Axiom Home Page Forums General Discussion Stereo Alan, Why vented enclosures?

Alan,

Why, in your opinion, have vented enclosures become so popular in speaker design? I've always preferred the sound of sealed enclosures as they eliminate the hump in the mid bass (and the vocal region) that seems to plague ported designs. Other than M&K and some NHT models, very few speakers are designed as sealed anymore.

I've found that plugging the port gets me the performance I'm looking for but I'm still curious as to your (and others) opinion on this subject.

Thanks,
George

i would guess that it's because ported speakers offer advantages in volume, frequency extension, and efficiency. the nature of acoustic suspension designs makes them considerably less efficient than ported designs. true, acoustic suspension allows for greater control over driver movement than ported designs, but there are other ways to get quick, accurate responses from the drivers. maybe using lighter more rigid materials or larger magnets? that way, you'll have the benefits of both accuracy along with an extended frequency extension and speaker efficiency.

i don't know. just a guess? i'm interested in finding out myself. good question.

The following link has some good information:
http://www.audioholics.com/speakbasic.htm

For those more technical, here is an indepth link:
http://xsspl.tripod.com/Audio/Sound.htm

Regards,

BBIBH

The vented enclosure allows making use of the energy from inside the cabinet that would otherwise be lost in a sealed enclosure. As to how this energy is used is up to the designer of the speaker. In the Axiom designs this energy is tuned to add lower frequencies to the amplitude response that would not exist without the vent, this extends the range of the speaker while remaining true to the principle of linear amplitude response. Many speakers are designed to use the vent to add energy at slightly higher frequencies thusly giving a boost to the upper bass region. This trick can be quite impressive on an initial and quick listen but usually becomes quite fatiguing over time. A fast indicator to this type of tuning is a relatively short, large diameter port, which will raise the tuning frequency and create the bass hump.

Ian Colquhoun
President & Chief Engineer

Ian has nicely nailed the logic behind ported designs, and you're also right, anonymous, on the efficiency question. However, a sealed-box design can produce very deep, extended bass--but you have to have lots of power to drive it. I'm using a sealed-box subwoofer in my car that produces output to 20 Hz, but it has a dedicated 180-watt RMS power amp driving only the sub. It's been said that when I play pipe-organ CDs on this system while driving at night, the headlights dim on the organ pedal notes!


Alan Lofft
Axiom Resident Expert