2. tech-talk
  3. 161005-2288

How can I establish a reference level?

With now 350+ hours on my new rear end (I hope it is OK to call the new speakers that, given the common use of the expression front end for the source) I am trying to understand gain and how it relates to listening level. The terms reference level, anchor level, gain structure, dB, dBU, crest factor, etc. all form an ill defined blur. My interest is in protecting one of my five senses. No amount of money and equipment swapping will ever reclaim lost hearing! Now with oodles of distortion free headroom I need to be careful.

Specifically -
JBL 4367 - 94 dB, 300W
Benchmark AHB2 in bridged mono 380W
SONY XA5400ES Compact Disc Player

What I find is -24 dB set on the preamp (with 0 dB being no voltage gain or cut with respect to the source signal) is too loud on most recordings - especially Pop and Jazz. On the 1964 SONY Classical recording of Petrushka, Ormandy (SBK 47664) a gain of -24 dB is pretty realistic as it is on many other classical recordings.
Some recordings sound loud no matter what the volume. Take Jimmy Smith with Kenny Burrell (Phono 870267) for example (listening to him now @ -34 dB)
Much of my listening is far-field, though the speakers are only about 6' apart in an open floor plan of about 1200 sq. feet.

The inverse square law relating to how loudness decreases with distance from the source - how is it affected by a stereo pair? Get on axis near-field with the speakers and just try and keep your mouth shut. Awesome!

So I have a new definition of LOUD and I want to be careful and have some consistency.
I feel -24 dB is a good reference level and am wondering how that relates live sound and the recording process.




mikewerner
pragmasi
212 posts
 
The quick answer is that it is very complicated and impractical to calculate the sound pressure level at the listening position based on calculations. You should measure it using a dB meter, this will allow you work out a safe listening level. General advice is that prolonged listening at greater than 70dB SPL could cause damage... this is probably quieter than most of us are used to.
The slightly longer but very generalised answer is that the loudness at the listening position is dictated by the output level of the amplifier, the efficiency of the speaker and the size of the room. The dynamic range of the source material is also a factor in this as heavily compressed recordings will sound louder.
I'd recommend understanding these relationships if you're trying to spec a system to meet your needs i.e. realising you don't need a 300W amp if you have an average sized room and reasonably efficient speakers. But if you want to protect your hearing you won't get close enough to the correct answer without measuring.
millercarbon's avatar
millercarbon
12,531 posts
 
Waste of time. For the simple reason every recording is at a little bit different level. Some a lot different. Some compressed real bad. 

But that's the least of it. You're right, your understanding of these terms is a blur. As in, there is none. Pick one or two. Right now I could write a book trying to address all your misconceptions. A page per word at the very least. Seriously. Baby steps. Take one. Which one do you want to work on first?
roberjerman
4,319 posts
 
If you start to feel uneasy it's too loud!
More to discover