Conclusion: I purchased these speakers for motorcycle use. Very happy with the increased clarity and volume over the OEM speakers. Upgraded the speakers from OEM and did not install an amp. I am sure the next move is to bring more out of these speakers by installing an amp.
Conclusion: I couldn't wait to get these mounted on my road glide, but the HD shop told me the wrong size speaker for the cowling. I'll find a use for them. They look great. Have ordered the correct size Infinity speaker. Have a buddy who has the Polk's and his system rocks. So this will be a review of his street glide with the db521s.
Conclusion: I bought 4 of these speakers for my motorcycles batwing. After I installed them, I took them for a 4 hour test ride and they sounded great. I ran an amp to them 50 watts each and they handled it. They look great too. They do sound better in a sealed enclosure, you can direct the tweeter where you need it and this helps a lot when installing at weird angles. For the price I'm glad I went with these speakers , Darren. Hanford, California.
Conclusion: I bought these a couple of months ago to put on my motorcycle. Finally got the chance to put them on today. One, they did not fit my application (which is fine). But, I just hooked one up to see what it sounded like, and the tweeter was almost non-existant. Not good on a motorcycle with loud pipes/wind. I have some cheaper Kicker CS40 speakers on the bike now (what I could buy on short notice before a trip last year). Those sound way better!
Summary: In my 2006 Dodge Ram regular cab truckI have a pair of Polk 6X9 in my doors and a pair of Polk 3.5 in my dash. I saved a little money initially with some Sony 5.5 behind the seat. MISTAKE Within or right at a year, the Sony could not keep up. I got these Polk 521 to replace them with and oh what a difference! Such clean sound! I can actually turn it up a little louder and it still sounds great! I will never buy another pair of Sony speakers again.
Pros: Sound absolutely great! I had them installed as I'm not inclined to take the time to do that. I have a much cleaner and stronger sound coming from behind the seat now to complement the rest. Everything about this purchase was good so far.
Cons: When i find one then I will have to change this review. There are no downsides yet.