Is it possible to replace the 8" JBL sub and add an amp w/o making big changes?

So Im about to install a replacement ub for the factory JBL 8" with a pioneer shallow 8" sub and for the map i'm going to use a kenwood amp ....question is, should I put the amp under one of the seats and wire it to the sub or put it in the back seat cubby hole on the driver side rear seat? I want to make it look as stock as possible ....replacing the sub and ampliflying (sp) it from another source than the oem jbl amp. I have seen the thread about how to replace the speaker but not an amp replacement ...anoyone out there done this?

 

Are you planning on putting the new sub in the existing factory enclosure? Or are you starting over with a new enclosure too?

If you are are using the existing plastic enclosure, this thread from another forum might help (sorry for posting a thread from "competing" a Toyota forum):

http://www.toyotanation.com/forum/showthread.php?t=161803

If you are going this route, I would build some kind of simple mounting panel for the amp (such as a piece of MDF or plywood covered with carpet or spray-on rubberized sound deadener available from an auto parts store)...just find a place next to the existing enclosure behind the rear seat and fasten the panel to the rear wall of the truck with bolts or cable ties or something. And then fasten the amp to it.

However, if you are planning replacing the enclosure with a custom one, you might want to have it designed to secure the factory amp (which you'll need to keep if you don't plan on replacing the head unit or other speakers) directly to it as well as the new amp that will power the sub. I've been brainstorming ideas for this recently with the help of Mr Marv.

If I ever come to a decision about how to upgrade my sub, I'll post a report with pix. My main concern at this point is how to do the wiring of an aftermarket amp with the existing factory amp. I'm not sure whether to splice in to the in-coming wires before they hit the factory amp or the out-going wires that go to the factory sub. Right now, I'm thinking the former. Who knows what that factory amp has inside it, in terms of crossovers and signal filters and such. I also wonder if the factory JBL head unit has any amplification in it before it goes to the separate factory amp in back.

 

Well I guess I should've clarified .... I replaced the stock sub with a pioneer shallow 8" 500w it should rip ..... took me a loooong time to take the eniire back seat apart in the proper order but I got it done and the sub is frimly in place......next is to wire the amp, I will be using the space behind the driver side rear seat to mount the amp and we should be good to go. I had to stop after the amount of work it took to do a sano job on the sub tomorrow I will be installing the amp and stereo (which I consider the easy part after that sub install I have ssen the thread about wiring an amp so I am good to go there ...i'll update tomorrow. Sorry no pics I don't have a camera currently

 

I will be installing a Jensen head unit that plays MP3's and cad play them from a DVD disc so i'll have 4.5 gigs of music on one disc but if you have the JBL system make sure you get the correct wiring harness Scosche makes an excellent one also I do recommend tha if you are indeed replacing the stock sub with an aftermarket try to get a shallow sub it will make your life much easier. Just cut the original wires going to the sub and pull them out and send new wire that will go to your other amp through the grommet and you will be air tight..........I doubt the factory amp has much power as it is running the 4 door speaker and the 2 tweets plus the sub so I disconnected the sub and will use my Kenwood amp for that. You can slpice the wires but if you get an aftermarket head unit (personally I think the stock 6 disc unit sucks and skips too much) there will be plenty of places to wire the stock amd plus additional pre-outs for the sub amp ..... i'll let oyu know once it's done how it sounds

 

Well after all the blood sweat and tears I finally finished the install with the stock sub replacement and an external amp......basically I replaced the stock sub with a pioneer 8" shallow 500w unit and a 400w amp...... sounds like sh!t!!!!! I regret using the stock enclosure as the whole back end distorts and rattles way too much im going to a stereo shop tomorrow to remedy the problem possibly remove the stock enclosure and put in a mdo box ..... lots of work and lackluster results ....If anyone can answer this.....would putting a 1" port hole in the box help with the distortion? Im thinking the box is too weak for the sub and it is vibrating creating the resonance

 

Do you know for certain that the sub that you purchased is compatible with the volume of the factory enclosure? It's possible that the volume of the enclosure is way too small. I wouldn't mess with trying to port the factory box.

Also, 400 watts sounds like a lot to power a single 8". How high do you have the gain on the amp turned up (percentage-wise)? A quarter? Half way? 3/4 of the way?

Are you sure you are wired in phase?

Have you tried stuffing some sort of soft material (carpet or something) between the rattly parts such as the enclosure and the back wall of the truck to see if that helps at all?

Did you end up splicing the existing sub output leads from the factory amp into the new amp? Could be that the signal coming out of the factory amp is weird somehow and is somehow not "mixing" well with the new amp. Like I said in my previous post, who knows what kind of signal filters there are in that factory amp that could be causing distortion or crappy sound quality when further amplified by a dedicated sub amp. That's why I may try to wire mine to the leads that come from the head unit before they reach the factory amp. It may be a cleaner signal.

 

I have learned a few more things today that should clear some this up

THe sub I bought is specifically designed for a small enclosure the Shallow poineer 8" here are the specs.....based on the air space requirements and the size of the stock sub bow I am WELL within the air space requirements the stock bax is plenty big :
[FONT=Arial, Helvetica, sans-serif]Specifications: [/FONT]

• [FONT=Arial, Helvetica, sans-serif]Watts MAX. Music Power 500W
  [/FONT]
• [FONT=Arial, Helvetica, sans-serif]Watts Nominal Power Handling 120W
  [/FONT]
• [FONT=Arial, Helvetica, sans-serif]Frequency Response 30-1,500Hz
  [/FONT]
• [FONT=Arial, Helvetica, sans-serif]Sensitivity 85dB
  [/FONT]
• [FONT=Arial, Helvetica, sans-serif]Ohm Rating 4
  [/FONT]
• [FONT=Arial, Helvetica, sans-serif]Recommended Enclosure 0.15-0.5Cubic Feet[/FONT]

THe speaker as you can see can handle a LOT of power for an 8 make that an exceptional amountr of power which is the reason I chose it for this truck so I could go with just 1 speaker. As of right now the gain is at about 3/4 and it is hitting very well for the rock/metal I listen to.

The speaker is wired in Mono and the amp is set to mono as well so it is receiving the maximum anount of power from the amd which puts out 100 rmx at max gain and 400w peak at max gain so I am good there too ....man you should see this little sub jump out on a goot bass drum hit wow.

I replaced the stock unit with a jensen unit that can play dvd misic discs. The head unit itself also has a single (mono) subwoofer out that I used for the amp (I checked with a couple local shops and they said it was the best way to go. The Jensen unit also has a built in Low pass filter that can be adjusted and well as a subwoofer out level to adjust I have the LPF set at 80hz and the amp is the same.

I Usewd the turn ol lead from the head unit and made a "y" sp to speak so both amps are turned on by the head unit I used the scosche wiring harness made things wiring wise a piece of cake.

So this afternoon I pulled the plastic covers out from behind the seat and the sound quality jumped 1000%! but there was still a lot of vibration now brings me to my next problem .... Since the speaker box is bolted to the back wall of the truck it causes a lot of vibration where the bolts attach it to the truck how or what should I use to prevent this? I stuffed a clean shop rag real tight in between the box and where it was vibrating the worst and it really almost killed the whole problem but I am looking for something more sano and permanent .....anyone have a fix for this??

 

I don't have any bright ideas about a more permanent fix for the resonating parts...maybe a couple of those thick soft rubber tiles they sell at Home Depot secured to the back wall somehow?

So after all the time, work, and money -- and despite the vibration problem you are still trying to sort out -- would you say the upgrade was a worthwhile improvement over the factory setup??

 

Well I made a trip to the local lowe's to find a solution...here's what I found.

Rubber Grommits on both sides of the mounting surfaces for the back of the cab (there are 3 bolts put the grommits on the front & Back) and make sure to get at least 6 x 30 screws so they can grab the threads.

Peel N Seal is sole there 6" wide 25' long $14.95 it is the same stuff as dynomat ....well almost identical close enough and A LOT cheaper I haven't applied yet as I am still on the mend from a recent dirtbike accident but the grommit idea as shock absorbers works very well thus far with the peel n seal added it should be perfect but make sure to remove the plastic covers as the vibrate like crazy if you try to leave them on.