Xenon lamps....

Quote:
David,


Unfortunately, Xenon lamps run hot - which means higher flow rate cooling fans - which are noisy.


For this reason, the movement has been away from Xenon lamps. The newest D-ILA projectors from JVC use

UHP bulbs and not the Xenon lamps found in the earlier D-ILAs.


I like the Xenon lamps, and am willing to alleviate the noise by other means - hushbox and behind the wall mounting.

However, I think most HT consumers don't want to bother with taming the fan noise - and the industry is moving in the

direction of quieter projectors - even if it means dispensing with the Xenon lamps.


I believe you probably will find Xenon lamps in high end machines - the ones destined for fancy theaters with

projection rooms at the back.

I am now MrW, how flattering...


There are few good reasons why Xenon bulbs are used in the "big-daddy" projectors (film and digital):


1. For illuminating film, you have to have a light source with a smooth spectrum response. If you don't the colors will look funky. The smooth spectrum response of a light source is determined by its Color Rendering Index (or CRI). Xenon lamps have a CRI that is at least 99 (100 is perfect) and this is very important for film. UHP lamps have a CRI in the 70's-80's but for digital video it is irrelevant. In digital video you are using tri-stimulus projection. Once the color is filtered properly into the three primaries that is all that is important. CRT's have horrible spectrum response, Laser projectors have horrible spectrum response, yet each can produce magnificent colors. With video you don't have to illuminate the film, you have full control of the primaries and are using them to illuminate a white wall. It is an apples and oranges comparison.


2. The target for movie theaters is 5500K. At this color temp, the new Perkins Xenons are as efficient as UHP so there is no efficiency gain by using UHP. However for video 6500K is closer to UHP's natural color and further away from Xenon's natural color so UHP's when filtered properly have more 6500K lumens per Watt than Xenon.


3. A reason they don't use UHP for D-cinema is that they don't make big UHP lamps. The biggest I think out there is 300 Watts. So, if you were trying to do a D-Cinema application, then you would have to combine the output of many UHP bulbs to equal that of one big 6000+ Watt Xenon. Personally I think Sony can use whatever marketing pitch they want, but the reason they aren't using UHP is because they need a big Xenon in their projector. Sony is using a lamp that can run over 900 Watts and is a Perkins Xenon. That type of output isn't possible with a UHP.


There are good reasons for either lamp type, but assuming that Xenon is categorically superior is wrong and for most HT applications UHP (or another Mercury derivative) is better choice.


-Mr. Wigggles


Ps. Xenon vs UHP is kind of like Vacuum Tube vs. Solid State. Vacuum Tubes will heat your house better but they don't sound better. (That comment should make the natives restless.)

Quote:
I was with you right up to this last part.


Although I use solid state amplifiers, there ARE legitimate reasons for using vacuum tubes. The circuit topologies that

one uses with vacuum tubes will have even order harmonic distortion products vis-a-vis the odd-order harmonic

distortion products from the topologies used with solid state devices. The human ear finds the even-order distortion

more acceptable than odd order.


Also, tube amps are "soft clipping" - that is they will start to deviate from the signal as they approach the

clipping point. Solid state tracks the signal right up to the clipping point - and clips suddenly - a "hard clip".


Many feel the benefits of even-order harmonic distortion and soft clipping make up for the heat, expense and finicky nature

of vacuum tube devices.