Lightweight-USPowah

what does porting an enclosure do to the sound/tone of the bass?

Jarrod

In general your sound quality is diminished somewhat and your output is increased. I don't know how detailed you want but . . .

Ported enclosures are tuned to a specific frequency, anything below that frequency will have very little to no ouput from the speaker, and trying to play a speaker below that frequency can severly damage it. That's what subsonic (infrasonic) filters are for.

The lower the tuning frequency the better the SQ, in general. But the higher the tuning freq. the greater the SPL.

A sealed box will give you better low end (to the extent of which the driver can play) and better (cleaner, crisper, less muddy) sound.

Bandpass has a VERY steep roll-off and you lose a lot of output under a certain freq. But they get REALLY loud, just also really muddy at the same time. There is such a thing as a good bandpass box, but they are difficult to build.

Also, ported boxes can sound really good, if done correctly. I probably gave you more info than you wanted to know, or not enough, or info you already knew, but I felt like typing I guess. :-D

Lightweight-USPowah

The box is currently sealed so I think I will just leave it like that.. I don't care how loud it is, I just want clean, crisp bass..

Jarrod

Glad I could help.

Neon01

<center><img src="http://filebox.vt.edu/users/chcampbe/Brahma12Tempest.JPG"></center><p>"A sealed box will give you better low end (to the extent of which the driver can play) and better (cleaner, crisper, less muddy) sound."

The first point here isn't *exactly* true. The virtue of a ported enclosure is typically that it can produce sound (at reasonable volume) at much lower frequencies. Below I've attached a graph from my analysis of enclosures for my Brahma. This plot shows frequency reponse. I was selecting whether or not to use ported or sealed. The yellow line indicates the sealed enclosure of .93 cubic feet (Qtc of .707 or 'optimum'), and the green the ported box, tuned to 30hz, with a net volume of 2 cubic feet. Disgregard the purple and brown lines, they were for another project. What's important to note here is that the sealed box rolls off slowly, but begins very high (around 50hz). The ported enclosure will gain you a nice little rise in dB right around your tuning freq (at shown right around 30hz), and then drop STEEPLY, like Jarrod said. But notice that until that point, the ported enclosure is still well within it's +-3dB band, all the way to about 28hz. The -3dB point on the sealed is at about 44hz. Big difference.

I do agree with everything else Jarrod said however. Sealed boxes can certainly take much more power down low, and can sometimes react well with a Linkwitz transform to shape the freq response more like a ported enclosure. But you need tons of power, and a damn good EQ to do this.

Jarrod

that it can play lower. Not better at low frequencies. ie. An Infinity Perfect can play a 18Hz tone although it won't be loud (or even audible) in a sealed box. But that same sub in a ported box tuned to 28Hz is gonna have a serious problem with that 18Hz tone.

Jarrod

oh yeah, and you are absolutely correct. :-)

Neon01

Ahh, gotcha. Very true