# Subwoofer calibration with Sinometer JTS-1357



## NixPix (Jul 11, 2010)

Hi all. I'm new to the forum and new to using REW. I have previously calibrated my setup using an SPL meter (JTS-1357) but now I want to go a bit further and try REW for an accurate reading. I have a few questions, sorry if these are "noob" questions.

My SPL meter is a Sinometer JTS-1357. I have tried finding info of how accurate is measures for subwoofer calibration but have not found anything conclusive. So first question:

Does anyone have any experience or information how accurate is measures 20-80Hz?

Since there are no calibration files for this SPL meter, will a REW measurement be accurate enough to be considered reliable?

Since the Galaxy CM-140 seems to have almost identical specification, should I be able to use that calibration file?

And lastly, almost embarassing to ask but, my SPL meter has a DC out and an AC out for connecting to external device, its the AC I need to connect to the LINE IN right? :scratch:

I have not made my first measurement with REW yet, planning on doing that later today.

/Thanks in advance for taking the time to help a REW-noob :help:


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## tonyvdb (Sep 5, 2007)

You would really have no way to know for sure if the readings you get with your Sinometer will be even close to the Galaxy, I highly doubt that either meter are truly "almost identical". Most meters do just fine reading lower frequencies it when you get into the higher range (above10KHz) that you separate the good meters from the bad.


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## NixPix (Jul 11, 2010)

tonyvdb said:


> You would really have no way to know for sure if the readings you get with your Sinometer will be even close to the Galaxy, I highly doubt that either meter are truly "almost identical". Most meters do just fine reading lower frequencies it when you get into the higher range (above10KHz) that you separate the good meters from the bad.


So in other words my JTS-1357 can be considered accurate enough to be fairly reliable without a calibration file? For subwoofer calibration that is...


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## tonyvdb (Sep 5, 2007)

not without a calibration file, You could try the Galaxy file and see what you get but i doupt that it will be very reliable. You can make one for your meter however you must have a detailed specification sheet of the Sinometer frequency response and thats not always easy to track down.
I cant seem to find the info on it right now however there is instructions on how to do it here somewhere.


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## NixPix (Jul 11, 2010)

Any information what so ever seems scarce about the JTS-1357 :| I doubt I can get ahold of a detailed freq response specification on the meter. 
umm maybe I am misunderstanding you, do you mean there's that kinda spec floating around this forum? Or only a guide how-to if you have the required freq response document?

What kind of deviations are we talking about with an uncalibrated meter? And at what freqs?


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## tonyvdb (Sep 5, 2007)

a how to guide if you have the required freq response document, Hopefully someone here will remember where it is located.


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## NixPix (Jul 11, 2010)

Okey. Thank you for your response. I'll google til my eyes bleed and try and find such freq response document then hehe  Also gonna do my first measurement and see what it looks like.


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

> Since the Galaxy CM-140 seems to have almost identical specification, should I be able to use that calibration file?


It’s not unusual for SPL meters in a general price range to have similar specs, but those specs generally apply only to their designated objective of measuring the SPL of noise, not measuring broadband frequency response. (There are meters that can do that, but they’re expensive.)

Any meter’s C-weighted setting should accurately track the frequency response of the C-weighting scale, but in truth neither the Radio Shack or Galaxy meters track C-weighting accurately in the bass frequencies. However, the Galaxy meter tracks more accurately than the Radio Shack.

That said, the Galaxy and Radio Shack meters are with .5 dB of each other from 125 Hz down to 28 Hz, which covers most of the subwoofer range you said you were interested in looking at. Therefore, since the Galaxy and Sinometer are in the same price range I’d expect their tolerances are pretty close as well, except perhaps at the lowest frequencies. But even from 25-16 Hz, the discrepancy between the two shouldn’t be more than a dB or two.

Regards,
Wayne


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## NixPix (Jul 11, 2010)

Wayne A. Pflughaupt said:


> It’s not unusual for SPL meters in a general price range to have similar specs, but those specs generally apply only to their designated objective of measuring the SPL of noise, not measuring broadband frequency response. (There are meters that can do that, but they’re expensive.)
> 
> Any meter’s C-weighted setting should accurately track the frequency response of the C-weighting scale, but in truth neither the Radio Shack or Galaxy meters track C-weighting accurately in the bass frequencies. However, the Galaxy meter tracks more accurately than the Radio Shack.
> 
> ...


Thank you for your response  Am I understanding you correct - I can use the galaxy cm-140 calibration file and it should be fairly accurate?


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## JohnM (Apr 11, 2006)

Don't use a calibration file, just check the "C weighted SPL meter" box and make sure the meter is set to C weighting.


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## NixPix (Jul 11, 2010)

JohnM said:


> Don't use a calibration file, just check the "C weighted SPL meter" box and make sure the meter is set to C weighting.


Right *check* and *check*  Thank you.


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## NixPix (Jul 11, 2010)

So I made my first couple of measurements  Here's how it looks with the subs ASP on default.
 

I understand the freq response but what does the sudden drop in phase at ~40ish Hz mean?

I did a few other measures with various settings in the sub ASP, and in some of them the phase goes up and down like crazy, that can't be normal right?


A few measures later. How does this one look to the "trained eye"? This is with some adjustment in the sub ASP + EQ in reciever.


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## JohnM (Apr 11, 2006)

Phase is cyclic, such that 180 degrees and -180 degrees are the same point, and usually plotted in a "wrapped" format (when phase reaches 180 degrees it wraps around and continues from -180 degrees and vice versa). What you see at 40Hz is a phase wrap occurring, you can use the graph controls to select "Unwrap phase" which will give you a continuous phase curve without wrapping.


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## NixPix (Jul 11, 2010)

JohnM said:


> Phase is cyclic, such that 180 degrees and -180 degrees are the same point, and usually plotted in a "wrapped" format (when phase reaches 180 degrees it wraps around and continues from -180 degrees and vice versa). What you see at 40Hz is a phase wrap occurring, you can use the graph controls to select "Unwrap phase" which will give you a continuous phase curve without wrapping.


So a sudden drop in the phase doesn't mean there is a problem with the phase? It's normal? What's considered "optimal", should the phase "follow" the freq response or it doesn't matter?

Sorry for all the "noob" questions hehe, just trying to understand all 

Here's a new measurement after further calibrations. Can't seem to defeat the 48Hz peak :|
 

oh and btw the Sub is an "AudioPro Ace-Bass 3"


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## JohnM (Apr 11, 2006)

NixPix said:


> So a sudden drop in the phase doesn't mean there is a problem with the phase?


No, it is just how phase is plotted.



> What's considered "optimal", should the phase "follow" the freq response or it doesn't matter?


You can ignore phase in most situations.


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## NixPix (Jul 11, 2010)

JohnM said:


> No, it is just how phase is plotted.
> 
> You can ignore phase in most situations.


Okey. Thank you for your answers  And also big thanks for an amazing program! Top class! :clap: :T


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