Polk is trying to break a record for "The most innaccurate information about a subwoofer driver on the internet"... except (I suppose) for vaporware.
Let's start from the beginning. Some time in the past, I picked up a 10" Kicker driver from Best Buy as an emergency replacement for a failed driver in a Polk PSW-110
- It sounded really good to me, and having no knowledge that the DIY community even existed, I became excited about modular subwoofers. Back to Best Buy, where they had the Polk 12: DXi on sale, pre-mounted in a box
- for car use but very attractively presented. I bought one. Powered by a Crown amp, it sounded really good.
Fast forward a few weeks and I was messing around with several Polk 12" DXi and Kicker 12" CompVR subs, thinking myself in bass heaven. After having a few QC issues with the Kickers, I decided to use Polk to build out my subs. Wanting more, I looked at Polk's website and they pitched the 15" Mobile Monitor (MoMo) as their top sub.
From Polk's own website: "Through the use of high-tech carbon composite baskets, oversized voice coils, and state-of-the-art composite cones, we offer high-end audio performance normally found only in the most expensive loudspeaker systems."
Between then and now I learned a whole lot about bass and subwoofers and drivers. Eventually I realized the MoMo is a pure case of false advertising. Examine the official line from Polk - In reality the basket is made from plastic. The 2" voice coil is decidedly small for a high-excursion 15" subwoofer. The cone is also plastic (plain old polypro as far as I can tell), and rather heavy as well. That's not all - Polk's website listed the RMS of the 15" MoMo DVC as 425 watts, yet printed on the back of the motor is a 400 watt rating, and in their manual Polk gives the MM1540 a 360 watt rating.
Adding to the confusion, the product description for the MoMo on Crutchfield says: "The MM1540D 15" dual voice coil subwoofer handles up to 425 watts RMS, using a copper voice coil and neodymium magnet motor to drive the polymer cone with exceptional efficiency"
... well great because that's what convinced me to buy it! Neo motor, super-high efficiency! I dutifully entered their inflated spec for efficiency into WinISD. That's what left me feeling it was OK that the speaker had such a small magnet! I showed it off to friends and bragged about how awesome it was an American company could design something so light and powerful and economical. It makes me ill to think about it now.
So, thanks to the thread pointing to the MoMo going on sale for $89.99
, I decided to take a hammer and drill to mine. It worked fine, but I was not going to listen to it anymore and besides replacements are dirt cheap, if for some reason my suspicions were not confirmed. My suspicions were more than confirmed.
In practice the Polk 12" DXi is the superior subwoofer, but Polk seems intent to set the low bar for subwoofer value. Neither sub had the sort of sharp, brutally deep bass definition that hooks fiends. In fact neither Polk is as good as a 12" Kicker CompVR
The only good thing one could say: they are totally competent budget drivers, and commendably free of QC issues... but they don't plumb the depths.
So it is with some regret I post the following observations:
The MoMo has the black spider and the darker copper voicecoil. In the pictures of the motor assembly, the DXi is on the left, the MoMo on the right.
It looks like the same magnet on both speakers, a very modest ferrite magnet, the same one you find on all the cheapest 12" subwoofers like Kenwood and Pioneer. - so much for 'Neodymium'. The MoMo actually has a smaller pole vent than the DXi. The MoMo motor assembly weighs a few more ounces than the DXi motor - I attribute that to a bit of extra metal, resulting in the smaller vent.
The MoMo's cone weighs twice as much as the DXi cone, but only because it is thicker, not because it is stiffer. The cone is actually quite floppy and is almost exactly like a Frisbee in feel/stiffness. The MoMo's basket is plastic, not 'carbon composite'. The MoMo's spider is slightly larger but it's also quite a bit stiffer, as is the rubber surround. The MoMo does get a marginally longer voice coil - 1.15" vs. 1". The net effect is that the DXi actually sounds better, and might even be more efficient than the MoMo.
I do not recommend either speaker, however I cannot think of any other driver that so misrepresents it's specs as the Polk MoMo 15" - or the rest of the MoMo series. I still maintain it's 'built like a tank' in the sense that it'll take a beating and sounds decent... I'm just not under any illusions anymore. It was designed for yachts, and it was designed to be as cheap as possible to manufacture, The ferrite magnet is so disappointingly small for a 15", for a while I literally thought maybe it really is a Neo woofer but now I feel dumb for having been so naive. Thank you to the members here who threw their healthy skepticism my way a few months back when I was talking silly:mad:
Even the stated resistance is suspect, every other driver I've configured for 2 ohm operation worked fine with my Crown XTi amps, but the MoMo (and only the MoMo) would cause my amp to become unstable and clip in the most unpleasant manner. A thorough disaster and good riddance.
Polk's words - "The MM1540 15" 4-ohm subwoofer handles up to 425 watts RMS, using a copper voice coil and neodymium magnet motor to drive the polymer cone with exceptional efficiency"