Polk RM6900 £1000
30th Jun 2005 | 23:00
Polk makes a step in the right direction
Life is like a box of chocolates. You never know what you're gonna get...' According to Forest Gump's Momma, anyway. But with this box of Polk candy, you can be sure that while it's all packed in layers, you know it's a full on 5.1 speaker system in there.
Nestling in polystyrene homes are five speakers, all the same ovoid cross section but two shorties and three longer jobs. There is a selection of plastic mounting brackets, centre stand cradles and wall mount brackets, as well as a pair of what are termed desktop stands.
The three larger enclosures each have two 3.5in drivers in them, with rubbery surrounds and high compliance cones that seem happy to move to and fro a good old way for their diminutive size. Between the two drivers is a silvery soft dome tweeter. Both speaker sizes are described as Dynamic Balance designs. The same drivers are used in the shorter rear versions except that there is only one driver to go with the tweeter.
The porting in all five is described as a 'Powerport' and reminds me strongly of the underside of certain subwoofers. This is because of the thing sticking into the port. First off, the tube that reaches into the plastic baffle of the enclosure is not 'gas flowed' or particularly curved at either end, inside or out, but it does finish on the outside with a sort of scoopy shape, sculpted out of the enclosure. When the cloth and plastic grilles are in place, the exponentially curved pointy bit fixed to the grille is held so it sticks neatly into the hole. This provides a smoother flow of air in and out of the port, to reduce any of the chuffing sounds.
If you design your own bass box with a computer program the results will include the speed of air in the port as well as offering you a computer generated curve of predicted output. If the air movement exceeds Mach One it produces its own chuffing sounds. If however, there is a more pressurised and controlled laminar (or smooth) flow dictated by the port-probing point, this chuffing can be reduced and here has clearly been used to get phenomenal air movement through the port of a tiny speaker system for it to produce bass well above its fighting weight.
As for the bass, you need to take out a second layer of moulded polystyrene and there you will find a cunning subwoofer, lying upon its side. Polk is renowned for making Quart-in-a-pint-pot subwoofers. These are small designs that utterly beggar belief in what they can do with the limited cubic capacity allowed and the, commonly, 6in drivers used. But this is largely based on serious acoustic gain enclosure principles, and good woodwork costs far more than big ugly drivers, so the designs ain't cheap. However, Polk has moved forward to keep this sub bass system up to a reasonably high standard but also allows its kit to compete on a price basis as well as on its reputation as a performer.
In a simple-seeming but inspired mode, this sub has a small frontal drop but extends back a bit and mounts a serious 12in driver in its flank. This sealed box is not vast but is big enough for this driver to work well down to 35Hz and be relevant a lot lower than that, pumping upon its own built-in 100W RMS amplifier, all running at 4ohms. You can input and output in stereo at speaker level, use L&R phonos, or simply a mono LFE feed. It's equipped with frequency and volume potentiometers, as well as a 0-180 degrees phase flip switch and on/auto/off overriding power switch as well as the regular mains on-off switch.
The five speakers can either stand up on a flat surface via centre cradle, rubber dots underneath rears, or else the desktop stands for the left and right. The terminals of the speakers are a bit twiddly, being plastic 4mm binding post types but the idea is you'll only have to use them once. The 'desk top' stands are heavy, with circular bases, and look good. Fitting the speaker wires is a bit annoying, as you cannot simply throw 4mm banana plugs at them.
'You're a better Buzz than I am!' So says Lightyear-san to Rex as they play a video game at the beginning of Toy Story 2. Remember that awesome high-res game clip? It contains some wildly stressful soundtrack elements, too.
The performance from this Polk set can be startling. I especially liked the centre. A double bass was seemingly fixed in the centre of the room for my reference music DTS test. The tweeters are fast, sweet, lively and affording, to female vocals in particular. The sense of space is perfectly recreated and the low end is satisfyingly heavy, even for so small a woofer. Turn it up too loud and it sounds a bit congested but at normal levels, stuff like Buzz's breathing sounds are amazingly detailed.
The Polk name once generated quite a lot of excitement in the UK, but distribution problems have reduced its visibility. With this new RM system it once again appears to be getting its house in order.
Competition in this arena is fierce, and while this set might appear to be slightly overpriced against some of the competition, its powerport design obviously works well, and on this system delivers seamless bass integration. Well worth auditioning.