4200e Setup and Configuration
Working in conjunction with good room acoustics, speaker placement is always key for attaining the best possible sound in a home theater setup. To get the most out of the Atlantic Technology 4200e system we recommend toeing in the speakers towards the listening position, though not as much as is indicated in the user manual unless you are spreading them farther than 8-9 feet apart. The off-axis response of these speakers is above average. You will likely not be able to horizontally align the tweeters perfectly across the front three channels unless have an unusually high-mounted projection screen system. Do your best and at the very least be sure to angle your center channel down (or up) at the listening position using the included base.
I performed my standard distance and level setup using the Yamaha RX-V2500's YPAO system (with room correction disengaged.) I was sure to override and set the crossover point to the THX recommended 80 Hz. I also verified the finished level adjustment by using a Radio Shack SPL meter and running the test tones manually from the receiver. As usual, the Yamaha system nailed the distance and levels perfectly. If you are not fortunate enough to have YPAO, simply sit in the listening position with the Radio Shack SPL meter held directly in front of you and pointed at the ceiling. Some people use a mic stand and back away from the RS meter to set levels. This is great... if you plan on listening to your system from behind the couch. If not, then use the readings the SPL gives you as it will take into account your body in the listening position. If you are using an RS meter for setup you may want to play with the sub level after you put in some music or movies and adjust a couple dB to taste.
Setting the subwoofer will likely be an easier task in a THX Select system as opposed to a system having, for example, larger tower speakers with low frequency extension. The reason for this can be attributed to the fact that for the main channels, a THX system rolls off frequencies below 80Hz and sends them to the subwoofer, simplifying the number of problems that can result from having lower frequencies originating from both your mains and sub. If you find that you successfully place your subwoofer in half the time you expected, thank Atlantic Technology and THX for the time saved.
The 4200e SR (surround) speakers were located on the side wall of reference system 2, so we configured them as dipole for a more diffuse sound. There aren't too many cases where we'd recommend bipole operation for these speakers, except perhaps if mounted on a rear wall or if used primarily for gaming or multi-channel music playback (and this would be something to play with to get the best results). If you happen to switch them back and forth be sure to rebalance the levels as they are likely to change. We found that the nice diffuse soundfield was a good compromise and offered a convincing surround stage. You should also note that the Atlantic Technology manual shows a drawing of two possible placement options for the surround speakers, not the correct placement for a 7.1 setup. If you intend to do 7.1, we'd recommend an additional set of 4200e LRs (or perhaps 4200e SRs set in bipole mode) for use as back surrounds, placed approximately 2 feet apart.
Boundary Gain Options and Adjustments
This is a tough cookie to crack if you're on your own, so get a patient friend to help you with this tweak. We described earlier what this function does and, while it's a subtle change, it's very helpful to set correctly if you want to get the best performance from your system. Obviously, you'll want to stay away from multi-channel content when setting the boundary gain switch on the main 4200e LR and 4200e C speakers. I chose Jam es Taylor's Greatest Hits CD and listened to the mid to low frequencies in the guitar, the bass guitar, and to some extent his voice. This is a quick and easy place to listen and hear how the boundary compensation adjustments affect the output signal. If you are hearing differences in the high end you're likely dealing with a combination of harmonics and psychoacoustics as the adjustment only directly affects frequencies at and below ~250Hz (see our measurement graph.) My preference was to leave the boundary compensation off provided the 4200e LR was at least 2-3 feet from the back and side walls. If you are positioning it near a television or side/corner wall you will want to experiment to see what sounds best in your room. We would also likely recommend engaging the BC switch for center channels positioned on top of RPTVs or if enclosed in shelving or any kind of cabinetry. Honestly, however, the difference is so subtle as to be almost indistinguishable at normal listening levels - we're talking 2-3 dB max from the center and half that for the mains. In addition, trying to listen to boundary gain differences from the center channel while in the midst of a multi-channel music track qualifies you for a "golden ear" award. You may want to disconnect the other channels, but at the risk of creating a non-real world environment. The bottom line is: have fun with this option and use it to match timbre and tweak your system to your own personal taste.