Why Are Ported Speakers the Dominant Design?

[Theo]

I guess the use of computers to design the cabinet has helped improve the ported loudspeakers response, allowing for smaller, cheaper and louder ones...
OTOH, aren't the Dutch & Dutch, Devialet and Kii sealed cabinets? The use of DSP and class D amps will probably change the trend in the near future for active speakers.

 

[Cosmik]

Quoting Linkwitz:

Vented bass speakers are resonant structures and store energy which is released over time. For accuracy, bass must be reproduced from sealed or open baffle speakers that are non-resonant.

If you do things to the box or the signal that prevent those inaccuracies, you are preventing - or cancelling - resonance - pretty obvious. You want the resonator, you will have resonance. You can "control" it if you like, but you are simply setting your point between uncontrolled resonance and zero resonance; between resonance effects and no resonance effects - good and bad. For every resonance effect that you think is good (in terms of your frequency response and efficiency, perhaps) there is a price to pay in terms of the time domain or lack of control at lower frequencies. You can't have the good without the bad. If you build in a resonator and then attempt to oppose its effects completely, you would be better off not having the resonator in the first place.

 

[Wombat]

I guess the use of computers to design the cabinet has helped improve the ported loudspeakers response, allowing for smaller, cheaper and louder ones...
OTOH, aren't the Dutch & Dutch, Devialet and Kii sealed cabinets? The use of DSP and class D amps will probably change the trend in the near future for active speakers.

For sealed enclosure speakers I would think that it is more likely more rugged LF drivers that can withstand the substantial LF EQ applied.

 

[Juhazi]

For sealed enclosure speakers I would think that it is more likely more rugged LF drivers that can withstand the substantial LF EQ applied.

Like Theo and Wombat said, dsp and classD amps built-in give the control and power and multiple modern long-excursion woofers take care of air displacement necessary. Very high spl sets demand for even larger membrane area.

The boxer Devialet looks really funny when working hard!

 

[sfdoddsy]

The problem with ported satellite speakers is that they are designed as if they were expected to be full range.

So yes, porting helps them extend lower, but if you go too low you get fluffing due to the port resonance.

Given sensible people (whom I assume occupy this forum), use separate subs to get their bass fix, it is much easier to integrate a sealed satellite.

Alas, such a satellite will will sound bass-light in the showroom. And thus no-one will buy it.

So it's no surprise to me that the high-end home theater companies (and THX) who are used to blending with subs (and don't have showrooms) tend to have sealed satellites that roll off naturally at 80Hz.

If you have clever room EQ like Anthem ARC which adjusts for the speakers roll-off this is less of an issue, but most prepros get it wrong.

My current KEF R3s sound better with the ports running free when run full-range because they have nice bass. They measure better when crossed to subs with their ports stuffed.

 

[Wombat]

The problem with ported satellite speakers is that they are designed as if they were expected to be full range.

So yes, porting helps them extend lower, but if you go too low you get fluffing due to the port resonance.

Given sensible people (whom I assume occupy this forum), use separate subs to get their bass fix, it is much easier to integrate a sealed satellite.

Alas, such a satellite will will sound bass-light in the showroom. And thus no-one will buy it.

So it's no surprise to me that the high-end home theater companies (and THX) who are used to blending with subs (and don't have showrooms) tend to have sealed satellites that roll off naturally at 80Hz.

If you have clever room EQ like Anthem ARC which adjusts for the speakers roll-off this is less of an issue, but most prepros get it wrong.

My current KEF R3s sound better with the ports running free when run full-range because they have nice bass. They measure better when crossed to subs with their ports stuffed.

Is that lower than the design limits?

Fluffing??

 

[Wombat]

Quoting Linkwitz:

If you do things to the box or the signal that prevent those inaccuracies, you are preventing - or cancelling - resonance - pretty obvious. You want the resonator, you will have resonance. You can "control" it if you like, but you are simply setting your point between uncontrolled resonance and zero resonance; between resonance effects and no resonance effects - good and bad. For every resonance effect that you think is good (in terms of your frequency response and efficiency, perhaps) there is a price to pay in terms of the time domain or lack of control at lower frequencies. You can't have the good without the bad. If you build in a resonator and then attempt to oppose its effects completely, you would be better off not having the resonator in the first place.

Come again, again. You don't appear to have anything more here than a layman's subjective view of resonance. Do some study of the subject.

 

[Cosmik]

Come again, again. You don't appear to have anything more here than a layman's subjective view of resonance. Do some study of the subject.

The "I know but can't be bothered to say it, so look it up" ploy is so cliched, discredited, pathetic. If you know what you're talking about, then say it. If you don't, then don't. (I'm not quite as nice a person as @oivavoi )

 

[Wombat]

The "I know but can't be bothered to say it, so look it up" ploy is so cliched, discredited, pathetic. If you know what you're talking about, then say it. If you don't, then don't. (I'm not quite as nice a person as @oivavoi )

If you know what you are talking about(your claim) back it up. You know how this works. Stop the circumbobulation. Geez.

Your deflecting tactic doesn't work with me.

I have asked you more than once to substantiate your posit to no avail. Typical. Pointless to continue.

I am more interested in technical validity than discussion gymnastics.

Don't confuse 'nice' with garrulous. You do well on the latter.

 

[splattened]

Like this subwoofer built/cast into the basement.

Turning it, of course, into a bassment.

 

[KSTR]

Designing a good ported speaker is much harder than a sealed one, with much more variables to consider. But it can be done, and the way to verify this is to compare it to a speaker with the same driver in a sealed enclosure which is dialed in to have the same frequency response and LF roll-off (4th order) that the ported variant. At low volumes (driver not excursion-limited) they should sound and measure exactly the same and when they do you know you've nailed it. At higher levels the ported design has the edge but when really overdriving it things might get worse than with a sealed cab.

 

[pozz]

Designing a good ported speaker is much harder than a sealed one, with much more variables to consider. But it can be done, and the way to verify this is to compare it to a speaker with the same driver in a sealed enclosure which is dialed in to have the same frequency response and LF roll-off (4th order) that the ported variant. At low volumes (driver not excursion-limited) they should sound and measure exactly the same and when they do you know you've nailed it. At higher levels the ported design has the edge but when really overdriving it things might get worse than with a sealed cab.

By "measure the same" you mean the frequency response? Because from about 500Hz down for every ported speaker I've seen (with one exception, the JBL M2), there's a gradual increase in woofer's settling time. I'm no designer of course, but these measurements of studio monitors are pretty clear:

Neumann KH80 (ported)

Neumann KH310 (sealed)

Neumann KH420 (ported)

Fugu C4 (sealed, but it follows passive single-driver design like the ubiquitous Auratones and the active APS COAX)

Genelec 8351A (ported)

JBL M2 (ported)

These are really well behaved models. There are others like the sealed passive radiator Focal SM9, which sounded bloated to my ear although the frequency response is more or less flat (5dB variation). The low-Q tilt from around 500Hz downwards may be more responsible for that, possibly.

 

[watchnerd]

Back in the 70's I recall most speakers were sealed boxes. Today the vast majority are ported, except for subwoofers where sealed boxes compete with reflex designs. Offhand, the BBC mini monitor replicas are sealed and so are the expensive Magico line. There are also passive radiator designs. While there are not that many, they are a bit more mainstream with speakers from KEF and Goldenear, among others.

My personal hunch is ported speakers can be built with smaller cabinets, and cabinets are expensive. Likewise, a passive radiator costs more than drilling a hole in the box.

I'm going to blame it all on math, more design choices, and parts.

The Thiel-Small parameters and port box math, with modern software, makes it pretty easy to simulate a pretty decent 'starting point' for a design, and tweak the box volume and port dimensions really easily, with a lot of variables to tweak and play with.

With sealed box, you really only have one -- the box volume & matching driver.

As for passive radiators, it seems that most of the good implementations are custom to a particular design. If you shop a speaker catalog, there aren't even that many passive radiators to consider purchasing even if you like the idea.

 

[watchnerd]

Has anyone ever heard the sealed Benchmark SMS1 speakers? I'd like to pick those up one day for a listen.

Discontinued, apparently.

I'm not sure I'd buy a speaker from an amp maker, as a general rule of thumb. It's pretty outside their core expertise. They're unlikely to have a Spinorama or a Jupiter room.

 

[watchnerd]

I would be biased the other way round: asking the question why wouldn't it be like that? I am adding on a mechanical resonator. The unkind way to think about it is as a 'rumble hole'. The aim is to build up a resonance at a particular frequency. It changes the signal in the time domain, needing time to build up and time to die away - if it doesn't do those things it doesn't work. It isn't a miracle; it isn't a free lunch.

I'm curious what the measurement effect is for high passing a stand mount 1 octave above the port frequency, as I'm doing?

e.g. high pass at 80 Hz when port is tuned to about 40 Hz

 

[watchnerd]

I guess the use of computers to design the cabinet has helped improve the ported loudspeakers response, allowing for smaller, cheaper and louder ones...
OTOH, aren't the Dutch & Dutch, Devialet and Kii sealed cabinets? The use of DSP and class D amps will probably change the trend in the near future for active speakers.

I dunno...I can think of plenty of studio monitors that have Class D, DSP, and ports.

 

[DDF]

Ported speakers are popular simply because they can achieve lower over all system cost and size for the same low frequency performance as a sealed.

However there are drawbacks.

For constant drive voltage, sealed maintains relatively constant excursion over frequency below box resonance. Below a ported box tuning frequency the port unloads and the woofer excursion and distortion go way up compared to sealed. Most larger speakers get away with this being ported below 40Hz where program material rarely exists. Rare is not always. It also worth running the calculations for an eye opener: to avoid chuffing and high port distortion, low frequency ports have to be huge, and for sane alignments require large cabinets again. Ported speakers (especially small units with high tuning) rely on our lack of acuity to distortion in the bass.

Ported speakers also have a deficit of stuffing by necessity and poorer reduction of the back wave. Cones are opaque to the back wave.

Most actual commercial models also have port leakage and resonance further up the range which requires special attention to mitigate, which rarely happens. Happy examples to the contrary include KEF flex ports, internal baffle arrangements, external "muffler" resonators hanging off the port in the cabinet etc.

Really good ported speakers can be designed, but for fewer trade offs, I'll take sealed every time. A good sealed (small) cabinet augmented by sub woofers (Welti approach) will provide fewer performance trade offs but at a price.

 

[Blumlein 88]

snip........
As for passive radiators, it seems that most of the good implementations are custom to a particular design. If you shop a speaker catalog, there aren't even that many passive radiators to consider purchasing even if you like the idea.

Sonus Fabor used a full woofer as a passive radiator. They connected the terminals via a resistor so they could tune its behavior and damping. I always thought that was interesting. Vandersteen also used a full woofer that made for a semi-active passive. I forget how it was connected seems it was a capacitor in a way that made it coupled at some frequencies and not at others.

 

[watchnerd]

Sonus Fabor used a full woofer as a passive radiator. They connected the terminals via a resistor so they could tune its behavior and damping. I always thought that was interesting. Vandersteen also used a full woofer that made for a semi-active passive. I forget how it was connected seems it was a capacitor in a way that made it coupled at some frequencies and not at others.

Yeah, but both of those sort of prove the point.....custom implementations, much harder than just doing some port math.

 

[Juhazi]

One important flaw of ported/PR is "leakage" of midrange frequencies through the port. This can be a real problem for 2-ways. Passive woofers have way more resonances than a port, and suspensions modulus changes as time goes by.

JA of Stereohile always measures port output spl, but not decay. This is a good one.
(pozz, what is your source of decay plots?)