Page 9
SV Subwoofers
Parametric Equalizer
Important enough and challenging enough, this feature gets its own section! “PEQ” al- lows you to tame a “peak” in your room’s response. Peaks are quite common, especially in large rooms or ones where your sub is far from your listening position. NOTE: A Sound Pressure Level meter is a must for proper use of the PEQ, so get one before you tackle this control. TO DISABLE THIS CONTROL: Set the “LEVEL” control in the Parametric EQ feature until it stops on “MIN” — thus ensuring you do not inadvertently cause poor frequency response until such time as you properly configure the PEQ.
First you might ask yourself, “why use a PEQ?” The reason is quite simple. Your room. See, most times even a superlative subwoofer which measures very evenly (we say “flat”) in an open domain (no reflective boundaries) will not measure the same in your home theater or music room. Instead, colliding bass waves can build up and cause a “peak”. This is where a parametric equalizer helps out. A PEQ is an electronic circuit which al- lows the user to manipulate the input signal so the acoustical output is more desirable for their environment, in many cases allowing the worst peak to be “flattened”. By manipu- lating the input signal with your PEQ you can cut a wide or narrow peak in response lo- cated somewhere in the frequency range of the equalizer. Importantly, the equalizer found your sub only allows reduction of peaks, and is “cut only”, not a boost device.
Measure the room’s response. As indicated above, you must have a firm under- standing of your room’s acoustical properties before you use a PEQ. To determine your room’s natural response properties (and your subwoofer, in that room) you will need an SPL meter shown on Page 6, and at least a pad of graph paper and a pencil for charting as below. If you have graphing program similar to Microsoft Excel ® this will save some time graphing the response curves. The last item to correctly measure the room’s response is a test disc that can play specific frequencies. The disc should contain frequencies from 20Hz to 100Hz. One of the most popular frequency tests discs is Autosound 2000 CD #101. It can be found at www.carsound.com/cds.shtml and is quite inexpensive.
Freq | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 75 | 80 | 85 | 90 | 95 | 100 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
SPL | 85 | 84 | 86 | 91.5 | 95 | 90 | 84 | 84 | 86 | 86 | 85 | 83.5 | 83 | 83.5 | 84.5 | 85 | 86 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Room A Re sponse |
|
|
96 |
|
|
|
|
93 |
|
|
|
|
90 |
|
|
|
|
87 |
|
|
|
|
84 |
|
|
|
|
81 |
|
|
|
|
20 | 40 | 60 | 80Figure 3 | 100 |
|
| Fr equency |
|
|
