[dave in gva]

Hi guys,


Anyone with a frequency meter and an LT-150 out there? If so I'd be very interested to hear from you.


I'm going to make a passive hushbox for my LT-150. I think if the frequency of the fan noise is high enough it should be possible to build a simple design that would operate as a Helmholz resonator and absorb a good part of the fan noise....but to design the box I'd need to know what frequency range I'm aiming to block....


So - anyone care to contribute to the advancement of science? For myself, and I think many others, I'll be using a ceiling mounting, so I'd need to know what frequency range the projector's noise output is when it is operating in the upside down position. All you'd have to do is turn your projector upside down, fire it up and read what the frequency range is for the noise output. Post it back here and we can work through a passive hushbox design to take the noise out of the equation.


All the best,

 

[KBK]

The frequencies involved are high enough that standard methods of absorption will be more than sufficent. The Low frequency content is minimal. The energies involved are minimal. so, solid, high mass hushbox, with well-joined sidewalls, of fair mass, with a suitably chosen absorptive fire-rated faom, is more than adequate. Also, remember to SOLIDLY mount the hushbox,or What the hushbox is conneted to. Something must act as a sink for th energy. This is critical to getting the last bit of energy out, or dumping the energy accumulated.


One single gap or fault in the entire set-up....and all the energy gets out. No faults in the hush system..and the absorption is complete.