Anyone using a mic calibrator?
Not frequency response, just level - 94 / 114 dB @ 1 kHz. I do acoustic measurements, the mic has a cal file but the sound card I have has a gain knob. So FR should be right(ish) but who knows about overall sensitivity. So, calibrated reference source to the rescue.
B&K and GRAS make expensive ones and that's great when work is paying. But for hobby projects I'm looking for something cheaper. There are a few of them for sale on Amazon for around $100. Are any of them worth while?
Let's see, here are some examples...
Reed Instruments R8090 - $179 (the expensive one!)
This silver cylinder calibrator - sold by multiple vendors - ~$111
Grey rectangle with orange band calibrator - multiple vendors - $79
Black cyl with blue LCD - $109 (sometimes this one is called ND9B, but then it's ~$200)
Anyone know?
A bummer - these all seem to be targeted at SPL meters and accomodate 1" and 1/2" mics but I think the typical FR measurement mic is smaller. I can probably 3D print an adapter, if I seal it...?
Not frequency response, just level - 94 / 114 dB @ 1 kHz. I do acoustic measurements, the mic has a cal file but the sound card I have has a gain knob. So FR should be right(ish) but who knows about overall sensitivity. So, calibrated reference source to the rescue.
B&K and GRAS make expensive ones and that's great when work is paying. But for hobby projects I'm looking for something cheaper. There are a few of them for sale on Amazon for around $100. Are any of them worth while?
Let's see, here are some examples...
Reed Instruments R8090 - $179 (the expensive one!)
This silver cylinder calibrator - sold by multiple vendors - ~$111
Grey rectangle with orange band calibrator - multiple vendors - $79
Black cyl with blue LCD - $109 (sometimes this one is called ND9B, but then it's ~$200)
Anyone know?
A bummer - these all seem to be targeted at SPL meters and accomodate 1" and 1/2" mics but I think the typical FR measurement mic is smaller. I can probably 3D print an adapter, if I seal it...?
I bought and used the Reed R8090 for work a couple of years ago. I never had another calibrator to compare it to and we didn't splurge for the NIST certification, but if I recall correctly, it was within ~1 dB of the value reported by my UMIK-1.
We got it about 2 months before a 40% "workforce reduction" that I was a part of, so never had the chance to evaluate stability / reliability. Sorry that I don't have more insight to share.
I have the orange band one - It fits my Behringer ECM8000 perfectly. I don't have lab grade equipment to test its repeatability with, but it's $80 😉
I assume it is better than not having anything as a reference. I thought about maybe trying to power it with a DC supply and vary the input to see what the sensitivity to PS voltage was, but haven't got around to it.
I did hold an old RS SPL meter (too big by far) over the hole and it was fairly close to 94dB, maybe 93.5?
I assume it is better than not having anything as a reference. I thought about maybe trying to power it with a DC supply and vary the input to see what the sensitivity to PS voltage was, but haven't got around to it.
I did hold an old RS SPL meter (too big by far) over the hole and it was fairly close to 94dB, maybe 93.5?
Does anyone know how any of these work? The "standard" calibrator is called a pistonphone, and is what is sounds like. It's a mechanical piston on a crankshaft that moves back and forth a certain distance, and at a certain frequency generates a certain dBSPL,
What if you could measure the actual SPL accurately? I use an iPhone with SPLnFFT and found that it matches any SPL meter I have checked it against
https://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/
Not sure of the state of play with Android apps, but the hardware variations make it more difficult
Brian
https://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/
Not sure of the state of play with Android apps, but the hardware variations make it more difficult
Brian
This is the mic calibrator I've been using as an SPL reference for test mics and measurement systems for 15+ years. I checked 2 of them against Bruel&Kjaer & other industry standard calibrators at the physics dept of U of BC & they were accurate with 0.25 dB. It is usable with both 1/2" and 1" mics. I'd hope the current production is as accurate.
https://a.co/d/gbYpiTz
https://a.co/d/gbYpiTz
Same!
I've used a GRAS pistonphone, but that was at 200 or 250 Hz I think, not 1k. The one I've used most is the B&K 4231 - not a pistonphone, maybe piezo? I don't know. My experience with it has been good / consistent. But too pricey for me to buy for my garage.
I've got AudioTools by Studio Six Digital, on ios. It's been great! I had the 3.5mm calibrated mic for it from Dayton, but now my iphone doesn't have a 3.5mm jack and I haven't bought the USBC version of the mic yet. But that's neither here nor there. I want to use REW on a computer, and I would like calibrated levels. Phone Apps are a different party...
Wow, that's awesome that you've been using it for 15 years! It's good to hear that it's got that much history, has it been consistent in its performance for you over that time? That looks like the 'silver cylinder' version that I linked.
Also, I see iSemCon has a calibrator for sale that looks quite a bit, but maybe not exactly? like the silver cylinder. It's the SC-1 and it looks like it has a 1/4" adapter also! ...but it's $387...
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I use the Gain "silver cylinder". It's a 1kHz calibrator at either 94 or 124dB level. Yes you can 3D print an insert for whatever mic you like, just make sure the mic sits at the same depth as the insert it comes with. Has an o-ring seal that's not as important as you might think.
Prior to that I used an Omnimic for SPL reference, the low cost calibrator was within 0.3dB when I stuck the Omnimic in it, so it's good enough for me.
Prior to that I used an Omnimic for SPL reference, the low cost calibrator was within 0.3dB when I stuck the Omnimic in it, so it's good enough for me.
The Tekoplus claims to be class 1 or .25 dB accurate. It probably is for at least the first few months. The B&K uses an internal mike to stabilize it. That removes a lot of potential error from different mike front cavities (the biggest PITA with mike cal is that every vendors mikes are a little different).
The primary calibration is a reciprocity calibration, a really tedious process that needs three microphones, at least two of which are also useable as speakers. The pistonphone is the next step down and is dependent on the cam that pushes the pistons the displacement of the pistons and the internal volume of the chamber. This is where the different mike's front volume become an issue. Most class 1 mike vendors have published corrections for the B&K pistonphone. Otherwise you don't have a lot to go on.
However if you are tuning and testing your own speaker how much absolute accuracy do you need? +/- 1 dB should more than suffice. The involved stuff above is to get to the .1 dB level and that will always be suspect. If I did not have 10 mike calibrators I would get the https://a.co/d/gbYpiTz and get on with life. However with 10 calibrators, including GR reciprocity, I have no confidence that any are right.
The primary calibration is a reciprocity calibration, a really tedious process that needs three microphones, at least two of which are also useable as speakers. The pistonphone is the next step down and is dependent on the cam that pushes the pistons the displacement of the pistons and the internal volume of the chamber. This is where the different mike's front volume become an issue. Most class 1 mike vendors have published corrections for the B&K pistonphone. Otherwise you don't have a lot to go on.
However if you are tuning and testing your own speaker how much absolute accuracy do you need? +/- 1 dB should more than suffice. The involved stuff above is to get to the .1 dB level and that will always be suspect. If I did not have 10 mike calibrators I would get the https://a.co/d/gbYpiTz and get on with life. However with 10 calibrators, including GR reciprocity, I have no confidence that any are right.
I had 2. They were identical in performance when checked originally vs the B&K. They remained the same as each other for many years after. I sold one off a few years ago. Still using the 2nd one; I don't know if it has drifted.
For extreme consistency, you need 3 that measure identically. If one goes off, the other 2 should let you know.
But for a hobbyist, that's overkill.
Most universities have a sound lab & they'll have a reference calibrator. Since it only takes a few mins to check yours against theirs, they'll let you.
https://www.pcb.com/products?m=adp109
https://www.isemcon.net/shopus/product_info.php?products_id=5
If you don’t want to make an adapter
I am using this one, but bought not from Amazon:
https://www.amazon.com/UNI-T-Decibel-Digital-30-130dB-Measure/dp/B08PP5TMS7
It is more realistic, than my phone. Difference is ~15dB. Cannot compare to other ones, as I don't have any at hand and did not compared it measurements to other, more expensive.
https://www.amazon.com/UNI-T-Decibel-Digital-30-130dB-Measure/dp/B08PP5TMS7
It is more realistic, than my phone. Difference is ~15dB. Cannot compare to other ones, as I don't have any at hand and did not compared it measurements to other, more expensive.
This is my thinking as well.
A while back I heard a story from some someone at work. They had a DMM around and were getting strange readings. It took a long time to sort out, but the DMM which was marked as RMS was actually not, and was a peak meter that was calibrated to RMS values for sine tones. So mostly it is this level of error I'm looking to avoid in these very inexpensive waters. The most obvious thing I can think of to worry about is that level may depend on supplied voltage. Ron's idea here sounds like a good one to me..
Corrections for mic volume, pressure, ambient temp etc aren't particularly important to me as long as it's in the right neighborhood and not drifting.
I'll probably get the silver one and try to dream up some checks to run on it.
Thanks, all!
The rectangular one works fine for my purpose, which is using multiple mikes to measure using REW Pro. The Earthworks 1/4”insert works fine for my iSEMcon mics too. I do use a cheap o ring ($5 or so on Amazon) to keep the iSEMcon one centered.
I’ve used the black one with blue LCD.
I can confirm that it sucks the pair of AAA batteries, whilst the unit is off.
So to save the battery I take it out between uses. But the battery compartment is a little on the small size, so it’s a squeeze to get it in/out. A minor irritation I know, but I’m not sure I would recommend this model.
I did get in contact with the manufacturer of the grey one with the orange band (AZ Tech) who sent me to their authorised reseller Gain Express, so I guess they (Gain) can be trusted as a reseller.
However, only unusual thing is that sometimes these type of devices don’t have all the labels Eg. Missing ND9B label, or IEC label… I wonder why this is.
As far as accuracy for testing and tuning your own speakers I agree with @1audio. +/- 0.5 to 1dB is fine.
If you have an iPhone, it makes a class2 ( +/- 2dB ) with the NIOSH or Studio Six Digital app. When I’m about and about I can get a feel for how loud bars / clubs / concert halls can be.
🧐
I can confirm that it sucks the pair of AAA batteries, whilst the unit is off.
So to save the battery I take it out between uses. But the battery compartment is a little on the small size, so it’s a squeeze to get it in/out. A minor irritation I know, but I’m not sure I would recommend this model.
I did get in contact with the manufacturer of the grey one with the orange band (AZ Tech) who sent me to their authorised reseller Gain Express, so I guess they (Gain) can be trusted as a reseller.
However, only unusual thing is that sometimes these type of devices don’t have all the labels Eg. Missing ND9B label, or IEC label… I wonder why this is.
As far as accuracy for testing and tuning your own speakers I agree with @1audio. +/- 0.5 to 1dB is fine.
If you have an iPhone, it makes a class2 ( +/- 2dB ) with the NIOSH or Studio Six Digital app. When I’m about and about I can get a feel for how loud bars / clubs / concert halls can be.
🧐
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If you are referring to the gain knob of the sound card, you can simply calibrate this by applying a known AC voltage to calibrate the sensitivity of the input.
Mic sensitivity is a different story. I tend to believe the datasheet number. 🙄