweeters, in general, sound a bit harsh, but that's my personal opinion. My previous car (Subaru) had a set of Polk components and they were breathtaking. Yes the front door is actually 6x9, if Polk made some 6x9 components I would have gotten them, but these fit with a mounting bracket and the loss of bass going from 6.5" to 6x9 is trivial. Aesthetically it's irrelevant because they're black and hidden deep in the door. The tweeters can be mounted in the dash using a backstrap that Crutchfield provides

Back Doors: Kicker CompRT shallow-mount 6-3/4" subwoofer - what I am trying (hoping) to achieve is quasi-sealed back doors that will produce clean, tight bass at low volumes for the kind of music I listen to. If not, I'll just use them as fill.

Amplifier: Pioneer GM-D9605 5 channel amp - went with the 5 channel in case the back door subwoofer experiment is a failure. Of note this amp has HFP and LPF on all channels, not all amps do - the LPF is important if you are going to try and run subwoofers in your back door. For those who want an amp under the seat - Crutchfield measured my seats and felt that it was too close to fit the GM-D9605 under the seat, so it's going behind the back seat (driver side, to leave space for possible stealth box in passenger side)

AudioControl LC6i - I've never used one before but the reviews on both Crutchfield and Amazon are amazing and my understanding is that this will significantly improve sound quality over the cheap adapters you might otherwise be tempted to buy. The LC7i has "bass restoration" which I didn't think was necessary since I have an amplifier with bass gain on it

Dynamat x 4 doors - the main reason I did this was so that the Crutchfield installers could use it to try and "seal" the back door speakers in a quasi-enclosure.

Maybe one day:

Option B: make my own subwoofer if the Kickers in the back door are inadequate. This sub would be based on the JL Audio 8W1v3-4 - goes down to 25 Hz, middle of the pack sensitivity (85 db), and requires a stingy 0.35 cubic feet of space. I could make something pretty unobtrusive

Option C: JL Audio Stealth Box. I can't imagine this will sound the way I want if it's stuck behind the seat, and for ~ $800 I'm not willing to do that science experiment. But if worst comes to worst I might trial it, if that is possible

Results: I am very pleased with this upgrade. Not only do I have clear high/mid range from the front, I'm getting a very reasonable amount of bass from the back and I like the acoustic imaging that occurs when the lower frequencies coming from behind the seat. No detectable rattling in the back doors. Songs that I use to gauge bass include:
White Stripes: Ball & Biscuit
Band of Horses: Wicked Gil
Explosions in the Sky: Welcome Ghosts
Neil Young: Down by the River
My Morning Jacket: Evelyn Is Not Real
Alejandro Escovedo: Wave
REM: Country Feedback
Lucinda Williams: Car Wheels on a Gravel Road
CCR: I Put a Spell On You
RL Burnside: Glory Be

I am still tweaking the HPF/LPF and I will post a picture of the settings when they are optimized. I will say that there isn't as punch as my previous vehicle, a Subaru Outback with 2 x 10" Kenwood subwoofers in a sealed enclosure located in the trunk with its own dedicated amplifier. Obviously two 6.75" door subs that are not truly sealed are not going to produce the same volume/quality of bass response (also they only get 75 RMS whereas a dedicated subwoofer channel will put out ~ 300 RMS [which would probably blow the panels off the door]). For that reason, I have decided to go ahead and build my own subwoofer to sit behind the front seat based on the JL Audio 8W1v3-4 (I was spoiled by my previous vehicle). But... for those who want to really accentuate their bass and don't want to put a box behind the passenger seats, I think this is a really good option.

Lastly, I have asked Crutchfield to send me pictures of the installation of the subs in the rear door and the way they put the Dynamat in. They took some photos for me, just haven't sent them to me yet, I will post as soon as I get them.

 

This sounds very interesting, I am looking forward to seeing your pictures! Thanks!

 

sub'd

 

This sounds intriguing! In for pics!

 

Here are the pictures of the subwoofer installation in the rear door (installed by Crutchfield)! I've been listening to this setup for over a week now and to be honest am not even sure if I'm going to a dedicated subwoofer. Extremely pleased with the quality of the sound and the fact that everything is contained in the doors.

 

I think I'm going to just copy your exact setup, I just did the cheap kicker tweeter upgrade and all it did was leave me desiring more...

This is great thanks for sharing!

 

Subbed...no pun intended!

 

Like the write up, love the user name and avatar pic!

 

Most sub setups in cars are in trunks. Low frequencies don’t distort too much. You would need to do a custom mold to get some more space, I still don’t think the door is a good place for that much vibration. My taco tunes sub setup sounds great. All my door speakers and tweeter are powered off the stock HU and sounds good too

 

i went went the rockford 360.3 processor two set of t2 6.5 components , t1 600x4 , and a t1 500 x1 which pushes constant 750 to t1s1 10inch

 

Nice!! This is similar to what I'm in the process of finishing. I'm running kicker subs in the rear door and the rest of the speakers from the Premium Audio for < $250. I have an LC7i and Kenwood amp that I need to get around to installing and wiring. I'm planning on mounting the amp and LC7i under each front seat, where did you mount yours?

As you stated, I just want to accentuate the bass...not looking for a dedicated box sub.

 

Crutchfield put my amp behind the left rear seat - they didn't feel there was enough clearance under the driver seat when they put a "dummy amp" under there. They did but the LC6i under the passenger seat, that fit fine (much smaller). Will be curious to hear what you think about the sound after you have had some time to play with it. One thing I noticed is a real improvement when I relaxed the filters a bit, i.e. there is a fair amount of overlap between the high pass filter going to the front speakers and the low pass filter going to the back.

 

the guys the put my sub did 1/2 ass , took the whole pocket out of the back behind the seat , which i wanted to keep in really takes away from the look of the RF sub , thinkin of fabing up my own box kinda like taco tunes or oem does

Been awhile had them re-do with another box and ten

 

Cool idea thanks for sharing

 

thanks for sharing your setup. I wonder if I could manage to seal both back doors as yours was done? Anything special installed aside from the dyna seal? looks like they wrapped it into the enclosure and behind the subs.

 

This is exactly what I want to do for 2018 DCSB. I want to get a seat delete going and the goose gear stuff gives an option with no sub back there and we gain a ton space for the doggos (2 Vislas and a Weim) to be setup there. One of the big sticky posts here on the forum is the Audio / Visual DIY and this really detailed post about deadening the truck that looks pretty in depth. Is there anything special on trying to "seal the door" (btw total audio beginniner here) for the sub you put in it?

 

I got that same sub in the 12” version not to bad and I’m under powering it. I don’t know tho you seem like you might have at least a lil basshead in you , let us know when you get the Sundown X8 setup and yes Crutchfield they where really pioneers in marketing more than anything else and when the internet came along it was a perfect marriage and boom, I used to go to the store there all the time and drool at stuff I couldn’t afford back in the late ‘80s.

 

Any video?

 

I had no idea Crutchfield actually did installs.