After debating which amp to go with, I decided on the Alpine "Power Pack" for use on my factory Harley Davidson radio (my bike is a 2011 Ultra). The unit puts out 45 watts RMS x 4 channels @ 4 ohm or it can be bridged (which is what I did) for an output of 90 watts RMS x 2 channels @ 4 ohm.

This is a "Universal" install (not plug and play) but is pretty straight-forward on the installation if you pay attention. For example: When you bridge the amp (a switch on the back of the unit), you don't simply use the front speaker outputs. You use a combination of the front & read outputs. You also have to select "speaker level input" (switch also located on the back of the unit) because the default is RCA input and the HD radio doesn't have RCA outputs.

The instructions indicate that the unit will "Power On" when it receives a signal through the speaker input. If you read the "fine print", it also says that the signal from some head units will not "Power On" the unit, which is the case for the Harley radio/head unit. I used the remote power wire for the amp to turn the unit "On" when the ignition switch is on the accessory or run position. This was easy for me, because there was already an accessory connector & ground inside my fairing that are for HDI use. HDI is Harley Davidson International and is a connection for an additional low watt "parking light" (located in the headlight) for countries like Germany.

I tried to use the HDI power for the amp (got lazy), which resulted in the amp sometimes powering-up and other times it was dead. I could have found a "constant hot" wire in the fairing but decided to run a power lead back to the battery, along with a 15 amp in-line fuse. After I did that, everything works perfectly.

There are (2) gain adjustment screws on the end of the amp. If you're using the amp in 2 channel mode, the adjustment screw for the rear speakers in inoperative. I found that the gain for the front channel works best set at "minimum" when used with the 6.5" Titan XL II speakers. I could actually dial-it-up a few notches on some of my higher quality CDs without distortion but some CDs ("Legends of Rock" bought from Time Life) don't have the greatest fidelity and can cause distortion. I played "Hotel California" by the Eagles off of the original CD and was able to crank the gain up about 25%. The same song off of my "Legends" CD would produce distortion at just over the minimum setting. By the way, "Hotel California" is a highly recommended CD for testing audio equipment, that's why I chose it. Do not use your radio to set your gain. The fidelity isn't there.

Anyway, the system is in, it exceeds my expectations and I'm a happy camper. Here are some photos of the install. I'll include the rest in a separate post. You'll note that since I have the factory CB module, there isn't a "level" platform to mount the amp. I bought a Hawg Wired "Dummy Module" ($25.00) to solve the problem.

 

More photos of my Alpine amp installation.

 

Thanks for the write up.
you still able to run the factory fader when it is set up for 4 speakers?
This will be on my next list of upgrades

 

kinda curious about the bridged mode setting. what are your rear speakers running on, just radio power?

 

Yes, if you set-up the amp for 4 speakers and wire accordingly, the fader will work.

 

Yes, I'm running the rear speakers on the factory radio. Of course, with 90 watts of power going to the front speakers, the factory rear speakers aren't really audible when you crank things up (Dire Straits - Money for Nothin').

If I use the fader on the factory radio, I can achieve a good balance, up until the factory rear speakers begin to distort, then I either have to turn down the volume or adjust the fader more to the front channel.

My wife hardly ever rides with me any more, so not having upgraded rear speakers (and an amp for them) isn't that big of a deal for me.

 

Would you say there is enough room on top the radio for 2 of those alpine amps or no?

 

That's what I was thinking.
Won't need to max the system out whan I'm flying down the Hwy

 

I'm not for sure.

I know that many folks here on the forum have installed the Rockford Fosgate PBR300 amps in their batwing fairings, which has a height of 1.53" and width of 4.25" (length is not an issue). The Alpine amp is 1.5" high and 2 9/16" deep so the total depth of two of them would be 5 1/8", which is still "inside" the back of the factory radio.

 

Guys...if you buy the amp mount from Hogtunes Part # 4405-0234 (the one that replaces the right side speaker bracket) the KTP-445U Alpine amp bolts on there great