Axiom Home Page Forums General Discussion Home Theater SPL Meter Measurement

How do you folks use your Radio Shack SPL meter when you are calibrating your speakers? Do you:

1. Aim the meter at each speaker?

2. Just point it to the front and make all measurements from that single postition?

3. Point the tip of it vertical and make all measurements?

Just for reference, the instruction manual says to aim it at each sound source.

I'm just curious.

The instructions that came with my RS meter said the mic is designed to pick up 360degrees around the testing position. I place mine ear height in the primary listening position facing up. Sometimes I use a tripod and crouch down not to interfere with the surrounds mounted on the ceiling. Other times I sit and hold the meter up with one hand and control the remote in the other hand.

If you think about your ears, you don't turn your head and face each speaker when your watching movies or listening to music, so you really don't want to point the device at each speaker. Of course, this is just my opinion, let the bashing begin....

I do #1.

And I've done #s 2 and 3.

#1 seemed to work best for me.

Here is a quote from the below article on Audioholics.

"Step 7 Sound Pressure Level (SPL) Calibration
Place the SPL Meter at the listening position at ear level with the Mic end pointed toward the ceiling. Select “C” weighting, response slow then, turn the dB dial to 70. Activate the internal pink noise generator of your Receiver and select manual test tone. Now adjust each speaker to +75 dB reference. When you are adjusting the surrounds make sure your body is not in a direct path of the speaker and make sure the house is quiet. When doing the calibration, only the test tone should be heard (A/C, ceiling fans, ect. should be turned off). I like to adjust the subwoofer level to + 80dB for wow effect. Your taste may vary."



http://www.audioholics.com/techtips/setup/loudspeakers/loudspeakerplacement01.php

Bernard, unless there's been a recent change, the meter's supposed to be omnidirectional; so 3. would seem to be the way to go and it's what I do. Note that at a typical listening distance there's actually a bit more reverberent sound pressure from reflections than there is direct sound.

Interesting assorment of opinions.

What started me to thinking was the Onkyo setup had a mike that appears to be pointed straight up. I did a manual setup yesterday with the RS SPL and some of the settings were a few dB different from that of the automatic Onkyo setup. I began to wonder why.

I'm going to "play" with the RS meter and see what, if any, difference it makes.

My Denon mic setup also gives me slightly different results than my SPL meter when I calibrate to 75dB's.. I'm not sure when the receiver runs its tests what dB levels it is trying to achieve?

With my Denon mic the sub distance is always wrong. Usually by 15-20 feet.

I think Alan has mentioned that the sub will be different than an actual tape measure distance. It has something to do with the internal circuitry of a sub?

According to the Denon manual, speakers with a built in filter such as a sub might be set with a value that differs from the physical distance because of the internal electrical delay.

Number three here.

So do you change it to the correct distance or leave it alone?

I left mine alone and it sounds great.

Well, I moved the speakers around the other day, so I guess it's time to play with the set-up again anyway.

Here is an interesting article (allbeit 4 years old) from Stereotimes Magazine that ties-in.

Thanks for that article, but I don't think that I am going to convert my SPL. I like it just the way it is.

I have the RS digital meter. Setting up was straight forward like using the meter with the dial, but how do you measure how loud your sound is? My meter has no dial to turn to zero, all it has is a digital readout I believe 60 on up to 120.I'd like to know how loud my system is playing. Thanks for any info...

Does your meter look like this one?

Yes... That's it

Izub, the dial on your meter merely sets the range of the scale for the digital readout. Notice that just beneath the window for the digital readout, you can see 3 little numbers in white, -10 on the left, 0 in the middle, and +10 on the right. When taking measurements, as the volume rises and lowers, you can see a little line of black squares moving across the display in the readout just above those numbers, and below the large digital numbers. This line of squares is indicating where the volume is in the range of the scale to which you have the meter set

If, for example, you set the dial to the 70 scale , then the range dB range the meter will read is between 60 and 80 dB with the 70dB point right in the middle of the range (where the "0" is) .

Right now, with my meter set to the "60" dB scale, my meter reads 54db. When I count the number of little black squares showing in the range beneath that number, I see 5. The first square represents 50dB, and each square represents one more dB. So the 5th square, indeed, indicates 54 dB.

If the volume of whatever you are playing, be it test tones or music, or whatever, falls below the range of the scale to which you have set the meter, the digital readout will read "LO" meaning that the volume is too "LO"w to be read on the 70 dB scale. If you then set the dial to "60," you'll see a readout again. If the volume goes above 80 dB, the digital readout and line of squares FLASHES indicating the volume is too high for the 70 dB scale. Just move the dial up to whichever setting will give you a steady digital readout rather than a flashing readout. (see pages 13 and 14 in the meter's manual)

So, if you are trying to simply see how loud your music is, with the music playing, find the dial setting where the readout neither reading "LO," or is flashing. The numbers will be changing because music is dynamic and it's volume itself will be changing, but with the weighting set to "C" and the response set to "slow" you'll get an approximation of your volume.

By the way, the response on the meter defaults to FAST each time you turn it off. So, if you want the SLOW response, you must set it to SLOW each time you turn the meter on (mumble grumble).

I'm sure someone else could have explained this more succinctly, but I hope it helps. If you are still confused, be sure to say so and ask questions. We'll get you up to speed one way or the other.

I haven't bought an SPL meter yet largely because I didn't have a clue how I would use it.

After reading your post I feel I could easily do it. Nice job on explaining it.

Thank you, Ken. Nice of you to say so. I didn't think I did a particularly good job, but I'm glad you felt differently.

Ajax thanks.I did follow another post on calibration which came out very close to my amp. You explained it great. I see that when I crank up some tunes they approach 90 on peaks. I may cut back a little on that . I think Randy posted a chart on a thread on db levels and max hours before ear damage.

Ajax i just found the article off the thread. Here they say to check volume by A setting (that's where my confusionwiththe dial and the zero came in) If I use what you said c and slow and then use A and slow The C reading is substantially Louder....What to do?? Not sure i understand the difference in A and C weighting I guess it's in the range of sound (Higher tones?) Thanks for any clarification...Here's the link
http://audiophilia.com/hardware/spl.htm

From The article:
While simulating the volume level of a large rock band or full symphony orchestra in your listening room can be a lot of fun, remember to keep an eye on those SPL's to ensure that they are within safe levels. The following table from the U.S. Department of Labor (also included in the excellent documentation accompanying the Radio Shack sound pressure level meter) gives data on permissible sound level exposure.
To use the Radio Shack sound pressure level meter to ensure that you're listening to your system at a safe level, first set the meter's weighting and response switches to the 'A' and 'SLOW' positions respectively. Play some music on your system at your normal listening level (no cheating now!) and adjust the setting on the meter's rotary dial such that the average reading is around 0dB. Note that a setting which is too low will tend to "peg" the needle to the right, possibly damaging the meter. Given an average reading of 0dB, your measured listening level is given by the setting of the meter's dial. For example, if the meter has an average reading of about 0dB and the dial is set to about 90dB, then your listening level is about 90dB. According to the table above, you can safely listen at this level for about eight hours per day, although I would use this table merely as a guide and let common sense prevail. Making a habit of using the sound pressure level meter to measure the average sound level of your system at each listening session is a simple way to ensure that no harm will come to your hearing through regular use of your audio system.

Anybody buy a meter in Canada? If so, where? Radio Shack (now circuit city) doesn't sell them here.

Sorry, not meant to be a hijack.

A is for 500-10,000 HZ (voice recordings)

C is for 32-10,000 HZ (full range musical material)

You normally want to us C IZUB...

Thanks SirQ and Ajax that explains it clearly....Just curious Does anyone listen to loud music?dvd in the 90 db or above level? That's what I get sometimes in intermittent readings (A max on the meter)

Radio Shacks carried them last time I looked (about 6 months ago in Toronto, or whenever they became The Source). They were out of stock about half the time, and if you asked the staff they would assure me they had never sold SPL meters.

Always a big surprise when I brought them up to the counter

I have to admit, I can't find the SPL meters on the Source web site. Then again, I couldn't find it on the Radio Shack site either.

Does anyone know if the Source was able to keep getting access to Tandy/RS's house brands, or did they have to find new sources for everything ? If the latter, I guess you're driving to Buffalo.

If you're in Toronto, you can borrow my meter.

EDIT - whoops, you're in Thunder Bay.

I bought the floor model because they were out of stock They extended the warranty to 5 years....

I agree the RS or Source SPL meter is not online or in hard copy. But I did find these on the 'net.
The best price
Aperion
Galaxy
Nady
Audio-discounter

Zub, on the difference between A and C weighting. SPL meters have filters which intentionally roll off the frequency response(no "correction" necessary)at certain frequencies and at certain rates. The idea is to give a result that more closely matches what humans actually hear, since hearing ability is less for very low tones and very high tones than for the mid-range, and this difference increases as the sound level gets lower(Fletcher-Munson curves illustrate this). The A weighting roughly corresponds to hearing at very low sound levels while the C weighting corresponds at high sound levels and is usually suggested for use when calibrating audio equipment at a fairly high level. The curves and table shown on p.4 of this lab handout from Michigan Tech illustrate the differences. So, among other points, note that published "corrections" for the RS meter at very low frequencies don't in fact relate to meter inaccuracy, but the inaccuracy of our ears.

Greg, one point of interest that I noted on the Nady link is that Monster Cable has available a 9 volt alkaline battery for the meter for a mere $8.14, so maybe we should all stock up.

Interesting...Why then, did the article then suggest to use A weighting if it's lower, when we all seem to agree that C weighting will mpore accurately tell us how loud we are listening?

Thanks Greg and John.
I'll check RS again, otherwise one of Greg's links.