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Discussion Starter #1 (Edited)
I bought a Rockford Fosgate PBR Punch 300X2 amp and Polk Audio MM521 5.25" speakers. The speakers are rated at 90w RMS but at 2 ohm so with an amp rated at 150w at 2 ohm (the certs that came with my amp shows it really puts out 190w @ 2 ohm) and me setting the gain at I think it was 5 I smoked them in around a week. I bought a second set of the exact same speakers and set the gain at 3 so now it took a little linger to kill them. I'm now down 2 sets of speakers. Being the smart guy I am I now go for
and they sound great but are only rated at 60w RMS and my amp puts out 100w RMS (again the certs show mine puts out 124w @ 4 ohm) That's much closer but now I'm paranoid about killing a third set of speakers so yea here I go again (should have bought them the first time) and bought a set of Kickers CS65 rated at 100w RMS with 300w peaks so they'll handle what the Fosgate can throw at them. My biggest part of the Kickers was I didn't put an amp on the bike just to keep it turned down I wanted volume and these speakers honestly don't have as sweet a sound as the Polk's they sound good and really wake up when you drive them.

My head unit is clean up to 20 on the volume so that's where I set the gain and it sounded great up to around 5 so I backed it down to 4.5. This sucker will about take your head off at 20 but that's not the reason behind it it's so it 75mph I can turn it up to 15 and get wind defeating sound that crisp and clean.

I added Boom Mat speaker baffles for protection against water and dirt and got a bonus with the way the mid-range now sounds it made it sound a lot better. I guess instead of the mids going into the fairing they're directed at me.


Lessons learned here buy speakers able to handle the RMS of the amp. I like to share what I learn from successes and failures so others might not repeat what I've done.

Oh yea my wife's car is going to get a nice set of Polk Audio DB651's!!
 

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That's a shame and a real waste of money...but a good lesson to pass along.

The gain stage on an amp very often misunderstood. It's not a volume knob to make an amp put out less power. Turning input gain down will not protect speakers that are rated for much lower power. When you turn your head unit up, regardless of your gain settings, your amp will still have the potential to produce the rated wattage and blow speakers that aren't rated for that power.

Gain is a setting for the front end input of your amp. It simply gives the user control...to make sure you're not distorting signal on the input side.

Your speakers should always match the output rating of your amp for more than one reason. On the other side of the spectrum...under powered speakers will never sound as good as they should.
 
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Discussion Starter #3
You're right it was a waste of money but one saving note is the speakers weren't high end $$$ but enough for it to be a shame.
 

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I looked at the link you posted for the boom mat enclosures - they might be too small. There should be some reference (on or in the package) as to how much enclosure is needed for the particular speakers. Just a heads up. :wink
 

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Discussion Starter #5 (Edited)
I looked at the link you posted for the boom mat enclosures - they might be too small. There should be some reference (on or in the package) as to how much enclosure is needed for the particular speakers. Just a heads up. :wink

Already installed them. Perfect fit and used gorilla tape after I screwed them in.

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Thanks for the info Vindex. I'll be getting those same Kickers in the next couple weeks.
 

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Discussion Starter #7
Thanks for the info Vindex. I'll be getting those same Kickers in the next couple weeks.
I've found setting the iPod nano's EQ to off is the best sound. The Polks liked the Rock EQ setting the Kickers didn't.
 
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