Your subwoofer port rule of thumb is wrong!

[@DIYAudioGuy]

Learn more here: kzbin.info/www/bejne/Y6rSoYekmrhqnZosi=bcwffJ0o_oGmO3-O

[@hectorortega9131]

I would like to see if you could design the plans for my box built? If so, how can i contact you.

[@CarlVanDoren61]

Rel R&D passive subs to Control back wave guide 😊

[@CarsandCats]

Sealed box smiling and eating popcorn.

[@DIYAudioGuy]

🤣

[@clarkgriswald1768]

Sealed with twice as many subs :) same space

[@markwentz8332]

I miss my SI HST-15 in my Ranger

[@kaedeschulz5422]

​@@homeshopmachinist84 A well designed ported box doesn't really sound worse. I did an experiment where i build a sealed sub and then ported and used EQ to make the frequency response the same. Apart from the ported one being louder i honestly couldn't tell a difference in sound quality.

[@WariorMageThief]

@@homeshopmachinist84 That is not true. Power handling is gonna depend a lot on the suspension and the voice coil size more than the box alignment. Thats why you see these mega woofers that you can sit on and will barely move cause the suspension is so stiff with 3 or 4 inch 8 layer coils. The box size is going to have a lot more effect on the power handling rather than whether it is ported or not. If the air spring in the box you are using is too little cause the box is over sized, the over excursion of the cone outside of the magnetic gap does not allow it to cool properly. The motor needs control over the subwoofer to keep it within the gap because it moves faster and coolers better. At the end of the stroke, the subwoofer's motor force is at its lowest and moves slower and doesnt allow the heat to dissapate fast enough. Likewise in a ported box it is very easy to over heat the coil for the opposite reason.The cone is barely moving at the Fb andd doesnt move enough to dissapate heate even though it is well within the magnetic gap. You make up for this by using large multi layered coils that can soak up heat without burning.

[@ralphlongo1975]

I don't spend a lot of time in SPL areas, but when SQ people say cone area is king, that is because a large cone moves way less to achieve the same SPL. The less a driver moves, the more likely it is to be in a lower distortion range of the driver. Just a little FYI that not everyone that says that is talking about displacement, which also includes X Max. 😀

[@DIYAudioGuy]

Food for thought.

[@BenHeien]

Linear displacement is definitely what matters, so woofers like the stereo integrity IB-18 are perfect for SQ! Infinite baffle (as close as a car can get...) Setups are definitely my favorite. Especially when the "big woofers don't play tight" people hear a couple 18s killing double kick drums better than their sealed 10s

[@lunam7249]

wisdom is rare in the comments ❤️❤️👏👏👏

[@BenHeien]

@@lunam7249 I generally live by the rule of "If you don't know what you're talking about, shut up and listen!" If I'm not 100% on the subject, time to read more. Oddly, there's plenty of SQL (not those idiots with walls full of PA speakers) guys who are running a very large amount of THD in their bass and it still sounds damn good. I've not experienced it in person, but I've read 30% THD in subs is hardly noticeable. I guess it's time to crank the gain and find out!

[@lunam7249]

@@BenHeien correct !! your correct again!!👏👏❤️❤️, im an Ph.D. EE PE and do this for a living... low "distortion" does NOT equal "sounding the best"... a computer analyzer on a spectrum mic determines distortion, a jury of 12 listeners determines which sounds the best......the cerwin vega stroker stadium 18 inch is the cleanest sounding bass in the world, or the velodyne servo controlled 12 inch..or the "powersoft" digital 50 inch woofer... all 3 have distortion around 1% distortion up to half power....the human mind + ears cant differentiate distortion very well below 50hz..our minds our tuned to 3khz, electric guitar, evolutionary the sound of screaching steel is "very dangerous", while earthquakes and volcanos are very rare occurances.. low frequency makes high excursion, wind is high excursion, so our brains have built in "wind crossover filters", 1% dist. on mariah carey singing is horrible, bass at 20% is hardly noticable...while i dont like jl , the 13w7 jl, at 1/4 power is very clean in low freq amplitude linearity vs most other including sunset or dd...interestingly the dd with the 100 pound magnets do insane SPL, but sound absolutely horrible with music SQL, because the big magnet overdamps the cone, i work with the "klipple" sound computer people and that system blows away alot of common "myths", check it out sometime..btw, true distortion of everything is extremely high, its just that companies ONLY LIST "AMPLITUDE LINEARITY" distortion, theres odd order, even order, linearity , frequency, transient, doppler, waveform, q, braking, on and on...its a miracle we can even recognize our own spouses!

[@arnicus208]

I purchased a Fox Accoustics enclosure for my gen 4 Ram crew cab (4 10” subs) and it is amazing! However, I noticed chuffing at higher volumes and some lower frequencies. After watching numerous videos about ports, I took the largest radius router bit I could find to the port mouth, sanded all the super thick paint (?) out of the port; which gained almost 1/4” of height and width (!), and used wood filler to radius the inside corners of the port. It sounds like a lot of work, but it yielded a noticeable volume increase without chuffing. Firm believer in the enclosure is the most important part of the sub system equation Running DC Level 3 subs on a JP4300 a 320 alt and lithium behind the seat. Best I can do until I don’t need the back seat anymore, then, who knows! 🤔 😳

[@DIYAudioGuy]

I have always suspected that those boxes had a chuffing problem.

[@herrtrigger7220]

One constant issue across many different subjects today is people confusing "never had any problems" with optimum performance. Their ego has them clinging to comfort over embarrassing facts. These people rejected the bad news about Santa, they also swear cables, power filters and DACs make a huge difference.

[@CoreMaster111]

That's also why a lot of people say something like "oh, this cheap chinese product is really good." when in reality it's shit but because people don't know any better they'll claim that it's good.

[@Thomamps]

I've been trying for decades to tell people all these points and you have done it brilliantly in a video. Calling anything round an aero drives me nuts. I have built one square aero port in my time.

[@BenHeien]

Kerfed slot ports are a lot easier to build and tune low, but a few 10" tube with BAP flared ends? Wooooo wee, they're cool.

[@DIYAudioGuy]

I have notice an uptick in the number of people calling all round ports aero ports and it drives me nuts as well.

[@BenHeien]

@@DIYAudioGuy "got me a skar evl-18 in 2 cubes with an aero port made of 2" steel piping. Rule of thumb baby"

[@DIYhyfy]

Thank you for your work on these topics. It ain't easy. You make it look effortless. Summarizing hours of reading into a bite size video.

[@DIYAudioGuy]

I've been researching this one off and on for quite a while, finally decided to sit down and make the video. Hopefully people will get something valuable out of it.

[@JJ-kf2uk]

Thanks for this! I remember a rule of thumb I used for transmission line ports and also applied it to simple vented cabinets. It was the port area must be a minimum 75% of Sd. Nothing to do with box volume. That served me well before software:)

[@DIYAudioGuy]

I was always told that for quarter wave transmission lines the line had to be the same size as the driver. Not sure where I read that I might need to go back through my notes.

[@soldjahboy]

Thanks for clearing this up, it's a common thing people get really wrong and the worst part is it's almost impossible to correct someone otherwise. This video should clear this up much more for people who are still confused.

[@DIYAudioGuy]

I just hope people don't get lost in the weeds. Hopefully the four points I made at the end clear things up a lot.

[@veridico84]

This is why I love large transmission line setups as well as sealed boxes.

[@DIYAudioGuy]

My home theater speakers are transmission lines. parts-express.sjv.io/a1Jk4M

[@RecordnRtist]

I really appreciate this video and a lot of the comments are spot on as it relates to port area. My experience is just like others, I started with sealed enclosures and 12" woofers because they were simple and I had the space in my Rx7 hatchback. As I began to explore ported enclosures with the pre-fab box I purchased/tested proved greater output and thus began the journey. My old 12" sealed (which was based upon Kicker suggested recommendations) is in its 3rd iteration. Originally designed for a set of Petras, it now encloses 2 Skar IX 10" dual 2 Ohms being powered by two Pyramid PB-446 amplifiers. The vents were originally foot long 3" PVC, but are now rectangular MDF 10" by 1 3/8" by 21 1/2" long. I purchased a DATS and tested and designed everything using WinISD, just like the moderator of this channel. I missed my goal of 36 Hz and landed at 32 hz. Bigger ports operate more consistently at higher volume/power output. All I can say is that it takes experimentation. The last small modification I made was adding Yoga blocks inside of my chambers to decrease the interior volume about a tenth of a cubic foot and it increased my Fb by a whole 2 Herts (now @ 34)!! lol BUT the output increased and the lows did decrease smoothing out the impedance curve. Thanks for the content of this channel and not being arrogant like I see a lot of times here on KZbin.

[@DIYAudioGuy]

Thanks! I'll try to keep cranking out this style of video. All right

[@RecordnRtist]

@@DIYAudioGuy I've been following you for some time. You get it. The origin of my foundation for acoustical comprehension that introduced me to speaker parameters is: Radio Shack's 'Advanced Speaker Systems: How to Design and Build High-Tech Computer-Designed Speaker Systems' By: Ray Alden. I'm old. lol

[@JoeJ-8282]

This is crazy math! I thought I was a speaker guy, but I honestly am totally lost in all of these calculations and ratios and variables! I can't even comprehend all of these calculations and formulas, especially when they're contradictory sometimes! I guess that's why speaker designing and building is such a difficult thing to do properly, and why there's so many different designs out there!

[@DIYAudioGuy]

Anybody can learn this stuff. It just takes time.

[@JoeJ-8282]

@@DIYAudioGuy Well, after literally over 30 years of trying to learn all I can about speakers, I still don't understand all of the insane math and calculations that have to go into designing and building them!... But I have a learning disorder anyway, so I'm always struggling to comprehend what's going on, even though tinkering with speakers and stuff like that is still fun for me, so I guess that's what really matters. I don't know how to use a computer to run programs to figure all of this stuff out either, so the computer programs that will do all of these calculations for you, are kinda useless to me.

[@deaconsmith5988]

This why it’s easier to go 16 times cu ft…

[@slimsqde7397]

@@JoeJ-8282 you could do it, you just need someone to walk you through each variable of the equation and explain what it is and how it effects the solution.

[@JoeJ-8282]

@@slimsqde7397 True, that would definitely help! Unfortunately I don't have any friends who are at ALL interested in speaker design like me, so I'm left to trying to figure it out on my own, or by finding KZbin videos that explain it, but that's rare.

[@johnj2496]

Thank you for making knowledgeable but able to understand videos for non us NON rocket scientists

[@TheJPspike]

This is a fantastic video that explains a lot of what I'm seeing in bix design "rule of thumbs". I'm definitely getting that program for box design...

[@DIYAudioGuy]

Glad it was helpful!

[@michaelbloom5342]

I've been using mathematics to design enclosures since the 80's. When I first got interested, I went to my local library and checked out everything they had, and that included David Weems', Robert Bullock's, and Vance Dickason's books. Then I used my trusty Ti-34 calculator to design boxes, because this was way before personal computers. Everybody always wondered why my boxes sounded better than theirs. The answer to that is easy: I read those books over and over until I understood what they were saying, and I also paid attention in 10th grade Algebra class.

[@DIYAudioGuy]

That is awesome!

[@12Messenger]

I was debating if I should switch from slot port to side firing aeroport in the trunk.

[@DIYAudioGuy]

I built several of the side firing aero port style enclosures and I like them.

[@stevenPounder-p4b]

I have a friend who has this level of understanding of audio and implements said data in to his audio systems among his various vehicles yet 3 inch strait pipe is his go to formula for exhaust on whatever he owns.

[@DIYAudioGuy]

Ha

[@scarce911]

Glad that ive been a sealed enclosure guy since 1998 ...started with infinite baffle

[@any1alive]

infinite baffle truely is bae, then sealed lol

[@kaedeschulz5422]

Which is why i moved to Passive radiators when possible. When a drivers that doesn't need much volume yet pushes a ton of air the port needs to be huge and in some cases would be bigger than the volume which is where Passive radiators come into play.

[@DIYAudioGuy]

I am a big fan of passive radiators for that reason.

[@kaedeschulz5422]

@@DIYAudioGuy Hell yes! It's such an awesome thing to use when it's a well made one! I can't imagine building my current tiny 3way project with 2 TB W3-2088SOF with a port. Or if was to build something with the Dayton E150HE for example. No way to do that with a normal port!

[@Grommet2007]

One other thing that tends to get "lost in the noise" - the standard port length calculations typically assume that the volume occupied by the vent is much less than the volume of the box. This is not necessarily true for car audio subwoofers, particularly those designed for high output. In those cases, it might be best to design the boxes as multi-step or offset-driver transmission lines (the "steps" being dependent on the shape of the box and the location of the driver and vent within the box).

[@DIYAudioGuy]

That's a new one on me. I'll have to look into that.

[@Grommet2007]

@@DIYAudioGuy We had a discussion about this effect in the "Hornresp" thread in the Subwoofers forum on DIYAudio. Even came up with a "correction" for the vent equation, but unfortunately the accuracy of the correction depends on the shape of the box.

[@grizzly6385]

I am about to build my first box with 2x12” Kenwood KFC-3011s. What I did for the calculations is used the manufacturer recommended data and went 20% bigger for the box. The box is around 107L net volume and the aero port I went twice the recommended size due to using two speakers. I entered everything in the winIsd and BassBox 6 pro and it all seems flawless on paper, but will see.

[@DIYAudioGuy]

I think that'll sound pretty good.

[@BackAgain-i8t]

Port makes the sub more of an instrument as it can be tuned and is not a true representation of the audio

[@DIYAudioGuy]

Sealed enclosures roll off early, which is not a true representation of the audio.

[@RustyShackleford-m8t]

Thanks for the informative video. I have a practical application question. I am looking at ported box and due to size limitations, the options are a RF T1 Slim with a recommended vented box volume of 1.5 cuft, and a JL TW3 with a recommended box volume of .6 cuft. Both are the 10" versions going in a Chevy Colorado box from subthump with a volume of .85 cuft. and a 3"x4" x 30" long port tuned to 33 hz. Which should I choose?

[@shawnsanderson3695]

Exelent! This is a great video for the diy and professionals that need more understanding of their builds finally and detailed description of it! Thanks for doing all the work for us.

[@DIYAudioGuy]

Glad it was helpful!

[@Onewheelordeal]

Only subwoofer I've ever blown was an 8in as a teen learning a hard lesson about ports. I built a box with too small of a port and the chuffing was so bad I was determined to avoid it on my 2nd try and ended up making the port so large the driver was basically open baffle and could no longer handle the same power level I'd had it at in the chuffy box.

[@JWarrenPhilly]

I have found a quick way that seems to work for me if software isn't availble. VD x (AMP Power converted to electrical db gained + 10) /60 If you have a 1000 watt amp, that is 30db of gain. If the sub has 80 sq inches of cone area and an xmax of .5 inches, you would take 80 x .5 inches x (30 + 10) / 60 which equals ~26.67. That formula gives me 26.67 sq inches of port area required. If I added more power say 2k, its 40*43/60 which is 28.67 sq inches. This has worked a treat for me and can be done with little effort in the event you don't have a pc available so rough it for better than guess.

[@DIYAudioGuy]

That makes more sense than going off the box size.

[@JWarrenPhilly]

@DIYAudioGuy I always thought of it as energy and how efficient you transfer it coupling to the air aka vent air. 2 subs with the same cone may have different characteristics yet move the same distance in a gap. If they are equal in those elements, it tells me they will sound different which translates to the forces at work inside the enclosure. The best way I see to calculate that is the power handling. Unfortunately, not all woofer manufacturers honestly state the power handling. Hopefully, that makes sense to them bassheads reading these posts and, of course, watching the videos.

[@donaldwatson4991]

Back in the 80's and 90's I always went by 1/3 the diameter of the sub for a minimum port diameter per sub. One 12 = 4in port or 4 12's = 4 4in ports or one 8in. Port diameter.

[@DIYAudioGuy]

That sounds reasonable to me.

[@Bassotronics]

Awesome info. I wonder how much that applies to us tube guys who don't use "boxes".

[@DIYAudioGuy]

The physics are the same. The shape of the enclosure makes no difference.

[@Bassotronics]

@@DIYAudioGuy Thanks. :)

[@clarkgriswald1768]

Since the box has to be so much bigger for a properly ported enclosure. Just add a mother sun and keep it sealed with the same size single ported enclosure. Bass for space. Seems like this ol would be the best way to go.

[@annihilationindustries1990]

thank you for that info I will be taking it into consideration for my next box

[@DIYAudioGuy]

Glad it was helpful!

[@reinekewf7987]

2:30 that ist why those super small subwoofer have such a thick rim and a long driver, it has the same vd as a "standard" subwoofer wich is 2 to 3 times more surface area but the driver depth is smaller but it displace the same volume. another big advantage of those small subwoofer is they have a wider range of frequencys and a better loudness control, so they can be finer tuned with a less precise amp. but they need more power and have lower response time. but there are typical in portable bluetooth speaker because of there small size and deep bases, even they the cost more power and and a deeper case. but the needed power and control circuit is way cheeper so they can cram more battery in the case to compensate that.

[@keithmarlowe5569]

"There are rules". Forums and blogs "There are other rules". DIY Audio Guy.

[@DIYAudioGuy]

🤣

[@tenvali1434]

I mean i like ported boxes but i think passive radiators is the way to go if you want a smaller system

[@DIYAudioGuy]

I'm a big fan of passive radiators.

[@michaelbaldwin8869]

Well I'm going back to sealed box that has a accurate and tight bass

[@jsteezy80]

I was thinking of doing the same. I used to run 3 JL W6's back in the day and it sounded great

[@DIYAudioGuy]

I am seeing a lot of sealed box fans in the comments.

[@SQ_Silverado]

im dreaming of a hybrid box with a low tuned aero port for some wind that can be plugged to seal the box and get better SQ. 😢

[@DIYAudioGuy]

That is a thing, I have seen it done.

[@Sqnutt]

Vibe audio did that back in the day. Their loaded enclosures came with plugs styled to match the box so you could run sealed or ported

[@Seikatsu121]

Seeing this on the day I extended my port with an empty toilet paper roll and hot glue

[@DIYAudioGuy]

A lot of prefab boxes use cardboard tubes for the port. It's a little thicker than a toilet paper roll but it's cardboard all the same.

[@Hayawasa]

So does this method improve the bandwidth or hurt it for the sake of a higher but more narrow db peak? Reason i ask is ive always built the ports 12- 16 inches per cf to have a little of everything . I know it sacrifices a little of everything to do so, but im not to worried about optimal performance if it is only talking about db.

[@justinvanburen8259]

Another great episode!! Thanks

[@DIYAudioGuy]

Thanks for watching!

[@_Wake_Up_If_U_Can]

Short comment: Thanks for the video. Enjoyed the explanations. Any subs better then the (3) I listed below for Home Theater? Long comment: My journey into speaker building started in the 90s. I went from Radio Shack books: Basic Speaker Building & Advanced Speaker Building to ordering Vance Dickason's Speaker Design Cookbook. I used to do all my calculations for crossovers & vents by hand from The Speaker Design Cookbook. Then I discovered computers! I now use Winisd and love it. I am not even sure I could even do the old calculations by hand it's been so long! Side note: Most modern subs have too high an FS for car audio use and do not model well for home theater. Have you also found that to be true? The current top performs with almost flat response down to 20hz in a 4+cu foot vented box are: 12" Alpine Type R W12D2 (4.25 cu foot tuned to 20.7hz with an F3 of 17.9hz - models the best out of the three) 12" Infinity Reference 1262W (no longer made - 4.56 cu foot tuned to 20.7 with an F3 of 19hz) 12" Rockford Fosgate 12P3D2 (4.7cu foot tuned to 21.07hz with an F3 of 18hz) I have modeled the popular Stereo Integrity line and none of them compare to the top three I mentioned above. Even their 18" HT 18V3 in an 8cu foot box tuned to 22 hz starts dropping pretty sharply from 30hz down with an F3 of 21hz but it's response rises below 50hz then starts dropping at 30hz so it might have a bit of a bloated sound. Are there any good larger diameter subs that model as good or better then the Alpine Type R above but in a 15" or an 18"? I have modeled most of Parts Express Subs over the years and none of them match the (3) above. Also, I have had terrible luck with their quality control and engineering decisions that make no sense. Thanks again for the video.

[@DIYAudioGuy]

I have had good luck with Dayton Audio subwoofers they have worked well or me.

[@keithmarlowe5569]

You seem to know what your doing. I have a few speakers under my belt. I used manufacturers graphs for crossover point and suggestions for box volume and ports. Then forum and review suggestions, with a couple emails and phone calls to tech support. My first boxes are crap - drivers aren't recessed, not sealed properly - and they still sound really good to me. (builders bias perhaps) So I want to redo them proper and starting with winisd. According to winisd, those suggestions won't work. Between port noise, excursion, and port dimensions, I can't make it work out. Wait a second. Is it because I didn't factor in the crossover in winisd? P.S I had a 10 inch ported Alpine once upon a time properly powered. That thing would rattle windows as I drove by.

[@papergatorzfedducca7998]

How do you calculate/make a port in the middle of a box? I know how to do one on the sides, but somehow I don’t understand how to put one in the middle.

[@DIYAudioGuy]

If the port extends all of the way to the back of the box then treat it like two separate enclosures.

[@papergatorzfedducca7998]

@@DIYAudioGuydo you have a video on how to do it? I’ve been through your channel a while back looking but I couldn’t find one.

[@DIYAudioGuy]

Not a specific video, but if you treat it like to separate boxes with ports that merge together you should be fine.

[@jsteezy80]

@@DIYAudioGuy I have a box with a middle port that both subs vents converge into. Do you just split the area for proper calculation? Thanks

[@HighVybeTribe]

I've always wondered what the differences are using lets say a 2cu box tuned at 32 hz Vs a 3cu box at 32 hz for the dame size subwoofer 🧐🤔👍

[@DIYAudioGuy]

The bigger box is going to play louder, but it might also have a cone excursion problem at lower frequencies. Hopefully I'll get a chance to build a pair of boxes to test that out.

[@NicoRas-e9m]

Build the vent outside the box - simple

[@ryancossin6588]

This may be a shot in the dark but im lost with all the options of speakers and subs available today. I am looking for a budget set of 10s and speakers for my daughters car. Any advice on these and amps would be appreciated

[@DIYAudioGuy]

That may require a very detailed answer. It is a bit much for the KZbin comments section. Consider joining me here: www.patreon.com/diyaudioguy and I can provide more help.

[@DonnieMulligan]

Great Info! Keep it up!

[@DIYAudioGuy]

Thanks, will do!

[@AndromedatheBasshead]

I've definitely made a port too small for an enclosure I had. I was calculated to about 14in square per cube for a pair of high excursion 15s. It sounded fine til I got over 80% volume and then the chuffing became unbearable.

[@DIYAudioGuy]

Chalk it up to a learning experience.

[@601musik]

so if im limited in space, i should give up net volume and make sure the port area stays high. and when i say give up spac i mean specs may require 3ft and you may hace to drop down to 2.5ft3 ?

[@DIYAudioGuy]

Or you need to go with a smaller subwoofer.

[@brianlojeck]

I think I see the flaw in your "the vent does all the work" example. The cone moves. That creates a pressure delta inside the box. That delta draws air through the vent til the pressure is equalized. (Agree?) Like water in a hose, the excursion of the cone MUST move equal air to the air through the vent. X air gets pushed by the cone, X air must move through the vent. Otherwise the box would eventually become a vacuum or explode from overpressure. (Agree?) Thus, if you put your hand in front of the vent or in front of the cone, you MUST expose your hand to the same amount of air. Here's the difference: the cross-section of the vent is tiny compared to the cone, so the velocity of the air is much higher, and the moving air is distributed over much less area, so your hand is exposed to a higher percentage of the moving air at the vent.

[@DIYAudioGuy]

It seems counterintuitive, but the majority of the output comes from the port at the tuning frequency. Test it out for yourself. The cone will move less at tuning frequency. kzbin.info/www/bejne/o3m3eKp7fah2iNEsi=tLZ-aqKwFxZPQS_r

[@brianlojeck]

@@DIYAudioGuy I mean, in the end, this is simple physics... if something seems counter-intuitive, I suspect it means we're missing something. If you managed to get your hands on a high speed camera, this might make an interesting research project for your channel...

[@DIYAudioGuy]

@@brianlojeck I thought about renting one. As you can imagine, they're not exactly cheap. Plus they're very hard to use You've got to get the lighting just right. Everything you said in your original post is accurate If you were playing below the tuning frequency. Everything that I've said about how a port works has been known for decades. It's not new information.

[@brianlojeck]

@@DIYAudioGuy To be clear, I'm not saying it doesn't happen, or that you are wrong... but the most interesting science is found in the places where something doesn't make sense... and I have neither the expertise in the subject, or the big ass subwoofer, to solve the question myself. 🙂

[@BaddDukk]

Nice video. I agree with all you said. That bloke was correct though - it WAS DD that popularized that horsesh!t correlation between box volume and port area. It may not be on their site now, but back when they were relatively new and the hot ticket for extreme performance drivers, it was, and all the fledgling basshead wannabe's out there soaked it up and spat it out verbatim. For 20 years I have been hearing that shit. One can make that generalization if cone displacement is held relatively consistent, which may be applicable for a single product line or manufacturer but outside of all of that context, it is garbage. Anyway, another handy formula is VentArea = 0.02032* TuningFrequency * ConeDisplacement (inches). This gives the area in square inches for 5%Mach air speed. No need for exponential equations.

[@DIYAudioGuy]

All equations are exponential equations, the exponent is just equal to one.

[@PepijnHazelhof]

how about a car is a small confined space that is near air thigt with the windows closed how does this affect the sound quality?

[@linccc54]

What units are used for this formula? And is dv vent diameter or port area in in sq? I’m having a hard time understanding

[@DIYAudioGuy]

Dv is vent diameter. I I've got several videos that dive into the math and show the formulas.

[@rhkips]

I guess it just goes to show how out of touch I am. I had no idea people had drifted towards so adamantly trying to correlate box volume to port area. I don't even know where this concept would come from, it's just so far outside of basic box design principles... :\ Unrelated, but has anyone mentioned that your audio and video are way out of sync? Not a huge problem, just a bit disorienting.

[@DIYAudioGuy]

It's the software that I use to cut out the dead spots and the bad takes when I'm filming. I reached out to their tech support and they gaslight me and assure there's no way that their software would make the audio and the video out of sync.

[@liamkenny100]

If placement was a constraint, could you use and external port? Would be interesting to see results 😅

[@DIYAudioGuy]

That shouldn't make any difference.

[@liamkenny100]

@@DIYAudioGuyahh kk, just looked and jvc had something similar, gigatube or something marketing speil 😅

[@user-ij8no5zw6u-]

Actually it's not the Xmax of the bigger driver that call for a bigger port area.....its the motor force that the bigger driver typically has. More force energizes the port/sprint stronger resulting in bigger Xmax at the tinning frequency. But that is not the Xmax from the brochure, actually at tuning no speaker comes even close to the maximum excursion because of the motor force limiting factor.

[@DIYAudioGuy]

Yes, I agree. If you crank up the power you'll end up with more port velocity. This is just one more example of why the rule of thumb is so illogical. A 300w subwoofer in a two cubic foot enclosure can get away with a smaller Port compared to a 1500 w subwoofer in the same enclosure. But if you only gave the bigger subwoofer 300w the smaller Port would be fine.

[@theshark2804]

I have a 5.34 box for my dd9515. Want to tune to 40 with a aero port. What size port and length? Thanks.

[@Jaydogg209]

Flared port full length should be 6.6 for one 6" port or 14.5 for two 6" ports. Look up the measurements on precision sound port calculator.

[@theshark2804]

@@Jaydogg209 had to measure my box several times since its an l shape. Came in at 4 cubes net. So I believe 10inch would be a hood start now. I think it came in at 37-39hz. The test i did so far sounds amazing

[@rjthomasindyusa]

I'm building a ported box for a JL 8W3v3-4. It calls for a 2 inch ID port that is 18 inches long. It has a 90 degree turn. I looked at Parts Express and I can not find a the right port. Any ideas? How do you suspend the port in the box? Bracing? Thanks! Great video!

[@DIYAudioGuy]

You can get an idea of how I like to do it here: kzbin.info/www/bejne/q4XCoHSAgsShZ68si=XYXtm3I2ov2oASro Parts Express does not sell any port elbows. Not sure why they do not, there is a market for it.

[@rjthomasindyusa]

@@DIYAudioGuy How would you go about getting a 2 inch ID 90 degree fitting for the port? Your videos have been really helpful.... Thanks!

[@DIYAudioGuy]

@@rjthomasindyusa honestly, you should probably just buy some PVC pipe and see if you can find an elbow with a wide sweep. If parts Express isn't going to offer the parts people need then they'll just lose business to Home Depot.

[@SpeakerKevin]

Question. Why is it important to base port design on x-max, when the woofer hardly moves at the tuning frequency?

[@DIYAudioGuy]

That is a really good question. I'll need to do some research to see if I can figure out the answer.

[@EBMproductions1]

*So wait if max SPL at higher frequemcies is the idea then would a wider port be the way to go? And for max SPL at lower frequencies a thinner but longer port is key?* 🤔

[@DIYAudioGuy]

Neither. The output from the port is only relevant around the tuning frequency of the port. For frequencies that are higher than the tuning frequency the subwoofer cone itself is making almost all of the sound.

[@prodbykaioken]

I want someone to create a variable port tune box with no external parts. A true means of engineering

[@keithmarlowe5569]

I was about to say there is, then I saw "no external parts". There is an amazing sounding (I mean the descriptions sounds amazing, I haven't heard one) Subwoofer with 2 ports, and plugs that can be inserted to alter the sound.

[@sppb32]

I've been saying it for 30 years, port size doesn't have much to do with enclosure size (besides tuning frequency), too big of port it actual hearts performance since the subwoofer reaches it's mechanical limits way sooner than its maximum RMS handling, keep port air velocity as high as you can without having port noise

[@DIYAudioGuy]

Yep

[@killabee623]

I always based my port size on the woofer size.

[@hugofortuna6277]

But there is a formula in the loudspeaker design cookbook that does take into account enclosure volume?

[@DIYAudioGuy]

Nope.

[@JesseAdams-t4z]

I need help designing a box for 2 sundown u 15s.can you please help?

[@DIYAudioGuy]

I am not currently taking on enclosure design clients.

[@MrVolksbeetle]

What about passive radiators?

[@DIYAudioGuy]

I'm a huge fan of passive radiators. I've got several videos on the channel exploring them. The Big downside is the cost.

[@MrVolksbeetle]

@@DIYAudioGuy except for the weight difference, I’ve used blown and/or old drivers as passives. Ripping the magnet off and preserving the spider seems to help. I feel certain that’s all kinds of wrong but, it’s worked for what I’ve needed them for.

[@BrianWaller-qe7gr]

No replacement for displacement

[@Petethebuilder]

If my port is supposed to be 20 inches long by 4" diameter can I just do 2 10"x4" ports or 4 5"x4" ports.

[@DIYAudioGuy]

kzbin.info/www/bejne/eGHGooaqaLeBgZosi=J7MsbnohYqNq6GFb&t=180

[@arthurwatts1680]

The only magic numbers I need are this week's Powerball numbers ;) (seriously, do you have them ? thanks in advance !)

[@DIYAudioGuy]

I have them, but I can't get them to you until next week.

[@arthurwatts1680]

@@DIYAudioGuy well played, sir.

[@CrystalClearSQL]

Technology has changed in the past 50 years. Drivers aren't even remotely the same.

[@DIYAudioGuy]

I remember in the '80s when car audio subwoofers were just big PA drivers.

[@lunam7249]

wisdom!❤❤👏👏

[@massivehertz3869]

So, how does this apply to a 6th order when the rear chamber has a port well under the recommended port area? For example, my rear chamber port is 42 square inches and 7.5 cubes of air space on 2 18's with right around 5k rms. Is this not good?

[@DIYAudioGuy]

I'm not an expert on six doors, but the principal is the same. You size the port based on the performance of the subwoofer not on the size of the enclosure.

[@massivehertz3869]

@DIYAudioGuy my enclosure was designed for me by Drew Jones. I just built it. However, I did question how small the rear port was considering how large my subs are, But I was told he is the best in the business, so I built as designed.

[@BenHeien]

So they don't take the woofers displacement/xmax or fs into account?

[@DIYAudioGuy]

The "squares per cube rule of thumb" does not take any of that into account.

[@Mastermindyoung14]

So an RE XXX 15" needs a gigantic port size because it has a huge xmax?

[@DIYAudioGuy]

Yes. And for a big monster subwoofer like that space is going to be your limiting factor.

[@michaellarcom]

Is there a rule to thumb if the port could be on the back side of the box the top of the box coming out the side of the box is there a rule to thumb on Port location? Vs facing?

[@DIYAudioGuy]

If you were to take measurements in an anechoic chamber the port direction is not relevant. But in the real world the port will interact with nearby walls and that will vary depending on the room or car.

[@keithmarlowe5569]

I'm only passing what I have read numerous places. "For rear ported speakers, distance from the wall should be equal to the port diameter". That's it. That's from a good many people who know what they are talking about. As far as sound, they say it doesn't make much, if any difference.

[@BackAgain-i8t]

Use a sonic exciter

[@nikleiser5888]

Have you taken the fact that longer ports are less efficient due to air friction into consideration? that's why PROs use round ports (best ratio of portsize and air friction).

[@DIYAudioGuy]

I'm working on a video to debunk that myth as well. Make sure you hit the subscribe button so you don't miss it.

[@nikleiser5888]

@@DIYAudioGuy I am a subscriber for years already, but notification system is getting worse and worse by the day....not just on your channel.

[@DIYAudioGuy]

@@nikleiser5888 I feel like I've picked up a college minor in understanding KZbin's algorithm. It's all based on probabilities and likelihoods. If the algorithm says there's a high chance you're going to watch the video, then it shows you the video. If it thinks there's a low chance you're going to watch the video, it just doesn't show you the video.

[@BlueTegu360]

I've been saying this forever and always get told I'm wrong lol.

[@craigreustle2192]

What happens if you design the enclosure to be 100% port? Can you just put the sub at the end of a large tube of the correct length?

[@DIYAudioGuy]

That sounds a lot like a transmission line.

[@Robertb00]

Term pro software great investment for me.

[@Carl_Jr]

It's a rule of thumb not set in stone. Kinda like

[@forog1]

Thats why I don't do ports anymore. Just a big, massive ugly box. The bigger the box the harder it is to make it stylish and every time I look at a huge sub box with such a huge box I just feel I'm trying too hard and over the years I starting loving SQ over all else so big ported boxes sound bad to me at all listening levels so I tried sealed and it was great very accurate beats but the loss in the low end didn't sit right with me so I went with the passive radiator route doing nothing special but drilling holes for it in that same sealed box and boy is it night and day for SQ over the ported box.

[@DIYAudioGuy]

I'm a big fan of passive radiators.

[@glynnherron8065]

Port all day ftw

[@ladjkaoz]

nooooo i feel like a 5yr old walking into presschool🐒😶

[@mullinperformanceaudio5902]

Math is hard.

[@DIYAudioGuy]

Yep.

[@lunam7249]

sorry it is...but your not alone....calculus1 has a 92% failure rate!!!....einstein failed math classes more than once...try pit bull tenacity..never give up!

[@rcflugzeit8420]

😂😂😂let's try the impossible! It must be possible to find the perfect compromise that everyone can agree on. I don't want to live in a world where there are physical limits. When something goes up, does something else really have to go down?🤔

[@DIYAudioGuy]

🤣👍

[@PunisherOfDeath101]

Build sealed and save yourself the bs. Need more output? Add more drivers. Still going to be under the cubic ft of single ported.

[@DIYAudioGuy]

This video really seems to have brought out all of the sealed subwoofer fans.

[@hamiltoncouple01]

Exactly. Better power handling and less distortion.

[@Obsfucation]

Justin, please refer to drivers as…. drivers. They’re not “subwoofers”. That’s a finished system with a driver in a box for VLF reproduction. Sorry to be pedantic but, let’s get the terminology correct.

[@DIYAudioGuy]

The problem is that most people do not understand the distinction.

[@Obsfucation]

@@DIYAudioGuy You may not appreciate it or want it but, I see your role as a teacher. You are making a difference. Teach them the distinction. It’s not controversial or political; it’s just good info from your soapbox.

[@williamlineiii9372]

I'll take ported or sealed, sealed sounds like shit to me.

[@Steve-nu9op]

sealed ftw ! ;)

[@DIYAudioGuy]

That debate has been raging for decades.

[@Dingleberry1856]

It’s no debate. Sealed FTW

[@DIYAudioGuy]

@@Dingleberry1856 I've never done a sealed versus ported video, I think it's time for me to make one.

[@johnnycorn7225]

Yup, after 30 thirty plus years building enclosures and trying them all, sealed is the winner. Let me explain why it's because winners go the extra mile work hard and put double the amount of effort into going after what they want. And that means you can have double the amps and double the subwoofers in the same airspace ( say 2 12 s in 4 cubes ported vs 4 12s in sealed, both calling for 4 cubes needed). And I don't need to lecture anybody about the response curve being uneven( and please don't say tune super low and run a big box) because that's my least favorite sound of all. I listen to music and I'm a musician also, so timing is everything to me and I'm used to pounding my own beats out through horn loaded monitors so nobody is fooling me. Your loose rubber band floppy bass doesn't impress me. And now on to my 4 12s SEALED I. Same 4 cubes. Since I worked doubly hard I can afford double the subwoofers and I can run four of them on twice the power of two, while cutting power compression in exactly half maximizing my output and sound quality. I also run high power on 4 ohms, which is definitely expensive but shows up big time in your sound quality as well. I have done this several times and the four sealed on double the power in the same enclosure beats the snot out of two ported subs of same type, and your free to get really good subs optimized for sealed like si SQL or fi q for example. If you think I can't get loud with four stereo integrity 12s sealed on very high power your wrong. Two ported might barely if at all peak higher in a 6-10 hz super narrow bandwidth but overall, from the very lowest to top of used sub frequencies, the four sealed mercilessly obliterated the two ported in timing impact and clarity.

[@clarkgriswald1768]

Double the subs in a seal enclosure vs same ported enclosure. Bass for space

[@bassjasinski]

Ports are too complicated so stick with passive radiators 😂

[@DIYAudioGuy]

True story

[@dennycote6339]

Ive been knocking this rule of thumb for ages. Its a trash idea.

[@niiicetoyotaandfummins5956]

I just made a tiny box and my sub still works imagine that

[@DIYAudioGuy]

Yep.

[@slickwillybudgetking]

Are you familiar with triticum port volume calculator?

[@DIYAudioGuy]

I stumbled across it when I was originally researching this video probably over a year ago. I can't remember if I ended up with a dead link or a broken Google sheet.

[@Zockopa]

I design speakers since the eighties and never heard this nonsense.....🧐

[@prodbykaioken]

It’s called advancement in technology

[@hamiltoncouple01]

Same here.

[@matt6951]

Who's building a box for a 600 watt sub? 😅

[@DIYAudioGuy]

I do it all the time. The power rating on the subwoofer has nothing to do with whether or not the subwoofer deserves a decent box.

[@Sqnutt]

I still own a pair of DLS w310b rated for 150 watts each, paper cone reinforced with carbon fibre , they sound great in 2.6 cuft tuned to 36hz I love em

[@KamilK3]

Your audio in not in synch with your video

[@DIYAudioGuy]

Yep, it's a software glitch.

[@johnwhite5818]

Imagine how many views you get if you If you came up with the way to actually build these speakers and compare them side-by-side Including An actual audio example.

[@DIYAudioGuy]

Yes. That is the goal. Unfortunately material costs make it difficult. You can help: patron.com/diyaudioguy

[@randomtube8226]

I just use the same size diameter port as my subwoofers cone. Box size and port length are the variables. I don't care about box size. I will turn my entire trunk into the enclosure. Sorry back seat people. Your groceries will have to go inside the enclosure. Can't promise no tossed salad and scrambled eggs from the bass 🤣

[@DIYAudioGuy]

I am listening.

[@subbassrules]

I don't think you even understand how huge a 12" vent tuned somewhere around 30 Hz needs to be.

[@randomtube8226]

@@subbassrules I get it, in a vehicle it's tough to fit anything too big.

[@subbassrules]

@@randomtube8226 Also if you attempted to "just use your trunk," you wouldn't be making an enclosure that operates like a vented box. It would be more like a bandpass which may be why you are thinking this works well. You can achieve high SPL levels with a bandpass. Sound quality is generally garbage if you do this except on a song with frequencies close to what your trunk is tuning the box to.

[@subbassrules]

Say you have a 12 cubic foot trunk with a sub in a 2 cubic foot sealed box in it. If you cut a 12" diameter hole in your rear package tray, you would end up with an effective tuning of 60-65 Hz. This could work, it depends on the subwoofer. This is a fairly low tuning frequency for a bandpass though. And if your box also has a port, you now have a series tuned bandpass which is very hard to build properly. It's not a build it and run it design. I'm not trying to be a jerk, just explaining what is actually happening if you try this. 99% of the time it won't sound good.

[@albaanisissi702]

Do you really have any real life data on ports or just the theory? port lenght is way way more important than the cross section or the tuning. Some chuffing is good on the lows, more wind but port needs to be loooooooong. Make a video how mutch you lose output with double/triple baffle, you might suprise yourself....

[@DIYAudioGuy]

Yes, tons of real life data. I test and measure every enclosure that I build. I've built a few that chuff. I promise you It sounds like absolute garbage. Port length, Port cross-section, and tuning, are all mathematically related to each other. One is not more important than the other.