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Polk MM651 Speakers
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The Polk MM651’s are very easy to install, you simply mount the speaker, connect the crossover to the appropriate spade lugs for the mid and tweeter, and connect the amp. No adjustments are possible.

MM651_Profile_optAfter installing the system in my listening room’s panels, I connected them to my reference amp and did some listening. Beginning with the Marc Cohn tracks “Walking in Memphis” and “Perfect Love”, I was quite surprised at the high level of sound quality considering the price. The system had very good warmth and clarity. I thought the upper midrange was ever so slightly accentuated, but nothing approaching strident or unpleasant. And when I sat off axis, this was much less noticeable, so perhaps the engineers at Polk realize that most of these speakers are going to be placed low in a car door, and simply designed for it? 

Moving on musically, I listened to Robby Robertson’s “Somewhere Down the Crazy River”. The opening of the song has a sense of space and movement that few car audio speakers can capture, but once again, the Polk’s surprised me with a really decent reproduction of the recordings ambience. I listened to a bunch more stuff, as I generally do when I’m enjoying myself. From AC/DC to Valdy, the Polk’s handled it all in stride, and did very well. Couple these speakers with a decent woofer, and you’ll have the entire spectrum well covered. If I was to really pick nits, I thought there was a hint of sibilance from time to time, especially when pushed hard, and the minor issue in the upper midrange would occasionally make a snare drum or sax riff have a tiny bit more bite than it should but these are small complaints indeed. I had to repeatedly remind myself that these Polk speakers were under 200 bucks, and at that price, they’re exceptional!

Technical Measurements 

With the listening session over, I moved the system into my loudspeaker measurement room, and measured the on-axis frequency response. The system is quite flat, with a small bit of a dip around 8500Hz. The dip is narrow enough to be of little consequence, but it may explain a bit of what I heard earlier.

As you can see from the system impedance graph, the MM651 does have a bit lower than normal impedance but certainly won’t pose a problem even for a head unit amplifier.

As a function of how I make a living, I listen to somewhere around 150 different pairs of coaxial, component, or home loudspeakers a year. At any given time I may be evaluating speakers ranging from $29.95 bargain special computer speakers, to multi-thousand dollar, esoteric home transducers.

When a pair of speakers comes across my bench as good as these for less than the cost of a night out on the town, it’s a rare occurrence indeed. If you are in the market for reasonably priced high performance replacement speakers for your ride, you should check out the MM series. Based on the performance I’ve seen here, it seems Polk’s reputation for providing excellent speakers at reasonable prices is going to continue.