Originally posted by e24_635csi
why is it that they sound better facing the other way?
It's difficult to explain this without drawing you some pictures. In short, facing the sub's so they fire into the trunk gives you a LOUDER bass. facing them into the cabin, you get a crisper bass. In the end, it depends on your preference. Most people try placing their box in both directions and easily notice that the bass is much louder when it fires into the trunk. (their chest rattles more... you can feel/hear the bass from further away from the vehicle).. however you loose some of the frequency response of the music you're listening to. (which you'd notice a lot more in classical, jazz, or acoustic music... compared to most mainstream pop---where a lot of the time distorted bass frequencies are already establised at the time the song is recorded.)
A lot of what you hear, and what you feel depends on speaker placement... a lot of factors take place, such at atmosphere, wavelength, audio cancellation, etc.
A lot goes on in our mind when processing sound. Since our directional hearing and most sensitive detection occur between 400Hz to about 5kHz, (20Hz-20KHz audible detection) the speakers that produce those frequencies are most important with placement. In fact, most high-end components have only one driver producing those frequencies--one speaker = seamless sound. Keep in mind that at lower volumes we are less sensitive to frequencies above & below that rangeómaking it increasingly hard to satisfy our listener.
Bass, is not that picky. We can place the speakers in front of us, behind us, on top or below. I'd shy away from above & below because in a car, cancellation would be high.
Since 99.9% of all subwoofers are placed behind the vehicle operator & his/her passengers, let's assume we're all going to put woofers in the trunk or extended cab section.
Bass is like a whip. The closer you get your head to the tip, the harder it's going to hit you. Get too close to the whip, and it'll wrap around you and not hurt at all. This is true in direct proportion to the frequency.
Deeper bass has longer wavelengths. Since sound travels at 643m/s or 1125ft/s in a standard atmosphere, we divide one of the above by the frequency to get the wavelength. Standard atmosphere 20C, 1013mb pressure, 50% relative humidity. A 50Hz wave has a wavelength of 22.5 feet while a 100Hz wave is 11.25 feet.
In order to get the maximum of 50Hz you'd need to get that woofer 22.5 feet away from your head, while 100Hz, only 11.25 feet. This is why we 'hear' the 100Hz sound more prevalently when facing the woofer box towards the vehicle operator when the box is in the trunk. When we face the woofer box towards the trunk, we get the benefit of 3 feet each way via reflection of sound waves.
Since the 50Hz wave gets more time to approach maximum, it appears louder facing backwards than when facing the frontward. Add this with the cabin gain @ 50Hz, and it would appear to be substantially louder. The 100Hz wave is really not affected so dramatically. In fact, there might be some loss in longer vehicles (SUVs Vans, etc) since the wave may be past the 11.25 foot mark, and weakening.
In most cases, placing the woofer box to face the rear of the vehicle will improve frequency response below 60Hz compared to facing it frontward. As long as you have signal processing (EQ or head unit with bass controls) you can compensate for acoustic loss/gain. In most cases, cutting the strongest frequencies (usually 45Hz-55Hz) will balance out the freq resp and at the same time avoid additional distortion caused by over-boosting signal.
Hope that helps some.