How much is the dynamic range of Dolby SR, DTS, DD, and SDDS?

Dolby Digital is more dynamic than DTS? I didn't know.

So why on DA20 specs I found 92dB?

Dolby Digital, DTS and SDDS are all 16-bit systems and ALL 16-bit digital systems have a true dynamic range of about 92dB regardless of whether the manufacturer claims otherwise. The problem here is that dynamic range for digital systems is calculated differently depending on who you are and on your motives.

For example nearly all digital systems add a small amount of "dither" (a form of random noise) to allow signals to exist below the 1-bit barrier (statistically speaking). This process allows better resolution for low level signals and has been described as allowing the system to "see" signals beneath the noise. Some manufacturers then calculate the dynamic range as being the difference between largest signal and the smallest signal that can be accommodated, regardless of the noise level (giving figures typically around 96dB). This is in stark contrast to the conventional standard for dynamic range (which is universally applied to analog systems) which is the difference between the largest (unclipped) signal and the noise floor.

Furthermore, digital dynamic range figures do not take into account performance of the analog portions of the sound processor, which (except of course for Panastereo ) are usually somewhat worse than the digital part of the system.

The dynamic range of an analog SR track is primarily dictated by the film itself and the performance of the optics and pre-amplifer. It can range from downright pathetic for a filthy, scratched print using poorly aligned optics and a noisy preamp, to almost as good as digital.

The figure of 144dB does apply only to 24-bit digital systems which are not used in any of the film sound systems because of the large amount of data required, even with compression.

Dynamic range should not be confused with reference levels and headroom. 85dB is the standard reference level (first introduced by Dolby) which is used for the screen channels for both analog and digtal film sound systems. Headroom is the maximum signal level above this reference before clipping. The usually quoted headroom figures for film sound systems are 6dB for A-type, 9db for SR and 20dB for digital, however even here we do not have a clear cut comparison because analog signals can significantly exceed clipping levels for short periods without the resulting distortion being audible, whereas digital signals cannot.

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Ray Derrick
President
Panalogic Corporation Pty Limited
44 Carrington Road
Castle Hill NSW 2154 Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

You was very clear.
My question borned because I read on a newspaper a mail from a customer (with the comment of the director of newspaper) where he claimed that movie are too loud.
The director agreed with the customer.
So I would like to reply to the newspaper saying how much difficult is found a volume level so that 300 people get on well together AND that digital sound is more dynamic than analog one.
So I would like to write down one "number" to have a direct comparison from the two systems.
Digital dynamic is 92dB. In your opinion, generally speaking, how much can I consider for analog?

If you really want to quote dynamic range figures for comparison rather than headroom, then SR analog would generally have about 70dB dynamic range in an average system with a reasonably clean print. (This being made up of 9dB headroom and about 61dB signal to noise).

You might want to take a look at the "Are movies to loud?" paper on the manuals page, it's near the bottom under Instructional Documents. It's very interesting reading.