The center channel is wider than the satellites and also serves as the control pod for this 5.1 system. Being wider, there is room for the many controls on the center channel, included the power button, main system volume, fader (to control the volume of the rear channels), center volume, the "Matrix" button and a headphone jack. And, keeping with Logitech's speaker theme, a bright blue LED is present between the fader and center volume controls.

   The first four controls are fairly straightforward. Having a fader allows you to adjust the rear speaker volume depending on where they're positioned relative to the front speakers, and the center speaker volume serves a similar purpose.

   The "Matrix" button is a bit less clear in its function. The Matrix feature allows you to get center channel sound from a 4 or 2-channel source. It does this by considering the front left and right speaker signals, and the effect is pleasing, especially when listening to music. However, unlike the M3D function of the earlier Z-540s, this won't allow you to get sound from the rear speakers if you do not have at least a 4-channel source.

   There are four cables which come out of the back of the center channel, and one of them is a thick cable which terminates in a DB-15 type connector that attaches to the subwoofer.

   This DB-15 cable carries the front left/right and rear left/right signals to the sub where the signals are then sent out to the appropriate satellite. The cable also provides for control of various volumes and settings.

   The other three cables from the center channel are bound together, and they are the inputs which attach to your soundcard or another source. One is for the front left/right signals, another is for the rear left/right channels, and the last one is for the center/sub signals.

   The input cables are quite long, so you shouldn't have a problem placing the center channel in reach of your soundcard. As mentioned before, the source to which you are connecting the Z-640s to must be able to decode and output the signal into three stereo or six discrete channels; if you just have one digital output that requires decoding, then you'll need a decoder to do the work.

   I would have preferred if the inputs terminated in a straight 3.5mm stereo jack, rather than a L-shaped one, as this can create fitting problems at the back of your soundcard, with the output jacks so close together.
 

   The four other satellites are also mounted on metal stands, which can be reversed by loosening the screw at the back if the speakers are to be mounted on a wall. In this case, the two holes in the front, where rubber feet are, serve as mounting holes where screws can hold the stand to the wall.

   The thick cables which run to each speaker are hardwired into place, and terminate in a RCA-type male connector. The cable length for the front speakers is a bit greater than 5', while the rear speakers have about 15' of cable length. For this type of speaker system, these lengths should be enough as it isn't likely you'll be using these to fill a large room.

   The four speakers are identical to each other, and I believe they are the same as the satellites of the earlier Z-340/Z-540 systems from Logitech. Each of these speakers plugs into an output on the sub, and each of the outputs on the sub is labeled and color-coded so there can be no mistake during setup.  

One of the satellites.

Port on the rear.

Side view - satellites point upwards.

  The speakers are quite small, and should have no problem fitting on your desktop as they take up roughly a 3" x 3" footprint. They are angled upwards, as are most speakers, and they have a port on the back.

   I think that the metal stand that they are mounted on signals a level of quality that Logitech will not ignore, despite this being a "value" 5.1 system. There are three rubber feet on the bottom to keep the speakers in place, and they work quite well.

   For those of you using this system for a console, Logitech has included a RCA to mini-stereo adapter that will allow your Playstation 2, Xbox or GameCube to be used with the Z-640s. This addition should be welcomed as it acknowledges that these speakers can be more than just a PC system, and expands their usefulness.  

Bottom of stands	Install guide and console adapter.
. Adapter inputs.	Adapter outputs.

Testing:

   I've been using these speakers for almost every day for about three weeks now, and I have a generally good feeling towards them.

   In action and FPS games, such as Battlefield 1942, UT2003, America's Army: Operations and the Medal of Honor expansion, the experience was great. Explosions were represented with a resounding bass from the sub, and bullets seemed to truly be flying by in all directions during a game of AAO.

   The level of immersion during this game could not have been reached if it were not for these speakers and the powerful sound output by the bass. Using the "Matrix" to create a center channel during these games provided a nice effect, as well. In UT2003, the voice of the announcer was projected with much immensity, and the weapons' sound effects were reproduced with admirable results.

   The Z-640s' performance with music was somewhat less consistent. For Jazz and other instrumental music I found the Z-640s to be lacking in the midranges, and this made the low frequencies of the sub seem overemphasized. The brass instruments in "What's Next" from BBVD just sounded less "full" than what I've heard on other speaker systems.

   However, the bass performance of these speakers cannot be denied; for rap and other music with a heavy beat, these speakers perform quite well, enveloping you in the bass.

   The Z-640s seem to be at home in bass-heavy environments. One thing that you'll want to note is that the "Matrix" feature won't allow you to use the rear speakers if you only have a 2-channel output. They only create a signal for the center channel from the two front channels.

   I would have liked the Z-640s to have a feature similar to the "M3D" feature found on the Z-540s that did allow you to use the rear speakers with the 2-channel output of music.

   For DVD movies, the center channel helped to project dialog during some scenes, and also intensified the action of a lightsaber battle in Episode II: Attack of the Clones. Again, the bass played a major role allowing the flybys of various spacecraft/vehicles to seem more close and more real.

Conclusion:

   While the sound from the Z-640s is not perfect, you'll be hard pressed to find a better 5.1 system for this price. While the midranges were lacking, they were by no means horrible; in fact these speakers sounded better than some models which cost more than the Z-640s.

   What I can express negativity about are some minor things that could have been designed better. Firstly, the bass volume control on the sub presents the annoying problem of having to get down on the ground to adjust bass levels depending on the usage of the speakers, as you'd perhaps want more bass while watching a movie or playing a game than when listening to certain genres of music.

   Secondly, the mass of wires, especially the thick control cable which goes to the sub, which comes from the center channel tend to pull it in the direction of their travel, and this can be a problem especially when the center is placed on top of a monitor. I would have liked if at least the inputs went to the sub.

   Thirdly, the inputs should have terminated in straight stereo plugs rather than L shaped ones - The L shaped ones, IMO, don't do well on the back of soundcards, where the multiple inputs are placed so close together.

   And, lastly, I found the control knobs on the center channel to have a bit too much resistance for my liking; however, this is a personal preference.

Pros

• Easy to setup

• Bass is excellent in both movies and games

• Center channel provides nice effect in both games and movies

• "Matrix" feature creates a center channel when you only have a 4-channel source

• Price - An inexpensive 5.1 solution

• Console adapter allows use with Playstation, XBox, GameCube, etc.

• Metal stands allow wall mounting

• Headphone jack is nice

Cons

• Midranges not well represented - evident in music

• Volume knobs perhaps have a little too much resistance.

• Center channel tends to be pulled back by the cables coming from it

• Bass volume on the sub

   While I have said a lot on what annoyed me about these speakers, in the end, I was pleased with them. At their price, I can see no alternative to a 5.1 solution that produces such thunderous sound. My complaints, which for the most part, have amounted to quibbles, do not present a major reason against the viability of these speakers.

   Finally, thanks to Logitech for providing these speakers to me for review. This review would not have been possible for them, and I thank them for allowing me to do so.