Sealed vs Ported Subwoofers

Subwoofers are very commonly used with electronic equalization. The inherently-smooth slow rolloff of a sealed system is best suited to equalization, and the equalization can take care of the fact that the rolloff begins at a higher frequency.

There is no better..... but You can certainly prefer one over the other and there are implications of one being better over an extended period of time.
If a ported driver is ported correctly, it will be acoustically flat. If a sealed driver is in the correct encloser and you achieve a final QTS @ .707, you have an acoustically flat sealed driver. The big difference is that it is typically easier to find a driver that will achieve a very low frequency from a ported design and when the driver is at its minimum frequency a ported sub will then roll off @ 24 db per octave, so below its rolloff there is very little output. In a sealed design, once a driver hits its low frequency rolloff, it rolls @ 6db per octave, so you will still have very useable low end frequency below the point where it begins to roll. Because of this, the two do sound a little different from one to the other. Also, I had said that over time the implications are that one is better. That is because as a driver wears, its specs change, especially its qms... as the specs change a ported design has a tougher time maintaining its accuracy, where a sealed woofer will stay fairly true... Of course, that does take a fair amount of wear. As alluded to above by another... Any woofer in its perfect sealed box, will always need a larger encloser for its perfect ported box, But there are very few woofers (very few, not zero) that truly are versitile enough to use ported or sealed. I hope this helps, Tim

Timlub,

Very well said. Your reply zeroes in to the fact that cost is a major factor in loudspeaker design. While Wilson uses a ported design in it's flagship speaker it delivers sound that would take a much larger design, requiring a much larger room. If you have no constraints on the size of you room or budget you can always improve on commercially designed speakers.

Ported designs are a natural compromise that is utilized in many designs because of efficiency, both in size and cost.

Designing and building a loudspeaker that prevents the front wave and back wave of a driver from meeting is easy. Choosing drivers that crave that alignment is expensive. Doing it so that it sounds better than anything else is priceless! I couldn't resist saying that!!!

Ken

A ported enclosure can be 3dB more efficient at the same size or play a quarter octave lower at the same efficiency.

The same driver excursion will net you perhaps an extra 1/3 octave of extension with a ported speaker.

You'll have higher excursion limited output in the bottom of a ported design's pass-band so you can use smaller + less expensive drivers.

Distortion will also be lower in the bottom of the speaker's pass-band with the port because of the reduced excursion.

Ported enclosure+driver combinations have four poles in their high-pass function for an eventual 24dB/octave roll-off function while sealed ones have just two for 12dB/octave. With sufficiently shallow roll-off room gain (12dB/octave in an infinitely rigid room below its fundamental resonance at 1130 / 2 / the longest dimension) can keep the speaker flat below its roll-off.

Ported enclosures do not load the driver once you get below the port tune, with excursion increasing to what it would be in free air. Where too much low frequency energy is present below the speaker's pass-band you'll have distortion (including midrange IM distortion on 2-way speakers) and may even run the drivers into their mechanical limits resulting in damage (some very nice drivers will bottom the voice coils on the back plate). For a given input level sealed speaker excursion remains constant with decreasing frequency.