Sealed vs. Ported Subwoofer Enclosures in Pro Audio

Bennett Prescott

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

This might be a dumb question, but why isn't sealed enclosures more popular in pro audio?

The newest top level drivers from several manufacturers in a sealed box would probably outperform older vented boxes, and sound better as well.
Hey Helge,

I started a new thread with this post because I think it's both an interesting question and a departure from the thread it was in.

Off the top of my head, I imagine it has a lot to do with the marketplace. We can already make it to 30Hz with an 18", and achieve great sound quality and output. A sealed box would offer a slower rolloff and better excursion control, but below 30Hz where more or less it isn't needed. Engineers also expect to hear the bump in output at the bottom of the sub's range, subwoofers with a lower Q sound have more or less gone out of style.

Maybe some folks who actually know something about enclosures, unlike me, will have more to say.
 

Glenn Adams

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

I am sure my comment will bring out the long knives but so what. You don't even need the box if you can tour with a baffle large enough.

Over my years using subs, from Martins bins, to W's both ported or not, and just about every ported design in between, I can only say that the port helps design a bigger sounding box with a smaller box.
That is more low end from smaller enclosures. ( and yes I know the boost is only at a certain band for frequencies that the port is tuned to and the rest of the level is about the same ported or not).

But take Danley subs that merge the back wave with the front wave to gain the most efficiency from every watt. Can't match that with a sealed system.

PS- I always liked the throw from the Martin bin. Or should I say "Punch"
 
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John Roberts

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

This might be a dumb question, but why isn't sealed enclosures more popular in pro audio?

The newest top level drivers from several manufacturers in a sealed box would probably outperform older vented boxes, and sound better as well.
I am not the speaker expert here, but generally all things equal, a ported cabinet will go lower frequency for the same cost. This as an attractive marketing hook. As there is no free lunch in physics this extended response comes with the expense of faster roll-off below, etc.

While anecdotal, I asked Rudy Bozak (RIP), of that Bozak speaker company, that I had the pleasure of consulting for decades ago, why he didn't put a port in his biggest speaker system for the extra LF output, and he answered because it just doesn't sound right with classical music. Hifi playback has numerous intrinsic flaws to start with and I do not have an objective theory to explain his preference, but I trust his ears on the subject.

FWIW, people do not listen to classical music on big PA cabinets and the concert audience is generally more impressed by SPL than signal integrity.

JR
 
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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

I'm not a speaker guru myself, but I've build some boxes and listened to a lot of different systems over the years. For some reason I've always preferred the sound of a horn sub over a vented one, I still have six labhorns that I'm not able to use anymore.
I've had limited experience with sealed subs, but I completed my first one last week and instantly liked the sound of it, it was really close to some of the best horn designs I like.

This got me thinking, are the new SOTA top boxes leaving subwoofers behind in terms of audio quality?
I used to own Danley SH-50 and I always preferred the sound of them+labsubs compared to other subs I tried.
 

John Roberts

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

This got me thinking, are the new SOTA top boxes leaving subwoofers behind in terms of audio quality?
I used to own Danley SH-50 and I always preferred the sound of them+labsubs compared to other subs I tried.
I am a fan of the Danley stuff, but in R&R it's often just a SPL competition, and worse than that, some experienced users are so accustomed to typical low bass box/driver distortion that they perceive the lack of that distortion in a clean system as somehow lacking. :-(

I worry today that kids are so accustomed to LF clipping (fart bass) that they may think that is normal.

JR

PS: Rudy agreed with you about sealed boxes. Maybe a speaker expert will chime in but I suspect there may be some differences in the phase response at and below port tuning vs sealed boxes. Should be subtle but could matter in specific circumstances. Speaker amplitude response is measured with continuous tones, while music starts and stops so YMMV.
 

Phil Graham

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

This might be a dumb question, but why isn't sealed enclosures more popular in pro audio?
The port in a box acts as a second radiator, and a radiator with an amount of gain. They are a straightforward way of reducing the excursion of a driver, while providing additional acoustic output, at the bottom end of the passband where drivers need the most help. For a long time the performance of Helmholtz resonators (i.e. ports) was linear enough that they supplemented the output of drivers without too much fuss. The case for ports is pretty easy to make with five minutes fiddling around with Theile Small parameters.

Now the drivers are displacing enough air that ports are starting to be the long pole in the tent, performance wise. The need to be bigger, and more aerodynamic, to continue to keep pace. The challenge to this is that the mechanics of a fluid exiting and opening and entering the same opening are totally different. So ports need to be a compromise between helping air enter the port and exit the port.

The alternative is to make folded horns. In a horn the pressures are high near the throat, but the volume velocity is low, so this tends to help minimize the effects of turbulence in the air around the folds, at least near the throat. As one nears the mouth the pressure becomes lower and the volume velocity grows higher. Folded horns, too, eventually end up with problems of air turbulence in the vicinity of their bends.

One could argue that a sealed box is immune to these effects, but then you've got the nonlinearities of a loudspeaker that needs to move through more displacement for the same output. Also, air itself starts to experience nonlinear compliance behavior at high volumes, so even the air "spring" behind the driver in a sealed box is not as linear as we would hope. Sealed boxes also lack a way to dissipate the substantial heat generated by the driver's motor structure, at least in the conventional "cone out" mounting configuration.

There are always compromises in play, success lies in the skill of navigating them.
 
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Bennett Prescott

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

:)

Are there any drivers in your range you would recommend for a sealed box?
Helge,

Seems that whatever has the stiffest suspension, most Xvar, and strongest motor would be the best candidate. So 18SW115? I mean, I recommend it for everything, so maybe I'm wrong but I've seen good results in every box type.
 
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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

Helge,

Seems that whatever has the stiffest suspension, most Xvar, and strongest motor would be the best candidate. So 18SW115? I mean, I recommend it for everything, so maybe I'm wrong but I've seen good results in every box type.
A quick run through WinISD. Seems like a loss of about 5 dB for a sealed box compared to a vented one. Would have been really fun trying to design and build one.

Edit: Both simulations are with two drivers in each box.
 

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Chris Greco

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

I am sure my comment will bring out the long knives but so what. You don't even need the box if you can tour with a baffle large enough.

Over my years using subs, from Martins bins, to W's both ported or not, and just about every ported design in between, I can only say that the port helps design a bigger sounding box with a smaller box.
That is more low end from smaller enclosures. ( and yes I know the boost is only at a certain band for frequencies that the port is tuned to and the rest of the level is about the same ported or not).

But take Danley subs that merge the back wave with the front wave to gain the most efficiency from every watt. Can't match that with a sealed system.

PS- I always liked the throw from the Martin bin. Or should I say "Punch"
Hey Glen, if you really like those older Martins I have 2 x S2 and 4 x S1's collecting dust in my shop :twisted:
 

Peter Morris

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May 8, 2011
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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

A quick run through WinISD. Seems like a loss of about 5 dB for a sealed box compared to a vented one. Would have been really fun trying to design and build one.

Edit: Both simulations are with two drivers in each box.

This is the reason ... 5dB for free, although the sealed box technically has more desirable acoustic properties. You also need to have a look at the cone displacement and the reason will be more apparent.
 

Peter Morris

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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

:)

Are there any drivers in your range you would recommend for a sealed box?
As a rough rule of thumb only, dividing FS by Qes (EBP) can be used as a guide to determine what type of enclosure is best for a speaker.
Around 100 - ported enclosure.
Around 50 - sealed enclosure.
50-100 may work with either
18SW115 – Fs 32 /Qes 0.32 = 100
 

Peter Morris

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May 8, 2011
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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

I am a fan of the Danley stuff, but in R&R it's often just a SPL competition, and worse than that, some experienced users are so accustomed to typical low bass box/driver distortion that they perceive the lack of that distortion in a clean system as somehow lacking. :-(

I worry today that kids are so accustomed to LF clipping (fart bass) that they may think that is normal.

JR

PS: Rudy agreed with you about sealed boxes. Maybe a speaker expert will chime in but I suspect there may be some differences in the phase response at and below port tuning vs sealed boxes. Should be subtle but could matter in specific circumstances. Speaker amplitude response is measured with continuous tones, while music starts and stops so YMMV.
A seal box is a 2[SUP]nd[/SUP] order system, ported boxes are 4th order. Accordingly the phase and impulse response of the seal box is better. The price is LF efficiency.
 
Jan 19, 2011
898
24
18
39
Oslo, Norway, Norway
drbentsen.no
Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

As a rough rule of thumb only, dividing FS by Qes (EBP) can be used as a guide to determine what type of enclosure is best for a speaker.
Around 100 - ported enclosure.
Around 50 - sealed enclosure.
50-100 may work with either
18SW115 – Fs 32 /Qes 0.32 = 100
Using your rule of thumb, I made this spread sheet.

Now, considering all things else being equal, the b&c 18PS100 is the one most suited for a sealed enclosure.
But if you use Xmax as a decider, it's a close race between 18Sound 18TLW3000 and b&c 18TBW100, 18NBX100, 18SW100.

I'll have to run them through WinISD and see :)
 

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Glenn Adams

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Feb 3, 2014
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Re: Sealed vs. Ported Subwoofer Enclosures in Pro Audio

Yes, thus the market success of ported LF cabinets. More SPL/$ ignoring the tradeoffs, which most customers are willing to do.

JR
Thankful no one mentioned passive radiator designs. Doh!