Port Noise?

[L.J.]

Curious about this?

I'm wondering what is port noise, what causes it?

[Resident Loser]

...air...

jimHJJ(...in ported speakers that is...)

[L.J.]

...air...

jimHJJ(...in ported speakers that is...)

Can you explain what does this have to do with a rear ported speaker being too close to a back wall?

What sound should one listen for? Is it so obvious that you know there's a problem?

Thanks in advance

[topspeed]

Speakers that have rear firing ports that are placed either too close to the wall or within a small space such as a bookcase can produce port noise, or "chuffing." This usually happens at high SPL's when there is a lot of air moving through the port and hitting the wall and yes, you can hear it. You can address this by putting a bung into the, well...hole...or by moving your speaker. B&W supplies foam cylindrical bungs with their speakers and Smokey tried using his socks at one time, but the speakers started to smell up the house . Be aware, this does change the character of the speaker, in particular low freq. response.

Hope this helps.

[L.J.]

Speakers that have rear firing ports that are placed either too close to the wall or within a small space such as a bookcase can produce port noise, or "chuffing." This usually happens at high SPL's when there is a lot of air moving through the port and hitting the wall and yes, you can hear it. You can address this by putting a bung into the, well...hole...or by moving your speaker. B&W supplies foam cylindrical bungs with their speakers and Smokey tried using his socks at one time, but the speakers started to smell up the house . Be aware, this does change the character of the speaker, in particular low freq. response.

Hope this helps.

Thanks Topspeed. This may be a little off subject, but what's the purpose of putting acoustic paneling behind your speakers? Is this to reduce port noise or is that a totally different subject?

[topspeed]

I suppose you could use it for that, but most use it to absorb unwanted reflections from the speakers. Sound radiates in a 360 pattern and when it hits walls, it bounces back thereby cancelling/reinforcing other waves. On the topic of room acoustics, I know just enough to be dangerous. The guys you want to talk to are Wooch, Sir TT, and Richard Greene (who doesn't post much anymore, but do a search on his name and you'll find he's the Zen Master).

[jocko_nc]

I would consider "port noise" to be noise generated within the port itself, noise that would be present regardless of walls or the location of the speaker. You certainly might be more inclined to hear it in a certain position.

I suppose it's a matter of fluid dynamics, the nature of the airflow through the restriction in the cabinet which is the port. Air velocities and features that would contribute to disturbances. Putting a properly-sized port against a wall would increase air velocity and could create a disturbances.

On my DIY projects I ran into some port noise issues. I initially tried a homemade "diffuser" in my port tube, an attempt to dampen the bass enhancement in expectation of a dual-sub satellite setup. All I did was reduce the cross section area and create noticeable chuffing. When I did the subs, I went for the tapered Precision Port. It has a parabolic taper on either end, with a MAX of double the port diameter. I think that design feature is hugely valuable as it allows for smooth acceleration of the air. As damped as my subs are, the airflow is quite violent. Having the port designed for smooth airflow has got to help.

jocko

[FLZapped]

Curious about this?

I'm wondering what is port noise, what causes it?

Poorly designed speakers.

If the designers make the port too small, then the velociy of air trying to move through the port will become audible.

[L.J.]

Thanks for the response guys.

Topspeed, I'm such a dork. I asked that question about the paneling behind the speakers in another thread months ago and simply forgot about it. Woochifer pretty much gave the same answer you did, in that thread. All those parties finally catching up to me.

[GMichael]

Thanks for the response guys.

Topspeed, I'm such a dork. I asked that question about the paneling behind the speakers in another thread months ago and simply forgot about it. Woochifer pretty much gave the same answer you did, in that thread. All those parties finally catching up to me.

Have another cookie.

[kexodusc]

Yep, port noise is caused when the velocity of air inside the port is too fast, becoming audible...I've heard it sound very different from one speaker to the next...don't know why that is, maybe a big difference in the air flow?

[GMichael]

Curious about this?

I'm wondering what is port noise, what causes it?

When you are on a large ship, this is the noise coming from the left.

[L.J.]

Man I think I had one cookie tooooo many. My short term memory is shot. All those all nighters are finally catching up.

Hey kids ever see this commercial: This is your brain, this is your brain on ..................

[GMichael]

Man I think I had one cookie tooooo many. My short term memory is shot. All those all nighters are finally catching up.

Hey kids ever see this commercial: This is your brain, this is your brain on ..................

And this is your brain on HT.

[hermanv]

Thanks Topspeed. This may be a little off subject, but what's the purpose of putting acoustic paneling behind your speakers? Is this to reduce port noise or is that a totally different subject?

Some speakers (almost all electrostatics for example) radiate out both front and back, they are called dipoles or bipoles (bipoles are in phase, dipoles are reversed). In a large room with the speakers well away from the wall this usually sounds better than a typical front only speaker. In a smaller room the speakers end up too close to the back wall and an absorbant panel does wonders.

See for example:
http://www.soundlab-speakers.com/accessories.htm

At bass frequencies (longer wavelength than the cabinet size) all speakers radiate more or less at 360 degrees.