i just read the thread about possibly losing the factory sub when you install a new head unit because you might have to bypass the factory amp(?)...
https://www.clublexus.com/forums/sho...threadid=99704

please tell me if the following scenerio is; possible? bad? good? idiotic?

first, this is all taking place in a 1993 LS400...
orignally, i was planning on installing an Alpine CDA-7995 head unit, and powering a 12" JL Audio by bridging a 150W 2-channel Lightning Audio amp. how much (for better or worse) will my 12" or factory 8"sub be affected if i run both subs off the same 2-channel amp (each with their own channel of course)? i imagine if i max out the factory 8", the 12" will be MUCH lower than it could be, but by how much do you think? would it be enough that i negate the purpose of the 12"?

or, should i just screw the factory sub and run the 12" bridged?

i read through that post and couldn't figure out where it was said HOW to continue using the factory sub on a new head unit (although people claim to have). if i have to blueprint and trace the factory wiring to figure it out i'd rather (for now) find a quick fix in either scenerio i've listed above.

THANKS,
d

 

Having the 8" as a midbass driver is not a bad idea, and you shouldn't use the same 12" sub amp to power it. As long as you can identify the turn-on lead of the OEM amp, then use same blue/white wire from the 7995 to turn it on, like you would turn on the LA amp.

 

I do not recommend keeeping the factory sub connected in ANY configuration as you describe, unless you give it its own amp output and/or its own crossover. Here's the deal: Whenever you have two or more speakers connected to the same amp output, the speakers will affect each other, dynamically (varying over time), as each voice coil pulls current. Fortunately, when we hook up multiple speakers of the exact same type, all speakers are basically doing the same thing at the same time, or close to it, within the same frequency range, so it doesn't really affect the native response very much, as long as the amp can produce the extra current in sufficient time. When you hook up two different speakers to the same amp output, each one will draw current differently, present a different dynamic impedance, and dynamically affect the voltage across the other one, depending on its own time response, which will tend to result in more distortion. This is especially true when you're using a stock speaker that probably wasn't too good to begin with, and which is why you are replacing it. Don't kill the natural response of the 12" that you're adding. If you want an 8" midbass driver, set your system up for that.

 

engin_ear,
thanks. makes sense. i'll bypass it. i really won't need it with a 12".