Sound level meter: digital or analog?

[hired goon]

G'day,

I want to measure the bass output of my speakers in my room. I've got a Stereophile test CD with 1/3 octave warble tones (down to 20 Hz), and a Radioshack digital sound level meter.

But I seem to recall problems with the digital sound level meter (something to do with having to adjust the results, IIRC). Is that correct? Should I get the analog sound level meter, or compensate the readings from the digital meter?

--Geoff

[Spearmint]

G'day,

I want to measure the bass output of my speakers in my room. I've got a Stereophile test CD with 1/3 octave warble tones (down to 20 Hz), and a Radioshack digital sound level meter.

But I seem to recall problems with the digital sound level meter (something to do with having to adjust the results, IIRC). Is that correct? Should I get the analog sound level meter, or compensate the readings from the digital meter?

--Geoff

Hi Hired Goon

Both meters are on a par as far as accuracy goes.

Head on over to Sonnie Parkers great site on setting up the Behringer BFD and at the bottom are links to different items including audio files for testing and also a spreadsheet for recording your results including the RS SPL meter corrections.

BFD Setup Guide

[whoaru99]

Agreed, both meters are comparibly accurate. Both need correction factors applied if you want to gauge absolute freq. response; especially towards the low end if memory serves.

The analog route seems like one could interpret a little higher resolution compared to the digital meter, but even at 1db res. the digital meter is probably as good as one really needs.

[junior77blue]

I think it's just personal preference....plus the analog is cheaper. I like analog cause its an acutal gauge. Kinda like a speedometer...what would u rather have? analog or digital display?

[PewterTA]

I have the correction tables in my sound meter for the Radio shack digital meter.

When I get home I'll post them on the site here so you have have them for when you do your frequency sweeps.

[PewterTA]

Well I said it and just remembered... Sorry it took so long, here's the correction table.

Radio Shack SPL Meter Corrections
------------------------------------
10hz.....+20db
12.5hz...+16.5db
16hz.....+11.5db
20hz.....+7.5db
25hz.....+5db
31.5hz...+3db
40hz.....+2.5db
50hz.....+1.5db
63hz.....+1.5db
80hz.....+1.5db
100hz....+2db
125hz....+.5db
160hz....-.5db
200hz....-.5db
250hz....+.5db
315hz....-.5db
400hz....0db
500hz....-.5db
630hz....0db
800hz....0db
1k.......0db
1.25k....0db
1.6k.....-.5db
2k.......-1.5db
2.5k.....-1.5db
3.15k....-1.5db
4k.......-2db
5k.......-2db
6.3k.....-2db
8k.......-2db
10k......-1db
12.5k....+.5db
16k......0db
20k......+1db

THX Home Theater 16000 -8.5
20000 -11.2

[Patt]

I have an Analogue.

Dan,
Even knowing it is a correction table ....what exactly is it for without getting too technical on me.....Thanks.

[Spearmint]

I have an Analogue.

Dan,
Even knowing it is a correction table ....what exactly is it for without getting too technical on me.....Thanks.

Hi Patt

I know you directed your question to Dan; this is how the table works...

If you look at the 25Hz for instance is says +5dB

Therefore if you run a 25Hz signal thru your subs and then used your RS SPL meter to measure the output and you got a reading on the meter of 80dB. For this reading to be close to accurate you need to add 5dB because the meter is -5dB down at this point. So although the meter gave you the result of 80dB you are in fact getting approx 85dB at the 25Hz point.

[Patt]

Thanks Spearmint,

So if it says + then I add and if it says - then I subtract the number accordingly.

Thanks, it looked so simple.....and it really is...

[Chris D]

Geoff- the reason that the analog SPL meter is recommended, is that you can see trends and averages on an analog scale that are difficult on a digital. If your digital meter is bouncing between 75, 77, 74, 76, 72, 78, what's the average? You have to think and maybe do a bit of math. But visually on an analog scale you can see that even though the needle jumps a bit, it seems to be centered or averaged around value X. Like somebody else said, even with our current digital technology, this is why car speedometers have stayed analog. I'm a pilot, and digital value readouts in the cockpit are always accompanied by a analog readout of some sort, whether it's a scale, tape measure, or something so you can see trends.

[Lefteris]

I know you have a different kind of conversation, but i was wondering, what's A-B-C-weighting?

Cheers

[Burke Strickland]

the reason that the analog SPL meter is recommended, is that you can see trends and averages on an analog scale that are difficult on a digital. If your digital meter is bouncing between 75, 77, 74, 76, 72, 78, what's the average? You have to think and maybe do a bit of math.

That may be why the digital version of the Radio Shack Sound Level meter has an averaging feature built in. No guess work, no "mental math" -- the machine computes it for you. It can also tell you the peak reading during a set period. I like that better than trying to pick it up off the bouncing needle on the analog model.

For the record, I own and use both models, analog and digital. I've found that each has its place. The purchase price of both together is still not very much contrasted with the total HT cost. (Of course I bought each "on sale", not as MSRP. ) Which to use in which situation gets down too a personal preference in making use of the features of each.

The main thing, though, is to have an SPL (sound pressure level) meter on hand, and to use it frequently to make sure you are playing your system at a safe listening level. That's just as important as the setup calibration which (unless your receiver / pre-pro does it automatically via a connected microphone) is most effective when done with an SPL meter.

If you are working toward a specified level (as in setting the same volume for all channels) then for me, either will work just fine, but I find that the digital meter is a bit easier to use, because once you've hit the "correct* (desired) volume level, you see it on the digital readout -- no guess work.

Ditto for taking averages over time -- the digital's computed average is probably more reliable and accurate than" guess-timating" based on the analog's bouncing needle. That also saves using a calculator or entering numbers into a spreadsheet if you are trying to be really precise.

OTOH, when setting the overall volume level for playing a movie or listening to music, if you are checking for a safe sound level, the analog's bouncing needle will tell you right off if the reading is way high or low and you can adjust accordingly -- you don't need an exact digital readout to know that it is "too loud" (and if it is "too soft", you probably won't hear it anyway.) :>)

what's A-B-C-weighting?

The weighting (A,B,C or D) determines how parts of the frequency range get the emphasis in the measurements. (The most widely used are the "A" and "C" scales.) In overly-simplistic terms, the different curves account for differences in the way human hearing perceives sound.

All of the scales measure the same at 1000 hz, but vary at other frequencies. The "C" weighting" is closest to, but not exactly, "flat". The "A" weighting attenuates the bass significantly, similar to the lower sensitivity of human hearing at those octaves.

By the way -- just because the ear is not sensitive to a given frequency does not mean that it is safe to expose yourself to an incredibly high volume at that frequency for extended periods. That would be kind of like saying that just because my hand is numb (so I can't tell how hot or cold something is), I won't get scalded if I dip it in boiling oil.

For a more detailed explanation of the sound curves, refer to http://www.norsonic.com/web_pages/correlation.html (no sales pitches on that page, just a lot of tech talk).

Burke

[aud19]

I've got a digital (as Ratshack had no analog's available when I purchased) and it works fine :T

[chrispy35]

What weighting does the correction table above apply to?

[hired goon]

G'day,

...here's the correction table

What is the source for these corrections?

The corrections described in the BFD setup guide linked to earlier only go to 160Hz, whereas these corrections go to 20kHz.

--Geoff

[PewterTA]

Here's where they come from...

http://www.danmarx.org/audioinnovation/rsmeter.txt

But here's the pretty HTML link...

http://www.danmarx.org/audioinnovation/rsmeter.html

[hired goon]

G'day,

Here's where they come from...

Thanks for the link. Although, do these correction figures apply to all Radioshack SPL meters, or just the analog meter?

--Geoff

[cuda65]

Thanks for the link. It made it much easier to print out the information. I am looking to get an SPL meter in the next couple days. This will help. :T

[PewterTA]

I believe it will be correct for both the analog and digital sound meters since they are identically made except for how they display the results.

But for the best, there are places that will calibrate the units since each one could be a slight bit different. But I know a lot of people don't want to spend that kind of money to have their meters calibrated.

I used this table with my Digital Radio Shack meter (since I couldn't get the analog since the store was out of them) and my sub sounds much better than with going with the "normal" readings of the meter. So I would have no fear on tellins someone to use this correction table.

This is all for C weighted settings.

[whoaru99]

I jave a program to generate tones that can be used for this purpose. There is an option for mono or stereo tones.

Which would be more appropriate if I were trying to graph the response of my front/main speakers, mono or stereo tones?

[PewterTA]

Mono would probably be better that way you would know for sure that there is no difference going to the left and right speaker.

[Chris D]

When tuning, you want to do one channel at a time. So you'll want something that can repeat equal signals to all your speakers, done one at a time.

[Cracking Oboe]

I have a digital RS soundmeter. I noticed a single RCA output jack on the side of the unit. Does anyone know what it is used for?

Cracking!