PLACEMENT

AN IMPORTANT NOTE

ON HRS150 BASS

RESPONSE AND YOUR
CONTROL ROOM OR

LISTENING ROOM

You’ve heard it before. “Low-frequencies are non-directional, so it doesn’t matter where you place the subwoofer.” Although it is true that frequencies below about 100 Hz are non-directional, it is also true that a lot of factors can conspire to thwart the HRS150’s extended low frequency — including room shape, room volume, and acoustical treatment.

This is not a cop-out or an apology. It’s plain old physics in action. Here are some tips to help you find the best placement for your HRS150 and optimize the low-frequency response in your particular room. Consider the following:

Room acoustics and bass-handling ability

Nobody likes to buy a subwoofer and a new set of speakers and then be told that they should spend extra bucks on bass traps or a remodeling job. But the simple fact is, “standard” rooms, i.e., rectangular rooms in conventional business or residential structures, are rarely if ever conducive to optimal low bass reproduction without some modifications.

However, understanding what can cause

degradation of the low-frequency response in a room can help in choosing a location that can minimize the problems associated with poor bass response most notably interference and resonance.

Interference is caused when the reflected wave from the surrounding walls arrive out-of- phase with the direct sound. This can weaken or even cancel the sound. Keeping the distance between the subwoofer driver and any adjacent walls no longer than 1/8 of a wavelength (20 in. or 51 cm at 80 Hz) can minimize interference. Room resonance is caused by the reinforcement of certain frequencies between 20 Hz and

200 Hz, which creates “standing waves” or room modes. These resonant frequencies are determined by the dimensions of the room. The bass response is sharply boosted for a narrow band near resonance, and then appears to be attenuated between resonances.

Corner or Center Placement

Placing the subwoofer in a corner (corner loading) excites the most room modes in the room, which tends to smooth the individual peaks and dips caused by each standing wave. Moving the subwoofer outward from the corner along the wall results in fewer standing waves, but may result in noticeable peaks at certain frequencies.

Some people prefer to place the subwoofer between the left and right main speakers, so that all the sound is coming from the same plane. Some prefer to use two subwoofers and place one with the left speaker and the other with the right speaker. The Master Out/Slave In connections on the HRS150 allow you to do this quite easily.

Another benefit of corner placement is increased efficiency and lower distortion. The energy that is reflected off the walls reinforces the direct sound, putting less of a demand on the power amplifier to reach higher sound pressure levels.

It is important that the corner has good structural strength, or the low-frequency energy can cause rattling and other distracting vibrations. Experiment with the orientation of the

subwoofer. The driver in the HRS150 faces downward toward the floor while the passive radiators face out the sides. It may be helpful to play steady-state tones or pink noise while a partner moves the subwoofer (perhaps on a small wheeled cart), to make it easier to hear the differences in the sound as the changes in placement and orientation are made.

Principle of Reciprocity

One trick that has been used successfully to find the best location for a subwoofer is placing the subwoofer in your listening position. The principle of reciprocity says that you can find the best location for the subwoofer by switching places between the listening position and the subwoofer position. It is important that the cabinet be raised off the ground and at the same level as your ears. If that’s not possible, at least put the subwoofer in the same location as your listening position to achieve a close approximation.

6