in ,

KIH #34 – Any port in a storm

  • One man’s ‘Ode to Joy’ by Louis van Beethoven becomes another’s ‘Node to Oi’ by Lewis von Beathaufen. He uses ‘Oi’ as shorthand for obnoxious irritant. This forwards us from prêt-à-porter, ready to wear in French, at fret-à-ports, ready to swear at ports. In speakers, they’re virtually omnipresent. For every sealed or transmission-line speaker, there must be 100s with one, two or three holes attached to which are pipes of a certain length. Those act as resonators to enhance low- frequency reach and power. Depending on which direction they aim at (front, back or down), to what frequency they’re tuned and whether they’re high or low Q, ports can come with side effects which aren’t that often discussed.

    There’s the notion that good sound only matters in the sweet spot. That’s rooted in how stereo works. The perfect stereo illusion demands perfect symmetry by way of path-length equality between the left/right speakers and your ears. Anything outside that spot is sub optimal by definition. Why should a card-carrying audiophile care what happens outside his small comfort zone, there at the apex of our tribe’s sacred stereo triangle?

    I could think of two reasons. The first is social not asocial enjoyment. If one could do so without liabilities, why not make better sound in more seats or areas? Two, the sweet spot isn’t an island in a vacuum. It’s influenced by what else happens in the room. The air connects everything within it.


    Do a little experiment. Play some music containing substantial bass. Walk around your room. Stand in each front corner. Walk along the side walls. Stand to either side of the central chair as though there were more seats on each side. Walk up and down the virtual centre aisle. Map the entire space like a chequered table cloth. Unless you’re very lucky; or very good at setup; or simply happen to own one of the rare non-ported speakers… you should have noted rather uneven sound depending on your location. Particularly, you should have noticed how certain notes or bunches of them “went off” like a bell or debris from a mortar hit. This boom and associated wooliness could make listening in any of those spots most annoying indeed.

    Granted, you’ll never sit in the front corners. Why give a toss about those? If you’re not inclined to share, you might feel the same about any spot other than your hot seat. And that’s certainly a valid position to take. Even so, it still overlooks that if your shoe is too tight, it’s not only your foot that hurts. Your mood sours, your gait changes, your attention keeps getting diverted and so forth.


    The same is true for a room. “Faraway” bass pressure zones compress far finer more fragile HF which want to pass through them as reflections. Less pressurization, better treble. Also, high pressure zones create acoustic stress which our nervous system registers whether we’re aware of it or not. This leads to sooner fatigue. The proof is in the pudding. Temporarily stuff your ports with tightly rolled- up kitchen towels or anything else suitable. Repeat the walkabout. Not only should you notice less “room mode crap” (which that experiment proved was in fact a lot of port-induced crappola), you should also notice better easier more even sound in the hot seat. (Of course you’ll also have less bass power and perhaps even extension since you disabled that particular speaker’s innate tuning.)

    Without massive room treatments, certain peaks and troughs are unavoidable. Acoustic energy distribution below 200Hz will activate certain room modes based on placement and architectural geometry. Good setup simply insures that the seat doesn’t coincide with either a peak or trough though a cut will be less offensive.


    Just how big the before/after effect will be between open and closed ports depends on their tuning frequency, Q and your room. In my experience, the worst offenders are rear-firing ports whose tuning sits below 50Hz. I touched on this subject in the recent Æquo Audio Ensis loudspeaker review for my site. As a rarer sealed design, I compared it directly to a 2-way monitor with two rear ports per channel. Where the Ensis performed far less lumpy all around and likewise in the hot seat, the Kroma Audio Julieta was unlistenable in a rocking chair along the sidewall where it boomed like a juvenile truck. In the same spot, the Ensis performed unblemished. Ditto for more areas like my work desk, our dining table and others. While the Julieta was brilliant in the sweet spot, it was really fussy outside of it.

    Ports are popular because software can easily calculate their length and diameter for a given box volume and response goal. They allow more bass from smaller boxes with smaller woofers. Since small is popular, ports are, too. What few people tell you is that many ported designs will cause acoustic hot spots which are very easily mistaken for room modes, i.e. effects one thinks are endemic to the room and thus must be put up with. Not. It’s when one experiments with ported vs. sealed designs of similar bandwidth, in the same room, each optimized by precise location, that the penny begins to drop about self-inflicted pain. Invariably the sealed speaker will cause less “room” issues. It’ll sound better, more even and less lumpy in more places (a benefit on the social scale) and because of that, will sound better in the hot seat (a benefit on the asocial scale).


    If you’re invested in a ported speaker you love, never mind. You’ll have figured out how to best accommodate it. This article is for those who aren’t committed; who are still shopping for their next ‘serious’ speaker. It’s to those people that I recommend sealed speakers or transmission lines. If not you, then your significant other who does all her listening anywhere but in the sweet spot might just thank me. Actually, I’m certain you’ll be as well. Removing or minimizing port-induced issues really does have a demonstrable effect on the listening experience even in the ‘perfect’ spot. For good sport and to wrap up, obviously there are worse and lesser port offenders; and combinations of those and given rooms that will show up these interactions to varying degrees. But I’d still ask myself. Why buy into ‘less’ when one could avoid stepping into the muck altogether? Ode to Joy and all that…

    You can read more of Srajan’s supremely erudite audio coverage over at his own 6moons.

    Srajan Ebaen

    Written by Srajan Ebaen

    Srajan is the owner and publisher of 6moons. He used to play clarinet at the conservatory. Later he worked in audio retail, then marketing for three different hifi manufacturers. Writing about hifi and music came next, then launching his own mag. Today he lives with his wife Ivette and Nori and Chai the Bengal cats in a very small village on Ireland’s west coast, between the holy mountain Croagh Patrick and the Atlantic ocean of Clew Bay in County Mayo’s Westport area. Srajan derives his income from the ad revenues of 6moons but contributes to Darko.Audio pro bono.


    1. Imagine an audio system with two sealed speakers in the corners of the long wall of your room, a turntable and a receiver. This is a simple unobtrusive system with a stereo image covering just over half of the room. A social system many can enjoy at the same time. I did and have never upgraded it in 28 years.

    2. I have a sealed SVS sub located close to my main speakers. I turned down the sub’s volume and adjusted the crossover until it sounds right with most music. I have the equalizer set to flat in my music software, which I think yields the best sound from my main speakers. There are a few songs, though, maybe three or four out of the 3,200 I have in my playlist, for which the bass is way too heavy.

      I also have a sealed sub that I recently added for my TV. It always sounds good.

    3. And then we have the Larsen speakers which go hard against the wall, are also ported, but produce a soundstage that is pretty natural.

      There isn’t a sweet spot either and depending on how the original performance was recorded, the soundstage reproduction depends on whether its pan-potted monos, or stereo pairs in the mikes. With the Larsens you hear the differences.

      And these speakers don’t reproduce finely etched soundstage, but do seem to reproduce a more realistic sound field, everything else being equal.

      Me? No room treatment but some response smoothing using an Accuphase DG-58 voicing equaliser, and that’s it, Wherever one sits the spatial sense is more or less the same.

    4. Srajan, right on!
      Not only ported speakers create bass havoc in the rooms – the ports itself are guilty of severe distortions. From port noise (where velocity of the air simply overpowers capacity of the given port and gives out “nice” farting sounds) to audible vibration of the port itself (given the shitty materials that are used for most ports).
      Ports are really terrible in subwoofers – just try to listen to any ported subwoofer without the main speakers engaged – most are an awful mess.
      Sealed or OB subs are way to go.
      Jerry Cmehil
      Well Rounded Sound

    5. Jerry – I deliberately didn’t touch on other port issues to keep focused on the faux room mode effects. But you’re perfectly right. Ports screw with the time domain. That’s why it’s curious when some hi-profile makers tout precisely adjustable physical time alignments on their speakers, then embrace ported bass whilst talking of optimized group delay.

      And like you, I’d not touch a ported sub with a 100-foot pole. Open-baffle subs like various H-frames… now *there* is a most interesting topic. I’ve played with a few of them and concluded that, 30Hz limit excepted, they’re far less ‘room interactive’ and incredibly clean and quick if perhaps not quite as punchy as sealed subs. Regardless of bass EQ on the plate amps they came with, even with dual 18″ woofers, I measured good response to about 30Hz but nothing useful below. That’s where I can get my big sealed Zu Submission to go lower (also with EQ).

      But with the built-in directivity of H-frame subs due to their lateral nulls, they can solve certain typical issues. And the difference between OB and box-bass textures is amazing. Of course they have to be pretty big so can get domestically challenging. Definitely a great topic for discussion though.

      With this piece, I simply wanted to focus on the typical rear-port side effects of big speakers which I don’t see mentioned often enough. It’s such a relief when one finds out that it wasn’t one’s room after all but 50-75% of the issues one suffered were purely self-inflicted due to one’s choice of ported speaker -:)

      Of course now one is limited by the far sparser choices in sealed speaker designs. Still, it can be a very worthwhile effort to seek them out -:)

      • Timely piece for me as I’m currently shopping for new speakers. You mention in this reply “typical rear-port side effects of big speakers.” Are the negative effects of ports more problematic for larger speakers? I’m shopping for bookshelf speakers and my two finalists are the Vandersteen vlr wood (sealed), and Quad S2 (ported). Thanks.

      • Hi Srajan – thank you for your reply. You are probably familiar with Acoustic Elegance drivers. But if not – Czech them out – they make an outstanding woofers for an H Frame or OB. Cheers!

    6. Reflex or tuned enclosures are more efficient in the low frequencies than closed boxes. It’s true that sealed boxes have potentially better transient response, the cost being a reduction of 3 dB in the bass, meaning twice the power is required for a given SPL. Another drawback with sealed is driver’s extension which equals higher distorsion. Transmission line seem like the perfect alternative, more efficient, yet with a broader loading. Unfortunately, the lazy designer cannot predict the performance as easily and must rely on more prototypes (or insight) to get it right.

      • Transmission boxes tend to be quite deep and larger than usual so perhaps it not just a laziness of the designers but it is the desired form factor of the final design. With powered subwoofers sealed design is not an issue as there is more than enough power on tap and the subwoofer drivers are over-engineered to deliver outstanding performance. With sealed speakers “lazy” designer select drivers that is designed for such function – with proper motor and higher sensitivity of 90dB + to counteract the loss of the acoustic suspension. Cheers! JC

    7. Interesting perspective. I have 2 sealed Linn sub-woofers to complement innocuous bookshelf speakers (Wharfedale Diamond 9). I wonder if I should try blocking the forward firing ports on the bookshelves to see what happens. The thing that troubles me is my ability to balance whereas I never worried about that before. All I was doing was reinforcing the lower registers without beating up the midband but maybe there is more to learn here. Any advice?

    8. As the article indicated, the problematic side of ports depends on how they’re tuned, which direction they dire and how that interacts with your room. If you don’t have audible issues where you sit; and few to none in ‘secondary’ areas that are important to you… then there’s no problem as far as you are concerned.

      In my experience so far, “ambitious” port tunings (tuned low and of lesser damping to be, according to their designers, “more dynamic”) which aim out the back have been the most problematic. If you’ve got small monitors with front-firing ports and they blend seamlessly with your sub, no worries. If you’re curious, you can always stuff the ports, compensate on the sub for any losses in gain or extension, and see which way sounds to you the most even and non-lumpy. That’s down to trusting your ears and nothing else – and it’s quickly reversed if you don’t like it.

    9. So how does Albedo’s TL technology with tuned Helmholtz resonators sound out of the sweet spot in your listening room if there even is a sweet spot with these speakers?

    10. Unless a speaker is a true omni like a Duevel or German Physics, all speakers have a fixed sweet spot. That’s how the stereo illusion works: equal path length between both, with you right in the middle. With dispersion of standard front-firing speakers getting progressively narrower with rising frequencies, there are response shifts as you move out of the sweet spot; and other things in the soundstage begin to shift and so forth. Some speakers have a bigger or smaller window where things remain acceptably stable but the perfect stereo illusion relies on being equidistant to both boxes (in the middle) – unless it’s a true omni.

      This article was about how bad, spotty, lumpy or boomy things can get *outside* the sweet spot when a ported speaker misbehaves. With the Albedo being a downfiring TL, there is decidedly less port crap than with a rear-ported speaker that’s similarly tuned to go below 40Hz. In short, I can listen outside the sweet spot, be in a rocking chair against the side wall, sit on my writing desk on the other side wall or back at the dinner table and not suffer the same exaggerated bass boom and compression wooliness. Of course being outside the sweet spot now, imaging is screwed up and the treble response is, too. But that’s more like being in a “badder” seat in a concert. It’s bad not by what it exaggerates but by what it drops.

      With the Albedos and in non-critical mode, I can still enjoy music fully in those spots because there’s no interference distraction. The boom truck has left town. But the best sound remains in the sweet spot. Makes sense? And, the Albedos don’t amp up the usual pressure zones in the room to the same extent. That means they play cleaner in the bass – and with it, cleaner all over.

    MQA: a non-hostile takeover?

    iFi S/PDIF iPurifier: entry-level pricing, next-level results