Benefits of sealed enclosure speakers?

[paulsue38]

Considering upgrading to the new Spendor A5r speakers. They have removed the rear port from the previous A5 model. What do people consider to be the main benefits of a sealed enclosure?

Best wishes

Paul

 

[SteveR750]

Natural roll off, lack of bass humps and less likelihood of an unwanted interaction with the room, and less sensitive to positioning.

 

[CnoEvil]

Natural roll off, lack of bass humps and less likelihood of an unwanted interaction with the room, and less sensitive to positioning.

Yup.

Plus it's less sensitive to the "woofling" of the Bass Driver, that can be caused by the low frequency rumble from a TT (if that's an issue).

 

[Vladimir]

The box acts as an air spring, which helps with more accurate pistonic movement of the cone, compared to relying alone on the foam/textile/rubber surround.

For those interested to learn more google AR (Acoustic Research) and its founder Edgar Villchur.

 

[peterpiper]

my kefs are the first sealed box speakers i have owned, and the bass is still punchy but without much boom boom, impressed with them

 

[lindsayt]

The major improvement possible with sealed box speakers is better transient response in the region covered by the port.

Think about it. The pedal hitting a bass drum at the same time the strings are plucked on a bass guitar. You've got two transients with some decay. What's likely to sound more realistic? The sound of them coming off a bass cone, or the sound of them coming out of a reflex port?

Think about it a bit more. If you've got a large bass cone in a small sealed cabinet, playing loud transients, what effect is the air inside the box going to have on the cone? It's going to act like a spring and compress the transient. Put the bass cone in a huge sealed box and you don't get that spring effect. But huge size increases cost and decreases domestic acceptability. Speaker design is a series of compromises.

 

[peterpiper]

Think about it a bit more. If you've got a large bass cone in a small sealed cabinet, playing loud transients, what effect is the air inside the box going to have on the cone? It's going to act like a spring and compress the transient. Put the bass cone in a huge sealed box and you don't get that spring effect. But huge size increases cost and decreases domestic acceptability. Speaker design is a series of compromises.

I think that makes sense, and could be the reason why the likes of kef have retained a port on their bookshelf models but made their floorstanders sealed designs,

 

[paulsue38]

This probably describes what I need. I currenly have the Spendor A3 with Arcam A38 and Marantz Pearl Lite CD player. The A 3 is an amazing compact floorstander for its size, with lovely tonal qualities. However, the port arrangement, does perhaps, cause problems in my small room; with two deep alcoves and a bay window. I have to pull them right out into the room. I have introduced bass panels which have helped to extent. There is enough bass, but its not as well pronoucd as I would like. Sounds like the A5 may be ideal.

Best wishes

Paul

 

[matt49]

Think about it a bit more. If you've got a large bass cone in a small sealed cabinet, playing loud transients, what effect is the air inside the box going to have on the cone? It's going to act like a spring and compress the transient. Put the bass cone in a huge sealed box and you don't get that spring effect. But huge size increases cost and decreases domestic acceptability. Speaker design is a series of compromises.

It also reduces the stiffness and rigidity of the box leading to greater distortion because of resonances.

 

[Coll]

This probably describes what I need. I currenly have the Spendor A3 with Arcam A38 and Marantz Pearl Lite CD player. The A 3 is an amazing compact floorstander for its size, with lovely tonal qualities. However, the port arrangement, does perhaps, cause problems in my small room; with two deep alcoves and a bay window. I have to pull them right out into the room. I have introduced bass panels which have helped to extent. There is enough bass, but its not as well pronoucd as I would like. Sounds like the A5 may be ideal.

Best wishes

Paul

Basically from the same size cabinet you get more bass if it is ported. Ports on the back are always a problem if the speakers are close to the wall. Unless they are designed to be.

There is one other thing you should try before spending your money, block the ports and see how you like the sound. If there is not enough bass you either need larger sealed cabinets or a front ported design.

 

[SteveR750]

To confound things, ATC (who have a thing about low distortion) use a sealed box design for their lower cost domestic models, and ported for the bigger ones.

 

[peterpiper]

there will always be arguments for and against certain designs, its what woks best in your room,,, of the ported speakers i have owned, i always tried them with the bungs in, never liked it, yet i like the sound of the kefs, my conclusion is , you should use the speaker as it was intented in its design, if a speaker is ported it was designed to sound best like that, likewise the sealed kefs would probably sound bad with a hole drilled in the back*shok*

 

[lindsayt]

Think about it a bit more. If you've got a large bass cone in a small sealed cabinet, playing loud transients, what effect is the air inside the box going to have on the cone? It's going to act like a spring and compress the transient. Put the bass cone in a huge sealed box and you don't get that spring effect. But huge size increases cost and decreases domestic acceptability. Speaker design is a series of compromises.

It also reduces the stiffness and rigidity of the box leading to greater distortion because of resonances.

For a given, relatively thin thickness of cabinet, yes that may well be the case.

But who says anyone has to make huge cabinets with the same materials and thicknesses as small cabinets?

Think about this one. Beef up the cabinets and you'll get better rigidity. You'll also have much greater mass in a huge, thick cabinet with large drivers than you will with a small, thinner walled cabinet with small drivers. That mass will couple the speaker to the floor more. You'll also have a larger footprint for a more stable connection with the floor.

 

[matt49]

For a given, relatively thin thickness of cabinet, yes that may well be the case.

But who says anyone has to make huge cabinets with the same materials and thicknesses as small cabinets?

Think about this one. Beef up the cabinets and you'll get better rigidity. You'll also have much greater mass in a huge, thick cabinet with large drivers than you will with a small, thinner walled cabinet with small drivers. That mass will couple the speaker to the floor more. You'll also have a larger footprint for a more stable connection with the floor.

True, though I doubt very much that many large cabinets actually do have a wall thickness that's scaled up proportionately.

Imagine a 5-litre speaker with 12mm-thick walls (e.g. the LS3/5A). Now scale that up to a 40-litre cabinet (e.g. the Harbeth SHL5), and we're looking at 96mm-thick walls.

OK, let's scale up in 2 dimensions rather than 3. The LS3/5A's front and rear panels are 496 sq cm; the SHL5's are 2044 sq cm. That's still a ratio of x4, so a wall thickness of 48mm would be required to retain the same integrity of build. Are there any 40-litre speakers with walls that thick? And just imagine how thick the walls of your Patricians would have to be to preserve the ratio. *shok*

I'd be extremely surprised if it weren't the case that large speakers generally have less structural integrity than small ones.

 

[Coll]

there will always be arguments for and against certain designs, its what woks best in your room,,, of the ported speakers i have owned, i always tried them with the bungs in, never liked it, yet i like the sound of the kefs, my conclusion is , you should use the speaker as it was intented in its design, if a speaker is ported it was designed to sound best like that, likewise the sealed kefs would probably sound bad with a hole drilled in the back*shok*

Quite right driver units have a low qts for ported cabinets and high for sealed.

There are few drivers that will work in either, but I am sure that people like Spendor design the drivers to suit the cabinet type.

 

[lpv]

there will always be arguments for and against certain designs, its what woks best in your room,,, of the ported speakers i have owned, i always tried them with the bungs in, never liked it, yet i like the sound of the kefs, my conclusion is , you should use the speaker as it was intented in its design, if a speaker is ported it was designed to sound best like that, likewise the sealed kefs would probably sound bad with a hole drilled in the back*shok*

which Kef's are sealed exactly?

 

[SteveR750]

Interestingly, the ATCs don't have the most solid sounding cabinets I've come across when I tap them. The D18s seemed much more inert, and S5e before them.

I've often though that the ideal speaker (for me) would be a 3 way infinite baffle design, the cabinet made of reinforced concrete for mass and damping. Messing around with various stands when I owned standmount speakers shoed the importance of attenpting to lock the drive unit stationary in space. If the Newtonian reaction is pushing the cabinet backwards instead of air forwards, then a whole lot of sonic detail is lost / coloured by the cabinet/stand system.

 

[Vladimir]

I have a pair of sealed enclosure speakers that used to cost quite a bit some time ago. The cabinets are quite heavy and rigid compared to the light and flimsy 8" Seas woofers with stamped metal baskets and smallish magnets. I still can't believe how these speakers achieve such tremendous bass with clean transients and great timbre on wire instruments with those (by my taste) petite drivers which in pairs at best amount to 12" woofers. It demonstrates to me that design is what gives the brilliant sound. Also tall sealed cabinet multidriver designs are better at bass transients and extention than cube like single large woofer with the same volume, as per the reasearch of John Dunlavy. Therefore I disagree with lindsayt that tall slim multidriver cabinets are just cost effectiveness and interior decoration trend.

 

[hg]

What do people consider to be the main benefits of a sealed enclosure?

Compared to the same driver in a ported cabinet (assuming the driver is suitable for both) the main benefit is a cabinet half the size and, depending on how the room behaves, there might be more bass well below the roll off frequency. The ported cabinet will be about twice the volume and extend the bass deeper by about an octave. The better transient response does not really apply in a comparison like this because although the resonances of the ported speaker degrades the transient response more than the resonance of the sealed speaker it kicks in at a significantly lower frequency. For the frequency range above the roll-off of the sealed speaker the ported speaker is likely to have the better not worse transient response. Below the roll-off of the sealed speaker the sealed speaker has insufficient output compared to the ported speaker but relatively a better transient response. Unfortunately it is the room resonances that tend to dominate what we hear at these low frequencies and so this advantage is likely to count for little.

 

[SteveR750]

What do people consider to be the main benefits of a sealed enclosure?

Compared to the same driver in a ported cabinet (assuming the driver is suitable for both) the main benefit is a cabinet half the size and, depending on how the room behaves, there might be more bass well below the roll off frequency. The ported cabinet will be about twice the volume and extend the bass deeper by about an octave. The better transient response does not really apply in a comparison like this because although the resonances of the ported speaker degrades the transient response more than the resonance of the sealed speaker it kicks in at a significantly lower frequency. For the frequency range above the roll-off of the sealed speaker the ported speaker is likely to have the better not worse transient response. Below the roll-off of the sealed speaker the sealed speaker has insufficient output compared to the ported speaker but relatively a better transient response. Unfortunately it is the room resonances that tend to dominate what we hear at these low frequencies and so this advantage is likely to count for little.

Given an average room (whatever that is, but a speaker designer must make that approximation), do you think a steady roll of a sealed box should in theory be less problematic than the deliberately enhanced resonance of a ported design? Less problematic as in the random variation of real rooms, and also perhaps that a natural 3rd order is more natural to our own hearing?

 

[peterpiper]

there will always be arguments for and against certain designs, its what woks best in your room,,, of the ported speakers i have owned, i always tried them with the bungs in, never liked it, yet i like the sound of the kefs, my conclusion is , you should use the speaker as it was intented in its design, if a speaker is ported it was designed to sound best like that, likewise the sealed kefs would probably sound bad with a hole drilled in the back*shok*

which Kef's are sealed exactly?

not sure about all kefs , but the q500 are sealed, with a couple of auxillary radiators complimenting the two driven units in a quite a compact floorstander , some reviews state the bass is lightweight, i dont find this at all,

 

[hg]

Given an average room (whatever that is, but a speaker designer must make that approximation), do you think a steady roll of a sealed box should in theory be less problematic than the deliberately enhanced resonance of a ported design?

It is not enhanced, in a competent ported design it is the right amount to extend a flat frequency response about an ocatve below that of a sealed design. It is a significant plus when it comes to efficiently generating decent SPLs at low frequencies and is why most speakers these days are ported.

However, to answer the question then yes in some circumstances. Not a large room, speakers with a decent amount of cone area, say 12" or multiple 8" drivers, a bit of equalisation and foregoing the bass for exploding planets then a sealed design is starting to look a reasonable approach. The cone area is costly though.

 

[hg]

not sure about all kefs , but the q500 are sealed, with a couple of auxillary radiators complimenting the two driven units in a quite a compact floorstander , some reviews state the bass is lightweight, i dont find this at all,

Passive radiator speakers use the same physical approach as ported speakers to extend the bass. A ported speaker uses the resonance of the box and the resonance of a slug of air in the port whereas a passive radiator uses the resonance of the box and the resonance of the cone plus weights. The advantage of the latter is avoiding problems with air chuffing in the port and the physical size of low tuned ports in modest sized boxes but this comes at the cost of most of a driver rather than a plastic tube.

 

[lindsayt]

Compared to the same driver in a ported cabinet (assuming the driver is suitable for both)

Very few bass drivers are ideally suited for both. Bass drivers tend to be suited for either sealed box or ported cabinets.

the main benefit is a cabinet half the size

Why half the size? Surely it's up to the designer / marketing department how big the cabinet in any speaker is and not down to whether it's ported or not?

and, depending on how the room behaves, there might be more bass well below the roll off frequency. The ported cabinet will be about twice the volume

Why? See my comment above.

and extend the bass deeper by about an octave.

For the same bass driver, yes. But surely the drivers that are put into any speaker are decided by the designer / marketing dept and not by whether the speaker is ported or not?

Stick a larger driver into a sealed box and you'll get the same bass extension as a smaller driver in ported speaker. Make the driver much larger and you'll get more bass extension than the ported speaker. All at the expense of cost and domestic acceptability.

The better transient response does not really apply in a comparison like this because although the resonances of the ported speaker degrades the transient response more than the resonance of the sealed speaker it kicks in at a significantly lower frequency.

Oh yes it does apply in the real world. Listen to a few different sealed boxes vs a few different sealed boxes and you'll soon discover which sounds more realistic in the bass.

You could even do single cycle measurements at various frequencies which would illustrate the problems with transient handling in ported speakers.

For the frequency range above the roll-off of the sealed speaker the ported speaker is likely to have the better not worse transient response.

Why? Surely that would all depend on factors other than whether the speaker is sealed or ported? Such as driver quality, size of cabinet, etc etc.

Below the roll-off of the sealed speaker the sealed speaker has insufficient output compared to the ported speaker but relatively a better transient response.

Again, that's only if we've got similar sized bass drivers in our ported and sealed examples. A competent designer of sealed box speakers prioritising sound quality over marketability would ensure sufficient bass cone size and cabinet size to provide enough bass extension and bass quality.

Unfortunately it is the room resonances that tend to dominate what we hear at these low frequencies and so this advantage is likely to count for little.

That may be true in some rooms. The echoey cave / modernistic minimalist type rooms.

What if someone has, for example, a very well furnished room with lots of open bookcases filled with vinyl or books? IE a room that acoustically has some similarities to an anechoic chamber? IE a room with clean bass?

It's up to each of us how we furnish our rooms. Room resonance is something that can be controlled, if anyone wants to.

 

[hg]

Very few bass drivers are ideally suited for both. Bass drivers tend to be suited for either sealed box or ported cabinets.

Many if not most midwoofers and woofers these days tend to be suitable for both sealed and ported configurations. The Efficiency Bandwidth Product (EBP) of the driver is an indicator of this with a value less than roughly 50 being suitable for sealed, greater than roughly 100 being suitable for ported and those in the range 50 - 100 being suitable for both.

Why half the size? Surely it's up to the designer / marketing department how big the cabinet in any speaker is and not down to whether it's ported or not?

In order to answer the OPs question about the pros and cons of sealed speakers the most obvious thing to do is to use the same driver in a properly configured sealed and ported cabinets. It is physics that determines the reality of this and not the marketing department which may help or hinder the perceived reality.

An optimum size for a sealed speaker is the one that gives a box Q in the range of about 0.5 - 0.85 with 0.7 being the conventional best compromise. The optimum size for a ported cabinet follows from sizing both the port and the cabinet so that the roll off of the output of the driver is exactly matched by the rise of the output from the port to sum to a flat response. If you do this for drivers that are suitable for both loadings you will see the sealed cabinet is roughly half the size of the ported but the ported gives roughly an octave deeper bass extension.

What is nice about physics is that you do not have to take my word for it or the word of a marketing department but can check for yourself if you are prepared to make the effort. Here is a free program that will allow you to study in some detail the performance of woofers and midwoofers in various speaker enclosures.

For the same bass driver, yes. But surely the drivers that are put into any speaker are decided by the designer / marketing dept and not by whether the speaker is ported or not?

Not sure I understand your point. The driver chosen will behave according to the laws of physics. In particular it will follow Hoffman's Iron Law in that you can have only two of high efficiency, small size and deep bass extension but not three.

Stick a larger driver into a sealed box and you'll get the same bass extension as a smaller driver in ported speaker. Make the driver much larger and you'll get more bass extension than the ported speaker. All at the expense of cost and domestic acceptability.

Again I am not sure I see your point. If a designer opts to put a large and expensive driver in a large domestically unacceptable sealed box only to get the same performance as a small and cheap driver in a smaller more domestically acceptable ported box then they will need to rely very heavily on marketing to stay in business.

Oh yes it does apply in the real world. Listen to a few different sealed boxes vs a few different sealed boxes and you'll soon discover which sounds more realistic in the bass.

This is not my experience where it is mainly the room that determines the quality of the bass given sufficient cone area to generate the SPLs. In an untreated room one can make a case for a sealed speaker but this is less the case in a treated room.

You could even do single cycle measurements at various frequencies which would illustrate the problems with transient handling in ported speakers.

If you use the software I linked to earlier it will do this for you. If you put the same driver in an optimum sealed and ported enclosures and look at the group delay you will see the ported driver actually has a better, albeit by a tiny amount, transient response above the frequency the sealed cabinet starts to roll off. Below this the ported cabinet has a significantly worse transient response but maintains a flat frequency response unlike the sealed cabinet.

For the frequency range above the roll-off of the sealed speaker the ported speaker is likely to have the better not worse transient response.

Why? Surely that would all depend on factors other than whether the speaker is sealed or ported? Such as driver quality, size of cabinet, etc etc.

Because the two resonances in a ported speaker are at lower frequencies than the single resonance in the sealed speaker. So for frequencies just above the sealed box resonance the sealed box is being influenced by its one resonance whereas the ported speaker is not yet being influenced by either of its two resonances.

That may be true in some rooms. The echoey cave / modernistic minimalist type rooms.

What if someone has, for example, a very well furnished room with lots of open bookcases filled with vinyl or books? IE a room that acoustically has some similarities to an anechoic chamber? IE a room with clean bass?

Such rooms will have almost no influence on the low frequency room modes we are talking about here. The bookcases will diffuse higher frequency sound and the furniture will absorb and diffuse higher frequency sound. The absorption of low frequency sound requires large structures.

It's up to each of us how we furnish our rooms. Room resonance is something that can be controlled, if anyone wants to.

Indeed but the devices that do it effectively are all large and often best put in false walls and ceilings which is not always an option.