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
MDF: Material of choice for the DIYer. Heavy, fairly easy to work with, and better characteristics than hard wood in term of resonance. Depending where you're from, the cost for the MDF (medium density fiberboard) can be between 12-40 bucks, and can vary with your cabinet design. The thicker the better. 3/4 inch is widely available here, so I often double it up for 1 1/2 inch width. However, this stuff is MESSY. Its made from compressed sawdust, so its a good idea to work in a well ventilated area. And I STRONGLY suggest wearing a painters mask. It helps a lot. Also, its not a bad idea to have carbide bits, and a few of them for each tool. MDF is extremely hard, and wears bits down like none other.

Tools: Basically a must have: A router (though a dremel or Roto-zip with router attachment can be substituted), a table saw (unless you dont like straight cuts), plenty of clamps, and a drill or drill press. Again, carbide bits and replacement bits are strongly suggested to have on hand.

Putting it all together: There is some debate in this area. For attaching the driver, t-nuts and threaded screws seem to be the way to go. For laminating boards together, any strong wood glue or Liquid Nails will do, although I like to use "Rue glue". I get this from a nearby woodworking company. It dries slightly rubbery, giving it excellent damping, but once it dries, you're more likely to rip the face off of the MDF than you are to break the bond. If you are going to use screws to hold it together, I suggest drywall screws. They have a bigger thread, so they grip the MDF better. All vented cabinets must be sealed very well in all areas except the port. You can use your choice of materials for this, although I and many others use silicon caulk. Its a good idea to let this dry first, because the fumes can damage the driver. Also, you need to line the inside of the cabinet. A heavy felt can be used, but I prefer to use acoustic foam (the egg-crate stuff). It helps that I get this extremely dense foam for free from "Hi-Tech Packaging"; a company who my father, a UPS man delivers to.
Also, if you want to keep the cabinet from resonating, you're going to have to brace it, and the bracing mustn`t effect the wave guide or cause standing waves within the box . Be sure to compensate for all bracing when calculating the final volume.

Port tubes can be made of PVC, or there are several online sources to find them, for a neater look, and not much money. Now, we get to the shape...

If you want to keep things simple, you can make a box. Is this the best enclosure? In my opinion, no. Whenever you have a right angle, you have standing waves, and this we want to avoid. I can point you to a few pyramidal designs online, similar to the Wilson WATT appearance. For a small monitor speaker, I'd point you in the pyramid direction. If you have no woodworking skill or know how whatsoever, then come back and let us know, and we'll continue this further...
Sensitivity, I believe, is almost always measured by itself, primarily because different boxes change the sensitivity (horns for example). The industry standard is to present an 8-ohm speaker with a 1 watt (2.83 volts) input signal and measure its output in an anechoic chamber with a microphone at a one-meter distance.
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