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#363177 - 01/09/12 03:27 PM Sealed vs Vented Subs...and impact
Nick B Offline
devotee

Registered: 08/05/06
Posts: 496
I have a couple of questions about subs, that I haven't been able to find answers to.

1. With all things being equal, what is the difference between a sealed and vented design?

This question comes to mind especially when looking at the Rythmik line of subs. They have vented and ported designs with the same 15" driver and amp. Many have claimed that sealed designs are better for music and more detailed. On the other hand, vented designs are said to have "group delay", where the bass signal has a slight delay, when it is played, which slightly muddy's things up. But, maybe a positive side effect (for say, explosions in a movie scene) is that the vented design may be perceived as louder at the same volume level, because of this slight delay. So if two subs are basically equal in frequency response, up until the subs hit their limit, will these things be apparent? Has there been any blind (double or single) testing done to show that "group delay" is actually something noticeable during different pieces of music or movie passages? Are there any other differences between sealed and vented subs, that show up in the listening experience.

2. What factor contributes to impact in a movie scene?

What I mean is that if you have two different subs level matched, playing within their limits in the room, with very similar flat frequency response curves (from say 20Hz to 80Hz), is one sub going to have more of an impact (thump you in the chest bass in action movies) than the other? Does a larger driver (or sum or areas of drivers, if there are two drivers) play a factor in this? Or, does sealed vs. vented design play a factor? Does the volume of the box, play a factor? Or does the amount of RMS wattage that of the amp play a factor? Or, is there anything else that plays a factor?


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#363179 - 01/09/12 04:02 PM Re: Sealed vs Vented Subs...and impact [Re: Nick B]
J. B. Offline
connoisseur

Registered: 01/19/11
Posts: 1271
Loc: Quebec, Canada
subs, and other kinds of speakers, are ALWAYS compromises in every facet you can think of.
you would learn a lot by reading reviews in some specialized sites.
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#363190 - 01/09/12 06:19 PM Re: Sealed vs Vented Subs...and impact [Re: J. B.]
nickbuol Offline
connoisseur

Registered: 09/16/04
Posts: 4515
Loc: Marion, IA
From my (limited) knowledge on the subject, yes, a sealed design (if all other factors are equal) will yield tighter bass as people call it. So what about all of the ported subs? Well, sound travels through a medium (air in this case) and the more air you can move, the more "bass" you can get. A port allows for more air movement.

You will also hear people "tuning" their subs for even lower frequencies by messing with port sizes/lengths. With a sealed box, it would seem that things are a little more limited.

I am probably 200% wrong, but that is what I used when I built a sub box for my car years ago. I wanted the tight bass and not massive bass (I wanted to add to the music, not dominate the music) so I went sealed.

Home theater, to me, is a different story, and I like ported better.
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#363196 - 01/09/12 07:30 PM Re: Sealed vs Vented Subs...and impact [Re: Nick B]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 7139
Loc: Canada
Originally Posted By: Nick B
I have a couple of questions about subs, that I haven't been able to find answers to.

1. With all things being equal, what is the difference between a sealed and vented design?


One is sealed, the other vented. Really.

There is a lot of myth in the sealed vs. vented debate. How well a sub reproduces a given frequency is a direct result of the quality of parts and the quality of the design.

Where sealed subs are damped by the sealed internal air mass, a (good) vented sub relies on motor strength to start and stop the driver properly to accurately reproduce sound.

Because of the way a sealed sub rolls off gradually, it will often require some equalization (either a cut in higher frequencies, and/or a boost in lower frequencies) to give flat output across its range.

A vented sub will require a high pass filter to keep frequencies below its optimal range from destroying the driver (no natural damping as with a sealed design).

A driver designed for use in sealed enclosures will not work as well in a vented design and vice versa.

As for group delay, there are well known and respected designers on both sides of that argument and you can find some interesting discussions on avsforum.com and diyaudio.com where both sides duke it out.

Originally Posted By: Nick B

What I mean is that if you have two different subs level matched, playing within their limits in the room, with very similar flat frequency response curves (from say 20Hz to 80Hz), is one sub going to have more of an impact (thump you in the chest bass in action movies) than the other?

Nope.

Originally Posted By: Nick B

Does the volume of the box, play a factor? Or does the amount of RMS wattage that of the amp play a factor?

Yes and yes. In general, you will need more power with a sealed design than ported to produce the same volume and range of sound. A lot depends on driver design and efficiency as well though.

Also, ported systems need internal volume to reproduce those extended lower notes so they tend to be bigger, often bigger than your average person wants.

If you want the point made with real examples go to the diy subs and speakers sub-forum at avsforum.com and search for a thread by bossobass on his dual opposed 15" sealed sub design. It is very compact and fed by something like 4,000 watts of power to produce incredible bass from 10Hz on up.

Then search for a thread on the wolfhorn a 'ported' (well horn loaded actually) design at the other end of the spectrum. It produces the same bass with a fraction of the power, but is, um, quite large.

If you skipped all the way to the bottom to see if I had a point grin , you can get similarly good (sic) bass from either design, just in different ways.
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-------
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#363197 - 01/09/12 07:39 PM Re: Sealed vs Vented Subs...and impact [Re: fredk]
tomtuttle Offline
axiomite

Registered: 06/20/03
Posts: 8294
Loc: Tacoma
Excellent post, Fred.
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#363200 - 01/09/12 08:14 PM Re: Sealed vs Vented Subs...and impact [Re: Nick B]
casey01 Offline
aficionado

Registered: 07/03/08
Posts: 768
Loc: Toronto
Originally Posted By: Nick B
I have a couple of questions about subs, that I haven't been able to find answers to.

1. With all things being equal, what is the difference between a sealed and vented design?

This question comes to mind especially when looking at the Rythmik line of subs. They have vented and ported designs with the same 15" driver and amp. Many have claimed that sealed designs are better for music and more detailed. On the other hand, vented designs are said to have "group delay", where the bass signal has a slight delay, when it is played, which slightly muddy's things up. But, maybe a positive side effect (for say, explosions in a movie scene) is that the vented design may be perceived as louder at the same volume level, because of this slight delay. So if two subs are basically equal in frequency response, up until the subs hit their limit, will these things be apparent? Has there been any blind (double or single) testing done to show that "group delay" is actually something noticeable during different pieces of music or movie passages? Are there any other differences between sealed and vented subs, that show up in the listening experience.

2. What factor contributes to impact in a movie scene?

What I mean is that if you have two different subs level matched, playing within their limits in the room, with very similar flat frequency response curves (from say 20Hz to 80Hz), is one sub going to have more of an impact (thump you in the chest bass in action movies) than the other? Does a larger driver (or sum or areas of drivers, if there are two drivers) play a factor in this? Or, does sealed vs. vented design play a factor? Does the volume of the box, play a factor? Or does the amount of RMS wattage that of the amp play a factor? Or, is there anything else that plays a factor?


Quite frankly, in my experience, this design difference between the two types and what some perceive as being preferential for movies or music or visa versa, I believe is highly overblown. In my case, I have both types in my system(FOUR total) and either works for any type of sound coming through it equally well. With a multiple sub arrangement especially, as long as they are relatively close in power capabilities and frequency range along with being phased and balanced properly, it won't really matter what type of sub it might be. Room interaction will have a much greater affect on what you are hearing and getting it right than the design characteristics.

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#363204 - 01/09/12 08:52 PM Re: Sealed vs Vented Subs...and impact [Re: fredk]
CatBrat Offline
axiomite

Registered: 08/05/09
Posts: 5912
Loc: Milky Way Galaxy
Originally Posted By: fredk
If you skipped all the way to the bottom to see if I had a point grin , you can get similarly good (sic) bass from either design, just in different ways.


Aha. I knew I didn't have to read the whole thing. smile

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#363221 - 01/09/12 10:54 PM Re: Sealed vs Vented Subs...and impact [Re: CatBrat]
tomtuttle Offline
axiomite

Registered: 06/20/03
Posts: 8294
Loc: Tacoma
casey, that's exactly the kind of well-reasoned, first-hand feedback that I find valuable, and that I think is a signature element of the Axiom forum. It is also the sort of thing that will get you torched at AVS.
_________________________
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#363263 - 01/10/12 01:30 PM Re: Sealed vs Vented Subs...and impact [Re: fredk]
Nick B Offline
devotee

Registered: 08/05/06
Posts: 496
Originally Posted By: fredk


Originally Posted By: Nick B

What I mean is that if you have two different subs level matched, playing within their limits in the room, with very similar flat frequency response curves (from say 20Hz to 80Hz), is one sub going to have more of an impact (thump you in the chest bass in action movies) than the other?

Nope.



So if you locate the best place in a small room (say 12 ft by 17 ft with 8 ft ceilings) for the EP800 and level match it with the rest of the speakers. Place an EP400 on top of the EP800 and level match it to the rest of the speakers. Have an external EQ, trim the bass of the EP800 below 20Hz, so that it has the same frequency response as the EP400. Then you will not notice the difference (in terms of the amount of tactile bass and impact of it) between the two if you A/B them on heavy bass scenes, like chapter 4 of Master and Commander, or the the bridge of khazad dum in the Fellowship of the Rings, for example?

Originally Posted By: casey01

In my case, I have both types in my system(FOUR total) and either works for any type of sound coming through it equally well. With a multiple sub arrangement especially, as long as they are relatively close in power capabilities and frequency range along with being phased and balanced properly, it won't really matter what type of sub it might be. Room interaction will have a much greater affect on what you are hearing and getting it right than the design characteristics.


What subs do you have that are sealed and ported? You have two of each design integrated at the same time in the same room? Are you saying that you have done an A/B comparison of both of the sealed and ported subs in your room and didn't really notice a difference?


Again, this question came to me when looking at the Rythmik line of subwoofers. They have a 15" sub in either a sealed or ported design with what seems like the same driver and amp and just about the same price. The ported design has a slightly larger cabinet. For a few hundred dollars more they have a sealed sub using two of those same drivers (at least they seem to be from as far as I can tell) the same amp and obviously a larger cabinet to fit the two drivers. So for almost the same money you can have three very different subwoofers, in terms of the design. I'm just confused as to what the difference would be between these. The only obvious difference that I can see is that the one with two drivers is probably more capable in a larger room, due to the amount of air that it can move in comparison with the other two.

Axiom has a slightly similar offering. The EP600 and EP800 are nearly the same size cabinet. The 600 has one 12" driver and is ported. The 800 has two drivers and is sealed. The frequency response curves look very similar (the 800 playing slightly lower), so do they sound identical with those same from 20Hz to 80Hz, if they are playing within their limits?

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#363308 - 01/10/12 03:57 PM Re: Sealed vs Vented Subs...and impact [Re: Nick B]
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3191
Loc: Toronto/New York/Dwight
In my listening tests of subs at Axiom (not nearly as elaborate or extended as listening tests of other Axiom speakers), I'd say yes, the 800 and 600 do not differ in a qualitative sense. That is, I don't write down on the rating sheet stuff like, "Oh, it's obviously a sealed sub!" Or "something tells me this is a ported subwoofer".

"Tactile impact" from subwoofers is a product of extension and output capability. The reason Ian made the 800 a sealed design with two drivers (as opposed to the ported 600 with one driver) was to offer deeper bass extension without port noise that would otherwise intrude at very low frequencies from a vented design, and also to increase the overall output.

Remember that with a sealed design, you are "throwing away" all the back energy from the driver, so you have to have larger amplifiers or double up on drivers to achieve the same SPL that could be obtained from a ported single-driver design, other things being equal.

The comparison you mention, with the 400 on top of an 800, is kind of specious, at least in a large room. The 400 was designed for deep bass extension in a small room, so it isn't capable of the same SPL as the larger EP800. If tactile impact were the criterion, the EP800 would win, simply because of its greater output capability.

Regards,
Alan
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Axiom Resident Expert

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