Page 16 | SV Sound |
|
|
Advanced Features: Room Compensation
Theory: In typical home theaters a phenomenon known as “room gain” can play a major role in affecting the sound of the subwoofer in any given home. If you desire, skip to “size” setting recommendations on the bottom of the next page. “Room Comp” control (short for “room compensation”), is there for some interesting techni- cal reasons, we need to discuss why this knob has been implemented.
In a typical home theater or music room, a subwoofer is sometimes called upon to produce frequencies lower than the lowest “mode” in that space. For example, if a room measures 21ft long by 16ft wide and 8ft high, the lowest mode will be about 27Hz. To calculate the lowest room mode use the following equation. Note: 565ft (or 170 meters) in the formula is a “constant” representing the speed of sound.
Lowest Mode = 565
Lowest Mode = 170
÷Longest Dimension (feet)
÷Longest Dimension (meters)
When the subwoofer produces any sound below 27Hz, the output is different than its “anechoic”* output. The difference is depicted in the graph below. The red trace indicates the anechoic response and the blue trace indicates the same subwoofer’s response in a 2800ft3 room. As you can see the output increases as the frequency decreases when compared to the anechoic response.
|
| d B SPL |
| SP L vs F req |
|
|
|
|
|
| ||
| 1 1 5 |
|
|
|
|
|
|
|
|
| ||
| 1 1 0 |
|
|
|
|
|
|
|
|
|
|
|
| 1 0 5 |
|
|
|
|
|
|
|
|
|
|
|
| 1 0 0 |
|
|
|
|
|
|
|
|
|
|
|
| 9 5 |
|
|
|
|
|
|
|
|
|
|
|
| 9 0 |
|
|
|
|
|
|
|
|
|
|
|
| 8 5 |
|
|
|
|
|
|
|
|
|
|
|
| 8 0 |
|
|
|
|
|
|
|
|
|
|
|
| 7 5 |
|
|
|
|
|
|
|
|
|
|
|
| 7 0 |
|
|
|
|
|
|
|
|
|
|
|
| 6 5 |
|
|
|
|
|
|
|
|
|
|
|
| 6 0 |
|
|
|
|
|
|
|
|
|
|
|
| 5 5 | 1 0 H z | 2 0 | 3 0 | 4 0 | 5 0 | 6 0 | 7 0 | 8 0 | 9 0 | 1 0 0 | |
|
| |||||||||||
|
|
| 6 : An e c h o ic |
|
|
|
|
|
|
|
|
|
|
|
| 7 : 2 8 0 0 ft^3 |
|
|
|
|
|
|
|
|
|
Map |
|
|
|
|
|
|
|
|
|
|
|
|
Notes |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| E n c lo s u re | P e rs o n : J im F a rin a |
| P ro je c t: R o o m C o m p e n s a tio n | J u l 1 8 , 2 006 |
|
|
| ||
5.2.0.350 | Ju l/15/2005 | S h o p | C o m p an y : S V S o u n d , L L C |
| F ile : R o o m C o m p en s a tio n .le d | T u e | 4: 4 2 p m |
|
|
| ||
*Anechoic: Meaning essentially, “without echo”. As measured in a special room, or outdoors, without the reflective boundaries that any audio enthusiasts’ home present to a speaker or subwoofer.
This resultant “in room” frequency response will