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Explanation Required - AV Receiver Volume Control

 

Alan Kirkelstein
Unregistered guest
I bought my 1st AV receiver, a HK AVR 125 recently.

I have 2 questions about its volume:

First, where can I get an explanation as to why the decibel counter on the front-panel information display is a negative number that becomes a larger negative number as I increase the volume. Without speakers connected, the decibel display shows minimum volume of -80 and maximum volume of +10 with comfortable listening volume showing negative decibels.

Secondly, I am confused about and would like to have an understanding of the procedures for determining the half way volume point to see if I am asking too much of the AVR 125 with regard to my speakers. HK offer the following comment - "There is a very easy way to determine if you are asking too much of your amplifier. Follow these directions to perform this test:
Set the Bass and Treble knobs in the middle (flat).
Make sure all Equalization buttons are turned off (loudness, EQ, contour, etc.).
Put on a CD.
Turn the volume halfway up (electronic volume controls/ display would read 0dB).

If you normally listen louder than this, chances are you are pushing your amp too far, causing it to clip and blow the speakers. Generally speaking, when listening to CD, VCR, DVD, or Laserdisc, you are at maximum clean listening volume when you reach the halfway point on your volume control."

I found the above comment in the section titled General FAQ's under the question "I keep blowing my speakers...". see http://www.harmankardon.com/faq/showFaqanswer.asp?faqId=230

I am not clear on how to figure what the half way point of the volume control would be as the volume knob free-wheels and the display of +10 to -80 decibels doesn't make sense to me.
Tks - AA
 

New member
Username: Geekboy

Post Number: 86
Registered: 12-2003
Alan: welcome to home theater! The measure in decibels (dB) on your receiver's display (volume knob) is relative to "half power" on an H/K receiver. (Other vendors may only allow the volume control to go to 0dB, so the half-way point (in volume) can be interesting to find if the vendor doesn't state it in the book!)

That is, on an Harman Kardon AVR-525, a volume reading of 0dB would yield 35W per channel (in 5.1 or 7.1 channel mode). (This assume that the channel adjustments are not set to +/- dB in the OSD, the bass and treble are flat, and no special EQ functions are present.)

Why is 0dB halfway? Because that's the way H/K setup their volume control. The formulas about this are so complex... but, generally, the +10dB would effectively be DOUBLE the volume from the 0dB reference point.

I generally, on my Harman Kardon AVR-525, listen to TV at -30dB to -35dB. I listen to stereo CDs at about -35dB to -40dB, and to 5.1/7.1 channel movies (dvds/laserdiscs) at -15dB to -20dB (Dolby Digital... my DTS stuff seems to be very loud at -20dB).

What H/K is suggesting by the documentation is that IF you have the receiver's volume at 0dB and you "think" you still have to turn up the volume to get to your "comfortable" listening volume (ambient volume), then you're in danger of "underpowering" your speakers. Generally, most home installations never require more than 40W of power for speakers. Even my 70W x 7 Harman Kardon AVR-525, never sees a volume setting ANYWHERE near the half point (according to H/K) of 0dB.
 

Alan Kirkelstein
Unregistered guest
OK - Let's see if I got it!

My old stereo receiver displayed volume settings in a positive numeric progression (low = 1, mid = 20, etc.) This is no longer the case with the new AV's. They do not use a numeric progression. They limit the maximum volume to 50% of the possible range and display a scale.

Not very user friendly against a background of user experienced in radio & TV dials with there increasing numbers. Does this new format have any relation to the definition of decibel?

Thanks for the info.
 

New member
Username: Geekboy

Post Number: 88
Registered: 12-2003
Alan: yeah, I understand the confusion. I was use to the old stereos with a volume knob which went from 1-10 or 1-20 (with the higher number being the higher volume). I personally don't know why they went to "relative" volume. (I think some receivers you can tell it whether to display relative or absolute volume.)

The format has some relation, but not directly. The reason I say some and not directly, is due to a.) efficiency of your speakers, b.) distance from you to your speakers, and c.) other factors (anechoic vs echoic room).

They are not limiting the maxium volume to 50% power. It's realy difficult to explain without understanding speakers, speaker efficiency, and the relationship of decibels to watts (power) to perceived volume. What H/K is saying is that at 0dB (relative volume) on the receivers display, they are providing 1/2 of the rated amplifier's power to the speakers. For my AVR-525 that's 40W-50W (actual).

Speaker efficiency is measured as the sound pressure level generated at 1 meter (~3ft) with 1 watt of power applied. Most speakers are 89-92dB efficient meaning that they'll produce 89-92dB of sound at 1M (1 meter = ~3 feet) with 1W of power. If you're 3M (3 meter = ~10 feet), the decibels produced by the same speakers falls by ~ 10dB. The power required to listen to those speakers at the same sound level as at 1M (1 meter = ~3 feet) would require 10W.

For every additional 3dB of sound, you must DOUBLE the power supplied to the speaker. (They say that 3dB is what a human can "perceive" as a change in volume.) For a human to actually hear a "doubling" of the volume -- although 6dB would be mathematically accurate -- it takes 10dB for the human to perceive a doubling of the sound.

Distance from the speaker also plays a role in this because for every doubling of the distance from the speaker... 1M vs 2M... requires a doubling of the electric sound (6dB). Add all this up, and you see why you need more than just 1W to listen to your system at 10ft (3M) at 90dB. As I wrote earlier, most home theater systems with pretty efficient speakers, can deal with most needs with 40 - 50 watts. But, when you need to increase the dB levels from say 100dB to 110dB (ouch, my ears) on the same system, you'd have to multiply the power requirements by 10! (Your system now needs to produce 400 - 500 watts!)

Since your receiver's "relative" volume is expressed as relative decibels to (for H/K at least) half the rated power of the amplifier, there is a relationship between the volume setting and the power being applied to your speakers.

I know, that doesn't help much, but may help you. It would probably had just been better if I answered: yes. :-)
 

New member
Username: Creed

Post Number: 12
Registered: 01-2004
does that means setting the volume as '0 db' at my Marantz receiver is its reference db level?
 

New member
Username: Geekboy

Post Number: 90
Registered: 12-2003
Gan: I don't know for Marantz. Each manufacturer does it differently. I think that on Yamaha, the highest is 0dB. If your setting goes beyond 0dB to, let's say +10dB, then the answer, probably, is yes.
 

New member
Username: Creed

Post Number: 13
Registered: 01-2004
yeah, my receiver volume range is from (-infinity to +18db)
 

Alan K
Unregistered guest
Here's a statement from HK on the relative volume with its negative/positive scale. "When the receiver is at 0dB, it is running flat out with the lowest distortion levels. As it increases into the positives the distortion also increases along with the power."

As to why the use of relative volume vs absolute, it becomes apparent that the benefit of this method would lessen the danger of blowing receivers and speakers. HK advised me that "As far as the negative dB, also very logical design feature."(sic) To now, this wasn't a benefit for me as the feature isn't mentionned in any of the supplied product literature that came with the unit. This info isn't on the HK web site. I had to ask the question on this forum & of HK tech support. Am I alone or are there others without understanding of relative volume control scales?
 

New member
Username: Geekboy

Post Number: 93
Registered: 12-2003
You're not the only one Alan. The way that "decibels" work is logarithmic... so unless you are studying electronics ... it's just too overwhelming! The H/K technie is correct though, you want to be at comfortable listening for YOUR particular speakers, room, setup, whehn the receiver is at its lowest THD (Total Harmonic Distortion). As you approach maxium rated power, the THD increases (H/K AVR-525, for example, is 0.07% THD at 70W). So, that means that after +3dB (which is DOUBLE the power (in watts) to get a +3dB raise in SPL (sound pressure level)), my AVR-525 goes from 35W to 70W (rated power). When you cross this and start getting to 1.0% THD (and clipping), it's all over. This is probably at +6dB on the H/K volume scale... since my AVR-525 would be trying to do 140W (DOUBLE the power (in watts) to get another +3dB raise).

Why isn't it mentioned as a feature... because it's not really a feature, per se. It's just the way manufacturers have decided to help us with volume control on our receivers. That way, when you call and say "I listen to my receiver at +9dB all the time. Why did my speakers blow?" They can say it's your fault. :-)
 

Alan K
Unregistered guest
geekboy - your participation in this forum is terrific, interesting & appreciated!

Up above in my first post, HK comments "Set the Bass and Treble knobs in the middle (flat)." Is flat the optimal setting? Or, does this mean that the bass and treble should be dialed up to full amount for the sound quality to improve beyond flat? Or, is this another of those words that has its own secret AV definition?
 

New member
Username: Geekboy

Post Number: 94
Registered: 12-2003
Optimal, not really. They're just saying that to not skew the 0dB reading on the display, the signal can't be "enhanced" in any way. If you set the bass high (past dead center) then you're increasing the lower frequency output, and could cause the receiver to use more power than what the "reference point" at 0dB is.

The words aren't so much secret... "flat" just means that there is no accentuation or attenuation of the signal. Equivalent to taking an Equalizer and setting all bands to "0" -- if you're familiar with EQs.
 

Alan K
Unregistered guest
Is there any correlation between "flat" bass & treble settings and the AV industry's Watts war? I mean, do the AV receiver manufacturer step-down or strip out some of the bass & treble from the incoming signal to make the sound flat? Wouldn't that mean they could show more watt capacity? Wouldn't that also mean that for fuller (less flat) sound, bass & treble have to be turned up?
 

Anonymous
 
geekboy:
I really enjoy your contribution to this forum (and others). You are very knowledgable in audio/video. I have a HK 525 and I am afraid I may have blown my Boss acoustimass speakers by turning the volume to +5 db.
Thanks for your explanation. Your time and sharing are highly appreciated.
I would like to see more of your comments.
 

New member
Username: Geekboy

Post Number: 95
Registered: 12-2003
If you listened at +5dB alot, you probably drove your speakers to clipping, which may have damaged them. If your +5dB setting was extremely short in duration, maybe you didn't suffer any damage. I use to have the Acoustimass 11 system, but have since upgraded... to Paradigm.
 

New member
Username: Unicronwmd

Post Number: 35
Registered: 12-2003
Hey Geekboy,
I am still trying to decide between the Yammy 1400 and the HK 430. What are your opinions and do you know the best place to buy either one? Thanks man,
WMD
 

New member
Username: Geekboy

Post Number: 96
Registered: 12-2003
WMD: I've never used any Yamaha products. I use to dream of them though... does that count? I have heard positive things about the RXV1400, but, as you know, I'm an H/K man. Depending on your speakers and what you like... I'd probably still recommend the H/K product. :-)

Yamaha has all those crazy DSP modes, though, which always intrigued me. Plus, their build quality is pretty good. Unfortunately, I don't give recommendations for/against products I don't know that well... just doesn't seem fair. Brand bias/loyalty is always a factor on these boards. I'm a firm believer in a.) narrowing your choice down to 2 or 3, b.) trying them out (in your home if possible), c.) weighing the costs (feature/benefit analysis, d.) making the final decision. The biggest part, I think, is the feature/benefit analysis. You may find the features in the Yamaha more to your liking over the "plain and simple" H/K line.
 

New member
Username: Geekboy

Post Number: 97
Registered: 12-2003
WMD: sorry... where to buy? I always trusted OneCall (OneCall.COM) for my mail-order stuff. Trust is the key word here. Secondly, you want to make sure it's a factory authorized dealer. If buying from a retail location, it's tough to beat CostCo. They have a "forever" return policy.
 

New member
Username: Unicronwmd

Post Number: 36
Registered: 12-2003
Thanks man, I went to OneCall and they had the HK 430 for $899. I can get the Yammy 1400 for $670. I'll see what I can get the HK for here but I don't know if it is worth the extra money:-(

I think I might be able to get the HK over here for $799 but I don't know if it would be worth $130 more then the 1400.

I guess we'll see what happens.

Thanks man,
WMD
 

Alan K
Unregistered guest
Try Froogle.com - a Google subsidiary

The 430 starts at $620 - not $899! The yammy is probably there at a much better price.

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