Since there's some speaker buffs here, I just thought that I'd comment on an intriguing new product line from Altec Lansing. I was walking through the Best Buy over Thanksgiving vacation, perusing the different offerings in the home audio and computer audio departments, when I noticed that Altec Lansing had introduced a new system in the $100-150 category. Usually there isn't a whole lot to get excited about in this price range, but the new FX-series from Altec Lansing does a couple things differently that I feel are worth mentioning.
The FX4021 is a 2.1-channel speaker system with two small, elegant 2-way satellite speakers with a 1" mylar semi-dome tweeter and a 2.5" cone midbass with a continuous-profile aluminum cone (most likely bonded to a paper cone behind it, though). The shape of the satellite speakers is a truncated square prism, and they have some nice-looking little stands as well. A square control pod is included, which I particularly like. It offers volume and mute control, as well as bass and treble adjustment. A large finger wheel provides the adjustment, while the changes are reflected in a small LED display around the rim of the finger wheel. Two other controls I don't typically expect to see on a speaker system at this price point are also present -- a 'loudness control' and something Altec Lansing calls SFX, which creates an expansive psychoacoustic effect. This effect causes the midrange to sound somewhat recessed, though, but I did not find this effect to be disturbing. The sound of the satellites can be quite natural with proper adjustment of the treble control, but it's also possible to cause them to sound shrill and harsh with the addition of too much treble EQ. The 2.5" midbasses exhibit a reassuring amount of excursion, letting me know that the satellite speakers work down to a decently low sub crossover point. There's plenty of detail retrieval here. At my neighborhood Best Buy store, the multimedia speakers are fed from a Sony SACD player, and I found the FX4021 satellites to be the best sounding ones in the price class. My own Cambridge Soundworks MicroWorks II satellites (which I use while at home instead of at school) have a slightly richer sound, but the FX-series satellites still have greater treble extension on tap than the MicroWorks' 3" full-range drivers, but both would be pleasant to listen to, and the FX-series offers the ability to dial-in your own frequency contour, which the MicroWorks do not. Lucky for the MicroWorks, they don't do much wrong in the first place.
The most intriguing facet of the new FX-series speakers, though, is the new subwoofer design. It's the only one in the price class that comes close to qualifying as a "true" subwoofer. As I listened, I was stunned at the real, deep bass coming from the FX series subwoofer's 5.25" cones -- this was even deeper bass than Altec's VS4221 which were sitting right beside, with their 6" subwoofer driver. The unconventional styling of the FX4021's subwoofer hides another unconventional technique, which is the secret behind the truly deep bass I was hearing. To tune a subwoofer to a low frequency, typically a large enclosure is needed, but a small enclosure with a very long bass port can be used to achieve the same tuning frequency. However, this small enclosure tends to produce a much higher acoustic impedance on the back-side of the driver, restricting the cone motion and requiring a large amount of force from the driver's motor. When the enclosure used is too small, the response curve appears to gradually roll off instead of exhibiting the proper vented box cutoff characteristics. By taking two drivers and coupling their diaphragms together, it is possible to produce a driver with twice the motor strength and suspension stiffness acting on the same amount of diaphragm area, allowing the required enclosure size for a given tuning to be reduced by half. This method of coupling two drivers together is called Isobaric* loading, because it creates a tiny chamber of constant pressure between the two driver cones, which is about as effective as coupling the voice coils of both drivers. Sometimes both drivers are facing forward, and an extra chamber must be built into the enclosure. However, another method of achieving Isobaric coupling is by taking the second driver and mounting it face-to-face with the first driver. Then, the second driver is wired out-of-phase with the first one, so that when the electrical signal is applied, both cones move in the same direction, even though both drivers are facing each other. This is called Isobaric Push-Pull, because one driver pushes while the other driver motor pulls. This has the added effect of canceling out asymmetries in the motor's magnetic field or the compliance of the drivers' suspension, lowering the distortion produced by the drivers when they are driven hard, for bass that's both deeper and cleaner. Isobaric push-pull doesn't double the effective diaphragm size, so it doesn't double the efficiency, but it does double the thermal power handling. The FX4021 delivers 24 watts to the subwoofer, but this is enough. It's possible to overdrive the subwoofer into "wubba-wubba" distortion by cranking both the bass controls and the loudness control to the max, but by this point the balance of the sound has already been shot to heck by the tweaking required to push the subwoofer into mud. On a heavy techno track, I managed to generate wind noise in the subwoofer's port. This sub is capable of generating a lot of air movement, but if you push it too far, you'll get both the Wubba-Wubbas and "Chuffing" from the port.
If you know about someone who loves to listen to music on their computer, but blasts it at high levels through ultra-cheap $30 JUSTer or OG speakers, this system would make a great gift for them. Or anyone who would enjoy decent sound from their computer. A 5.1 version is available, which steps up to 6.5" woofers in the subwoofer. I can only suppose that this further improves the already amazing bass for a product in this price range.
Here's a review of the FX4021 system, though the reviewer hasn't a clue about what is happening in the subwoofer. The main value is the pretty pictures.
*The proper spelling of the word is Isobaric. Sometimes, you will see this technique "Isobarik", because the Linn Products Company offered a loudspeaker using this principle, called the Isobarik. Linn has been known for their funky product names, but in this case we aren't referring to the Linn product, but to the design principle.