I've recently managed to clear out my workshop and end up with a fair bit of free time, so I've decided to finally try and build a rig. I end up with a lot of extra sheets of ply from work so it seemed like it could be a good way to use it all. The problem is, while I have friends who are more literate in this I don't know too much about building one - although therein lies the fun! I'll be asking for their guidance along the way but wanted to post here as well to take my own initiative a bit.

After some minor research I figured I might (over a fair bit of time I imagine) aspire to build a rig consisting of the following:

4 x SKRAM 21" Subs (ground coupled)

2x Dual Reflex 18" 

3x Horn Loaded Cubo kick 15

2x tops tbc maybe SMT 212? OR MT121?

Any glaring issues with this? I think my friends can help me with driver recommends but seeing as the bulk of the timber will be free I think it may be worth sinking budget into that. I was considering a hand build but I suppose if I can stretch it CNC would be preferable. 

any notes/advice/pointing out any idiocy is greatly appreciated! It's a big learning curve but looking forward to it.

Thanks

i'd choose one or the other for your sub-bass. 

Also about the rest of it, theoretically sounds ok just a lot of preference, like the cubo kicks, do you like kicks that are thump your chest, that leans towards Pure horns I guess, bandpass more punch you in the face, ex: em15 , or tapped horn for smooth, even response and fidelity (ksthr-15). Cubokick a horn assisted tapped or whatever seems pretty easy to build, but also sort of middle the road.  Same for those tops, a lot of the sonic character will come from drivers being used, so you can either decide which designs you like and get the speakers thst would work, or get the speakers that would work first and look for compatible design. 

If you have access to nearly or totally free building material, make prototype cabs and then build out your preference

skram - 20-60hz

reflex - 50 - 120hz

cubo - 100-250hz

smt212 - 250hz+

It's highly likely I have made a mistake here lol and yeah I did wonder about subs doing most of the legwork already and phasing issues etc.

I think you are right, building material is essentially free so the main focus really is the drivers. I just don't know much yet about to what scale the shape of one cab vs another affects acoustics. Like I want it to look cool obviously haha but it's super important to me that it sounds great too. It would mainly be for tekno, hard house, hardcore etc if that affects any recommendations, although it would be nice to have something that can offer some diversity across multiple genres I suppose! I guess I need to consider amps and other bits and bobs as well into my budget but I can get to that later once the actual cab designs/drivers are settles I reckon

Thanks

EDIT:

After some more thought/research it seems that while it might be possible with proper DSP tuning to have a  4-way system work well perhaps for someone with my level of experience (zero) dropping the reflex for just the SKRAM will provide enough of that 'warmth' and for the music it will mainly be playing perhaps the punch of a SKRAM suits better anyway?