Your ported box will fail!

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In this video we bust the biggest myth in car audio, the subwoofer port rule of thumb that you use to design your vented enclosure is wrong. Do not use the enclosure volume to calculate your port cross section.

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Chapters:
0:00 Introduction

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[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.

[ralphlongo]

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. 😀

[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 Youtube.

[arnicus]

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! 🤔 😳

[Bassotronics]

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

[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.

[CarsandCats]

Sealed box smiling and eating popcorn.

[JJ-kfuk]

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:)

[herrtrigger]

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.

[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.

[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...

[TimpBizkit]

Usually I model the SPL at maximum excursion somewhere, then search the peak air velocity for the port and try and keep it under 25m/s, though usually this happens at tuning so if this is impossible I will check what the port air velocity is for most of the pass band to see if it is acceptable.
It becomes a battle with some of these high displacement powerful magnet motor drivers common in high end SPL car audio. They are really more suited for horn enclosures, and in the ported enclosure size, the port is usually too long or skinny, but they can be used with a suitable passive radiator system.
I've found with PA woofers in large boxes, it is EASY to get the port dimensions needed, but with the high power density SPL car woofers, you either end up with a squiggly wiggly little tube that can barely pass any air, or filling up most of your car with flexible drainage pipe.
I wonder if it's possible to trap a denser than air gas in or around a port. Something like perfluoro-butane sealed in with a loose flexible membrane on either side (ideally something that doesn't rustle and flap like a plastic bag). That way the air is denser and the port can be shorter.

[OK-stst]

You should make a video on a 4th/ 6th order box, or infinite baffle. You explained this great!

[johnj]

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

[JoeJ-]

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!

[veridico]

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

[shawnsanderson]

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.

[reinekewf]

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.

[stevenPounder-pb]

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.

[Messenger]

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