Hi
@Ravindra Desai
Wc to the forum.. You seem to have vast expereince..
Glad to have a professional/commercial installer on the forum.. Hope you could shed some light on topics..
Am curious to know,
- How many subwoofers does a theaters have?
- Where do they usually place it in the theater ?..
- Roughly how much power (or) SPL is required from each..
- How many measurements (for bass) do you take, until you deem they are good..
- I don't know the logic behind Atmos channels being placed flat overhead (spread across the theater), but would it be better if these over head channels are placed in hemisphere type overhead?..
Appreciate you inputs..
Hello elangoas,
Let me give your questions a try:
- How many subwoofers does a theaters have?
For subwoofer, there is no limit. Its the budget that constrains it. All the 5 theaters where I installed the sound system, the wattage to the subwoofers was 2-4 times the center channel. spread over 2 x 18" drivers. Practically speaking, 2 x center channel wattage gives correct sound and feel with safe headroom. But sometimes the theater owners insists on more punch based on the mood of their local crowd. This was for 400- 650 seat capacity
I know Apsara theater in Hubli has 8 x 18" subwwofers. But their theater size is around 850 seats.
Sterling in Mumbai has even more, but I don't have the exact count.
Remember, most of the times, the number is increased to spread the load. You cannot just go on adding subs as it would drown the mids and the highs.
- Where do they usually place it in the theater ?..
No fixed place. Usually at 1/3 and 2/3 distance from side wall.
Remember, even the walls behind the screen are treated heavily. So there is no booming even if they are all placed in one corner.
- Roughly how much power (or) SPL is required from each..
The B-chain settings (EQ) uses a compressor and a limiter on all the channels including the LFE channel. You can push the subs hard and still be OK. If the person doing the settings does not know what he is doing, you will have konked off subs and HF units every now and then.
To answer your question: Calibration is done at 85db for all the channels including the subs. So if you use one sub, the response, theoretically, should be flat. If you use 2 subs, you will have 3db more bass and so on. Remember, the dynamics of the recording can go as high as 120db but the compressor/ limiter is set at the onset of amplifier clipping. Also, no one can and should watch a full length movie with full dynamic range.
- How many measurements (for bass) do you take, until you deem they are good..
Gain, 27-band graphic eq, 6-band parametric eq, delay and phase settings are done. A good installer will do it all manually. An experience installer will manually fine tune the settings after a round of auto-eq.
People do the settings differently. Some use the calibration mike at the center and that's it. Some take readings at three different places.
Again, to answer your question: There is no definate pattern/ method.
- I don't know the logic behind Atmos channels being placed flat overhead (spread across the theater), but would it be better if these over head channels are placed in hemisphere type overhead?..
I don't know. I have to think.
The installations that I did were in theaters with very limited budget. We had to cut down from 5.1 to 2.1 (Center, Mono surround and sub-woofer). Trust me, no one could tell the difference in any of my 5 theaters over a period of 15+ years.
Coming back to your question, our head needs to be in a mood to resolve the sound position as we would be engrossed in the movie.
You tell me: Will you be able to tell the difference if you were un-aware of what the configuration is? Panned effects is a very small part of the entire content. I would feel happy with top class vocals, good (not too much) bass and surround that creates an ambience of the scene. Personally, I don't care how many surrounds. I also don't like installations where I can tell where the surround speaker is located. I like to be enveloped by surround, not distracted from my heroine on the screen.
I hope that I have answered your questions.
Note that I have expressed some personal opinions in here. So don't take me word for word.
b.t.w. don't you agree that with the technology that we have and the money that we spend, the user should not have to do anything. He should be able to un-box the system and use it. That's it. If the likes of A. R. Rehmaan spend hours recording their stuff, who are we to change it? Makes sense?
Yes, systems that need no calibration also exists!! Interested?
Regards,
Ravindra.
