An Easy Way To Solve A Complex Problem

Continue from where we left, this article is about subwoofer's setting.

Place your subwoofer where your primary seating area is. Connect it to your system and set the crossover and volume to a good starting point; we'll fine-tune that later. Use program material that offers a combination of sustained low tones and fast, powerful midbass. A good choice for this is the work of Les Claypool of Primus, especially that bands' seminal "Pork Soda" and the cut "My Name is Mud." If you prefer jazz, look to the work of Jaco Pastorius. If concert music is your thing, you may want to play one of the bigger works of Wagner. They key is to have a musical selection (or movie soundtrack selection if you'd prefer) that has lots of dynamic energy in the mid and lower bass from 150Hz to about 40Hz.

Turn the system on and bring the volume to your most typical listening level. Now get down on your hands and knees and crawl around the room slowly, listening for a change in bass quality, quantity and definition. Take your time. You want to find the spot in the room that provides the best integration of bass and upper ranges and the smoothest response. It is important to know that the best spot sometimes isn't along a wall or in the front of the room. Make sure you listen to regions throughout the room - and really listen for the integration and quality of the bass detail. In my own music room installation, for example, the subwoofer sounds best when placed as a coffee table between and in front of the primary listening seats some eight feet off the front wall!

Once you've determined the best potential location or two for subwoofer placement, change the layout. Put the subwoofer in that spot and go back to your listening position. Using the same tracks at the same volume, listen again. What changed? What needs to change? If the bass is a bit thin, perhaps move the subwoofer closer to the walls to reinforce the bottom end. If there is still a "hooty" or ringing quality, check to see if the distance from the subwoofer to the various wall surfaces is identical or multiples of a single measurement. Ideally, you want the woofer positioned from the nearest three room boundaries at distances that are as different as possible.

By now you should have found the location where the bass is the smoothest and most detailed in the room. It's time to integrate that bass into the sound field. There are various control schemes, test tones and equalizers available on most modern surround sound receivers. Using these built-in tones and an inexpensive sound level meter can give you a real advantage in setup. If available, follow the advice in your A/V receiver's owner's manual or subwoofer owner's manual for precise tuning tips.

Here is what I do to "dial in" my own rig. Select an NPR FM Station or quality digital video news feed featuring a deep male voice. Try to select a program source where there is as little dynamic contrast as possible - in other words the voice changes pitch (no monotones here) but doesn't span a very broad range from soft to loud. A great source program for this exercise is the speaking voice of Garrison Keillor from "A Prairie Home Companion". With the system playing at your average playback level, decrease the volume of the subwoofer all the way to the minimum. Now slowly increase the gain until the voice has power and loses any nasality. If you begin to think it sounds "chesty," as though the speaker were in a barrel, bring the gain back down. With a male speaking voice, you should not hear the subwoofer as a discrete sound source at all. Set up like this, the system will have maximum transparency and the most natural frequency response in your room.

One additional control is available, the phase control. Now some of you have probably twiddled this control back and forth, heard very little if any difference and so left it at the center detent. That's one technique. Here's a better way. Select a mono musical source, preferably a musical piece originally recorded monophonically and properly mastered on CD or DVD. One of my favorite pieces for this is the reissue of John Coltrane's "Soultrane" on DCC Classics, especially the track "Russian Lullaby."

Now, playing the soundtrack through the Dolby Pro-Logic settings, you should get output only from the center speaker and the subwoofer. Listen carefully to the interplay between the bass guitar, and bass drum or piano left hand. The impact of the drum is much higher in frequency than the deep, resounding skin sound. What you want to accomplish is to have the initial impact of Arthur Taylor's drum kit precede the deeper drum skin sound and the note from the bass guitar (by the way, it doesn't hurt if that note is lovingly teased from the instrument by Paul Chambers!). This establishes the correct phase relationship between your center speaker (and by extension your left and right main speakers) and the powered subwoofer.

By now your system should be sounding pretty good. Measure everything and get quality interconnects of the right length to settle this into a permanent installation and start thinking about how to treat the wall for the best performance from your surround monitors. That too will be part of the next installment. Till then, happy listening!