Thanks to all of you.
When I was talking about about power in the preamp I made things confusing but it was just saying that theoretically as soon as you have a voltage and a resistance that is not infinite, you have current (I = U/R) and ultimately power (P=V^2/R) even if it’s a very small...
Thanks for clarifying. Could you by any chance point me to an online explanation of where the doubling factor comes from in this case? If I understand logs correctly it derives from an expression where V was to the power of 2?
You assumed right. Is there an abbreviated convention for this...
I am not sure what you mean by 0 dB ?
From what I have read, a typical AVR will use a narrow band PN generated at -30 dBFS and use this to calibrate each speaker so as to read 75 dB(C) from it’s calibration mic.
This should ensure that movie content, which is recorded at a normalised -20 dBFS...
Thanks for the explanation.
Thus, do we have any way of calculating how much of the total power we had previously calculated would be redirected to another speaker because of bass management, to find a more realistic figure that will help use choose an amplifier?
What confuses me is if sensitivity is measured with a 1 kHz tone then how can it be relevant to calculate how much power you need to read a 85 dB(C) SPL generated from a pink noise?
Surely you would need much more power to produce a PN than a 1 kHz tone to the same SPL?
I am not sure what I mean either...
- for a given speaker, one can calculate how much power one needs to reach a given SPL at a given distance, using the speaker’s sensitivity figure.
- for reasons I have yet to understand, bass frequencies seem to require much more power than mids and highs...
Great explanation !! I see more clearly now.
Is the sensitivity measured with a 1 kHz tone @ 2.83V?
If so, I don’t understand how one can use this value to calculate how much power you need to achieve a given SPL at the listening point using a pink noise, which contains many more frequencies...
Hi Pluto,
I realise I haven’t made this obvious: I absolutely don’t pretend to understand much of what we are discussing here. My intention is just to understand, for the sake of understanding, so it doesn’t matter if it’s really important in the end :).
To answer your question, yes I meant...
Hi Paul,
Thank you very much for your reply!
Very good explanations and a lot to read in the links you provided. :)
If I understand correctly, the volume setting on a preamp is measuring a difference of power relative to a reference? Hence the 20 (2 x 10) log (V/V’) formula because P=V^2/R...
If I understand things correctly, in the world of cinema and home-cinema, the norm is that each speaker should be able to reproduce sound at a reference level of 85 dBC SPL at the main listening position, with a 20 dB headroom.
It follows that the power needed to reach that level can be...
Could someone please explain to me if it is possible for any preamp to calculate for any given position on the dBFS scale a pre-out output based on a known dBFS/preout value?
I.E. a given preamp measures 1.4 V RMS on it’s preouts when the volume is set at -0 dBFS. From there, can we know where...