You can do better...
Hi joetech
When I first started building speakers about 4 years ago, the AR.com was my first effort. The Madisound kit was an easy way to start because they sold an assembled crossover at a good price. It’s not a bad speaker, but for the same price you can do better. I can give you links to designs that I prefer over this one.
The Peerless 6" woofer is a good driver. The problem is that the manufacturer no longer makes it, even though it was a big seller. Check with Madisound and Parts Express to see if they still have some available.
The Peerless tweeter is not good. I would avoid using it. It has a large 5-6 dB peak that begins around 10 kHz and continues on up to 20 kHz. It’s more like a wide shelf than a peak! I could easily hear it as a bright irritating tizziness that I could not eliminate with any tone controls. There are many other good tweeters for $30 or less that are much smoother.
The AR.com crossover lacks any correction for the unpleasant sound coloration caused by narrow speaker cabinets, called baffle step. This baffle step compensation (BSC) corrects a nasal sounding exaggerated midrange. A lot of commercial small 2-ways fail to address this problem at all! To learn what BSC is see
http://www.quarter-wave.com/General/BSC_Sizing.pdf. If it is present, BSC smoothes out the all-important midrange, and leads to better bass response. It will lower the sensitivity of the speaker somewhat, but it is worth doing.
If you are interested, I can email you a schematic of a corrected crossover design for the AR.com. It includes BSC and filters out the harshness of the tweeter. It improved my AR.coms significantly.
Your ideas about relocating the vent sound OK. If you want to do a slotted port, why not increase the height of the cabinet so the distance from the bottom of the woofer to top of the slot is the same as the distance from the woofer to the lower edge of the cabinet. That way you could mount the crossover on top of the “roof” of the slot.
You can mount the crossover anywhere so long as you keep the inductor coils about 3-4" away from the woofer magnet. That big magnet can interfere with the inductor coils. If you hang it from the “ceiling”, mount everything well. I use ¼" pegboard with cable ties to fasten the inductor coils and large caps, and hot melt glue or epoxy for the smaller bits. I twist all the leads together through the pegboard holes, and solder them on the backside of the board. I drive some short screws through the board into the cabinet to mount it all. It may seem like over kill, but when I used easier short cuts, stuff did come apart.
I would avoid using solid wood in speaker cabinets. Solid wood resonates more than MDF, and can make cabinets that “ring”. MDF is essentially free of resonance because it is fine sawdust glued up under pressure – it lacks any grain structure. All the best speaker cabs seem to be at least ¾" MDF. If you want the look of hardwood, cover it with veneer. Solid wood also changes shape and dimensions as humidity changes through the year. So if you make a cabinet that combines solid wood and MDF you may have cracks, split joints, or worse when the weather gets humid. ½" MDF and ¼" plywood may be OK, but you have to be careful how you attach the ply to the MDF so expansion doesn’t cause damage. I don’t know how that is done, but more experienced wood workers could tell you.