# SPL meter



## Steeve-O (Dec 3, 2010)

Hi,

I don't have anything to measure my speaker level. I don't have REW but I do plan do REW measurement in the next few years once I can setup a proper HT setup. I just aquired a house so it's going to happen. 

For now I would like to start with a SPL meter to set my speaker trim. It would have been usefull more than once and I realised that it's a pretty much must have tool to set your speaker trim. 

The issue is that I live in Canada so the Radioshack SPL meter is not available here. I don't want to spend more than 100$ if possible. It would be great to have a general calibration file for it (like the radio shack) just to start doing basic measurement. Also I know there is a lot of bad stuff in the SPL world so that is why I asked help. I saw one available at the source.ca but after seing a few review I found out that it's cheap and too expensive. 

There is also cheap stuff on Ebay but really their quality is questionnable. If one can tell me where these calibration file are available. I know you can get it calibrated but I don't want to get it calibrated this good as I won't use it for EQ. There is REW with cross spectrum mic for that.


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## tonyvdb (Sep 5, 2007)

If you want a dedicated hand held meter the Galaxy CM 140 is a really nice one.
Your other option is to use your smartphone as there are several decent apps that will get the job done. I use "audio tools" on my iPhone and it's very good.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Steeve-O said:


> The issue is that I live in Canada so the Radioshack SPL meter is not available here. I don't want to spend more than 100$ if possible. It would be great to have a general calibration file for it (like the radio shack) just to start doing basic measurement.


The calibration file thing for the Radio Shack meter came about from people trying to use it in a manner for what it was not designed, namely measuring sine wave signals. Sound level meters, especially cheap ones like those from Radio Shack, are simply designed for measuring noise levels, which are seldom frequency-specific like sine waves are. If you’re primarily interested in setting speaker levels, which is typically done with limited-band pink noise signals, no calibration file is needed for it or any other meter, cheap or expensive.

The Galaxy CM 140 meter Tony recommended is certified by the manufacturer as a Type II device, meaning it’s accurate +/- 1.5 dB. Meters more accurate than that (e.g. Type I) start to get really expensive, so the CM 140 is not a bad deal for $130. I would expect that it tracks the C-weighting curve pretty accurately, so if you wanted to measure sine waves for your subwoofers, you could easily calculate SPL by comparing your readings below ~60 Hz to a C-weighted response graph. For instance, most C-weighted graphs show response to be down ~5 dB at 25 Hz, so you’d add 5 dB to your reading for a 25 Hz sine wave to get a reasonably accurate figure.

Galaxy makes a more economical model, the CM 130, which doesn’t meet the lowest IEC or ANSI standards and therefore is only certified to be accurate +/- 2 dB. However, if you’re only interested in setting speaker levels it should be sufficient. I expect that the other cheap meters you’re talking about would also be no better than +/- 2 dB, but could easily be even worse.

Hope this helps.

Regards, 
Wayne


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## Steeve-O (Dec 3, 2010)

Alright. So It is better to invest in a less expensive SPL meter and use it only for matching speaker level. I will look into the Galaxy model. I will save some money by looking in the CM 130. 

I plan to buy the required hardware to do rew stuff but since I currently don't have my final room and I cannot plan much with speaker position, subwoofer, etc and have no space for room threatment. I figured that I prefer to beleive that my system sound good because I think it does. Because what has been seen can't be unseen right? So REW is at least a years away.


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## Felipe (May 9, 2011)

I have the CM-140. I use it to make REW measurements and I think it is enough for most purposes.
Buy it from Cross Spectrum with a calibration file, so you can start to do REW meas when you want and start to learn to use REW and interpret the graphs. Later you can use it in your new house with the background learned. Just check you have a line input in the computer (most mic in are dual mic/Line, but best check it).

Other way you can buy a CM-130 (it is fine for matching speaker level) and later buy a calibrated usb mic.

Both are good decisions.


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## Steeve-O (Dec 3, 2010)

I didn't knew Cross Spectrum sell SPL meter. I will look at them too.


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## nwf477 (Feb 8, 2015)

I am not going to imply the SPL meter is the way to go for accurate measuring but I seem to recall there was something I read that compared the SPL with 3 or 4 mics? and it was found during the test at lower freq.'s the SPL was within 1db. I also read something about were it was lacking, I am not trying to be vague just cannot remember where I saw it. Regardless of that I wish I had the mic set-up would be so much easier and you would not have use correction tables for the meter. At least for me close will work for now.


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## informel (Jun 21, 2011)

If you plan to use REW, you can also buy the UMIK-1 from cross-spectrum, it connect to your PC via USB so it is easy to install
http://www.minidsp.com/products/acoustic-measurement/umik-1


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## Steeve-O (Dec 3, 2010)

I guess that is the dilema... Having a portable SPL meter to setup my HT and my friend HT once in a while. Or grab the right mic and use REW and be done with it but I will most likely be stuck when I need somewhere else (don't have a laptop). I guess I will have to think about it. 

Is the REW SPL meter accurate using an USB mic and the proper calibration file?


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## informel (Jun 21, 2011)

If you apply the calibration file, yes it should be accurate. As for a laptop, you can buy a used laptop (but check the price against the new one, as people are asking way too much for the new one.
I have one mic like that, I cannot comment on precision as this is the only one I have.

note: I see you are in Saguenay, I hope you enjoy the Québec winter:sarcastic:


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## tonyvdb (Sep 5, 2007)

Steeve-O said:


> Is the REW SPL meter accurate using an USB mic and the proper calibration file?


Yes, very. The other really nice thing about it is its plug and play unlike using the old method of having to get something with phantom power like a mixer and all the extra wires needed.


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## Steeve-O (Dec 3, 2010)

I might go with the USB mic. I need to think about that. 

Yeah the Quebec winter is sort of long and rude. It has been -20 to -33 degree celcius where I like since almost 3 week straight and it keep going. And they say earth is warming up? All I know is that I don't stop puting wood in the furnace.


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## tonyvdb (Sep 5, 2007)

Its always strange how the weather patterns work. Here in Alberta its been mild most of the winter, Southern Alberta has even had record breaking high temps in January in the mid teens (60s F)


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## felixm (Jan 26, 2013)

With the CM-140 you only need a common audio cable to connect to PC: 3.5mm jack conector to plug in the CM-140 and 3.5mm jack (usually)or RCA (it depends on the PC line input). No needs for phanton power like with the analog mics.
The only downside is its frecuency response is not flat. It is flat from 60Hz to 10KHz. Below 60Hz its frecuency response goes down to -6dB at 20Hz and above 10KHz it goes down to -5dB at 16 KHz and -12dB at 20KHz.

If you make mesurements with REW use the calibration file to correct this error and your measurements will be flat.
The little drawback is at that frecuencies where it is not flat, you loss a little sensitivity and dynamic range wich I think it is no problem.

I have the CM-140 and have no experience with USB mics (I buy it before they were avaliable), so maybe I am wrong and I am losing something.

Are there more advantages of USB mics over the Galaxy CM-140?
If so, maybe I buy a new USB mic.


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## FargateOne (Mar 3, 2015)

To Steeve-O
I am from Québec. It is cold too!
I am new in EQing and all HT sound stuff. So I have a lot to learn.
I read a lot and had a few weeks ago the same dilema because I wanted to understand wht YPAO was doing. I found a new Galaxie CM-140 for 89$ US at B&H (108$ can livré à Québec). I do not have the calibration file (too expansive for now) but I will figure if I decide to go with REW EQ. For example felixm reply will help when the time comes.
This SPL helps me to put the sub at a better place and to see that my room is not as bad as I thought because it tells me that I have a pretty flat response between 20hz and 100hz.
P.S.: tu auras compris que mon anglais est approximatif !
Bye


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## rljsho (Jan 1, 2012)

I am looking for a quality SPL meter that can be used with R.E.W.. Has anyone used a Bogen Digital Sound Pressure Level Meter? The features and specifications appear to be able to supply all the data that R.E.W. requires and comes with a USB cable. Thank You.


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## Wayne A. Pflughaupt (Apr 13, 2006)

This meter doesn’t appear to have a line output for the mic, so I guess you only want it for the purposes of calibrating REW’s internal meter? The USB capability offers nothing for REW that I’m aware of.

Aside from features like waterproof or rugged construction, it should be noted that when it comes to sound level meters, “quality” means the ability to deliver accurate dB readings for noise levels. Most meters in this price range are Type 2 that are accurate +/- 1 dB. There’s no reason the Bogen shouldn’t be as good as any other meter in this price range. If you need something more accurate, you’ll have to move up to a Type 1 meter. They start at more than double the price of the Bogen.

Regards, 
Wayne


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## rljsho (Jan 1, 2012)

As you mentioned that the model SPLM didn't have a line output for the mic, my spec sheet indicates that it has an AC analog signal output jack,3.5mm. Are we talking about the same type of ac signal output that the Galaxy CM-140 has and has been recommended for use with R.E.W.? Thank You.


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## Wayne A. Pflughaupt (Apr 13, 2006)

So you intend to use the meter as a measurement mic also. Yes, that 3.5 mm jack has the same function as the one on the CM-140. However since there is no known calibration file for the Bogen it should be limited to subwoofer measurements, not full range. So honestly I don’t know what the Bogen brings to the table for REW, especially since you can get a _custom calibrated_ CM-140 from Cross Spectrum Labs for $40 less than the Bogen’s street price.

Regards, 
Wayne


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## rljsho (Jan 1, 2012)

I checked the Cross Spectrum Labs deal and it looks as if I want to have the equipment to take full advantages of R.E.W. I should order the CM-140 and the umik-1 at the same time. Would this be the best selection to make at this time? Thank You.


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## Wayne A. Pflughaupt (Apr 13, 2006)

No, you don’t need two calibrated mics. The UMIK-1 from miniDSP has a sensitivity figure that you can plug into REW. It will calibrate REW’s SPL meter, which means you won’t need a stand-alone meter.

Regards, 
Wayne


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## rljsho (Jan 1, 2012)

That is good to hear. Should I order the UMIK-1 from miniDSP or order the calibrated UMIK-1 from Cross Spectrum, which includes a USB thumbdrive with frequency response data? Thank You Wayne.


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## Wayne A. Pflughaupt (Apr 13, 2006)

You get a calibration file either way, if you get the mic from miniDSP I believe it’s downloaded. You might ask Herb from Cross Spectrum about the sensitivity figure for REW’s sound level meter. I think it’s either an option or there is a work-around.

Regards, 
Wayne


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## gadgtfreek (Oct 13, 2014)

Not to hijack, but...

For measuring SPL with REW/Umik-1, say to check XT32 levels afterward, is C weight and Slow still the proper setting for the REW SPL program (subs and speakers)?

I have my calibration file from CrossSpectrum loaded to REW with the "sens" file from Minidsp for my particular Umik-1.

This is part of my actual narrow 90 degree file that is loaded:



> Sens Factor =-.1543dB
> 4.33 -5.64 0
> 5.79 -3.65 0
> 7.24 -2.99 0
> ...


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