Diy You're Doing it Wrong - Measuring Port Length in Speaker Building

Okay you may not be doing it wrong. However, a lot of people are. Watch it to make sure you are measuring your port length correctly. If you aren't you could be making a port that is tuned improperly and not getting the results you are expecting.
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[@2wilbster]

I never thought of that. I am glad I actually watched this. Man there is a lot to learn in this hobby

[@Toid]

Thanks! I am glad it helped you out. I definitely agree that there is a lot to learn. More than most people think. Thanks for watching!

[@RodofAllTrades]

A refresher for me, but news for others! Awesome.

[@paulweston8184]

Thanks so much for posting this video. I've been designing an enclosure for a Skar ZVX-12. I've been taking into account the area of space the port takes up, but at the same time I didn't feel a 100 percent confident that I was doing it right. Finally, I have a definitive answer to my start and end point for my port.

[@justinsprouse2564]

I'm about to build a box for the same speaker what was your final measurements and what is it tuned to?

[@FSXgta]

I had no problems with the port in my first box, but I had the wrong volume because I did not take account for the port taking up airspace. Box still sounds good, and I learned from it

[@Toid]

That is a great point and such an easy mistake to make. You are definitely not alone with that. I guess that is one of the great things about this community, learning from each other's mistakes. I'll have to add this one sometime to another video

[@RobertJeffersonBased]

I had the same misconception so I made a little video about it on my channel. I messed that up for like 7 years until I made a box with a bigger port and it was really noticeable.

[@dbwiskus]

Thank you for this video. Man i was way off. Much appreciated!!!

[@Thumper68]

I find it funny that people wouldn’t think of these things lol

[@MrScarcejason911]

Information to the masses ! I wonder how many "pro" box builders just went "oh ..damn!"

[@TheRattleSnake3145]

None, this is basic.

[@JViello]

Seriously? Zero.

[@Petrezen1982]

Thanks man, good job !

[@workingclassperson2124]

Box building is fun but as I get heavier and heavier subs 80-90-110 lbs it turns into a whole other ball game. Almost lost a finger once my make shift brace I was using slipped and just by luck I moved my fingers out of the way or else I would have had to try to unwedge a 80pound sub while my fingers were being crushed or just cut off. But the longer the port the better I like 28-18hz with my custom subs I get. Thanks!!

[@ericschulze5641]

All major Manufacturers of appliances say a 90deg. Elbow on a dryer vent = 2 ft of venting, due to reduction of air flow, this would apply to anything that moves air and any shape vent , therfore if anything you should make any port with a bend a little shorter than calculated

[@crippledbeast_U-toob]

Good call on that mistake. I am building my first custom box and would have missed that.😂

[@josephsaucedo8691]

The kicker audio app has most of these programs built in there one app along with test tones and wireing charts, air space calculater port calculater the only thing it doesn't tell you is were you should be Messering from make sense now when it give me the calculation. Should check there app out it worth getting the pays version. in less you really able to take your computer / laptop to Evey build. it has more features just for audio. 👌👍✌️

[@omark2423]

I want to build a box for 3 15's so do I want them in their own chambers or leave them open to work as one?

[@vusstoppyv4612]

I already knew this but it's nice to see a video on this because I see this all the time. Fyi to people, you can have your port outside the enclosure if you don't have enough room inside your enclosure

[@Toid]

Joe Baker thanks Joe! Great point about putting the port outside the enclosure. You can even make it a design aspect if you want.

[@vusstoppyv4612]

123Toid I have made ports outside enclosure as designed purposes in a line array tower. The port was (edit 26"lx2"d) 76"lx2"d and tuned 16 3" drivers to 37Hz. I couldn't fit that port inside the enclosure with room for the drivers

[@zacharyhafer2806]

I generally tune to 30 and then raise the tuning 2hz at a time until its right where i like it. For me i end up cutting between 1.5"-2" of port length of to raise my tuning just 1hz

[@grahamsquared]

Excellent vid as always. It would be interesting to discuss end corrections for slot ports as there seems to be no clear method in correcting actual port frequency other than measuring and adjusting. Some people on forums say slot ports should be 30% shorter if they share three walls on exit of the port. I personally think that it depends on the size of the cabinet and the scale. What are your thoughts?

[@tashspop]

i've always added half port width to the length for effective port length when running a slot port on an existing wall of the box. example if port is 1inch wide x 5 in long you would add .5 in to your measured port length to get effective port length. just imagine a 45degree line coming off your port board to the box wall then measure center line from port exit to the center of the imaginary 45 degree line. all this means i would have been .5 inch shorter on my port board if building the same box. am i off?

[@Dying_Breed.300]

Can u get the box program on your iPhone and what’s the name of it . Thx

[@EmoBubba]

Thank you for this... I always wondered how to calculate the length in a port that bends. Now if I could just get an explanation like this on speaker displacement. Does it assume a certain box thickness, or is it the entire displacement of the speaker in which case the cutout hole gets added to the volume of the box?

[@Toid]

If you use a program like WinISD where you input the parameters, it is assuming the entire driver as the displacement. In all honesty, the majority of the time, the little that isn't being taken into account, will affect the response very little. And will probably not be noticeable.

[@mpikas]

For most speakers, ones that don't have heavy cast frames, you can get a very good number with some simple math just by computing the volume of a cylinder with the diameter and height of the magnet and a cone the diameter and height of the speaker cone. The little bit the sheet metal frame, wire, spider... take up will be roughly accounted for by the amount that the small steps in the magnet structure... have that you didn't take out. On much larger driver the old school answer is put the driver face down in a simple box of known volume and fill it with packing peanuts and measure the volume of the packing peanuts and subtract the difference. Some people would take a large measuring cup and measure the packing peanuts coming out, but an easier way is just pulling the seaker out of the box and seeing how much the level drops. For example, you take the box the speaker was shipped in, it was 10x10x10 (just to make things easy), take any packing cardboard out, put the speaker face down in the box, fill it with packing peanuts (shake it around a bit to get them to settle into the nooks and crannies) pull the speaker out, shake it around again and if the height of the packing peanuts drops to 7", you have 3" of empty space on top you know the volume of the driver is 10x10x3 or 300in^2.

[@gianstevens7918]

Can you do a video on kerfed ports?

[@mwagner1996]

Preparing to build my first sub, I've been wondering about these very questions, now I have the answers! Thank you for the easy to follow and helpful video.

[@thethirdman225]

I guessed this must be the way but never knew for sure until you explained it, so thanks for that. BTW, what determines the length and capture area of the port? Could you possibly do something on how this works with a transmission line please? For example, if your quarter wave length is 1.2 metres, how do you design a box so that the TL is exactly that length? Also, is the TL measured from the theoretical inside face of the enclosure where the driver is mounted or is it from the back of the driver itself?

[@mrkazman]

This is a nice vid, you have a good speaking voice. pity about the framerate on the video capture, though.

[@alladin1237]

can you talk about slotted port correction factor ,when the slot port uses 2 sides or 3 sides common to the enclosure..

[@Str8GasGenetics]

Port correction factor: A port at a certain length will actually have its own resonance, this will change the tuning of your enclosure by a few hz. To fix this you use formulas to factor this in. Torres and winisd both factor this in for you. Common sides: How many existing walls of the enclosure the port utilizes. For example a normal slot port you only have to add 1 board to the port right? Because it uses the side top and bottom of the enclosure as 3 sides of the port. So it would have 3 common walls. If your port was directly in the middle of an enclosure and you had to add 4 boards for the port it would have 0 common walls.

[@mester84]

Can u link the program from where can be download

[@bvdvoort638]

nice video. So long story short: mesure the lengt of your port from the center of your port

[@goodgoat3096]

It would have been nice if radii on port ends and their impact on port length calculation would have also been discussed. Another common error in port calculation is using the nominal size of PVC pipe instead of the actual size. EX: 2" PVC has an internal radius of 1.0335 and an area of 3.356 sq in while if the nominal dimension of 2" diameter (1" radius) is used the area calculation yields 3.141 sq in, an error of about 6-1/2%. Other sizes of PVC pipe have actual internal diameter dimensions further away from the nominal dimensions so using the nominal dimension would arrive at even larger errors. Great job in raising awareness of the issue and showing the accurate method of measuring port length.

[@Toid]

Good Goat thanks! Those are both great points. I had discussed PVC in another video, but can't remember which one. I should have added that in here. Thanks for the heads up. I hope people read this, as it is an excellent point

[@goodgoat3096]

I created an xl spreadsheet with ID and OD area calculations for all sizes of standard schedule 40 PVC pipe in decimal and metric to avoid ever needing to do those calculations again. The spreadsheet is useful for port tuning and box volume calculations. I appreciate your efforts on these videos and your web site and hope that persons watching understand the time and work that goes into the videos.

[@mengyang589]

How do you calculate port length in a kerf port? And can a kerfed port be too wide?

[@tee228]

great explanation. lets hope all the box builders know this info lol

[@chinzouran6620]

Very informative. Thank you

[@SHADOWBEAR82763]

Calculating box volume is simple...width x height x depth (internal) divided by 1728 = volume.

[@hippo-potamus]

3:44 How far away from the corner (entrance) does the port have to be for the corner turn to not be included in the length? For example if yours had stopped half way (5 in assumption vs 10) and you added another 1.2 in piece to the end for bracing it would in effect visually appear the same only with a much larger entrance totaling approx 8in? So how far away would the entrance corner have to be for it to not "extend" the length? How what would be the size differential? Say if the port was 4 in and the entrance distance to corner turn was 8 in. Thank you.

[@GP-fc7jv]

How do you know how long to make it for the frequency you want to get

[@Dying_Breed.300]

I need help please 🙏 I need a box and it has to have .95 cubic foot net volume with 12.5 square inches of port area. Port length of 30.5 inches for it to be tuned 32hz. Now may max space is 40.5” long and 19” high with the bottom 11” and top 6” now the width can’t be more then 40.5 “and hight 19” the bottom or top can be more if needed. I have a 12”JL shallow mount tw3 -4 if you can please help me I would appreciate it

[@Toid]

It’s best to ask this in the forum. www.toidsdiyaudio.com/forums

[@vdfritzz]

what's irritating is that the longer the port, the more the box volume decreases, and then the whole calculation goes to shit again, what a pain to tune speakers!

[@droper683]

Great vid

[@davidembry5748]

@123Toid How do you figure out what your tuning frequency should be? Is it the F3?

[@Toid]

That is a great question. I did a video on it using the free program winISD. It isn't your F3, although, it might sometimes be the same. Here is the video. kzbin.info/www/bejne/nXK6potrhMinjbs

[@derrickwaller9397]

What about a wall port

[@l34052]

How do I work out the volume of a round tube port to factor that into my box calculations? I'm looking at a 4x17 tube.

[@Toid]

Great question. I covered that here: kzbin.info/www/bejne/nXK6potrhMinjbs

[@OnePotMeals]

This is a valuable video (and why I normally just use a tube). Could I ask that you rehearse a bit before you start? Sketchup is a great tool but the jumping around and the additional lines, etc take away form the great info you are sharing

[@Toid]

I always appreciate constructive criticism. Thank you

[@just4u239]

Maybe you can help me. I'm doing something I don't think anyone has done. I'm making a box for 4-12 inch subs with a quadflow system, with 3 different 12s 2 kicker 12inch svc 150rms 4ohm 1 kicker 12inch dvc 300 rms 2ohm each coil 1 pioneer 12 inch svc 4ohm 700 watts Dimensions 30x27.75x 18in Port cylinder Is 6 wide and 24 long to work with After I figure out port size I'm making a spiral helix for air flow with the port not THROUGH it, so there should be no chaufing and I will be able to adjust the helix in and out like playing a trombone to tune it, along with a 12inch Passive Radiator out of an old sub with the magnet cut off and a cable with a tension spring that I will be able to adjust to make tighter or looser. So if you could help me with normal port size with those dimensions. I'd appreciate it thank you

[@johndc7446]

Recommended specs/parameters for PA Sub's driver and enclosure? I heard they are different from car subs. I am planning to build my own PA sub but I am only familiar with the basics of car audio system.

[@criven3128]

You’ll want to look into horn loading and high-efficiency designs. It’s a totally different arena

[@clejhunbacus1347]

how about cross section area of the port?

[@kylewilson9809]

so how does it work or how should you measure if there is a round over edge or a kerfed port? do you only measure the straight portion?

[@Max-oi9ge]

That's a really good question... O.o

[@penttijakonen3817]

@@Max-oi9ge There isn't a simple way to calculate this exactly. Should be accurate enough to count half of the kerf or the flange as port length in most cases.

[@SuperPickle15]

You need a new graphics card.

[@Toid]

I think It's actually the screen capture program. There are no issues in person. I am using a 1060 6GB with an i7processor. I'll try to reconfigure the program later.

[@SuperPickle15]

Ah, You should try OBS if your aren't already

[@MrTruth111]

🤣

[@ChiTownTino]

Does it matter how high port? Cuz the height increases the amount air that can move

[@Toid]

Are you asking, does it matter if there port is high or low as far as placement? If so, then no, it doesn't matter.

[@Sqwan2]

I am wondering if this ever append

[@richardscarlett7942]

Nice. I have a beginner question though. What happened to the forward facing round ports in cabinet or tower speakers like the Fisher, Pioneer. Kenwood, Technics speakers of the old days? As someone that is interested in building his own speakers with higher quality components for quality sounding audio and saving money on labor that a manufacturer charges you for their name, looks and their 50 employee engineering staffs degrees. Is it better to place a round or rectangular port in front or back, or even forget about a port and just make it sealed? I have looked for explanations of this but cant really find a single source on youtube that really explains this when, where why and how magic. I like Kirby and your channels but Kirby is more garnish (except for his last 6 -7 videos), I need meat and potatoes to live on so I found your channel, lucky you haha. Also what makes a speaker good or great? At some point a speaker cant sound any better than another speaker so what validates a $15K speaker or a $60K home audio amp other than artsy fartsy and bragging rights on how much an idiot spends? If you could so a video or series I think it would go over great.

[@Toid]

Richard great questions! First the way the port faces is a non issue most of the time. So if you would rather face it forward you can. As far as what goes into what makes a high end speaker, there are a few things. The first is wide sound stage. In order to know this, you will need to look at the graphs for off angle dispersion as well as know about a term called beaming (spoiler - I will have a video on that in the future). Secondly, You will need to be familiar with distortion in a speaker. Although a speaker may be able to produce sound until x frequency, it can have distortion in that region. The easiest way to see this is with a calibrated microphone and a program like Rew. Third, a properly designed crossover with the drivers time and phase aligned is huge. If they are not aligned correctly, you will have some issues. Finally, every type of speaker has a different type of sound signature. Some people love the sound of soft domes, but not aluminum. Some enjoy compression drivers. Really that choice is yours. But just know that will play a part in it. So to summarize, you are typically looking for drivers with low distortion, fairly linear response, without beaming (wide sound stage) that has the sound signature you want. I think you will be surprised at how much less you will spend for the quality of components you use. P.S. I love Kirby. We are actually working on a collaboration. I hope you enjoy it.

[@paulweston8184]

I was curious about the response to this question and the question itself. I was reading the response from 123Toid and was thinking, I'm not sure this was the answer he was looking for. Then, I reread your question you said that you were interested in building your own "speaker" with higher quality "components". Did you mean that you actually want to build your own subwoofer or the enclosure?

[@ryancochrane1777]

Whoa boy! I do hope you're not building 12 inch square boxes for speaker enclosures, as any repeated dimension will incur standing waves at the 12inch Wavelength (in this particular case). A better approach would be to use a Logarithmic ratio box (3 different dimensions) and thus eliminate the possibility of any standing waves (The basics of audio design). Any box , where the dimensions are multiples of whole numbers is asking for trouble. Even when using Log ratios you can have problems, you just have to make sure you're outside the audio range when you hit that standing wave frequency, wallah! You are spot on with the length of the ports though, well done.

[@mpikas]

This is almost but not exactly right. In both your examples you used a slot port that used the outside wall as one of the walls, and the wall kept going past the end of the slot port. Some of that will add to the effective length of the column of air, because one wall keeps going the effective length is not a squared off line at the end of the port wall but a diagonal at somewhere between a 30 and a 45* angle depending on the configuration. In your examples, it will be somewhere in the 1/4-1/2", not as big and error as the bit you're showing, but in some speakers that could cause some weird tuning that you're not expecting, especially if the other wall of the port starts getting close to the outside wall but isn't quite there. One way to cut down on some of this weirdness in some configurations AND decrease port noise is to put a big radius on the end of the port.

[@domino7215]

What 3D software is used here?

[@Toid]

It's sketchup.

[@RinksRides]

cool story bruh. also, I had no idea Sketchup was still a thing in 2018.

[@Toid]

It is for me :) What are people using now a days?

[@akuma4u]

Torres box calculator takes this into consideration. Your wood pieces will always be 3 to 5 or so inches shorter than the actual port length

[@stevofla239]

No one would build their box that way

[@TheSpazzattack95]

Holy fuck took forever just too figure out how to measure a port get to the point thanks tho..

[@clarkgriswald1768]

12 inch would be better !!!! Longer is lower. So you just screwed yourself ! Again

[@iceberg789]

you are forgetting the volume speaker itself is taking inside the box.

[@nathanqualls]

No, he mentioned that towards the end.

[@Str8GasGenetics]

why would he bring that up at all lol? He's talking about ports. I guess he also forgot to mention that class D amps are more efficient then class A/B ?

[@penttijakonen3817]

In my opinion the first example is pretty much a worst case scenario and most people likely would not go with that design. I would even add a little to the 12 inches because the inner end of the port is right next to a wall. The fact that people lack very basic math skills needed to calculate port area and displacement of the enclosure is pretty sad really. Instead of using calculators and not really having a clue it would be a lot more usefull to figure out how to calculate them. A good video though, hope it helps someone.

[@domino7215]

What 3D software is used here?

[@Toid]

This is Sketchup. It is a free program