# Strange RS SPL meter calibration results



## Ilkka

A friend of mine wanted to have his newer type analog Radio Shack SPL meter calibrated, so he sent it to me. I noticed some strange behaviour while calibrating it against to my professionally calibrated microphone. The amount of correction needed wasn't anywhere near to what Sonnie's correction file suggest for this type of meter. I believe a few graphs explain it better. All the measurements were done with the REW (4.00), I merely used the TrueRTA to show them.

The first graph shows the difference between the correction files for my (i.e. my friend's) new analog meter and Sonnie's new analog meter. Quite a difference!










The second graph shows the difference between the correction files for my new analog meter, my old analog meter, and Sonnie's old analog meter. As you can see, they all match reasonably well (within ~3 dB). My new analog meter seems to be only a little bit better than the old ones.










*So what does this all mean?* Assuming both Sonnie and I took accurate measurements, some of the new analog meters are better then the others. The worse ones aren't much better than the old analog ones. This will definitely cause some strange measurement results when all the people having the new analog meter are using the same correction file. Their frequency response can look like having much more low frequency roll-off than it in reality has. 

So it looks like some of the new analog meters are still having the insides of the old analog meter. How do we separate them? I took a picture of the QC stamp, which reads "10A05". *Could people post their QC codes for all the RS meters they have?*

Here's the list:

*New analog (soft-look)*
04A06 (tatkinson)
12A05 (Chrisbee, toecheese)
10A05 (Ilkka's friend)
06A05 (WillyD, Average Joe)
4A05 (norpus)
02A04 (JRace)

*Old analog (boxy)*
07A06 (Jeffeory)
11A05 (daxie)
12A03 (Ilkka)
10A02 (Peter De Smidt)
09A01 (snatcher)
9A4 (Chrisbee)


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## brucek

> So it looks like some of the new analog meters are still having the insides of the old analog meter.


I can't see any other explaination. Granted, Sonnie only tested a few when the calibrations were done, but a random pick of two that reveal the same response ain't bad....

I seem to remember when Chrisbee said his new analog didn't give him anywhere near as good a response as he was measuring with the old meter. I wondered at the time why they weren't the same... This could be it.

I do have to agree with something you've commented on before, and that's if you want to test down to 10hz it is probably a better idea to get a good microphone like many of us have resorted to..

brucek


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## Ilkka

brucek said:


> I can't see any other explaination. Granted, Sonnie only tested a few when the calibrations were done, but a random pick of two that reveal the same response ain't bad....


I believe RS made some changes (different mic capsule etc.) to their analog meters, but not necessarily at the same time they changed the outlook. It is more than likely that both Sonnie's meters were these "upgraded" ones, while my friend's isn't. Eventhough they all look the same.



> I do have to agree with something you've commented on before, and that's if you want to test down to 10hz it is probably a better idea to get a good microphone like many of us have resorted to..
> 
> brucek


I agree 100%. :bigsmile:


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## Chrisbee

Recently purchased soft-look analogue: QC 12A05 TEC

12 year old (?) boxy shaped analogue: QC 9A4 TEC

I shall do an REW sub response curve for each meter without loading any meter calibration files tomorrow.


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## brucek

> I shall do an REW sub response curve for each meter without loading any meter calibration files tomorrow.


I would do it near field to remove as many spikes etc from the room that makes comparisons difficult.

I'd tape the two mics together.....

brucek


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## Sonnie

This could definitely throw a kink in things, especially for those purchasing newer analog meters.

I do have the $99 Galaxy CM-140 in hand, but haven't done any measurements with it. It may be that we simply need to advise people that they will need to either have someone check their RS meter for accuracy or purchase one of the CM-140's, if it turns out to be as accurate as we suspect it will be.


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## Chrisbee

Okay. Nearfield measurements at 4" from the dustcap of bottom driver of my IB. 

Both meters carefully calibrated individually to 80dB prior to measurement. 

Meter calibration file in REW cleared prior to each measurement to ensure no cal file loaded.

Here's the old analogue meter.










Here's the new analogue meter.










Like two peas in a pod!!!


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## brucek

Yep...... I guess you better use the cal file for the old meter.

Ilkka has made an interesting discovery?

What can we do about it? :scratchhead: 

brucek


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## Chrisbee

Those of us with two meters at least have a control (of sorts). 

The chances of two meters being so alike is er.... very unlikely. 

It certainly explains why my new meter behaves exactly like old meter when using the old RS analogue cal file.

But can we trust Sonnie to have got the old RS analogue cal file right? :devil: 

How many were in his sample? 

Does this mean I can now have my bass back which Sonnie stole by giving us the new rs analogue file?


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## Ilkka

Chrisbee said:


> Okay. Nearfield measurements at 4" from the dustcap of bottom driver of my IB.
> 
> Both meters carefully calibrated individually to 80dB prior to measurement.
> 
> Meter calibration file in REW cleared prior to each measurement to ensure no cal file loaded.
> 
> Like two peas in a pod!!!


Thank you! Just what I thought. You should definitely use Sonnie's *old* analog correction file for both of them. 

And might I say, that's a fine looking NF response. When you put the correction file in, you'll have loads of low frequency gain! How does it look at the LP?


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## Chrisbee

Ilkka said:


> Thank you! Just what I thought. You should definitely use Sonnie's *old* analog correction file for both of them.


Agreed.



> And might I say, that's a fine looking NF response. When you put the correction file in, you'll have loads of low frequency gain! How does it look at the LP?


This was my best curve after a 16dB 120/60BW boost at 20Hz using the BFD.


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## Ilkka

Chrisbee said:


> This was my best curve after a 16dB 120/60BW boost at 20Hz using the BFD.


That looks strange. Could you take a NF measurement (4" from the dustcap) WITH the right correction file loaded? Do not use any BFD boost etc.


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## brucek

> How many were in his sample?


The purpose of the exercise to create the new calibration files came from the widely held claim that the new RS meters were different and more accurate than the old RS meter and so Sonnie agreed to test a few against his calibrated ECM8000. Then we could come up with closer cal files than the low resolution one that had been circulated for years.

Sonnie got two new digital meters, two new analog meters and his own old analog to compare against the ECM8000.

A new file was created for the old RS meter against his single old RS meter.
A new file was created for the new analog meter against two new analog meters.
A new file was created for the new digital meter against two new digital meters.

The decision was made that if two meters compared the same, then that was as large a sample as we would use. The two new analogs tracked well and the two new digitals tracked well. Arguable a small sample, but since Sonnie paid for these himself, I think it was good enough.

Once completed, Sonnie did a retest to compare the final results against his ECM. It was close enough and we posted the results for anyone who dared to use them.....

Here is a jpg of a final test of the ECM8000 against the two new digital and two new analog with their posted cal files loaded. This pic didn't have the old analog in it, but it was just as accurate when compared with its cal file at the time.

It would indeed appear though, that they may have switched the mic elements in the new ones at some time after they started producing them? What can you do.











brucek


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## Chrisbee

Ilkka said:


> That looks strange. Could you take a NF measurement (4" from the dustcap) WITH the right correction file loaded? Do not use any BFD boost etc.


Nearfield without boost:










Thanks for the explanation brucek.


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## Sonnie

Also keep in mind that Ilkka created correction values for an old analog meter with a completely different mic and we were within 1.5db of each other, except at 10Hz where I still say he had a blurp... :bigsmile:


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## Ilkka

Thank you. But that doesn't make sence...? How can THIS...










Turn into THIS when you apply the correction file? The deep bass should go UP, not down.


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## brucek

> Turn into THIS when you apply the correction file?


Scaling.....




> With BFD boost nearfield old analogue file new meter.


Your scaling makes it hard to interpret.

Can you repost it with vertical scale 45dB - 105dB and horizontal 10Hz - 200Hz.....

brucek


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## Chrisbee

brucek said:


> Scaling.....
> 
> Your scaling makes it hard to interpret.
> 
> Can you repost it with vertical scale 45dB - 105dB and horizontal 10Hz - 200Hz.....
> 
> brucek


 Both plots are in exactly that format.

I should have scaled to 800 not the 880 I have been using.

I have also lifted the target curve to 80dB which is my calibration level in REW.


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## Chrisbee

The first plot is nearfield with the BFD boost but no cal file.

The second plot is no BFD but with cal file.

I think.:scratch:


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## Ilkka

Chrisbee said:


> The first plot is nearfield with the BFD boost but no cal file.
> 
> The second plot is no BFD but with cal file.
> 
> I think.:scratch:


Arrgh... :wits-end: :sarcastic:


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## Chrisbee

We can't all be experts like you, Ilkka. 

I now have a whole mass of completely meaningless graphs because you questioned the old V new RS meter. :crying: 

I now have whole threads which are completely meaningless because they are based on the wrong meter cal files. :blush:

But I bet my bass is better than yours even if I can't manage a simple graph.


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## Ilkka

Chrisbee said:


> We can't all be experts like you, Ilkka.


I was just kidding. :innocent: Although it does help if you tell ALL the settings etc. used for each graph.



> But I bet my bass is better than yours even if I can't manage a simple graph.


Hey! Have you heard my bass? It's not that bad either...


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## Chrisbee

Ilkka said:


> I was just kidding. :innocent: Although it does help if you tell ALL the settings etc. used for each graph.


I do. I just forget what my abbreviations mean ten minutes after saving the graph.:blush:



> Hey! Have you heard my bass? It's not that bad either...


Did you ever build that secret infrasonic device you were threatening to put together? :devil:


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## Ilkka

Chrisbee said:


> Did you ever build that secret infrasonic device you were threatening to put together? :devil:


Nope, it's currently on hold. Although it wasn't anything "secret"... Just a normal IB, only built to a regular room door. :bigsmile: The rest of the apartment (yes :coocoo: ) would have been the backspace for it. I could fit two 18" to it. But unfortunately it's not going to happen now, maybe later...


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## Chrisbee

Does your RS meter go right off the scale on the 120dB range? Mine does! 

Better get a couple of F1 Q18s in your door! Nice! :devil:


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## Ethan Winer

Folks,

Sonnie emailed me and asked me to chime in. Here's what I can offer:

First, every Radio Shack SPL meter is not necessarily the same. I can imagine they buy whatever capsule is the least expensive on the open market each time they place an order. More to the point, even very cheap electret condenser capsules are quite accurate at low frequencies. And at high frequencies, it takes a lot of skill to properly measure a microphone's response. I'm skeptical that most folks who post "compensation charts" have enough experience with microphone calibration.

Below is a graph I made showing the low frequency response of my Radio Shack SPL meter compared to my expensive AKG calibrated microphone, as measured in my home studio. As you can see, the two track each other almost exactly below 200 Hz. I also tested both microphones to 20 KHz, and they tracked each other within 1 dB up to 800 Hz.

However, I would not trust any inexpensive meter or microphone beyond a few KHz. I recently bought a high-end DPA measuring microphone and, like similar models from Earthworks, this one has a tiny diaphragm to be usably accurate to beyond 20 KHz. I haven't yet done a side by side with either my AKG mike or RS meter, but when I do I'll post the results here.

--Ethan


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## Chrisbee

It would show a good example if the moderators posted their own RS SPL meter QC numbers! :devil:


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## WillyD

I have a new style analog meter with a QC code of 06A05.


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## Snatcher

Old style analog, QC is: 09A01 TEC


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## Brian Bunge

I'll post mine later this evening if I can remember where I put the thing.


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## Sonnie

Ethan Winer said:


> First, every Radio Shack SPL meter is not necessarily the same.


Yeah... we are very aware of this fact. However, we have tested quite a few, albeit not in a professional setting, and found several to be similar in their measurements. We are not trying to make this an exact science, but merely get as close as we can. Plus, remember that we are using this strictly for the low-end... 10-200Hz.

What shocks me is your RS meter needs no correction whatsoever... which would be the first I've ever known to be perfect... :scratch:


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## Sonnie

Actually, does the QC Code do us any good if the meter has not been calibrated against a better mic? :hissyfit:


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## GPM

Greets!

Mine is an early analog unit with a 12A7 date code and shortly after I bought it the local G.E. instrument test lab confirmed it was 'close enough' to what's published in the manual, i.e. with 'C' weighting it's ~flat from ~20-2 kHz, rising to ~ +7 dB/6500 Hz, then falling to ~ -6 dB/20 kHz.

GM


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## daxie

Mine is a QC11A05

It's an old 2050-style one...

Is there already something I can conlude out of this info regarding correction values?


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## toecheese

Mine is an analog- looks like the picture at top of thread (soft look?).

12A05


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## JRace

mine is also the newer analog one (as shown in the pic)

q.c.
02A04
TEC


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## tatkinson

I bought a new (soft style) Sound Level Meter about 4 weeks ago.
Code: 04A06

Tuck


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## brucek

Ethan wrote:


> More to the point, even very cheap electret condenser capsules are quite accurate at low frequencies.


Perhaps, but certainly not the element that was used in the original old analog meter Model 33-2050. This one was down about 12dB at 20Hz and 27dB at 10Hz. Enough of these were cross checked to assume that the 'amateur' calibration file that the Shack posts is fairly accurate.

When we tested several of the newer models we noticed that the response had improved and concluded that the newer models had a new element. We tested and created another different calibration file for these newer meters.

The trouble here is that we now find that perhaps the change of mic element didn't actually occur at the same time as the model changed. Who knew? :huh: 

We don't really know what to do about it other than post the date codes of known meters that have been verified as to a newer or older element in them. These can only come from people who have checked the responses between a RS meter and a professional mic or between an old RS meter and a new RS meter. Any other codes are meaningless.

Ethan, you didn't provide your RS meter code....

brucek


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## Peter De Smidt

I have an old style analogue meter, QC 10A02 TEC.


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## AverageJoe

New style analog, QC code of 06A05


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## norpus

I have a 1 year old soft-look analogue: QC 4A05 TEC


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## GPM

brucek said:


> Perhaps, but certainly not the element that was used in the original old analog meter Model 33-2050.


Greets!

Hmm, my 42-3219 has the same basic case with different guts than the 33-2050 and is 10-20 yrs older (can't remember when model numbers changed), not to mention much more accurate, so if you're considering it the original, then please delete my posts.

GM


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## Guest

Old style analog, QC is: 07A06 TEC


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## brucek

> Old style analog, QC is: 07A06 TEC


Are you saying yours is an old style 33-2050?
When did you purchase it? In 2006?

brucek


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## Ilkka

Thanks, keep those numbers coming. 

I will contact Radio Shack for further info, but I'm pretty sure the first two digits are the month (01-12), and the last two digits are possibly the year (or some other running number, higher number indicating newer meter).

Sonnie, do you know who owns those two new analog meters you tested?


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## Chrisbee

We can draw at least one conclusion: 

toecheese's new model has the same number as mine and must therefore need the old analogue correction file. 

Do we have anybody with 12AO5 or 9A4 and another closely matching meter response? We could then add another meter code with an old analogue response.

9A4 could be 1994. It fits the meter's age quite well. 12AO5 is probably 2005.


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## Ilkka

Chrisbee said:


> We can draw at least one conclusion:
> 
> toecheese's new model has the same number as mine and must therefore need the old analogue correction file.
> 
> Do we have anybody with 12AO5 or 9A4 and another closely matching meter response? We could then add another meter code with an old analogue response.


We can at least add my friend's 10A05 on the list of having the old response. And probably every meter with a code smaller than 12A05 (could go even higher).


> 9A4 could be 1994. It fits the meter's age quite well. 12AO5 is probably 2005.


Quite possible. (btw, it's 05, not O5)


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## Chrisbee

So now we just need the turnover point when the new calibration took place.


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## Sonnie

Are we confusing what we are calling old and new now? Maybe it's just me that's confused.

Toecheese has one of the meters I calibrated ... Model 33-4050 and it uses the newrsanalog.cal file. QC is 12A05.

FlashJim has the other unit. I've emailed him, but not heard from him yet. Perhaps Wayne could give him a call at home tonight.

I have one of the Model 33-2050 RS Meters that uses the oldrsanalog.cal file and it has a code of 09A01.

My digital unit has a code of 02A06 and it could survive off the newrsanalog.cal file.


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## Ilkka

Sonnie said:


> Are we confusing what we are calling old and new now? Maybe it's just me that's confused.


33-2050 (boxy) = old
33-4050 (soft-look) = new



> Toecheese has one of the meters I calibrated ... Model 33-4050 and it uses the newrsanalog.cal file. QC is 12A05.


That's strange. Chrisbee has the same code, but his has the old response... That is a bummer.


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## Chrisbee

toecheese's new model 33-4050 has the same code number as mine but my two meters are too alike to tell apart in their REW raw response without calibration files loaded. So they should both use the old analogue correction file despite one being brand new and the other from the 90s.

I'll check mine again tomorrow. It's very late here now. Goodnight.


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## JohnM

I have an 04-A04 marked 33-4050 analog meter, I'll compare it with my calibrated mic this weekend if I get a chance.

Edit: found a measurement I did a year ago but was measuring a small bookshelf speaker, so only good down to 40Hz or so. The RS meter has inverse C weighting applied but no cal, the MP1R mic is using its cal file. Quite close (within 1dB) from 40 - 140Hz.


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## F1 fan

My Wife works at a test instrument calibration lab and informed me today that they may have some results for the Realistic meters on file.They don't do the meters and mic's in house but send them to a third party at a cost of $125:raped: I will post the data when she is able to find it for me.


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## Brian Bunge

I have a 33-2050 (probably 5-6 years old) with QC 04A99 TEC.

BTW, hello to Greg Monfort from Palm Bay, FL!


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## Sonnie

JohnM said:


> Edit: found a measurement I did a year ago but was measuring a small bookshelf speaker, so only good down to 40Hz or so. The RS meter has inverse C weighting applied but no cal, the MP1R mic is using its cal file. Quite close (within 1dB) from 40 - 140Hz.


There is actually less than a db of correction from 40Hz up to 105Hz... it's below 40Hz where it starts to need help... more specifically below 30Hz.



F1 fan said:


> My Wife works at a test instrument calibration lab and informed me today that they may have some results for the Realistic meters on file.They don't do the meters and mic's in house but send them to a third party at a cost of $125:raped: I will post the data when she is able to find it for me.


Exactly... it is very expensive to have an SPL meter calibrated, if you can even find anyone to do it.

My recommendation going forward will be to purchase the Galaxy CM-140 for $99 or the equivalent Voltcraft meter.... which neither needs any correction at all.


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## Guest

I bought this RS meter recently, and I'm assuming it's a newer model. The QC code is:

05A06


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## blekenbleu

My 33-2050 has QC 2A3 TEC; it was never calibrated
but I spent enough time in 1996 reconciling it with my Parsons "Sound Check 2"
to be satisfied that its C weighting was close enough for my purposes.
I am considering getting my Denon DM-S305 calibrated,
since it does not spend much time configuring multEQ for my AVR-5805mk2...


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## Prof.

I bought my RS meter about 2 months ago...It's the model 33-4050 with the QC code 12A05..


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## SteveCallas

DrJon and Ryan both have Behringer mics - next time I visit one of them, I'll compare it to my digital RS spl meter. I'll provide my number when I get home this weekend.


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## F1 fan

Mine is the 33-2050 purchased in around 90 or 91 with code 8A0 TEC.


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## southworth

My meter is a digiatal model and the Q.C. code is:

04A00

Do the digitals have the same issue?


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## Guest

I`m guessing here,but I believe mine to be about 7 years old--QC 09A01


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## Mitch G

Model 33-2050.
QC code: 09A01

No idea how old it is (bought it used), but the instructions inside have a date of 12/99 on the back page.


Mitch


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## canaris

Mine is a digital no:33-2050- QC 9 A6 TEC


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## tigerpawgt

model 33-2050
QC code: 10 A 02

Its been around too long to recall when I bought it.


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## Blue Dude

I have a 33-2050 (old style) with a QC code of 7A7. I bought it "new" (actually it was on clearance) about three years ago.


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## John S

I also have an old style 33-2050.
QC is 09A00
Got it about 4 years ago.


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## Miron

Hi all.
Sorry I can't really help here but, as info, I have both analogue and digital RS SPL meters as well as one Shure mic. They all meassure quite close.


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## fibreKid

I have the new style (soft look) 33-4050
QC code 04A04

I'm currently using an ECM8000 mic with REW.


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## GPM

Brian Bunge said:


> BTW, hello to Greg Monfort from Palm Bay, FL!


Greets!

Palm Bay, eh? I emailed you several times after the news showed the damage a twister did in the vicinity of where you/your parents lived awhile back, but didn't get a response or saw any more speaker follow-up posts on the Atlanta HT, so assumed you'd been KO'd, not blown all the way to Fla.!

GM


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## rectorydp

I have a new style analog purchased in March 2005 in the UK. The QC code is 06A04.

David


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## Chrisbee

New and old meters side by side nearfield to my bottom IB driver.
There is a mismatch in overall sensitivity. The old analogue reads 3dB higher.
The curves themselves are as near identical as anyone would care for our purposes. 
I plugged both meters into the same twin coax cable and used Left and Right in REW to switch between them.


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## Chrisbee

For the spatially challenged: Both together. 










12 years apart but still looking good. :T


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## Guest

Sonnie,

My QC code is QC 06A03 TEC.

If you really want me to give you my view on this problem that you're having? Then I've updated my profile for those that don't know who I am!

(Just trying to be polite and prevent further confusion, That's all!)

Woodworld


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## Guest

brucek said:


> Are you saying yours is an old style 33-2050?
> When did you purchase it? In 2006?
> 
> brucek


Sorry! Old style (box shaped) digital (QC is: 07A06 TEC) which I purchased in Dec 2006

DrJ


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## Guest

Model # is 33-2055


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## Jeje2

*Don't shoot the messenger...*



Ilkka said:


> A friend of mine...


And the guilty one to this mess joins this thread. - please don't shoot :surrender: 
(First thanks to Ilkka for willingness to calibrate my SPL :hail: )
One info though - bought my SPL in January 2006 from a local reseller. (Has good reputation)

One question though - how can you solve this problem with only the QC Code? (Wouldn't you need to also know how each meter behaves?)

Total rockie in all this - it's just that I'm currently uppgrading my speakers (sold old one's already a month ago :dumbcrazy: :coocoo: ) and as have tested different new ones I've been disappointed with the behaviour in my flat. So now seeking some understanding to what could be the problem. (currently suspect 200-500Hz region - it's heavily damped in my flat)


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## brucek

> Wouldn't you need to also know how each meter behaves?)


Yes, of course. But we also wanted a peek into what sort of numbers were out there.
To be meaningful we obviously need people with a new RS meter combined with an old RS meter or calibrated mic (i.e. ECM8000). These people are able to do a comparison.

So far it looks like the interesting date code is 12A05, since we have one with that code that acts like an old analog and another with that code that acts like the new analog. Perhaps this could be the switching point?

Here's the data in date order (with a few comments)......



Code:


[b]New analog 33-4050 (soft-look)[/b]
06A06 {KrisitSwallow)
05A06 (Arkasha)
05A06 (aeon)
04A06 (tatkinson)
04A06 (BoomieMCT)
04A06 (Kerbango)
02A06 (Sonnie-new digital meter) >>> acts like a soft look 33-4050 
12A05 (Prof)
12A05 (toecheese) >>>>>> acts like new soft look 33-4050 (calibrated by Sonnie) 
---------------------------------------------- possible changeover point........................
12A05 (Chrisbee) >>>>>>> acts like old boxy 33-2050 
11A05 (ae93qti)
11A05 (Gizmo)
11A05 (dknightd)
10A05 (Ilkka's friend) >>>>> acts like old boxy 33-2050
07A05 (Exocer) 
06A05 (WillyD)Average Joe)
06A05 (Average Joe)
4A05 (norpus)
06A04 (rectorydp)
04A04 (fibreKid) 
04A04 (PeteD)
04A04 (JohnM) >>>> he will test
04A04 (privateradio) >>>> acts somewhere between new soft look and old analog 
----------------the meter of privateradio above compared with an old analog and new analog cal file  
against an ECM8000 exhibits interesting results. It makes the theory that we could establish a changeover date abit more difficult.......
02A04 (JRace)



[b]Old analog 33-2050 (boxy)[/b]
11A05 (daxie)
12A03 (Ilkka)
08A03 (DMF)
06A03 (woodworld)
03A03 (wackii)
10A02 (Peter De Smidt)
10A02 (tigerpawqt)
09A01 (snatcher)
09A01 (jc2020)
09A01 (mitch)
09A00 (John S)
08A00 (nova)
04A99 (Brian Bunge)
10A9 (tdamocles)
7A7 (blue dude)
6A7 (rcarlton)
3A5 (brucek)
9A4 (Chrisbee)
2A3 (blekenbleu)
8A0 (F1 fan)
6A0 (Kerbango)



[b]Unusual type[/b] - hard to determine what to do here...

07A06 (Jeffeory) >> old digital 33-2055 this one is very strange?
06A01 (dent) >> old digital 33-2055 

07A02 (frockc) >> old digital 
04A00 (southworth)  >> old digital
9A6  (canaris) >> old digital 33-2050

brucek


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## Guest

> Ilkka wrote:
> A friend of mine...


To jeje2,

Terva! from Woodworld,


> So now seeking some understanding to what could be the problem. (currently suspect 200-500Hz region - it's heavily damped in my flat)



German company called Cara, do some nice programmes for what you want. Program called Cara 2.0

If this is not the way you want to go..

Guy called Bob Katz, at Digital Domain, written lots of easy texts on your problem. Check him out.

Woodworld


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## Guest

I have heard that radio shack sold the rights to its spl meter to another company named Audio Technologies Inc (ATI) i recently bought an spl meter from them, this meter looks uncannily like the "new" radio shack meters, but has no QC sticker on it anywhere.
Is radio shack still producing their spl meter, or have they actually sold the rights to these guys?


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## fibreKid

Hi Bruce;

I guess I should send my mic off to get a matching cal file :bigsmile: 

-john


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## Sonnie

I'm thinking the solution is going to be one of the following:

1. Find a professional to calibrate your SPL... probably $125 or more (obviously not worth it so this is really not an option).

2. Find a friend or buddy with a calibrated mic and see if they will check your SPL meter for you.

3. Buy a Galaxy CM-140 or the Voltcraft equivalent for 100 bucks and be done with it... practically no calibration needed.


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## Guest

New style analogue: 05A06


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## brucek

> I guess I should send my mic off to get a matching cal file
> 
> -john


The ECM with sonnies cal file should be quite close. It would be close enough to establish whether your "new RS meter" was closest to the ECM8000 while using the old or new calibration file. The data in the list says it should act like an old RS meter 33-2050..

brucek


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## nova

Well, FWIW mine is: 08A00 old analog box.


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## wackii

I got mine about 3 years ago. 

Model: Q.C 03A03 TEC


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## ae93gti

11A05 for me, bought 6 months ago.


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## dknightd

Mine is model 33-4050 (new one I believe)
it is Q.C. 11A05 - TEC

Thanks for trying to sort this out. There seems to be considerable variabliity in these things, perhaps even among those made near the same time. :dizzy:

FWIW as near as I can tell the old correction curves seem to be pretty close to how the meter behaves, but I have not had it calibrated.


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## tdamocles

old - 10a9


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## rcarlton

Model 33-2050
Q.C. 6 A7

Bought it in 1998.


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## BoomieMCT

Model 33-4050
04A06

If anyone in Northern Virginia can help me figure out what .cal file I should be using (as I have nothing to compare this to), I'd me much obliged.


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## brucek

Well, I'm not from Northern Virginia, but since your new analog meter was produced after Sonnies, then I'd say you would use the newrsanalog.cal file......

brucek


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## Guest

Digital meter, about 2 years old: 08A03

Since the first two digits are stamped, I wonder if they indicate the test station. The last three might reflect either the design/build revision (possibly affecting response) or the test revision.


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## brucek

I would say it's simply a date of production. The dates and when purchase was made seems to be fairly consistent.

08 = August

03 = 2003

brucek


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## jerstamb

My Digital meter 33-2055: 06A05 TEC. Purchased Dec '05.
However I made some modifications to the circuit board. These mods include increasing the series coupling capacitors to the circuit board. I found this information on "the other forum". :bigsmile: 

Cheers, Jerry


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## Gizmo

i got a 11A05


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## Exocer

New analog meter version "07A05"


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## brucek

Exocer,

Looks like you're below Ilkka's friend.... Perhaps you need to use the old analog cal file....... see the list.

brucek


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## brucek

Interesting when we look at the graph of privateradio's new analog meter compared against the ECM8000.

He took a nearfield measurement while using both the new meter cal file and the old meter cal file. 

At first glance, the ECM8000 looks closer to the new meter cal file, but I think if you trace offset at ~100Hz and bring the lines together at that point (since that's where the cal files are all approximately equal), then I think his new analog meter is closer to the ECM8000 when he uses an old analog cal file for the new soft look meter. This would be consistent with the response I would expect, given the date of his meter (see the compiled list).

Anyway, this ones a hard call....











brucek


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## Dent

Digital meter: 33-2055
06A01


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## KristiSwallow

Ilkka said:


> Could people post their QC codes for all the RS meters they have?


Mine is 06A06


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## Kerbango

New Radio Shack Analog Meter Model 33-4050 QC 04A06

Old boxy ADC SLM-3 Analog Meter. Tag in the battery compartment says 6A0 but is not preceded with QC. Looks exactly like the old Radio Shack Analog meter. Made in Korea by Audio Dynamics Corporation, a BSR Company.


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## Dent

So is there any help for us RS digital meter owners as to which correction file to use? I have been using the newrsdigital.cal since my meter is the digital one but this whole thread makes things confusing. I'm also not sure how you guys are deciding to call the digital meters old or new. As far as I can tell from these posts, the digital meter hasn't had its look changed or its model number changed since it started, unlike the analog one, so what makes you call one old digital or new digital and again, which correction file to use?


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## brucek

You can see the list on page 4 of this thread and make a decsion on what you think is best.

I simply posted the list from the information people gave. We know of only three types of meters. There were some members who posted with information that I put at the bottom of the list, since I didn't really know what to do with it. We wanted model and serial. There were some entries of old digital 33-2050 and old digital 33-2055? Kinda confusing, so it didn't make the list.

I feel there are three types as shown in the Downloads section of the BFD forum with pictures.

Most people seem to either have the old or the new analog meter as seen by the list. It was with the new analog that the problem arose about the output not being consistent between like meters. We had a couple of verifications, so we decided to make a list. It's the best we can do. No one has forwarded any specific information about the digital meter being inconsistent with its cal file, but that's not to say it doesn't have a problem.

So the answer to your question is, "I don't know?"....

My recommendation is to buy a good microphone. Sonnie is working on a new one called a Galaxie CM-140 that looks good. He'll post a cal file when he gets finished....

brucek


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## PeteD

I have the 33-4050:
04A04

Hey brucek, your note on page 4 says this acts between the new soft look and old analogue...what does this mean exactly?

Has JohnM tested his, yet (below 40Hz)?

This may account for some of my (apparent?) lack of room gain at the low end, if the correction factors should be larger that the new meter cal file.

Pete


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## brucek

From the lists I would generally say you have a number that should respond like the old analog meter 2050. But we did have one unusual reading from privateradio where his was producing results you couldn't nail down. It throws a bit of a wrench into the list.

See this thread.

I would say yours is likely closer to the old analog type if it's consistent with the list, but I certainly can't say for sure. To be sure, you need a decent mic like the ECM8000.

brucek


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## CdnTiger

I have both the really old 42-3019 (I bought it used and someone has written 1-17-83 on the box - 1983?) and a soft-looking analog 33-4050. The 42-3019 code is 8A2 and the 33-4050 code is 11A06. It looks like below 100 Hz the old meter had a problem showing correct absolute dB level, although the general shape of the traces are the same. The yellow trace is the 42-3019 and the red trace is the 33-4050. No correction values were loaded for either measurement, except to check the C weighted SPL option.


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## Geoff Gunnell

I have the digital RS meter, 33-2055, with the same QC code as Ilkka's meter: 12-A03


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## Jerm357

I look at the graph Ilkka made and it looked like it had about the same drop in the low end that my sub's graph has. And since this response is just about the same as sonnies old analog meter file I decided to install it instead of the new digital file that I was using. Heres a pic of my old measurement with the old analog file installed, Now the measurement has not been adjusted by the calibration file yet but you can see the rolloff is about the same. Im going to take some more measurement tomorrow to see what happends, Im almost getting my hopes up that this might be my problem. What do you guys think of this? Could it be that some of the new digital meters are off like Ilkka's new analog one raying: ? My numbers on my digital meters are 06A05


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## brucek

> What do you guys think of this? Could it be that some of the new digital meters are off like Ilkka's new analog one ? My numbers on my digital meters are 06A05


From the list on page 4 of this thread it appears you are a candidate to use the old analog meter file with your meter. We just don't know for sure.

Our solution is really to encourage purchase of the Galaxy meter that sonnie is presently taking orders for..

brucek


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## muzz

Old-33-2050
QC 03A99

I also believe it's a date code.....
I've had this meter for about 6 or 7 years.


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## Guest

New analog: 33-4050
QC 02A07

Bought it a few weeks ago from Sonicboom audio to calibrate my system and plot some measurements with REW.


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## warrensomebody

Bought mine years ago...
Digital 33-2055
QC 04A99 TEC


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## TheaterFan

Mine is 33-2055 and teh QC code is 10 A03 TEC. I cannot recall when I bought it, but it has been at least a few years.

Is this thing ok to use with the currently posted calibration file?


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## brucek

Yeah, that's the standard digital meter with a code that wasn't in question....


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## Jerm357

Jerm357 said:


> I look at the graph Ilkka made and it looked like it had about the same drop in the low end that my sub's graph has. And since this response is just about the same as sonnies old analog meter file I decided to install it instead of the new digital file that I was using. Heres a pic of my old measurement with the old analog file installed, Now the measurement has not been adjusted by the calibration file yet but you can see the rolloff is about the same. Im going to take some more measurement tomorrow to see what happends, Im almost getting my hopes up that this might be my problem. What do you guys think of this? Could it be that some of the new digital meters are off like Ilkka's new analog one raying: ? My numbers on my digital meters are 06A05


Quick Update... 

Well, it was not the wrong calibration file like I thought but the Art cleanBox that I was using that was causing the low end roll off. I have since got rid of the cleanBox and am using the digital calibration file like Im supposed to and have got my low end back. :bigsmile:


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