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Discussion Starter #1
I have the JBL Synthesis system in my 2008 Sequoia and am looking to upgrade the subwoofer. Instead of just replacing the subwoofer, I plan to add an amp as well. I plan to use the amps speaker-level inputs since they can detect the signal to turn the amp on instead of running a remote wire. I thought the easiest thing to do would be to use the 4 speaker wires from the disconnected sub as the speaker level inputs for the amp. Is this going to be OK? More specifically:
1. Will this be a signal with a wide enough range (Hz) to produce a good signal to the amp and thus to the new sub?
2. Since the JBL DSP/Amp will then be seeing an amp instead of a subwoofer and the impedance will be different, will this mess up the stock DSP/Amp or the signal to any of the other speakers (if they are run in parallel or series)?

Also, am I OK to install a Class D Mono amp in the floor cargo well in the back of the Sequoia (the little handle in the floor)? It would be nicely out of the way but I worry about it having enough ventilation so the amp doesn't overheat.

Thanks.
 

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Check out the JL Audio Stealthbox for 2008-present Sequoias. 13.5" 600 RMS.
 

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Discussion Starter #4
I have looked into the Stealth Box - I am wanting to maintain the factory look. Not stealthy enough for me.

I am looking at a Kicker IX500.1 Amp. I have ordered an Infinity 8" sub that should fit in the factory mount.

I am trying to do this on a budget, too, and I'm in no hurry, so eBay is my friend.

Any other thoughts about the speaker level input or impedance questions? Thanks.
 

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Yea I'm looking to put a better woofer in the factory enclosure also. I've read on here that it will actually put out some good bass with the right speaker in there. I'd definitely love some pics when you get it done. I've even wondered what a better speaker hooked up to the factory amp would sound like.
 

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I have a kicker 400 Watt mono pushing a series set of 2 kicker 8" shallow mounts in a sealed box under the back seat of my 05 Tundra DC XSP.
It runs off of the factory JBL Line level outputs for the rear speakers with no problems.

You should not run into any impedance problems using the speaker level for the sub inputs, that is exactly what it is designed for. The inputs are many orders of magnitude higher in impedance (negligible biasing current will flow into them). Your signal will already be a low-pass filtered signal so I am not sure what you worried about bandwidth there. Two low passes in series will just give you a sharper roll-off, cut off, corner, half-power or whatever other term you are used to using. If you are worried about it just run your new amp as full range, set the gain and leave it there. You will be able to control it with the factory head unit well enough.
 

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Discussion Starter #7
Thanks pxsp. That is helpful about the bandwidth - makes sense that it won't be an issue - makes the internal crossover redundant I suppose. My question was about the difference the factory amp will see in impedance and its only a question in my mind because I was surprised that there are 4 wires running to the subwoofer - I was expecting to see two. That made me think that its possible that the speaker wires are maybe running parallel or in series to the speakers in the rear doors, but I haven't been in there to check.

Does anyone have a wiring diagram for a 2008 Sequoia with JBL? I have found plenty for earlier model Sequoias but not for 2008+.

I did end up getting the Kicker IX500.1 (275W RMS) and I have an Infinity Reference 860W 8" Subwoofer (250W RMS) to put in.
 

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Some subs will have two coils so it is easier to impedance match. As an example if you have two 4 ohm coils you could wire them in series or parallel to get 8 ohms or 2 ohms. You could of course just wire one for 4 ohm. Or, as may be the case for your Sequoias, you can wire them as two separate 4 ohm coils as long as they are in phase with each other.

Generally you don't have to worry about connecting a higher impedance load than was previously connected because your power output is going to go down. Your factory amp should run much cooler not having to drive the sub because it won't be delivering any noticeable power to your sub amp.
 

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Discussion Starter #9
I guess I would be surprised that the factory sub (with its paper cone and small magnet) is a dual voice-coil sub. That's why I was surprised it had 4 wires attaches to it. The new replacement sub is a Single voice coil.
 

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I can almost guarantee you that the watts coming out of the factory sub wires will be too much for the high level inputs on your amp. Even some high wattage hi-to-low converters won't last when hooked up to the factory sub wires. Either run wires from the full range door speaker wires from the amp under the passenger seat or get something high quality for audio signal conversion such as an Audio Control LC2i.
OEM Integration
 

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Has anyone actually upgraded the sub in the JBL system? I've read probably 5 threads of people asking about swapping it out and what sub will fit but nobody has ever come back to update?

I recently installed a 500/1V2 amp and 12W3 sub in a ported box and I'm getting WAY to much boominess in the cabin so I'm thinking of just upgrading the stock sub.
 
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