Front vs. Rear Port


Seems like the majority of speakers have rear ports, but a significant minority has front ports. What are pros and cons? Are font ports preferable when the speaker needs to be close to the wall?
raduray
Front Ports generally work better when a speaker is close to the wall. There are some exceptions.
I went from front to rear port in one of my designs.

It's not at all uncommon for some midrange energy to emerge from the port. If the woofer is active up to frequencies where the port is 1/4 wavelength long, you stand a good chance of getting midrange port resonances (imagine talking through a cardboard tube). If that happens, better to aim it backwards than forwards.

As you correctly suspect, proximity to room boundaries will reinforce a rear-firing port's output. This is usually detrimental, and can be a cause of "boominess". On the other hand if the enclosure were tuned with the expectation of boundary reinforcement of the port's output, the net result would likely be deeper than normal bass extension. Audio Note uses this technique with their rear-ported AN/E, which is intended to be placed in a corner. I borrowed the idea and incorporate a variable-length port system in my rear ported designs.

Now if a rear-facing port is close enough to the back wall, the wall will increase the effective port length enough to change the box tuning. This may or may not be beneficial in a given situation. Keeping the port two or more port diameters distance away from the wall reduces this effect to negligible (which again may or may not be beneficial).

As long as the path length around the box from the rear-facing port to the front-firing woofer is less than 1/4 wavelength at the port's tuning frequency, there should be negligible loss of bass impact from the path length difference. In fact, placing the port in a different plane from the woofer would help to spread out their room interaction effects by giving them different path lengths to the room boundaries. In theory this would smooth the bass a little bit.

All that being said, port location is probably unlikely to be a major factor in the overall sound quality of a loudspeaker system.

Duke
Raduray: Yes, conventional wisdom says to use front porting if the speaker is placed close to the back wall.

Duke: Please forgive my ignirance but when you speak of your designs, are these commercially marketed models? What name do they go by?
I port out the bottom or back of cabinet I tried front ports not my cup of tea,best is bottom porting [this is harder and more costly to pull off]next back.Only front ports I now use are slot ports for bass systems only[oris ref]If my customers would let me back port these cabinets I would but they like the look;).
Aktchi, I showed two speakers of my own design at the Rocky Mountain Audio Fest in Denver a few weeks ago, using "AudioKinesis" as my brand name. I don't sell through a dealer network - just peddle 'em myself.

Don't want to hi-jack Raduray's thread, so will just mention that you can read about 'em on my website, www.audiokinesis.com.

Johnk, I also like down-firing ports, though at the moment I'm not using a down-firing port in any of my designs. But I'll concede that down-firing is probably the ideal. Do you find that the floor surface underneath a down-firing port is a significant consideration? I mean, like whether it's a hard surface or carpeted?

Cheers,

Duke