Sealed Subwoofers are my Cup of Tea

[Paul McNeil]

I am using Dirac Live plus Bass Control running on a Marantz AV10. Previously, I had run in one corner of my room two SVS Ultra 13 cylinders, in the ported mode (lowest frequency configuration). These were supplemented with three Klipsch THX subwoofers stacked in the other corner. Because of all those corner and proximity effects, the cones were barely moving (for example, the SVS were adjusted down 35 dB). So, a restless 'Audioholic', I decided to try sealed. In went the foam plugs into all of the SVS's three ports. And foam into the slot loaded ducts of the Klipsch. Wow, do I like the sealed sound, though the overall frequency response measured by REW is not that different. I guess I have ears for time domain and ringing. One surprising thing, after many adjustments, was that the sub 20 htz response was improved. The sound for classical and acoustic jazz is to die for, everything else is fine too.
Here's the latest REW measurement. Any thoughts?

 

[ski2xblack]

Measurement looks great, particularly for subs placed in the corners. Kudos.

I don't know if I would chalk it up to your sensitivity to time domain and ringing. Maybe, maybe not. In good, capable ported designs, time domain issues occur so low as to not be much of an audible issue. We hear frequency and amplitude, mainly.

The arguments against sealed subs is generally that they are less efficient than ported for reproducing low frequencies, and require a brute-force approach regarding amp power secondary to huge boosts required for extended low frequency reproduction. Ported subs do have more phase shift as they roll off more steeply, and the fact that you have two different models with slightly different extensions might come into play there.

So keeping that in mind, lets see how it applies to your setup. You overcome the main objections to sealed subs via two distinct means. First, your five sub collection has the brute force by virtue of the sheer number of subs. With so many subs dividing the load, your setup must have gobs of available headroom and virtually zero modulation or drive level related distortion. They're all just loafing along, way down in their low-distortion zone of their safe operating areas. And second, your choice of corner placement and the rather dramatic boundary gain that entails, when combined with the slightly shallower roll-off of sealed alignment, allows them to extend in-room as deep as they do. The fact that the subs are stacked means slightly different locations for sources of low frequencies, so despite that they are all in corners of the room, it will result in more distributed modal excitation and smoother measurements.

So I think you essentially used a brute force approach to sidestep the limitations of sealed subs, while maybe benefiting slightly from their strengths in the time domain, to arrive at well measuring and subjectively satisfying results.

Being satisfied with the results, for maximum musical enjoyment, is the whole point of all this, after all. Time to boogie down to the music!!

Oh, and you must have a very forgiving wife.

 

[Paul McNeil]

Measurement looks great, particularly for subs placed in the corners. Kudos.

I don't know if I would chalk it up to your sensitivity to time domain and ringing. Maybe, maybe not. In good, capable ported designs, time domain issues occur so low as to not be much of an audible issue. We hear frequency and amplitude, mainly.

The arguments against sealed subs is generally that they are less efficient than ported for reproducing low frequencies, and require a brute-force approach regarding amp power secondary to huge boosts required for extended low frequency reproduction. Ported subs do have more phase shift as they roll off more steeply, and the fact that you have two different models with slightly different extensions might come into play there.

So keeping that in mind, lets see how it applies to your setup. You overcome the main objections to sealed subs via two distinct means. First, your five sub collection has the brute force by virtue of the sheer number of subs. With so many subs dividing the load, your setup must have gobs of available headroom and virtually zero modulation distortion. And second, your choice of corner placement and the rather dramatic boundary gain that entails, when combined with the slightly shallower roll-off of sealed alignment, allows them to extend in-room as deep as they do. The fact that the subs are stacked means slightly different locations for sources of low frequencies, so despite that they are all in corners of the room, it will result in more distributed modal excitation and smoother measurements.

So I think you essentially used a brute force approach to sidestep the limitations of sealed subs, while maybe benefiting slightly from their strengths in the time domain, to arrive at well measuring and subjectively satisfying results.

Being satisfied with the results, for maximum musical enjoyment, is the whole point of all this, after all. Time to boogie down to the music!!

Oh, and you must have a very forgiving wife.

You nailed that one, I do have a very forgiving wife!
And, I agree, I can use 'brute force', not only because of the corner locations but also because the subs (paired and tripled) proximity to each other (I think this is a 6 dB gain for the pair, who knows for the triple).
Of course, I may change my mind about the sound I'm hearing, as a restless audiophile, but am boogying now.
Thanks for your thoughtful and positive input.

 

[MrBoat]

I sure do enjoy my sealed subs but my main speakers were pretty much enough for a music first system, to start with. What little they contribute below say 30hz, is still overkill in my room. Seems that most of the music I listen to, has bass that rolls off similarly as my subs do anyway and even a hint of anything reaching down to 20 Hz goes a long way in my home.

Actually, it was these same sealed (DIY versions, at that) subs that prompted me to make the bassline topic in the Musical Goodness section of this forum because I was suddenly more aware of it in songs that I had been listening to for over 40 years. At any rate, it has added another addictive layer to my music listening.

Not arguing either for or against ported, or even having a preference, but the fact that I was able to fit two reasonably sized sealed subs instead of not fitting even a single ported 12" or 15" is more the truth of the choice.

It also helps, in my case, because I had been perfectly fine with large, full-range, 3-way speakers, that could play into the mid, or even lower 30hz range. Those had never left me yearning for lower bass.

 

[TLS Guy]

I am using Dirac Live plus Bass Control running on a Marantz AV10. Previously, I had run in one corner of my room two SVS Ultra 13 cylinders, in the ported mode (lowest frequency configuration). These were supplemented with three Klipsch THX subwoofers stacked in the other corner. Because of all those corner and proximity effects, the cones were barely moving (for example, the SVS were adjusted down 35 dB). So, a restless 'Audioholic', I decided to try sealed. In went the foam plugs into all of the SVS's three ports. And foam into the slot loaded ducts of the Klipsch. Wow, do I like the sealed sound, though the overall frequency response measured by REW is not that different. I guess I have ears for time domain and ringing. One surprising thing, after many adjustments, was that the sub 20 htz response was improved. The sound for classical and acoustic jazz is to die for, everything else is fine too.
Here's the latest REW measurement. Any thoughts?View attachment 73738

Taking a ported sub and sealing the ports makes a sealed sub, but a bad one. There are two reasons. A good driver for ported, and a good one for sealed, have different Thiele/Small parameters as a rule. The much bigger reason is that the box alignment for the same driver sealed and ported is completely different, with the sealed alignment requiring a much smaller box volume than the ported alignment. So what you have done is way suboptimal.

The other misconception is people think that sealed alignments are not resonant, or aperiodic as we call it, but they are not. Actually many sealed designs actually do show the resonance of the alignment with a peaking of output before the second order roll off.

So as with all speakers, the quality is very much dependent on the total design, and clumsy alignments like yours are not to be recommended.

 

[ski2xblack]

Valid critique, Doc. I was hoping you could explain in more detail for the OP's specific situation.

...the box alignment for the same driver sealed and ported is completely different, with the sealed alignment requiring a much smaller box volume than the ported alignment.

In his case, assuming his subs drivers and cabs were intended/optimized for ported use, the cab volume would be too large for the drivers when sealed. How would you expect that to model, or measure? I realize that you won't be able to specifically model the situation, but the OP might appreciate some fleshing out of your criticism.

(Also for my own edification...IME, one can get away with a bit more design "clumsiness" with sealed alignments, particularly when the volume is too large rather than too small. Also, many reputable sub brands tout variable tuning, and it seems like they wouldn't do so if it pushed performance too far into the "clumsy, suboptimal" zone.)

 

[TLS Guy]

Valid critique, Doc. I was hoping you could explain in more detail for the OP's specific situation.

In his case, assuming his subs drivers and cabs were intended/optimized for ported use, the cab volume would be too large for the drivers when sealed. How would you expect that to model, or measure? I realize that you won't be able to specifically model the situation, but the OP might appreciate some fleshing out of your criticism.

(Also for my own edification...IME, one can get away with a bit more design "clumsiness" with sealed alignments, particularly when the volume is too large rather than too small. Also, many reputable sub brands tout variable tuning, and it seems like they wouldn't do so if it pushed performance too far into the "clumsy, suboptimal" zone.)

Well, one thing is certain, F3 will increase. Also the enclosure will be severely underdamped. A vented enclosure has light damping. It is usual to damp 50% of the walls of a vented cabinet for initial evaluation. A sealed enclosure on the other hand requires heavy internal damping, otherwise you have an internal box resonance and a 'honk' of varying severity depending on the frequency and severity of the resonance.

Without running a model on the actual situation it is not possible to be precise, but bass output will be reduced over all, F3 will be higher and more than likely there will be unwanted resonances above F3. The other issue is that the cone movements will not be controlled. In a ported design at, and around tuning, the pressures in the cabinet are very high, and cone movement reduced and you get the two impedance peaks with the tuning frequency at the null between them. So this really limits cone excursion, as the design is a true acoustic transformer.

Now in a sealed enclosure the cone excursion is controlled purely by the pressure generated by pistonic movement of the cone. Obviously if you have an enclosure that is too large for sealed alignment then the cone excursions are not correctly controlled.