I have this Kenwood mono amp that I want to add between the factory radio and factory sub. It has speaker level inputs for R and L and one sub output for the sub speaker.

If I cut off the factory wire (+ and -) that goes to the sub and reroute the wire to the speaker level inputs of the Kenwood amp, my question is...would I hurt anything if I wire the + and - to "Y' onto both the Left and Right speaker level inputs? Would the impedance that the stereo sees change dramatically? What if I simply put it in, say the left channel?.... Would I still be driving the amp to its full capability?



Sub wire coming from the OEM Stereo (+/-)
______(-) Right Amp Input
/______(-) Left Amp Input
=================/ AMP >============> +/- Output to sub
\_______(+) Right Amp Input
\_______(+) Left Amp Input



This is for the GS sub and if possible I don't want to use a line converter and Y the RCA cords.
Thanks for any suggestion.

 

OK, it's a bit unclear, but I think I see what you're trying to do.
IF you're chopping off the SUB's wires, you can run them into the input of your Kenwood amp. It is designed to handle the high-level input (assuming you've properly verified this). If you run the wires into both inputs in parallel, still no problem. The factory amp's output that you'd be using is designed to drive a low impedance (the speaker). If you drive the Kenwood amp instead, it is much easier on the factory amp - it will see a much higher impedance, prob on the order of 10K ohms (instead of 4). If you parallel the L/R inputs, the equivalent impedance would drop by a factor of 2, but this is still much higher than the speaker's impedance was. The factory amp will have to produce slightly more current to drive both L/R inputs instead of just one, but this is nowhere near the current required to drive the low impedance of the factory sub. (You'll have to adjust the gain on the amp accordingly anyway - see below.) The Kenwood amp'will be lowpass filtering and summing the two inputs to produce the single sub mono output. In any case, you may incur noise problems - you'll have to try it and see.

The alternate way to do this would be to use the low-level input setting on your amp, and use a line-level converter (Audiolink Powerlink-II is recommended), and Y the output, as you say. This tends to minimize noise problems because you're chopping the signal level down just prior to entering the amp. People that don't have speaker-level inputs on their amp do it this way. There's nothing really wrong with it. - you could wind up with noise problems either way, depending on the architecture of your system, how your amp is built internally, etc. You can also tap into the preamp line that enters your factory amp and completely bypass it, only if you have the GS Nakamichi system. Not trivial if you have stock Pioneer, and not for the uninitiated anyway.

If you have access to an oscilloscope, the way you should determine whether you're "driving the amp to its full capability" is to take a sinewave test tone at 0dB FS (full scale) at a low frequency like 40-60 Hz, from a suitable test disc, and put it in your CD player. This represents the largest signal that your CD player can produce without clipping/distortion. With woofer disconnected, set your volume control to the 12 o'clock position, or above if you can determine the point where your headunit output starts clipping. You can then set your amp input (or output) gain accordingly, and look for clipping of the sinewave. You can do it all by ear (approximate, and not as effective) if you don't mind listening to really loud sinewaves, or you can use a music source. Turn your headunit volume up to where you normally think it's loud, then adjust your Kenwood amp gain. This won't show you if the amp is clipping however, so beware.

 

Thank you for your excellent detailed info. This is exactly what I'm trying to understand and it is very clear now. All I want is a little more bass that would come from the added amp and increase the reserve power to the main speakers by decreasing the power needed by the factory amp to drive the sub (I'm assuming power to the sub also comes from the main factory amp).

Thanks again.