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Discussion Starter · #1 ·
I thought that I would start a new post and give you my take and lessons learned while building my HushBox. This is a long post, http://www.avsforum.com/ubb/frown.gif but hopefully I have covered in one post, many questions that took me months to research in this forum. First, my G11 D-ILA projector is mounted on a beam in my cathedral ceiling family room and not tied into the hushbox in any way. I built a pretty large box out of ¾" MDF that encloses the 6"x 6" beam. There are cutouts on the side of the box to accommodate the beam and it is attached to the top which is over the top of the beam.


Specs/materials.
  • The box size is 27" wide by 23" deep by 21" high (outside dimensions), no sound insulation yet. (3/4", 4’ X 8’ sheet of MDF $18.00)
  • The whole front (with 8" X 10" Edmund Industrial optics, coated optical glass, Item NT43974, $33.00) has a piano hinge at the top and opens up as a big door.
  • There are 3, fans mounted inside the box at the top, rear. Each is rated at 82 CFM at 12 volts DC, model 4412FM, ball bearing types from EBM industries. The fans on each end pull air out. The one in the middle puts filtered air into the box when necessary. All fans are mounted using small bolts, nuts, washers and rubber grommets in oversized screw holes for fan to box mechanical noise isolation. (3 at $26.85 each = $80.55)
  • There is a baffle plate (S-type) that sits 3"off the bottom of the box and a large rectangular filtered opening for inlet air on the bottom of the box. I used an anti static filter (aprox $7 for 18" x 24") media from Home Depot. It works great and has a nice plastic grill that fits the routered opening. The filter is made up of a black weave filter and on top of that is a tighter weave white filter. I can’t detect much flow restriction at all.
  • A Sears current sensing, "Craftsman Auto Switch" outlet turns power to the fans on and off when the G11 is activated and it works great. (Model 24031, $20.00)
  • JC Whitney Indoor outdoor back lit thermometer. (catalog #15zx8003r, $19.95)
  • Originally I was using a selectable 6 to 12 volt DC, 800ma, wall wart type power supply for fan power. Each fan draws 270 ma at 12 volts. ($20.00) I didn’t like it because I wanted to control each fan individually. See below
  • Misc. hardware, Shipping costs, sales tax etc. $$$$. Total Cost to date aprox $250.00
  • If you don’t have the tools and have a straight forward installation and don’t mind the look of a clear acrylic box, the WisperFlow built by Dave Beatty is a good value at $499.00. Unfortunately That design wouldn’t fit my needs.


I did a lot of reading in this forum when I was in the design phase of the box. I had a somewhat unique design problem because I needed to have my projector as high as possible to properly line up with the top of my 3X4 screen and I only had a beam to mount it on. I couldn’t mount a box to the bottom of the beam as it would take up valuable inches I needed for the G11to screen alignment. So I designed a box to encompass the beam.


There were posts on what people thought the air temp should be kept at for the DILA, but I couldn’t find anything that mentioned where to monitor the temp of the box. I was initially monitoring the air in the general area of the G11 outlet. I purchased from JC Whitney, a 12 Volt back lit indoor outdoor thermometer that I mounted on the outside of the box. Since I had 12 volts to the fans, it was easy to supply 12 volts to the thermometer light. It is has a darkness auto sensor and easily read in a dark room. At this location the temperature was running from 20 - 25F above ambient inside the box with both fans at 12 volts. This scared me because I was seeing it above 95F on occasion so I purchased a third fan. I mounted this in the center. It helped but I had to run all fans at 12 Volts. Much to loud. Finally I realized the air I wanted to monitor was the inlet to the bulb. I mounted the external thermometer sensor on the beam, 1.5" above the inlet. What a difference. The differential of room to inlet temperature runs between 10 - 12F. I am trying to keep inlet air at less than 86F. Typically it is about 83 - 86F after the G11 has been on a couple of hours and is very much dependent on the room temperature. When needed, I can turn on the center fan, putting filtered air into the box. This can drop inlet temp down by as much a 4 degrees in less than two minutes. I stumbled on this effect quite by accident. I have the two inlet fans running at 7-8 volts (pretty quiet) and the center is at about 7 volts when needed. About 10 year ago I built three variable 12 volt DC power supplies and had put them in one hobby box. It was just sitting around as I wasn’t using it any longer. This ended up being the perfect solution for controlling each fan.


Now I’m going to sit back and enjoy. Next (winter project) will be to pull down the box (very heavy) and add sound insulation to the inside. I am now starting to hear more G11fan noise than I am hushbox fan noise.


This is a FYI and I hope it will help others getting ready to undertake this somewhat daunting project.

I hope to have pictures soon, that I can email to interested people.


Don



[This message has been edited by anderdea (edited 06-19-2001).]


[This message has been edited by anderdea (edited 06-19-2001).]
 

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Great description. I sent you an e-mail to request the pics as I am in the process of adding intake fans to my box.


Regarding the fans, I have a couple of questions. Why DC versus AC fans? Also, how did you decide on the particular model of fan?


In some other posts, people referred to Papst fans. Did you check them out as well?


Finally, does anyone know a commercial source for variable DC transformers?


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Discussion Starter · #3 ·
Sands,
Quote:
Regarding the fans, I have a couple of questions. Why DC versus AC fans? Also, how did you decide on the particular model of fan?
"ebm Industries" is very close to me in CT. I called a tech rep and explained what I was doing. He suggested a particular fan model, flow rate and DB noise level, and I had the original two in a day. I selected DC because it’s easy to control the speed and they are physically small in size. The original fans he suggested had a "syntec" type bearing. I couldn’t stop the mechanical motor whine from being transmitted to the box. So I talked to another tech rep, he was more informative. I sent the originals back and purchased the ones I mentioned in my original post. They are a are ball bearing type and 1" thick as opposed to 1.5" of the originals.

Quote:
In some other posts, people referred to Papst fans. Did you check them out as well?
No

Quote:
Finally, does anyone know a commercial source for variable DC transformers?
Can’t help


Don
 

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thanks for the info, how about the design drawings with measurements etc?


As for an additional idea for your box use a switching thermometer which automatically turns on the third fan when the temp is running to hot. I wouldn't want to keep looking at the temp while missing the movie http://www.avsforum.com/ubb/smile.gif ))

I live in Europe so i don't know the electronics stores that you have (prob. Radio Shack).

If you can't find it an expensive alternative is a Honeywell thermostat.


[This message has been edited by Kjelt (edited 06-19-2001).]
 

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Thanks for sharing http://www.avsforum.com/ubb/smile.gif

For the fans in my PC (overclocked AMD Thunderbird) to keep the internal temp as low as possible, I learned that the noise, a fan generates, is very depending on its rpm's. The smaller the fan, the more noise it will make for the same air output compared to a bigger fan, which can rotate less fast. In theorie it would be possible to by pass the noisy internal D-ILA fans and control the airflow by other means, WITHOUT a hushbox. You have to seal a flexible pipe (like the "exhaust of a washing machine, or bette an aluminium flexible pipe like used in the kitchen above the "fire")spray it bloody red for looks and use two big fans inside the pipe, far away from the listening position. This is just a crude idea. You can add a second beautiful painted (different color)aluminium flexible pipe at the outlet of the DiLA with a fan that sucks the air out (far away from the listening position) All the other ideas are stil valid, like temp sensors that autimatically enacts an extra fan

Maybe some day I will do it, I don't like the bigness of the hushboxes.

Kyrill
 

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Discussion Starter · #6 ·
Kyrill,

With an open cathedral ceiling and three exposed beams in my family room, I was pretty well limited on what I could do. The exhaust hose and fan idea, I also had thought off. However there was really no where to run a fairly large diameter hose from the D-ILA exhaust and out of the room without cutting a hole somewhere in the house to vent it to outside air. I think that would look equally as bad as a big ugly hush box. I had to make due with the limited options I had.


Don
 

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Don:


Did you try having both fans on the side of the box where the exhaust is? Right now, my G20 is in a box that's completely open in the back, and it will still overheat to the point of shutting down without the two fans I now have in there. I found that the best way to keep it cool was to have both fans next to the outlet fan of the projector, blowing the hot air out of the box. With one fan at one end blowing air in, and the other fan at the end of the projector's outlet fan blowing air out, it would still overheat.


I'm wondering if your having a fan blowing air out on the opposite side of the projector's outlet fan, would end up drawing hot air towards the projector's inlet fan... It's seeming to me that it's more important to get the hot air out of the box as efficiently as possible, without worrying so much about getting fresh air into it.


- Dave
 

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Discussion Starter · #8 ·
Dave,

Having the fans on the side of the box in my particular application would be difficult and I think would end up being very loud as the DILA Exhaust fans are right there. I really don't have an heat problems with my current setup, in fact I am very pleased with it. I watched a 2 hr movie last night. The room temp was 75F. the temp in the box got to 86.5F at the inlet after about an hour. I turned the center fan on (bringing air into the box) and it dropped to 83F and stayed there plus with the low fan speeds, it was quite.


Don
 

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Discussion Starter · #10 ·
Hugo,

I am at present using the same antistatic filter media that is in the intake area. It consists of two layers of a woven material. Most suppliers of fans have additional frames and foam filter accessories you can purchase for the fans. I didn't get them because at first, I had all three fans taking air out of the box. I have just made a wooden frame (last night) that I will be holding the filter in place with (using duct tape at present). It would cost more in shipping than it would for the material, to go back to the company and purchase just one the foam filter and housing after the fact. However, I would suggest, if you are going to purchase any fans that will be used to bring air into your box, to order the filters at the same time. I don't have a clue if the foam is any better than the filter weaved material I am using now.


Don
 
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