Sealed versus Ported Bass, can the difference be measured?

[Paul McNeil]

I recently replaced three ported Klipsch THX 120 subs, stacked in one corner of the room, with a SVS Ultra SB-17. In the other corner are two SVS Ultra 13 cylinders operating not in the sealed mode. Previously these SVS cylinders and the Klipsch operated in the ported mode. Now, with the sealed arrangement, the REW measurement is good (attached), I think, but similar to that of the previous all-ported mode. EQ is by Dirac with Bass control via a Marantz AV10.

But can I get subjective, not only does the bass have more more convincing detail but the detail is better all around, both for music and movies, and this last was a surprise, with an improvement in dialogue clarity, I think.

Here's the REW measurement for the new, sealed arrangement...

 

[levimax]

There can certainly be measurable and audible differences between subs, whether they are ported or sealed is not as important as the complete design of the sub.

Your measurement shows FR which is part of the story but not all. Is that a MMM measurement or a sweep? If a sweep I would compare the group delay, distortion, and time alignment in REW of the old and new set up for any differences which may explain what you are hearing. If the measurement is MMM you unfortuneately would have to set up the old system and measure it with sweeps and do the same with the new set up.

 

[staticV3]

Sealed versus Ported Bass, can the difference be measured?

See here:

I measured 10 subwoofers.

Hi, it's been a while! I would like to thank the people who made this project possible on a scale never before imagined in South Korea. I measured a total of 10 subwoofers, including my own DIY subwoofer(L26RO4Y), and measured them to the CEA-2010 standard using a Klippel TBM module. Below are...

www.audiosciencereview.com

 

[kemmler3D]

If there is a big measurable difference from switching to sealed, it may show up in the decay/ waterfall views. You would need to look at before/ after measurements to see the change.

 

[amirm]

You have made too many concurrent changes to draw any conclusions. It would be good to do this test in a controlled manner.

 

[Holmz]

I recently replaced three ported Klipsch THX 120 subs, stacked in one corner of the room, with a SVS Ultra SB-17. In the other corner are two SVS Ultra 13 cylinders operating in the sealed mode. Previously these SVS cylinders and the Klipsch operated in the ported mode. Now, with the sealed arrangement in both corners, the REW measurement is good (attached), I think, but similar to that of the previous all-ported mode. EQ is by Dirac with Bass control via a Marantz AV10.

But can I get subjective, not only does the bass have more more convincing detail but the detail is better all around, both for music and movies, and this last was a surprise, with an improvement in dialogue clarity, I think.

Here's the REW measurement for the new, sealed arrangement...

“Sealed versus Ported Bass, can the difference be measured?”​

Well.. not the way you are measuring it.


It would be measurable in transcient response or in group delay.
Just not in a frequency response plot… (which is a perennial boner-plot on here… like that is all that there is, ever was, and ever will be.)

 

[TurtlePaul]

It would be measurable in transcient response or in group delay.

And in distortion vs. frequency.

 

[Holmz]

And in distortion vs. frequency.

^yeah ok - you have a point.^
But distortion, especially in subwoofer frequencies is pretty difficult to hear.
I suppose a lot of higher order harmonics could really stand out.

Chuffing and rattles are a real thing.

 

[Keith_W]

^^^ What Amir said. If you want to see what the difference is, keep all the variables the same and only change the variable you want to study. Do not change microphone position, do not repeat the Dirac calibration between configurations, etc. Re-measure with the ports open and the ports closed, and post the MDAT. That's it.

 

[ppataki]

I recently replaced three ported Klipsch THX 120 subs, stacked in one corner of the room, with a SVS Ultra SB-17. In the other corner are two SVS Ultra 13 cylinders operating not in the sealed mode. Previously these SVS cylinders and the Klipsch operated in the ported mode. Now, with the sealed arrangement, the REW measurement is good (attached), I think, but similar to that of the previous all-ported mode. EQ is by Dirac with Bass control via a Marantz AV10.

But can I get subjective, not only does the bass have more more convincing detail but the detail is better all around, both for music and movies, and this last was a surprise, with an improvement in dialogue clarity, I think.

Here's the REW measurement for the new, sealed arrangement...

I think we discussed this topic in many other threads here but to summarize:

Sealed design will have:
- lower group delay
- less phase rotation
- 12dB/octave slope (instead of 24dB/oct. of ported designs)

Due to the mild rolloff mentioned above, you can apply a low shelf filter (or any Linkwitz Transform) to linearize the low-end response of a sealed cabinet. Potentially reaching a lower knee frequency than ported designs.

Some caveats:
- your amp shall be able to cope with the increased load caused by the low shelf filter
- the speaker driver shall be able to tolerate the higher excursion caused by the low shelf filter
- a min phase low shelf filter will increase the group delay and introduce phase shift so probably you will end up with a similar response as with a reflex design (you can circumvent this by using linear phase filters though)

Some people (including me) *subjectively* prefer the way sealed speakers sound, while others don't

 

[voodooless]

You’ll primarily hear the difference in frequency response between closed and reflex. Sure the closed box may go lower as well, giving it more influence on room acoustics down there if you have a multi-sub arrangement. But the room is always dominant, and if you EQ the setups to the same response, it will probably sound very close to the same. The caveat here is that you cannot get them close enough because the local frequency responses are not the same, so the summation isn’t either. Again here, room effects and interactions with the subs prevail. It might very well be that the Kilpsch subs in different locations might yield similar results.

Do you have a before/after measurement? That should reveal what changed.

 

[TurtlePaul]

^yeah ok - you have a point.^
But distortion, especially in subwoofer frequencies is pretty difficult to hear.
I suppose a lot of higher order harmonics could really stand out.

Chuffing and rattles are a real thing.

Yeah, but for any given driver area, Xmax and SPL, the ported enclosure gives you more free bass extension.

 

[Paul McNeil]

I think we discussed this topic in many other threads here but to summarize:

Sealed design will have:
- lower group delay
- less phase rotation
- 12dB/octave slope (instead of 24dB/oct. of ported designs)

Due to the mild rolloff mentioned above, you can apply a low shelf filter (or any Linkwitz Transform) to linearize the low-end response of a sealed cabinet. Potentially reaching a lower knee frequency than ported designs.

Some caveats:
- your amp shall be able to cope with the increased load caused by the low shelf filter
- the speaker driver shall be able to tolerate the higher excursion caused by the low shelf filter
- a min phase low shelf filter will increase the group delay and introduce phase shift so probably you will end up with a similar response as with a reflex design (you can circumvent this by using linear phase filters though)

Some people (including me) *subjectively* prefer the way sealed speakers sound, while others don't

Yes, subjectively, as of now, I prefer sealed.

My question was, can I measure what I believe I hear as superior.

Can REW can measure lower group delay of phase rotation? It's the only objective tool I have. I've never seen these measured in an objective subwoofer review, but maybe that's just ignorance.

It seems to me to be an important issue given that sealed versus ported in a major decision for potential buyers.

P.S. My apologies for posting this topic twice. Is there any chance the two post could be merged?

 

[Paul McNeil]

You’ll primarily hear the difference in frequency response between closed and reflex. Sure the closed box may go lower as well, giving it more influence on room acoustics down there if you have a multi-sub arrangement. But the room is always dominant, and if you EQ the setups to the same response, it will probably sound very close to the same. The caveat here is that you cannot get them close enough because the local frequency responses are not the same, so the summation isn’t either. Again here, room effects and interactions with the subs prevail. It might very well be that the Kilpsch subs in different locations might yield similar results.

Do you have a before/after measurement? That should reveal what changed.

Yes, I do have REW measurements with the ported SVS/Klipsch arrangement. And the frequency response, equalized by Dirac live plus bass control is very similar. I could post these and other REW data if this would be helpful.

 

[voodooless]

Yes, I do have REW measurements with the ported SVS/Klipsch arrangement. And the frequency response, equalized by Dirac live plus bass control is very similar. I could post these and other REW data if this would be helpful.

Sure, post it. Let’s see what we can find…

 

[Paul McNeil]

Sure, post it. Let’s see what we can find…

OK, here it goes...

 

[Keith_W]

Can REW can measure lower group delay of phase rotation? It's the only objective tool I have. I've never seen these measured in an objective subwoofer review, but maybe that's just ignorance.

Yes. "GD" tab. (EDIT) did not see that you managed to figure it out. Note that if you did not use a time reference, it can change the Group Delay. For assurance I prefer to look at the plot from 20Hz - 20kHz to make sure the tweeter GD is the same in both measurements.

It's better to post the MDAT. Zip it first then upload it to ASR.

 

[voodooless]

Ported and sealed pictures are exactly the same

 

[Paul McNeil]

Please ignore those above, here's the 'right stuff', I think.

 

[Blueprint]

There is little convincing evidence anywhere of group delay audibility in low frequencies. I have always presupposed that the perceived ‘tightness’ people hear from sealed subwoofers is really just from the absence of very low frequencies that, by nature, rumble in a way that doesn’t sound tight.