Difference between Front and Rear Ported!

[PrOwLeR84]

Helo, I am trying ot figure out what the difference between a front ported and a rear ported cabinet are. Does it change the tone at all, or is it merely aesthetic?

[billfitzmaurice]

Originally Posted by PrOwLeR84

Helo, I am trying ot figure out what the difference between a front ported and a rear ported cabinet are. Does it change the tone at all, or is it merely aesthetic?

One has the port on the front, the other has it one the back. No change in tone. Do a search, this one gets beaten to death on a regular basis.

[gbarchus]

A rear ported cabinet can be affected by placement; near a wall or corner, for example.

Gale

[billfitzmaurice]

Originally Posted by gbarchus

A rear ported cabinet can be affected by placement; near a wall or corner, for example.

Gale

Radiation from a port is omni-directional, so front or rear it's equally affected by cab placement. The only exception is if a rear ported cab is pushed tight to a wall. Omni-directional port output is why a port can be placed anywhere except directly behind the cone, as that will allow midrange to go through the port and that can cause problems with reflected midrange off a rear wall.

[Bassamatic]

No difference, as the sound coming out is very low frequency and non-directional. I went over this in detail with my acoustical engineer.

[svtb15]

yeah its been said there is no difference... over and over ob TB.....I detect a big difference,, I prefer front ports....sure its non directional in theory.. but i dont know about anyone else but even if the cab is crossed over below 100hz i can tell where source is.. Its not that hard...

[SurferJoe46]

I always though that in the front you can at least 'feel' the sonic waves coming out the tube, reinforcing the front sound somewhat.

If you send it rearwards, then I think it might be lost in the wrong direction. No?

Maybe not?

[billfitzmaurice]

Originally Posted by svtb15

yeah its been said there is no difference... over and over ob TB.....I detect a big difference,, I prefer front ports....sure its non directional in theory.. but i dont know about anyone else but even if the cab is crossed over below 100hz i can tell where source is.. Its not that hard...

There's nothing theoretical about the omni-directional output of ports or the inability to directionally locate their output, which is centered around 50Hz with the average cab. When you can tell where the source is you're not hearing below 100Hz content, you're hearing the harmonics of that content. Were it not so there could be no such thing as subwoofer/satellite systems.

If you send it rearwards, then I think it might be lost in the wrong direction. No?

Look up the definition of 'omni-directional'. All output below roughly 200 Hz from the average cab is omni-directional, above that it goes directional, and the higher in frequency you go the narrower the dispersion. That's why you can stand behind your cab and hear the same thing below 200 Hz in back of it as in front of it, but you can't hear the mids behind it, and you can't hear the highs even when you're beside it.

[BassIan]

Originally Posted by svtb15

yeah its been said there is no difference... over and over ob TB.....I detect a big difference,, I prefer front ports....sure its non directional in theory.. but i dont know about anyone else but even if the cab is crossed over below 100hz i can tell where source is.. Its not that hard...

Were you testing the same cabinet (barring port location) in the same position in the same room in each case?

Detecting proximity can feel like detecting direction to a lot of people. You are locating the source because you can triangulate via proximity or are hearing artifacts from your subwoofer such as port chuffing or vibration. The woofer could also be producing higher-order harmonic distortion that you are detecting too.

Frequency-dependent directionality isn't "just a theory", rather a known fact.

[svtb15]

You guys nit pick too much about theory and not enough time playing your basses....

take any cab cross it over low.. if you cant hear where it is coming from in a no reflective room or outdoors , you may need to get your hearing double checked..
Too late to start wearing earplugs guys

[SurferJoe46]

Originally Posted by billfitzmaurice

Look up the definition of 'omni-directional'. All output below roughly 200 Hz from the average cab is omni-directional, above that it goes directional, and the higher in frequency you go the narrower the dispersion. That's why you can stand behind your cab and hear the same thing below 200 Hz in back of it as in front of it, but you can't hear the mids behind it, and you can't hear the highs even when you're beside it.

OK - suppose that the cab ports are so close to the rear wall that it gets a bounce-back of the vented (is 'frequency' a good word here?) - er, pressure waves and they collide with the outgoing waves.

A problem?

Do you have a rule of thumb for the distance away from a wall equaling 'X' times the diameter of the port?

You're the guy with the audio slide rule, so I look to you for information and guidance.

I know that if I put my cab in a corner, then it gets a lot 'boom-ier'.

[BassIan]

Originally Posted by svtb15

You guys nit pick too much about theory and not enough time playing your basses....

take any cab cross it over low.. if you cant hear where it is coming from in a no reflective room or outdoors , you may need to get your hearing double checked..
Too late to start wearing earplugs guys

Nobody is questioning whether you can locate the cab or not. So can I. However, you and I are not locating it because of what you hear at any frequency affected by porting. We are hearing other artifacts that *are* directional.

An understanding of the technical side of equipment makes it easier to enjoy music. Less time fumbling over why something doesn't work, more time playing. My job is engineering (nit-picking details), and it just happens to make the music side easier too.

[Zooberwerx]

If you're using a rear-ported cab and the cab has casters and you're playing high volume gigs, the enclosure will propel itself off the front of the stage...

...and I don't know what the heck I'm talking about!

Riis

[mulchor]

Think of the main acoustical cues for sound source direction. You have the spectrum (filtering of the outer ear), between ear level differences, and between ear time/phase differences.

In a long wavelength/low frequency sound source, there's hardly any of that info present. Of course a bass speaker doesn't only project low freq, but the port's design does.

[billfitzmaurice]

Originally Posted by SurferJoe46

OK - suppose that the cab ports are so close to the rear wall that it gets a bounce-back of the vented (is 'frequency' a good word here?) - er, pressure waves and they collide with the outgoing waves.

A problem?

No.

Do you have a rule of thumb for the distance away from a wall equaling 'X' times the diameter of the port?

No more than the port diameter is adequate.

I know that if I put my cab in a corner, then it gets a lot 'boom-ier'.

That's the result of boundary reinforcement in the midbass, and has nothing to do with port location, or for that matter whether the cab is ported at all.

[m_bisson]

Originally Posted by Zooberwerx

If you're using a rear-ported cab and the cab has casters and you're playing high volume gigs, the enclosure will propel itself off the front of the stage...

...and I don't know what the heck I'm talking about!

Riis

Lol I almost pissed myself!

Truth is, it doesn't matter for the low frequencies. If I go get my drumset and my my kick drum you can hear it anywhere in the house. Cymbals, snares, not so much.

Crank up my guitar and play it, then turn the bass to the same volume and the bass can be heard further away.

Woooooooo sound! You mystify me!

[silky smoove]

Originally Posted by svtb15

You guys nit pick too much about theory

Actually, you were nit picking what you consider a theory, whereas they were stating a fact.

[synaesthesia]

Originally Posted by billfitzmaurice

There's nothing theoretical about the omni-directional output of ports or the inability to directionally locate their output, which is centered around 50Hz with the average cab. When you can tell where the source is you're not hearing below 100Hz content, you're hearing the harmonics of that content. Were it not so there could be no such thing as subwoofer/satellite systems.
Look up the definition of 'omni-directional'. All output below roughly 200 Hz from the average cab is omni-directional, above that it goes directional, and the higher in frequency you go the narrower the dispersion. That's why you can stand behind your cab and hear the same thing below 200 Hz in back of it as in front of it, but you can't hear the mids behind it, and you can't hear the highs even when you're beside it.

You, sir, have the patience of a saint to keep dealing with these .....

[billfitzmaurice]

Originally Posted by synaesthesia

You, sir, have the patience of a saint .....

My wife would disagree.

[MrLenny1]

Speaker builders should think twice before putting ports on the rear of cabs.
Most of us weekend warriors are stuck up against a wall in a very small room.
2 of my cabs get left at home often because of this.
I played on a real size stage last week!!! Woohoo!