Rat Shack dB meters- how good?

[formica]

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On 9/25/2004 7:16:37 AM William F. Gil McDermott wrote:

The next time you go to a rock concert and things sound distorted, fashion some earplugs from paper and saliva. In my experience, the music becomes more clear.

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You must be married... and for quite a few years... right?

I'm just not too sure a date I'd bring to a rock show would be very impressed by "paper and saliva" ear plugs... well at least not for a first date.

Rob

[WMcD]

As a matter of fact I'm not married.

On the other hand I'm not so proud that I'll risk hearing to appear cool. Not that I have ever achieved coolness in any case. Maybe that's why I'm not married.

Smile.

Gil

[3dzapper]

Gil, you are not alone. Once at an outdoor rock concert, it was so loud that I stood in a line of 100 people just to get some TP out of the porta-jon. I didn't worry about being cool. I had just gotten done with my hitch in the USAF fixing jets. My ears never hurt near them but that concert had me in pain. What is the threshold of pain, 128db+?

By nightfall they had adjusted the sound better and boy did Rufus with Chaka Kahn and Ten wheel Drive with Genya Ravan put on killer sets!

Gil, have you ever heard of an very successful attorney in Providence,RI named Arum Sheffron? He was the bass player in Ten Wheel Drive.

Rick

[DrWho]

110dB is the range that pain starts to occur, but it depends on the person. 120dB is where permanent damage starts to occur. (Though prolonged exposure to 115db will start to create damage).

I've read recently some other articles from health organizations that disagree with my numbers, but I'm just telling you what I've always been led to believe. I personally start to feel discomfort around 98dB. (good thing mixers generally get to sit in the back)

[WMcD]

Sorry, I never heard of Arum as an attorney. OTOH most of my work is in the mid-West and West. Doubtlessly he's never heard of me either. Smile.

The distortion and earplugs ploy was at the Dallas Schmernoff pavillion while seated inside but toward the back. Once with Moody Blues and once with CSN. Not exactly headbangers. I can't say it was physically painful. But it sure was irritating.

Maybe this was mostly a matter of distortion and the plugs cut down on the high frequency components. The music sounded much better . . . not distorted music at a lower level. And it may be a matter of aged ears.

In any event, OSHA standards are no comfort to me and OSHA is not going to solve any problems which might result. In my view, it was a problem worth addressing.

= = = = = =

BTW I did check out Media Player (bars something display) with the Sound Check II test CD. It has one-third octave noise. It looked to me that maybe the lowest bar was not as low as 20 Hz and the high one was not as high as 15 kHz. OTOH, the pink noise did push them all to the same level, with some dancing around to the noise.

It is a cheap thrill if you have any sort of test CD and a computer with XP.

Best,

Gil

[formica]

The theoretical "Threshold of pain" is given as 125 dB in most text books, although I agree with drWHO that lower levels will lead to damage, depending on exposure.

Rob

PS: Gil, I hope you didn't take my poking too seriously... I was just keeping things light.

[colterphoto1]

I've been keeping the meter handy on a light stand next to listing position. Looks like I tend to have avg 'everyday' listening level of about 74-80 dB 'C' weighted. Seems loud enough while allowing conversation without shouting. Anything more demands your attention. From the thread, them seems adequate without causing distortion, listening fatigue or damage of any sort. Think I'll just stay here for a while.

Wish I could say the same for the idiots driving past my home with their car stereos blaring! Getting tired of hearing them inside my home with windows shut! What about MY rights!

[radiob]

Mine works good!

[3dzapper]

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On 9/27/2004 10:04:24 AM radiob wrote:

Mine works good!

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HUH?? WHAT?? I CAN"T HEAR YOU!!!!!

Rick

[IB Slammin]

Yep. Thats what mine looked like just before the K-33 coil jumped out of the gap. Ooops!

TC

[lo123]

Reading thru the posts for this thread I have not seen a discussion of the Radio Shack digital versus analog SPL meters. Their web site shows both available. Is there an advantage to one or the other type for balancing a 5.1 system?

[WMcD]

Hey Formica, that's okay. It was good for a chuckle.

Gil

[mbajner]

I've heard that the analog model is the way to go

search around the internet on the RS meter

there are charts and also a CD test disc to compensate for the RS meters shortfalls

[formica]

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On 9/29/2004 7:46:01 AM mbajner wrote:

I've heard that the analog model is the way to go

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There seems to be an online preference for the analog meters as many users feel it's easier to visualise the SPL swings. Its like the general preference for analog car gauges vs the digital dash. Although only digital ones are available in Canada... I opted for importing at extra cost, an analog one because of the recommendations.

The digital meter offers some features not found in the analog one like "peak hold", etc... In hind-sight, I think the extra features (and the slightly lower cost) would have been more useful to me, than the analog needle.

In other words, no REAL difference..

Rob

[MPNX2]

Ok I have been following this topic as well and I have a question. I understand the 2.8 or 2.6 volts is one watt. So I got out my VOM and I used the AVIA DVD and just turned on pink noise to the left front channel and turned my reciever(HK AVR7200) up until 2.8 volts were read on the VOM. I then looked at my SPL meter and it was between 97-99 from 3ft or 1m which is within spec of my RF-35's. My question is this I had to turn up my reciever about three quarters of the way up to get 1 watt but my amplfier is rated at 110X7 channels. So why would it put out only 1 watt or 2.83 volts at 3/4 of the volume. Obvisouly the reciver isnt going to put out 308 volts (110watts X 2.8V)so are they using different scales whay not use the same scale for both or maybe these are totally different ratings? Why not just say my HK AVR7200 is rated at 1.5 watts max instaed of 110? Just looking to understand how this all works....

[DrWho]

The reason you have your dial up to 3/4 at 1 watt is because the dial uses the dB scale and the output of your amp is measured in watts...The dB scale is logarithmic (i think a change of 6dB = doubling the power...or is it 3dB or 10dB? i always get it backwards).

Anyways, after one watt at 3/4 of the way up...each 6dB turn of the dial is going to result in doubling the power. If you've got at least 20dB left in that 1/4 turn of the dial, then your output will be up to about 110watts (which is what your amp is rated at). If 1/4 turn = 20dB, then a full turn = 80dB which is actually a typical range for a volume knob (-80db to 0dB, and sometimes up to +10 or +15 dB).

I hope that answers your question; i know i explained it like crap

Btw, there is no reason to multiply 110 watts by 2.8 Volts...the answer gives you 308 volt*watts which is a meaningless term. If your reciever is putting out 110watts and you divide by a theoretical 8ohm resistance, then your reciever is putting out 13.75 volts. For some reason i feel like my math is screwed up. it's been so long since i've had to use these forumals. V=I/R right?

[lynnm]

As mentioned by the good Dr. the volume scale on the reciever is not ( and cannot be linear).

In order to double the acoustic output of a speaker reproducing a 1000hz tone as measured at 1 metre ( 3 db ) it is necessary for the amplifier to put out twice the power.

For Khorns which are rated at 104db/meter @ 1 watt this translates to:

71db requires 1/1088 watt

74db requires 1/544 watt

77db requires 1/272 watt

80db requires 1/136 watt

83db requires 1/68 watt

86db requires 1/64 watt

89db requires 1/32 watt

92db requires 1/16 watt

95db requires 1/8 watt

98db requires 1/4 watt

101db requires 1/2 watt

104db requires 1 watt

107db requires 2 watts

110db requires 4 watts

113db requires 8 watts

116db requires 16 watts

119db requires 32 watts

122db requires 64 watts

etc.

Bear in mind each 3db represents a doubling of acoustic output so a 3db increase is not a trivial thing.When one considers that most music listening realistically occurs in the 60db-70db range,It can be sobering to realise that a 1kc tone at 110db is actually about 35 times as loud as that same tone at 70db and demands about 70x as much amplifier to produce.

Most speakers are rated at about 90db/1watt/1meter@1hz. Thus:

72db requires 1/64 watt

75db requires 1/32 watt

78db requires 1/16 watt

81db requires 1/8 watt

84db requires 1/4 watt

87db requires 1/2 watt

90db requires 1 watt

93db requires 2 watts

96db requires 4 watts

99db requires 8 watts

102db requires 16 watts

105db requires 32 watts

108db requires 64 watts

111db requires 128 watts

etc.

Thus most makers will set the 12:00 on the volume scale at some value that will result in an averagely efficient loudspeaker putting out something in the 70 db range. This can only be a guestimate given the wide range of efficiency of speakers on the market.

Don't trust the scale on the volume scale...Trust your ears.

[formica]

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On 9/29/2004 5:41:34 PM DrWho wrote:

i think a change of 6dB = doubling the power...or is it 3dB

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As lynnm mentionned... each doubling of power is about a 3db increase in volume. (I use the word "about" because efficiency does drop with increased power). The chart lynnm posted are theoretical values...

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it's been so long since i've had to use these forumals. V=I/R right?

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Ohms Law is actually V=IR or P=(I^2)*R

V= Voltage (volts)

P= Power (watts)

I= Current (amps)

R= Resistance (ohms)

later...

Rob

[richinlr]

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On 9/26/2004 9:18:54 AM DrWho wrote:

110dB is the range that pain starts to occur, but it depends on the person. 120dB is where permanent damage starts to occur. (Though prolonged exposure to 115db will start to create damage).

I've read recently some other articles from health organizations that disagree with my numbers, but I'm just telling you what I've always been led to believe. I personally start to feel discomfort around 98dB. (good thing mixers generally get to sit in the back)

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Have a look at OSHA requirements and info on SPL. Hearing damage can occur as low as 90 db. The main ingredient in hearing damage is not the peak SPL but HOW LONG you are exposed to a given SPL.

Can't remember the numbers but there is some kind of table somewhere that will give you information like 'a 2 hr. exposure to 95 db will require 4 hrs. for the ears to recover and a 4 hr. exposure will cause permanent damage' As the db's go up the max exposure time for hearing damge goes down and the recovery goes up.

As the professors say, finding the actual chart is an exercise left to the student...

[jonwolfe]

http://www.rivesaudio.com/home/home.html

Check this site out. I have an analog Radio Shack analog meter and with the CD that Rives Audio sells you can get very good results. THey have 'skewed' the frequencies so that the readings will be correct for the analog rat shack.