# Voltcraft SPL-meter



## daxie

Hello,

Currently I own this meter:

Voltcraft SL-100










Does anybody know which correction values I can/should use?

It has no line out, so it only offers manual measurement, but I can't find the radioshack models here in Belgium/Europe.

Thank you!


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## Sonnie

I doubt you'll find correction values for it.

Try http://www.svsound.be/AVIA_SPL.aspx which is SVS in Belgium.


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## Fincave

I live in Finland and ordered my Radioshack meter from Dick Smiths Electronics who are in Australia. The price including shipping was about 40 euros and delivery took about ten days.


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## daxie

thx for the reply, seems I found one after all...

Will see when it gets here if it's the correct one...


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## Ilkka

daxie said:


> Hello,
> 
> Currently I own this meter:
> 
> Voltcraft SL-100
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Does anybody know which correction values I can/should use?
> 
> It has no line out, so it only offers manual measurement, but I can't find the radioshack models here in Belgium/Europe.
> 
> Thank you!


Don't bother buying the RS meter, the Voltcraft SL-100 is much better and more accurate. Here's the manual for it. You can use the general C-weighting corrections with it. 

edit: It has no line out, so you can't use with REW. But as an SPL meter it works great.


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## brucek

Looks like a nice meter.

I like that it measures down to 30dBSPL, but wonder if you can take frequency readings below its specified 31.5 Hz bottom end? and how close it tracks C-weight at frequencies down to 15Hz?

No line-out makes it a bit of a show stopper for REW.

Perhaps consider the Behringer ECM8000 and preamp combined with the Voltcraft.

brucek


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## Ilkka

brucek said:


> Looks like a nice meter.
> 
> I like that it measures down to 30dBSPL, but wonder if you can take frequency readings below its specified 31.5 Hz bottom end? and how close it tracks C-weight at frequencies down to 15Hz?
> 
> No line-out makes it a bit of a show stopper for REW.
> 
> Perhaps consider the Behringer ECM8000 and preamp combined with the Voltcraft.
> 
> brucek


Yes, it tracks well below 31.5 Hz. Much better than the RS meter. I have the more expensive Voltcraft meter and I measured it to be less than 1 dB off at 10 Hz (compared to my calibrated mic). Naturally it can not be used with REW because it's missing a line out connection (sorry for missing this earlier).


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## Sonnie

Ilkka said:


> Naturally it can not be used with REW because it's missing a line out connection (sorry for missing this earlier).


What a bummer. It sounds like it would be a great meter for us if it had the line out. I wonder if we might could get them to put a line-out on them and are they offered in the States?


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## Ilkka

Sonnie said:


> What a bummer. It sounds like it would be a great meter for us if it had the line out. I wonder if we might could get them to put a line-out on them and are they offered in the States?


It's sold as Galaxy in the States. They don't have the same SL-100 model, but CM-130, CM-140 and CM-150 instead. It looks like the CM-140 would be the best choice. It's sold for $99.99 (for example amazon.com) and has an aux output (AC). I'd recommed this over the RS meter without a doubt. I self have the CM-150 model and it's great.


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## Sonnie

Well whaddayaknow... we got the CM-140 in the Electronics Store.

AC output? What is that? Will an RCA connect to it?


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## Ilkka

Sonnie said:


> Well whaddayaknow... we got the CM-140 in the Electronics Store.
> 
> AC output? What is that? Will an RCA connect to it?


http://www.galaxyaudio.com/products/Pdf/CM140OperationManual.pdf

Nope, I mean AC as alternating current. The output is a regural 3.5 mm jack.


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## Sonnie

> AC signal output is available from standard 3.5mm
> coaxial socket suitable for a frequency analyzer, level
> recorder, FFT analyzer, graphic recorder, etc.


So maybe it would work with REW?


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## Ilkka

Sonnie said:


> So maybe it would work with REW?


Yes, it will work with REW (and TrueRTA etc.)


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## Sonnie

Well if it is fairly accurate down to 10Hz (on a consistent basis), it makes sense that it would be better to purchase it than the RS Meter/ECM8000/Mic Amp combo... and a lot less aggravating to setup. What am I missing?

Maybe I should order one and test it against my ECM8000 then compare to what you have tested. We might be on to something here. Why the :devil: haven't you spoke up about this meter before now? :boxer:


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## daxie

I only recently learned out about this forum...

BTW, I bought a RS in the between time cause I thought the sl-100 was a dud 

Guess not 

So I should be able to use it, albeit not with REW... (maybe using manual measurements and importing them, I'll see to it)

Since I have both, I will do a comparison between the corrected RS, and the SL-100.
That way, we can at least know a tad bit on how it performs...

Will be in a few days, when I'm on holiday, currently don't have the time 

Greetings,

daxie

(btw, still have to buy my behringer and sub though )


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## Sonnie

Thanks daxie.... that will be interesting to see them compared.


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## Ilkka

I did some quick comparison between my calibrated mic and the Voltcraft 322 SPL meter (which is the same as the Galaxy CM-150). When the C weighting was noted, the FR of the SPL meter was identical down to ~18 Hz. It has ~2.5 dB extra gain around 10 Hz, but then below 7 Hz is rolls off more quickly, ending up being around 4 dB down at 5 Hz. My calibrated mic is calibrated "only" down to 10 Hz, but it should be pretty accurate also below it.

If the CM-140 is a similar performer, I would definitely recommend it over the RS meter or even the ECM8000.


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## Sonnie

Sweet... I'd like to see a chart on a 140 too. Everyone looking for a mic down to 5Hz without having to send it off and get it calibrated.... and only 100 bucks. This is much cheaper and more accurate than the ECM route.


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## Ilkka

Sonnie said:


> Sweet... I'd like to see a chart on a 140 too. Everyone looking for a mic down to 5Hz without having to send it off and get it calibrated.... and only 100 bucks. This is much cheaper and more accurate than the ECM route.


I'm assuming the accuracy is identical with the CM-150 since they both are "IEC 651 Type II, ANSI S1.4 Type II" rated.

And you don't even have to buy a separate mixer/phantom power like with the ECM8000, one can plug this straight into his sound card. And one can calibrate his absolute SPL accurately. :clap:


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## Sonnie

I think I'll pick one up and piddle with it some. I think this is going to be a great find.


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## Wayne A. Pflughaupt

> If the CM-140 is a similar performer, I would definitely recommend it over the RS meter or even the ECM8000.


Any idea how good it is on the top end? I hear the RS meter starts to punk out at about 5 kHz.

Regards,
Wayne


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## Ilkka

Wayne A. Pflughaupt said:


> Any idea how good it is on the top end? I hear the RS meter starts to punk out at about 5 kHz.
> 
> Regards,
> Wayne


I'll take some measurements with my CM-150.


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## Wayne A. Pflughaupt

Guess you’ve been too involved with Ed and bosso on that JL Audio Fathom thread to get to it? :T 

Regards,
Wayne


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## Ilkka

Wayne A. Pflughaupt said:


> Guess you’ve been too involved with Ed and bosso on that JL Audio Fathom thread to get to it? :T
> 
> Regards,
> Wayne


Well yeah, and the fastly closing Christmas doesn't help either. I'll try it tomorrow.


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## Wayne A. Pflughaupt

Just hoped you hadn't forgotten. No rush - we're not going anywhere!  

Regards,
Wayne


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## Ilkka

Sorry that it took so long, but here are the measurements. It looks pretty good.


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## Ilkka

Sonnie said:


> I think I'll pick one up and piddle with it some. I think this is going to be a great find.


Did you get yours already?


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## Sonnie

lol... no... I forgot to order it. I actually thought I had ordered it, but obviously forgot. I will do this now. Thanks for reminding me.

EDIT: It is ordered.


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## Deane Johnson

It appears to my untrained eye/brain that the chart only measures down to 200 Hz. Isn't it below that where most meters get in trouble, and where we have the greatest interest in accuracy.


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## Ilkka

Deane Johnson said:


> It appears to my untrained eye/brain that the chart only measures down to 200 Hz. Isn't it below that where most meters get in trouble, and where we have the greatest interest in accuracy.


Yes, that chart goes only down to 200 Hz, but not because the SPL meter wouldn't be accurate there.

This is the chart I showed earlier. You can see that the SPL meter is dead accurate down to ~18 Hz, and only slightly off below that.


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## Deane Johnson

Take me one more step. Does that mean it doesn't need a correction factor such as the RS meter does?


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## Ilkka

Deane Johnson said:


> Take me one more step. Does that mean it doesn't need a correction factor such as the RS meter does?


It needs a general C weighting correction. REW has that built-in.


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## Deane Johnson

I don't use REW, but rather the Excel spread sheet from this forum that provides the RS correction and draws the graph. I guess my question is, with this meter, does one need any special correction like the RS does, or simply the "C" weighting provided by the meter switched to that position. In other words, is what the meter reads correct, unlike the RS meter.


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## Ilkka

Deane Johnson said:


> I don't use REW, but rather the Excel spread sheet from this forum that provides the RS correction and draws the graph. I guess my question is, with this meter, does one need any special correction like the RS does, or simply the "C" weighting provided by the meter switched to that position. In other words, is what the meter reads correct, unlike the RS meter.


I'll try to explain it.

RS meter= C weighting + additional error (varies from meter to meter)
Voltcraft/Galaxy = C weighting

So yes, you will need to add the C weighting corrections for this meter too, but the difference is that when yo do that, it's dead accurate, unlike the RS.


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## Deane Johnson

Aren't the "C" weighted corrections added automatically in the meter when the A/C switch is in the C position?


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## Ilkka

Deane Johnson said:


> Aren't the "C" weighted corrections added automatically in the meter when the A/C switch is in the C position?


No, the output is then C weighted (or A). If you want to make it flat, you'll have to apply a reversed C weighting i.e. C weighting corrections.


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## Deane Johnson

Ilkka said:


> No, the output is then C weighted (or A). If you want to make it flat, you'll have to apply a reversed C weighting i.e. C weighting corrections.


OK, fair enough. And I guess we do that automatically with the Excel spread sheet, or are my graphs all wrong.


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## Ilkka

Deane Johnson said:


> OK, fair enough. And I guess we do that automatically with the Excel spread sheet, or are my graphs all wrong.


Yes, the Excel sheet applies a C weighting + additional error corrections for the RS meter. You can't use the same sheet (unless you modify it) with more accurate SPL meters.


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## Deane Johnson

Ilkka said:


> Yes, the Excel sheet applies a C weighting + additional error corrections for the RS meter. You can't use the same sheet (unless you modify it) with more accurate SPL meters.


OK, finally getting it. One of these days I'll muster enough fortitude to get involved with REW. Thanks for your answers.


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## Wayne A. Pflughaupt

Can (or should) John do a calibration file to address the deviations above 2 kHz? And if so, could this meter replace the calibrated Behringer ECM8000 for full-range?

Regards,
Wayne


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## Ilkka

Wayne A. Pflughaupt said:


> Can (or should) John do a calibration file to address the deviations above 2 kHz?


I don't think it's wise to start correcting 1-2 dB errors at very high frequencies. It's enough accurate for full range frequency measurements. Although I wouldn't start designing speakers with it.



> And if so, could this meter replace the calibrated Behringer ECM8000 for full-range?


I haven't measured the ECM8k, so I don't know accurate it is.


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## Sonnie

Wayne, remember that Ilkka is testing the equivalent to the Galaxy CM-150, which costs about $225. If the CM-140 tests out the same, it's only $99 via the Shack Electronics Store. It would be a more viable replacement for the ECM8000.


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## Ilkka

Sonnie said:


> Wayne, remember that Ilkka is testing the equivalent to the Galaxy CM-150, which costs about $225. If the CM-140 tests out the same, it's only $99 via the Shack Electronics Store. It would be a more viable replacement for the ECM8000.


Yes that's true, although I believe CM-150 and CM-140 will measure up identically. CM-150 has only more options/settings.


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## Sonnie

I thought I'd get to measure this CM-140 today. Got everything setup but don't have the right mini plug. I have a stereo to RCA plug, but it needs a mini mono to single RCA.


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## Ilkka

Sonnie said:


> I thought I'd get to measure this CM-140 today. Got everything setup but don't have the right mini plug. I have a stereo to RCA plug, but it needs a mini mono to single RCA.


Stereo plug works at least with my meter. Just use the left channel.


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## Sonnie

Why didn't I know that? I was using the right channel... left channel worked perfectly and as you suggested and expected, the CM-140 needs no correction values.


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## Sonnie

Of course my ECM8000 is only calibrated to 10Hz and this is an unfiltered measurement... I could probably get more precise, but I think this is good enough to tell us what we wanna know and that is that the CM-140 is really the way to go as far as meters are concerned at only 100 bucks... no correction values needed.


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## JohnM

Which trace is which, Sonnie? Do you have inverse C applied for the CM-140? How does the low end look if you match the levels of the traces at the upper end of your range using the trace offsets?


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## Wayne A. Pflughaupt

Looks to me like it needs some kind of correction, because it’s far from flat.

And I’m still wondering if it can replace the Behringer mic for the upper end.

Regards,
Wayne


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## Sonnie

JohnM said:


> Which trace is which, Sonnie? Do you have inverse C applied for the CM-140? How does the low end look if you match the levels of the traces at the upper end of your range using the trace offsets?


I'm not sure which is which, but I've still got everything setup in the HT room, other than my laptop is not in there. I can probably check it all again tomorrow night.



Wayne A. Pflughaupt said:


> Looks to me like it needs some kind of correction, because it’s far from flat.
> 
> And I’m still wondering if it can replace the Behringer mic for the upper end.


The response is far from flat because it's my sub response. However, the ECM is corrected and the CM is not... so that means it won't need any corrections. I'm not sure on the upper end, but I'll see what it looks like up there. 

I may be able to do it later tonight when we get back home... I'll see how I feel then.


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## brucek

> However, the ECM is corrected and the CM is not


But does the CM have a C-weight switch that you select (like the RS meter) and then compensate for in REW by checking the C-weight box, or is the C-weight box unchecked and the CM simply reads flat?

brucek


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## Sonnie

I'll check it tomorrow night... check that... later tonight.

It does have a A/C weighting toggle, but I'm not sure if the output is weighted. I wanna say I had the C weighting block unchecked, because I unchecked it for the ECM and I don't think I ever checked it back for the CM-140.

Either way, we know it will match up down low.


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## Ilkka

Sonnie said:


> I'll check it tomorrow night... check that... later tonight.
> 
> It does have a A/C weighting toggle, but I'm not sure if the output is weighted. I wanna say I had the C weighting block unchecked, because I unchecked it for the ECM and I don't think I ever checked it back for the CM-140.
> 
> Either way, we know it will match up down low.


At least my meter's output is C weighted (or A if you like), so you must have the inversed C weighting checked.


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## Ilkka

Wayne A. Pflughaupt said:


> And I’m still wondering if it can replace the Behringer mic for the upper end.
> 
> Regards,
> Wayne


I'm not sure what you're after, but if you need to take accurate measurements up to 20 kHz, neither of these is a perfect choise. Both are reasonably close, but I wouldn't start to desing a speaker with them... For normal in-room frequency response measurements - good enough.


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## Peter De Smidt

Ilkka said:


> I'm not sure what you're after, but if you need to take accurate measurements up to 20 kHz, neither of these is a perfect choise. Both are reasonably close, but I wouldn't start to desing a speaker with them... For normal in-room frequency response measurements - good enough.


Just out of curiosity, what mic would you recommend for speaker design?


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## Wayne A. Pflughaupt

> I'm not sure what you're after, but if you need to take accurate measurements up to 20 kHz, neither of these is a perfect choise. Both are reasonably close, but I wouldn't start to desing a speaker with them... For normal in-room frequency response measurements - good enough.


Since it’s comparable to the Behringer, I’m thinking it would be nice to have the accuracy of the calibrated Behringer without the hassle of the mini-mixer/pre-amp. I wonder if Sonnie’s calibration guy could calibrate them?

Regards,
Wayne A. Pflughaupt[/size][/font]


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## Sonnie

No... he will not calibrate SPL meters. It's hard to find anyone to calibrate those.

I didn't get around to doing anything else tonight, but I'm off tomorrow and will do some more testing.

I contacted Galaxy today and I'm getting setup with them so that we can offer their SPL meters here at the Shack... direct. Maybe with a little discount off the normal prices you see floating around.

Galaxy also has a CM-130 which is generally only 50 bucks at most online stores. It's rated the same at the 140 and 150 with less features, but enough to get us buy. I've got one of those on the way and we'll measure it as well. It would great if it is spot on down to 10Hz. I think we are on to something positive here.


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## Malice

Sonnie said:


> Well if it is fairly accurate down to 10Hz (on a consistent basis), it makes sense that it would be better to purchase it than the RS Meter/ECM8000/Mic Amp combo... and a lot less aggravating to setup. What am I missing?


The fact that the BFD lowest filter setting is 20Hz. Why measure something you cannot control? :dunno:


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## Ilkka

Sonnie said:


> Galaxy also has a CM-130 which is generally only 50 bucks at most online stores. It's rated the same at the 140 and 150 with less features, but enough to get us buy. I've got one of those on the way and we'll measure it as well. It would great if it is spot on down to 10Hz. I think we are on to something positive here.


The CM-130 doesn't have a line out! And it's rated only down to 125 Hz...

http://www.galaxyaudio.com/products/Pdf/CM130OperationManual.pdf


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## Wayne A. Pflughaupt

Malice said:


> The fact that the BFD lowest filter setting is 20Hz. Why measure something you cannot control? :dunno:


Because irrespective of the fact that you can’t set a filter that low, it’s nice to be able to see what your sub is doing down there. Not to mention, a filter set at 20 Hz will have an effect on frequencies lower than that. 

Regards,
Wayne


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## Malice

With room gain playing a big part with lower frequencies, and my room adding about 10db at 25 Hz, I cannot imagine creating a filter at 20Hz to try and knock out an anomaly at 16Hz. I think too much would be lost either side of 20Hz filter. 

And besides, ignorance is bliss!!


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## Sonnie

Ilkka said:


> The CM-130 doesn't have a line out! And it's rated only down to 125 Hz...
> 
> http://www.galaxyaudio.com/products/Pdf/CM130OperationManual.pdf


Hmmm... guess I was looking at some bad info then... 



> The Galaxy Audio CM-130 CHECK MATE is a lightweight, 9V battery-operated SPL meter with a built-in electret condenser microphone and a large, backlit display featuring low, medium and high level range readouts. This high-tech but inexpensive meter offers selectable fast and slow response times, AC signal output, and large. easily accessible selector buttons.
> 
> 
> Key Features:
> 
> •	Lightweight, miniature SPL meter with 0.1 dB resolution
> •	Built-in electret condenser microphone with windscreen
> •	Large backlit level range display with low, medium and high level readouts
> •	Standard 9V battery operation with 50 hr. battery life
> •	AC signal output





> Specifications:
> 
> Frequency Response -	31.5 Hz - 8 kHz
> Accuracy -	+/-1.5 dB (ref 94dB @1KHz)
> Standard -	Not Specified by Manufacturer
> Weighting -	Time: Fast, Slow; Frequency: A, C
> Response -
> Lo: 35 - 80dB
> Med: 50 -100 dB
> Hi: 80 - 130 dB
> Signal Output -	AC
> Battery Check -	Yes
> Battery Life -	50 hrs.
> Dimensions - 9.1 x 2.1 x 1.3" (232 x 54 x 34mm)
> Weight - 7.05 oz (200 g)


It appears the site I was looking at may have had their info crossed up with the CM-140.

Yeah... the 130 does us no good. Looks like the 140 will be the best ticket.


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## brucek

> Why measure something you cannot control?


Lots of control can be realized with sub positioning.........


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## Malice

brucek said:


> Lots of control can be realized with sub positioning.........


me :duh: 
you :hail:


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## Sonnie

Here are some more amateur results:










And for Wayne:










I'd probably stick with the ECM or better for upper range measuring, but the CM-140 will be fine for what we do with the BFD.


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## brucek

Does the CM-140 have a selectable switch for:

(a) flat
(b) C-weight
(c) A-weight

?

brucek


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## Sonnie

Nope... just A or C toggle.


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## brucek

> Nope... just A or C toggle


So why are you not selecting C-Weight in REW? I see you also unchecked it. Why is that?


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## Sonnie

It matches the response of the ECM-8000 better when unchecked... isn't that what we are after... :huh:

Or should we really be adding C-Weighting to the ECM to get a more accurate measurement?


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## brucek

But wouldn't it be better to create a calibration file and make it a perfect match?


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## Ilkka

Sonnie said:


> Here are some more amateur results:


You have to match the lines in 100-200 Hz range. It seems that the CM-140 reads a little bit high at the low frequencies, especially below 20 Hz. But definitely better than the RS meter.



> And for Wayne:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> I'd probably stick with the ECM or better for upper range measuring, but the CM-140 will be fine for what we do with the BFD.


Upper range measurements are extremely hard to take. I use shorter measuring distance and make sure both mics (the mic capsule part) are identically located. So I'm not taping them together, because then the mics are not located identically.


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## Ilkka

Sonnie said:


> It matches the response of the ECM-8000 better when unchecked... isn't that what we are after... :huh:


Of course you must check the C weighting in REW. And please, match those measurements in 100-200 Hz range (use REW's offset function). Then you can see the real differences.



> Or should we really be adding C-Weighting to the ECM to get a more accurate measurement?


ECM8000 doesn't have a C weighting, it has a flat response.


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## brucek

> Or should we really be adding C-Weighting to the ECM to get a more accurate measurement?





> ECM8000 doesn't have a C weighting, it has a flat response


I believe Sonnie was talking about checking C-weight in REW.
But as you know, it makes no difference to check C-weight in REW in a frequency range that is covered by a calibration file. The calibration file over-rides the C-weight file up to its frequency limits.

brucek


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## Sonnie

brucek said:


> But wouldn't it be better to create a calibration file and make it a perfect match?


We could, but I think we'd could possibly see a db or two variance between meters and measuring conditions. I'd like to see some other CM-140 comparison with other calibrated mics... similar to Ilkka's comparison of the CM-150



Ilkka said:


> Upper range measurements are extremely hard to take. I use shorter measuring distance and make sure both mics (the mic capsule part) are identically located. So I'm not taping them together, because then the mics are not located identically.


Exactly... that's why I said amateur results. I didn't tape them either, but rather swapped them out and try to keep them in the same location, but again, my setup is not really ideal, especially for the higher range of frequencies.


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## Ilkka

Peter De Smidt said:


> Just out of curiosity, what mic would you recommend for speaker design?


http://www.earthworksaudio.com/
http://www.acopacific.com/
http://www.linearx.com/products/ProductsTop.htm


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## Ilkka

brucek said:


> I believe Sonnie was talking about checking C-weight in REW.
> 
> brucek


Yes, I got that.  But you shouldn't do that, since ECM8000 has nothing to do with C weighting.


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## Sonnie

Okay... here's what I think you want. C-Weighting is checked in REW. 

Red=ECM8000
Green=CM-140


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## Sonnie

Hey... look at my subs go ... 2Hz :yikes: ... :sarcastic:


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## brucek

> Okay... here's what I think you want. C-Weighting is checked in REW.


Exactly.. 

But we need to create a cal file from about 30Hz and down just as we did for the RS meters, except they were ****** below 100Hz. Looks like 30Hz and down will be fine for these CM140's,


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## Ilkka

Sonnie said:


> Okay... here's what I think you want. C-Weighting is checked in REW.
> 
> Red=ECM8000
> Green=CM-140


Yes, that's what I wanted.  Now you see that it reads around 1.5 dB high at 20 Hz, and more below. So it seems to need a correction file after all. Of course to be sure we would need to measure a couple more...

My CM-150 was accurate down to ~18 Hz, and only ~2.5 dB high at 10 Hz.


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## Sonnie

Yeah... let me make sure I'm gonna be able to get a dealer line setup, which I don't see a problem according to Galaxy and their rep... and I'll order up a few of them and double check them all. Then we can be more certain of the cal file. 

Kinda surprising that it is actually reading too high though... all the RS Meters read too low down low.


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## brucek

> Then we can be more certain of the cal file.


Maybe we'll do this one from 5Hz to satisfy all the IB wackos audiophiles. 

brucek

.....oops, just remembered. The ECM cal file only goes down to 10Hz.....oh well, it'll have to do.


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## Guest

Sonnie said:


> Kinda surprising that it is actually reading too high though... all the RS Meters read too low down low.


This raises a point I've been curious about regarding the newer correction files provided on this site for both style of newer RS meter. 

Since REW ignores C-weight correction in the range covered by a meter correction file, it seems logical that the values listed in the file must also account for the C-weight correction. 

So if you're calibrating against an un-weighted mic and end up lets say -2db at 32hz, then in the correction file you would add -2db to the C-weight -3db at that frequency for a total of -5db. 

Using the meter correction files as they are right now yields about half of what a C-weight correction alone offers. Meaning...a response graph plotted with no meter correction file, but C-weight correction checked in REW shows better low-end gain comparred with a graph plotted using the current correction file for that style RS meter. 

Which brings us back to the quote above if you follow me.


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## Ilkka

dcanet said:


> This raises a point I've been curious about regarding the newer correction files provided on this site for both style of newer RS meter.
> 
> Since REW ignores C-weight correction in the range covered by a meter correction file, it seems logical that the values listed in the file must also account for the C-weight correction.
> 
> So if you're calibrating against an un-weighted mic and end up lets say -2db at 32hz, then in the correction file you would add -2db to the C-weight -3db at that frequency for a total of -5db.
> 
> Using the meter correction files as they are right now yields about half of what a C-weight correction alone offers. Meaning...a response graph plotted with no meter correction file, but C-weight correction checked in REW shows better low-end gain comparred with a graph plotted using the current correction file for that style RS meter.
> 
> Which brings us back to the quote above if you follow me.


That's correct. I was pretty surprised to find out that Sonnie's corrections for both new analog and digital meters are actually smaller than the C weighting correction. Their frequency response without the correction file but with the C weighting compensation on in REW would be actually pretty close to CM-140's response.


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## brucek

> Since REW ignores C-weight correction in the range covered by a meter correction file, it seems logical that the values listed in the file must also account for the C-weight correction.


Yep, that correct.
The calibration files for the three RS meters were simply created by measurment differences against the ECM8000 with its calibration file loaded. So sure, the final files are indeed a combination of the standard C-weight spec and the deviation from it. REW conveniently carries on with a standard C-weight from any end point that the calibration file stops. 

After the files were created, when any of the meters that Sonnie tested was compared against the ECM with their new cal files loaded they tracked almost exact.

brucek


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## Sonnie

> I was pretty surprised to find out that Sonnie's corrections for both new analog and digital meters are actually smaller than the C weighting correction. Their frequency response without the correction file but with the C weighting compensation on in REW would be actually pretty close to CM-140's response.


Yeah... and we'd be fine if hadn't found a friend... :bigsmile:


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## Guest

> Sonnie wrote:
> Kinda surprising that it is actually reading too high though... all the RS Meters read too low down low.


Perhaps Sonnie can clarify further what he meant, as this statement seems to contradict what the correction files are showing...in that they have attenuated the C-weight corrected meter readings down low. Which suggest the RS meters (with C-weight correction only) actually read *too high * compared against his calibrated mic. 

BTW: I do appreciate the time and dedication you guys have put into this excellent site.


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## Sonnie

When the RS corrections are applied in the lower frequencies they increase the response. With no corrections (no calibration file) the response would read too low, lower than it actually is.

Here is an example of what one of the RS calibration files would do to your response if your response read flat 75db with the RS meter:


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## brucek

RS meters were all supposed to track a C-weight standard in their response. If they indeed followed that spec, then a simple click of the C-Weight switch in REW would inversely compensate for their response and you would end up with the readings representing a flat response. That's in a perfect world. 

There are also microphones (ECM8000) that are supposed to track a flat response, and as such we should simply deselect the C-weight switch in REW and you would end up with readings representing a flat response. It isn't perfect in reality and so we have a cal file supplying a small amount of compensation.

What we found was that the newer RS meters had more of a flat output than a C-weight output that the old analog meter possessed.

It was decided that since none of them tracked either flat nor C-weight, it would be best to simply create separate files for them all against a calibrated mic. Seemed reasonable to me. :huh: 

I suspect sonnie simply forgot that the CM140 had the C-weight box checked indicating that it simply reads a bit higher than C-weight.... whatever..... it needs a cal file to make it track the ECM8000.

Below is a picture of the calibration files of the three RS meters and the ECM800 and the C-weight standard.

------------------------










-----------------------

brucek


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## Guest

brucek said:


> I suspect sonnie simply forgot that the CM140 had the C-weight box checked indicating that it simply reads a bit higher than C-weight.... whatever..... it needs a cal file to make it track the ECM8000.
> brucek


Thanks, *that *answers my original question. The newer RS meters (just like the CM140) read a bit high with only C-weight correction applied. Whew! 

Sorry you felt a primer covering the basics of calibration files and why we use them was required. 

When I first started tuning my sub with REW/BFD last spring, I was using the original cal file for the old analog RS meter. I was living large (or so I thought) with decent extension 
below 20hz. Then Sonnie posted the new cal files. Poof! My sub/room response now drops dramatically below 22hz. The truth hurts! Even if I probably can't hear it anyway....

Fortunately I enjoy the process of exhausting every possible placement for both sub and primary listening position. Can't say my wife shares in my enthusiasm.

So it seems what I'm now seeing is (or reasonably close to) the true response. Rock on!!


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## Chrisbee

dcanet said:


> When I first started tuning my sub with REW/BFD last spring, I was using the original cal file for the old analog RS meter. I was living large (or so I thought) with decent extension
> below 20hz. Then Sonnie posted the new cal files. Poof! My sub/room response now drops dramatically below 22hz. The truth hurts! Even if I probably can't hear it anyway....
> 
> So it seems what I'm now seeing is (or reasonably close to) the true response. Rock on!!


I went through this agony thinking I'd lost all my IB's low bass. :hissyfit: 

Now I have discovered my new meter should really use the old analogue file I have all my bass back again. :jump:

I wish Sonnnie wouldn't keep showing near DC responses in REW! :sneeky: 

He doesn't even have real subwoofers show off with! :rofl:


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## brucek

> I wish Sonnnie wouldn't keep showing near DC responses in REW!


Since the lowest level we have a calibration file for is 10Hz, that should be the lowest limit I suppose.
For using REW to check equipment responses, it is fine to go to 2Hz...



> I went through this agony thinking I'd lost all my IB's low bass


But you must have noticed that the actual bass never changed when you swapped meters. I guess you questioned the original meter at that point? Even if you suspected your bass was gone due to a meter change, weren't the rattling walls and pictures a clue?  

brucek


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## Chrisbee

brucek said:


> Since the lowest level we have a calibration file for is 10Hz, that should be the lowest limit I suppose.
> For using REW to check equipment responses, it is fine to go to 2Hz...


I see. You had better stand over Sonnie until he makes some meter cal files down to DC then. 



> But you must have noticed that the actual bass never changed when you swapped meters. I guess you questioned the original meter at that point? Even if you suspected your bass was gone due to a meter change, weren't the rattling walls and pictures a clue?
> 
> brucek


I was comparing my IB with my 16-46 which regularly shakes the floor more than the IB. :huh: My old meter always seemed to exaggerate the low bass. I was always getting fantastically deep responses from my DIY subs (and the SVS) and it just didn't seem likely. So when Sonnie published the new analogue cal file I finally had a get out clause for all my subs. Now I know I really need the old cal file I have all my amazing performances back again. (in duplicate)


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## Sonnie

Chrisbee said:


> I see. You had better stand over Sonnie until he makes some meter cal files down to DC then.


I don't have anything to calibrate below 10Hz with... :huh: Maybe someone who has a professional mic that is flat to DC will volunteer to calibrate one of the CM-140's for us... or I can send them my ECM8000.


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## Chrisbee

What happens if the present cal. curves are extended further westwards following the trend above 10Hz?

Something like this?


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## brucek

> What happens if the present cal. curves are extended further westwards following the trend above 10Hz?


The response below 10Hz would be compensated by your guess. 

Are you sure it doesn't drop immediately off? Are you sure it doesn't go flat? Are you sure it doesn't rise?

brucek


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## Chrisbee

brucek said:


> The response below 10Hz would be compensated by your guess.
> 
> Are you sure it doesn't drop immediately off? Are you sure it doesn't go flat? Are you sure it doesn't rise?
> 
> brucek


I agree we are in completely unknown territory.

But, it would still be fun to try if REW's graph boundaries can be stretched. 

Few subs (one presumes) have any useful output down in these constantly dark depths. 

It will be fun to shine a light on the strange creatures inhabiting this level.:dumbcrazy: 

And no sarcastic remarks about IB owners, thankyou very much! :devil: 

IB = Infrasonic Bathysphere! :nerd: 

One day HT'ers will look back at or fumbling attempts to reach these crushing depths with breathless admiration. :clap: 

:R


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## will95

Has anyone looked at this SPL meter for $99? 

http://www.reliabilitydirect.com/soundlevelmeters/RDI-AR824.htm

Specs are similar to CM-140, but it has some nice extra features beyond what I have seen published for the CM-140 including:

- 4 overlapping sound ranges instead of 3
- Appears to have digital bar representation of an analog display above the digital read-out. This could be useful, and this appears to be the same feature as on the CMT-150.
- Same sample rate (0.5 sec) as CM-150 (haven't seen a sample rate for the CMT-140)
- Auto shutoff like CM-150
- Spec says it has AC and DC outputs
- Will run on either four AA or one 9 v batteries (comes with 4 AA batteries).
- 0.5" microphone (same size as CM-150, have not seen a mic size quoted for the CMT-140).

Also, I have no connection to the company offering the AR824 SPL meters. My interest is that I have just put in an order to Sonnie for the group purchase of the CM-140s. I just want to get the best meter for my money and this meter looks like it may be better if it tests out equivalent to or better than the CM-140 versus a calibrated mic. 

I also called the company about a quantity purchase discount and they quoted me 10% off, but futher negotiation may be possible.

I'd be willing to wait on the CM-140 group order for this unit to be tested/evaluated first.

--Mike


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## will95

The Reliability Direct AR864 SPL meter ($99) (http://www.reliabilitydirect.com/soundlevelmeters/RDI-AR824.htm), appears to be equivalent to this one <TES 1357 Sound Meter with Combination Digital and Analog Display> offered at http://www.dasdistribution.com/products/sound_level_meters/index.htm for $219. Das Distribution also offers a NIST calibrated SPL meter on sale for $119 <DT-805-NIST Professional Two Range SLM with Bright Backlit Display>.

Here is another SPL meter that I found that looks similar to AR824 and appears to be functionally equivalent the CM-150 at only $109 in quantity of 5+. http://www.multimeterwarehouse.com/JTS1357.htm#

It also appears to have a user selectable sample/screen refresh rate that exceeds the Galaxy CM-150 spec. Probably can get it for even less with the proposed HTS group purchase of 10+.


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## Ilkka

will95 said:


> The Reliability Direct AR864 SPL meter ($99) (http://www.reliabilitydirect.com/soundlevelmeters/RDI-AR824.htm), appears to be equivalent to this one <TES 1357 Sound Meter with Combination Digital and Analog Display> offered at http://www.dasdistribution.com/products/sound_level_meters/index.htm for $219. Das Distribution also offers a NIST calibrated SPL meter on sale for $119 <DT-805-NIST Professional Two Range SLM with Bright Backlit Display>.
> 
> Here is another SPL meter that I found that looks similar to AR824 and appears to be functionally equivalent the CM-150 at only $109 in quantity of 5+. http://www.multimeterwarehouse.com/JTS1357.htm#
> 
> It also appears to have a user selectable sample/screen refresh rate that exceeds the Galaxy CM-150 spec. Probably can get it for even less with the proposed HTS group purchase of 10+.


http://www.reliabilitydirect.com/soundlevelmeters/RDI-AR824.htm
http://www.multimeterwarehouse.com/JTS1357.htm#

Those two are pretty much identical and they also have pretty much identical specs with the Galaxy CM-150. Highly recommended! Has Sonnie noticed this?

DT-805-NIST Professional Two Range SLM with Bright Backlit Display:

That one doesn't have AC output so it's no good with REW.


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## Sonnie

Yes, I called Reliability Direct and spoke with Chris. He stated their AR824 rolls off below 30Hz. It would be in line with the CM-140, except have a couple extra features. Really they are features that we don't need or have to have. The least he will sell them is $90, if we buy in bulk, + shipping. There is no way I can get those in here and shipped back out for $95.... it would be more like $105-110. And no one has ever even heard of this meter. At least with the Voltcraft/Galaxy we have measured them and are better known.

Now, if someone wants to buy one and test it themselves, they could buy it direct for the $99 + shipping and let us know what it's like.


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## Ilkka

Sonnie said:


> Yes, I called Reliability Direct and spoke with Chris. He stated their AR824 rolls off below 30Hz. It would be in line with the CM-140, except have a couple extra features. Really they are features that we don't need or have to have. The least he will sell them is $90, if we buy in bulk, + shipping. There is no way I can get those in here and shipped back out for $95.... it would be more like $105-110. And no one has ever even heard of this meter. At least with the Voltcraft/Galaxy we have measured them and are better known.
> 
> Now, if someone wants to buy one and test it themselves, they could buy it direct for the $99 + shipping and let us know what it's like.


All C-weighted SPL meters roll off below 30 Hz. That's why REW has built-in C-weighting compensation.

I'm pretty sure that model would be as accurate but anyways.


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## Sonnie

Well... Chris said that the AR824 would not be as accurate as the more expensive SPL meters. Again, if someone wants to buy one and test it... go for it! It will be no skin off my back because I'm not making enough for all the time involved in what I'm doing anyway... not that I mind, but the point is someone buying from somewhere else is absolutely within their own choice and would not hurt my feelings one iota.



> I'm pretty sure that model would be as accurate but anyways.


As accurate as what? And how are you pretty sure? As far as we know, know one except the seller of the unit, Chris, has had any experience with the meter.


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## Guest

So ........ If I have a CM-140, I don't need the ECM8k I just bought ;(


So , my best bet would be to sell or return the ECM8k and get a SPL.

What about this meter Radio Shack is no longer in Canada , but we have The SourceCC which was Radio Shack. and what about this SPL 

http://www.thesourcecc.com/estore/S...ge=en-CA&keywords=sound+level+meter&pagenum=0


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## Sonnie

If you have a CM-140, you have an SPL meter and mic all in one... the ECM8K nor the RS SPL meter is needed. Save your money... :T


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## Guest

Thanks too late though I bought the ECM8K first 
thought that the SPL was just to set the db levels and the EM8K was to read the frequencies.

So, what I gather is that I can use the CM-140 and plug it into my laptop and REW will use it as a RTA mike


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## brucek

> So, what I gather is that I can use the CM-140 and plug it into my laptop


You do need an external soundcard to plug into first and then into the laptop....

brucek


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## Guest

external ?

internals are no good ?


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## brucek

> internals are no good ?


The problem being that there is usually no line-in capability on a laptop. Only a microphone in, and that's unsuitable. You need an external USB soundcard to use a laptop. They're cheap as dirt. 

brucek


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## Guest

My Laptop has a Mic in and a line in and a line out.


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## anidabi

Any news about AR824 sound level meters? Anyone ordered and tested already? Some user comments would be nice.


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