Just thought id post a little blurb. I just finished installing a rockford fosgate pbr300x4 amp on my 2008 street glide. I decided to take on the task myself as most shops around me wanted 300 to install my amp and speakers so i figured id save and do it myself. I went with the polk audio mm651 speakers, most people on here say not to use them because they are 2.7 ohm, well i talked to a few people myself and they are better quality and handle more power than most speakers in its class. The amp install went smooth , i bought a 20 dollar amp install kit from walmart and it had all i needed. I also bought the speaker adapters on ebay for 20 bucks shipped. overall it took me about 3 hours total only because i took my time in routing the wires and took extra care removing my gas tank. I also used polyfill in my fairing and this thing rocks.........I had an arc audio amp 125.2 and polk db651s speakers in my last bike and this amp kicks its ***, i bought my amp on amazon for 150 shipped......i bought my speakers at fry's for 75.00 so for what I have invested i am highly impressed....thanks to those on here who posted wire diagrams and install info.........happy thanksgiving.......

 

I don't think there was ever a discussion over the quality of the Polks, only that the RF amp was not made for that low a load. RF told a couple of people who questioned them on it and they said that the amp was not made for a load lower then 4 ohms. Good thing those amps are cheap...

 

As long as the warranty isn't compromised by running those speakers !! Does the warranty go into detail about that ??

 

I agree about the RF amp kicking, my wife has me hiding my head in shame because I put one on her bike, and she can drown my Hawgwired out, and I paid less for her whole system than what just my amp cost, lol..

 

I was told by Rockford Fosgate not to run MM691's because of them being 2.7 Ohm speakers.

They said the amp is not designed for less than 4 Ohm loads and it would eventually damage the amp.

He also noted that any PBR300X4 running less than 4Ohm speakers would not be warranted if it failed.

Run less than 4Ohm's at your own risk, according to Rockford Fosgate.

 

Hmmm,, I know very little about audio systems but I gotta ask,, If a feller was to solder 2 Ohm resisters in line with each speaker, would that resolve this concern?? Would this effect the sound quality enough to notice?? Just asking because I am looking to upgrade my system & dont have 5 or 6 hundred to drop for amp & speakers.

 

Bigred just sells the speakers u got or $75 and by a set of rockford's that are 4ohms. About the same price on amazon.com. I have the same amp and set of Rockford T1692-S for $89 shipped of amazon. Best bang for your buck. Good luck with it.

 

What would be a good match for the fairing and tour pack speakers with the RF amp? Certainly interested in upgrading my sound.

 

Not being a tech or audio professional, I found this link (and website) to be very useful in providing useful information regarding speaker impedance and other audio questions:

http://www.bcae1.com/resvsimp.htm

Basically, speaker impedance is not a fixed value; it varies.

An amp driving a speaker w/ lower nominal impedance to the amp will require the amp to work harder which causes heat in the amp.

Driving the lower impedance speaker under normal conditions in a car wouldn't be a concern to me--I doubt I'd have to push the amp hard to hear the music clearly. But on a motorcycle the amp has to work very hard to drive speakers given the ambient noise, lousy acoustical environment, etc.

Like others, I've asked RF about using the PBR300X4 with the Polk 2.7 impedance speakers and was discouraged from doing so by RF out of concern for generating excess heat in the amp.

I wish the OP well with his system. And I hope he will post some experience long term with this set-up. Listening to the bike while it's on the kickstand has virtually no relevance to what happens running down the road at speed, especially on interstates--the amp is not working nearly as hard at zero MPH, as it is at 75-80 mph on the interstates.

Carl

 

Well, if the amp shuts down(or overheats), he will know where the problem lies. Turn it up (aka HTNHARD!!