Planning a DIY projector and have several noobish questions

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After some 3 evenings of research on DIY LCD projectors, I somehow found this forum and it looks like there are some very knowledgable people here. I figured I would post what I want and perhaps you guys can point me in the right direction.

What I'm basically looking to do is create a projector with a 15" LCD and 400W metal halide lamp to create a screen size of 8-12 feet from a distance of about 10-15 feet away from the screen. I think I'm going to be planning my build around the MkIII over at

As I am still very new to this, I would also like some input on the prices they have there. A 400w metal halide kit (ballast, lamp holders, bulb) is listed at $215. Two fesnel lenses and a triplet-80 projection lens sell there for $70. Unfortunately, the 400w ballast is not available there in 120v.

Anyways, here is my list of questions:
1. How is the pricing of the light kit and lens kit compared to other places?
2. Are the lenses listed there of reasonably impressive quality?
3. Exactly what 400w metal halide lamp and ballast should I be looking for to have good performance at a reasonable price? (part numbers at would be good as that seems to have a lot of choices)
4. If the lens kit at is not good or is overpriced, where should I go to get them and what should I get?

My most important question, of course, is with the ballast and bulb. I can order everything but the ballast/lamps at diyprojectorcompany.
another lamp choice

Their price for the lamp kit is not unreasonable: Double-ended lamps all seem to spec an electronic ballast, and those are expensive.

If you want to use a cheaper (but slightly larger) lamp, here is a good choice:

An S51 HPS ballast kit, like $62.50

A Ushio MH retrofit lamp like: $38

An E39 Mogul socket from a local electrical supply store ~$8

Shipping on the ballast can be expensive, since magnetic core ballasts are very heavy. I think Goodmart has a warehouse in Orange County, CA. (If that is the O.C. you meant in your handle info.) See if you can go pick it up. Otherwise, you can find an S51 ballast locally, They are pretty common, since they are for the standard HPS "pink light" used in parking lots, etc. MAKE SURE you get one that can run on 120 VAC, with the capacitor & ignitor included.
So I take it I just need to mount that thing sideways and all is good then.

What is the difference between the mechanical ballasts and the electronic ones? The most difference I would think it can make is possibly extend the lamp life and perhaps make less noise.
next question: Why 2 Fresnels? I see kits that come with 2 and have heard people say they used 2. Don't you just need one to make the light hit the LCD panel straight on and evenly? What's the other fresnel for?

Another question: Is a condensor important? How much of an improvement will it bring? Where would I find one of those?

EDIT: Also, what exactly is a "long throw" lens? The mkIv project over at seems to be more capable of fitting a 15" LCD panel but I'm afraid that "long throw" means I'll have to put the projector significantly further from the screen to obtain a picture the size I want.
From the initial research I have done, I believe I read somewhere that using a fresnel to project an image would distort the image. The fresnel should only be used to shape light.

So I'm going to do light - UV filter - fresnel - lcd - fresnel - mirror - lens.

We'll find out how it all works out when I get all my parts ;-)
I ordered both IR and UV filter glass already ;-)

As for cooling, I already have a 12v power source and 3 low noise 120mm fans from a previous failed modding project (I shrouded/ducted an in-window air conditioner so it can function on a desktop). With the kit I ordered, I should also have 2 80mm fans coming. That should make for more than enough cooling.

I'm likely going to use the 1 80mm fan to blow directly on the bulb, one 80mm fan to blow on the LCD (or whatever surface I have exposed from 2 glass plates, 2 fresnels, and an LCD) and 2 120mm fans for circulation in the hot part of the box
cooling heresey

The "common knowledge" is that you need several fans, but my 250 Watt 15" LCD projector may disprove that:

I have a single 120 mm 65 CFM 120 VAC fan pulling air over the LCD and fresnels, over the hot mirror IR filter, then through the lightbox (from the socket toward the tip of the lamp), and then through a duct to the fan mounted on the side of the enclosure. The exhausted hot air (about 110 F) all ends up outside of the enclosure. I designed the enclosure so the different layers would have an open duct along one side. I can block the ducts on alternate sides, so the cool air has to travel all the way across the LCD, etc. to get to the next level. I think the key to this system, is to make the air flow from cool areas to hot areas. (It does not matter if the air around the lamp is 95 F, it will still cool a 400 F lamp.)

My result is an LCD that never even gets warm to the touch.
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