Each enclosure type has its benefits. If cost were no object and you could have multiples, what type of enclosure would you use?
Sealed
Pros: the easiest to model and build, no compression or turbulence from the port or horn, the deepest extension, the lowest phase shift/group delay
Cons: the least efficient in terms of physical size and conversion of electrical to sound energy, requires a driver with a lot of excursion (these tend to be less efficient) to geet good deep bass
Ported
Pros: easy to model, somewhat easy to build, great low end efficiency, great overall efficiency in terms of physical size, port tuning protects driver from overexcursion
Cons: port compression and turbulence, the port limits extension on both ends because of the tuning and port resonance, generally needs to be large to get a good alignment and port with enough area to minimize compression
Horn
Pros: the most efficienct in terms of converting electrical energy to sound energy, decent efficiency in terms of physical size
Cons: difficult to model and build, peaky response, nonlinear compression, wonky behavior right outside the passband, large and heavy, not that much more efficient than ported in terms of physical size (meaning ported with multiple drivers and the same size cabinet can deliver similar results)
Ported horns and other higher bandpass enclosures have the same pros and cons as horns
So which would you choose? For home audio I would choose multiple sealed enclosures with high xmax and high power handling subwoofers. For live sound I would choose ported subs or horns depending on the application. If tons of SPL and chest-thumping bass is the goal than it would be ported horns.
welcome to the forum Kanye, sorry about your Twitter, happens to the best of us LOL ( JK )
first of all let me say that on any other website what you wrote above would be considered G_d level wisdom but that’s not going to stop me from correcting it - don’t take it personally.
i’m not picking on you i’m just assuming that if you came here you want a deeper level of knowledge than can be found elsewhere
good question …
so far so good …
uhm … no.
sealed enclosure produces less deep bass for any given voltage input but it actually is more efficient for any given level of energy input ( versus vented ) because it draws far less current. you can use HORNRESP ( free but hard to use ) software to plot efficiency and you will see what i’m talking about. or just let me know if you need further clarification - from experience 90% of people can’t understand this - namely, can’t understand what efficiency is - but if you want to understand it we can certainly talk about it.
again … no. it doesn’t require a driver with more excursion … it requires a driver with more cone surface area, and when you look at it this way it is actually more efficient not less. remember for same enclosure volume you can use a larger cone when going sealed. of course this is an over-simplification.
so far so good …
as i said before only in terms of voltage, not amperage. but inefficiency is actually losses to heat and it is the current that results in those losses, not voltage. ported gets higher output by cutting a valley in the impedance peak around resonance, but this also results in higher current and associated heat and efficiency losses.
only compared to horns, certainly not compared to sealed boxes.
only at the extremely narrow frequency band around port tuning - so narrow as to not really be very significant benefit even with proper high pass filter implemented. to really get protection you have to aggressively turn the bass down and be satisfied with one note bass at tuning frequency.
not a big deal for a properly designed subwoofer. more of an issue for full range speakers which must juggle between having a port not muddy up midrange and deliver powerful bass. if you have a 80 hz low pass filter you can just use a huge port that will probably compress a lot less than the driver itself.
at the low end it’s a hard limit yes, at the high end - could you operate through port resonance ? i don’t know. there are resonances everywhere in a speaker - air inside the cabinet, cabinet itself, cone itself, suspension etc. would port resonance be worse than all of them ? probably. certainly if i could avoid it i would.
right … if we compare a 15" full range versus 15" subwoofer one of the main differences will be the size of the port ( in addition to larger box volume for sub ). the full range will optimize for cleaner midrange while the sub will optimize for harder hitting bass. so the full range will have shallower box with more padding and smaller ports while the sub will have deeper box with less padding and larger, deeper ports. i’m not just talking ports tuned lower but ports that are physically larger.
sort of … but again, not as efficient as people think because as with vented enclosures horns pull higher current than sealed boxes because the acoustical transformer has the effect of flattening impedance peak. instead it is arrays that are the most efficient when it comes to bass. an array is actually a super horn so to speak. horns are better suited for higher frequencies where size is not an issue and arrays can be problematic. of course you can array horns as well, and in fact you should.
not really … again, it is really arrays that are efficient in terms of size which may seem counter intuitive. but a smaller array will outperform a larger horn.
100% which is why all serious companies like JBL have given up on horns.
the real reason to do ported horns is to provide some cooling for the voice coil.
for cost no object i would go with arrays whether for home or prosound …
but you’re asking about bass specifically …
horns is not a question of home vs prosound as much as a question of permanent install versus portable … for a permanent install horns make sense if you can design and build them yourself and integrate them into your space. for any application where the speaker may need to be moved horns don’t make any sense.
as for sealed vs vented it’s probably going to depend on your room gain. in a small airtight space like a car room gain will perfectly compliment the rolloff of a sealed enclosure. in a large venue like a stadium there is no room gain and vented makes more sense.
actually in large venues room gain is replaced with the mutual coupling gain from arrays, which is why in any large music festival it will be 100% arrays 100% of the time …
so we could probably say arrays for large venues, vented for small to medium ones and sealed for very small spaces like a dorm room or smaller.
as for high excursion remember you can just use higher cone area. BAG END for example is a company that used prosound drivers in sealed alignment in very small boxes with electronic compensation to get extension to 8 hz.
i’m going to summarize by saying worry about cone area first, then excursion, then cabinet volume and then whether it is ported or sealed.
the saying is there is no replacement for displacement but it’s really the cone area that there is no replacement for.
you can get more cone area with larger drivers or with more drivers or both.
for subwoofers 18" to 21" is the sweet spot right now based on market availability. JBL only goes to 18" while most other good companies like B&C, Eighteen Sound etc go to 21" …
24" home theater subs are mostly low quality and overpriced … just like MTX Jackhammer before them in the car audio space they’re mainly for show… of course a $1,500 24" driver will outperform a $800 21" driver but it won’t deliver twice the performance, because the 21" driver is a workhorse and 24" is a freakshow. this isn’t inherent to physics in any way but simply an issue of marketing and industry standards. in the future 24" might become the workhorse but it is doubtful because of arrays …
the reason JBL is sticking with 18" is because dual 21" become too heavy to be flown as arrays …
Powersoft makes 30" and 40" M-Force drivers but those are very niche and can only be driven by special Powersoft devices designed to drive them …
in fact even the B&C iPal is designed to be driven by special Powersoft modules though most people buying the iPal aren’t aware of this …
it goes back to impedance and efficiency issues i brought up earlier … iPal and M-Force have a very reactive impedance curve that Powersoft modules are optimized for …
as the head of Powersoft said driver and amp are one system and must be designed together. he is opposed to even using watts as a unit - he says we have to look at volts and amps separately and he is right. watts are not useful when it comes to describing reactive loads such as subwoofers, but worse than that they are actually holding back subwoofer development by introducing this need for drivers to try to approximate resistive loads which robs them of power and efficiency …
essentially a speaker has both resistive and reactive components to impedance but the resistive component represents only the WASTED energy …
thus the more resistive the impedance the less efficient the speaker …
yet only Powersoft actually takes this seriously by saying we have to design the resistive component out of the speaker and make sure our amps are optimized for the result …
while i’m testing my new hall effect switch keyboard ( dayum it is smooth as buttah ) let me throw some more ideas out there …
if you spread enough subwoofers evenly enough through a large space it will probably begin to approximate the behavior of a small space with a single subwoofer …
in other words mirror symmetry when it comes to acoustics behaves the same way as if the mirror was a solid boundary …
if you ever built car audio systems you khow how much bass gain there is in such a small space but really you can have the same gain in space of any size so longer as subwoofers are spaced no wider from each other than the dimension of that car cabin …
most drivers are designed to reach about 30 hz in vented enclosures so they will begin to roll off at around 50 hz when sealed … so how can you design the room to have room gain begin at around 50 hz instead of say 10 hz as you would have in a large room ?
well the common wisdom is room gain start is a function of longest room dimension …
but i posit its also a function of subwoofer spacing …
this isn’t going to be an exact science but just like line arrays have more bass than treble so should distributed subwoofer arrays have room gain …
in other words you can take a driver designed to only reach 30 hz vented / 60 hz sealed and take it all the way down to 10 hz by using enough of them distributed evenly through the space …
bottom line when you use multiple sources it becomes more an issue of how many of them you have and how evenly they are spaced and less of an issue of how each one performs …
i mean obviously you can’t take the array much lower than the tuning frequency but you can go sealed or you can tune as low as you like …
in the end whether a speaker is sealed or ported can be a moot point when the tuning is low enough …
one “trick” is to build cabinets with for example four ports out of which 1, 2, 3 or all 4 can be plugged. this way you can get several useful alignments out of one box. then based on real world testing you will decide which to go with.
being able to individually tune each sub electronically would also be pretty sweet. there are programs that let people do this. one limitation is that it’s hard or impossible to control the phase of deep bass without a full blown computer running the DSP and introducing massive latency that would make gaming impossible and require some kind of video delay for movies.
anyway … you want lots of cone area, evenly distributed, possibly with ability to re-tune enclosures by plugging ports … and ideally with individual DSP control of every sub location.
i think either sealed or ported would work as long as there is enough cone area and the tuning is low enough.
horns are simply not flexible enough in case you need to move. you can custom tailor them to a space but then they will never fit anywhere else. for this reason many small subs are superior.
you want to think in terms of reconfigurable arrays that can be adapted to any environment … this is how the pros do it and there is no reason not to use the same insight at home.
The problem with tuning low is that the port needs to be long relative to the port area. So low-tuned ported subwoofers either have ports with low port area and high compression, or they are very large in volume. You can look at JTR to see what a very low tuned ported sub looks like for home theater. The 2400 has port tuned to like 11Hz or something; it is very small, but it is as large as the box permits with its length. The result is serious port compression at all levels. A larger box would allow for a larger port, but then that begs the question of whether it would be better to just use multiple drivers in a sealed configuration that would occupy the same volume.
I like the idea of arrays. They would also control the directivity of the sounds waves and clear up room issues. I don’t know how arrays change the impedance of the system, but I guess it makes sense. I know coupling subs together has benefits beyond the sum of their output. So you’re saying a large array is like a large horn?
i won’t dispute that there is serious port compression - but is that actually a problem ?
consider JBL - they researched ports exhaustively, they understand basically every aspect of port design and yet most of their subwoofers and speakers have very simple ports like this:
in other words they are aware of port compression, and they know how to reduce it, but they simply don’t bother except in the product line designed for absolute maximum performance to weight ratio because it is designed to both be moved to a new location every week and to be suspended in the air.
they must have done cost / benefit analysis and determined the most basic ports had the best price / performance ratio, thus reserving better ports for what is essentially a cost no object application.
again you have to ask yourself - why does port compression bother you so much ? you’re losing output that is free to begin with. now if you have audible port chuffing that’s another matter - but are you really going to hear port noises in some hulk smash scene in which that 10 hz port actually moves enough air to create noises ?
you can also use a high pass filter slightly above tuning frequency which will reduce port output … you would still be getting free port output, but a controlled amount of it.
as i said sealed would be better if you can take advantage of room gain at the very lowest frequencies provided those frequencies make any difference for your content. i mainly listen to music which means stuff below 30 hz is irrelevant to me so even if i could take advantage of room gain to get down to 4 hz for example it simply wouldn’t be of any benefit.
room gain is 12db/oct same as sealed box rolloff which means they cancel each other out completely resulting in flat response all the way down … provided your total displacement is enough for your room volume and you can pressurize the room evenly …
vented and higher order boxes have higher rolloff slopes which means room gain can never cancel them out …
so going sealed is a question of being able to take advantage of room gain …
array effects obviously highly frequency dependent and also room dependent. for bass you probably want to fill the room as evenly as possible with subwoofers which would create an even pressurization with minimal standing waves.
for other frequencies in a normal room you ideally want floor to ceiling arrays.
for large venues the best array type is J-array or progressively curved array suspended above the crowd.
haven’t actually thought about it but in extreme cases they would probably reduce the height of impedance peak. i wouldn’t worry about it though. also HornResp will model all this for free if you really need to know.
essentially two subs next to each other have same output as one sub with FOUR times the power fed to it. this is because feeding the driver 4X power only doubles displacement. this is because displacement is proportional to speed but power is proportional to energy which is proportional to speed squared ( kinetic energy formula ). two subs achieve same displacement at half the speed so they produce same output at half the power. it’s almost cheating but not really - it’s actually a tradeoff. you save on amplifiers but spend more on subwoofers.
yes.
the reason speakers are inefficient is because airload mass is too low compared to moving mass of the speaker cone, thus only a fraction of kinetic energy of cone can be transferred to acoustic energy of the airload.
by creating a funnel for the air horns essentially increase airload mass until it matches the moving mass of the cone thus optimizing energy transfer.
think of a horn as a gun. what if you removed the barrel and fired a gun without it ? well you would get hurt but aside from that the bullet would still move forward, but not nearly as fast as with a barrel. the barrel is needed to transfer the energy of gunpowder to the bullet by keeping the pressure high instead of allowing it to dissipate …
however arrays actually have the same effect …
if you detonate a nuke you no longer need a barrel - the explosion is large enough to pressurize the space without any funnels …
which is why in the old days with the gramophones horns were mandatory because the transducer was small and weak and power was low …
but not with 20,000 watt class D amps power is almost free and horns make little sense …
arrays act as horns because they also prevent pressure from dissipating … when two subs are next to each other they each only now have half the space available to push air out to … this has literally the same effect as a horn …
which is also why most bass horns are actually designed to be arrayed. without arraying a bass horn would need to be prohibitively large. but because array has horn loading effects relatively compact bass horns can be designed that still work well when arrayed. again, HornResp will model all that.
but the question is - do you really need 150 decibel bass ? if you don’t then there is simply no way to justify the amount of space and plywood for a horn system with good bass extension.
so again, efficiency is high when airload mass is high relative to speaker cone mass, which is the same thing as saying that efficiency is high when air movement speed is high relative to the speed of speaker cone movement … those are the conditions for effective energy transfer from the cone to the air.
this is because acoustic energy is basically kinetic energy which is proportional to mass times speed squared.
the voice coil moves the cone which moves the air load. a little bit of thinking will reveal that most energy will remain in the cone so it will be like digging up holes and then filling them back up with dirt - a complete waste with no useful work done. for efficient energy transfer you need to increase the mass and speed of airload while reducing the speed of the cone. a horn accomplishes that. so does the array.
an array also effectively creates a funnel for air just like the horn, but the funnel is virtual. it is created by the symmetry plane which to acoustical waves might as well be a concrete wall as movement of air across the symmetry plane cancels out making the air there stationary as if pressed against a wall.
the reason you probably don’t want to use a line array for bass at home is room standing waves. it is more important to eliminate standing waves for bass in a room than it is to maximize output and efficiency. of course you would have same problem with bass horn in a room.
what you want at home isn’t kinetic energy of bass WAVES but even pressurization of space. it will cost more and not be as loud but hopefully it will sound better. this borders on pseudoscience of course but i have to mention it.
to evenly pressurize the room you would have to fill the entire volume of the room with speakers - which is of course impossible. so instead you go for some compromise.
