[Li On]

Hi,


Last night CKL finally invited me to see his LT150 as he finally installed a new Stewart Studiotek 1.3 gain wall screen and a hushbox for the LT150 on the ceiling. Source is a HTPC using a GeForceMX and WinDVD 3.1.


After some minor adjustment on the GeForceMX overlay and the LT150 picture control, white balance, we enjoy the picture til the mid-night!


With more viewing, I can kind of see past it's flaws and enjoy it's wonderful color rendition, great resolution layers from darkest to brightness, the great 3D feel. Once again the BEST digital projector picture IMO. Without it's usual problems, I'll replace my CRT projector for it!


There is 1 minor issue, the HTPC GeForceMX display card was RFI modded. When using the 6' 15pin to 15pin cable come with the LT150, the picture is SUPER sharp and clean, perfect. CKL has built a 28' 15pin to 15pin Carane VGA cable between the HTPC with a ceiling run to the LT150. With that long cable, there's some visible "ghosting" to the picture on the Windows desktop. The "ghosting" effect is hardly noticeable in DVD playback.


CKL also has another PC with a old G400 display card. There is NO "ghosting" effect with that PC connected to the LT150 using the same long cable.


Should CKL get a better quality cable to make the best use of the RFI modded (the card is mine actually!), or get a display card with the RFI in place?


regards,


Li On

 

[CKL]

My ceiling mounted LT150 with hush box:

http://www.urphoto.com/users/39429/2...45941cfwme.JPG

 

[wst]

Dear Li On,


Sorry for my stupid question but, what is RFI modded? Also, many people think that Radeon based display card has a better PQ than Geforce based case but you still use one, is that because it has more control in the overlay?


Thank you!

Tony

 

[Federico]

"Should CKL get a better quality cable to make the best use of the RFI modded (the card is mine actually!), or get a display card with the RFI in place?"


I think what you need is an RGB line amplifier like the Extron P/2 DA2 Plus, this one also is a splitter, I'm using one with my 50' cable with very good results. You can buy it from ebay auction to save some money.


Federico

 

[sonny b]

CKL,


That's a nice looking hushbox. Can you share some more details of your design? More pictures perhaps?


What are the dimensions? What did you use for a ceiling bracket? Where are the exhaust fans located? Is the lens port covered or is it covered with clear glass? I pressume the white gadget inside is a thermometer.


Looking at the picture, the inside of the hushbox appears to be compartmentalized. Did you segregate the intake and exhaust sections of the projector?


I also noticed the round holes on the side. Are these the intake ports? How many did you make? Looks like you covered them with filters, right?


Sorry for the many questions. I'm sure a lot of people are also interested in this.


Tnx

 

[CKL]

I built the hushbox to lower the noise level and dust getting in. OK, here is the detail design.


(1) Dimensions


The internal size is (15x12x4) inch. The thickness of plastic board is 0.25in for the cover and 0.5in the board connecting to the bracket to the ceiling. All the equipment were install on this thick board and the cover was fastened by fours numbers of screws.

http://www.urphoto.com/users/39429/2...45924bvsms.JPG

(The fans and transformer have been relocated inside the hushbox)


(2) Air Intake and Filter


There were two dia. 2.5in holes facing exactly the air intake of the projector. The holes were covered by filters. The filter covers could be removed from the outside to replace the filter material. I used the filter material for air conditioner.

http://www.urphoto.com/users/39429/2...45928tcbct.JPG


(3) Exhaust fans and transformer.


I used two number of 55mm exhaust fans (12DCV, 1.4W, 15cfm). They used magnetic floating motor so that they were more quiet than conventional fans. I didn't give them full load. After testing, I supplied 8DCV to further lower the noise level. I used the electronic transformer (using for mobile phone) which was lighter and cooler comparing conventional transformer.


There was a enclosure to cover the air exhaust of the projector and the external exhaust fans. It was used to separate the cold and hot air. The enclosure was not completely sealed where the air underneath the projector (at the lamp cover) could be drawn out. The air exhaust was facing the ceiling.

http://www.urphoto.com/users/39429/2...45925piffi.JPG

(The fans and transformer have been relocated inside the hushbox)


(4) Lens filter


I used a 62mm UV filter in front of the lens. Please choose filter without affecting the colour balance and no reduction of light intensity. It was better to have multi-coating to minimize the reflection. I found there was reflection from the plastic cover to the rear of the projector. That's why I placed a piece of paper at the cover and made it be good looking.


(5) Holes for cables


There were two holes at the rear for cabling. Please be reminded to seal the holes and gaps.

http://www.urphoto.com/users/39429/2...45940uhcms.JPG


(6) Thermometer


I installed a thermometer to monitor the internal temperature. The internal temperature can be kept at 40degC or lower at the room temperature of 25degC.


THAT'S ALL

 

[CKL]

Quote:

Originally posted by Federico "Should CKL get a better quality cable to make the best use of the RFI modded (the card is mine actually!), or get a display card with the RFI in place?" I think what you need is an RGB line amplifier like the Extron P/2 DA2 Plus, this one also is a splitter, I'm using one with my 50' cable with very good results. You can buy it from ebay auction to save some money. Federico

Thanks Federico for your suggestion. Are you using RFI modded video card with RGB amplifier?

 

[Federico]

"...Are you using RFI modded video card with RGB amplifier?"


No, this is an unmodified board, but I had the same problem, with the long cable there was a ghost that I didn't have with the short cable, now with the addition of the amp the problem is over.


Federico

 

[sonny b]

CKL,


Wow, those are great pics. The design is very neat and elegant as well. Thanks for the detailed response.


I still have a few questions though, if you don't mind...


1. What kind of mounting bracket did you use for mounting the hushbox to the ceiling?


2. Where did you get those nice looking filter covers?


3. What screw size did you use for attaching the LT150 to the plastic base? 4mm?


4. What type of material did you use for the enclosure of the air exhaust/external exhaust fans inside the hushbox?


Thanks again.

 

[CKL]

Federico,


Thanks for your information.


Sony B,


1. The mounting bracket is the one using for surround speakers. It 's cheap around USD13 per pair. It can be adjusted 360deg.


2. I bought the filter cover and fans in the store selling electronic parts.


3. Yes, M4 screws. The three M4 holes at LT150 have different lengths. So you need long screws and nuts to adjust the level.


4. It's simple, thick paper board. You can cut it in any size and shape then spray paint it in any colour you like.

 

[sonny b]

CKL,


Thanks a lot.

 

[bmwrob]

CKL, did you do any calculations for the minimum airflow needed to keep the temperature within safe limits? What is actually the maximum safe temperature for the LT150? Could someone recommend a site or link which describes the calculations for the airflow needed?

 

[CKL]

Hi Rob,


I didn't calculate the flow rate but did some experiments. I used a transformer with variable voltage output. I started the experiment at 12VDC and then decreased the voltage gradually. If the flow rate was insufficient, the internal temperature raised continually. Finally, I chose 8VDC. The internal temperature was kept at around 40degC after watching a movie (say 2 hurs) at the room temperature of 25degC. Before I installed the projector the hushbox, I placed the thermometer at the air exhaust of the projector. The temperature was recorded over 60degC. I think 40degC is a safe figure for a hushbox.


I've tried to block one of air intake holes. The internal temperature raised significantly. LT150 uses two 1.25-1.5in exhaust fans. I think the size of air intake hole should be double the size at 2.5-3.0in.


The hushbox does reduce the noise level but I still feel it is not quiet enough. You can try the in-line-duct fan (somebody mentioned here sometimes ago) and add some ductwork at the air intake. I believe there should be further improvement but the size of hushbox will be increased as well.

 

[sonny b]

CKL/bmwrob,


It appears that the target temperature inside the hushbox is arbitrary...opinions seem to vary on what the safe operating temperature should be.


I was wondering if it would be safer to keep the hushbox's operating temperature closer to room temperature. A projector without a hushbox would actually be operating in ambient room temperature despite the high temp (warm air) at the exhaust vents, right?


Would adding more intake vents or perhaps additional exhaust fans make this possible? Would this have an impact on the LT150's operation? Where inside the hushbox should you measure the temperature?


Hopefully, other people who've built hushboxes can chime in and comment on this.


Tnx.

 

[Frode]

Li On,


A Radeon will provide a jump over a RFI modded nvidia card. I originally modded my GF2MX, and while there was significant gain compared to unmodded when I got a Radeon SDR the picture quality did improve quite a lot more. Better colors - not just resolution. That said the long cable run will still be a problem.

 

[CKL]

Quote:

Originally posted by sonny b I was wondering if it would be safer to keep the hushbox's operating temperature closer to room temperature.

It's difficult to keep the internal temperature at the room temperature unless there is additional cooling system.

Quote:

Originally posted by sonny b Would adding more intake vents or perhaps additional exhaust fans make this possible?

The noise actually comes out from the vents. So it's not good to have many vents. Another restriction is that there are vents all around LT150. I can't install just one airduct to the main intake vent. Using bending airduct plus thick filter and quiet powerful fans is the way to reduce the noise level.

Quote:

Originally posted by sonny b Where inside the hushbox should you measure the temperature?

I placed the thermometer next to the enclosure of the exhaust vent (hot air).

 

[CKL]

Quote:

Originally posted by Frode Li On, A Radeon will provide a jump over a RFI modded nvidia card.

Hi Frode,


I'm considering to get a Radeo VE or 8500. I believe the unmodded video card should be find for my 28ft long cable (G400 didn't have). I wonder if it is worth to use modded video card plus RGB amplifier and long cable. The idea of RFI modification is to make the signal path be more direct and straight. Adding amplifier is in the opposite way.


Best Regards,