# Radio Shack SPL Meter Correction Values (All new *.cal files are published!)...



## Sonnie

As promised I am calibrating 2 ananlog and 2 digital RS SPL meters. This by no means a professional calibration but it will be better than nothing at all and give us some clues as to what we need do with correction values.

These will be calibrated against my professionally calibrated Behringer ECM8000 mic and a Behringer Euroback UB802 phantom power mic amp.

Pre-impulse response window set to Tukey 0.25
Pre-ref Window Width set to 125ms

Here's the response we will use to calibrate the RS mics against (this is about as flat as I could get it):

ECM with ecm.cal file is on Tab 1(red):











Old Analog Meter (with newrs.cal loaded) on Tab 2 (green):











New Analog Meter 1 (with NO .cal file) on Tab 3 (blue):











New Analog Meter 2 (with NO .cal file) on Tab 4 (magenta):












Digitals coming up soon!


----------



## Guest

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*



> (we'll be giving 3 away!)


Yesssssss!


----------



## Dent

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

Sorry for asking this but what exactly are these graphs showing? I'm not sure what I am looking at. Is it of a sweep measurement with various filters engaged? With the second graph showing the ECM mic and the old analog RS meter with the newrs.cal loaded are these lines supposed to be matched exactly although in the region of 18 Hz and lower they obviously are not so what is that saying?


----------



## Sonnie

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

Here's the digital models...

New Digital Meter 1 (with NO .cal file) on Tab 5 (light blue):

Viewed with ECM:











Viewed with ECM and Analog Meter 2:













New Digital Meter 2 (with NO .cal file) on Tab 6 (magenta again):

Viewed with ECM:











Viewed with ECM and Digital Meter 1:













And FWIW... here are all of the responses together:












Now we need to get some correction values... although these look pretty good compared to the older ones.






.


These RS Meters will NOT be for sale. Instead.... Home Theater Shack is going to give 2 of the analogs and 1 of the digital meters away.

Not only will you get the meters and have the proper .cal file for them... but you will also get a brand spanking new BFD DSP1124P.

Yup :yes: ... you are reading it right! We will giving away 3 new 1124P's with an RS SPL Meter included. Details and an official announcement to follow soon!


And this is just a snippet of what we will be giving away. Stay tuned for the sho-nuff giveaway that we'll be announcing soon! You DO NOT want to miss out on it! :T


Of course there will be qualifications and one is minimum post count!


----------



## Sonnie

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*



Dent said:


> Sorry for asking this but what exactly are these graphs showing? I'm not sure what I am looking at. Is it of a sweep measurement with various filters engaged? With the second graph showing the ECM mic and the old analog RS meter with the newrs.cal loaded are these lines supposed to be matched exactly although in the region of 18 Hz and lower they obviously are not so what is that saying?


What you are looking at are 4 different RS Meters that have no correction files loaded compared against an ECM8000 that has been professionally calibrated. 

The old analog meter has the newrs.cal file correction values loaded in it just for comparision. It's pretty close... close enough. 

We will build a new .cal file for the new meters. More than likely we'll let it be the actual newrs.cal going forward since most people have the new meters instead of the old one.


----------



## Sthrndream

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

I'm having a hard time importing ndm1.mdat to apply the correction values to it. Is there a procedure I'm missing?


----------



## Sonnie

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

Just save it to your harddrive and open it up in REW version 3.29... it should work.


It appears the only significant difference between the new analogs and the new digitals is around 32hz.



I probably should have shown one with the old analog meter and no .cal file so show the difference between the two.


----------



## Sthrndream

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

Yeah, I tried File/Load Measured Data Set and File/Import Measured Data and neither worked. One says it's not 3.29 compatible and the other gives a parsing error.:dontknow:


----------



## Sonnie

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

Hmmm... it's definitely 3.29 Build 321. Try one of the others and let's see if it does the same.


But if you are trying to determine correction values then you probably need to use Excel and then create a .cal file in Notepad.


----------



## Sthrndream

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

That's what I have too. I just wanted to see what the graph looked like with one of your Digital SPL and the .CAL applied. Just to compare with that ECM .

I tried with ndm2.mdat and got the same result. I'll try with IE instead of FireFox maybe...otherwise, no big deal.


----------



## Sthrndream

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

Ok well it's doing the same thing with IE. No worries, probably user error.


----------



## Sonnie

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*



pierrebnh said:


> That's what I have too. I just wanted to see what the graph looked like with one of your Digital SPL and the .CAL applied. Just to compare with that ECM .


You wouldn't be able to do that anyway. You'd have to load the cal file prior to measurement. Unless there's a way to do it that I'm not aware of.

I can tell ya though... If you add the newrs.cal file to any of those RS measurements above.... you get an almost ruler flat response. You'd be right about 80db at 10hz.


----------



## Sonnie

*Re: Calibrating 4 RS SPL Meter mics... (we'll be giving 3 away!)*

Okay, thanks to *brucek*... we have new correction values for the newer analog and the newer digital meters. The old analog meter correction values will not change, however, what model RS Meter you have will determine which correction values you will need.

For the record... from meter to meter of the same model, the measurements are extremely close. brucek took the average of the two meter responses (the average of the two new analog meters and the average of the two new digital meters) and developed corrections values that would correct to an average of the meters. This should keep us very close to the same corrections from meter to meter.

Unfortunately if you have been using the newrs.cal file on one of the newer analgo or digtal meters then your response is NOT correct and you will need to obtain the latest .cal file from the *Downloads* page.


Below are graphs of what the correction values will look like when you load the appropriate .cal file into REW.


New Analog Model #33-4050 = newrsanalog.cal










-----

New Digital Model #33-2055 = newrsdigital.cal










-----

Older Analog Model #33-2050 = oldrsanalog.cal (no change... only the .cal file name changed from newrs.cal to oldrsanalog.cal)











It is apparent from these tests that the newer meters are definitely much more accurate than the older meter.


----------



## Dent

Sonnie,

When you say the new RS digital SPL meter are you saying that there used to be an old RS digital SPL meter? The reason I am asking is because I have had my RS digital SPL meter for a few years now and I believe the model number hasn't changed but I could be wrong.


----------



## Sonnie

I don't know for sure but I think there use to be another one that was an older model #... I'm not positive but I wanted to be safe. If the model # is the same I think you'll be okay.


----------



## Guest

I have an "older" digital meter. It is flat-sided rather than waisted like the new analogs. On the back it says, "Cat No. 33-2055". That is the one still shown in the RS online catalog. So I guess they are the same. 

Anyone have a digital meter with a different catalog number?


----------



## Sonnie

Good question... I just ask you this over at AVS... lol.


----------



## Guest

Geez, I hope I'm not throwing a kink in things here, and this may be old news, but...

According to Michael Fremmer in the June 06 issue of Stereophile:

RadioShack has discontinued its Realistic analog sound-pressure-level meter. Audio Technologies, Inc (ATI) http://www.atiaudio.com has stepped in and bought the rights to it. They improved the response of the built-in electret condenser microphone and now rate it at 32Hz-20Hz, +/-2dB at 114dB.

RG


----------



## Sonnie

It seems there's about 4-5 different companies making these meters, or sticking their names on them. We did post about the ATI meters here in another thread somewhere.

If you'll notice that the corrections above are +/- 2db from about 30-100hz... which would coincide with ATI's response claims. Maybe whoever was building the meter for RS improved it before ATI got a hold of it. Seems that way.


----------



## Guest

This is for the old Radio Shack analog meter (33-2050). I took Sonnie's low frequency data out to 100Hz, Ilkka's mid-frequency data from 110Hz to 660Hz, the old calibration data from 800Hz to 8000Hz and data from a guy named Salas from 10000Hz to 20000Hz (they were similar to Ilkka's data in this range) and merged them. I then did a spline fit and came up with the following set of correction factors:

10 -27.00
11 -24.15
12 -21.91
13 -20.13
14 -18.61
15 -17.33
16 -16.15
17 -14.92
18 -13.85
19 -13.01
20 -12.38
21 -11.66
22 -10.79
23 -10.00
24 -9.33
25 -8.80
26 -8.41
27 -7.99
28 -7.50
29 -6.99
30 -6.50
31 -6.03
32 -5.60
33 -5.23
34 -4.89
35 -4.58
36 -4.29
37 -4.04
38 -3.83
39 -3.64
40 -3.46
41 -3.31
42 -3.16
43 -3.01
44 -2.88
45 -2.74
46 -2.60
47 -2.46
48 -2.35
49 -2.26
50 -2.21
51 -2.18
52 -2.15
53 -2.11
54 -2.04
55 -1.98
56 -1.95
57 -1.92
58 -1.88
59 -1.84
60 -1.80
61 -1.77
62 -1.73
63 -1.71
64 -1.71
65 -1.72
66 -1.70
67 -1.67
68 -1.64
69 -1.60
70 -1.56
71 -1.52
72 -1.47
73 -1.41
74 -1.34
75 -1.26
76 -1.19
77 -1.12
78 -1.07
79 -1.02
80 -0.98
81 -0.94
82 -0.89
83 -0.85
84 -0.80
85 -0.75
86 -0.71
87 -0.66
88 -0.62
89 -0.59
90 -0.55
91 -0.52
92 -0.50
93 -0.47
94 -0.43
95 -0.40
96 -0.36
97 -0.34
98 -0.32
99 -0.30
100 -0.27
110 -0.21
120 -0.19
130 -0.16
140 -0.13
150 -0.10
160 -0.08
170 -0.07
180 -0.05
190 -0.04
200 -0.03
210 -0.02
220 -0.01
230 0.00
240 0.00
250 0.01
260 0.01
270 0.02
280 0.02
290 0.02
300 0.02
310 0.02
320 0.02
330 0.01
340 0.01
350 0.01
360 0.01
370 0.00
380 0.00
390 0.00
400 -0.01
410 -0.01
420 -0.01
430 -0.01
440 -0.01
450 -0.01
460 -0.01
470 -0.01
480 -0.01
490 -0.01
500 -0.01
510 0.00
520 0.00
530 0.01
540 0.02
550 0.02
560 0.03
570 0.03
580 0.04
590 0.04
600 0.05
610 0.05
620 0.06
630 0.06
640 0.07
650 0.07
660 0.08
670 0.08
680 0.08
690 0.08
700 0.07
710 0.07
720 0.06
730 0.06
740 0.05
750 0.04
760 0.03
770 0.02
780 0.01
790 0.01
800 0.00
810 -0.01
820 -0.01
830 -0.01
840 -0.02
850 -0.02
860 -0.02
870 -0.02
880 -0.02
890 -0.02
900 -0.02
910 -0.02
920 -0.02
930 -0.01
940 -0.01
950 -0.01
960 -0.01
970 -0.01
980 0.00
990 0.00
1000 0.00
1100 0.01
1200 0.00
1300 0.00
1400 0.02
1500 0.04
1600 0.08
1700 0.13
1800 0.19
1900 0.26
2000 0.34
2100 0.42
2200 0.51
2300 0.60
2400 0.70
2500 0.81
2600 0.91
2700 1.02
2800 1.13
2900 1.24
3000 1.34
3100 1.45
3200 1.55
3300 1.65
3400 1.74
3500 1.83
3600 1.92
3700 2.01
3800 2.09
3900 2.16
4000 2.24
4100 2.31
4200 2.37
4300 2.43
4400 2.49
4500 2.55
4600 2.60
4700 2.65
4800 2.69
4900 2.73
5000 2.76
5100 2.80
5200 2.83
5300 2.85
5400 2.87
5500 2.89
5600 2.90
5700 2.91
5800 2.91
5900 2.92
6000 2.91
6100 2.91
6200 2.90
6300 2.88
6400 2.86
6500 2.84
6600 2.81
6700 2.78
6800 2.75
6900 2.71
7000 2.66
7100 2.62
7200 2.56
7300 2.51
7400 2.45
7500 2.38
7600 2.32
7700 2.24
7800 2.17
7900 2.09
8000 2.00
8100 1.91
8200 1.82
8300 1.72
8400 1.62
8500 1.51
8600 1.40
8700 1.29
8800 1.18
8900 1.07
9000 0.95
9100 0.83
9200 0.71
9300 0.58
9400 0.46
9500 0.33
9600 0.21
9700 0.08
9800 -0.05
9900 -0.17
10000 -0.30
11000 -1.50
12000 -2.50
13000 -3.51
14000 -4.60
15000 -5.74
16000 -6.93
17000 -8.16
18000 -9.43
19000 -10.71
20000 -12.00

Can someone who took data with this meter and a calibrated microphone through the entire spectrum verify if this is close?


----------



## Sonnie

I don't know of anyone who has calibrated the entire frequency range on this meter. I never could get a flat enough response to compare it.


----------



## Ilkka

Sonnie said:


> I don't know of anyone who has calibrated the entire frequency range on this meter. I never could get a flat enough response to do compare it.


I could do it, but still it would be good only for my meter. RS meters aren't good above ~500 Hz and the variances between two meters can be large. You (not you Sonnie  ) need to buy a better mic if you want accurate full range measurements.


----------



## Guest

Hi,

I know that this is an old thread but I was wondering if anyone has ever evaluated the RS meter's dB response vs. Actual dB level. In other words, how accurate is the digital RS meter over the rated sound pressure spectrum of 50-120 dB? 

The reason I ask: In setting up REW 4 with a ECM 8000 (via audio buddy pre-amp into my Mac's vanilla sound card) I was "calibrating" the REW dB meter value to the RS digital meter which I own. When I measured the REW white noise with RS meter it was 82 dB so I set the REW meter to read 82. I then stopped the white noise from REW. In my house the heater was going and I could audibly hear it. The REW meter stated 65 dB as the background noise from the heater (which I could believe since the thing is pretty loud). However, the RS meter would not register any signal at all (both A and C weighting, fast/slow response etc.). Yes, I set the RS meter to 60 dB so it should pick up any background noise over 50 dB. I was also placing the RS meter at the same location as the ECM mic. 

Sooooo.... Just how accurate (linear) is this RS digital meter over the entire sound pressure range from 50-120 dB? Is the ECM8000/REW/computer more accurate for a dB meter? Is there something funky going on with my Mac's input level where it boosts low-levels? 

Thanks much,

Mace


----------



## Ilkka

The RS meter is reasonably linear within its operating range. The REW/ECM8000 combo picks up that heater noise because its frequency response isn't weighted (though mic's FR isn't flat all the way down to DC). The RS is always at least C-weighted, so it doesn't respond to low-level low frequency sounds as well as unweighted meter/mic.


----------



## brucek

The ECM8000 is a full range flat microphone. It does require a small amount of calibration, but basically it's a flat microphone. At 20Hz it will pick up a flat level. The RS meter is a C-Weighted meter, it's down the C-Weight at 20hz, hardly comparable to the ECM....... I have no idea what the frequency of your 'heater' is, but it's likely a low frequency.

brucek


----------



## Guest

Ilkka said:


> The RS meter is reasonably linear within its operating range. The REW/ECM8000 combo picks up that heater noise because its frequency response isn't weighted (though mic's FR isn't flat all the way down to DC). The RS is always at least C-weighted, so it doesn't respond to low-level low frequency sounds as well as unweighted meter/mic.


Thanks for the info! So, if I now understand this correctly... the "C-weighting" means that the response curve at a given sound pressure is not flat* and *that if frequency is held constant and the sound pressure changed the measured dB level will not be "linear". 

Thanks,

Mace


----------



## brucek

> if frequency is held constant and the sound pressure changed the measured dB level will not be "linear".


No. If the sound pressure level is held constant and the frequency is changed, the measured SPL level will not be linear.

The C-Weight meter will measure on a C-Weighted curve as shown below. That's the FR of the meter.

REW applies the inverse of this curve to any readings from a C-Weight microphone (if it tracked a perfect C-Weight). The resulting graph would then be equivalent to a flat response meter.

A flat response microphone simply measures flat...









brucek


----------



## SteveCallas

Just thought I'd chime in. I went a step beyond Sonnie's RS meter calibration files by plugging my port and taking a close mic FR sweep of the driver with the meter a couple inches from the center, resting on a blanket I folded several times on the baseplate. I then modeled my driver as a sealed sub with the same volume and adjusted power in the simulation until it generally matched the average output level I was seeing from an initial sweep. With the mic stationary, I then painstakingly tweaked the calibration file and took sweep after sweep until the sealed close mic response I was seeing closely matched the predicted response :wits-end: Ilkka can correct me if I'm wrong, but if someone is willing to spend the time, this seems like a decent way to end up with a relatively accurate calibration file.


----------



## Ilkka

SteveCallas said:


> Just thought I'd chime in. I went a step beyond Sonnie's RS meter calibration files by plugging my port and taking a close mic FR sweep of the driver with the meter a couple inches from the center, resting on a blanket I folded several times on the baseplate. I then modeled my driver as a sealed sub with the same volume and adjusted power in the simulation until it generally matched the average output level I was seeing from an initial sweep. With the mic stationary, I then painstakingly tweaked the calibration file and took sweep after sweep until the sealed close mic response I was seeing closely matched the predicted response :wits-end: Ilkka can correct me if I'm wrong, but if someone is willing to spend the time, this seems like a decent way to end up with a relatively accurate calibration file.


I have to say that I wouldn't recommend this method. Assuming that a simple small signal simulation (especially if using WinISD) would match perfectly with a real world frequency response is not wise or accurate. A reference microphone having a known frequency response is a much better method for calibrating your RS (or any other mic).

Although I would be interested to see the cal file resulting from using such method? Can you post it?


----------



## SteveCallas

Yeah. 

10	-15.90
11	-14.75
12	-13.60
13	-12.45
14	-11.30
15	-10.20
16	-9.10
17	-8.05
18	-7.00
19	-6.00
20	-5.00
21	-4.25
22	-3.65
23	-3.15
24	-2.55
25	-2.05
26	-1.80
27	-1.60
28	-1.40
29	-1.20
30	-1.00
31	-0.80
32	-0.60
33	-0.44
34	-0.33
35	-0.22
36	-0.11
37	0.04
38	0.13
39	0.25
40	0.35
41	0.40
42	0.45
43	0.55
44	0.60
45	0.45
46	0.25
47	0.05
48	-0.15
49	-0.15
50	-0.15
51	-0.08
52	-0.03
53	0.00
54	0.04
55	0.10
56	0.19
57	0.30
58	0.46
59	0.54
60	0.50
61	0.48
62	0.44
63	0.41
64	0.39
65	0.37
66	0.36
67	0.34
68	0.30
69	0.28
70	0.27
71	0.30
72	0.32
73	0.34
74	0.34
75	0.35
76	0.36
77	0.12
78	0.00
79	-0.03
80	-0.06
81	-0.09
82	-0.12
83	-0.09
84	-0.06
85	-0.03
86	0.00
87	0.00
88	0.05
89	0.15
90	0.20
91	0.25
92	0.30
93	0.35
94	0.40
95	0.44
96	0.49
97	0.50
98	0.50
99	0.50
100	0.50

Next time I head up to Purdue I can reference this against an ECM mic.


----------



## Ilkka

You had the digital version?


----------



## SteveCallas

Yeah. Do you recall your free air measurement of the TC 2000? I believe it rolled off at 8db per octave, and in WinISD, it's just about 8db per octave in 1000 cubic feet.


----------



## Ilkka

SteveCallas said:


> Yeah. Do you recall your free air measurement of the TC 2000? I believe it rolled off at 8db per octave, and in WinISD, it's just about 8db per octave in 1000 cubic feet.


Around 9 dB/oct, but it's not the sub-Fc area that I'm worried about. It's just that most simulations (all WinISD) don't take the varying Le into consideration. Even Unibox's model doesn't correlate that well with my free air measurements (even when Le is given in the three number form).


----------



## brucek

> correct me if I'm wrong, but if someone is willing to spend the time, this seems like a decent way to end up with a relatively accurate calibration file


What an enormous leap of faith you've taken in assuming your real world sub matches a computer simulation. 

You've simply modelled your meter to your computer program, not to its actual calibration. 

I suppose your assumption is no worse than expecting all el-cheapo Radio Shack meters to measure consistent among themselves, but I would still recommend using Sonnies cal file until you got an ECM or Galaxy meter.

In addition to a lot of reasons your method is flawed, I have to add that measuring an inch away from a driver results in some varied results. Sonnie found this when he was testing all the Galaxies. If he measured very close, a resonance was set up (of some sort) if the mic was an inch or so away - it may have been as simple as wind noise from the driver. A foot worked better producing more consistent results.

You'll also find that microphone responses tend not to jump around quickly (note your dips at 50Hz & 80Hz). These are just measurement anomalies. These types of readings are generally ignored and then extrapolated results substituted instead.









brucek


----------



## SteveCallas

Well again, next time I pay a friend a visit at Purdue I will calibrate my meter to his Behringer mic. Using the digital corrections from this thread, the close mic sealed response rolloff would be more than 20db/octave.


----------



## SteveCallas

Measured my Yamaha receiver today - sub out surprisingly doesn't start rolling off until 3.5hz and is 3db down at 2hz :rubeyes: So that's not an issue. Don't have a way to measure the amp, but I have no reason to not believe the specs and it being pretty flat to 10hz. So here is the close mic and 1.5' away sealed responses using the newdigital corrections - the rolloff is way too sharp, ~20db/octave in 650 effective liters. If not the amp, it's gotta be the RS meter, and that doesn't seem far fetched.


----------



## brucek

> it's gotta be the RS meter,


Why not buy a better mic like the ECM or galaxy? It's not that expensive and is something you'll have for a long time.

brucek


----------



## SteveCallas

Personally speaking, I can think of several things I'd rather spend the money on and I can calibrate my specific RS meter to a Behringer mic in the not too distant future. I don't worry much about it.


----------



## SteveCallas

brucek and Ilkka, I'll be if the new RS digital calibration file based on Sonnie's professionally calibrated Behringer mic isn't virtually identical to what I made <20hz a few posts up by using a sealed close mic and comparing it to simulation :T


----------



## krunk

Can you tell me if the cal file for the EMC8000 from the download page is better than the other cal file that's also available on this forum? (http://www.hometheatershack.com/forums/bfd-rew-forum/314-professional-mic-calibration.html)


----------



## brucek

> I'll be if the new RS digital calibration file based on Sonnie's professionally calibrated Behringer mic isn't virtually identical to what I made <20hz a few posts up by using a sealed close mic and comparing it to simulation


Yeah, not bad. I'd probably go with the new one though... it goes to 7Hz..










brucek


----------



## brucek

> is better than the other cal file


We believe so.... for Sonnies microphone anyway.

It depends on how consistent the mic elements are across different ECM8000's... who knows..

brucek


----------



## Exocer

I wouldn't mind ordering an ECM8000 for Sonnie to measure against his own (assuming his hasn't already been professionally calibrated?) to get a somewhat better understanding of how consistent these microphones are.


----------



## Sonnie

As far as consistency it will not matter if my ECM has been professionally calibrated. I have only mentioned it to a couple of others, but I've actually ordered another ECM8000 and it should be here tomorrow. We will find out a little about consistency very soon.


----------



## Sonnie

Apparently all ECM8000's are not created equal, but they are probably all close...


----------



## krunk

Where can I buy a calibrated EMC8000?


----------



## brucek

> Where can I buy a calibrated EMC8000?


You have to buy one and send it to be calibrated.....

or you can use our ecm calibration file and assume it's close enough for home use... it's certainly close enough to use for equalization of room peaks with REW.

brucek


----------



## krunk

I live in the Netherlands. Sending it over will cost some more money then order a calibrated one directly. I can calibrate the old mic with the new one and sell it.


----------



## Exocer

Sonnie said:


> As far as consistency it will not matter if my ECM has been professionally calibrated. I have only mentioned it to a couple of others, but I've actually ordered another ECM8000 and it should be here tomorrow. We will find out a little about consistency very soon.


Thanks for clearing up the consistency issue 

My point was to measure with two (or more) uncalibrated ECM8000s. A calibrated ECM would definitely measure different than a non-calibrated ECM (in the lower frequencies) so it wouldn't make sense to compare the measurements of calibrated and uncalibrated ECM to get an idea of consistency unless there were another uncalibrated unit there as well. Just my train of thought on the issue. Maybe I am misunderstanding something.


----------



## brucek

> A calibrated ECM would definitely measure different than a non-calibrated ECM (in the lower frequencies) so it wouldn't make sense to compare the measurements of calibrated and uncalibrated ECM to get an idea of consistency


The calibration comes in the form of a calibration file that Sonnie would have loaded for both ECM8000's he tested.

brucek


----------



## Sonnie

Yeah... that's correct. I could test them both uncalibrated or both calibrated. It's easier to see the response on the graph (as we normally view and post) when using the calibration file on both.


----------



## krunk

brucek said:


> We believe so.... for Sonnies microphone anyway.
> 
> It depends on how consistent the mic elements are across different ECM8000's... who knows..
> 
> brucek


These are both Sonnies calibration files. Quite a difference, not?
I think they aren't very consistent.


----------



## brucek

> I think they aren't very consistent.


You're a bit confused. Those are the *same* microphone calibrated by two different companies using two different methods. 
Let's just say the last calibration that was carried out is very, very accurate.

brucek


----------



## krunk

Ok, that's clear. Sorry :nerd:
Im surprised by the difference between them. I also use this mic when I measure my DIY speakers. The upper frequencies are way different. :mooooh: 

What to use as reference.. :scratch:


----------



## Exocer

Ah, ok thanks for clearing that up... I was under the impression that professionally calibrated mics were permanently modified somehow to measure accurately without the use of a calibration file. :coocoo:


----------



## Guest

I just bought the digital RS sound meter, and I plan to use it with REW.
I went to download page to grab the correction cal file for it however I see the numbers are off compared to the comparison graph at the beginning of this thread.

For example:
In the donwload page the correction for digital RS at 20HZ is -6.56 where based on the graph at post#1 it should be around -2.

I also found some some posts at AVSFORUM related to this that has a calibrated file with the values closer to the graph at post#1 here (the value is -2.50, I believe the values are from Sonnie P and Bruce K, posted by DMF).

The link to the avsforum
www.avsforum.com/avs-vb/showthread.php?t=505236&page=3


At 20Hz for digital RS the correction:
the hometheathershack download page has -6.56
vs.
AVSFORUM result posted by DMF, Sonnie P and Bruce at -2.50


at post number 140 of the thread in avsforum it has the download link to the corrections that user 'DMF" posted earlier.

So I am confused on which one to use. (I think the one in AVSFORUM is more in sync with the graph in the post#1 at the beginning of this thread).

Sonnie, Bruce, please help.

Thank you.


----------



## brucek

> I see the numbers are off compared to the comparison graph at the beginning of this thread.


Sonnie had his ECM8000 calibrated by a professional company (West Caldwell Calibration Laboratories Inc) in 2007, and subsequent to that we redid all the cal files to compare against it. Sorry for the confusion. Just use the files on the download page and ignore 2006 posts showing old cal files.

brucek


----------



## Guest

Thanks for the clarification Bruce.


----------



## Sonnie

Maybe we should get someone to make a post stating those numbers are no longer considered accurate and more accurate corrections can be found here. :huh:


----------



## marcosreg

Do you think all new analog RS SPL meters have the same errors?
Marcos


----------



## brucek

I think they're fairly consistent.........


----------



## atledreier

Just make sure you use the file for the right model of meter. The difference between my Old-old analog and my old analog is pretty big.


----------

