Those are all very good points. I was trying to point out that some stock systems limit the bass going to the speakers, it frees up power for the mids and the highs. Sometimes adding an amp and speakers that have better low freq response can improve the "presence" of a sound system by adding a little more volume in the lower freq range.
I do agree with JZ, adding a sub in the trunk will make a big difference. Some of us need the trunk space and will go to a lot of effort to avoid a trunk sub.

JZ have you tested the Alpine KTP-445U? I was puzzled by the instruction to use the "radio power" as long as it's at least 15A. If I assume that 10 A are available for the amp, that leaves about 145 watts of input power for the Alpine. My math says that's only about 35 W input power, not nearly enough to get 45W out on each channel.

 

Some systems do that, but not for that reason. they do that to prevent overstressing the speakers. low frequencies don't "take power" from the mids and highs, amplifiers don't work like that.

4x45 is 180 watts, which is 12.5 amps at 14.4 VDC supply. The 445U is a class-D amplifier so its efficiency is probably in the 90% range. So yeah, it should be fine on a 15A circuit.

I don't know what you're saying here. what do you mean by "10 A are available for the amp, that leaves about 145 watts of input power for the Alpine. "

 

If the head unit is 16wx4 and 100% efficient, it would require up to 64W or about 5A, leaving only 10A for the Alpine. I usually trust published power numbers, these don't seem to add up to me.

 

because if you're using the speaker-level inputs (like the OP is) on the KTP-445U, the head unit is no longer putting out 16 watts x 4. the stated 16Wx4 is with a load impedance of 4 ohms. The input impedance of the Alpine thing is minimum 10k ohms, so the radio is only delivering about a hundredth of a watt per channel. in this case the radio is likely only drawing about an amp or two maximum.

 

Thanks for all the suggestions. Sounds like an Infinity Basslink subwoofer may be my best choice considering I want to keep as much trunk space as possible. Looks like the power/ground wiring is not a problem.

However not sure about the signal connections or amp turn on (if needed). I read a lot about the install on Shaker radios but I have a non Shaker so don't have amps for any door subs from the factory. Any idea what the best way would be to get signal and/or amp turn on connections for non Shaker factory radio. thanks!

 

the Basslink apparently has auto turn-on if you use the speaker-level inputs.

 

I use a Sony XM-4S which uses speaker level inputs, it turns off and on when it sees the radio turn on.
It does not require a 6 or 12V off/on control signal. I don't recommend this amp for your sub, but if you can find an amp you like with this feature it will save you some time and wiring.

I think we were both typing at the same time.

 

Where exactly should I be grabbing the speaker level inputs from? Can I get them from the rear speakers, do I need to run wire to the head unit and grab the front speakers, can I grab any speaker(s) ?? thanks.

 

On my 2012 the rear speakers have the full frequency range. I ran wires from them to my amp and tuned the amp for the best sound. I think it should work OK for you. I usually wire everything up before I mount them...makes it easier to make changes.

 

they're high-passed at 60 Hz, but that will still give enough signal for a subwoofer amp w/speaker level inputs.