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Discussion Starter #1
I just bought me a Alpine 9815 for my is300 my ? is i should bypass the factory amp right! If so then will i have to run new wires to & from the speakers or can i splice into them from the harness
 

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1) Factory Amp will not work without factory HU, so Yes, you need to bypass it.
2) You can splice into the harness, however the OEM wires are not of a high quality.

3) Rear speakers actually have 2 speaker pieces each. That means you need to buy a crossover to work with it. Lisnup65 can specify which specs to use. Otherwise, you will need to replace the rear speakers. The front tweeter piece is parallel to the woofer/mid piece, so no worries there.

P.S.
Download correct wiring diagram for your model year and use it as a guide.
 

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From what I understand from the manual, the built-in crossover works only with an external amp for the subwoofers. All I see is 6ch RCA output and 4ch speaker output. That means that you need an external crossover to work with rear speakers.
 

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Here is a useful post:

lisnup65 said:
The problem with adding a new amp to the factory system is as follows:
The factory speakers suck and will not handle much more than thier rated 15/30 watts of power.
-The front speakers are a simple 2 way design that the factory amp limits the high-pass frequency to the set and then their is a 6db cap that limits what the tweeter gets. You can simply add an amp that has a highpass X-over set around 90/100 Hz and you will be fine.
-The rear speakers though are a bit tricky as you have a 6*9 with a stacked mid/tweeter. It is a Bi-amplified system which means the factory amp feeds each speaker with its own channel of power. The factory amp is not a true 6 channel amp. They use X-overs built in and send each speaker its designated frequency. The woofer is a 2ohm speaker thus allowing the amplifier to create more current for more power than the 4 ohm mid. You cannot simply hook a 4 channel amp up and be good to go unless you left either the rear 6*9 or the rear mid disconnected. The reason behind this is because the new amp may have a cross-over built in, it cannot through a single channel split the single into 2. A 6 channel amp would make install easier, but for the cost its not worth it as you would be better off replacing the factory speakers.
-To sum up the rear speaker problem is as follows.
--You need a custom built cross-over network if you wish to use 2 channels to drive the 4 speakers in the rear.
--6*9 should have a cross-over designed for 2 ohms. The design should be bandpass at 50-500/1000Hz.
--Mid-range x-over should be a high pass design at (I recommend) 1000Hz

-If you just hook up 2 channels to all 4 speakers this is what will happen.
--The amp will see a 1.33 ohm load and most likely the amp you have is not capable of running this load.
--The power the amp would produce at 1.33 ohms will smoke the cheap factory speakers.
--The full range signal will smoke the factory speakers as they have limits and are not designed for full range.



Now if we factor the cost of the cross-overs it is cheaper and a better sound quality choice to simply replace to even a set of coaxial's.


Does this now make more sense?
 

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Discussion Starter #6
Thanks Vlad_a so where are yall connecting the illumination wire to in the plug are you just going direct to the lights? I noticed theres a white/green wire in the plug thats not in the lexus wiring diagram for the 2001. The front speakers are they connected to the factory amp?
 

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Here is what I PMd to one of the members before:

Grey is the "remote" wire that tells the system the car is on. L/Y (Blue-Yellow Stripe) is the constant 12V that powers up the system.

For illumination, you can grab +12V from the light coming from the Glove box or Cigarette Lighter socket. It is the GREEN wire. Same wire is used for Radio.

White-Green Stripe wire is the DIM wire that dims the light relative to the ground point. So, if you wanted to use dimmed lights, you would connect positive terminal to Green wire and negative to White-Green Stripe wire. If you wanted to just get the illumination, not dimmed, you would connect positive terminal to Green wire and negative to the ground (Brown).

It is not recommended to use the gray wire since it handles only low current. Connecting to the cigarette lighter adapter is recommended.

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Negative dimming, White-Green Stripe wire.
Illumination turns on via Positive Green wire.

From my previous aftermarket install experience, the headunit will simply dim the lights when the illumination is on.
 
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