subs facing?, does it matter? Options

[lake1069]

i have 2 12" 700watt subs in my hatch, i've been messing with the levels to get it to sound just like i like them, but i'm wondering if it makes any differece which way the subs face, like toward the driver or opposite?

[Silvan]

It shouldn't really matter what side they are facing. That part has to do with the human ear; the human ear isn't capable to detect where sounds below 80Hz (I believe) are coming from. Think of the subwoofer of the surround-set. You can virtually place it anywhere.

As for the part of subwoofers not doing there job; This all depents on the construction of the enclosure; is it designed to meet the specs of the sub? What about crossovers; maybe set to a too high frequency or a too high db-cut off ?

[Abraxis64]

It shouldn't really matter what side they are facing. That part has to do with the human ear; the human ear isn't capable to detect where sounds below 80Hz (I believe) are coming from. Think of the subwoofer of the surround-set. You can virtually place it anywhere.

while you are correct in your assertion that sounds below a certain frequency are omnidirectional (you can't tell which direction they're coming from), that doesn't mean that the sound waves don't exist--in fact these sound waves function like any other wave and they tend to bounce off of stuff. sometimes, when they bounce off stuff, their strength is amplified.

take your home theater example--sure, if you wanted you could stick your sub in the middle of the living room...but if you stick it against a wall, it appears to sound louder...stick it in a corner, and it's louder still. you won't be able to localize the sound (if your sub is playing nothing but sub-bass, anyway), but you will be able to discern a noticeable volume difference.


afroman, as far as his subs, i don't recall the w3005 ever being produced in a dual-coil configuration. it is possible, however, that they are single 8-ohm each? hopefully the shop told him
peace

[Silvan]

It shouldn't really matter what side they are facing. That part has to do with the human ear; the human ear isn't capable to detect where sounds below 80Hz (I believe) are coming from. Think of the subwoofer of the surround-set. You can virtually place it anywhere.

while you are correct in your assertion that sounds below a certain frequency are omnidirectional (you can't tell which direction they're coming from), that doesn't mean that the sound waves don't exist--in fact these sound waves function like any other wave and they tend to bounce off of stuff. sometimes, when they bounce off stuff, their strength is amplified.

take your home theater example--sure, if you wanted you could stick your sub in the middle of the living room...but if you stick it against a wall, it appears to sound louder...stick it in a corner, and it's louder still. you won't be able to localize the sound (if your sub is playing nothing but sub-bass, anyway), but you will be able to discern a noticeable volume difference.

[right][snapback]331709[/snapback][/right]

All that you are saying is true, but then again also not entirely. (dont feel offended )
Subwoofers are really a tricky thing. Because subs play in the lowest regions of soundfrequency, what you really measure is the response of the environment it is in.
The reason that you have for example 90db@20Hz. has more to do with the fact that you find yourself in a spot where you have maximum bassreponse at that specific frequency. (anti-node)

As an experiment try this: place your sub in a room and let it play a constant tone of 40Hz. Walk around with a db-meter and mark all the spots where you have good reponse, walls for example (anti-nodes). Mark also places where you have nearly zero response (nodes). Now try the same with a 50Hz tone. You will notice that all the spots you've marked before are all mixed up. This is because all tones travel with exact the same speed. But the wavelength is different which causes that a full low frequency sinus does not "fit" in the room. Also if letting sound reflect from a surface isn't a clean solution. The reflected sound travels delayed. If you make this visible with a spectrum analyzer you should see several sinus curves, crossing eachother. This will result in amplification at some points(spike, anti-node) but also at some points they will cancel eachother (node).
Also, the reflected sound will travel to your ear with delay, causing a rumbly and distorted bass.
This proves that placing a woofer doesn't work by the priciple that if it reflects its sound, there is more sound pressure level at every frequency, thus making it very difficult finding a sub that meets your needs for a specific room without tuning it.

If the woofers are suited for it you could go ported. While there are some benefits there, like 3-4 db more pressure, be carefull not to make design flaws, you could easily blow your subs.
A rule of thumb that can be used is; EBP produkt (Efficiency Bandwith Product):EBP = Fs / Qes
If EBP > 60, and QTS = 0,5 : Free air
If EBP = below 100 and QTS equals 0: Closed enclosure.
If EBP = between 50-100 and QTS equals 0: Ported.