[tomhahn]

Several folks here have used this glass for their D-ILA hushboxes. I'm building one for my HT300.


Anyway, on the Edmund website, the glass is specified as 3.3mm nominal thickness. My question is: Is it really than thin? How could it afford much of a sound barrier if so? Thanks for any info.


-Tom

 

[ssj2]

Tom, I use the Edmund glass in my homemade LT150 hushbox and it the sound barrier is really quite effective.

 

[AlanMFriedman]

I have a G-15 mounted behind the rear wall in my HT and I am using that same glass (I believe it's an 8x10 piece). It is THAT thin and is a great sound barrier. It also has no visible impact on the picture, which is outstanding on my 92" greyhawk.


Great product. Inexpensive and very effective for this application.


Alan

 

[johng]

Hi Folks,

Do you have a part or SKU number for the specific glass you have had success with?

Thanks,

John G

 

[Morbius]

John,


Check out:

http://www.edmundoptics.com/IOD/Disp...Productid=1919


Greg

 

[johng]

Greg,

Thanks. Much appreciated.

 

[Taff]

Hi All,


I had the chance to look at the specs on the Edmunds site and for $38 for an 8x10 piece of float glass ( coated ) I think that you'd be better of going down to a local picture framer and getting them to cut you some glass.


I'm not too well informed on what hush boxes look like but I do know optical systems.


An uncoated float glass plate ( basically window glass ) you would expect to loose not more than 3% of the transmitted light ... and that's being extream.


I would suggest that you have a look at making your own from picture frame glass ( about the same thickness ) and if your unhappy with the out come get back to me as , if there is enough interest , I could look into getting the plates coated at my facility. I do think that you be happy with your first results though.


Taff

 

[Paul_Saul]

No. For uncoated window glass with light normally incident on it you lose 4% per surface. Since it is a plate of glass that you are going through there are two surfaces so you will lose a total of 8%. This figure will vary somewhat with wavelength (color) of the light and is very sensitive to the angle the light hits the glass. It only goes UP from the 8% figure as the angle gets farther from normal incidence. You will also get multiple reflections within the glass potentially leading to multiple images. Next time you look out a window look to see if you can also see your reflection.

 

[johng]

Hi Paul,

Are you saying that the glass being recommended is NOT the way to go? What is the difference between the "Float Glass" and "Optical Glass"?

Thanks,

John G

 

[Paul_Saul]

What I am saying is that I believe that an anti-reflection coating on an optical window for your PJ is the way to go. While it is not as cheap as a plate of glass, at $20 to $40 it is a small fraction of the cost of your PJ and the performance difference (coated vs uncoated) will be worth the addded expense.

 

[Morbius]

I have to agree wholeheartedly with Paul - the Edmund Scientific anti-reflective glass is definitely the way to go.

[ You can be sure all the glass in your PJ's optics system is AR coated - the manufacturer did that for a reason - and

you should continue the practice. ]


Not only do you not want the loss of light due to reflections - Taff, you definitely don't want to be sending

a few percent of your projector's output energy back into the projector through the front lens.


Although the cost may seem high - it's only of few tens of dollars - a trivial cost compared to the projector and the

other components of an A/V system.


This is not a good place to scrimp - you don't save much money - and the downside just plain isn't worth it.


Dr. Gregory Greenman

Physicist

 

[bluedevils]

I used an 8x10 picture frame to mount my edmunds. At first I didn't really see any difference between the original glass and the edmunds.

When mounted, looking straight at the lens and glass, I could not even tell there was any glass plate there due to the non perceptible reflections!!

 

[Jay C]

I too used the glass in question (Edmund) in my hushbox design. The sound is not transmitted via the glass, nor the 1/4" lexan shell. I also agree with the AR argument. I used a 3"x3" in my design.


FWIW,

Jay