What is the difference between front, bottom and rear firing ports on subwoofers?

Jeff Adams

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I have been doing a ton of research on subs as I am getting ready to purchase one or two of them. One thing that I was wondering about is the ports on subs and if it is something that I need to be concerned about. I am going to be placing my subs in the front right/left corners of my room.
 

Robert_J

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If one port location was best, then every manufacturer would port their subs the same way.

-Robert
 

Jeff Adams

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So then what is the difference? What does a porting a sub in the front have over porting them in the rear? Do they sound different?
 

Jeff Gatie

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Aesthetics, design, space and size considerations. along with manufacturer preference. There are many more important differences between subs, besides where they are ported, starting with performance. I would not use this as a deal breaker or maker on any sub I bought.
 

RichardH

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The only consideration I can think of is if you can't give a sub's ports enough clearance from the wall. e.g. if you have a sub with rear firing ports and you have to put it 2 inches from the wall, you may want to consider a front or downfiring sub.
 

Jeff Adams

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Richard,
Your response makes a lot of sense but now I question why they put them on the bottom then. There is not a lot of clearance in between the floor and port for floor firing ports.
 

Paul_Dunlop

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My limited experience

I had a rear firing sub in a condo - was below the left surround, back wall
Port fired towards my neighbours bedroom - he didn't like it

I changed to a front firing, same location and everything is good

I will be using the front firing sub in a new location, at my new place - probably beside 1 of the front speakers, or midwall on the left side. We'll see how that works out

Downfiring might work better with hardwood, but I think it would be muffled by carpet

Some of it may be esthetics - rear firing allows a clean front end to it - nothing for people to see or stuff something into

My 0.02
 

ScottCHI

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Even though you may read that sound, theoretically, shouldn't come from the port of properly designed ported sub, I've never heard a ported sub that didn't have sound (not chuffing, actual sound) emanating from it's port.

So, given that, you can see how the location of the port could make a difference in how a sub "sounds".

Ports are probably located on the bottom to minimize this contribution of the port to the overall sound of the subwoofer.

Ideally, of course, a port shouldn't produce any sound, BTW.
 

andySu

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Jeff

I would appear you need to have faith in the sub basses ability, personally I’d go for an 18” JBL professional sub bass 4645 4645-B 4645-C they kick slam drop down to abyssal depths of unrelenting pressures and are THX certified, look no further, I use the JBL 4645, and the newest film that I played last night on region 2 DVD Poseidon, WOW that “Rouge Wave” sounded very deep VERY!!!!
 

ScottCHI

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Did you even read what you linked to?

The purpose of a port is NOT "to produce sound to augment the output of the driver"! That's completely wrong.
 

Jack Gilvey

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I'm rather familiar with reflex theory, yes.


Do you really believe that no sound is produced by a port? What do you believe a port does?
 

ScottCHI

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OK, I'm not being clear. And perhaps I'm a little bit wrong.

The port IS tuned to resonate at a particular frequency in (sort of) the same way that a bottle can produce a tone when you blow over it's opening.

What I am addressing, though, is the fact that many people think that a port is supposed to produce sound that comes from the back of the driver, that comes out from inside the enclosure. A properly designed port/enclosure will not do this.

But many subwoofers (and speakers) DO produce sound from the port that is well above the tuning frequency of the port, and this is not correct. Sound from the back of the driver shouldn't come out of the port. The location of the port (relative to the listening position) can diminish this undesirable artifact.
 

Jack Gilvey

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Agreed. Any internal noises, or airspeed-induced port chuffing, can be diminished with positioning.
 

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