I started building speakers before the internet was popular, so the vast majority of my info came from books, articles, and trial & error. The Loudspeaker Design cookbook and a calculator were my two most valuable resources. Good kit speakers may have existed, but it was much harder to get information and feedback about them. I can only imagine what the internet can do for you now.
Whether to build your speakers from scratch or from a kit is a personal decision you'll have to make....not all that different from the decision to build a guitar from scratch or from kit. A kit is undoubtedly easier and is a known commodity, but is limited to what's offered and limits the learning experience to a few basic assembly tips. Building your own can be extremely rewarding, can yield astounding results, and will undoubtedly teach you a ton of new stuff you may have not known before. It's not that hard to make a decent sounding pair of speakers from scratch on your first attempt that eclipse the vast majority of mass-fi junk found in stores....study up a little on the basics of crossover networks, enclosure designs, and how the Thiel Small parameters effect the optimum enclosure requirements.
I imagine that the supplier names have changed, but good suppliers are important. Zalytron was one of my favorites....Elliot was a tremendous asset to me, and I believe he's still very active. Madisound, Gold Sound, Parts Express, and others were also good suppliers for me.
I'm also sure that the component brands have "shifted" over the years too, but 15-20 years ago, there were great drivers available from companies like Focal, Dynaudio, Morel, Seas, Vifa, Scan Speak, Audax, Seas, among others. Parts Express seems to have done quite a bit with their Dayton line, but I haven't tried any of their drivers.
Speaker sound is extremely subjective, so don't let someone who can boggle your mind with information be overly influential about what you like. Let your ears decide, but be open minded about might be "better" or at least different.
For beginners, it's easier to make a simple two way speaker sound good than a more complicated 3-way.
"Watts", size, and powerhandling have nothing to do with how a speaker sounds, but it's ok to recognize the physical limitations of smaller drivers.
Speakers are a system of components....good components reveal the weaknesses of lesser components, so you'll only be as good as your weakest link. Use good components, and focus on all 3 main aspects of the system...drivers, crossover, and cabinets.
Having control over your crossover design gives you a lot more flexibility to tweak expensive drivers that may not always behave as expected. If you buy an off the shelf crossover, you're fairly limited unless you're willing to modify it, but letting other's handle the design certainly simplifies the project. It really depends on how far you want to go.
There are pros and cons with every design choice. Go with what you like, what you know, or what makes sense to you.
Don't be afraid to experiment....it's how you learn. You can start with modest crossover changes to see what happens. Get your feet wet and go from there.
There are many little tricks that may or may not make an audible difference by themselves, but if you do them all, you're far more likely to get noticeable improvements that reveal other differences. Use good wires, good inductors, good caps, bi-wire or tri-wire the crossovers.
Inductors have a magnetic field. Place them away from woofer magnets, and far apart from each other i f possible. Set them at 90° to each other to reduce interference with the magnetic field.
Put the tweeter and mid/bass drivers in as close proximity with each other as physically possible....you're trying to create a single sound wave from more than one driver. If the driver's centers are farther apart than the physical wavelength of the crossover point, it'll behave like two sound sources instead of one. ie: (IIRC) 2000 hertz = 6", 1000 hertz = 12", etc., meaning that if you choose a crossover point of 4000 hertz, you'll need to get the driver centers 3" apart, which is darn hard to do. The lower that crossover point, the farther apart you can place the drivers, but you'll also be taxing the tweeter as you go lower, so you'll need a tweeter with a lower resonant frequency or a steeper crossover slope to reduce the amount of lower frequencies the tweeter sees. Some drivers have truncated mounting flanges to help with proximity issues.
Unlike speakers for live music production, home "hi-fi" speakers are intended to faithfully reproduce the sounds that are played through them, with as little sonic signature as possible. Use inert materials that are acoustically neutral, like MDF, solid core ply, high grade dense ply, etc. Over build them, and brace them throughout. Use lots of wool, dense foam, acoustic stuff, or compressed polyester to absorb internal resonances. You can also paint the inside of the enclosure with a boroscillicate compound to help deaden vibration. Suggestions to use old pine, etc., mainly apply to guitar, organ, or other live music production speakers where a sonic signature is desired.
Avoid building speakers with parallel walls as much as possible. You can hide non-parallel wells inside the enclosure to make it easier to finish them. Definitely harder to build but will sound less like sound coming from a box.
Seal the seams with caulk to prevent air leaks. Air tight enclosures are a good idea on any speaker, but even more so if your design is based on a totally sealed enclosure.
Make the front baffle as diminuitive as possible to reduce deflections. You can soften the corners, and/or add sound absorbing materials to the fronts.
Woofers are often pretty stiff when new, so give them a heavy work out before doing any critical listening or mods.
Good capacitors will benefit from a burn in time. Give them a heavy work out prior to doing any critical listening or changes based on what you hear. Many will start out sounding a bit shrill, then go slightly dull, then after a few hours of use start to clear up nicely. That's when you can finally evaluate what you've got.
Don't be discouraged if "version 1" isn't everything you'd dreamed it would be...that's only a starting point. I've spent months and even years, making tweaks to improve a design. It can take time to be certain what you'd like to change. "Revision 47" will undoubtedly be better sounding than "rev 2". Be patient.
What you hear is a culmination of the music being played, the acoustics of the room, the system you're playing it through, and finally your speakers. It's best if you can evaluate your speakers through a more neutral room, system, and music source. Well recorded voices, or solo instruments are often a better reference for evaluating what your speakers are doing than your favorite heavy metal band.
That doesn't mean you need to become a classical music buff, or need to build an anechoic chamber, but be conscious of the quality of the initial recordings and your surroundings before making drastic changes to your speakers.
...to be continued...