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Re: Minimum power for M22/VP100?
Cork #364645 01/24/12 03:20 AM
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Cork, no, even that 90% setting isn't "inherently" bad, since the volume control settings are relatively meaningless with respect to how much power is actually being used. The actual loudness, as measured with an SPL meter, would give more meaningful information as to power being used, since the loudness at a given setting, such as 90%, can vary greatly depending on the strength of the input from the source material.


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Re: Minimum power for M22/VP100?
JohnK #364659 01/24/12 12:59 PM
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Thanks Alan & JohnK, I appreciate the additional info.

With the added info I feeling a little better. (Alan, FWIW, a few drinks puts me at my stated max, one more and I'm either crashed, or doing something I'll regret that doesn't involve using a receiver.) It definitely good to know to stop at 0db.

John, I've wanted an excuse to buy an SPL, so this is interesting. But I don't follow your (implied) equation. Once I have a measurement, how do I equate a db level to how close I am to the receiver's max output?

Re: Minimum power for M22/VP100?
Cork #364708 01/25/12 01:26 AM
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Originally Posted By: Cork

John, I've wanted an excuse to buy an SPL, so this is interesting. But I don't follow your (implied) equation. Once I have a measurement, how do I equate a db level to how close I am to the receiver's max output?


Simple, once you drop the SPL meter in order to cover your ears with your hands, you're probably nearing the receiver's max output.


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Re: Minimum power for M22/VP100?
St_PatGuy #364709 01/25/12 01:26 AM
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Eh, not with a 30 WPC receiver...


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Re: Minimum power for M22/VP100?
Ken.C #364711 01/25/12 01:34 AM
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In that case, it'd be because your wife/girlfriend/significant other is yelling at you to turn it down?

Last edited by St_PatGuy; 01/25/12 01:36 AM.

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Re: Minimum power for M22/VP100?
Cork #364712 01/25/12 01:35 AM
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Cork,

As JohnK indicated, with the level differences in souce material--some CDs are recorded 10 dB to 15 dB "hotter" (louder) than others, so understand that the 0-dB indication on the receiver is very approximate.

Using a dB meter at your listening seat is really instructive. You can measure peak or average levels and equate them to the general subjective impression of most people: peaks at 95 dB or higher are considered "very loud". Levels around 85 dB are "quite loud" and lots of listeners set levels to average between 75 dB and 85 dB. We hear each increase of 10 dB as "twice as loud". A 3-dB increase is described as "a bit louder".

It's impossible to know exactly when your receiver/amplifier is approaching clipping, short of having an oscilloscope with a hold setting. Some amplifiers begin to sound harsh or strident as distortion increases. Certainly you should avoid setting the volume so that peaks at your listening chair exceed 100 dB SPL. By the way, the SPL meter should be set to the "C" weighting, and all of the levels I've talked about are relative to the meter set to "C" weighting.

Keep in mind too, that I've rarely measured acoustical music in concert halls peaking at more than 102 dB (that's with full orchestra and chorus in Carnegie Hall in a very good box seat).

Amplified rock is an entirely different story, and absurdly loud levels are often the norm---well above 100 dB in clubs and live concerts.

Regards,
Alan


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Re: Minimum power for M22/VP100?
alan #364714 01/25/12 02:12 AM
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How often do you bring your meter to Carnegie Hall? Do you bring your metal detector to the beach too? smile


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Re: Minimum power for M22/VP100?
Cork #364716 01/25/12 03:05 AM
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Cork, the digital version of the Radio Shack SPL meter is well-suited for this use. It has a provision(the analog doesn't)for measuring the maximum level reached either briefly or over an extended period. You'd read the max level at the volume setting you usually use and then convert that to power used at that level. To do this you'd start with the sensitivity spec for the M22, which was 89dB for 1 watt at 1 meter distance for my M22s(and I assume yours). Recently Axiom changed this by 4dB to 93dB, and it would be helpful if Ian or Alan would clarify this, since this would indicate better than a doubling of sensitivity.

However, using the previous 89dB figure, it would be decreased by about 3dB per doubling of listening distance beyond 1 meter, according to research reported by Dr. Toole in his book. For example, at a distance of 9-10', about 4dB should be dropped, down to 85dB for 1 watt. So, if a max reading of 95dB was measured this would use 10 watts, if it was 98dB, this would bring it to 20 watts, etc. This follows the formula for power increases which can be summarised as a doubling of power needed for each 3dB increase and 10 times the power for a 10dB increase. This can be done approximately in your head, or a formula can be plugged into a pocket scientific calculator(you always carry one; right?)for more precision, or probably easiest, there are online power calculators, such as this one .


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Re: Minimum power for M22/VP100?
alan #364717 01/25/12 03:19 AM
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Yeah, Alan; as I've mentioned before, I also took my SPL meter to the concert hall a couple times. After explaining to the gentry that it wasn't a bomb and what I was doing(they still thought that I was a nut, but probably not a dangerous one), I did find that even at the max of the most dynamic pieces, the level in the front rows was a few dB above 100.

Incidentally, it would be interesting to hear about the 4dB increase in the sensitivity specs which I commented on above.


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Re: Minimum power for M22/VP100?
Cork #366053 02/08/12 05:52 PM
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Once again, sorry for asking a question and not responding. I've been camped out work. (I'm starting to believe my boss is on this site and feeds me more when I post.)

I tried to get a Radio Shack SPL, but of course my Radio Shack didn't have any, so I order this (cheapo) one from Amazon. I figure it'll let me play. And thanks again Alan and JohnK for the added info.

http://www.amazon.com/gp/product/B005JX2EZ2/ref=oh_o01_s00_i00_details

Alen mentioned the reciever going harsh or strident when reaching its limit. I've had solid sound up to my required range. Although last night the thing needed to be reset (plug pulled out) because I lost all button responsiveness (receiver and remote). When I turned it back on it went into a 15 minute reset sequence. So THAT'S not making me feel very comfortable.

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