Hello,
What's better between the two:
Acoustic suspension (sealed enclosure) or bass reflex (vented enclosure) in terms of sound?
I see currently only bass reflex enclosures in the shops, but this not necessarily means that they are better than sealed box.
There are other features such as dimensions, for example, that weigh on the purchase.
Assuming you have no dimensions limits,which type of enclosure would you buy/build in order to achieve good sound results?
Thanks for any feedback
What's better between the two:
Acoustic suspension (sealed enclosure) or bass reflex (vented enclosure) in terms of sound?
I see currently only bass reflex enclosures in the shops, but this not necessarily means that they are better than sealed box.
There are other features such as dimensions, for example, that weigh on the purchase.
Assuming you have no dimensions limits,which type of enclosure would you buy/build in order to achieve good sound results?
Thanks for any feedback
There are too many factors involved to really say which is better. Actually I recently saw an article in The Absolute Sound talking about Subwoofer design inwhich they claimed the superiority of Acoustic Suspension, suggesting that the only reason to use bass reflex is to get lower boomy bass. I disagree, but unfortunatly this is the sort of myths perpetuated in the media, and its also a result of many poorly designed speakers.
A sealed speaker has the benefit of an air suspension, or cushion that aids in controlling the movement of the cone. You make see, as a result, lower distortion and greater control of the cone in a sealed box. You see a shallower rolloff in the bass, which means that, though the -3db point will be higher up, it will still, potentially be producing bass deeper down. For instance you may see a lower -10 db point than with an equivelant ported box. Sealed boxes are generally able to be made smaller as well. However they are generally less efficient, some of this having to do with what it takes to make a driver have deep bass in a sealed enclosure, so TS perameters, and some of it is simply what happens in an acoustic suspension.
Ported boxes on the other hand can be made to extend down deeper at the -3db point, can can often be tuned, in the case of subwoofers, so low that the -10db point is still lower in frequency than the sealed box, especially when using a bass shelf. However, to achieve this, given that a speaker has T/S specs that allow it to work equally well in either box, the ported box will likely be much larger, as much as twice as large is not uncommon, and at least 50% bigger in my own experience. One problem I see is that, because consumers don't like large boxes, a lot of speakers have portes boxes that are too small, with the port tuning too high, causing a rise in the low end, which makes for boomy bass. It gives the perception of greater bass, but the reality is that this is a coloration in the sound. All too many ported speakers are not tuned properly. Oh yes, and generally ported boxes are more efficient than sealed boxes.
As for the claim that a sealed box has lower distortion and a better transient response, in general that can be seen as true, but its not always true. Also, you have the arguement of, is it audible, and is the effect of greater importance than other factors. Overdampened sealed systems can give things like drums an unrealisticly tight sound, lacking the natural decay that a drum has. The use of servo's in ported boxes allows for better transient response and the better extension that a ported box gives, but these systems are rare. However, the better more linear motors being used in a lot of todays subs also allows for a much better transient response. For example, the new RS line of subs from Parts Express Dayton have excellent transient response in ported boxes, though not quite as good as that of the sealed version, the benefit of greater bass extension more than makes up for the almost imperceptable change in transient response. Getting a sealed sub to play flat down to 20hz or so, even 25hz requires equilization. In TAS, they acted like the Linkwitz Transform cuircit is a miracle cuircit that negates the the benefit of deeper bass from a ported box. However, they forgot that it requires more power and excursion than pretty much any woofer made. Using the JL Audio W7, which has near 30mm of xmax, one of the highest in the industry, along with a very high power handeling level. This is a speaker that you would think could do as well as any with the linkwitz cuircit, and in my experience it does very well. However, it still requires over 3000 watts and will exceed xmax in order to be flat down to 20hz. This really isn't a major issue in the real world, as its rare that you need a 20 or even 25hz tone to be as loud as a 35hz or 55hz tone, very little material is down there, none the less, it shows the massive difference in efficiency between a ported and sealed box in the lowest end of their extension, the sealed box needing much more power and excursion to achieve the same extension. In this scenerio, more than any amp could reasonably supply, or any speaker could reasonably handle.
All of that is true of subs, and much of it carries over to regular full range speakers, but when dealing with things like midbass drivers and such, it becomes more what the speaker will work in best. It's still important to tune everything correctly, a midbass driver in an overdampened enclosure will give an unrealistic sound to deeper male voices, drums, piano, the bass, etc. A ported box with a tipped up bottom end can sound boomy and loose. I've always prefered the midrange from cone drivers that are in open systems, such as ported, open baffle, resistive vent-aperiodic, etc.
A sealed speaker has the benefit of an air suspension, or cushion that aids in controlling the movement of the cone. You make see, as a result, lower distortion and greater control of the cone in a sealed box. You see a shallower rolloff in the bass, which means that, though the -3db point will be higher up, it will still, potentially be producing bass deeper down. For instance you may see a lower -10 db point than with an equivelant ported box. Sealed boxes are generally able to be made smaller as well. However they are generally less efficient, some of this having to do with what it takes to make a driver have deep bass in a sealed enclosure, so TS perameters, and some of it is simply what happens in an acoustic suspension.
Ported boxes on the other hand can be made to extend down deeper at the -3db point, can can often be tuned, in the case of subwoofers, so low that the -10db point is still lower in frequency than the sealed box, especially when using a bass shelf. However, to achieve this, given that a speaker has T/S specs that allow it to work equally well in either box, the ported box will likely be much larger, as much as twice as large is not uncommon, and at least 50% bigger in my own experience. One problem I see is that, because consumers don't like large boxes, a lot of speakers have portes boxes that are too small, with the port tuning too high, causing a rise in the low end, which makes for boomy bass. It gives the perception of greater bass, but the reality is that this is a coloration in the sound. All too many ported speakers are not tuned properly. Oh yes, and generally ported boxes are more efficient than sealed boxes.
As for the claim that a sealed box has lower distortion and a better transient response, in general that can be seen as true, but its not always true. Also, you have the arguement of, is it audible, and is the effect of greater importance than other factors. Overdampened sealed systems can give things like drums an unrealisticly tight sound, lacking the natural decay that a drum has. The use of servo's in ported boxes allows for better transient response and the better extension that a ported box gives, but these systems are rare. However, the better more linear motors being used in a lot of todays subs also allows for a much better transient response. For example, the new RS line of subs from Parts Express Dayton have excellent transient response in ported boxes, though not quite as good as that of the sealed version, the benefit of greater bass extension more than makes up for the almost imperceptable change in transient response. Getting a sealed sub to play flat down to 20hz or so, even 25hz requires equilization. In TAS, they acted like the Linkwitz Transform cuircit is a miracle cuircit that negates the the benefit of deeper bass from a ported box. However, they forgot that it requires more power and excursion than pretty much any woofer made. Using the JL Audio W7, which has near 30mm of xmax, one of the highest in the industry, along with a very high power handeling level. This is a speaker that you would think could do as well as any with the linkwitz cuircit, and in my experience it does very well. However, it still requires over 3000 watts and will exceed xmax in order to be flat down to 20hz. This really isn't a major issue in the real world, as its rare that you need a 20 or even 25hz tone to be as loud as a 35hz or 55hz tone, very little material is down there, none the less, it shows the massive difference in efficiency between a ported and sealed box in the lowest end of their extension, the sealed box needing much more power and excursion to achieve the same extension. In this scenerio, more than any amp could reasonably supply, or any speaker could reasonably handle.
All of that is true of subs, and much of it carries over to regular full range speakers, but when dealing with things like midbass drivers and such, it becomes more what the speaker will work in best. It's still important to tune everything correctly, a midbass driver in an overdampened enclosure will give an unrealistic sound to deeper male voices, drums, piano, the bass, etc. A ported box with a tipped up bottom end can sound boomy and loose. I've always prefered the midrange from cone drivers that are in open systems, such as ported, open baffle, resistive vent-aperiodic, etc.
which one?
If it were me, I'd go with a high quality driver suitable for ported enclosure.. I've had really good luck with sonotube designs, as well as a mid-bass enclosure good to ~45 Hz using 7" peerless drivers that sounds remarkably tight (but I also have good sealed enclosures ~ 1 ft^3) with bass to below 30 Hz. the Sonotubes go down below 20 Hz with authority, though, and can be built on the cheap...
John L.
mastermosfet said:
If it were me, I'd go with a high quality driver suitable for ported enclosure.. I've had really good luck with sonotube designs, as well as a mid-bass enclosure good to ~45 Hz using 7" peerless drivers that sounds remarkably tight (but I also have good sealed enclosures ~ 1 ft^3) with bass to below 30 Hz. the Sonotubes go down below 20 Hz with authority, though, and can be built on the cheap...
John L.
Mastermosfet
Generaly speaking, bass reflex boxes are prefered on the basis of technical arguments (mainly : less cone excursion which means less harmonic distorsion and higher possible level in the bass region ) and closed boxes are prefered on the basis of subjective arguments.
I suggest you make your mind by listening to both types of boxes of similar size. Maybe not easy to find.
Generaly speaking, bass reflex boxes are prefered on the basis of technical arguments (mainly : less cone excursion which means less harmonic distorsion and higher possible level in the bass region ) and closed boxes are prefered on the basis of subjective arguments.
I suggest you make your mind by listening to both types of boxes of similar size. Maybe not easy to find.
Either done well can sound good just as either done poorly can sound bad. If you start with a quality driver with parameters optimized for a ported enclosure, than take that same driver and alter it's parameters to be optimized for a sealed box, it becomes a different driver. Point being there's really no way to make a direct comparison. It's apples and oranges. So as said above, you just have to listen and make your own choice.
To me the highest quality, or most realistic sounding is actually a Infinite baffle with a low frequency boost.
an Infinite baffle is a really big sealed box, geneally much bigger than usual, it can be 4x the drivers Vas.
Bass Reflex always has port noise issues. Ports do not maintain SPL with the driver, ie as you turn it up it hits its maximum bass fairly low on the dial, and then stays fairly constant.
Personally I like Bass Reflex, I have made many, I do think it has its positives, and there are many reasons why I use it, but ultimatly if realism and natural sound is the aim, Infinate baffle is the key, just need to boost the lowest end.
The infinate baffle will provide a smoother response in the midrange.
an Infinite baffle is a really big sealed box, geneally much bigger than usual, it can be 4x the drivers Vas.
Bass Reflex always has port noise issues. Ports do not maintain SPL with the driver, ie as you turn it up it hits its maximum bass fairly low on the dial, and then stays fairly constant.
Personally I like Bass Reflex, I have made many, I do think it has its positives, and there are many reasons why I use it, but ultimatly if realism and natural sound is the aim, Infinate baffle is the key, just need to boost the lowest end.
The infinate baffle will provide a smoother response in the midrange.
One of the more interesting aspects of ported design is the problem with unequal loading a ported system, is of the inner air pressure loading of the port vs the front pressure loading.
One trick I tried nearly 15 years ago, to help deal with this issue is of a nature, but in some ways, beyond all the recent attempts, patents, etc..is to put something like a 'flower' on the inner lip of the port. It will, or may require more solid backing that a simple cone cut alone, so consider removing all flex in that inner 'flowered cone'. A simple cut cone, will flex under loading and the flex must be eliminated. I could likely patent such an arrangement, but I dismissed such long ago and only work with sealed boxes since that time - but it may be of use to those of you who prefer ported designs.
What I mean, is to take a old exponentially flared speaker cone, and cut it so it fits over the inner end of the port. Cut it like a multi- 'winged' flower shape. This allows gradual loading of all the standing wave frequencies (pressure nodes, etc) which evolve in the inside of the box. This brings about a very interesting character to the loading which is far more even and benifical to the bass response. Give it an experimental shot, guys. see what you get. Each individal box design will require a different one, obviously.
One trick I tried nearly 15 years ago, to help deal with this issue is of a nature, but in some ways, beyond all the recent attempts, patents, etc..is to put something like a 'flower' on the inner lip of the port. It will, or may require more solid backing that a simple cone cut alone, so consider removing all flex in that inner 'flowered cone'. A simple cut cone, will flex under loading and the flex must be eliminated. I could likely patent such an arrangement
, but I dismissed such long ago and only work with sealed boxes since that time - but it may be of use to those of you who prefer ported designs.What I mean, is to take a old exponentially flared speaker cone, and cut it so it fits over the inner end of the port. Cut it like a multi- 'winged' flower shape. This allows gradual loading of all the standing wave frequencies (pressure nodes, etc) which evolve in the inside of the box. This brings about a very interesting character to the loading which is far more even and benifical to the bass response. Give it an experimental shot, guys. see what you get. Each individal box design will require a different one, obviously.
audiobomber said:
Correct. However, the port frequency can be tuned really low.
Take a 12 inch driver in a sealed enclosure.
Take another 12 inch driver in a ported enclosure tuned to 30 Hz.
Drive both so that they produce 110 dB at 30 Hz.
The driver in the ported enclosure will be moving only one quarter as far to produce that 110 dB as the driver in the sealed enclosure.
At some point, the driver in the sealed enclosure will run out of excursion-but the driver inthe ported enclosure will be able to go 12 dB higher SPL.
Yes, below 30 Hz the ported driver will begin to excurse quite a bit more than than the sealed driver. But 30 Hz is pretty low, and down to 30 Hz the ported driver has it all over the sealed driver, SPL, (volume), wise.
Of course, you can tune a ported driver lower than 30 Hz if you wish and stil get the same benefits. I just selected it because it was a common tuning frequency.
Bass is about producing SPL's with a limited excursion ability, (ability of the driver to move back and forth). A ported enclosure, down to it's tuning frequency, simply produces a much higher SPL, (volume level) in the bass for the same excursion ability of the driver.
Wow! How many replies!...
Now I'm a bit confused...
Anyway, I see all around almost exclusively bass reflex enclosures, but I'm agree with some of you about the fact that their bass are unnatural, likely "coloured", while acoustic souspension seems to be more accurate.
From my part I ask why,then, acoustic suspension speaker systems are really unfindable?
They seems to be cheaper and easier to build than Bass reflex ones...
Well,
How to get low frequency boost?
Now I'm a bit confused...
Anyway, I see all around almost exclusively bass reflex enclosures, but I'm agree with some of you about the fact that their bass are unnatural, likely "coloured", while acoustic souspension seems to be more accurate.
From my part I ask why,then, acoustic suspension speaker systems are really unfindable?
They seems to be cheaper and easier to build than Bass reflex ones...
Well,
How to get low frequency boost?
No, To get this right an acoustic suspension speaker system is a subset of the more general sealed enclosures that can be defined if the rear leaks (losses) have a very long time constant in comparison with the system cut-off frequency and the rear side features is not contributing to the system output at all.
Instead the output is solely relying on the control from the contained volume, the acoustical compliance that can take any value but for the case of acoustic suspension this volume is much more dominating than the driver compliance.
The system compliance ratio (alpha=Vas/Vb) for an acoustic suspension is typically >=4 but for a general closed box system alpha can be of any number thus a low value of box volume is selected for an acoustic suspension speaker when compared to the driver Vas volume.
b
I was not really aware that ported systems had pushed sealed systems out so completely. Time was when you could not get a ported system. Perhaps it is just the dealers in your area.
As statistics go, the bass is measured at the -3 dB down point. In other words, we consider a mediocre bass output as being -3 dB @ 50 Hz, a deep bass output as -3 dB @ 30 Hz.
A -3 dB down @50 Hz is not bad for say, a 6.5 inch woofer. For a 12 inch woofer, that would be considered pretty lackluster.
Sealed systems-whether "acoustic suspension" or not-roll off at a rate of 12 dB per octave. Ported systems roll off at the rate of 24 dB per octave-usually. So if you have a ported system and a sealed system, both -3 dB @ 50 Hz, the ported system will seem to have a little more bass, since below that 50 Hz line it will still have some hearable output. The ported system will not have hearable output below 50 Hz.
However, for advertising puposes, the ported and the sealed will seem to be the same if they have the same -3 dB down point. And the ported enclosure will be considerably smaller if both enclosures have the same -3 db down point.
So when the consumer goes shopping, he sees a sealed unit of 28 liters, and a ported unit of 14 or 15 liters, and they both have a -3 dB down point of 50 Hz. The consumer will seem to be instantly drawn to the smaller unit which seems to have "equal" bass to the larger unit.
That is one reason.
As statistics go, the bass is measured at the -3 dB down point. In other words, we consider a mediocre bass output as being -3 dB @ 50 Hz, a deep bass output as -3 dB @ 30 Hz.
A -3 dB down @50 Hz is not bad for say, a 6.5 inch woofer. For a 12 inch woofer, that would be considered pretty lackluster.
Sealed systems-whether "acoustic suspension" or not-roll off at a rate of 12 dB per octave. Ported systems roll off at the rate of 24 dB per octave-usually. So if you have a ported system and a sealed system, both -3 dB @ 50 Hz, the ported system will seem to have a little more bass, since below that 50 Hz line it will still have some hearable output. The ported system will not have hearable output below 50 Hz.
However, for advertising puposes, the ported and the sealed will seem to be the same if they have the same -3 dB down point. And the ported enclosure will be considerably smaller if both enclosures have the same -3 db down point.
So when the consumer goes shopping, he sees a sealed unit of 28 liters, and a ported unit of 14 or 15 liters, and they both have a -3 dB down point of 50 Hz. The consumer will seem to be instantly drawn to the smaller unit which seems to have "equal" bass to the larger unit.
That is one reason.
Sorry I tuned out and missed the question.
My personal experience of this was in a cinema that I designed and custom built the speakers for. The boost was from a 1/3 octave equalizer within the dolby processor , so simply a 6 db boost at 32 hz.
I would assume that a cheap kit from an electronics shop would do the same thing bass extender
Boosts are also found in some plate sub amplifiers.
Its simply a compromise of quality verses efficiecy. If you like music which features the Double Bass, the difference is noticable. to me its sounds more natural.
Easiest way would be to design a large bass reflex box, listen to the results, temporarily seal the port, boost the sub bass electronically, and then decide for yourself.
pjpoes said:
Omigosh! I agree with TAS! In about 95% of cases with BR boxes they're correct. In most cases, the boxes are mis-aligned and you don't really have a good connection between the Helmholtz resonator and the driver (ie. if the driver doesn't 'almost' stop movement at some point, then there's not a really good coupling). This is when you start to get boominess. It's louder, but it doesn't sound like an instrument, just noise. I'm not sure that EQ'd sealed enclosures sound much better (apologies to Linkwitz). Basically, there's not substitute for cubic inches...IMHO
kelticwizard said:
Oh no!, my 12 inch boxes are -3dB at 50Hz, -12dB at 20Hz, -21dB at 10Hz.
_ 
oh come now, plenty of 6.5" woofers can do a -3db at 50hz, and with plenty of output. In a ported enclosure anyway, hehe. In a sealed box, I tried modeling some and had trouble, I think the Extemis was the only one that did, and in a very large box.
Only going with subwoofers for the moment, a ported box is more efficient than a sealed box in the low bass. Taking my own Dayton case in point, the Dayton has an F3 of around 47hz, and thus rolls off at 12db's per octave, the ported system will be 12db's per octave more efficient below the point the sealed system starts rolling off. Also, that isn't completely accurate in that the ported system isn't even rolling off at all until 20hz, which is what, about 1 octace down, a little more.
TAS is not right I'm sorry, and I'm currently putting together a test rig to prove my own point. However, there are many far more knowledgable than I that already could not only argue, but show with graphs how what they say isn't so. I currently have in my hands two 12" dayton Refrence subs, one in a 2.5 cubic foot sealed enclosure, with an F3 of 37hz, and the same woofer in a 4.5 Cubic foot enclosure tuned to 21hz, and an F3 of 19hz. I have some preliminary measurements, but I'm still calibrating everything. Even using my ol' RS digital meter modified for a flatter response, and using the associated correction factor, I still have at 1 watt a 2db increase in efficiency from the ported system. Also, Running it outside and doing my measurements as close to free air as I can, same as Stereophile does, my Impulse response from 19hz to 45hz is better on the ported system than on the sealed system. That overhang they show on the ported system has more in common with what I'm seeing from my sealed box. So far distortion measurements are showing it to have as much as 20% less distortion in the very low end, and I calculate quickly an average of 5% better. The only place the sealed system is showing better impulse response, better distortion, and otherwise identical measurements is from 45hz on up. Also, my focal based main speakers have a better measured response, including impulse response, from its low end, an F3 of 42hz on up. Though I actually cross the sub over at closer to 60hz as I prefer the transition, I still feel that designed right, the ported box is the better choice here.
I also think its unfair to characterize a design by the misuse of the design by many manufacturers. Even if you want to use the ol' if it was better everyone would be doing it, look at the majority of high end speakers. In the bass area, most seem to still be going with ported enclosures, rather than sealed enclosures. I know, not 100%, and there are ways to make the sealed boxes perform great, but I still see them preferring ported as a whole.
Only going with subwoofers for the moment, a ported box is more efficient than a sealed box in the low bass. Taking my own Dayton case in point, the Dayton has an F3 of around 47hz, and thus rolls off at 12db's per octave, the ported system will be 12db's per octave more efficient below the point the sealed system starts rolling off. Also, that isn't completely accurate in that the ported system isn't even rolling off at all until 20hz, which is what, about 1 octace down, a little more.
TAS is not right I'm sorry, and I'm currently putting together a test rig to prove my own point. However, there are many far more knowledgable than I that already could not only argue, but show with graphs how what they say isn't so. I currently have in my hands two 12" dayton Refrence subs, one in a 2.5 cubic foot sealed enclosure, with an F3 of 37hz, and the same woofer in a 4.5 Cubic foot enclosure tuned to 21hz, and an F3 of 19hz. I have some preliminary measurements, but I'm still calibrating everything. Even using my ol' RS digital meter modified for a flatter response, and using the associated correction factor, I still have at 1 watt a 2db increase in efficiency from the ported system. Also, Running it outside and doing my measurements as close to free air as I can, same as Stereophile does, my Impulse response from 19hz to 45hz is better on the ported system than on the sealed system. That overhang they show on the ported system has more in common with what I'm seeing from my sealed box. So far distortion measurements are showing it to have as much as 20% less distortion in the very low end, and I calculate quickly an average of 5% better. The only place the sealed system is showing better impulse response, better distortion, and otherwise identical measurements is from 45hz on up. Also, my focal based main speakers have a better measured response, including impulse response, from its low end, an F3 of 42hz on up. Though I actually cross the sub over at closer to 60hz as I prefer the transition, I still feel that designed right, the ported box is the better choice here.
I also think its unfair to characterize a design by the misuse of the design by many manufacturers. Even if you want to use the ol' if it was better everyone would be doing it, look at the majority of high end speakers. In the bass area, most seem to still be going with ported enclosures, rather than sealed enclosures. I know, not 100%, and there are ways to make the sealed boxes perform great, but I still see them preferring ported as a whole.
pj,pjpoes said:
I'm not trying to start a fight
, I just prefer the sound of sealed to ported. Them plucked or stroked double-bass notes just don't sound like the instrument through a hole. But that's my opinion (and I'm sticking to it !). And when it comes to efficiency, well, the Lambdas in my bass bins can handle 300w all day, and the amp that drives tham can also. I'm just looking around for a 800W-er to drive my planned subby (15" Lambdas). Something under $400Aus, because I'm cheap...he! he!
I think if you looked at my outfit with graphs, you might say it was down on bass extension. But it sure doesn't sound like it. And when we move somewhere bigger, then there will aways be the bigger sub to handle the extra bass required.
Ported does make more bass noise from a smaller box with less power. But, if you've got the power and the space then you might prefer the sound of the sealed.
Or O/B. Or T/L. Or horn. Which are all outside the scope of this thread.
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