# SPL Meter

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#### Andy_Leviss

##### Active Member
It depends on how accurate you need; the Radio Shack ones are accurate within about 2 dB, although their response isn't perfectly flat. They're good enough for an idea of what you're putting out, but not usable as evidence, for example, if you get sued or are dealing with legally imposed limits.

Smaart needs to be calibrated to be used to measure SPL, otherwise it's just giving you dB FS measurements, which are useless without knowing how they reference to your preamp and mic. Also, Smaart does NOT give you the option of setting up multiple mics for other zones inherently; to do it you either need to use an external switcher/mixer or us a multi-channel soundcard with twice as many inputs as you want to use mics, and Y your reference signal into one channel of EACH pair, and then switch which pair is your active pair in a preferences setting in Smaart.

They've talked about multi-channel support in a future version, although I don't know if that's actually coming soon or not, right now it's still just stereo support. Meyer's SIM is the one that currently offers multi-mic support, but at a much higher cost of needing dedicated hardware, including the computer.

Of course, that's all way overkill and out of the price range if all you want is SPL measurements.

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#### Peter

##### Well-Known Member
I dont know much about this, but one review on zzounds does point out that the low frequency limit is 125Hz, which does seem rather high for a low limit... might be something to compare with other meters

#### The_Guest

##### Senior Team Emeritus
Andy, I should have clarified that with any computer program you can use multiple mics for metering different zones via as you said splitting the signals. Which is an advantage over a hand held meter because you can get readings at FOH without walking around. And it's not always possible to have a runner walk around and gather readings (particularly theater and formal settings you can't walk around). You mentioned that Smaart SPL meter is not accurate without calibrating (obviously, nothing is accurate unless it's calibrated). But is there a reason why one would not calibrate their smaart rig before use?

As for the galaxy unit, the 125Hz cut-off normally wouldn't be that big of a deal for a cheap meter. But for $50 that's skimping. Even though your low freqs require lots of power, they don't have the volume and throw like your higher freqs will. When working with volume limits, it's usually the HFs that cause the disturbances to your neighbors (HF travel futher/directional, LF tend to emit in all directions and are tougher to throw). So it's not always the bass that is creating all that volume. Think about it, why is a snare louder than the kick? HF travel more than LF. I'd advise not to get the galaxy if you have limits set on you, and plus it's$50 meter (~10 bucks more than the radioshack) that probably cuts off way before the 'shack unit does. The unit will do the trick if just want to know what you're hitting for the hell of it.

I forgot to include one thing. When mixing under volume limits, the method/policy of measurement is often not at the engineer's discretion. So getting a meter just for this app isn't the greatest move unless you know all promoters you work with will accept you're measuring methods/standards. So if you're looking for something to cope with limits, check with your promoter or local standards. But then again, it's only 50 bucks, and it's nice to play around with. But it's word will not always be interpreted the way you'd like it to.

#### AVGuyAndy

##### Active Member
Just get the RadioShack one. I have one and it's great.

#### avkid

##### Not a New User
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I basically need it for consistency testing, we have a real problem with the balcony speakers!

#### Mayhem

##### Senior Team Emeritus
The one that I have is similar to the Radioshack ones discussed here. I use it mainly as a reference to see how the sound is in various areas of a room. I run a mobile DJ service and so the room size and shape varies from gig to gig.

Whilst (as already pointed out) these will not hold up in a legal dispute, it is often enough to show the reading to those responsible for ensuring a certain level is not breached. In fact, in the few venues that do have noise restrictions, I tend to aim for 5db below their limit.

I think this type will provide a cost effective option for the majority of people who want to check their SPL.

Not sure that I fully understand the problem that you are hoping to rectify with a SPL. Perhaps you might like to explain the consistency problems a little better?

#### Andy_Leviss

##### Active Member
The_Guest said:
You mentioned that Smaart SPL meter is not accurate without calibrating (obviously, nothing is accurate unless it's calibrated). But is there a reason why one would not calibrate their smaart rig before use?

Yup. To accurately calibrate it, you need a calibrator, which is a small device that generates a 1 kHz sine wave at exactly 94 dB, and has a coupler to fit the head of your microphone. You put it up to the mic, set your preamp at a usable level, and then see what reading it comes up with. You calculate the difference between that and 94 dB, and enter that into Smaart as the calibration offset. Aside from being time consuming, you're going to pay a minimum of $300-400 (the one model that SIA sells directly costs$425).

The other way to calibrate it requires that you have an SPL meter that's already calibrated; then you can hold it right next to the measurement mic, play noise through your system, and match Smaart up to the meter. This obviously isn't as accurate as using a calibrator, but it's often "close enough" depending on your needs. Bear in mind that if you're using a meter that's already "just close enough", this is going to add even more error into the equation. Not to mention that it takes longer than using a calibrator.

So, in other words, you're probably not going to be calibrating it each time, unless you have invested the money in a calibrator and need those measurements; for normal system analysis/tuning usage, you don't need it calibrated.

--A

#### jkowtko

##### Well-Known Member
Has anyone picked up one of the yellow and black ones on eBay? They're a brand called "wow2buy" and the look like clones of the Radio Shack model. but under $30 including shipping (vs.$40-45 + tax for RS).

Also, do you prefer analog or digital? Analog seems like it would actually be easier to read during a live performance ... what do you think?

Thanks. John

#### avkid

##### Not a New User
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Also, do you prefer analog or digital?
Digital, I can get actual numbers not estimations.

#### howlingwolf487

##### Active Member
Has anyone picked up one of the yellow and black ones on eBay? They're a brand called "wow2buy" and the look like clones of the Radio Shack model. but under $30 including shipping (vs.$40-45 + tax for RS).

You're going to have to spend some money if you want event a somewhat accurate measurement...just go to Radioshack and plop down the cash. If you save $20 but get results that are highly skewed, then that other money was a complete and total waste. You've now got a$30 paperweight - congratulations!

Also, do you prefer analog or digital?

I have an analog SPL meter only because I've heard they take peak measurements better than digital meters. If the Radioshack meter has a peak-hold function then heck...I'll go out and buy one tomorrow!

#### museav

##### CBMod
CB Mods
Departed Member
If the goal is simply to confirm a number, then the digital meters are probably easier to use since they give you a direct numerical reading. For some applications I actually prefer analog metering as I find them easier to judge dynamics and how the peak levels compare to average levels, etc.

Which segues into the peak issues. This is not an analog versus digital issue, the detector and meter dynamics/ballistics have a lot more to do with it. For example, the fast or slow selection on a meter, which even the Radio Shack meters have, will have a lot more effect on whether what you're seeing is, in very general terms, peak or average. Professional SLMs sometimes have an additional peak or impulse response setting that is an even faster response. The same idea applies to meters on equipment, there can be a big difference between whether it is a VU or PPM meter, the former is more an RMS reading representing volume while the latter is peak levels, but you cna find both in digital and analog forms. Supposedly, the Radio Shack digital meter will provide a min, max and integrated average reading for a user selectable 1 second to 199 second period.

Those black and yellow meters look like the old Radio Shack analog meters, not the one they currently offer. At about $27-$28 with shipping and with at best a 30 day warranty with you paying shipping to and from Hong Kong (two of the offerors show no warranty and only 3 or 7 day after delivery "DOA" replacement), you might want to buy more than one. At that point you've spent more than for a new RS analog or digital meter with a 90 day warranty that you can return to the store if it's DOA.

#### jkowtko

##### Well-Known Member
Ok, I can skip on the black and yellow knockoffs then ...

What about the Galaxy checkmate meters? Are they any better than the Radio Shack ones? I saw the performance test of the RS against another one, and it looked like the RS was measured to be as much as 5db off. Or is that level of accuracy to be expected for any of these relatively inexpensive meters?

Thanks. John

#### museav

##### CBMod
CB Mods
Departed Member
What about the Galaxy checkmate meters? Are they any better than the Radio Shack ones?
The CheckMate meters come in several versions. The CM-130 is pretty much the RS equivalent since it has no type rating, although it's MAX function has no time limit. Personal opinion here, but the fact that the CM-130 comes with a windscreen, has a calibrator available for it and that the shape forces the mic further away from your body which helps with minimize the effect of the person taking the measurements on the results are all potential advantages over the Radio Shack meter, although the RS meter being more compact is something others may appreciate. The CM-130 is recommended for a limited frequency response of 125Hz to 8kHz, but that is not probably much of a concern if making A-weighted readings of typical sources and although it is not specified, I'd guess the Radio Shack meter has similar limitations.

The CM-140 is similar to the CM-130 but is one of the lower cost rated Type meters, in this case Type 2, and the frequency response increases to 31.5Hz to 8kHz. The CM-150 is a pretty big step up with autoranging, data recording and a RS-232 interface and software so that the data can be saved and displayed on a computer.

I saw the performance test of the RS against another one, and it looked like the RS was measured to be as much as 5db off. Or is that level of accuracy to be expected for any of these relatively inexpensive meters?
Most comparisons I've heard related were much closer than that, but it isn't out of the question. Both the Radio Shack meters and the CheckMate CM-130 are specified as +/-2dB accuracy, so if one meter was quite a bit older or even if one was sitting there a while and the other just came from being out in the sun or in a cold car, then a 5dB difference wouldn't be that surprising. To give Radio Shack credit, the User Manual clearly states
Note: This meter should be used for home/hobbyist use only. This meter does not meet the requirements set forth by the American National Standards Institute (ANSI), Standard S1.4.
Of course, this statement being in the manual is one reason why it would be difficult to use the related readings for any legal purposes. Even Type 2 meters could disagree by several dB, that's why calibration is critical if you are making absolute level measurements.