Where is the best place to position the subwoofer in a room?

The best place to position a subwoofer can only be determined by careful measurement by an experienced acoustic engineer using the appropriate acoustical measuring tools. When measuring a subwoofer system you are looking for a smooth extension of the frequency response from the main loudspeaker low frequency cut off (85Hz when using the internal subwoofer crossover) down to the subwoofer low frequency cut off point. Positioning the subwoofer correctly is part of the solution but the other major part is adjustment of the controls:

• The subwoofer response can be altered to adjust for the level of the subwoofer relative to the main loudspeakers
• There is often a room interaction around the subwoofer low frequency cut off so this can be attenuated
• There is the phase control which delays the subwoofer in 90° steps to ensure that there is no cancellation at the crossover frequency due to the physical distance between the subwoofer(s) and the main loudspeakers

After measurement the subwoofer often ends up placed close to the center of the front wall so this is a good place to start whether you have a measuring system or not. This gives the following benefits:

• Increased acoustical loading from the front wall and floor
• No cancellations from the front wall and floor
• An good excitation of all the low frequency room modes giving a good frequency response

If the sound is still not quite right then try the following:

• Move the subwoofer slightly to the left or right off-center so that different room modes are excited at different levels
• Add a second subwoofer and place two subwoofers asymmetrically (relative to the side walls) against the front wall to excite different room modes at different levels. A useful by-product of this is the efficiency generated by mutual coupling
• If there are two subwoofers then try moving them to the front corners as this sometimes helps with problematic rear wall reflections

One additional advice:

• Place the subwoofer in the reference listening position and move the measuring microphone to different possible subwoofer positions to see which one gives the best response. This is called subwoofer reciprocity principle and works because the frequencies that subwoofers produce are omni-directional. It is easier to move a small microphone around than a heavy subwoofer!