Customer Ratings & Reviews

Great sounding speaker

Overall this speaker has a nice warm sound that gets better and better. I have only had these for a week and they get better bass extension, although it isnt completely needed because I have a sub. I purchased these the 6.5 components, and the 6x9 polks as well they sound great together. I have a 12 inch kicker L7 solobaric and these speakers keep up the bass doesnt over power them.

Pros Great customer service and quick shipping clean sound, with crisp not overall bright highs perfect sounding.

Cons: none really they sound great

Polk MM521

I put these in my 2006 Harley Davidson Electra Glide Classic running the stock radio w/o an amp. They are a huge improvement over stock, and have amazing clarity and bass. They do get louder with use. I had to ziptie the crossovers to the fairing supports, which was no problem. I had to remove the little speaker covers, but the speakers look cool. I've washed the bike and they've been wet several times with no issues. I may try a small amp with them for more sound and clarity at speed! Highly recommend!

Polk Audio MM521 Speakers

I have used many brand marine stereo speakers and these are by far the best sounding speakers that I have used. Have installed about 300 stereos in golf carts and now this is the only speaker that I use.

MM521 = Great speakers.

I have these speakers in the fairing on my motorcycle. I have not heard better sounding 5-1/4" or smaller speakers. They play loud and clear, with great highs, and surprisingly good bass. They far surpass the stock speakers. Plus, they are waterproof.

Great Speakers!

I have to say I received great customer service. I ordered speakers for my 09 HD Street glide. They installed perfectly and sound great, so much better than the stock speakers. I would recommend these speakers to anyone.

Great sound and lightweight!

I purchased two pairs of these speakers and the sound is phenomenal. I bought them for a 2 seat roadster with a very loud cabin and they have done very well on only head unit power. As a plus, they're very lightweight but sturdy. I'd highly recommend them.

Polk is it

Awesome speakers for my topless Jeep, got rained on several times and NO problem.

Polk Audio MM521

Works Great, I have had these installed for more than 6 months. Even though they have the correct size for a Plymouth Voyager, they are a little too tall. I got them mounted, but not recommended for this minivan...they sound spectacular though!

pretty damm goof

Very tight sound, awsome looking speaker as well. Good bass level from such a small speaker.

MM521

This product is the standard everybody is trying to match. Great stuff

Polk MM521

I have these in my boat wired to a 2 channel 120watt amp and they sound awesome..Def recommend them

Natural clarity

I bought a pair of MM521's to go with a pair of MM921's & MM461's. Two months after installation & breaking them in. I have to say the sound is impeccable! All of the speakers work seamlessly in my '92 DeVille. The imaging is great, & music is natural. If there isn't much bass in the material, you won't hear it. If there is, these will bring it. As an ensemble, I can't see how these can be beat! I can only imagine the sound when I install the sub-woofer & amp.

quality 5 1/4 in. speaker

to me, these mm521 speakers sound great. have quite a collection of 5 1/4 in. and 4 in. 2 way speakers I didn't like. using these for front dash speakers on a early jeep tj wrangler with pioneer 100 rms watt x 4 ch. amp. setting front filter on amp. to cut some base for higher higher volumes. they will make the dash vibrate. my front speaker quest is over. a little over priced but recommend these speakers.

boat

The speakers sound awesome and just have them running off of the head unit highs and mid have great sound getting ready to add more speaker to the boat this winter going to amp these speakers and see what they can do.

Buy these

Best speakers for the value by far. its honestly not even close. Ive owned so many different pairs of speakers and I can tell you with no bias, that these speakers are in a class of their own. For the price you will not find better i promise you. they sound amazing, crystal clear with no noise. do yourself a favor and order them as soon as possible, so they get to your door quicker. there is honestly no need to look around any more

Killer little speakers

I'm running 4 of the mm521 with 4ch 2 ohm sound stream 320 amp thy true 80watts rms per speaker. Gains is little under half way . They are in front fairing on my custom Harley roadking. I installed foam cup baffle on back of speakers to help bass . I can honestly said I'm impressed with this setup. I set gains with volume on head at 43 of 50 . I can run on highway At 80mph and set volume to 35 this is LOUD &CLEAR 👍🏼👍🏼👍🏼
Friends have be totally surprised at how good this setup is .
I hope this hold up to Rock & Roll
Score durability at 4 cause I've only been running them month .

Rear door gmc envoy

Good crisp sound produced from the back doors as fill for my front staging. Worked well with existing mounts and simple to wire up. Depth of speaker allowed plenty of space for window to come down.

Great speakers

Polk makes a great marine speaker. I won't use anything else.

Great speakers at reasonable price

I put these in the fairing of my motorcycle, sound is crisp and clean, much louder than the stock speakers with zero distortion.

Great little speaker

I installed 4 of the mm521 in fairing of my Harley. It's being pushed by 320rms amp 4 x 80 watts. . They sound great and have surprising good bass for size. The sound azamimg at 85mph on freeway too,

Great sound!

Very good sound with minimal distortion when turned all the way up, highly recommended!

Great sound

These sound great with little to no distortion when turned up high

great buy

best speakers for the price. put them on my bike and look and sound great.plus fast shipping

Great Product

The brand speaks for itself. I would not get any other type of speakers. The brand takes a lot of abuse. My car is Polk MM although the way around.

Polk audio mm521

Awesome product really loud and clear , the design looks really good too

excellent speakers.

Top notch sound and even some decent bass from these speakers. Best 5.25" speakers I've ever heard. I have them with Alpine SPR-69's and a Boss PV 3700 amp (which is an amazing amp for the money by the way) and the sound is so loud and crisp and clear. The sound of this system is way louder than I can take and remains perfectly clear. I've had a lot of car stereo's and I learn a little more from each one. This combo of speakers and amp are by far the best I've ever had, and didn't cost a fortune either. Loving my driving! Thanks SonicElectronix, I couldn't have afforded a system like this without you.