[Drewnz]

Hi


Can anyone tell me what the basic formula is to calculate Ansi lumen drop over distance.

Is it a 100 ansi drop for every 3 meters? I realise room atmospherics plays a part but, i just want the basic best case scenario formula.

Any help would be appreciated.

Regards

Drew

[IWC Dopplel]

Lumens/Square foot of your 16:9 screen will give you your FTL reading. The Target FtL is 12+ Depending on your in room light control. This is then multiplied by the screen gain.

By way of exmple my screen is 53 sq feet the JVC HD100 is quoted at 600 Lumens and the Carada screen is quoted at 1.4 gain (Typical matt white screen are ususally 0.8 - 1.0)

So in THEORY I will have 600 x 1.4 / 53 =15.8 The reality is calibrated projectors will not produce the quoted Lumens, and screen gains can be exaggerated and bulbs dim with use. Also throw ratio will reduce the light output. Minimum zoom produces more contrast and less light than maximum zoom. I see less than half this figure ......................

You will not lose lumens by distance. Unless you consider dust particles and other minor considerations. Light travels quite well and quite quickly if you ever studied Physics (not meant to be patronising )

[Drewnz]

Hi.

Cheers for that..It's pretty easy really eh. However a co-worker just asked me this and im stumped!!!

What is the (seated) coverage diameter for a loudspeaker specified at 93 dB 1W/1m, 120 degree coverage and a ceiling height of 12 feet

Im trying to nut the formula out...any ideas?

[IWC Dopplel]

Originally Posted by Drewnz

Hi.

Cheers for that..It's pretty easy really eh. However a co-worker just asked me this and im stumped!!!

What is the (seated) coverage diameter for a loudspeaker specified at 93 dB 1W/1m, 120 degree coverage and a ceiling height of 12 feet

Im trying to nut the formula out...any ideas?

I suspect there will be no formulae for room Db as the room refections and materials will all have an impact.

Regarding db per watt, there should be a formulae that looks at voume drop off from a point source.

Regarding the actual question, for me it is a bit of a non question. Most speakers in room will be designed to work in room !