Kain Posted November 20, 2001 Share Posted November 20, 2001 1. Why is it that on receivers (and some other audio equipment) the volume goes from a negative dB number to a positive? How can you have a negative volume? Why don't they start at 0dB and work their way up? Get what I mean? 2. Lets say a receiver is rated 100W per channel. You hook that receiver to a RF-7. Does that mean that on full volume the RF-7 will only give out 100W of sound? The RF-7 is rated 250W maximum continuous, does that mean you need a receiver that can do 250W per channel to take the RF-7 to the max? ------------------ Will be getting the following in December. Home Theater: TV: (Still deciding) DVD player: (Still deciding) VCR: Sony SLV-ED100 (HiFi VCR) Receiver: Denon AVC-A11SR (230V version of Denon AVR-4802) Speakers - Center: Klipsch RC-7 Mains: Klipsch RF-7 Surrounds: Klipsch RS-7 Subwoofer: SVS CS-Ultra w/Samson S1000 amplifier Quote Link to comment Share on other sites More sharing options...
decibel man Posted November 20, 2001 Share Posted November 20, 2001 Kain64, 1) This one I am not 100 percent on. The negative db reading is only a reference point it doesn't actually mean that there is negative sound, obviously. With most receivers, when you turn them all the way up to "0 db" they are at normal full amplification. Anything after that could be a pre-amplification gain. That is why the current trend is to display negative db levels to show how close the receiver is to full amplification. Again this varies between manufacturers and models. 2) The amount of power used is dictated by the speaker NOT the receiver. Because the Klipsch speakers are so efficient they hardly use any power. I doubt that the RF-7's in most listening conditions will ever use more than 20 or 30 watts. That is loud, really loud! Efficiency is based on the sensitivity rating of the speaker, usually represented in a spl rating. The rating for the RF-7's is 102db. That is measured in a lab using one watt at a distance of one meter and only one speaker. The formula is: when the wattage is double the spl goes up 3 db's. 1 watt = 102 dbs 2 watts = 105 dbs 4 watts = 108 dbs 8 watts = 111 dbls = loud 16 watts = 114 dbls = louder 32 watts = 117 dbls = damn loud and so on.... A 100 watt receiver doesn't always put out 100 watts it just puts out as much power as the speakers need up 100 watts. I would love to get into a discussion about current and amperage, but time is short. I hope this makes things clearer than mud for you. There are plenty of other people that will probably chime in on this one. Enjoy and happy listening! JT Quote Link to comment Share on other sites More sharing options...
dougdrake2 Posted November 20, 2001 Share Posted November 20, 2001 Kain - Interesting question about the negative db levels. I recall reading (although my recollection may be wrong) somewhere on this board that volume knobs actually attenuate (or hold back) the output of the amp rather than boost it. So a negative figure would represent relatively how much is being attenuated. On my Denon, a -20 reading is pretty darn close to actually being 20db down from the measured volume at 0. JT's comment about positive numbers coming from a pre-amp boost make sense also, in this light, since you can't "un-attenuate" past the max power of the amp. To increase volume at that point you'd have to boost the pre-amp signal going into the amp. Wonder if any of this is even close to accurate ? Doug Quote Link to comment Share on other sites More sharing options...
Kain Posted November 21, 2001 Author Share Posted November 21, 2001 quote: To increase volume at that point you'd have to boost the pre-amp signal going into the amp. Sorry, but what does that mean? ------------------ Will be getting the following in December. Home Theater: TV: (Still deciding) DVD player: (Still deciding) VCR: Sony SLV-ED100 (HiFi VCR) Receiver: Denon AVC-A11SR (230V version of Denon AVR-4802) Speakers - Center: Klipsch RC-7 Mains: Klipsch RF-7 Surrounds: Klipsch RS-7 Subwoofer: SVS CS-Ultra w/Samson S1000 amplifier Quote Link to comment Share on other sites More sharing options...
dougdrake2 Posted November 21, 2001 Share Posted November 21, 2001 What I was trying to say (and seeking confirmation on), is this: assuming (dangerous) 0 on the volume setting represents the point at which the Denon is not attenuating the amp output anymore (therefore the amp is "wide open"), any further increase in volume can only occur if the pre-amp signal going into the amp is increased, so the amp is amplifying a louder signal than it was before. For that to happen, the pre-amp must be doing some amplification of its own signal before passing it to the amp. Again, I'm just theorizing here and would welcome any corrections or confirmations from the peanut gallery. Doug Quote Link to comment Share on other sites More sharing options...
VideoGUY Posted November 21, 2001 Share Posted November 21, 2001 Gain is one of those words that is hard to explain, but easily understood once you know what it means. I know that doesn't help much. So here goes an explaination. Basically what dougdrake2 is saying is that once the volume knob is at "0db" the amplifier is putting out its maximum power in its "cleanest" form. I chose cleanest because basically by that I mean the sound is coming from its source, through the amp, and right to the speakers. Once the knob goes past "0db" the amp can no longer produce anymore power, it's at its 100w (for example) peak. So, in order for it to get louder, the signal is boosted using gain prior to getting to the amp (aka your pre-amp signal needs to be boosted) So, when you think about it, if your pre-amp signal is boosted in someway, then the amp can play louder at given levels. So gain is applied to the signal. Which is pretty much a technical term that refers to electronically making signal louder. In other words, a volume knob adjusts how much power an amp is putting out, as a result increasing or decreasing the volume of the singal. Gain on the other hand, electronically boosts the singal first creating a louder initial signal, then the volume is adjusted in the same matter. As a result, adjusting the volume of a louder signal. Sounds like a great idea, but once a signal is messed with electronically its no longer "pure". Depending on the quality of the reciever, artifacts (or distortion) will start to be heard. For example clipping or ripping your highs. Make any sense? VideoGUY This message has been edited by VideoGUY on 11-21-2001 at 01:09 PM Quote Link to comment Share on other sites More sharing options...
Seb Posted November 21, 2001 Share Posted November 21, 2001 i thought the dB reading went down to count down to the "reference" level (whatever that is), which can be adjusted on some models... but then again, i may be wrong. Quote Link to comment Share on other sites More sharing options...
Mighty Favog Posted November 22, 2001 Share Posted November 22, 2001 So, Kain, anything below that 0db number is actually the choking off of power going to the speakers. Think of it as a 100w light bulb with a dimmer switch. You turn the knob all the way to the right to get that 100w brightness and left for anything below 100w. When DM, DD and VG talk about a louder signal (in a number above 0db) this is sometimes called 'headroom'. Which some amps can do for limited amounts of time and measurement (say 1.9db). So if you have a source unit (cd player, tape deck etc.) that has an adjustable output knob on it and it is not already set to the max. Then turning THAT up would increase the amount of SPL (Sound Pressure Level) coming from the speakers without having to touch the volume control on the amp/receiver. I doubt seriously that your speakers will ever see a full 100w of power. Well, before something blows anyway. The amp will start to "run out of gas" (or output power) and begin to clip. Oh God, another tech term! If you were to look at an Osciliscope (sp?) and see an up and down wave on the screen, this is the high and low points of power from the amp. It looks like a constant rollercoaster going up and down. When the amp is being asked to produce more power than it is able, then that up-and-down thing on the Osciliscope (called a sine wave) cuts (or 'clips') off the top of the hill. This may sound as if it's a good thing but its not. What that missing signal is replaced by is inaudible high pitched and very dangerous distortion. Too much of this fry tweeters fast; they're the weakest driver in the most any speaker. --------------- Tom KLF-20 Mahogany (Cornell Hotwired) McIntosh C33 Preamp McIntosh MVP-841 CD/DVD Rotel RB-1080 Amp Yamaha PF-800 Turntable/ Sure V15 Type V Cartridge Ortofon VMS-30 mkII Cartridge Stanton 999SS Cartridge Yamaha K-1020 Cassette dbx 1231 EQ H.H. Scott 830z Analyzer Monster Interlink 400mk II Monster Interlink 300mk II Monster Video 2 (DVD to TV) Studio Tech U-48RW Cabinet Monster Power HTS-5000 Power Conditioner/Surge Protector Original 12ga. Monster Cable Enough empty boxes for a fire hazard! This message has been edited by tblasing on 11-22-2001 at 12:34 AM Quote Link to comment Share on other sites More sharing options...
Kain Posted November 22, 2001 Author Share Posted November 22, 2001 I get it. Thanks guys! ------------------ Will be getting the following in December. Home Theater: TV: Sony KV-ES38M91 (38" FD Trinitron WEGA) DVD player: (Still deciding) VCR: Sony SLV-ED100 (HiFi VCR) Receiver: Denon AVC-A11SR (230V version of Denon AVR-4802) Center: Klipsch RC-7 Mains: Klipsch RF-7 Surrounds: Klipsch RS-7 Subwoofer: SVS CS-Ultra w/Samson S1000 amplifier Quote Link to comment Share on other sites More sharing options...
decibel man Posted November 22, 2001 Share Posted November 22, 2001 I like the "light bulb" analogy. I think we are all on the same page. JT Quote Link to comment Share on other sites More sharing options...
USparc Posted November 24, 2001 Share Posted November 24, 2001 The onkyo's have an Absolute/Relative Switchable Volume Display- Absolute provides the output level on a scale of Min(0:no sound) to Max(100: extremely loud), and relative provides the output on a scale which is measured in plus or minus, relative to the calibrated reference volume. ------------------ ------------------------- Receiver: Onkyo 676 DVD: Pioneer DV-525 Screen: Thomson 46" RetroProjection Front: RF-3 tFTP Rear: RF-3 tFTP Center: RC-3 tFTP Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.