Subwoofer Ports???

Mr. Mojo

Does bass actually come out of a subwoofer port or is it just to allow air to exit?
I'm talking about a front facing sub with a port in the back.
I'm asking as it could impact where I place it.
Thanks for any input.

treitz3

All subs will be greatly influenced by location. Not sure if I can truthfully tell what the function of the port is without blowing smoke up your arse, so I'll let someone who is more qualified answer that one a little more precise than I can. You do want to make sure that the port can breathe though.

jacob.simpson

http://www.polkaudio.com/downloads/12vhndbk.pdf
THINK THIS COVERS MOST OF THE COMMON QUESTIONS RELATED TO SPEAKERS AS WELL AS CAR AUDIO.;)

Systems

Mr. Mojo wrote: »

Does bass actually come out of a subwoofer port or is it just to allow air to exit?
I'm talking about a front facing sub with a port in the back.
I'm asking as it could impact where I place it.
Thanks for any input.

Think of a port as a piston of air that operates over a very limited range of low bass frequencies.You should not place the port up against a wall,but give it several inches of space.

TheMARPATNinja7

If you put your ear in the port and listen you'll hear bass but that is not nessicarily where the sound is produced, if bass was intended to come out of the port, sealed enclosures wouldn't make any noise. The driver is responsible for pounding the sound out.

comfortablycurt

Bass ports essentially help to increase low end extension through air being forced through them. Ports are more than just a tube stuck into the cabinet, they're tuned to reproduce different frequencies through different lengths and widths. They aren't actually "producing" any bass by themselves, but they are helping to solidify that bass. That's why ported subs are preferred when huge low end and overall volume are more desirable than SQ.

Sealed subs tend to be a lot more accurate and are typically preferred for music listening, where as ported subs tend to be preferable for HT applications. Not to say that one won't work for the other though.

As long as the sub isn't directly against a wall you should be alright. I'd try to keep it at least 7-8 inches off of the back wall. just play around with the placement and see what sounds best. Placement is everything with speakers. Moving a speaker as little as an inch forward or back can dramatically change your sound.

Systems

TheMARPATNinja7 wrote: »

if bass was intended to come out of the port, sealed enclosures wouldn't make any noise.

Actually the port does reproduce bass but over a limited bandwidth.It is tuned to a specific low frequency to augment the bass below the woofers operating range, therefore extending the bass response of the system.The small column of air in the port operates like a piston and is driven by the backwave of the woofer.

ShinAce

A port makes use of the energy coming off the backside of the speaker cone. A sealed box does not.

As weird as it is, a port is actually a filter. Ironically, it allows high frequencies through and shunts lower frequencies. It is a high pass filter. Tune it low enough(like 30 Hz), and it'll kill anything below 30 Hz from being played well. At 30 Hz, the speaker will barely move and most of the sound is from the port. As you move higher in frequency, the sound shifts from the port to the woofer. By about 45 Hz, you can figure that all sound is coming from the woofer.

So it uses energy that's normally lost to add more sound. The trade-off is that if you play too much music around the port frequency, the speaker will overheat(remember, it's barely moving but taking full power). Below the port frequency, the speaker will flop around like it wasn't even in a box at all.

Rule of thumb is a minimum of 3" from the port to any surface.

Mike21

You might try this experiment after locating the sub where you like the sound best. Stuff some socks into the port and see how it sounds.

gsquared

hate to hijack the thread, but will obscuring a downfiring sub port with furniture/placement negatively affect sound output. also, what is "chuffing"?

ShinAce

Chuffing is when the sub is pounding hard and too much air is moving through the port. It sounds like a low-pitched whistling when the bass hits.