Sealed vs ported

[William Lemmerhirt]

"Overall system performance is a function of the driver’s Thiele/Small parameters and enclosure volume, which together will determine system Q and the system’s resonant frequency. Below the resonant frequency, sealed subwoofers typically feature a shallow roll-off of 12dB/octave, which also corresponds with relatively low levels of group delay and ringing in the deep bass." [https://www.audioholics.com/loudspeaker-design/sealed-vs-ported-subwoofers]

"Group delay has been found to be a major predictor of the "tightness" or transient accuracy of a subwoofer system. Group delay, in it's mathematical form, is the negative derivative of acoustic phase with respect to♪ requency. That is, group delay is a measure of how fast the acoustic phase of the system changes. Lower group delay numbers are indicative of a "tighter" sound of the subwoofer (to a certain point; once below a certain threshold, changes in group delay are no longer reliably detectable. The actual threshold is beyond the scope of this page, and as such will not be discussed). Conversely, higher numbers can indicate a "looser" sound."[http://stereointegrity.com/wp-content/uploads/SIGroupDelay.pdf]

So I still didn’t see any proof that sealed is better for music. Most of the points to be made revolve around group delay which IMO and obviously others is usually so far below the threshold of audibility as to be considered if no consequence. Also, as mentioned, subwoofer Q, quality, integration and the room itself determine tightness. To say “sealed is best for music” is not only a gross misrepresentation, it’s also not true. I have designed, built and used BOTH kinds and you’re just plain wrong.

 

[Verdinut]

Sealed subs do not have tighter bass. Let's allow this myth to die in peace please.

This statement is exact provided that the ported woofer or sub has a Qts lower than 0.50, the box is tuned for the proper parameters of the driver, and that you drive it with a solid state amp. With a tube amp, the result will be totally different because of its high output resistance (low damping factor).

 

[lovinthehd]

This statement is exact provided that the woofer or sub has a Qts lower than 0.50, the box is tuned to the proper parameters of the driver, and that you drive it with a solid state amp. With a tube amp, the result will be totally different because of its high output resistance (low damping factor).

Are there really subs driven by tube amps?

 

[Verdinut]

Are there really subs driven by tube amps?

Not commercially sold ones. But someone might try to use a tube amp with a passive sub and be disappointed with the results.

 

[lovinthehd]

Not commercially sold ones. But someone might try to use a tube amp with a passive sub and be disappointed with the results.

Hard to imagine doing such.

 

[Verdinut]

Hard to imagine doing such.

With people, anything is possible.

 

[lovinthehd]

With people, anything is possible.

Let alone audiophiles

 

[KEW]

Your propogating an old audiophile myth, nothing more.

Actually, I would be inclined to say it was an old audio truth, but a modern myth!
I believe if we went back 30 years and listened, we would mostly agree that sealed subs were best for music!
That doesn't dispute what is being said except instead of acting like this is insanity, it is better to recognize that the statement does have an honest origin before subwoofer design matured to the level it has.
I am not disputing you in particular, 3db, you just gave me a good quote to work off of!
TL subs may have been "tight" 30 years ago, but they are a rarity and not what people generally speak of when they say ported sub.
To TLSGuys point that group delay is not so critical, Josh Ricci answered the question of which measurement would best predict the "tightness" (with tightness defined as less overhang of notes after the signal stopped) and his response was that having a greater portion of higher frequency energy as compared to low frequency energy was the best predictor of tightness. This means that a simple sealed sub with its natural roll-off (without EQ to keep a flat response into the 20's) and a simple ported sub with no EQ and port tuned to a flat anechoic response would sound boomy in a typical room after it was put in a corner or along a wall as they generally are.
I expect Josh Ricci more than anyone else to actually know the answer to this question, and I also would trust him to say "I don't know if he didn't!
In this age, the discrepancies between sealed and ported are largely minimized and good subs allow you a great degree of flexibility such that you can give a ported the characteristics of a sealed and a sealed the characteristics of a ported.

 

[William Lemmerhirt]

Well @KEW I’m glad we don’t have the same designs as 30 years ago!!! Lol

 

[shadyJ]

The time

"Overall system performance is a function of the driver’s Thiele/Small parameters and enclosure volume, which together will determine system Q and the system’s resonant frequency. Below the resonant frequency, sealed subwoofers typically feature a shallow roll-off of 12dB/octave, which also corresponds with relatively low levels of group delay and ringing in the deep bass." [https://www.audioholics.com/loudspeaker-design/sealed-vs-ported-subwoofers]

"Group delay has been found to be a major predictor of the "tightness" or transient accuracy of a subwoofer system. Group delay, in it's mathematical form, is the negative derivative of acoustic phase with respect to♪ requency. That is, group delay is a measure of how fast the acoustic phase of the system changes. Lower group delay numbers are indicative of a "tighter" sound of the subwoofer (to a certain point; once below a certain threshold, changes in group delay are no longer reliably detectable. The actual threshold is beyond the scope of this page, and as such will not be discussed). Conversely, higher numbers can indicate a "looser" sound."[http://stereointegrity.com/wp-content/uploads/SIGroupDelay.pdf]

Here is the thing: you say that sealed subs are better for music and then cite group delay as the reason why. Well, go look at the group delay difference between sealed and ported subs in music frequency bands, i.e., above 40 Hz. There really isn't any. In fact, some of the best group delay performance I have seen in music frequencies were in ported subs. Also keep in mind nearly every sealed sub you can buy comes with filters, and with filters comes group delay.

 

[lovinthehd]

The time

Here is the thing: you say that sealed subs are better for music and then cite group delay as the reason why. Well, go look at the group delay difference between sealed and ported subs in music frequency bands, i.e., above 40 Hz. There really isn't any. In fact, some of the best group delay performance I have seen in music frequencies were in ported subs. Also keep in mind nearly every sealed sub you can buy comes with filters, and with filters comes group delay.

Just for fun, and not audibility issues, how about behaviour of 20-40 Hz particularly?

 

[shadyJ]

Just for fun, and not audibility issues, how about behaviour of 20-40 Hz particularly?

I should have added a caveat to my previous statement that group delay in ported subs is largely the same as in sealed subs in music ranges- but for ported subs that are tuned to deep frequencies, such as the brands that are often discussed here, like Outlaw Audio, Monolith THX, Hsu, SVS, JTR, etc. Ported subs that have higher tuning frequencies are another matter, such as many of the cheap bandpass subs seen in HTiB setups.

In those ported subs, we normally see a rise in group delay in deep frequencies that hit about 1 phase cycle lag at port tuning. So if the sub is tuned to 20 Hz, the group delay increases as you get closer to the tuning frequency, as the port output makes a increasing contribution to overall output. There can be more group delay depending on the kind of limiters used. There can also be DSP tricks that can be used to get less than 1 cycle group delay at port tuning.

The group delay that filters can have on sealed subs can vary depending on the severity of the filter. Sometimes it can be mild, other times it can exceed group delay levels typically seen in a ported sub.

 

[Auditor55]

Pursuing the Truth: While sealed subs have less group delay inherent in the design, EQ used to restore the response to flat adds some group delay back. Also, these marginal differences in group delay are not very audible, if audible at all. Far more important is the in-room frequency response.

Pursuing the Truth: I call shenanigans. Nonsense again. If a ported subwoofer sounds boomy it’s either a poor design with a non-flat response or is poorly set up (which is not something inherent in ported designs). Well designed ported subs are just as tight and articulate as sealed subs. In many cases, the increased tightness some perceive from sealed subs is simply the fact that there is less bass coming from the bottom octaves in a sealed design. However, that is nothing more than a response issue and can be mimicked in a ported design. While there are poorly designed ported subwoofers, there are just as many poorly designed sealed subwoofers. This is not a point for comparison.

Ten Nonsense Myths About Subwoofers and Bass Busted!

There are as many myths in the audio industry as are written in the pages of a Tolkien novel. With that in mind, Audioholics is taking on the task of myth busting ten bass myths that are nonsense!

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Interesting.

The time

Here is the thing: you say that sealed subs are better for music and then cite group delay as the reason why. Well, go look at the group delay difference between sealed and ported subs in music frequency bands, i.e., above 40 Hz. There really isn't any. In fact, some of the best group delay performance I have seen in music frequencies were in ported subs. Also keep in mind nearly every sealed sub you can buy comes with filters, and with filters comes group delay.

ShadyJ, you are correct in that I was pointing to "less group delay" as a possible reason why sealed subs would be preferred for music over ported as it equates to ,subjectively, tighter bass or articulate bass.

The time

Here is the thing: you say that sealed subs are better for music and then cite group delay as the reason why. Well, go look at the group delay difference between sealed and ported subs in music frequency bands, i.e., above 40 Hz. There really isn't any. In fact, some of the best group delay performance I have seen in music frequencies were in ported subs. Also keep in mind nearly every sealed sub you can buy comes with filters, and with filters comes group delay.

Great knowledge. Thanks!

 

[Verdinut]

ShadyJ, you are correct in that I was pointing to "less group delay" as a possible reason why sealed subs would be preferred for music over ported as it equates to ,subjectively, tighter bass or articulate bass.

Sealed subs don't have a tighter bass than a well designed ported one. That's false info which you get on the web from people with no knowledge of speaker operation and speaker building, or some manufacturers which don't sell ported subs.

 

[Pogre]

ShadyJ, you are correct in that I was pointing to "less group delay" as a possible reason why sealed subs would be preferred for music over ported as it equates to ,subjectively, tighter bass or articulate bass.

That's certainly debatable as for it to equate to, subjectively, "tighter bass or articulate bass" I would think it would have to be audible. Which in my experience, and there's data to support it, is not the case. In my opinion that assertion is entirely false.

 

[3db]

Interesting.


ShadyJ, you are correct in that I was pointing to "less group delay" as a possible reason why sealed subs would be preferred for music over ported as it equates to ,subjectively, tighter bass or articulate bass.


Great knowledge. Thanks!

If there is less of something already inaudible, in this case group delay, then there can be no way of telling whether a sub is sealed or ported. Subjective audiophile myth is all.

 

[Auditor55]

I watched these two heavyweights go at in the sealed vs ported sub debate.

 

[TankTop5]

What you say is only half the truth. Yes, but if you select a low Q driver you find F3 is so high that you need to start EQ at a point where the driver becomes distressed. So distortion rises and output is limited. Sealed subs are highly inefficient and loudspeaker cones are very poor couplers to the air, and have severe difficulty filling large volumes.

Properly designed ported enclosures can have very acceptable Qt and sound excellent without stressing drivers. The only advantage of a sealed sub is smaller size, after that it is all down hill and negative.

Group delay is greater in ported subs, but its audible effects are very controversial.

I use transmission lines to reproduce the bass in 2 out of my three systems. Now TLs have high group delay, but are highly efficient and can be designed to be aperiodically damped and low Q. However the bass reproduction is the most natural of all, with cone motion tightly controlled and they are highly effective at filling spaces. The bass reproduction of a properly designed TL is incredibly natural. To me that gives the lie to this group delay argument for sealed subs.

Basically putting a driver in a sealed box for the reproduction of the last octave is in fact a terrible idea, with the only thing for it being smaller box size.

I was thinking of attempting a pair of TL sub using either morel drivers or Rythmik’s with custom made servo amps (yes they make them) for a TL design. Then I realized I was but a mere mortal. If only either company would design and build or license a knock down box design for a 12”-15” driver.... I’m thinking 15” x 24”x 9’ may be big enough!

 

[Auditor55]

If there is less of something already inaudible, in this case group delay, then there can be no way of telling whether a sub is sealed or ported. Subjective audiophile myth is all.

There are claims that group delay is in audible, particularly at the pertinent musical frequencies, however have anyone actually conducted an ABX style listening to test confirm that claim.

 

[3db]

There are claims that group delay is in audible, particularly at the pertinent musical frequencies, however have anyone actually conducted an ABX style listening to test confirm that claim.

There are claims that people can hear differences in amplifiers but refuse to partake in blind listening tests. Until they partake and able to distinguish reliably, then I remain skeptical.