Sealed vs ported

[William Lemmerhirt]

May ask then, if money was no object and assuming you was end the market for a sub, what kind of subwoofer would you most likely end up owning? I ask because it seems that most of the money no object, high-end subwoofers are sealed and not ported.

I’d be interested in seeing some metrics about this point. Some are sealed, like JL for example that doesn’t even make ported subs. But I haven’t found their performance(in the home market) to be worth the premium. No take someone like JTR. Jeff makes both, and his ported subs are some of the most highly regarded subs anywhere.

To answer your question, I would still buy ported. Part of what makes the answer to this tricky, is that I would consider ported subs ONLY IF I could have enough of them to equal the output of X amount ported subs. And also, the only reason I would even consider that would be to chase single digit bass. Room size and construction vs output and extension goals would dictate all of that as well.
But yeah, still ported.

To the point about early ported HT subs being boomy slow fart boxes, that’s basically true. Once SVS and HSU started making first rate subwoofers that normal people could afford, it changed the game. Problem is, there are too many people who just won’t let go of that. And here we are...still.....

 

[Pogre]

Just reflecting back on what I came out the so-called debate between Matthew and ShadyJ on this very topic. ShadyJ kind of talked about how ported boxes got the reputation of being boomy, slow and non-musical from poorly designed ported boxes, mostly from the home theater in the type box packages. Personally I suspect that there were many type of poorly designed ported boxes that goes beyond just the "home theater in the box" and were ubiquitous in the market for a certain period until the SVS, HSU, etc. came along and started the trend of well designed ported boxes.

So what you're saying is, do your homework, buy a well designed ported sub and avoid the crappy ones? That's revelatory, I never thought of it that way before. I agree with you 100%.

 

[mojave]

Any filter that is added in DSP adds latency to the signal. A miniDSP 2x4 with no filters has a latency of 1.08ms. However, if you add a high pass filter, the latency can go from 7 ms up to >30 ms depending on the frequency and slope of the high pass filter.

A ported subwoofer will have a high pass filter in its DSP and a sealed subwoofer will not. If they are at the same plane, the L/R speakers needs to be delayed in relationship to the subwoofer in order to be in time and phase and the crossover region. Many "music" systems do not use a receiver and have no method of delaying the main speakers. All "movie" systems have a method of delaying the mains since a processor or receiver is used.

In a "music" system without the ability to delay the mains, the main speakers will always be closer in time and phase alignment to a sealed subwoofer than a ported subwoofer because there is less latency. In a "movie" system, the system can be calibrated using the delay and polarity controls so the DSP latency doesn't matter as much.

In a two channel music system without the capability to delay the mains, a ported subwoofer will fatten the time alignment envelope at the crossover. The overlapping frequencies will be spread out over time. This is very noticeable with bass guitar or double bass. This is considered "slow bass" in comparison to the sealed subwoofer which has less latency and thus a "tighter" sound.

 

[Verdinut]

Just reflecting back on what I came out the so-called debate between Matthew and ShadyJ on this very topic. ShadyJ kind of talked about how ported boxes got the reputation of being boomy, slow and non-musical from poorly designed ported boxes, mostly from the home theater in the type box packages. Personally I suspect that there were many type of poorly designed ported boxes that goes beyond just the "home theater in the box" and were ubiquitous in the market for a certain period until the SVS, HSU, etc. came along and started the trend of well designed ported boxes.

Back in 1960's, for the North american market, there were some manufacturers, notably Altec Lansing, JBL, Electro-Voice, Jensen, KEF, Wharfedale and a few more that had a certain knowledge of a well designed ported enclosure. But following the research done by J. F. Novak in the late 1950's, Australian engineer, A. N. Thiele added to the research on vented box alignments and in 1972, R.H. Small published a series of articles extending on Thiele's research. By the mid-1970's, the T/S parameters were getting easily available and most commercial speaker manufacturers were able to release well designed ported speakers:

Thiele/Small parameters - Wikipedia

en.wikipedia.org

 

[Pogre]

Any filter that is added in DSP adds latency to the signal. A miniDSP 2x4 with no filters has a latency of 1.08ms. However, if you add a high pass filter, the latency can go from 7 ms up to >30 ms depending on the frequency and slope of the high pass filter.

A ported subwoofer will have a high pass filter in its DSP and a sealed subwoofer will not. If they are at the same plane, the L/R speakers needs to be delayed in relationship to the subwoofer in order to be in time and phase and the crossover region. Many "music" systems do not use a receiver and have no method of delaying the main speakers. All "movie" systems have a method of delaying the mains since a processor or receiver is used.

In a "music" system without the ability to delay the mains, the main speakers will always be closer in time and phase alignment to a sealed subwoofer than a ported subwoofer because there is less latency. In a "movie" system, the system can be calibrated using the delay and polarity controls so the DSP latency doesn't matter as much.

In a two channel music system without the capability to delay the mains, a ported subwoofer will fatten the time alignment envelope at the crossover. The overlapping frequencies will be spread out over time. This is very noticeable with bass guitar or double bass. This is considered "slow bass" in comparison to the sealed subwoofer which has less latency and thus a "tighter" sound.

Sure, there are situations like you describe where sealed is preferred, no one is denying that. Size is also a factor. If I didn't have room for a ported sub then a sealed sub would be my choice. Does that make sealed subs "better" in general? I would say no, it makes them better for you. It depends on your situation.

Personally I'm a big fan of bass management and avoid gear that limits my ability to properly blend a sub with my speakers.

*Edit: Don't most sealed designs use some form of dsp to improve deep bass extension? That adds delay also, doesn't it?

 

[shadyJ]

Any filter that is added in DSP adds latency to the signal. A miniDSP 2x4 with no filters has a latency of 1.08ms. However, if you add a high pass filter, the latency can go from 7 ms up to >30 ms depending on the frequency and slope of the high pass filter.

A ported subwoofer will have a high pass filter in its DSP and a sealed subwoofer will not. If they are at the same plane, the L/R speakers needs to be delayed in relationship to the subwoofer in order to be in time and phase and the crossover region. Many "music" systems do not use a receiver and have no method of delaying the main speakers. All "movie" systems have a method of delaying the mains since a processor or receiver is used.

In a "music" system without the ability to delay the mains, the main speakers will always be closer in time and phase alignment to a sealed subwoofer than a ported subwoofer because there is less latency. In a "movie" system, the system can be calibrated using the delay and polarity controls so the DSP latency doesn't matter as much.

In a two channel music system without the capability to delay the mains, a ported subwoofer will fatten the time alignment envelope at the crossover. The overlapping frequencies will be spread out over time. This is very noticeable with bass guitar or double bass. This is considered "slow bass" in comparison to the sealed subwoofer which has less latency and thus a "tighter" sound.

All DSP driven speakers and subs have added latency due to the processing. So any sealed subwoofer with DSP will have that latency as much as a ported sub. In fact, sophisticated enough DSP can help mitigate the group delay that unavoidably comes with the phase difference of port output. One way to get the whole system time-aligned is to add a delay to the speakers so that they match the "delayed" distance of the subs.

In a two channel system, the ported sub will not do anything to the time-alignment at the crossover point to the speakers unless it uses DSP in the amp, and the same would be true of a sealed sub using DSP. This also assumes that the two channel system had no way to compensate for that delay, like it is an analog system. The idea that a ported sub has some kind of time-domain disadvantage in music frequencies is a myth that needs to be beaten to death with a shovel.

 

[mojave]

All DSP driven speakers and subs have added latency due to the processing. So any sealed subwoofer with DSP will have that latency as much as a ported sub. In fact, sophisticated enough DSP can help mitigate the group delay that unavoidably comes with the phase difference of port output. One way to get the whole system time-aligned is to add a delay to the speakers so that they match the "delayed" distance of the subs.

I just explained why the latency in the DSP in a sealed subwoofer is different than a ported subwoofer. Below is the actual latency in a miniDSP 2x4 with various crossover filters. A high pass filter also adds latency in the DSP (which is only used in a ported subwoofer).

In a two channel system, the ported sub will not do anything to the time-alignment at the crossover point to the speakers unless it uses DSP in the amp, and the same would be true of a sealed sub using DSP. This also assumes that the two channel system had no way to compensate for that delay, like it is an analog system.

I specifically said, "without the means to delay the mains" which is what happens in most 2 channel systems. When I do the shows at AXPONA and RMAF with JTR Speakers, nobody else uses any delay on the mains when demoing a 2 channel system with subwoofers. We are the only ones that I've seen with correct time and phase alignment. When I did did all the measurements and EQ for a subwoofer GTG with Jeff Permanian and Mark Seaton present, the main speakers and the subwoofer locations stayed the same. However, the distance setting required was the least with sealed subwoofers, longer with ported subwoofers, and the greatest with horn subwoofers.

The idea that a ported sub has some kind of time-domain disadvantage in music frequencies is a myth that needs to be beaten to death with a shovel.

You are switching subjects. Once aligned in time at the crossover frequency, a sealed subwoofer has no time-domain advantage - which is why anyone with the capability to time, phase, and polarity align the subwoofer to the main speaker has other reasons for choosing between sealed and ported subwoofers.

However, the issue that I brought up is that the DSP latency is different for different subwoofer alignments due to the different filters required. If one does loopback measurements of miniDSP, Behringer DCX2496, dbx PA2, Lab Gruppen LM44, QSC DSP-30, etc., they will realize how the latency changes depending on filters being used.

I've measured the following JTR Speakers subwoofers: Captivator 4000ULF, Captivator 2400, Captivator 118HT, Captivator S2, Captivator S1, Orbit Shifter LFU. The S1 and S2 have the least amount of latency in the SpeakerPower amplifier. It isn't something that can be called a "myth". It is real and it affects ones ability to integrate a subwoofer into a 2 channel system with no means of delay for the mains.

 

[mojave]

*Edit: Don't most sealed designs use some form of dsp to improve deep bass extension? That adds delay also, doesn't it?

The delay added by a high pass filter is greater than the delay added by a shelving filter.

 

[shadyJ]

I just explained why the latency in the DSP in a sealed subwoofer is different than a ported subwoofer. Below is the actual latency in a miniDSP 2x4 with various crossover filters. A high pass filter also adds latency in the DSP (which is only used in a ported subwoofer).

View attachment 36006


I specifically said, "without the means to delay the mains" which is what happens in most 2 channel systems. When I do the shows at AXPONA and RMAF with JTR Speakers, nobody else uses any delay on the mains when demoing a 2 channel system with subwoofers. We are the only ones that I've seen with correct time and phase alignment. When I did did all the measurements and EQ for a subwoofer GTG with Jeff Permanian and Mark Seaton present, the main speakers and the subwoofer locations stayed the same. However, the distance setting required was the least with sealed subwoofers, longer with ported subwoofers, and the greatest with horn subwoofers.


You are switching subjects. Once aligned in time at the crossover frequency, a sealed subwoofer has no time-domain advantage - which is why anyone with the capability to time, phase, and polarity align the subwoofer to the main speaker has other reasons for choosing between sealed and ported subwoofers.

However, the issue that I brought up is that the DSP latency is different for different subwoofer alignments due to the different filters required. If one does loopback measurements of miniDSP, Behringer DCX2496, dbx PA2, Lab Gruppen LM44, QSC DSP-30, etc., they will realize how the latency changes depending on filters being used.

I've measured the following JTR Speakers subwoofers: Captivator 4000ULF, Captivator 2400, Captivator 118HT, Captivator S2, Captivator S1, Orbit Shifter LFU. The S1 and S2 have the least amount of latency in the SpeakerPower amplifier. It isn't something that can be called a "myth". It is real and it affects ones ability to integrate a subwoofer into a 2 channel system with no means of delay for the mains.

I have measured lots of subwoofers, including subs from JTR. The group delay in frequency bands where crossovers typically occur is pretty much the same going from sealed to ported. But group delay is relative to frequency, of course, and it looks like you might be talking about an absolute delay. It may be that setting a high-pass filter can cause a system wide delay in something like a MiniDSP. The thing is most sealed subs use high-pass filters too, although not quite as aggressive ones as typically seen in ported designs. In a system where there is no way to compensate for DSP delay, you can't get perfect time-alignment with any sub no matter what. However, the discrepancy in time-alignment at the crossover is nothing compared to the audible damage that the room acoustics will do to the bass sound. Many ported subs use fourth-order high-pass filters for low-end protection which, according to the chart you posted, would cause a 6ms delay in a MiniDSP at the typical 80 Hz crossover frequency. I very much doubt that a 6ms delay would have a perceptible difference, especially in a typical room with nothing to flatten out the response.

My point here is that I think you incorrectly attributing the high-pass filter delay as the reason why sealed subs can make a bass guitar or double bass sound tighter. My hunch would be that is a matter of frequency response and not so much time domain issues. A system that can't account for DSP latency certainly would not be able to equalize the response in low frequencies either.

 

[mojave]

The thing is most sealed subs use high-pass filters too, although not quite as aggressive ones as typically seen in ported designs.

Not a single sealed subwoofer tested by data-bass uses a high-pass filter. I've also never heard of a single subwoofer designer use a high pass filter on a sealed subwoofer. In a properly sized sealed subwoofer, the air spring and available power keeps the driver's excursion from surpassing its limits.

However, the discrepancy in time-alignment at the crossover is nothing compared to the audible damage that the room acoustics will do to the bass sound.

Room modes don't change with position of the sub or speaker. They remain the same since they are based on the rooms dimensions. As such, they affect the subwoofer and the speaker at the same frequencies. They also affect sealed and ported subwoofers the same. However, your assertion that it "the discrepancy in time-alignment at the crossover is nothing" is flawed. The root problem of both room acoustics and time alignment has to do with phase alignment. In a room, reflections are out of phase with the original signal and cause frequency response issues. In time alignment between the subwoofer and main, the signals will also be out of phase and cause similar frequency response issues. However, not only are there frequency response issues, but there are also time domain issues. Room reflections are not necessarily more of a destructive or audible issue than speaker/sub time and phase alignment.

Many ported subs use fourth-order high-pass filters for low-end protection which, according to the chart you posted, would cause a 6ms delay in a MiniDSP at the typical 80 Hz crossover frequency. I very much doubt that a 6ms delay would have a perceptible difference, especially in a typical room with nothing to flatten out the response.

A 6 ms delay is 180 degrees of phase shift at exactly 83.3 Hz. That will be audible in just about any system with an 80 Hz crossover. On The Police Certifiable Blu-ray, Sting's bass guitar is produced almost entirely by the LFE channel. The LFE was unfiltered by the sound engineer so it contains both the fundamental and the harmonics. If you route the LFE to a main speaker and then through a crossover to the subwoofer, one can detect speaker/subwoofer timing issues down to 2 ms. One can hear the thickening of the bass as one expands the time window.

 

[shadyJ]

Not a single sealed subwoofer tested by data-bass uses a high-pass filter. I've also never heard of a single subwoofer designer use a high pass filter on a sealed subwoofer. In a properly sized sealed subwoofer, the air spring and available power keeps the driver's excursion from surpassing its limits.


Room modes don't change with position of the sub or speaker. They remain the same since they are based on the rooms dimensions. As such, they affect the subwoofer and the speaker at the same frequencies. They also affect sealed and ported subwoofers the same. However, your assertion that it "the discrepancy in time-alignment at the crossover is nothing" is flawed. The root problem of both room acoustics and time alignment has to do with phase alignment. In a room, reflections are out of phase with the original signal and cause frequency response issues. In time alignment between the subwoofer and main, the signals will also be out of phase and cause similar frequency response issues. However, not only are there frequency response issues, but there are also time domain issues. Room reflections are not necessarily more of a destructive or audible issue than speaker/sub time and phase alignment.


A 6 ms delay is 180 degrees of phase shift at exactly 83.3 Hz. That will be audible in just about any system with an 80 Hz crossover. On The Police Certifiable Blu-ray, Sting's bass guitar is produced almost entirely by the LFE channel. The LFE was unfiltered by the sound engineer so it contains both the fundamental and the harmonics. If you route the LFE to a main speaker and then through a crossover to the subwoofer, one can detect speaker/subwoofer timing issues down to 2 ms. One can hear the thickening of the bass as one expands the time window.

Most commercially available sealed subwoofers use a high pass filter of some kind, including the ones tested at data-bass.com. A glance at their frequency responses is enough to confirm that.

Regarding room and phase shift, phase is a relative thing. If the signal is 180 degrees out of phase at crossover, just adjust the phase control until it is back in phase. Pretty much every standalone sub that you can buy has a phase control. That may put the sub's sound a cycle behind the speakers, but if you have no way of flattening the response, the cycle of delay is not going to be the biggest problem anyway.

As for timing issues being audible down to 2ms in bass frequencies, I would need to see some serious research to support that. If that is what you think you heard, how do you not know that it wasn't the power of suggestion that you heard instead?

 

[lovinthehd]

Not a single sealed subwoofer tested by data-bass uses a high-pass filter. I've also never heard of a single subwoofer designer use a high pass filter on a sealed subwoofer. In a properly sized sealed subwoofer, the air spring and available power keeps the driver's excursion from surpassing its limits.

Well I know one sealed sub Josh commented on the eq boost in his review, since I own it, the Epik Empire. I'm pretty sure I've seen it for a few others too.

 

[mojave]

Well I know one sealed sub Josh commented on the eq boost in his review, since I own it, the Epik Empire. I'm pretty sure I've seen it for a few others too.

EQ boost and a hight pass filter are completely different.

 

[KEW]

Not a single sealed subwoofer tested by data-bass uses a high-pass filter.

That is a very emphatic statement!
What is the basis for this statement?
Are you making inferences from measurements or do you have some other insight into this?
It certainly makes some sense in that (my understanding is) if a ported sub receives a strong signal below the port tuning frequency, it is almost certain to cause damage, while a sealed sub will "take care of itself" by just "not making the attempt"!

 

[colofan]

Well to throw in a different angle. Consider what the pros do:

https://jblpro.com/en-US/products/5742

This is a JBL system designed for supporting Movie Theaters for many years.

Floyd Toole's book provides ABX testing. Properly designed ported systems have been around for a long time.

T/S parameters should be taken in context that they are developed for "Small signal analysis" lots of add ons needed for taking into account non-linear aspects of large xmax drivers. Checkout references by Kippel.

I have built all kinds for subs 6 inch to 24 inch.

Just additional food for thought....... Check out thee bandwidth needed for most music except percussive and organ most of it stops at 30Hz.

Pretty big difference reproducing 10Hz sound effect on Movie and a Bass guitar.

Roydan

 

[colofan]

Oh and hear is the matching Subwoofer that goes with the screen array

.https://jblpro.com/en-US/products/5628

Roydan

 

[lovinthehd]

EQ boost and a hight pass filter are completely different.

Yeah am getting a bit corona-goofy I think I was just thinking eq generally from earlier on....

However, would like you to expand on room modes not being affected by sub position....

 

[Steve81]

Yeah am getting a bit corona-goofy I think I was just thinking eq generally from earlier on....

However, would like you to expand on room modes not being affected by sub position....

FWIW Josh mentions a probable high pass w/ the Epik:

The Empire exhibits a nicely extended upper range response and is useful up to at least 200Hz. The response is boosted near 20Hz to extend the frequency response corner, but the filter also seems to include a high pass filter so it will not be able to make use of room gain in the same manner an unfiltered sealed subwoofer would.

He also mentions a high pass with the sealed Emotiva X-Ref12:

This sub did not have much overall output though and the extension is effectively limited to barely 25Hz via a very sharp 18dB/octave high pass filter that results in a 30dB/octave acoustic roll off when combined with the 12dB/octave from a sealed system.

The Reaction PS15X:

The amplifier proved to be quite powerful but even still, it appeared to run out of steam before the driver became truly overloaded. The amplifier offered does have a high pass filter which rolls off the output of this sealed system below 20hz, so it limits the ability to take advantage of room gain a bit.

The JL E110 and E112

The E110 exhibits a smooth response that is shaped by some low bass boost and what appears to be a 12dB octave high pass filter below 20Hz. The response shape fits within a 6dB window from 21-143Hz.

The E112 exhibits a smooth response that is shaped by some low bass boost and what appears to be a 12dB octave high pass filter below 20Hz. The E112's basic response shape fits within a 6dB window from 19-135Hz.

The ML Dynamo 1500X

There is some increased ringing and excess group delay down below 25Hz due to the large amount of EQ boosting used to extend the response and the high pass filter applied immediately below 20Hz, but it is unlikely to be audible.

The Velo DD18+

There doesn't appear to be a good reason to use the high pass filter set any higher than its minimum 15Hz 6dB per octave setting. In truth Velodyne could probably move this down to 10Hz or remove it entirely since the platform appears to be utterly stable and well protected.

 

[lovinthehd]

FWIW Josh mentions a probable high pass w/ the Epik:


He also mentions a high pass with the sealed Emotiva X-Ref12:


The Reaction PS15X:


The JL E110 and E112


The ML Dynamo 1500X


The Velo DD18+

Thanks, didn't even reread it to support my position