Originally Posted by Gary Mertz
Any thoughts or threads to which I can be directed?
Welcome to the rabbit hole--I'll be your tour guide,
As with anything that you build, be it subwoofers, speakers, amplifiers, car engines, furniture, houses etc.--the best thing you can do is educate yourself about how they work. For example, when you purchase a driver you'll get T/S parameters on a tech sheet and it is wise to know what all those numbers mean before you purchase the driver. Learn about the digits, play around with them with software, there are different software packages and they go from the rather simple (WinISD Pro) to the very complex (Horn Response or Abakak) Horn Response is generally used to design front loaded, tapped or rear loaded horns but can also be used for dead simple alignments like sealed or ported.
Play around with the software, make the box larger, make it smaller, screw around with the port length and surface area and watch factors like first resonance (very important) for the port selected vS meters per second of airflow. Note how as the box becomes larger, the port length shrinks (a good thing) and as the port(s) become larger in cross section, the meters per second of flow decline (also a good thing) Gain an understanding how they relate to each other and why the compromises exist when building such a thing.
If you built car subs back in the day, that helps quite a bit because you have an idea how the game is played. You will understand box size VS output, how to brace the box and basic EQ when dealing with subwoofers. Very easy to spot on the DIY side of things when a person creates their design if they have experience with subs.
Not to scare you away but--you need to educate yourself on the operating of subwoofers, figure out what your demands are and put them in numbers. This way you can have solid numbers to aim for in your design and the software data will make sense. Once you have those numbers, then it is time to learn about different alignments to get what you want. Consumer subwoofers have to sell so they can make a living--as with all things. For this reason, you generally won't see more fringe designs because of size, build complexity, weight, excess shipping charges because of that size/weight and finishing costs. If you do your research and want a dual 21" PA driver in push-pull mode loading a tapped horn or transmission line--you won't be able to go down to the audio shoppe' to physically listen to one because 500 pound subwoofers the size of a fridge are not big sellers.
It is a very good idea to have a strong working knowledge of various forms of EQ be they parametric EQ dynamic limiting EQ and various filters. No matter what alignment be it sealed, ported, bandpass, transmission line, infinite baffle, LLT, front or tapped horns you will require some form of EQ to make it work properly in your room. Each alignment has possitives but they also have negatives so choose wisely and get the one that works best for you and your requirements. Be aware some of those alignments get huge--I would love to have four LLT push-pull subs tuned to 9Hz with massive ports but my wife is not a fan of 80 cubic foot subs in the house.
Once you find the "perfect" alignment, figure out the drivers, ports (if required) and all that jazz--give a week of "cooling down" period and attack your design critically to make sure the downsides can be lived with.
To the OP, if you want to find out about DIY--it helps to post in the DIY side of things.
The defacto standard for subwoofer DIY is a guy named Ricci who builds insane levels of subwoofers to have EDM parties in giant warehouses. He tests things with amplifiers used in stadiums, builds horn loaded beast subs and has the skills, test equipment and abilities to properly test drivers, enclosures and their capabilities. THIS is the best place to start, read subwoofer myths to start--you said "musical sub" so you really need to start there!
He has tests stretching back years, they can be consumer subs, DIY subs and custom builds so each to compare to each other.
Another good site to check is the forums over at DIY Audio--if you want to really fall down the rabbit hole, they design their own amplifiers also--you can really geek out there. Be the first on your block with a 1,000 watt subwoofer tube amp because... you can.
If you want to learn Horn Response and build massive horn loaded subwoofers IMAX or stadium style, the DIY Audio people have plenty of tutorials explaining how to use that powerful software to get you there. The rabbit hole runs deep on that side of the internet.
Hope that helps, be aware you might spend far more money to save money than you ever thought possible. You might find yourself seriously thinking about full DSP stadium amps and should you run 30 or 50 amps of 220V to your living room to feed 4 to 16 channels of stadium subwoofers. Be careful, drywall does break and bad things happen to buildings once you find their resonant frequency (bad things happen then!)
Once you are done with data-bass, check out the DIY side of this forum and that will help you define your wants VS needs. At least you'll understand the tech and terminology of DIY once your trip through data-bass is complete. Ricci has all the cool toys so enjoy the ride--but always keep a sense of reality. ZOD Audio is just Ricci's "brand" with a bit of tongue-in-cheek humor--I'm not worthy. Enjoy the read, figure out what you want/need with the numbers and start making sawdust. Good luck!