my experiences upgrading the jbl system

[smak]

I've noticed alot of contradictory inforomation on this forum about what harness to use for an aftermarket head unit, weather or not you can (or should) utilize the factory amps and so on.. thought i'd lay down what i've gone through the past week or so, and let people know what they may expect from their upgrades.

I threw a new sony head unit into my '94Mtx SHO with the best buy "70-5511" kit (not on display but they sell it out of their stock room if you ask a salesperson) had three sets of instructions for various installs.. i chose to keep the factory amps so have the "amp delete" cable left over. after 5 mins of soldering everything worked great. sub and all.

One thing i noticed was the volume control started a little higher. volume setting "1" was already fairly audible and 5-6 would drown out the sound of the engine and factory exhaust. its still nice and clear at 15-20 though (and LOUD heh), but my pass side speaker is on its way out, it starts breaking up at certain frequencies at any volume above 12. i suspect it was already damaged by the previous owner because the door panel was obviously removed and improperly replaced (door lock issues i think was his explaination) maybe he punctured the cone or damaged the surround? i'll be replacing them with some 4" etons soon anyways so it doesent really matter.

I upgraded the factory sub to a JL 10W0 4 ohm unit.. crammed it into the factory box (am selling my factory 6.5" sub on ebay currently actually, it was in great shape which totally surprised me for a 10 year woofer. no reserve if you want it) you DONT have to split the factory box in half heh.. simply pull back the foam over top of the speaker (not the surround of the speaker itself, but the piece that isolates the sub to the decklid) and remove the 4 torx head screws.

the JL 10 barely fit into the box depth wise after trimming the tabs ALL the way down within the box. even with alot of stuffing the box is still way too small for such a large driver. it responds fairly well down to maybe 50Hz but drops off in a very steep manner. i'll be fabbing a 25+ litre sealed box later on and bolting to the factory location but firing outwards. these changes should make the driver a little more efficient but i'll loose the factory look.

it does hit hard as is though and i think the factory sub amp can handle the load. we'll see how things go when the weather warms a little and i get more use out of it. if it fries i'll put in something aftermarket *shrug* i dont think it will though.

if i had it to do all over again, all i would change is maybe select the JL 8W0 driver instead for the sub.. it is probably be THE ideal woofer to throw into the factory box with a little modification. you should still stuff the box with fiberglass or your material of choice to add the illusion of a 16L-19L box. the factory amp would be ideal for this driver also. I'm missing out on some of the 10's performance by using the JBL amp, as its sweet spot is around 115-140 watts rms.

the stock system with a JL 8" sub and modern head unit would leave 99% of the population VERY pleased i think.. it is a very nice system in my opinion and well designed.

Has anyone had any success adding a cap to the system somewhere? find a spot to hide it to maintain a sleeper look? let me know of your experiences.

 

[Chris Benvie]

Nice write up!

The stock speakers are only meant to handle about 10-12 watts RMS. While your aftermarket deck is probably pushing 20-24 watts RMS, and peaking at somewhere between 40-50watts!

You can get some good deals on speakers on ebay and in some of the smaller car audio stores on close out.

Adding a Farad Cap would be great if you are using aftermarket amps, but probably not neccesary if you are just using stock amps.

Are you using the factory sub amp? If you are you are probably overloading that amplifier and it will eventually shut off as it gets too hot. I would suggest upgrading to a 150watt amp and possibly a .5 Farad capacitor. You can mount the cap on the bottom side of the rear deck next to where the sub box is, it won't be noticable at all.

Good luck!

 

[93medusa]

When you used that harness to keep the factory amps, did you by any chance use the decks Pre-amp outputs instead of the speaker outputs? The speaker outputs are sending an amplified signal to the amps, this is not ideal. The best way to do it is to solder on some RCA connectors to the harness, and then use the preamp outputs from the head unit to run the factory amps. This is how I had mine running, and it sounded great. It cranked way up, but was also able to play quiet, something that you can't do if you use the speaker outputs. Also, sending the high level signal into the low level input of the amp could posibly damage your amplifier's input stage.

That 10 inch woofer is probably not very happy in the meager enclosure that the JBL system uses. Although you were able to physically get it to fit, It's most likely stifled by the lack of volume, even given the amount of stuffing you put in the cabinet. An 6.5 or 8 inch speaker is far better suited to duty in that enclosure, and despite their smaller sizes would most likely play louder.

Adding a capcitor to the stock system would most likely not enhance it's performance very much. The JBL system does not draw enough current to require the reserves that a capacitor supplies.

Also, you can't overload an amplifier unless you are dropping the impeadance down way low. With the 4 ohm load that the JL10 is giving the amplifier, you aren't running any risk of damaging your amplifiers. However, I agree with Chris in that you would get better results with an aftermarket amplifier, and i would recomend getting the correct size box for that sub. With a 150 watt amplifier, you shouldn't even need a capacitor, so long as you have a decent battery.

Dave

 

[smak]

thanks for the props chris.. and the suggestion about upgrading the drivers.

if i wasn't set on moving onto a higher end unit then i'm sure the jbl's would hold up well though. i have a sweet midrange picked out that will respond nice and flat upto like 2kHz.. i'm hoping the factory amp crosses over to the tweeters after or around there.

'93.. the line level preamps were all i had avaliable. my deck has rca's but only for "rear audio" which is intended for subs only.. if someone wants to upgrade down the road and does not want to use or fab a line level to rca cable, then sticking to a lower rms rated preamp deck would minimize the volume issue. 15x4 should be fine, not sure about its effect on the factory amp though.

my decks specs lists max wattage only and sony rates it at 50x4 at 4 ohm. not being able to get the volume down to a whisper doesent bother me too much, its not really a level i enjoy music at anyways

as for the sub.. i'd be surprised if i'm getting 10L out of that factory box. the basket and magnet just take up so much volume that even with stuffing its pretty tiny. the graph plots the response curve at 10L and the ideal 30L+. (according to WINISD and JL's provided specs) theres a noticable steep dropoff around 60Hz with the smaller box, whereas the larger box stays fairly flat (just 3 db drop) down to 30Hz.

i'm still curious about the cap though.. might add a .5 down the road. we'll see i guess.

 

[Chris Benvie]

Yea the cap at this point won't do much for you besides be an added safeguard incase something out of the ordinary happens.

You should be good! Nice to see another knowledgable car audio guy.