You can actually buy speaker design software, where you enter parameters such as ampage, frequency response, porting, cone size etc and it will give you a number of options and then schematics.
I tried this years ago, before I discovered just how much research goes into nearfiled design.
Ended up with some good hifi speakers though.
That`s why I recommend accoustic design. It`s not something you can just "pick up". It`s not like building a table out of some bits of wood, or an average ported speaker box, you are actually dealing with some very complex physics, air/sound pressure/frequency to power ratios. Advanced baffling techniques, material properties, wave-guiding (modern waveguides are the product of decades of research, so you will inevitably have to purchase the waveguides [for around £100 and up a pair] as to make your own would involve getting hold of copyrighted and patented designs (costly/impossible), and also some kind of plastic moulding system).
If anyone could do it, anyone would be doing it.
It depends on your commitments.
You could spend 3-4 years trying to build the perfect nearfield. And hence lost 3-4 years of production time (unless you have decent nearfields already)
OR
Buy some proper nearfields, made and designed by a team of qualified accoustic engineers with years of experience under their belt, and manufactured to very exacting standards.
However, some useful websites to hep you on your way
http://www.partsexpress.com/speakers...TOKEN=52814673
Useful quote from speakerplans
http://www.diyaudio.com/forums/forum...php?forumid=54
http://www.diyaudio.com/forums/forum....php?forumid=6
http://www.diyaudio.com/forums/showt...hreadid=126586
Here is a website where you can purchase the plans or kits to make a pretty good monitor/decent hifi
based on the Ai ES10 monitor/speaker.
It`s a pretty good design, based on a pretty good speaker and has pretty good reviews, however I`m not really sure it rates up to a decent nearfield standard. It might match the same performance as a low cost nearfield monitor, such as a M-Audio nearfield.
http://www.gedlee.com/Summa.htm
another link to a high spec, well rated audiophile speaker, although again, I don`t think it is nearfield standard judging by the discussions about mid range performance
http://www.nutshellhifi.com/Ariel.html
more stuff
http://www.bobhodas.com/pub1.html
Personally I think the best success you will have is to use full range single driver based designs.
Audio Nirvana speakers are amazing full range drivers. Dr Vogts speakers have been used as monitors in high end studios for a long time.
He has stopped manufacturing complete setups now, as his driver sales alone are making him lots of money, however, he gives the cabinet designs awaw for free with the purchase of the drivers.
This will be your best bet, you`ll be able to build your own studio standard (in design anyway) monitors, but won`t have to go through years and years of R&D to come up with anything worthwhile.
Pricing looks like it will be about the same as buying mid range monitors, but it might be more satisfying
http://www.commonsenseaudio.com/nirvana.html
I`ve heard some of the original built monitors by Vogt at Angel Studios in london, they were luvverly, although they were mid field, rather than nearfield, but there are designs there for nearfield speakers.
Another good general guide about studio monitoring
http://www.soundonsound.com/sos/jun0...s/monitors.asp
Some great designs here,
Some of the performance curves look reasonable (although performance curves alone, don`t really tell you the whole story)
http://www.htguide.com/forum/showthread.php4?t=28655
That`ll do ya
Good luck