5 1/4-inch coaxial loudspeaker
5 1/4" coaxial
Designed to Perform
Through the use of high-tech carbon composite baskets, powerful neodymium motor structures using oversized voice coils, and state-of-the-art woven glass composite cones, we offer high-end audio performance normally found only in the most expensive loudspeaker systems. In addition, these space age materials offer weight savings that can mean higher performance for your car or boat. Don’t settle for factory-installed sound!
Space age materials reduce weight of components while offering rock solid reliability, advanced looks and ultra high performance.
Neodymium magnets a rare earth metal offering exceptional strength to performance ratio, found only in the most exotic speakers, saves tremendous weight. Don’t let the sound system weigh your vehicle down. Since the magnet is smaller, the speaker can fit into more applications.
Carbon composite basket based on the spokes of a wheel is lightweight, will not flex during peaks and looks great! Don’t be afraid to show off the back of your speaker.
Woven glass composite cones feature tremendous stiffness-to mass ratio. Lower mass means faster transients and finer detail.
Klippel optimized components using a state-of-the-art Klippel distortion analyzer, Polk engineers were able to optimize the woofer’s motor structure, voice coil alignment and suspension for the best possible performance, even at extreme listening levels.
Large-diameter voice coils (30mm) in drivers increase reliability and power handling capacity.
Swivel mount tweeters allow precise aiming of sound.
Stylish grille is included.
All Polk products are made using the best materials and the most advanced manufacturing techniques. They pass the industry’s most exhaustive quality tests, including drop testing, extreme signal response and UV & salt exposure testing. Polk loudspeakers are built to perform for a lifetime.
|Mid / Woofer|
|Diameter||5 1/4" (13.34cm)|
|Type||Dynamic Balance driver with poly-composite cone|
|Total Frequency Response||50-25kHz|
|Nominal Impedance||2.7 ohms|
|Cut-Out Diameter||4 5/8" (11.75cm)|
|Full-Range Mounting Depth|
|Top Mount||2 3/8" (6.03cm)|
|Bottom Mount||2 13/16" (7.14cm)|
|Unit of Measure||pair|
|Speaker Warranty||1 year parts and labor (original purchaser)|
Specifications, dimensions and features subject to change without notice. For more information call us at 1-800-377-7655 (USA and Canada). Outside of North America call +1 (410) 358-3600.
3 reviews with an average of 4.5Write your own review
by Dennis, November 1, 2009120 out of 180 people found this review helpful.
Very crisp highs and strong midrange. Excellent crossover phasing for perfect sound.
Plastic cage, be careful mounting. Check mounting depth.
Having excellent past experience with db series components I had my heart set on Polk audio speakers two ways for this tight install. When I listened to the mm series on display I was really amazed by the deep rich sounds comming from the midrange and the crispness of the highs. MM521's do need a little time to break in because of the composite materials. When you first install them they have little bass but they will not distort. Crank them up when you set your amplifier and within a couple of hours of listening you will be amazed at these powerful little two ways. Be careful mounting these speakers because the cage is made out of plastic. Make sure that all of your mounting hole line up perfect or you will crack the cage. Do not be alarmed however, the plastic cage is much more rigid then a standard metal cage and you will not be disappointed by the build quality.
by Volvo DaN, September 2, 20123 out of 3 people found this review helpful.
Separate crossover, not attached to speaker for component quality sound; 1" Tweeter; small size magnet on back; lightweight overall but tough
Single hole (not slotted) attachment flange; Basket doesn't taper for 1", potentially makes fit a challenge
Seems like an under-rated speaker. The plastic basket may turn some people off but it has advantages: water-resistant and won't rust, lightweight so there is less stress on attachment every time door is slammed (if used in door). The plastic frees up basket design so Polk makes the spider the same diameter as the cone; I know just enough that this maximizes the bass capabilities of the speaker. The only disadvantage here is that this large spider makes the basket start perpendicular to front flange and only tapers after 1". For some applications it may be a problem, likely in an older car (mine is Volvo 740 1986, had to cut door metal). On the other hand the main speaker magnet is lightweight and compact neodymium that makes the back-side compact and unobtrusive. This is where the weight is significantly reduced but all the benefits of a strong magnet is still retained. The speaker mounting flange only has single holes; it's not slotted. I think that is partly because it's plastic and will reduce breakage in odd attachments; also it's kind of a message from Polk: you better know how you're attaching these puppies. Again, probably many applications this is non-issue. Crossover is separate box, not attached to speaker basket. This allows better and bigger capacitors for crossover and means better sound. It's essentially component speaker style set-up except that the tweeters are permanently mounted. Build quality is excellent all around. The 1" tweeters sound excellent and sound relaxed even after driving continuously for 2-3 hours. Bass response is all that one could ask for in a 5.25" driver. Definitely allow 15-20 hours to break-in both tweeter and woofer. The longer I play these the better they sound! Welcome to the future of car speaker design: It Is Here.
by John, June 17, 20132 out of 3 people found this review helpful.
Durable with great sound
Bass could be better
I've had these installed on my Harley Road Glide since 2009 and they are awesome. They have performed awesome, even in down pouring rain, and continue to work without any issues. I just installed a Hawg Wired amp and they sound even better. Absolutely outstanding speaker for the money and totally underrated. They do distort slightly with it cranked all the way but I expect that a bit. The bass is not thumbing but it's a 5 1/4" speaker so you have to expect that as well. Sounds great cruising down the highway at 80 mph (breaking the speed limit a bit).
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