Good subwoofer ground location?

salong53

salong53

New member
I've installed a JBL sub/amp combo in my '04 SR5 and when I turn the amp gain up beyond about 1/4 I get an unbearably loud hum. The weird thing is, this only happens sometimes. Other times I can crank the gain way up and let the sub boom with no distortion or interference, and then spontaneously it will go into PITA hum mode and I have to crank the gain way back. The sub still works at that point, just at a much quieter volume. It's not the RCA wires (I've checked). I speculate that I've got a bad ground loop but I don't know where to find a consistent ground. Currently the ground is attached to the body under the center passenger seatbelt bolt. I've looked at other threads and still can't find my answer. Please help!
 
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In my '01 I pulled the center console out and used one of the e-brake bolts. Not sure if that's an option on the '04. FWIW, I connected that ground wire (4-gauge) to a distribution block so I could easily run additional ground wires in the future.
 
I used the seat mounting location and put it under the carpet. Works well. I would not think it is much different than seatbelt, but an easy spot to try
 
salong53 said:
"I've installed a JBL sub/amp combo in my '04 SR5 and when I turn the amp gain up beyond about 1/4 I get an unbearably loud hum. The weird thing is, this only happens sometimes..."
Click to expand...

Hi salong'

There are a couple (or combination) of things that could be causing your problem. First:, how are you feeding the subwoofer's amp. Are you using a "line-out" directly from the hu (RCA's), or "high-level"; taking the signal from the left and right speaker outputs? If you are using the "high level" signal, you may need to include the use of a LOC (line output converter) which helps to match the higher voltage speaker output signal (800mV to 8vdc), with the 'more sensitive', low voltage input requirement (200mV to 2vdc) of the amplifier. My two jl audio HD-750/1 mono-blocks have an "Input sensitivity selector switch" which does exactly what an loc does; your amp may employ one as well. But a mis-match here could cause a very serious "electro-magnetic field" (emf) hum. Amazon.com: Boss Audio Systems Car High Level to Low Level Converter (B65N): Car Electronics

Second: Has a proper input sensitivity adjustment been performed after the equipment was installed? This is an extremely important step. To neglect doing this can create excessive distortion, poor/inadequate volume levels, and introduce much electrical noise into the program signal. Here's a link to make things easy if you haven't done this yet: JL Audio » header » Support » Tutorials » Tutorial: Input Sensitivity (Gain) Setting Take your time w/ this tutorial and be comfortable with it... it's your best friend!

I really liked "Bucket81's" suggestion and link, that'll take care of any poor grounding issues if there are any. One more thing I'd like to mention. Something known as a "ground loop" effect. Since your car uses it's body/frame as an electrical path back to the battery, sometimes "electrical noise" is allowed to travel into your audio system, and amplified through the HU and other audio components. This electrical noise may also include "RF (radio frequency) signals"

This electrical noise can be "filtered" out and routed to a proper ground using a device called a "ground loop isolator". They are very inexpensive and easily installed; here's a link to a good one (check it's reviews): Amazon.com: Boss Audio Systems Car Ground Loop Isolator (B25N): Car Electronics Hope this helps. Be sure to let us know how things worked out with this and best to you!

rigtec, cheers
 
rigtec said:
Hi salong'

There are a couple (or combination) of things that could be causing your problem. First:, how are you feeding the subwoofer's amp. Are you using a "line-out" directly from the hu (RCA's), or "high-level"; taking the signal from the left and right speaker outputs? If you are using the "high level" signal, you may need to include the use of a LOC (line output converter) which helps to match the higher voltage speaker output signal (800mV to 8vdc), with the 'more sensitive', low voltage input requirement (200mV to 2vdc) of the amplifier. My two jl audio HD-750/1 mono-blocks have an "Input sensitivity selector switch" which does exactly what an loc does; your amp may employ one as well. But a mis-match here could cause a very serious "electro-magnetic field" (emf) hum. Amazon.com: Boss Audio Systems Car High Level to Low Level Converter (B65N): Car Electronics

Second: Has a proper input sensitivity adjustment been performed after the equipment was installed? This is an extremely important step. To neglect doing this can create excessive distortion, poor/inadequate volume levels, and introduce much electrical noise into the program signal. Here's a link to make things easy if you haven't done this yet: JL Audio » header » Support » Tutorials » Tutorial: Input Sensitivity (Gain) Setting Take your time w/ this tutorial and be comfortable with it... it's your best friend!

I really liked "Bucket81's" suggestion and link, that'll take care of any poor grounding issues if there are any. One more thing I'd like to mention. Something known as a "ground loop" effect. Since your car uses it's body/frame as an electrical path back to the battery, sometimes "electrical noise" is allowed to travel into your audio system, and amplified through the HU and other audio components. This electrical noise may also include "RF (radio frequency) signals"

This electrical noise can be "filtered" out and routed to a proper ground using a device called a "ground loop isolator". They are very inexpensive and easily installed; here's a link to a good one (check it's reviews): Amazon.com: Boss Audio Systems Car Ground Loop Isolator (B25N): Car Electronics Hope this helps. Be sure to let us know how things worked out with this and best to you!

rigtec, cheers
Click to expand...

Thanks for the reply. I ended up determining that my amp gain controller was shorting out somehow. (Crutchfield customer support was awesome in assisting with this). My system was/is grounded to one of the 2nd row seat belt brackets after I used sandpaper to grind paint off the body. RCA cables were the audio source to the amp, and they were run on the opposite side of the vehicle as the power wire and remote turn-on wire. My original thought was a ground loop problem, but I tried several different grounding points, and and still the same problem. Eventually, I plugged an iPod directly to the amp using a 3.5mm-to-RCA cable and it still produced the hum. At this point, I knew it wasn't a ground loop problem. Crutchfield sent me a brand new sub/amp for free and now it works flawlessly!
 
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Hi salong,

By "Gain controller", I'll assume you're referring to the 'local' sensitivity control that's built in to the amp's front control panel; not the "remote level control" (RLC) that's purchased separately, and connected through the 'RJ-11' phone cord adapter/port. That's fantastic salong, that you found the problem! And Crutchfield is giving you a brand new amp... I perceive that you're one of those folks who is blessed among us, seriously! Good for you brother. Thanks for reporting back to let us know, peace to you.

Greg, (rigtec)
 
For a good ground on 3rd gen (maybe others) I'd suggest using rear seat belt bolts into the metal body. Be sure to sand the paint off so the connection is good.

I'd also suggest running all new copper 12G power, ground, and 14G speaker wire for any aftermarket head unit.

Doing all this will greatly reduce chance of RPM speaker wine.
 
Best ground location is going through the hole on the front driver's side of the floor in the cargo area, it comes out above the coil bucket area, there is a threaded hole just to the front of the coil bucket, get a bolt that fits there and you're good to go.

Edit: Oops, didn't realize this was for 4th gens, I'm talking 3rd gen in my post above.
 
BrianSD_42 said:
"...I'd also suggest running all new copper 12G power, ground, and 14G speaker wire for any aftermarket head unit..."
Click to expand...

Hi Brian,

Here's where we've gotta be careful... A 500w rms, class D subwoofer amplifier will draw 40-45 amps 'and up' (depending on the amplifiers efficiency), and will require an 8ga copper power line to feed it; more than 10ft will require an even larger cable. A 750 watt subwoofer amp (80% efficient like jl) will draw 56 amps @full load, and require a 4ga copper line (up to 10ft) with a 60A in-line fuse at the battery. Here's a reference chart for "on the fly" calculations: https://www.google.com/url?sa=t&rct...Jzn22lfcEOEW7NBkw&sig2=AlfYXiIRckGZpV51tHCg5Q

I totally agree with your min. speaker size recommendations however, Regards.
 
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Dude I said head unit not amp. :)

But other than that I totally agree. 4G all the way for amp power. I don't even consider 8G an option since so many companies (selling wiring kits) lie about the G and are not AWG rated.
 
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