Question about volume

phileth

Hi guys. I'm pretty new at this whole home theater system thing and was hoping someone could answer a few of my questions about volume.

1. What exactly is a negative decibel?

2. Why do I have to adjust the volume setting on the receiver from different sources to achieve the same volume?

3. Does is really matter how high you turn up the volume on the receiver without getting distortion? For example, when watching TV, I usually have the volume around -35 dB to -30 dB and it is plenty loud. But I have a few DVD's that I have to turn the volume up to around -20 dB and it really is still not loud enough. I took it up to -10 dB and it was getting pretty loud, but didn't want to go higher. This also happens with some other TV channels.

For some background, I have a Denon AVR-1905, Polk Rti4 fronts, and a PSW 10 sub. I don't have a center or surrounds yet. Thanks.

PolkThug

I believe "0" is a "reference level". So, if you are at "-13 db", you are 13 db's below reference level. (Maybe someone else can clarify this)

Different sources have different outputs, so we have to adjust accordingly.

Frank Z

A negative reading is the value below your receivers reference level. If your reference level is 80db and the actual volume indicated is -20 db then your receivers output is 60db.

Different sources often require varying amounts of gain to achieve the same volume level. Some receivers/preamps allow you to vary the amount of gain from a specific source(s) to help eliminate this problem. Here's alink that you might find interesting...
http://www.hometheaterforum.com/htforum/showthread.php?&postid=1201017#post1201017

Distortion is a speaker killer. the problem is rarely the speaker, instead its the amplifier. The volume control on your receiver is the only way to protect your speakers. I know it sounds simple, and it really is, but if your hearing distortion your volume level is too high. If the distortion occurs before your speakers are loud enough for you then you are in need of more power (re: bigger amp).

McLoki

phileth wrote:

1. What exactly is a negative decibel?

As others have stated, it is referring to reference level. Dolby has decreed that reference level for movies to be played back at can and will include peaks of 105db in all the channels and peaks of 115db in the LFE or subwoofer channel. (that is with all speakers set to small in your AVR) If you calibrate your system using avaya or Digital Essentials, the test tones that are included on that disk are a set level below reference so that will allow your system and mine to play at the same volume (at the listening position) if we both listen at -10db. (95 db peaks, 105db peaks in LFE channel) even though our speakers, amps and rooms are different.

Since it is really designed for movie playback, it does not correlate nearly as well when listeing to the radio, cd, or tape playback. (basically you calibrate for your DVD player and the rest just falls where it may) Some AVR's will let you adjust the volume of different sources up and down to try and equalize volume, but it is hard to do since it is hard to play test tones over the FM radio.

phileth wrote:

2. Why do I have to adjust the volume setting on the receiver from different sources to achieve the same volume?

All an amplifier does it take a low level signal and make it louder. All the sources in your system send a different volume for that low level signal. Just saying that the sources are a different volume. It is not your AVR that is changing the volume on you.

phileth wrote:

3. Does is really matter how high you turn up the volume on the receiver without getting distortion?

Yes, but since you calibrate your system for reference level it is hard to say "don't turn up your volume above 10 o'clock" or "don't listen above -10 from reference level"

In my case, I had my system calibrated for reference level when I was just using my Onkyo AVR. Since then I have added a 500watt/channel amplifier and recalibrated everything for reference level. -15db from reference is the same volume now as it was when I had just my Onkyo AVR running, but where the Onkyo was starting to run out of steam at that volume, my new amplifier is not even breaking a sweat so I can turn it up louder now with less distortion than I could before I purchased my amplifier. Also keep in mind that distortion is not just in your AVR, it can also happen if you have your source calibrated to high in your avr. (clipping the low level signal) or in your speaker if you start approaching its design limits. The answer to all kinds of distortion is the same though - turn it down till you find out what is causing the problem and then work on that piece.

Michael

BTW - welcome to Club Polk.

louhamilton

And then you have a receiver like mine that seems to be too old for a reference level because the volume is MIN, 1, 2, ..., 47, 48, MAX. I use 20 - 25 for most of my listening levels. I have not invested in an SPL meter yet, so I have not tweaked my system yet. I am waiting until I finalize the position (waiting on new speaker mounts) before I invest in one and tweak it.

-Lou