I just listen with my ears and that determines which speakers I like. I have both ported and sealed speakers. Best of both worlds.

Most port designs take advantage of what is called "helmholtz resonance", much like what produces the sound in a pipe organ. By tuning the port/box/woofer combination, one can use this phenomena to produce bass notes at lower frequency and higher spl than the woofer could in a sealed box at the cost of (usually) a larger box. At least that's how I understand it.

I've recently been doing plenty of experimentation with ported box designs, including making my own 6th order bandpass box, and here is what I've learned about how ports behave. They are in fact in phase with the diaphragm, due to their resonance their phase is inverted, causing them to add to the air displaced. If they subtracted, there should be an output dip either side. This also causes an impedance dip, as the pressure within the box, experiences a peak caused by the added displacement. The driver moves slightly less due to the pressure, and causes an impedance dip as EMF decreases voltage being fed back to the amplifier. Efficiency is increased as power is "shifted" from moving a diaphragm with relatively high mass to a tube of air resonating, with a relatively low moving mass. Ported boxes have a steeper roll-off than sealed, as the port doesn't allow pressure to build up lower than its resonance. Low frequency air flow may come and go as it likes. It behaves sealed at higher frequencies, however only reflected waves come through. Due to bass having an inherent non-directionality associated with its creation, the speaker box is simply adding or subtracting the local air pressure around it. Phase from front to back shouldn't matter. Enclosures where it does are referred to as "dipoles". Port surface area is relative to length for tuning, possibly why front ported boxes have longer ports is due to a greater surface area attempting to eliminate "chuffing" with lower velocity airflow. As far as I'm aware passive radiators behave like ports, though without chuffing, are less efficient, and from what I can tell work better with smaller boxes than ports. Transmission line speaker enclosures work by having a set transmission line length, usually tuned to either 1/4 or 1/2 wavelength of the desired tuning frequency, feed the rear wave down a tube with said resonance. Port width is usually equal to the driver surface area and constant along the line, unless a tapering/horn loaded design is used. The effect on the air from thought experiments is like hanging a weight from a bungee cord, move your hand at the resonance of the weight, and although your hand is moving only a 1/4", the weight may be moving 1" or more. This works similarly to a ported box, though requires much more space. Generally transmission line boxes reach the lowest notes, though this may be due to them performing as dipole enclosures down low. Dipole enclosures (also from thought experiments) effectively add a springy moving mass to the driver, lowering its resonance, which improves low end. The distance between the front of the driver and the rear creates the pressure differential, and therefore sound. I kinda fell half asleep whilst writing this, so hopefully it makes sense

"Shift Registers" at 4:14.... Been a while since I heard that term. Paul must be an old assembly language geek ;D

The pressure inside a ported box is actually higher than a sealed. Low frequency waves actually go through the box a whole lot easier (below the tuning frequency of the enclosure, Fb.), this is called unloading. Below Fb the speaker increasingly "sees" no enclosure at all and will rolloff at ~24dB/octave. To avoid damage to a vented box with somewhat high Fb you need to highpass the frequencies below Fb as these will cause excessive excursion to the driver. Port "chuffing" can be largely avoided by simply decrease its air velocity to below 17m/s. Many use flanged ends to help alleviate this problem as well. A well designed port/enclosure will won't have these issues to any audible degree. A T/L and vented enclosure is not the same thing. Front port or rear ports really does not matter at all in a technical perspective. The wavelengths at low frequencies are so long that the port placement only amounts to a fraction of a frequency cycle's phase difference. You must have some distance (normally at least the vents diameter) between the wall and the backside of the enclosure which can lead to issues if you try to hang it on a wall or something. The main reason they place the vent at the back is to be able to save space really. Futhermore, a vented enclosure is by itself more efficient and has lower non-linear distortion than a sealed enclosure due to less excursion around Fb. This of course increases the maximum output of the driver within its voice coil thermal ratings. The only thing that a sealed enclosure is better at: as mentioned, the actual group delay/phase shift. The vent cause a phase shift in its passband which increases its group delay in these frequencies. This group delay's audibility must be seen in relation to the actual frequency. At 50Hz a full period is 20ms (1/50=.02s), while at 25Hz a full period is 40ms (1/25=.04s). With certain alignments the group delay can exceed a full period, at some point it starts to get noticable and this is what people refer to as "sloppy bass". A lot of times this issue is fixed by simply equalizing the frequency response as group delay is a derived function of the magnitude and phase response. The enclosure-inherited group delay of a vented design can be fully corrected for with FIR-based signal processing. In my opinion, the vented enclosure is usually far superior to a sealed box, especially if you got a powerful DSP / room correction. Note that not all drivers are suitable to use in vented enclosures, most high Q-drivers should be avoided for example.

Respect a man who uses shift registers to explain something.

I recently purchased Kali Audio front ported Studio Monitors. I used to have the Yamaha HS8's, but the 8" woofer with the rear port produced to much boomy bass as my studio is small thus my speakers are forced to be closer to the wall. The front ported Kali Audio monitors with 6.5in woofers and front port design fixed my issues perfectly. In addition they have a trim pot to compensate for speaker locations and room environments. So sometimes front is better depending on the the acoustics of your listening room.

These feel like hanging out with your grandpa on a weekend and he's teaching you about something your parents didn't want to learn but you're super interested in

I was just trying to figure out what "that hole in the front" was, I felt like a dumbass for calling it a hole haha

Glad to see you're promoting the elac line I have a set of UF5 Towers and the UB5 bookshelves and hoping in the near future to purchase your Sprout 2 for my UB5's great job🎧🎶

"in your little shift registers"-Paul is an iconic engineer

Very interesting subject. Vented speakers have (as you know) been around a long time. 1960's vented systems did tend to sound "unnatural". A.N. Thiele and R.H. Small research into vented designs was used by, I think, two companies in the early 1970's. Electro Voice and Ohm Acoustics. Venting took three major types; ducted ports, passive radiators (drone cones) and transmission line (labyrinth). I auditioned and purchased Ohm model L vented systems in 1978. I still enjoy these speakers today. Old argument was... acoustic suspension speakers sounded "tighter" than vented systems. My Ohm H speakers have an 8" woofer with a 12" passive radiator and bass is tight, deep and very satisfactory. I guess the main advantage of venting speakers is to provide deeper bass in a smaller box. Perfect for teeny weeny NYC apartments.

These videos are awesome, I'm learning many things I've wondered about for years.

Love this channel I am learning a LOT.

I prefer the curve of my ported subs. High at 30hz and steep roll off from 40 to 80 hz. I've spent my life chasing after perfection and to me this is as close as I can get. They lack the punch of a flatter curve, but I'll take that trade off. There is only one song I know of where my setup has an obvious lag between notes and it bothers me but I would still not trade it for anything else, especially not a sealed subwoofer. So much of this has to do with what music you listen to, and I think when people have disagreements they sometimes fail to take that into account.

Every port shifts the phase by 90 degrees at its tuning frequency, no matter on which side of the enclosure it sits. If it's on the back you usually lose a few decibels in the bass because the phase shift increases due to the time it takes the sound to travel from the back to the front. Wave lengths in bass are big in comparison to the dimension of the enclosure therefore they bend around the edges (spherical radiation). But ports also let a small amount of mids pass through which is perceived as distortion. In the mids the sound waves are smaller and don't bend around the edges. Therefore they don't reach the listerner if the port of a mid-woofer is on the back. With a port on the front this distortion might lessen the sound quality. The solution: port on sides, top or bottom as near to the front as possible. The huffing and puffing noises are generated by turbulences of the air flow inside the port and on its edges. Therefore those Elac speakers have a port with round edges. If the diameter of the port is too small the air flow gets too fast and turbulences occur even on the surface of the inner wall of the tube. The cross section of the port should be at least one fifth of the effective piston area of the driver. Even better is one fourth or more but the length then might become too big for the same tuning frequency. The standing wave inside the tube becomes a problem then. Before I discovered your "Ask Paul" series I started a similar podcast in German, apart from most of my other videos being in English. Im currently translating my first few episodes into English but it takes a lot of time because they were not scripted. On many of them KZfaq's automatic subtitle function didn't even work. (The German version seems to be not that good yet.) If I gathered some more subscribers from the English speaking world it would maybe motivate me to speed up my work. Source of all my knowledge: German DIY loudspeaker magazine Hobby HiFi.

Very nice explanation.I learned many things.There are also down ported speakers like Wharfedale diamond 200 series and diamond 11 series (no chuffing noise at all)!!

Paul, your description of how a port works is much less pornographic than Zeos Pantera's attempts to explain why that hole is there and I thank you for that. There are books dealing with loudspeaker design and I'm sure my 'accountant' will let me buy one when the time is right (hell freezing over, apparently) but until then I'll have to rely on the insights of people who actually do this stuff for a living. I look forward to the new PS Audio speaker even if I know that it will be many multiples of that Elac bookshelf you held up at the start of the vid - thanks again for the video.

Rear ports are more picky in regards to room placement. If a rear ported speaker is placed too close to a wall, there can be either an increase in bass amplitude or a cancellation of lower frequencies due to reflections and phase alterations of the sound leaving the port. Make more room behind them, and they will have smoother bass characteristics. Front ported speakers do not experience this problem, so they can be placed closer to walls. But because the port is facing the listening space, it might be easier to hear the port noise. I've got some rear ported bookshelf speakers, and they're pretty close to a wall, so I ended up plugging their ports. Their bass sounds muuch less boomy. And the reduced bass range is being taken up by my subwoofer. It's a win-win.

The port has an air mass that is suspended with the airvolume inside the box. When this mass reach resonance due to the triggered soundpressure from the woofer, it starts to resonate. At resonance, the air in the port goes out when the woofer does. This will enhance the bass level. The wavelength at 50Hz is about 7 meters, so it does not matter if the port is in front or on the rear. However, at lower frequencies than the ports resonance frequency, the air in the port starts gradually to get sucked in while the woofer goes out.

He seems really nice.. and it's rare to be that humble and open as an executive (which I think he probably is) Great video and I learned a few more things. I see why closed subs has an advantage being active.

When I eliminate the ports from the speaker box I enjoyed a lot than before .Luv u Paul . u are great .

as an electrician i think of ported speakers as LC oscillator , the port is the inductor and the box the capacitor. you may also think of a spring (box) with a weight (port) attached to it.

What most people seem to forget is that sealed speakers also have a port. That is the driver itself. The driver's backwave will resonate and reflect back through the cone in a number of rather unpredictable ways. And that is with all the stuffing in the world too. Of course if you set a whole room aside for the speaker we are close to infinite baffle and the effect will be very small. But that is fantasy land for most speakers.

I wish you’d do a comparison of sealed , ported , and passive radiators. I’m personally a fan of how passive radiators sound. But there’s very little information available on them

Ports are a way to alter the physics needed of enclosure size to produce sufficient bass. I used to own a few of the Dunlavy speakers that were all sealed boxes - no ports at all. And they had terrific bass, but they were large enclosures (not very high on the wife-acceptance scale). If you didn't mind your speakers almost as large as your refrigerator, the bass was articulate, fast, and very real, with none of the problems with ports. Still the best I've ever owned.

I prefer sealed over ported, but some ported models are great also. Rear ported designs are much better than front ports, to me anyway. Sealed just has a cleaner smoother bass and just plain sounds better I think.

Conversely to having a port. Does the sealed speaker with the compression and vacuum going with the cone operation, vacuum when out, pressure when in, actually create a quicker stop and then quicker restore of the cone and reduce vibrations as the cone goes back to its central position. Thus making the base truer to the original as it is now self controlled. Overthrow and sluggish return are now self regulated by the size of the box in relation to the cone movement.

When properly designed and manufactured, ported speakers can be used in two different ways: if you have the room to have your speakers out from the rear wall, as in on stands, rear ported speakers will be your best bet. If you don't have the room, and may even have to wall mount then a front ported design would be your best bet.

Paul reminds me so much of my dad... but happier

Thank you for explaining speaker operation Physics.

Thanks for sharing some magic of acoustics.In phase & out of phase sound production.

Actually the port sound output is in phase in its adjusted frequency. Due to resonance of the enclosure and the "Piston mass" inside the tube. Lets say you want to adjust the bass reflex supporting frequency to 35 Hz. You got a 50 L Box, than you need a round port approx 4" width times 12" length. Big floor standing speaker. Out of the adjusted frequency the "Air Piston" in the tube can not move properly, or even not at all. The fuction of the port increased if approaching the frequ. and its decreasing if leaving. But in this case it doesnt matter in my eyes, if the port is in the front or in the back. Because the wave length at 35 Hz is 10 yarts and you got a 1' deep Speaker maybe (front to back). So the back port would be 1/30th out of phase reaching your ears. Bass is emitting nearly 360° the same around the speaker. so doesnt batter to me. A passive Butterworth Frequency cross over for example, with -6 db per octave, generates a 90° delay in Phase in the low pass way, thats nearly 4' - Bass/Mid separation at 300 Hz . However it is the commonest frequency cross over. That tears apart the exact imaging of the stage arround the crossing frequencies. Some very smart invetors and developers build speakers that wave no delay in Phase, absolutely time coherent. A giant step towards natural sound play back. cheers.

ooh, fancy little Elac speaker, Jawhol ! I have passive radiators in the front of my 1978 Philips AH-487 speakers. It looks like a woofer membrane without the magnet and the voicecoil etc

From personal experience... I listen nearfield with the speakers at ear level. When I had front ported speakers? When certain notes were hit, it was like sitting in front of a hair dryer set to cool. On cold nights I would get cold air blown in my face. So... rear ports have another good purpose. I prefer sealed or passive radiator speakers. More accurate sounding.

Ports box is more produced Louder bass than sealed box but there is delay bass frequency comes out. Sealed box is always had smaller box needed and more accurate bass than port bass

What is your thought on Passive Radiators?

I have a pair of B&W 804 D3 floor standing speakers. They sit 3 feet from the back wall but are close to the side walls. I didn’t like the mid bass boom I was getting so I have now put the supplied foam bungs in the ports that are on the front of the speakers. They sound way better now. If I add a sub (or two) to extend the bass down, would I still get any bass bloat in the room, seeing as the 804s are now “sealed”? Thanks.

Thank you Mr. Paul. Nice explanation as always.

just looked thru some comments ( about 30 + ) didn't see anyone mention ' Thiel / Small' one of if not the first computer type speaker box/ port designs.... My Koss speakers ( 1978 1020 ) Koss claimed were the first to use this development. Seemed to work, the Stereo Review mag , Sept '78 > had a comment ' response curve flat + - 2 from 20 to 5000 hz'.... (closer to an amp than most speakers, even Advents of the day.my thought.) and distortion ' among the lowest we have yet measured' PS the Koss were fairly large, the mid range 1020's 33in high, 15 wide - 10 in bass with 2 front ports. Just as a guess, ported designs seem very common today.

Whether on the front or on the rear, the port is designed the same. At low frequencies the placement is not critical, since the wavelengths are long, so it can be put on either side. At frequencies below the port resonance there is indeed an issue with anti phase and cancellation and you get a steeper roll off. At the port resonance the driver does not move as it experiences anti resonance, while the output is coming from the port alone. Finally, at higher frequencies the port becomes decoupled and the behavior is the same as for a closed box.

Ports have some specific disadvantages. First of all, the loudspeaker is acoustically unsupported below resonance. The box is open. Any frequency below the box tuning causes excess cone motion. The second major disadvantage is that the box is a Helmholtz resonator that only resonates at one frequency. That adds pressure to the bass, but not at the same frequency. One difference between a port on the front, back, sides, top or bottom is its proximity to the wall which can aid or hurt the amount of pressure. Another difference is if the midrange that leaks out of the hole can be heard by the listener or not.

brian weir my Focal tower TL speakers have a front port. So do my old college airborne/phillips set. my B&W's have a rear one, and my Infinitys don't . All those great folks who designed them were not hacks; similar to your comment on A vs D, I think the original design and intent is the most important thing. They are all different and likeable to me. I like my Focals best in general. 1 second ago

Paul I really enjoy watching your KZfaq videos and the information you give. I would love to visit your factory one day!

Thanks Paul. Also, I really like your ending music.

There is also an added bonus to rear ported speakers, in that it's much easier to control bass intensity. It's mostly a given that speakers are best positioned at good distance from a front wall, that is, the wall behind the speakers. However, with rear ports it's possible to use the wall to stratigically enhance lower frequency performance. That can be particularly useful with overly lightweight, or higher frequency orientated speakers.

Thanks for the detailed explanation - really informative

So my question is what is a proper preamp to amplifier to mixer hook up. I write and play music for the love of it. And just want my sound to sound live and clear. But I do have a small room size for my set up. I do share the signal with a home audio receiver.

Sealed has a cleaner sound but requires more power. I personally think it depends on what kind of music you listen to. I dont know. I like a sealed box for rock and metal. But if you get into the hip hop style the speaker cant react fast enough and starts to bog. If that makes any sense. Love all your videos Paul.

The main reason why the ports are at the back is the mentioned sound they (sometimes) make. It is simply an artifact from air being pressed trough a tube, the entrance of the tube act a little like a whistle. Positioning it on the back hides it a little. The phase of the ports can be adjusted by the lenght. Simpified, the volume of the air in the tube has a mass and the the air inside box acts as a spring. If you have a spring and a mass you have a resonator which is allso a low pass filter. Those of course shift the phase of the signal and the signal can be in what ever phase the designer wants it to be at a certain frequency. A second resonator close to the resonance ferquency of the driver adds some complexity to the whole system, which will not make the design process easier. The more easy (controlled) way to archive the same are passive membranes but you have less possibilities to modify the parameters.

hahaha set that aside in your shift registers. people this is a man who knows his digital electronics.

And here I thought you were going to speak loudly about Port wine. 😄 Kali Audio purports (NPI) to have solved the port 'chuffing' issue with their front port design. You might look into that if you are curious.

A joy listening to you everyday. Thanks.

If you don't like the sound of ported speakers, can you just fill the port with foam filler, or is this not a good idea?

It's been my observation through the years that I prefer rear-firing ports as opposed to front firing port. IDK if the bass slams into the corner of the room behind the speaker and has more wave-length to travel or what. I was skeptical of my Kicker's Sub-box having a huge side aeroport, but it doesn't seem to effect any sound quality. so... IDK.

You also have ported on the bottom of the cabinet, downfiring speakers. So back port, front port and bottom port.

The port controls the speaker over a narrow bandwidth. The driver that you use in a ported box can have a lighter cone and therefore the speaker can be efficient and occupy a small volume. It reduces the cone mass requirement and makes the box smaller and this leads to sensitivities in the range of 89 dB SPL as opposed to 84 dB SPL for 1 meter, 2.83 volt sensitivity in free field. Closed box speakers need to be bigger to have the same lower bandwidth limit and efficiency.

It can be added that a front port is still a rear port; of course it is,it acts only on the rear part of the woofer,it just has a *longer* traject to cause a delay in the air movement to allow the "meet" , half ass in phase,with the front pressure wave, and try to reinforce it.

I actually have had 2 different surround speakers series by Psb Audio with ports and found the number of ports made a difference as well. My current speakers have 3 ports and I also have port plugs.

A sealed cabinet will give the best bass. But it is tricky to calibrate and you would need a strong amp.

G.day I’m all the way from Guyana I need to know if I should use a Ported or seal box for my low mids,plz note that the boxes are facing out the car by the back side window

Hi Paul. I have a pair of Roland DM-20 front ported. Because I'm curious I pulled them open and found them empty except for the built in amp. I decided to stuff them a little bit with some pillow material. These are monitor speakers used, and was wondering if filling them is OK? They sound good, especially once I took them off the floor. Should I not have stuffed them, or does it not matter? I use them for listening to music, not mixing or anything. Thanks!

Great explanation 👍

Med always comes out of ports too (but at a really low level). But it's enough to effect the med tone and make the voice sound wrong. But if the vent is at the rear of the speaker the med (from the port) is less heard. That's why I reckon most ports are rear.

Paul's a visionary

I read a book by a Dr Bailey who produced a design for a transmission line speaker back in the 1960's It was a design taken up by IMF in the UK who produced some of his earlier designs. His latter design had a lattice of a triangular path which was, he said aimed at reducing internal cabinet resonance. Infinite baffle designs usually had to be quite large to reduce the affects of compression and vacuum within a speaker. The concept of a reflex design was to reduce the affects of compression and vacuum within a cabinet, to produce a smaller speaker and extend the bass response. The design was renowned for reducing definition due to the problems of phase cancellation. I always had a large living room so I favoured transmission line designs with a separate high quality reflex speaker, sitting on top for the quality of sound in the upper frequencies. I spent many years in the Hi Fi trade and researched a lot of designs and our company produced the JR 149 which as you might know was designed by Jim Rogers who produced the legendary LS3/5a design used by the BBC. I still have a pair of Bowers & Wilkins DM4's and a pair of Keff B139 bass units. I hope to resurrect a pair of Transmission line speakers one day. I don't like Reflex speakers because as you say they lack definition. Thank you for your informative videos. Jeremy Travis former buyer for Teletape London

A reflex speaker having a front port does not thereby become a transmission-line speaker. Acoustically, it doesn't matter where the port is placed, assuming we're talking about a speaker designed to reach fairly low - say below 50Hz. Speakers for boom boxes that can only play down to about 150Hz could be a different matter. The important point to observe with rear-port speakers, is not to push them up against a wall, which can block the port and make it ineffective. Drivers selected for ported speakers should have stiffer surrounds and spiders to help prevent over-excursion at very low frequencies (below the port's tuning range).

At tuning frequency the port is at 90 degrees out of phase with the driver. At the upper resonance is where the phase is perfectly aligned between the driver and port. At the resonance below tuning freq of port they are 180 degrees out of phase and the port and driver cancels each other like a dipole. The port is basically loading the driver at tuning freq of port.

I had a pair of monitor audio rs6. They had a port at the front and one at the rear. They were actually nice sounding speakers

how do I calculate optimal port dimensions (length and diameter for a round port) to gain maximum efficiency and maximum output for a given subwoofer

In a ported design the speaker cone barely moves near the ports tuning frequency. So the box and cone actually see much more pressure than a sealed enclosure. This can have a couple advantages like reduced distortion if designed correctly. This is a misnomer and common misconception that sealed produces less distortion. There are many advantages like the amp is only needing half the power at the same loudness further reducing distortion. If you dont believe me listen to a self powered gelelec studio monitor. No chuffing either .

Is it ok to partially block my ports to cut the bass down a bit at night? I use Klipsch rear ported speakers.

Given a round to square opening, front/rear ports use (mathematically calculated) LENGTH of the tube ( inside the speaker) for optimization.

Firstly, thank you so much for these videos. I've only just dicovered them. Now I am.going to ask a very basic and possibly, naive question. What is possibly better between a scoop bin and a rear mounted speaker. 'W Bin'??? I've owned scoop bins before, but never a rear mounted speaker. Is one better suited to a certain situation? Size of room etc.

I have a great fan of passive radiator speakers.

For bass you have the measured "thile-small" parameters of a woofer, which you can use to make a spreadsheet that will tell you what it will do in a particular closed box, or ported complete with minimum port diameter. You can check out box sizes and port lengths for tuning the internal resonance that shores up the bass. A closed system needs a woofer with more self-bass resonance than a ported system. The ported woofer would be bass-shy in a closed system, and the closed woofer would be blubbery in a ported system. For little systems like a 4 1/2" woofer, you need the port. Ideally you'd have a long-throw woofer. You can get a -3db of 60HZ with the right woofer in 5-7 litres, which could/should be a narrow mini-tower. Perfect for a desktop, with the speakers at the top. To keep mids from coming out perceptibly you line the inner walls with damping material. For the closed system, they are generally filled with damping material to prevent inner reflections from hitting the cone and sounding it. You can't fill a ported system, of course. The thile-small parameters include: frequency of resonance in HZ in free air of the cone. Measured by using a sine-wave generater, ac voltmeter, and resistor, and amplifier to graph the speakers resistance over the bass frequency range. There will be a big peak at that frequency. Then, DC resistance. VAS - "volume equivalent" if I remember right. You put the woofer on a box of known volume and measure the resonant frequency, which will be higher due to the air spring. You want to know the linear travel, usually 3mm each way if not long-throw. You need Qts - my memory of this is vague - the self damping of the woofer, electrical and mechanical - combined. Mechanical - like, if you thunk it, does it go woong or blup? And the area of the cone. So now, you have what you need to graph it in a trial box. Therefor you can shop for woofers and plug in their parameters for the size system you want. Many will be too resonant and deliver a blubbery bass, while many will be too non-resonant (in the bass) and have little bass. Now when those babies arrive, you have to test them because their published parameters can be quite off. This would be less likely with entry level and up high-end woofers from Europe. If you want a ported system, a woofer with, memory holding, about .4 Qts will be great in a box the volume of its VAS. Now you can tune it (using box size and port tuning) for maximum bass or better damping, the latter of which will make the bass roll off slower and be more controlled. The box would be bigger. To compensate for an average British room I read about years ago, you'd actually want the slowly rolling off bass. Bass is bouncing back from the walls, overall boosting it is that case. Bass is omni-directional so half goes around the back. This actually makes it quieter than the mids when you're using an accurate mid-woofer, and you have to lower the mids in the crossover. The fact that the impedance is rising in the woofer with frequency helps. There's a 6db rise from bass to mids over 2 octaves. Forgot the formula but I think for a 12" wide box the top is at 1,000 HZ. So there's alot that beginning speaker-builder books don't tell you. Oh - and the air in the box is part of the spring-return system for the woofer, completing its internal spring. The spreadsheet can also tell you how loud the system can go, using the linear throw length, bass tuning, cone area.

I really enjoy Paul's authenticity! ...spite the fact the transmission is emitting from Boulder, Colorado! Yikes!

I think a rear port has a distinct advantage over a front port. With a rear port, strategically placed, it's possible to effectively control bass reinforcement. Try the same trick with a front ported speaker, nine times out of ten, all you will end up with is excessive bass boom.

If designed properly transmission line speakers can have very low bass output though the cabinet size will have to be fairly large.

I live in Port ugal. Will plugging ports harm the woofer in any way?

I've read that rear ports need space behind them to keep them from "chugging".

You said that only high frequency goes out than you said that bass output goes out too but bass is a low frequency and you said low frequency cannot pass to the vent can someone explain me what im confusing

5:45 this is incorrect. Vents do not relieve pressure inside the box, on the contrary it increases the pressure until you get to a little below the fb. Air has mass and the ports use this mass to load the driver. Push a lot of air through a little hole and it moves very quickly, when the driver begins moving back the other direction the air in the port is still moving the same direction this is where the increased pressure comes from and why you get more sound pressure. Sound is pressure, less pressure less sound.

Read the second chapter of of Vance Dickason's Loudspeaker Design Cookbook. It's is the worse transient response (time delay) that is the problem. There is always a delay and the inherent inertness reveals itself with complex percussion music. Also the ported enclosure exhibits less control on the woofer especially below the port resonance.

Put simply, a ported enclosure is an acoustic resonator The mass of air in the port resonates with the volume of air in the box. If tuned correctly it should radiate the bass in phase with the woofer hence greater bass output. The 'tuned circuit' of the box/port causes a 180 degrees phase shift for the driver rear output near the resonance peak of the woofer. If critically tuned it can also damp or smooth out the bass response of the system. There are formulas for calculating optimum port sizes for a given box and woofer (Thiele Small parameters) Not room here to go into this now.

I'm not a Port guy either. Prefer Single Malts.

I have audiology Grason Stadler 162 with altec 418b loudspeakers. There is a lot of clarity with highs and no mid and low range. I was wondering if I should port the sealed enclosure.

For me there’s nothing like aperiotic ported speakers (Dutch audiolab largo pro speakers). They sound amazing!!

Front ported are much easier to place than rear ported ones as the latter need room at the back (normally 20cm) for all that as sound energy to be released easily. Hence, Big spaces rear ported, small spaces front ported. Example, you can't keep a rear ported bookshelf in an enclosed area...where as a front ported will work just fine.

I love your expert opinion on amplification but your explanation on ported speakers is flat wrong. #1 the sound coming out of the port is in phase with the woofer whether front or rear ported. #2 The port is not a pressure release (in the frequencies in which it performs it's duties). #3 A port does not work like a transmission line to invert the phase. A port tunes the box at a certain frequency determined by the diameter and length of the port. At this tuning frequency, the woofer and port output are in phase. Because the woofer is moving in the same direction as the air in the port, the pressure inside the enclosure is GREATER than the pressure of a not ported(sealed enclosure). Don't believe it? Run this test. Find the tuning frequency of the ported speaker by running an impedance sweep. There will be 2 humps in the low frequency area. In between the 2 humps will be a valley, this is the frequency at which the ported speaker is tuned. Let's say the impedance dips between the 2 humps down to 6 ohms at 40 hz. Plugging the port with your hand, run a 40 hz test tone through the speaker until you see the woofer really moving. Now take your hand off the port and notice that the woofer now is barely moving yet the speaker is producing even more bass. The reason is, the air spring (pressure) in the box has increased due to the port output being in phase with the woofer.

Two additional comments. First, the advantage of a front ported speaker lies in less placement restrictions than a rear port which needs room behind the speaker to "breathe". But both disadvantages of ports (placement restrictions and port "chuffing" ) can be ameliorated by using a passive radiator which is essentially a port substitute.

rear port is to save space. if you put a port in front you need a bigger box to situate the port to the front. the advantage of a rear port is when the speaker box is near the wall. the bass at the rear port hits the wall and bounces to the front giveng a bigger booming sound.

Very well explained, thanks for the video :)

What do you think of horn loaded stuff?

hate chuffing sound, love acoustic suspension on my advents nice tight punchy bass

in your little what registers ?

Paul, why do some B&W speakers have dimples on their ports?

Intuition tells me placement is even more important for rear ported speakers as they are "playing the room" more (back wall reflections). Same for dipoles, magnetic planar, electrostatic, open baffle, etc. True or false?

Nice video Paul. How about ported speakers vs passive radiators?

Ive got a question for Paul McGowan and viewers out there. I'm building a 2x12" speaker cabinet for a 100w peavey valveking head and wondered should I port the cab? I don't really want too as it will be a closed back cab, but does and will it make a huge difference in the sound if I do? And if I put a small hole in the cab say 10-15 or 20mm for example just to let the speakers breath/move properly within the cab and not let out alot of noise will this help with speaker over all speaker perfomance and or sound? Thanks and love your videos.