Greetings- This seems to be the place to gather information on DIY subwoofers, and since I am planning my first project I turn to you guys for some advice. My system is for music only. Current system consists of ACI Jaguar speakers,(factory built) McIntosh MC-202 amp, McIntosh C-15 pre amp, Myryad CD player, assorted other stuff. The Jaguars are great, but I always intended to use them with a pair of subs. I have outlined, as best I can, what I am looking for in my project. Here it is; 1) Fq response that is more or less flat from 20-80 hz in room. I will be using a Marchand XM-9 crossover (24 db/oct) between the mains and the subs. I would like to try and use 80hz, but if that is too high, I could drop as low as 60. I want to try and free up the midrange a bit on the Jaguars, and relieve some congestion that I hear in the lower mids. I do not want to use any eq. 2) Relatively modest SPL. I am absolutely stunned by some of the numbers you guys are getting from your DIY subs. I can’t even imagine what 120 db @ 15hz must be like. My listening rarely exceeds 90db, and is usually confined to 75-85db. So, for adequate headroom etc. I would like my subs to play cleanly to around 105db @ 20 hz. (in room) I won’t use any performance beyond that, and am unlikely to even go for 105. But, I do want it to be clean, and very very low distortion from 70-95 db, again 20-80 hz. 3) Size: I want to keep the enclosures down to around 100 lbs each, probably in Baltic birch ply. I figure that to be about the max. that I can move on my own with a dolly and not strain the back. Given that weight restraint I would set 8-10ft^3 gross box volume as my limit. 4) Wood box; I don’t think tubes are for me. 5) Front firing. I want to see my drivers! 6) Budget: No more than $300 in drivers for each sub. 7) Power: I want to use a standard audio stereo amp, something like 250w into 4 ohms. No fans, no pro amps. I have a good Rotel that I can use for now, eventually to be replaced with an older Bryston or similar. 8) Room: I am moving in 4 months, so I don't know what room these will be going in, but it will probably be a normal sized "average" living room. Say 10 by 20? Certainly not a huge room, but not too cramped either.... Ok, so with those goals in mind I have read and read as many posts as I can find here. There is a tremendous amount of information in the archives. I think a sealed enclosure with a low Q is what I want, since this is a music only system. I have modeled several designs, as best I know how, in WinISD, and the sealed boxes always seem to be 7-8 db down @ 20 hz. Given careful room placement can I hope for flat response? I know that this is totally room dependant, but in your general experience what kind of gain should I expect, in room, from 20-30hz? I still have many questions. Most importantly I guess, is what size driver, and which one to buy. Re size, 10, 12, 15 or 18? For that tight natural music bass sound I am looking for, what size should I be considering? Can musical bass be had out of an 18” driver? Would say twin 12s or 10s be better than one 18? (twin 12s or 10s in each sub, or 4 total for the system) I can’t remember seeing a main full-range speaker that relied on an 18” woofer, in fact the biggest woofer I can think of that I have seen built into a speaker would be the 15” used in the B&W 801s. Should that be telling me something? Drivers that seem to stand out as being good candidates are: ACI, NHT, Aidre Tempest and Maelstrom, and some of the drivers from Stryke. Ok, this is way way to long already. Any advice that can steer me in the right direction would be very much appreciated!