Sealed vs. Ported Speakers

I read an article a few years back that said ported speakers have more bass output but roll off quickly where a sealed enclosure goes down a bit lower (with a smoother rolloff) but has a bit less output.

Based on this information I wonder why more companies do not make sealed enclosure speakers (even if they are a bit less efficient) as it seems sealed enclosures would work in more rooms as well.

One other wrinkle:

There are variations on sealed boxes. Those designs which limit internal cabinet volume relative to maximum driver displacement (usually called "acoustic suspension" speakers) damp the driver's movement to a greater degree than those which use a larger volume box relative to max driver displacement (generally "infinite baffle" speakers).

Caveat: As far as I can tell, these terms are used somewhat imprecisely in audio writing, so you've got to be careful about written descriptions. The less damped infinite baffle designs generally sit somewhere between ported designs and acoustic suspension designs in regard to tight bass, but...

Not all ported designs are created equal, either. Some (Merlin and Ref 3a come to mind) sound (to my ear, anyway) like they're more highly damped than others. That makes it even harder to compare/contrast the two approaches.

In the end, I believe that generalizations are often of limited utility when trying to pin specific qualities back to broad design criteria like "ported" vs. "sealed" speakers.

Marty

Not many sealed (acoustic suspension) speakers around nowadays. Maybe because manufacturers want specs to sell, maybe because there's a limited amount of drivers available and suitable for sealed enclosures (higher Q drivers relying on the lower Q of the cabinet). Examples of older speakers that were sealed were Dunlavy, Hales and Infinity/Genesis (except for the dipoles). Looking at those names, you might say it's a failed business approach but that's not the why. NHT is still committed to that design.

Every now and then, I still run across an opinion, even one as experienced and respected as Siegfried Linkwitz, that's derogatory to anything other than dipole or sealed, espescially for subwoofers. Everyone is entitled to an opinion, even husbands on occasion. Some have reasons.

Myself, having just built a pair of DIY speakers, chose sealed because of the transient response, being able to fit twice the number of drivers in the same cabinet volume and some forgiveness in the design. Sure, it gives up some deep bass extension but that's what subwoofers are for. Historically, quickly becoming ancient history, I've generally preferred sealed. Still say quality over quantity but not so arrogant to say they're mutually exclusive. There's always a compromise.

For example, let's say the next project is a sub or two. If I want "fast", I could choose a smaller, lighter 10" but in a sealed box that might have an F3 (-3dB) of 40Hz (hardly my idea of a sub). With a port, transmission line or passive radiator, the same driver can be tuned down to the 20's. Or, you start getting bigger, dropping efficiency, adding servo feedback...

Typical snides about ports include "chuffing", time and phase distortions and "wicked, nasty" driver excursion. Even an old fart has to concede something to modern manufacturing techniques, relatively accurate Thiele/Small parameters and the progress of science, albeit sideways, other ways and otherwise.

Sealed enclosures used to dominate high end speakers; ported speakers were often dismissed as "frat boy" speakers. However, over time things reversed.

Sealed enclosures may roll off at a gentler 6 dB/octave, but they start rolling off at a higher frequency than a properly tuned ported speaker of similar size. For a small tower, a sealed enclosure starts rolling off at 100 Hz. A ported one is more likely to be flat to 45-50 Hz, which translates into a *much* more realistic tonal balance as it's linear down to the bottom fundamental of a kick drum or bass guitar.

I had a pair of ADS L1090's, a small tower with twin 7-1/2" woofers in a sealed enclosure. For being about 40" tall with twin woofers and as much as it cost me, it sure didn't have much bass. I replaced the L1090's with a pair of Mirage M5si's with dual 6-1/2" woofers and two large diameter ports. It was linear to the mid-30s with clearly audible bass down to the mid-20's. There was no "one not bass," no boominess. Bass is clean, tight, and full.

I also have a pair of petite Mirage floorstanders, the OMD-15. It doesn't have the bass output of the M5si, but it still smokes the L1090 in tonal balance and bass extension. And ports and all, it gives up nothing to the ADS in bass tightness and clarity.

Another cool thing about ported speakers is that you have more ways to match the speaker to the room. Wilson's new Alexandria XLF is made so you can direct the port to the front or the rear. Monitor Audio and PSB both offer several twin-ported models with foam plugs so you can damp the bass alignment four different ways. I used to view ported speakers with disdain, but not anymore. Once designers figured out how to get the bass extension while damping the resonant frequency, you got more and better bass in a smaller enclosure for less money.

Magicos seem to be the primary example of modern sealed design, but they're so expensive they sort of have their own little world most mortals can't enter. Also, some designs have a port with a passive speaker plugging it up to aid in efficiency and halt the dreaded "port chuff" that I personally haven't ever noticed, but then I don't stick my head near the port very often (unless, unfortunately, I've passed out on the floor behind my speakers). I think of transmission line speakers are a good idea in the "ported" camp and wonder why there's not more of that sort of thing.