Does anyone else think that perhaps a sticky linking users to correction tables for the Radio Shack SPL meter might be helpful? For example:

http://forum.audiogon.com/cgi-bin/fr.pl?htech&983682086&openflup&1&4

http://www.danmarx.org/audioinnovation/rsmeter.html

http://www.gti.net/wallin/audio/rsmeter/33-2055/33-2055.html

http://www.etfacoustic.com/Software/RSAnalogueSPL.zip

http://www.audioc.com/library1/testcd/testcd.htm

http://www.hometheatershack.com/forums/rew-forum/86-interesting-info-rs-spl-meter-correction-values.html

http://www.audioxpress.com/magsdirx/ax/addenda/media/koya2811.pdf

http://www.svsound.com/questions-faqs-rscomp.cfm

I don't think a lot of people know about the correction factors so making it a sticky would be a good idea. SVS has a page on it, too:

http://www.svsound.com/questions-faqs-rscomp.cfm

Yea sounds good. Correct information is good :)

That qti.net link is very interesting. I had assumed that it was the mic that gave the meter its lousy response (lousy as far as calibrated mics go). Turns out it's mostly the electronics.

Still, so long as we compensate for the deficiencies, it's good enough for our uses in audio.

Note also that the 'Quick Tip' on the danmark.com web page refers to measuring loudspeaker response, NOT something that the typical audiophile uses his meter for. So ignore the Tip. When calibrating speaker levels or checking room response, the meter goes as close to your head in the primary listening position as you can get it. Point it up. It mounts on a standard camera tripod which makes the process a lot easier.

Last week, I received a test CD from Rives Audio. It has 2 sets of 1/3 octave test tones recorded from 20 Hz to 20 kHz. One set is the standard set of test tones and the second set is "corrected" for the Radio Shack meter. I used the RS corrected tones to measure my system, and I got some confusing results. I then had the following e-mail exchange with "technical support" at Rives Audio:

"My center channel speaker appears to have severely reduced output above 10kHz, (down ~25 dB compared to the 80 dB reference). I moved one of my mains in front of the CC and hooked it to the CC cable. It too has limited output above 10 kHz, but not quite as severe, (down ~20 dB). However, it was also about 2 feet closer to the meter, which may explain the difference."

Response fro Rives Audio:

"Above 10k, the RS meter is not terribly reliable. I would not be too concerned with measurements above 10k."

Reply from me:

"The Test CD is billed as having a set of tracks that are specifically corrected for the Radio Shack SPL meter. If the Radio Shack meter is really that unreliable above 10k, maybe you should delete tracks 59, 60 and 61, and instead include an explanation that the meter is too unreliable to correct at those frequencies. It would keep people, (like me) from freaking out thinking that a tweeter is blown."

Response from Rives Audio:

"That's a reasonable idea, but people would then freak out and buy other Test CD's that had the full bandwidth."


According to the charts in the links in the original post, the RS meter is within +/- 1 dB from 10k to 20 kHz. So, who's right? I'm thinking that my meter is damaged. I sure HOPE its not my speakers!

Thoughts?

Craig

In the qti.net link the author refers to the digital meter being -3dB at 12 KHz, yet notes that the analog meter is better up top. -25 dB cannot be explained by meter foibles.

I think you should test it in free air - outside - at 1m and then (assuming the same result) worry about your electronics. If both speakers do it, it's not a blown tweeter.

Btw, since this is a sticky thread now, we should continue this elsewhere.

Here's a free Excel spreadsheet with the comp values that you can download. Makes it quicker than doing by hand. Also a PDF version for those without Excel:

http://www.audioc.com/library1/testcd/testcd.htm

When calibrating your Sub with SPL meter, Is it best to use the SPL in your primary seating location and point the SPL meter towards your sub?

OR is it better to measure with the SPL meter closer to the sub (if so, how close should you be to the sub?)

Thx,
Claude

Claude,

I've always heard to place it in the exact location that your ears would be in your primary setaing position, angled slightly forward.. maybe 20 to 30 degrees down from the ceiling towards the front of your room. Some people point it directly at the front of the room... others use 45 degrees.

Regs,
Jeff

Here's a somewhat more anal version of the table, courtesy of Ilkka and apparently appropriate to TrueRTA:

10 -14.33259693
10.59463094 -13.52968703
11.22462048 -12.74595335
11.89207115 -11.98268094
12.5992105 -11.24113838
13.34839854 -10.52255777
14.14213562 -9.828113197
14.98307077 -9.158898305
15.87401052 -8.515903684
16.81792831 -7.899994991
17.81797436 -7.311892737
18.87748625 -6.752154684
20 -6.221161728
21.18926189 -5.719108023
22.44924097 -5.24599587
23.7841423 -4.801635653
25.198421 -4.38565084
26.69679708 -3.997487754
28.28427125 -3.6364296
29.96614154 -3.30161399
31.74802104 -2.992053117
33.63585661 -2.706655603
35.63594873 -2.444249093
37.75497251 -2.203602722
40 -1.983448665
42.37852377 -1.782502185
44.89848193 -1.599479687
47.5682846 -1.43311451
50.396842 -1.282170279
53.39359417 -1.145451828
56.56854249 -1.021813749
59.93228308 -0.910166743
63.49604208 -0.809481987
67.27171322 -0.718793751
71.27189745 -0.63720053
75.50994501 -0.563864932
80 -0.498012574
84.75704755 -0.438930194
89.79696386 -0.385963182
95.1365692 -0.338512687
100.793684 -0.296032457
106.7871883 -0.258025523
113.137085 -0.224040813
119.8645662 -0.193669799
126.9920842 -0.1665432
134.5434264 -0.142327811
142.5437949 -0.12072348
151.01989 -0.101460247
160 -0.08429567
515.625 0.000 0.000
539.063 0.015 0.181
562.500 0.029 0.364
585.938 0.041 0.544
609.375 0.052 0.739
632.813 0.063 0.949
656.250 0.076 1.187
679.688 0.091 1.444
703.125 0.111 1.711
726.563 0.135 1.978
750.000 0.162 2.237
773.438 0.191 2.488
796.875 0.222 2.729
820.313 0.255 2.962
843.750 0.288 3.187
867.188 0.322 3.408
890.625 0.357 3.625
914.063 0.392 3.839
937.500 0.428 4.051
960.938 0.465 4.265
984.375 0.503 4.474
1007.813 0.541 4.682
1031.250 0.580 4.888
1054.688 0.619 5.088
1078.125 0.660 5.293
1101.563 0.700 5.492
1125.000 0.741 5.687
1148.438 0.781 5.880
1171.875 0.818 6.069
1195.313 0.857 6.259
1218.750 0.893 6.451
1242.188 0.931 6.646
1265.625 0.968 6.841
1289.063 1.008 7.039
1312.500 1.049 7.236
1335.938 1.091 7.433
1359.375 1.134 7.633
1382.813 1.179 7.830
1406.250 1.224 8.031
1429.688 1.272 8.221
1453.125 1.322 8.409
1476.563 1.376 8.581
1500.000 1.433 8.724
1523.438 1.491 8.832
1546.875 1.547 8.900
1570.313 1.599 8.938
1593.750 1.648 8.947
1617.188 1.693 8.938
1640.625 1.733 8.920
1664.063 1.770 8.906
1687.500 1.804 8.900
1710.938 1.837 8.902
1734.375 1.868 8.910
1757.813 1.900 8.920
1781.250 1.931 8.935
1804.688 1.961 8.947
1828.125 1.990 8.952
1851.563 2.020 8.959
1875.000 2.049 8.964
1898.438 2.076 8.963
1921.875 2.102 8.967
1945.313 2.128 8.969
1968.750 2.152 8.976
1992.188 2.177 8.987
2015.625 2.203 8.996
2039.063 2.227 9.005
2062.500 2.250 9.012
2085.938 2.275 9.017
2109.375 2.301 9.020
2132.813 2.327 9.017
2156.250 2.351 9.012
2179.688 2.374 9.004
2203.125 2.395 8.999
2226.563 2.415 8.991
2250.000 2.435 8.987
2273.438 2.453 8.985
2296.875 2.471 8.978
2320.313 2.489 8.973
2343.750 2.505 8.962
2367.188 2.519 8.962
2390.625 2.532 8.963
2414.063 2.543 8.980
2437.500 2.555 9.013
2460.938 2.568 9.070
2484.375 2.586 9.136
2507.813 2.608 9.198
2531.250 2.633 9.246
2554.688 2.659 9.280
2578.125 2.683 9.299
2601.563 2.706 9.307
2625.000 2.728 9.305
2648.438 2.749 9.295
2671.875 2.770 9.280
2695.313 2.788 9.261
2718.750 2.806 9.238
3164.063 2.938 9.082
3187.500 2.935 9.122
3210.938 2.932 9.173
3234.375 2.929 9.248
3257.813 2.926 9.333
3281.250 2.926 9.432
3304.688 2.928 9.535
3328.125 2.931 9.637
3351.563 2.936 9.743
3375.000 2.941 9.846
3398.438 2.947 9.948
3421.875 2.953 10.045
3445.313 2.958 10.146
3468.750 2.962 10.243
3492.188 2.968 10.345
3515.625 2.975 10.449
3539.063 2.982 10.557
3562.500 2.990 10.671
3585.938 2.998 10.789
3609.375 3.006 10.916
3632.813 3.015 11.053
3656.250 3.025 11.199
3679.688 3.039 11.354
3703.125 3.055 11.520
3726.563 3.074 11.682
3750.000 3.095 11.837
3773.438 3.118 11.983
3796.875 3.142 12.112
3820.313 3.167 12.230
3843.750 3.192 12.331
3867.188 3.217 12.422
3890.625 3.243 12.502
3914.063 3.270 12.578
3937.500 3.297 12.648
3960.938 3.325 12.710
3984.375 3.352 12.766
4007.813 3.379 12.815
4031.250 3.406 12.855
4054.688 3.433 12.890
4078.125 3.461 12.912
4101.563 3.488 12.930
4125.000 3.514 12.938
4148.438 3.540 12.939
4171.875 3.565 12.929
4195.313 3.591 12.915
4218.750 3.616 12.892
4242.188 3.640 12.863
4265.625 3.664 12.828
4289.063 3.686 12.780
4312.500 3.706 12.725
4335.938 3.724 12.661
4359.375 3.740 12.599
4382.813 3.753 12.535
4406.250 3.764 12.483
4429.688 3.772 12.440
4453.125 3.781 12.409
4476.563 3.788 12.392
4500.000 3.795 12.383
4523.438 3.804 12.391
4546.875 3.812 12.404
4570.313 3.820 12.427
4593.750 3.829 12.456
4617.188 3.838 12.492
4640.625 3.849 12.533
4664.063 3.860 12.585
4687.500 3.872 12.651
4710.938 3.885 12.729
4734.375 3.901 12.822
4757.813 3.919 12.924
4781.250 3.938 13.032
4804.688 3.961 13.143
4828.125 3.986 13.258
4851.563 4.013 13.369
4875.000 4.043 13.476
4898.438 4.076 13.576
4921.875 4.112 13.664
4945.313 4.150 13.741
4968.750 4.190 13.803
4992.188 4.230 13.850
5015.625 4.269 13.883
5039.063 4.309 13.900
5062.500 4.350 13.906
5085.938 4.391 13.904
5109.375 4.432 13.895
5132.813 4.471 13.885
5156.250 4.510 13.873
5179.688 4.550 13.870
5203.125 4.592 13.879
5226.563 4.638 13.894
5250.000 4.687 13.913
5273.438 4.742 13.923
5296.875 4.802 13.913
5320.313 4.866 13.871
5343.750 4.933 13.790
5367.188 5.002 13.667
5390.625 5.071 13.501
5414.063 5.141 13.288
5437.500 5.211 13.035
5460.938 5.280 12.732
5484.375 5.347 12.388
5507.813 5.413 11.997
5531.250 5.472 11.564
5554.688 5.525 11.091
5578.125 5.570 10.586
5601.563 5.606 10.061
5625.000 5.635 9.528
5648.438 5.655 8.999
5671.875 5.670 8.481
5695.313 5.680 7.985
5718.750 5.684 7.507
5742.188 5.686 7.050
5765.625 5.685 6.613
5789.063 5.681 6.190
5812.500 5.675 5.783
5835.938 5.666 5.395
5859.375 5.653 5.024
5882.813 5.638 4.674
5906.250 5.622 4.345
5929.688 5.607 4.037
5953.125 5.595 3.750
5976.563 5.584 3.484
6000.000 5.574 3.229
6023.438 5.565 2.986
6046.875 5.557 2.748
6070.313 5.552 2.508
6093.750 5.548 2.264
6117.188 5.544 2.005
6140.625 5.540 1.731
6164.063 5.536 1.443
6187.500 5.530 1.145
6210.938 5.521 0.846
6234.375 5.509 0.551
6257.813 5.496 0.265
6281.250 5.480 -0.010
6304.688 5.464 -0.274
6328.125 5.448 -0.526
6351.563 5.430 -0.767
6375.000 5.412 -0.999
6398.438 5.393 -1.222
6421.875 5.375 -1.437
6445.313 5.359 -1.643
6468.750 5.344 -1.845
6492.188 5.332 -2.041
6515.625 5.322 -2.237
6539.063 5.316 -2.442
6562.500 5.310 -2.658
6726.563 5.246 -4.667
6820.313 5.171 -5.937
6843.750 5.152 -6.257
6867.188 5.130 -6.583
6890.625 5.105 -6.919
6914.063 5.077 -7.264
6937.500 5.048 -7.617
6960.938 5.018 -7.980
6984.375 4.985 -8.350
7007.813 4.950 -8.725
7031.250 4.910 -9.102
7054.688 4.867 -9.478
7078.125 4.820 -9.848
7101.563 4.769 -10.206
7125.000 4.713 -10.548
7148.438 4.652 -10.870
7171.875 4.589 -11.169
7195.313 4.523 -11.442
7218.750 4.454 -11.689
7242.188 4.384 -11.906
7265.625 4.313 -12.093
7289.063 4.241 -12.249
7312.500 4.168 -12.371
7335.938 4.097 -12.459
7359.375 4.026 -12.513
7382.813 3.958 -12.537
7406.250 3.892 -12.530
7429.688 3.830 -12.501
7453.125 3.772 -12.453
7476.563 3.718 -12.393
7500.000 3.668 -12.324
7523.438 3.620 -12.246
7546.875 3.575 -12.166
7570.313 3.533 -12.081
7593.750 3.495 -11.994
7617.188 3.460 -11.907
7640.625 3.428 -11.825
7664.063 3.400 -11.753
7687.500 3.374 -11.696
7710.938 3.351 -11.656
7734.375 3.329 -11.637
7757.813 3.307 -11.637
7781.250 3.283 -11.656
7804.688 3.260 -11.689
7828.125 3.234 -11.731
7851.563 3.207 -11.776
7875.000 3.178 -11.819
7898.438 3.146 -11.854
7921.875 3.113 -11.875
7945.313 3.080 -11.881
7968.750 3.047 -11.872
7992.188 3.016 -11.847
8015.625 2.988 -11.812
8039.063 2.964 -11.771
8062.500 2.943 -11.732
8085.938 2.927 -11.699
8109.375 2.914 -11.679
8132.813 2.905 -11.679
8156.250 2.897 -11.701
8179.688 2.891 -11.750
8203.125 2.885 -11.826
8226.563 2.878 -11.933
8250.000 2.870 -12.070
8273.438 2.860 -12.238
8296.875 2.848 -12.434
8320.313 2.830 -12.654
8343.750 2.808 -12.896
8367.188 2.780 -13.146
8390.625 2.746 -13.399
8414.063 2.706 -13.645
8437.500 2.661 -13.875
8460.938 2.611 -14.087
8484.375 2.557 -14.275
8507.813 2.500 -14.438
8531.250 2.442 -14.573
8554.688 2.381 -14.678
8578.125 2.319 -14.750
8601.563 2.256 -14.787
8625.000 2.192 -14.787
8648.438 2.129 -14.751
8671.875 2.068 -14.680
8695.313 2.012 -14.579
8718.750 1.959 -14.452
8742.188 1.912 -14.310
8765.625 1.871 -14.156
8789.063 1.834 -13.998
8812.500 1.803 -13.841
8835.938 1.775 -13.691
8859.375 1.751 -13.550
8882.813 1.730 -13.423
8906.250 1.712 -13.312
8929.688 1.697 -13.219
8953.125 1.683 -13.144
9375.000 1.294 -13.518
9398.438 1.280 -13.492
9421.875 1.270 -13.481
9445.313 1.262 -13.489
9468.750 1.255 -13.518
9492.188 1.248 -13.568
9515.625 1.241 -13.640
9539.063 1.233 -13.732
9562.500 1.225 -13.841
9585.938 1.215 -13.965
9609.375 1.203 -14.101
9632.813 1.188 -14.245
9656.250 1.171 -14.395
9679.688 1.152 -14.546
9703.125 1.131 -14.698
9726.563 1.109 -14.851
9750.000 1.088 -15.008
9773.438 1.066 -15.168
9796.875 1.043 -15.335
9820.313 1.018 -15.510
9843.750 0.989 -15.692
9867.188 0.958 -15.877
9890.625 0.922 -16.059
9914.063 0.883 -16.234
9937.500 0.841 -16.390
9960.938 0.796 -16.520
9984.375 0.748 -16.619
10007.810 0.700 -16.684
10031.250 0.653 -16.714
10054.690 0.608 -16.712
10078.130 0.567 -16.684
10101.560 0.530 -16.639
10125.000 0.499 -16.593
10148.440 0.472 -16.560
10171.880 0.449 -16.552
10195.310 0.427 -16.576
10218.750 0.405 -16.628
10242.190 0.382 -16.706
10265.630 0.359 -16.801
10289.060 0.333 -16.910
10312.500 0.305 -17.028
10335.940 0.275 -17.154
10359.380 0.243 -17.281
10382.810 0.208 -17.411
10406.250 0.173 -17.540
10429.690 0.136 -17.670
10453.130 0.099 -17.798
10476.560 0.061 -17.926
10500.000 0.023 -18.060
10523.440 -0.015 -18.194
10546.880 -0.055 -18.333
10570.310 -0.095 -18.478
10593.750 -0.137 -18.629
10617.190 -0.180 -18.784
10640.630 -0.225 -18.942
10664.060 -0.273 -19.098
10687.500 -0.323 -19.252
10710.940 -0.376 -19.397
10734.380 -0.429 -19.529
10757.810 -0.482 -19.643
10781.250 -0.535 -19.741
10804.690 -0.586 -19.826
10828.130 -0.635 -19.905
10851.560 -0.684 -19.977
10875.000 -0.731 -20.056
10898.440 -0.777 -20.146
10921.880 -0.823 -20.253
10945.310 -0.867 -20.375
10968.750 -0.914 -20.511
10992.190 -0.961 -20.662
11015.630 -1.012 -20.817
11039.060 -1.066 -20.976
11226.560 -1.592 -21.844
11250.000 -1.664 -21.887
11273.440 -1.737 -21.919
11296.880 -1.810 -21.945
11320.310 -1.883 -21.962
11343.750 -1.957 -21.974
11367.190 -2.034 -21.980
11390.630 -2.113 -21.977
11414.060 -2.194 -21.958
11437.500 -2.278 -21.920
11460.940 -2.362 -21.855
11484.380 -2.448 -21.758
11507.810 -2.533 -21.630
11531.250 -2.616 -21.462
11554.690 -2.696 -21.261
11578.130 -2.773 -21.031
11601.560 -2.845 -20.780
11625.000 -2.911 -20.517
11648.440 -2.971 -20.251
11671.880 -3.026 -19.986
11695.310 -3.076 -19.738
11718.750 -3.122 -19.504
11742.190 -3.164 -19.295
11765.630 -3.203 -19.111
11789.060 -3.238 -18.957
11812.500 -3.272 -18.832
11835.940 -3.305 -18.741
11859.380 -3.337 -18.678
11882.810 -3.370 -18.648
11906.250 -3.403 -18.644
11929.690 -3.439 -18.667
11953.130 -3.475 -18.712
11976.560 -3.514 -18.773
12000.000 -3.555 -18.849
12023.440 -3.598 -18.933
12046.880 -3.645 -19.025
12070.310 -3.693 -19.126
12093.750 -3.744 -19.225
12117.190 -3.796 -19.321
12140.630 -3.850 -19.415
12164.060 -3.906 -19.502
12187.500 -3.963 -19.584
12210.940 -4.021 -19.644
12234.380 -4.081 -19.694
12257.810 -4.141 -19.730
12281.250 -4.199 -19.739
12304.690 -4.257 -19.737
12328.130 -4.311 -19.725
12351.560 -4.362 -19.706
12375.000 -4.411 -19.694
12398.440 -4.456 -19.701
12421.880 -4.499 -19.715
12445.310 -4.542 -19.754
12468.750 -4.586 -19.807
12492.190 -4.633 -19.880
12515.630 -4.681 -19.970
12539.060 -4.732 -20.052
12562.500 -4.789 -20.133
12585.940 -4.847 -20.205
12609.380 -4.909 -20.243
12632.810 -4.974 -20.268
12656.250 -5.038 -20.273
12679.690 -5.103 -20.244
12703.130 -5.169 -20.203
12726.560 -5.234 -20.138
12750.000 -5.301 -20.060
12773.440 -5.366 -19.969
12796.880 -5.431 -19.856
12820.310 -5.496 -19.738
12843.750 -5.559 -19.601
12867.190 -5.622 -19.443
12890.630 -5.685 -19.283
12914.060 -5.745 -19.107
12937.500 -5.804 -18.918
12960.940 -5.862 -18.733
12984.380 -5.916 -18.536
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13031.250 -6.022 -18.158
13054.690 -6.072 -17.983
13078.130 -6.122 -17.828
13101.560 -6.170 -17.697
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13406.250 -7.018 -17.029
13429.690 -7.090 -16.947
13453.130 -7.163 -16.891
13476.560 -7.236 -16.856
13500.000 -7.313 -16.839
13523.440 -7.395 -16.845
13546.880 -7.483 -16.866
13570.310 -7.579 -16.881
13593.750 -7.682 -16.880
13617.190 -7.791 -16.843
13640.630 -7.906 -16.754
13664.060 -8.023 -16.616
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13710.940 -8.258 -16.156
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13828.130 -8.795 -14.217
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14320.310 -9.969 -1.304
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14414.060 -10.096 1.343
14437.500 -10.119 2.033
14460.940 -10.138 2.712
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14507.810 -10.160 4.050
14531.250 -10.166 4.685
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14601.560 -10.156 6.445
14625.000 -10.147 6.982
14648.440 -10.139 7.481
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14718.750 -10.094 8.732
14742.190 -10.072 9.078
14765.630 -10.051 9.384
14789.060 -10.027 9.615
14812.500 -10.002 9.801
14835.940 -9.982 9.923
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14976.560 -9.959 9.945
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15023.440 -9.980 10.020
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15070.310 -9.995 10.169
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15351.560 -9.678 9.892
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15421.880 -9.546 8.935
15750.000 -9.716 3.011
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15796.880 -9.789 2.443
15820.310 -9.826 2.162
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15867.190 -9.908 1.611
15890.630 -9.956 1.333
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15937.500 -10.063 0.842
15960.940 -10.122 0.626
15984.380 -10.183 0.420
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16031.250 -10.310 0.030
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16242.190 -11.202 -0.750
16265.630 -11.336 -0.296
16289.060 -11.465 0.288
16312.500 -11.569 1.022
16335.940 -11.663 1.843
16359.380 -11.733 2.688
16382.810 -11.780 3.597
16406.250 -11.819 4.526
16429.690 -11.829 5.411
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16523.440 -11.770 9.101
16546.880 -11.734 9.955
16570.310 -11.686 10.818
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16617.190 -11.577 12.488
16640.630 -11.510 13.296
16664.060 -11.440 14.086
16687.500 -11.362 14.822
16710.940 -11.280 15.585
16734.380 -11.205 16.294
16757.810 -11.119 16.974
16781.250 -11.036 17.703
16804.690 -10.952 18.372
16828.130 -10.851 19.047
16851.560 -10.751 19.751
16875.000 -10.644 20.353
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16921.880 -10.406 21.530
16945.310 -10.281 22.030
16968.750 -10.154 22.550
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17015.630 -9.903 23.382
17039.060 -9.778 23.758
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17203.130 -8.910 24.253
17226.560 -8.817 23.951
17250.000 -8.757 23.592
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17601.560 -8.770 20.120
17625.000 -8.782 20.017
17648.440 -8.793 19.881
17671.880 -8.790 19.757
17695.310 -8.791 19.580
17718.750 -8.776 19.347
17742.190 -8.765 19.127
17765.630 -8.762 18.828
17789.060 -8.756 18.462
17812.500 -8.755 18.139
17835.940 -8.760 17.762
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17906.250 -8.782 16.712
17929.690 -8.788 16.390
17953.130 -8.793 16.034
17976.560 -8.791 15.712
18000.000 -8.791 15.381
18023.440 -8.790 15.003
18046.880 -8.782 14.619
18070.310 -8.782 14.224
18093.750 -8.781 13.772
18117.190 -8.781 13.359
18140.630 -8.792 12.935
18164.060 -8.803 12.508
18187.500 -8.817 12.102
18210.940 -8.836 11.728
18234.380 -8.860 11.360
18257.810 -8.887 10.990
18281.250 -8.914 10.632
18304.690 -8.945 10.293
18328.130 -8.986 9.976
18351.560 -9.029 9.618
18375.000 -9.077 9.333
18398.440 -9.135 9.034
18421.880 -9.195 8.765
18445.310 -9.264 8.577
18468.750 -9.341 8.383
18492.190 -9.417 8.264
18515.630 -9.501 8.208
18539.060 -9.587 8.172
18562.500 -9.669 8.190
18585.940 -9.750 8.254
18609.380 -9.828 8.346
18632.810 -9.901 8.491
18656.250 -9.981 8.620
18679.690 -10.048 8.709
18703.130 -10.116 8.825
18726.560 -10.187 8.900
18750.000 -10.255 8.942
18773.440 -10.329 8.992
18796.880 -10.404 9.002
18820.310 -10.482 9.031
18843.750 -10.564 9.054
18867.190 -10.647 9.089
18890.630 -10.730 9.150
18914.060 -10.815 9.228
18937.500 -10.897 9.311
18960.940 -10.974 9.418
18984.380 -11.049 9.519
19007.810 -11.114 9.610
19031.250 -11.176 9.724
19054.690 -11.237 9.774
19078.130 -11.286 9.804
19101.560 -11.336 9.848
19570.310 -11.889 6.085
19593.750 -11.922 5.741
19617.190 -11.955 5.439
19640.630 -11.986 5.144
19664.060 -12.015 4.873
19687.500 -12.040 4.626
19710.940 -12.064 4.382
19734.380 -12.084 4.147
19757.810 -12.101 3.910
19781.250 -12.115 3.679
19804.690 -12.127 3.446
19828.130 -12.139 3.215
19851.560 -12.150 2.966
19875.000 -12.158 2.731
19898.440 -12.169 2.491
19921.880 -12.175 2.263
19945.310 -12.188 2.059
19968.750 -12.201 1.822
19992.190 -12.212 1.606

You could have just posted the link... ;)

http://personal.inet.fi/private/ilkka/RSAnalogueSPL.txt

And yes, save that as a txt file and use as a mic correction file with TrueRTA.

Originally posted by Iceblade
Claude,

I've always heard to place it in the exact location that your ears would be in your primary setaing position, angled slightly forward.. maybe 20 to 30 degrees down from the ceiling towards the front of your room. Some people point it directly at the front of the room... others use 45 degrees.

Regs,
Jeff

Thanks for responding....I really appreciate the advice. My sub it positioned right behind my recylner. Would I still want it at my seating ear level position and pointed slightly towards the front as you mentioned?

I should have my SPL Meter tomorrow.

Thx,
Claude

Please take the setup questions to a non-sticky thread.

According to the instructions on Avia and DVE test DVDs, point the meter straight UP (at your listening position(s) -- or between them. This is also what I have read on SVS and other sites.

This is also what the Pionner MCACC and other Auto-Calibration receivers also recommend.

Leaning the meter forward biases the meter readings falsely. The only time you want to point towards any speaker is if you are making "Near Field" measurements -- done outside (or in an anechioc chamber).

ACI says to add 6.2 at 20Hz. The other ones say to add 7.5 at 20Hz. What gives?

Originally posted by Eddie Horton
ACI says to add 6.2 at 20Hz. The other ones say to add 7.5 at 20Hz. What gives?
6.2dB's comes from the general c-weighting correction. 7.5dB's comes from one guy's measurements. I believe 6.2dB is more closer to the "truth".

Would the Digital Radio Shack SPL Meter have the same correction table?

Yes.

Originally posted by Ilkka
Yes.
Thanks.

Ed Mullen posted the correction factors for a B&K SPL meter in C-weighted mode:

====================
You can clearly round these off - the program simply calc'd them out to several significant digits.

Frequency C-Weight
10 -14.33259693
10.59463094 -13.52968703
11.22462048 -12.74595335
11.89207115 -11.98268094
12.5992105 -11.24113838
13.34839854 -10.52255777
14.14213562 -9.828113197
14.98307077 -9.158898305
15.87401052 -8.515903684
16.81792831 -7.899994991
17.81797436 -7.311892737
18.87748625 -6.752154684
20 -6.221161728
21.18926189 -5.719108023
22.44924097 -5.24599587
23.7841423 -4.801635653
25.198421 -4.38565084
26.69679708 -3.997487754
28.28427125 -3.6364296
29.96614154 -3.30161399
31.74802104 -2.992053117
33.63585661 -2.706655603
35.63594873 -2.444249093
37.75497251 -2.203602722
40 -1.983448665
42.37852377 -1.782502185
44.89848193 -1.599479687
47.5682846 -1.43311451
50.396842 -1.282170279
53.39359417 -1.145451828
56.56854249 -1.021813749
59.93228308 -0.910166743
63.49604208 -0.809481987
67.27171322 -0.718793751
71.27189745 -0.63720053
75.50994501 -0.563864932
80 -0.498012574
84.75704755 -0.438930194
89.79696386 -0.385963182
95.1365692 -0.338512687
100.793684 -0.296032457
106.7871883 -0.258025523
113.137085 -0.224040813
119.8645662 -0.193669799
126.9920842 -0.1665432
134.5434264 -0.142327811
142.5437949 -0.12072348
151.01989 -0.101460247
160 -0.08429567
====================

Has anyone looked through all of youngho's nice links and noted what the unit-to-unit variation is for the RS meter?

Thanks

I didn't see one.

I looked; they all seem to be pretty much the same.

Sorry if this has been asked before but what frequency are the internal test tones at on a THX certified receiver? I currently have mine set up where the SPL meter bounces between 75-78dB.

Pink noise, which is a mix of many frequencies. And the THX certification has nothing to do with it (or much else).

gti.net link is gone.

Here's the new site (http://mysite.verizon.net/tammie_eric/audio/rsmeter/33-2055/33-2055.html) (Eric Wallin's RS meter mods).

And here (http://www.stereotimes.com/acc032902.shtm) is a discussion of the mods with some interesting related notes.
.

Thanks for the update, heading out in an hour to get an anolog meter.

One question, if I get 'it', the correction talk, (and I may not), I can either use the stock unit and apply the correction values published in various places, "OR", change out the caps. as discussed in the Wallin meter mod.

I shouldn't do both - correct???

Are the correction factors the same for the digital version of the Radio Shack SPL meter?

Editted:

No, especially below about 150 Hz. Nor is the new analog meter (new after the question was originally posted) the same as the old, although the digital and new analog meters are quite similar. See page 3 of this thread for new data.

Today I got my professionally calibrated microphone. Even without any correction files, it's only 0.5 dB off at 10 Hz. Pretty impressive. It was calibrated against B&K 4133 microphone.

I have now measured it against my analog RS meter. As I have said, the RCA output jack is weighted (C or A). But as Ethan showed, it appears that the output of the RCA jack of the digital RS meter is unweighted when set to C-weighting, when set to A, it's A-weighted. When set to C, it has a flat FR atleast down to 20 Hz.

Here is a TrueRTA screen of my results.

http://personal.inet.fi/private/ilkka/truerta/microphone_rs_comparison.png

As you can see, even with those general CFs, the RS meter is still below the true FR. It tracks the mic down to 40 Hz, but below that it's off. You need to compensate even more than for example 7.5 dB @ 20 Hz. Around 11.5 dB seems to be more closer. Of course every RS is different, so this might not apply to your RS. Although me and my friends have measured total of three RS meters (analog) and they all give pretty similar FR.

http://personal.inet.fi/private/ilkka/RS_calibrated.txt

Here is a calibration file which turns my RS into calibrated measurement microphone. When using this file its FR is within 1 dB (10 Hz - 200 Hz) from my calibrated microphone. It may not be as perfect with your RS, but much better than the general CFs. Notice that general CFs are way off below 15 Hz.

Analog version:
Use atleast general CFs or this (http://personal.inet.fi/private/ilkka/RS_calibrated.txt) file when measuring with the TrueRTA or smilar. Same thing if you are measuring manually (looking at the needle). You can use the rough corrections below, if you don't want to check the file (if you are measuring manually, add those corrections, do not subtract them).

Frequency / Correction
10 Hz +5 dB
12 Hz +6 dB
16 Hz +14.8 dB
20 Hz +11.5 dB
25 Hz +7.8 dB
30 Hz +5 dB
40 Hz +3.2 dB
50 Hz +2 dB
80 Hz +1 dB
100 Hz +1.2 dB

Digital:
Do not use any correction files when measuring with TrueRTA or similar. The output of the RCA jack is unweighted when set to C-weighting. When measuring manually, add corrections shown above to the readings.

Awright, I'm confused. Why would you not use any CFs when feeding a C-weighted, digital RS meter to TrueRTA or ETF? The deviations are due to the meter, not the weighting contour.

Awright, I'm confused. Why would you not use any CFs when feeding a C-weighted, digital RS meter to TrueRTA or ETF? The deviations are due to the meter, not the weighting contour.
Yes I admit, it is confusing. But as Ethan's (and my friends) measurements show, the output of the RCA jack is unweighted. I don't know how and why they have done it, but the proofs are pretty solid. I'll try to get a digital measure to myself and measure it too.

And the deviations are due to the weighting contour and the meter (analog version). As you can see from my TrueRTA screen, if you compensate for the C-weighting, it is not enough. As we all know, the general CFs compensate a little bit more than for the C-weighting, but still not enough.

Which correction table can be loaded for use with RoomEQ Wizard and the analogue RS meter? Or do you need to load one?

dD

Which correction table can be loaded for use with RoomEQ Wizard and the analogue RS meter? Or do you need to load one?

dD

http://personal.inet.fi/private/ilkka/RS_calibrated.txt

You can use that one. Just rename it to .cal.

Thanks!

I'll let you know how I make out.

dD

http://personal.inet.fi/private/ilkka/RS_calibrated.txt

You can use that one. Just rename it to .cal.


When I used this in RoomEQ Wizard a response plot of the radio shack meter showed up.

I also got a plot for the subwoofer measurement.

What I don't understand: Do I want to then make the final EQ corrections to match the corrected Radio Shack meter plot? Or is the goal to make the plot close to a straight line across the graph?

Does anyone have any correction factors that go below 10hz? Even just a couple of hz would be helpful.

Does anyone have any correction factors that go below 10hz? Even just a couple of hz would be helpful.
I could do some measurements using my analog Radio Shack, but unfortunately I can't promise that they are accurate for your meter. I definitely recommend some more expensive SPL meter or microphone, if you need to measure frequencies that low. Although most microphones do come with a calibration info only down to 10 Hz (mine too).

Thanks for the response. It's not really THAT important. My in-room response starts to get a bit jagged towards 10hz, so I was really just curious what it does below that. Not worth any work though.

Thanks again!

I have measured my analog RS meter mic against my calibrated Behringer ECM8000 and came up with quite the different corrections from above. John Mulcahy (REW) and Ken Bruce (brucek) calculated new correction values based on this measurement and created a newrs.cal file graphed as follows:

http://i1.tinypic.com/o7t2l2.jpg

-------


When these correction values were used with a different RS meter mic and compared to the calibrated ECM there were very slight variances, thus indicating there are slight variances in response from one analog RS meter mic to the next, which we pretty much already knew this. The above correction values can be downloaded as a .cal file...

newrs.cal available here. (http://www.hometheatershack.com/forums)

-------

So now we have "corrected" correction values - serveral times over? The values posted at the beginning of this thread were all in agreement - (e.g. at 20Hz the meter is down 7.5dB, etc.) Are we now saying all those are wrong? :confused: Realizing that the TRUTH of a matter is sometimes difficult to come by, I'm just hoping we can determine who's correction values are to be trusted.

Ok Maybe it is just me, but what correction should I use? For exemple I saw for 20hz: -6.5, -7.5, -11.5 and -12.4 :confused:

What are the globaly accepted corrections for the R.S. Analogue SPL Meter 33-2050 ?

Good point... and I don't know what to tell you other than to show you what we've done above. I sent my ECM8000 off and had it calibrated. It was not off much to begin with. From the several calibration files I've seen from various members who have had their ECM calibrated, they only varied slightly from mine.

Here's what my ECM8000 calibration file looks like (-1.82db at 20hz):

http://www.hometheatershack.com/bfdguide/images/ecm8000calfull.jpg

I basically followed the instructions of John Mulcahy (RoomEQ Wizard) and Ken Bruce. Here's a quote from John:
You need to be very cautious in using measurement data to derive corrections. In areas where the response is changing rapidly (especially where it is dropping) very slight differences in the positions of the RS meter and the ECM8000 will produce significant differences in the measurements, but these are due to the positional differences and not the inherent responses of the microphones. Note that it is the microphone capsules that need to be at the same location, which are usually located just inside the tip of the mic. Measuring a response that is already fairly smooth (e.g. after correcting resonances with the BFD, or in a heavily treated room) would give more reliable data.

Therefore we took the drastic peaks and dips out of the response (flattened it to as best we could) and measured the three mics.

Whether there is that much variance from RS mic to RS mic, I just don't know. If you compare Ilkka's corrections vs. our corrections:

10 Hz +5 dB vs. 27.00
12 Hz +6 dB vs. 21.91
16 Hz +14.8 dB vs. 16.15
20 Hz +11.5 dB vs. 12.38
25 Hz +7.8 dB vs. 8.80
30 Hz +5 dB vs. 6.50
40 Hz +3.2 dB vs. 3.46
50 Hz +2 dB vs. 2.21
80 Hz +1 dB vs. 0.98
100 Hz +1.2 dB vs. 0.27

We are within 1.5db of each other from 16hz to 100hz which would be a very reasonable difference from one RS meter mic to the next. What I would question is possibly his calibrated mic's accuracy at 10hz and 12hz. I have a problem believing that any RS meter mic is only -5db at 10hz or -6db at 12hz. Our correction values would be more rational when considering what the old ones were... according to the old corrections, 10hz was down 20db... we adjusted it to 27db. At 12.5hz it was down 16.5db and we adjusted it to ~21db.

Sonnie,

I will do more measurements soon. I have also noticed that the way you measure (manually, with program) affects on needed corrections. My corrections are good for TrueRTA, but not possibly for REW or manual measurements. I have both programs and I will do more measurements soon.

Of course it is also a fact that you can't find two identical RS meters.

And what comes to accuracy of my mic, I trust it, it has been professionally calibrated. It's better than ECM8000 even with no corrections at all. It only needs ~0.6 dB correction at 10 Hz. ;)

I think the bottom line is (similar to what Ilkka stated a few posts above) if you want to make absolute certain you have accurate measurements, you should acquire a good mic or have your mic calibrated. Unfortunately I don't know of anyone who will professional calibrate and SPL meter mic for a reasonable price. Picking up a mic like the Behringer ECM8000, mic amp, mic cable, and having it calibrated, will add to your sub eq'ing about $150 or so. You still have to have an SPL meter.

Sonnie,

I will do more measurements soon. I have also noticed that the way you measure (manually, with program) affects on needed corrections. My corrections are good for TrueRTA, but not possibly for REW or manual measurements. I have both programs and I will do more measurements soon.

Of course it is also a fact that you can't find two identical RS meters.

And what comes to accuracy of my mic, I trust it, it has been professionally calibrated. It's better than ECM8000 even with no corrections at all. It only needs ~0.6 dB correction at 10 Hz. ;)

Thanks Ilkka... I definitely agree on finding two identical RS meters. It would be a miracle.

I wonder how accurate the two mics are that we had our personal mics calibrated against. My ECM was calibrated against a ACO Pacific and your mic was calibrated against a B&K 4133. As I stated above... I see a lot of the ECM's being used that have been calibrated. It appears that all of the calibration files appear fairly close to each other with very slight variances. This makes me feel fairly confident with its' calibration as well.

Thanks Ilkka... I definitely agree on finding two identical RS meters. It would be a miracle.

I wonder how accurate the two mics are that we had our personal mics calibrated against. My ECM was calibrated against a ACO Pacific and your mic was calibrated against a B&K 4133. As I stated above... I see a lot of the ECM's being used that have been calibrated. It appears that all of the calibration files appear fairly close to each other with very slight variances. This makes me feel fairly confident with its' calibration as well.
I believe they were so accurate, that we don't have to worry about them. :) If there are any variations, they are probably well less than 1 dB. So calibrated ECM is a very good and accurate mic. Other variables cause much bigger differences.

I just stopped by Radio Shack to pick up an SPL meter. As others have pointed out they no longer carry the 33-2050. They have a 33-2055 which is the digital one as we all know, but they also had a 33-4050 which seems to be a new analog model.

My question is as follows - does anyone know if the 4050 uses the same innards as the 2050 and can therefore use the same correction tables?

Thanks,
McP

See post #51 in this thread (http://www.nextlevelav.com/forum/showthread.php?t=1265) ... when I mention Rodny's meter, his is the newer style like you are referencing. There was very little difference.

Beautiful.

Thanks much,
McP

How is this Scosche Boom Stick SPL1000 Competition Style Sound Level Meter at Walmart (search for "sound meter") compare to the one from Radio Shack?

sorry to beat a dead horse but there is a lot of differing information, just wanted to triple check:

I use a Digital RS meter, use the RCA output into my laptop and use RoomEQ. Since im using the output jack of the Digital meter, i do NOT apply correction values?

Wondering before I purchace a spl meter. The Radio Shack one is go enough instead of getting an expensive one for homeaudio ? Because even if the CV don't match as long as the speakers say the same db reguardless of correction thats what we are trying to do? If I'm not worried about graphs ? (for now :) )

sorry to beat a dead horse but there is a lot of differing information, just wanted to triple check:

I use a Digital RS meter, use the RCA output into my laptop and use RoomEQ. Since im using the output jack of the Digital meter, i do NOT apply correction values?
Yes... you would need to apply correction values.

Wondering before I purchace a spl meter. The Radio Shack one is go enough instead of getting an expensive one for homeaudio ? Because even if the CV don't match as long as the speakers say the same db reguardless of correction thats what we are trying to do? If I'm not worried about graphs ? (for now )
If you want to simply level match your speakers then no, you would need correction values. You really only need the correction values if you are tryig to level the frequency response of your speakers.

sorry to beat a dead horse but there is a lot of differing information, just wanted to triple check:

I use a Digital RS meter, use the RCA output into my laptop and use RoomEQ. Since im using the output jack of the Digital meter, i do NOT apply correction values?

...

Digital:
Do not use any correction files when measuring with TrueRTA or similar. The output of the RCA jack is unweighted when set to C-weighting. When measuring manually, add corrections shown above to the readings.
But Sonnie, I think we are all confused because of the above quote by Ilkka which is located at the top of this page. With your tests recently, have you actually tested a Radio Shack digital SPL meter vs an analog one?

I have not personally tested between the digital and analog, however, another forum member did and there was a difference in his testing.

I'm not sure on Ilkka's quote there. I thought the RCA output was in-line after C-weighting. I also didn't think C-weighting effected frequencies as low as what we are correcting. IOW's, corrections are needed for all the meters. Maybe Ilkka could elaborate because I may not fully understand myself.

How about the analog meter from RS? There's an older version.

I believe the model number for the "current" version is 33-4050. But what if you have the one from the 90s? It's model number 33-2050. Do you know if the corrections are the same for that model as well?

I believe that if a meter is calibrated to the "weighted curve" in should be similar in performance; i.e. RS, NADY, the blue and yellow fleabay one, etc. They all look to be built by the same OEM and then outsourced to others for sale. I've attached a scan of the curves with an explanation. HTH

Sonnie?, Ilkka?,

Any further comment about the recent posts by me and Irfan?

Also, Sonnie, you mentioned that you didn't think that the C-Weighting compensation affected the frequencies that we are trying to correct with subwoofer equalization. What frequency range does C-Weighting affect then?

I did reply to both your comments. I'm just not familiar enough and don't really understand C-Weighting well enough to chisel in stone a comment about it. My statement included an "I also didn't think" preface and this comment at the end: "Maybe Ilkka could elaborate because I may not fully understand myself." My thinking ain't always accurate and I believe he would be more familiar with this than I would. I have seen comments by some of the more knowledgeable to this effect, or at least I thought they were more knowledgeable.

Without a doubt though, I do know that by using C-Weighting it does NOT make the necessary corrections for the RS mic to be accurate... you DO need correction values for all of the RS SPL meter mics.

I have an older model analog and 3 newer models. I have tested between the older and two of the newer models and they were all three different. It wasn't by much but it was different.

The whole key here is that the old correction values are not adequate... they are way off for any meter I have tested against my calibrated ECM8000. However using the newrs.cal file that John Mulcahy, Ken Bruce and myself created, it will get you closer than any other .cal files I have tested. Due to the variances from meter to meter, you may be off a couple of db but that is much better than being off as much as the old correction values would cause you to be off.

Many moons ago, before I was actually a member here... I say about 5 years ago, there was a guy here on AVS that posted his results of testing the RS Meter and stated the old correction values were accurate... therefore I always used them. I just simply decided to acquire a better mic and have it professionally calibrated so that I wouldn't have to use the RS mic. I decided to test the differences and learned how drastic a difference there is. I came here and noticed Ilkka had done the same.

I posted this above in an earlier post showing the differences between his test and my test:

10 Hz +5 dB vs. +27.00
12 Hz +6 dB vs. +21.91
16 Hz +14.8 dB vs. +16.15
20 Hz +11.5 dB vs. +12.38
25 Hz +7.8 dB vs. +8.80
30 Hz +5 dB vs. +6.50
40 Hz +3.2 dB vs. +3.46
50 Hz +2 dB vs. +2.21
80 Hz +1 dB vs. +0.98
100 Hz +1.2 dB vs. +0.27

We are within 1.5db of each other from 16hz to 100hz which would be a very reasonable difference from one RS meter mic to the next. What I would question is possibly his calibrated mic's accuracy at 10hz and 12hz. I have a problem believing that any RS meter mic is only -5db at 10hz or -6db at 12hz. Our correction values would be more rational when considering what the old ones were... according to the old corrections, 10hz was down 20db... we adjusted it to 27db. At 12.5hz it was down 16.5db and we adjusted it to ~21db.... while he went the opposite direction with his adjustments.

That's about all I know to tell ya.

I'm not sure what happened to Ilkka... I hope he's okay. I've sent him a few PM's in various forums but he's not responded and I noticed he hasn't posted here since March... which is highly unusual for him being he's made almost 2200 posts since Feb 2005.

Btw... I have two brand new analog RS Meters sitting on my table. I plan to measure these against my calibrated mic. I will not need them when finished and will be letting them go for exactly what I have in them and they will include the calibration file with them. I am simply doing this to test between meters. Hopefully I'll get around to this in the next few weeks.

Hi again, Sonnie,

Thanks for the reply again. I know that you had responded to my previous post but I still felt that the question about whether the RCA output of the RS digital SPL meter was c-weighted compensated or uncompensated was still unresolved, that is, not tested and verified by anyone else other than the forum member, Ethan Winer, of whose results that Ilkka posted which suggested that the RCA output was uncompensated unlike the RS analog meter output which is C-weighted compensated.

I believe this would make a big difference when using the REW program and the RCA output of the RS digital SPL meter because according to Ilkka on post #16 of this thread, it says that the value of +6.2 dB at 20 Hz (as taken from a previous compensation table that he had come up with which is referenced in post #10 of this same thread) comes from the general c-weighting compensation. Note this value he is talking about is not referring to any SPL meter inaccuracy or otherwise but is referring to the general c-weighting compensation definition. So I take it to mean that if one had a perfectly flat microphone at 20 Hz but one took the output of that mic at 20 Hz and applied the c-weighting compensation to the output (like the RCA output of the analog RS SPL meter does, that is, it applies a c-weighting compensation), then the output would decrease by 6.2 dB so one would have to add back 6.2 dB to the reading to get it back to normal.

Now the correction values you have come up with were done with the RCA output of the analog RS SPL meter which is known and verified to have a c-weighting compensation done to it so your values corrects for the both the c-weighting compensation plus the inaccuracy of the RS SPL meter mic. So using your value of +11.5 dB for 20 Hz, I would take this to mean that the microphone was inaccurate by -5.3 dB and then the c-weighting compensation of -6.2 dB was added to it by the c-weighting compensation circuits of the RS analog SPL meter so if you add these two numbers together you get your -11.5 dB deviation that you came up with.

Now with the digital RS SPL meter, if it is the case, as Ethan Winer had supposedly verified, does not have the c-weighting compensation applied to the RCA output, then even if the microphone from your analog RS SPL meter was moved into the digital RS SPL meter, since the RCA output does not supposedly have the c-weighting compensation, the correction value at 20 Hz would only be +5.3 dB using your findings.

This is why I think it is important that someone else test another one or two or more digital RS SPL meter RCA outputs and see if Ethan Winer is correct or not.

P.S. I found a webpage here: http://www.diracdelta.co.uk/science/source/c/w/cweighting/source.html that gives the formula for c-weighting compensation plus has a calculator that you can input any frequency and these values follow exactly the compensation table of Ilkka's that is referenced in post #10 of this thread.

What you say makes good sense. I think if you will post a question about this in the BFD | REW forum (link in sig), you might can get John Mulcahy, Ken Bruce, Wayne Pflughaupt, all to chime in on this. I believe you'd get some answers maybe... John understands this stuff pretty well... a lot better than I do.

I can tell you that when I did my testing on the analog units I did not compensate for C-Weighting in REW.

I would suggest Ethan knows what he's doing and would be correct with his testing, however, whoever manufactures this meter could have made some changes, therefore further testing may be beneficial. Since I have two analog meters to test, I'll see if I can get my hands on a couple of digital meters as well and test them too.


EDIT: Have two digital meters on their way. I will test one older analog, two new analog and two new digital meters all at the same time and report my findings in the BFD | REW forum once concluded.

The results are in... whether C-Weighting is applied or not is irrelevant... the meters (all of them) still need correction values applied.

See the test here (http://www.hometheatershack.com/forums/bfd-rew-forum/361-radio-shack-spl-meter-correction-values-all-new-cal-files-published.html)!

And the resulting calibration files here (http://www.hometheatershack.com/forums/downloads-page/19-downloads-page.html).

Sonnie has produced calibration files for the old analog meter (which we already had), the new analog meter, and the (only) digital meter - the first ones I've seen for the latter two. Note that the digital meter is much more like the new analog meter than the old analog, which means I've been using a bad calibration file for a long time. :(

Sonnie, do we have permission to post the file contents here?

And the resulting calibration files here (http://www.hometheatershack.com/forums/downloads-page/19-downloads-page.html).


Sonnie, do we have permission to post the file contents here?
Absolutely! We are not copyrighting calibration files... :D Distribute as you wish.


Is it a fact that Radio Shack has only had one model number for the digital meter? I need to make note of this if so... I couldn't seem to verify it one way or another.

I can only say that it's been the same since 2004, and that the digital looks just like the old analog (different insides, though).

I see that the calibration files only go up to a bit over 100 Hz. Did you compare response above that at all? If I recall, the new meters are reported to have a difference HF response over about 8 kHz.

We didn't compare above 100hz since we are mainly using this for sub measurements and we were allowing C-weighting to pick up the slack from 100-200hz. I personally use my calibrated ecm for full range for the few times I've looked at it. Plus it's better to use a flat response when calibrating and it would be impossible for me to get anywhere remotely close to flat full range in my room. It's ugly above 100hz with all the zigzagging.

I see that the calibration files only go up to a bit over 100 Hz. Did you compare response above that at all? If I recall, the new meters are reported to have a difference HF response over about 8 kHz.

It's really only the response below 100Hz where any of the RS meters diverge from the C weight standard with any significance. Above that we allow REW (Room EQ Wizard) built in C weight compensation to take over. If a meters calibration file is loaded, the C weight compensation is in effect outside the frequency range limits of the calibration file. In the case of sonnies calibration files, the C weight compensation merges and takes over at >~105Hz. Certainly the area of concern is from 10Hz to 200Hz for equalizing a subwoofer. Any readings with an RS meter above 10KHz are questionable.

Be cautioned that using measured data (as we have done) is a dubious method to derive a calibration file for a meter. We simply decided that it would be a heck of a lot more accurate than what's available - which until sonnie began testing was a single crude low resolution file for all the three types of RS meters.

Using the calibration files that sonnie has posted on his forum for the three meter types, measuring against a professionally calibrated ECM microphone, provide results that are quite close and acceptable for sub EQ. Using the best sweep to sweep results there are always anomolies which can be attributed to anything from element positional differences to someone moving around the room or scratching their nose. Either way, the calibration results are quite close.

brucek

These are for the current analog meter used as a microphone.

10 -7.29
11 -6.85
12 -6.35
13 -5.70
14 -5.10
15 -4.60
16 -4.30
17 -4.00
18 -3.70
19 -3.55
20 -3.25
21 -3.15
22 -3.00
23 -2.90
24 -2.80
25 -2.65
26 -2.58
27 -2.45
28 -2.25
29 -2.09
30 -2.01
31 -1.91
32 -1.80
33 -1.71
34 -1.55
35 -1.40
36 -1.27
37 -1.15
38 -1.07
39 -1.00
40 -0.98
41 -0.93
42 -0.86
43 -0.75
44 -0.69
45 -0.63
46 -0.59
47 -0.55
48 -0.50
49 -0.49
50 -0.46
51 -0.46
52 -0.45
53 -0.46
54 -0.47
55 -0.47
56 -0.48
57 -0.49
58 -0.50
59 -0.51
60 -0.53
61 -0.55
62 -0.57
63 -0.59
64 -0.61
65 -0.63
66 -0.65
67 -0.67
68 -0.68
69 -0.72
70 -0.75
71 -0.77
72 -0.79
73 -0.79
74 -0.80
75 -0.82
76 -0.83
77 -0.84
78 -0.86
79 -0.85
80 -0.86
81 -0.87
82 -0.88
83 -0.91
84 -0.94
85 -0.94
86 -0.93
87 -0.92
88 -0.92
89 -0.91
90 -0.90
91 -0.89
92 -0.88
93 -0.87
94 -0.86
95 -0.85
96 -0.84
97 -0.83
98 -0.83
99 -0.82
100 -0.82
101 -0.81
102 -0.80
103 -0.78
104 -0.76
105 -0.73

These are for the current digital meter used as a microphone.

10 -5.66
11 -5.25
12 -4.66
13 -4.20
14 -3.80
15 -3.50
16 -3.30
17 -3.10
18 -2.90
19 -2.70
20 -2.50
21 -2.30
22 -2.10
23 -1.95
24 -1.80
25 -1.60
26 -1.40
27 -1.15
28 -1.00
29 -0.90
30 -0.75
31 -0.65
32 -0.55
33 -0.44
34 -0.33
35 -0.22
36 -0.11
37 0.00
38 0.08
39 0.15
40 0.22
41 0.34
42 0.36
43 0.41
44 0.45
45 0.49
46 0.52
47 0.55
48 0.59
49 0.60
50 0.62
51 0.64
52 0.64
53 0.64
54 0.63
55 0.62
56 0.60
57 0.59
58 0.56
59 0.53
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 0.37
78 0.38
79 0.39
80 0.42
81 0.42
82 0.43
83 0.43
84 0.43
85 0.43
86 0.43
87 0.44
88 0.45
89 0.45
90 0.46
91 0.46
92 0.47
93 0.48
94 0.48
95 0.49
96 0.49
97 0.50
98 0.50
99 0.50
100 0.50
101 0.50
102 0.50
103 0.50
104 0.50
105 0.50

These are for the now-discontinued analog meter used as a microphone.

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
101 -0.25
102 -0.23
103 -0.20
104 -0.17
105 -0.14
106 -0.11
107 -0.07
108 -0.03

An enterprising person might merge these corrections with those posted by Ikka earlier in the thread to get a better full-range set. Unlike the old widely available calibration file, his corrections are somewhat lumpier and appear to map to the response curve measured by Sonny and friends.

Isn't it amazing how the old original "correction" values which have been circulated far and wide for years were so totally OFF!!! Many thanks to Sonny, Bruce, and friends for doing us all a huge service with much diligent research and testing to finally publish something closer to the TRUTH and especially for being tailored to the respective types/models of RS meters!!

Thats for all the work.

Its refreshing to see that the new meters are getting more accurate. I have been using the digital for a while now and am actually very pleased with the unit.

-Eli

Was only one of each type measured? Wondering about the unit-to-unit variation.

Thanks

lol, looks like all my hand drawn "calibrated" curves need to be redone.

Was only one of each type measured? Wondering about the unit-to-unit variation.

Thanks

I only had one of the older model analogs... but I had two of the newer model analogs and two of the digital meters. They were very close to each other in response as you can see from the graphs in the test thread. Even so, those two responses were averaged (the two for the analog and the two for the digital) and then the corrections were set to the average. That should keep us fairly close all around... I'd day you will be within +/- 1db.

If we consider the ATI meter (supposedly took over the meter manufacturing - although I'm not 100% on this - I simply think they did) and their claims of +/- 2db from 32hz on up... this coincides with what we found at least from 30hz up to about 120hz. So it does appear they are getting more standardized/uniform in their manufacturing process and maybe using better components/caps, etc. This would indeed seem to indicate that there's very little variance from meter to meter. Unfortunately I can only confirm this between two meters of each, analog and digital. Even the analog and digital were very close to each other... the minor variances were below 30hz.

I must have missed this part. How do I know if I have an older analog model or a newer one?

Look at the one currently offered on the Radio Shack web site. If it looks like that one, it's "newer". If it looks more like a brick, it's "older".

Or if you were really lazy, you could use the catalog numbers posted above to match to the number on the back of your meter.

Thanks for the reply - I have the newer model.

So - I measure the response at 20hz with a test tone then I have to subtract 3.25 to get the true response? Or do I have to add 3.25. (Using your table above)

Thanks

Your measurement is down 3.25db at 20hz so you will add this to your measurement.

Add negative numbers and subtract positive numbers.

Excellent work guys!

I hate to confuse the situation but I have the older analog model 33-2050 purchased in Canada many years ago and have compared it to my Behringer ECM800 (not calibrated) and assuming the ECM is reasonably accurate out of the box my older RS meter measures fairly accurate and the new table won't apply.

My setup is like this: I'm running the ECM into the metering of a DEQ2496, using the line-out of the RS meter into ROOM EQ Wizard, and of using the RS metering needle as well. Both meters set to C-weighting. 1/3 octave tones provided by Stereophile Test CD2. I planned to use 1Hz increments from ROOM EQ Wizard but ran out of time.

I ran the measurements a few times the first time through with a battery that's been in the unit for awhile and these first measurements had me about 5dB out at 20 Hz from where they increasingly improved improved.

On the next two runs I installed a new fresh battery and the results improved, the corrections I calculate are referenced to the ECM8000:

Line out
200 -.8
160 -1.2
125 -.5
100 -.4
80 -13.6
63 +.7
50 +3.7
40 +.7
31.5 +1.0
25 +1.0
20 +3.5

Needle
200 -1.1
160 -1.2
125 -.5
100 -.8
80 -1.8
63 -.9
50 -1.4
40 -1.0
31.5 +1.2
25 +.7
20 +2.1

I'm a little surprised how close the two meters are, the meters needle being more accurate than the lineout which shows a system problem at 80hz.

So the obvious question: is it possible an uncalibrated ECM8000 is out 10 dB at 20Hz? Anyone have there's calibrated and wish to comment?

Also for Sonnie, how many older model 33-2050 analog meters were sampled to obtain your correction values and was it/they outfitted with a fresh battery?

On a side note, when compared to the ECM8000 my RS meter is most accurate reading 60 dB and steadily becomes less accurate as dB levels increase being out about 2 dB at 100 dB.

I think some of your difference may be C-Weighting. The meter's RCA output is not weighted. You'll need to factor that into your calculations above.

My ECM is -1.8db at 20 hz... -5.33db at 10hz. This is pretty close to what I've seen from other calibrated ECM's. Some may have been a little different at 20hz but not 10db.

I used a new battery because when I started my battery was dead and had to get my wife to pick me up a new one. I only tested the one older meter but if you look back at the other test done by others here, their corrections were pretty close to mine except at 10hz and 12hz, and I think the other one had an error there. Here's what I posted on that earlier:

10 Hz +5 dB vs. 27.00
12 Hz +6 dB vs. 21.91
16 Hz +14.8 dB vs. 16.15
20 Hz +11.5 dB vs. 12.38
25 Hz +7.8 dB vs. 8.80
30 Hz +5 dB vs. 6.50
40 Hz +3.2 dB vs. 3.46
50 Hz +2 dB vs. 2.21
80 Hz +1 dB vs. 0.98
100 Hz +1.2 dB vs. 0.27

We are within 1.5db of each other from 16hz to 100hz which would be a very reasonable difference from one RS meter mic to the next. What I would question is possibly his calibrated mic's accuracy at 10hz and 12hz. I have a problem believing that any RS meter mic is only -5db at 10hz or -6db at 12hz. Our correction values would be more rational when considering what the old ones were... according to the old corrections, 10hz was down 20db... we adjusted it to 27db. At 12.5hz it was down 16.5db and we adjusted it to ~21db.

It's also important that when you compare mics that you are using sweep or tones as flat as you can get. On REW you will need to set the Pre-ref window to 0.25 Tukey prior to taking measurements and the Pre-ref window to 125ms after measuring. All this will affect your results. Plus we ran a sweep and smoothed the response to remove the spiky anamalies.

Hi Sonnie,

I suppose first it would be important to understand the purpose of the "calibration files". I took it to undertand that files were to compensate for inaccuracies of the RS meter when compared to an equally weighted reference meter and this is what I performed, apples to apples.

If, however, the "calibration" files are actually c-weighting compensation/error correction files intended to adjust for inaccuracy and c-weighting from the RS values then this is slightly different. If I have time tonight I'll rerun the test to see if the weighting compensation factors are similar, I suspect they'll be close. Perhaps I missed some new info but I thought it was determined the old RS analog meter has c-weighting applied to the line out, the digital meter does not.

As a general question, it seems faulty to not use c-weighting when calibrating speakers, the intent is to end up with a flat response as heard by your ears not a piece of electronics. Unless the test tones are weighted I don't see any value in not using c-weighting. What the hell am I missing here?

It really doesn't matter whether C-Weighting is applied or not... the end results need correction values to make the mic in the meter read flat.

I cannot say for sure this is your difference between the needle and the RCA output, but it seems logical... I'm not why else there would be a difference. Not why else they would be different. But irregardless... when we plug into the RCA output of those RS meters, we do not get a flat response and (as you stated) the CV's compensate for this.

This whole thread is frightening.

I ran one of the two "Type 0" acoustic laboratories in the country for three years, so I know a thing or two about acoustical measurements.

I don't have a lot of time to get into all the details, but the short of it is Radio Shack and other low cost SPL meters should not be used for Acoustical measurements (response or otherwise) under ANY circumstance. They are specifically designed for UNCALIBRATED, BALL PARK "how loud is this" type of measurements (about 50Hz-5Khz). Any real piece of measuring equipment is labeled either Type 1, or Type 2, or if you get specialized equipment, even Type 0. Even IF these inexpensive meters declare they are Type 2 for "A" weighted measurements, they can still be very inaccurate at low and high frequencies. These meters vary so much from one to the next that a calibration file for one is meaningless for another. In addition, they are not good for measuring above about 105dB. This has to do with poor electronics, but more importantly, the super poor quality of the mics they use.

I know most of you can not afford the Type 0 equipment we use here at Acoupower. But, there are some reasonable alternatives:

1) The AudioXpress site has a good microphone for a reasonable price.
2) Many companies offer PC Card based test and measurement systems that are reasonably accurate and only a few hundred dollars.

The bottom line is there are several ways to get a pretty good test and measurement setup for about $500.00.

Again, please visit the AudioXpress site for more information.

Hello Carlos,

I here where you are coming from, but most people who spend 100 bucks on a BFD aren't too interested in spending 4-500 bucks on a mic setup. While the RS meter isn't perfect, it will be within a few db of accurate. From meter to meter they run about 1-2db in variance, so that's not bad. Most folks won't notice a difference in a couple of db. For the most part we use these in the 20 - 200hz range at about 75-85db. For our purpose they are fine. If someone wants to spend the money to get within .5db of accuracy then there are plenty of mics available for less than 4-500 that will do that too. Remember that most of us are simply the average homeowner and most of us don't want to spend as much or half as much for a mic setup as we did our sub. :D

Sonnie,

Personally, I wish what you were saying were true.

I have experience measuring these units with laboratory grade equipment. Unfortunately, at the very lowest and highest audio frequencies, these meters can vary +-10dB. Actually, near 20kHz, they can vary even more. They are only REASONABLY accurate from about 50 to 5kHz.

That means a very "hot" meter at 20Hz might read 20dB higher than a very low meter. That is much more than a dB or two.

Again, the bottom line is using these meters for ANY kind of SPL vs. Frequency measurements is outside of their intended application.

This is why the first line in my first post on this thread was "I find this whole thread frightening".


Carlos

ATI claims accuracy from 32hz to something another. And even if it's only 32hz to 5khz... that's pretty good.

There's been several people test these things in the real world environment and we've just never seen 10db difference at 20hz from the same model meter to meter... even calibrated against different fairly good quality mics. If our response is off 10db at 20hz, we'll probably be able to notice it... and say... this don't sound right. Plus, for the most part we are trying to tame the bad peaks/spikes and most of those don't occur at 20hz... most are between 30-60hz... so I believe we can get relatively close.

Hey... most of us are simply doing the best we can for the least $$$ we can.

Carlos, you've provided a intriguing criticism (although in my experience the RS SPL meters don't exhibit the variance that you suggest). If they have power compression problems themselves, then maybe they're inappropriate for power compression measurements. I'd be interested, though, to know what mics the guys doing those measurements use, and why the ones that use RS meters don't all show the same results, since the meter should go into compression before the sub?

In any event, what's the alternative? Spend four or more times the amount on better measuring equipment? Or just don't do any measuring?

I find both of those alternatives unacceptable. Do you have another?


BTW, please provide a link to the mic on the audioXpress site. I didn't see one.

This whole thread is frightening.

No doubt to a professional in the business such as yourself, it is so. For those of us trying to get the best audio systems for as little money as possible, not so much. The suggestion to invest $500 in a measurement device for a subwoofer, so we can tame a few room responses is not going to be readily embraced. :)

I'm surprised that you've experienced such a disparity between these cheap meters. When Sonnie had his ECM8000 microphone professionally calibrated (I suspect you'll not be giving the thumbs up to this mic either - doh), we decided it would be interesting to use it as a standard and try and create some calibration files for the three different cheapo Radio Shack meters on the market.

We had already created a file for the original analog meter, but thought we should attempt the newer analog meter and its digital partner since there had been some discussion whether the newer models had a better response.

As we've readily admitted and as I'm sure you can obviously attest, the results obtained from measurement data (against a standard) are dubious at best. But either way, we felt that the final proof would be in the comparison of frequency response data using each meter in question utilizing the popular Room EQ Wizard program. (http://www.hometheatershack.com/roomeq/)

Granted, when conducting any experiment, a sample of four is questionable, but telling none the less. Sonnie tested two new analog meters and two new digital meters. We created the calibration files for them. The meters were suprisingly close. Maybe we got lucky.

Below is the frequency response of the professionally calibrated ECM8000 mic/meter against the two analog meters and the two digital meters using the newly created calibration files from Sonnie site (http://www.hometheatershack.com/forums/). Sonnie used his home theater as the test bed.

They appear fairly close to me and good enough for home use. There are differences, but every measurement reveals a new set of differences. The point being that in a home environment even the smallest positional difference or speaker movement will result in some reponse change. This is evidenced by the anomolies that kept showing up at 22Hz, where each measurement revealed a different response at that frequency. Anyway, you can see that these five responses are within a few dB. That's good enough to set up filters in a parametric equalizer when you have a room resonance that is causing a peak in your response of 20dB at 50 Hz. It sure works for me.

http://i4.tinypic.com/10qzzie.jpg

brucek

BTW, please provide a link to the mic on the audioXpress site. I didn't see one.

I think he is referring to the Mitey Mike II Testing Microphone (http://www.audioxpress.com/bksprods/kits/kd-4.htm) at $193.95 which has been calibrated for use with one of the KD-4 series preamps (from 128.95 to 269.95 depending on whether you want a kit or prebuilt unit and depending on whether you want one or two channels, which one channel would be all you would need)... however, none of the preamps to which the mic is calibrated are available. The mic might work with another lesser expensive preamp... don't know. The mic itself is rated ± 2 dB, 10kHz-20kHz.

http://www.audioxpress.com/bksprods/media/b/kd-4preampb.gif

I'm not so sure how this could be all that much better (if any better at all) than the 50 dollar Behringer ECM8000 measurement mic that is ± 2 dB, 18kHz-46kHz straight out of the box. Of course you'll need a $40 preamp and if you wanna get really accurate all the way down to 10hz (where we can't even adjust - not with the BFD anyway)... you can pay 40 more bucks and have it calibrated against one of those $2,000 mic setups. $130 total.

Bruce,

Your data makes sense and looks good. I agree that things are much better once you individually calibrate each sound level meter.

My impression from reading the messages on this thread is that people are making calibration tables and telling everyone "Here, this is the calibration data for this model of SPL meter". That is what is so terrifying. The models simply vary too much from one to the other. Not just in response, but in level. I looked up the specs at Radio Snack and they only say +-3dB from 50Hz to something in the several k range. That means that one meter could be off by as much as 6dB in comparison to another meter....in their "mid-band". Outside of this range, that difference will increase rapidly. Incedentally, even the R/S lit says the response drops like a rock at very high frequencies.

Acoustical Measurements is an area of expertise of mine...and the readers here need some help. Here we go:

MICROPHONE ITSELF:
BTW, for everyone out there. In case you did not know this. The "GOOD", low cost electric condesner mic is the Panasonic WM-61A available for less then $2.00 at DigiKey. DON'T BUY ANOTHER MIC CAPSULE. Many people don't know that companies such as Earthworks simply buy this mic, dress it up and add some good electronics around it, and sill them for $2,000.00 :eek: . Quite a nice mark-up. Just put the mic itself in a small diameter brass or AL tube from the local hobby store. Use the default mic circuit that Panasonic recommends, and you have yourself a pretty decent microphone :) . It is so cheap and easy to do, I always encourage people to go ahead a make several of them at a time. Many of the $100-$250 Measurement mics out their are exacly this.

ELECTRONICS:
There are several small companies (people) that make inexpensive test and measurement gear. One of them is Here (http://www.etfacoustic.com/index.html) .

This software is $150.00 and works with a sound card. Do any of you guys have sound cards in your PC :p

Seriously, be careful. When talking to this guy, or any other similar outfit, ask them what cards they recommend. Honestly, it may well be worth it to buy the card they recommend.

SO THERE YOU HAVE IT. A reasonable OPTION FOR AROUND $200.00 (WITH misc. hardware and electronics for the microphone). This set-up will measure LOTS of different things with REASONABLE accuracy.

BTW, I am not recomending the etfacoustic outfit over anything else. I have no experience with them. I do know that there are a few outfits like them out there. Just do an internet search like "Audio Measurement System PC Low Cost" and things will pop up.

Also, there are many options for low cost dedicated hardware items. Such as the Clio Lite System (http://www.cliowin.com/lite.htm) available here (http://www.e-speakers.com/). This particular one is very good and is $650.00. Other can be found in the several hundred dollar range.

Anyhow, I hope this helps.

Carlos

Sonnie,

EXACTLY!

Your response showed up before my longer one. Yes, the Mitey Mike is one of the mics I am reffering to when I said there are many mics in the $150 to $200.00 range that are exacly this. Several of the companies that make inexpensive acoustic test and measurement gear offer something very similar. In all fairness to the two guys who designed the Mitey Mike (I know them both), it is better than what the average person will put together with my simple directions above.

Anyhow I got to GO!

Carlos

P.S. How come you guys haven't ordered my drivers (http://www.acoupower.com/picsandvideo.php) yet?

Those drivers look impressive. Seem to be a tad on the expensive side though in relation to what else is available. You designed and built those yourself?



My impression from reading the messages on this thread is that people are making calibration tables and telling everyone "Here, this is the calibration data for this model of SPL meter". That is what is so terrifying. The models simply vary too much from one to the other.


Those 4 meters tested in that chart are from different geographical locations intentionally. From about 29hz on up to 150hz they are +/-1.5db (maybe one spot on one meter is 2db) of each other and the reference mic. It's hard for me to believe that we would find many that would be as much as 6db difference. Chances are unlikely based on this test anyway. Maybe several years ago the consistency might not have been that good. Look around at the various companies that are now putting their label on these units... they are all the same meter, just different names. They rate the response +/-2db from 32hz - 10khz... which would definitely be consistent with what I've measured and tested with the four above.




Not just in response, but in level. I looked up the specs at Radio Snack and they only say +-3dB from 50Hz to something in the several k range.


The level is not gonna make that much difference. We are mainly looking at response. If the level is off it will be uniform throughout the response.

I think you may have gotten some outdated info on the RS meter OR maybe RS just hasn't updated their info... or they are just being extra precautious... again... these are the same meters others are selling labeled with a different name and they have obviously improved them.

Not only that... I have shown earlier on about 3 different occasions in this thread... comparisons between another member test and one of my older test. Each RS meter from different parts of the world. Each compared against different types of calibrated mics... his mic much more expensive than mine. We were within 1.5db of each other from 16hz to 100hz which would be a very reasonable difference from one RS meter mic to the next based on recent tests.

I know bruce stated maybe we were lucky.... (I would say it sarcastically)... but seriously, I find it hard to believe based on all these tests that it's just coincidence that we happened on 6 different meters from different directions, dates of manufacturer, tested with different calibrated mics.... that they are as off as you suggest. The most recent test we have done just don't suggest it.




Incedentally, even the R/S lit says the response drops like a rock at very high frequencies.


We don't care about high frequecies. We are not doing full range measurements. Look at the correction values that are posted here. We have only provided 10hz to about 100hz. Some folks may indeed be using it for whatever... but we did the tests strictly for use with the BFD as it is being used for its parametric eq on subs.... not full range speakers.




MICROPHONE ITSELF:
BTW, for everyone out there. In case you did not know this. The "GOOD", low cost electric condesner mic is the Panasonic WM-61A available for less then $2.00 at DigiKey. DON'T BUY ANOTHER MIC CAPSULE. Many people don't know that companies such as Earthworks simply buy this mic, dress it up and add some good electronics around it, and sill them for $2,000.00 :eek: . Quite a nice mark-up. Just put the mic itself in a small diameter brass or AL tube from the local hobby store. Use the default mic circuit that Panasonic recommends, and you have yourself a pretty decent microphone :) . It is so cheap and easy to do, I always encourage people to go ahead a make several of them at a time. Many of the $100-$250 Measurement mics out their are exacly this.


This may some good info.... if people are inclined to build a mic.

Could the capsule be a replacement for the RS Meter capsule?

Remember, we still have to have the SPL meter.




SO THERE YOU HAVE IT. A reasonable OPTION FOR AROUND $200.00 (WITH misc. hardware and electronics for the microphone). This set-up will measure LOTS of different things with REASONABLE accuracy.


Not really reasonable. Again... we still have to have an SPL meter. Now you are back to $250. Most are gonna be satisfied with the $40-50 for the RS Meter.

I think I have misunderstood something here, and I have also been misunderstood.

I thought the measurments posted by Bruce were using individual calibration files. I am a bit confused still, but after re-reading, it appears he used some "standard" calibration files.

I have also noticed that a few of the low cost SPL meters seem to look the same. Most likely they are all coming from one manufacturing source and it is possible that this source has made improvements to the design that make the current Radio Snack specs obsolete. It is quite possible that the meters are much better than their specs suggest. BTW, one of you brought up a good point in discussinig +-level vs. +-response. Keep in mind that when you say somethig is +-3dB over a frequency range, it's response can be ANYTHING within a 6dB window over that range. For example let say the spec is +-3dB 50Hz to 5kHz. A response that is flat +3dB form 50Hz to 500Hz, and then falls to a flat -3dB from 600Hz to 5Khz actually falls withing the +-3dB spec. As another example, a flat response all the way from 50Hz to 5Khz with a + OR - 6dB peak somewhere also fits the +-3dB spec.

You guys are correct. I am spoiled. My own mic is a laboratory standard from Denmark, +0.5B, -0dB from 5Hz to 20khz. My work demands high accuracy. Also, this mic is nice to use as a calibration mic. Very often I need to do a plane wave tube measurment, or horn throat measurement or an in cabinet measurement, and I don't want to risk destroying my $2,000.00 Bruel and Kjaer Lab mic. I can do a really nice calibration with a low cost condensor mic and put the lower cost mic in "harms way".

BTW, most of the low cost sofware packages out there DO allow you to use your sound card and low cost mic as and SPL meter. AND a FFT analyzer, AND an impusle measurement tool, etc., etc., etc.. You can also use this set up without a mic and measure all the important parameters of any electronic equipment you have.

Carlos

I thought the measurments posted by Bruce were using individual calibration files. I am a bit confused still, but after re-reading, it appears he used some "standard" calibration files.


The standard we used to create the three new calibration files for the three types of RS meters was a professionally calibrated ECM8000.

To verify and test the two latest calibaration files (namely the new analog and the new digital), we took a response measurement of the ECM8000 using its calibration file, then we took a response measurement of two new analog meters using the single new analog calibration file and we also took a response measurement with two new digital meters using the single new digital calibration file.

As much care was taken as possible to remove as many variables and the 5 sweep are shown on the graph in my previous post. This was a test to see if we did a passable job and also to show how much meters of the same kind can vary. We decided our cheap and dirty calibration files were good enough to use and also for anyone else who cared to use them.

BTW, most of the low cost sofware packages out there DO allow you to use your sound card and low cost mic as and SPL meter. AND a FFT analyzer, AND an impusle measurement tool, etc., etc., etc.. You can also use this set up without a mic and measure all the important parameters of any electronic equipment you have.

REW (http://www.hometheatershack.com/roomeq/) software allows you to do all this and much more.... and it's free

brucek

thought i'd add some more data to this thread....Ed Mullen and I compared my RatShack Analog meter to his M30BX back in March. here is the data we too 15-90Hz...

http://www.cyberfrogs.net/files/M30BX%20vs%20RS%20Analog.txt

I've also got a bunch of truerta files with pink noise and quick sweeps of each meter id anyone is interested....just PM me.

i should note, that the measurements were taken from the needle not the line-out on the meter. The numbers look pretty nuch in line with the RSAnalogueSPL.txt that was posted in another thread.

here is the truerta shot of the M30BX (green) vs the RatShack (purple) using pink noise:

http://www.cyberfrogs.net/files/M30BX%20vs%20RS.PNG

Which model analog meter was used?

Of course taking the measurements from the needle would mean the measurement is C-weighted. Not sure if Truerta compensates or not since I'm not familiar with the program.

Interesting though.

Which model analog meter was used?

Of course taking the measurements from the needle would mean the measurement is C-weighted. Not sure if Truerta compensates or not since I'm not familiar with the program.

Interesting though.

the old analog meter was used. i dont believe truerta applys c-weighting.

Which model analog meter was used?

Of course taking the measurements from the needle would mean the measurement is C-weighted. Not sure if Truerta compensates or not since I'm not familiar with the program.

Interesting though.

if i use your values and REW for the old analog meter, should i tell REW that c-weighting was applied or not applied?

Sonnie,

I've removed the C-weighting from the needle values that I showed in the linked txt file. Here are the results, both of our results are within a couple dB:

Hz Correction

15 -16.34361941
16 -15.22756225
17 -13.68583066
18 -12.40894914
19 -11.1888943
20 -10.21882506
21 -9.492874248
22 -9.00598465
23 -8.353778216
24 -7.832450254
25 -7.338682945
26 -7.069573988
27 -6.422577243
28 -5.895453034
29 -5.586226304
30 -5.093151186
31 -5.014680894
32 -4.649442029
33 -4.59621258
34 -4.453903023
35 -4.121540044
36 -3.998252482
37 -3.783259158
38 -3.575858312
39 -3.675418416
40 -3.481370171
41 -3.39319951
42 -3.110441486
43 -3.232674904
44 -3.159517608
45 -2.990622339
46 -2.92567308
47 -2.664381826
48 -2.606485729
49 -2.251744577
50 -2.099938539
51 -2.150866179
52 -2.004342674
53 -2.160198236
54 -2.018276696
55 -1.878434238
56 -1.940538272
57 -1.904466415
58 -1.97010558
59 -2.237351156
60 -1.906106274
61 -1.876281135
62 -2.147792413
63 -2.320562714
64 -1.894520079
65 -1.869597544
66 -1.645732732
67 -1.72286749
68 -1.800947551
69 -1.679922234
70 -1.259744167
71 -1.140369031
72 -1.421755334
73 -1.103864198
74 -1.386659165
75 -1.570106024
76 -1.454172644
77 -1.33882883
78 -1.024046185
79 -1.109797983
80 -1.096059054
81 -0.782805679
82 -0.870015492
83 -0.757667385
84 -0.74574143
85 -0.934218801
86 -1.023081698
87 -0.712313285
88 -0.901897628
89 -0.691819638
90 -0.882065017

You can have REW compensate for C-weighting and C-weighting will be applied to frenquencies where there are no correction values, but from 100-200hz there's not enough adjustment from C-weighting to matter... less than 1db. So... ultimately it doesn't matter if you compensate or not for the sub measurements.

This is really good that you have posted this. It proves yet again that the old long time used RS correction values that were floating around the net for years and years are just not accurate. Like you say... just glancing through a few of the numbers, we are within a couple db of each other. I don't know for sure without inputting both into a spreadsheet, but I suspect if we made a 1db across the board adjustment to either set of values (to account for the level variation)... we would then be within 1db of each other. Either way... what we see is perfectly acceptable from meter to meter and either set of values would get us really close. If you smoothed your response we'd probably be again closer. There are several variables that could cause our minor differences, but we've all done well to provide others with better and more reasonable values.

Of course, it's possible that RS made some changes to the innards of the "old" meter somewhere in its past, so that the correction values were once valid.

I'm thinkin' that is what happened because I remember back in 2001 a fella right here on AVS tested those older correction values to be correct at that time. Somewhere along the line I can't help but to believe RS upgraded the units to be a little better.

but I suspect if we made a 1db across the board adjustment to either set of values (to account for the level variation)... we would then be within 1db of each other. Either way... what we see is perfectly acceptable from meter to meter and either set of values would get us really close. If you smoothed your response we'd probably be again closer.

I imported PLincolns calibration file into REW (http://www.hometheatershack.com/roomeq/) as if it were a frequency response text file and then did the same for the HomeTheaterShack old analog meter calibration file to see how they compared. You can see for yourself from the attached graph that they are very close - (note the Plincoln file is only from 15Hz to 90Hz). I only needed to do a small wholesale gain adjustment on one file as sonnie suggested to match measurement level variation.

I think we can presume that the new calibration files (http://www.hometheatershack.com/forums/bfd-rew-forum/) at sonnies site on the downloads page are fairly accurate.

http://i2.tinypic.com/11hwl1d.jpg


brucek

bruce,

thanks for taking care of that....i was planning on doing the same thing today, but I can't seem to pull myself away from listening to the ascends that arrived today.

it is certainly a good comparison to have...two different calibrated mics and two different people running the same experiment....and then have similiar results. I guess I should have posted this information earlier...

Yeah... excellent graph comparison. Thanks brucek!

This is again so very good... as you say PLincoln... two different people, two different calibrated mics, and also two different RS meters that were more than likely manufactured at different times.

Guys,

Some "Ray" guy published a MASSIVE list of great links in another thread. Many to useful gear and software. There is also a bit of discussion there that has crossed paths with this thread. The thread is here (http://www.avsforum.com/avs-vb/showthread.php?t=359982).

ALSO, I am into R/C airplanes, and this upcomming Wednessday I am calibrating the 3-4 club SPL meters (R/S for the most part) at the club meeting. I may take the time and do some more fooling around while I have 3-4 of them on hand at the same time. I will let you know what I discover.


Carlos

That would probably be very helpful if you could compare those Carlos... thanks!

Tonight was our Monthly club meeting and I had a chance to look at four R/S SPL meters. We also saw some awesome videos of R/C plane crashes (mostly of the turbine variety). My god some of those planes were totally destroyed. ANYHOW, moving on.....

Three of the four meters were analog, and one was the newer digital one. The analogs seemed to vary in both age and abuse by a good margin.

Calibration for level: The digital meter was within 0.5dB of my Lab Mic, two of the analogs were low by 1 dB and one of them was high by 1 dB. Not bad at all, especially considering the brutal conditions these mics are always used in (around loud, high crest factor airplanes spewing spent fuel all over the place).

Comparing the response to the B&K lab mic: Unfortunately, two guys had to leave the meeting early, so I only looked at the digital and one of the three Analog SPL meters for response. The results were impressive, and interesting. First of all, the response differences between them was very small (I was only looking at 1Khz and lower). More importantly, if you applied an inverse C weighting curve, both of the responses would be close enough to flat for most DIY purposes. I was truly impressed. These meters are much better than when I last looked at them (many years ago).

Thread Summary: (If I may be so bold....after all, I did take the time to re-read most of the posts on this thread :) )
1) Standard weighting curves for these meters HELP
2) The response below about 40Hz CAN vary from meter to meter, and sometimes it CAN be very close. Lots of good data on this thread seems to suggest that there is certainly a response GOAL for these meters that is USUALLY held to, but sometimes this goal is simply not realized in the lowest octave.
3) There is some data that shows that the digital meter output is C-Weighted, and some data that shows it is not. The reasons for this are not known at this time. The low end may simply vary that much, or there may have been a design change at some time, or it could be a result of a manufacturing "glitch" of some kind.
4) The meters are substantially more accurate when used for what they were intended for than their specs suggest (looking at basic C Weighted and A Weighted SPL), and the response for much of the room dominated response range (300 Hz and below) is pretty accurate and smooth.
5) The meters are not conistant ENOUGH to be considered accurate in the last octave (below 40Hz) without INDIVIDUAL calibration OR AT LEAST COMPARISON to a reference of some kind.


Carlos

Good info Carlos... thanks for taking the time to check those out.

Btw... I haven't forgot about you on the call. It's been unreal, as you can imagine.

well i had a chance to play around with my new calibration files (that removed the adjusting for the c-weighting) today...I still have to decide how I feel about the new curve. I spent a couple hours with REQ and TrueRTA to get as flat as a response as I could with my rane pe-17

with the new calibration file (sonnie's or mine) there is a huge amount of room gain evident from 22hz down that was masked when using the old cal files. after pushing those peeks down nearly 10-12db, the new flat curve is taking some time to get used to. clearly some of the boomy-ness is gone, but as one would expect, the impact down low of the IB is now "less".

Since I "thought" my setup was flat prior to this new adjustment, I always thought flat sounded real good....when in reality i was listening to c-weighted flat which included the lift at the lower end....I will watch a few movies this way to see if I can adjust to the true flat sound.

I may borrow my friends mic and preamp so i can once an for all eliminate the ratshack meter as part of the problem.

well I'm just thru the first disc of Pearl Harbor (great flic, btw) using the flat curve, and all appears to be well. I think my concerns will be diminish after viewing a few more flix. There is plenty of low end even with the flat curve, without being bloated or over powering. I doubt I will remove any of the low end cut that I applied.

I will post back after a couple more movies and some more tunes.

Flat usually will sound flat... this is why many will choose to optimize to a house curve for movies and flat for music. The house curve will get that low end back for you without the boominess... where you can really appreciate your IB's and what they can do.

Wayne P. does a nice job of explaining the house curve in this sticky thread (http://www.hometheatershack.com/forums/bfd-rew-forum/96-house-curve-what-why-you-need-how-do.html) .

I have just used the new correction tables and my RS (old) analog SPL meter to equalize my subwoofer. I found the new correction table to be far more accurate than the older readings, sub and system have never sounded this good.

Thanks to all who contributed to figuring these out, I knew there was a reason I regularly cheched these forums :-)

A little new in the audio area so please bare with me.

Since I was interested in calibrating my TV and figured I'd do the HT audio calibrated as well. I got my hands on an old RS SPL meter and have been searching for the right correction tables to use.

Way ealier in this thread post #10 there are some tables that I figure I add the second column to the reading at a given frequency,but after 160hz there are 3 columns:

http://www.avsforum.com/avs-vb/showthread.php?p=5272422&&#post5272422


Since thera are tables floating on the web that are different, are these the right tables for my old analog meter? What is the third column for?

Thanks!

These are for the now-discontinued analog meter used as a microphone.

10 -27.00
11 -24.15
12 -21.91
13 -20.13
14 -18.61
15 -17.33
16 -16.15


Question for sonny, why is the correction -27dB at 10Hz when, on your site, the old analog meter using the old cal file showed very good agreement with your calibrated mic at 10Hz? The old cal file uses -20dB at 10Hz, correct? If your calibrated mic matched the old analog meter at 10Hz using a cal factor of -20dB wouldn't -20dB be correct?

I have measured my analog RS meter mic against my calibrated Behringer ECM8000 and came up with quite the different corrections from above. John Mulcahy (REW) and Ken Bruce (brucek) calculated new correction values based on this measurement and created a newrs.cal file graphed as follows:

http://i1.tinypic.com/o7t2l2.jpg

-------


When these correction values were used with a different RS meter mic and compared to the calibrated ECM there were very slight variances, thus indicating there are slight variances in response from one analog RS meter mic to the next, which we pretty much already knew this. The above correction values can be downloaded as a .cal file...

newrs.cal available here. (http://www.hometheatershack.com/foruml)

-------

Is this a merger of your new low frequency data for the old analog meter with the old cal file at higher frequencies or did you actually measure the old analog meter versus your calibration standard out to 20kHz?

This is for the old Radio Shack analog meter. 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 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?

Here is an image from a SMAART session using a Meyer HD1 as the speaker, with a DPA 4006 calibrated mic which is almost razor flat against the Rat Shack digital meter. I made this today.

Hello, maybe im thinking or trying to hard with my RS SPL and Rives disc. Im not sure if i have the old or new analog RS SPL or if the old is analog and new would be digital??? So if someone could plz help with what #,s i would need to +- to/from my samples i have taken. Im using an RS Analog SPL bought it 4 months ago and the Rives disk tracks 32-62. A simple wich post here (Name/Date posted) #'s to use would be fine to. Thanx for any help and sorry if i seemed confused I am :) Edit= OK searched alot more now i know i got the NEW anolog meter 33-4050 so is there any correction tables needed for this or has Rives realy done all the compensation needed if i use tracks 32-62 ?

I was wondering how accurate or inaccurate the newer digital RS meters are in the higher frequencies. I know they are pretty close in the bass region.

But I ask because this is the result I got with REW from my Ascend 340SE center channel (I had the receiver in DPL II Movie) + sub, with the meter on a tripod in the LP aiming diagonally up, as well as aimed forward (attached).

In my room I do have absorber panels on the left/right sides, and I have a large 3~4" thick floor cushion that I put on top of the large square coffee table.

Any idea why the frequency response looks like this in the highs?

Any idea why the frequency response looks like this in the highs?

I'm glad you asked that :) . Here is a similar graph of my left main speaker (a Phase Technology Velocity series tower), measured at the listener position & height with RS digital meter pointing almost vertical.
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=73756&stc=1

What's happening? I believe the "hairy" appearance of the graph at midrange to high frequencies (all frequencies greater than about 300 Hz) is due to comb filtering effects. If you zoom in on any part of the frequency scale, you will see the "hair" is actually narrow, deep minima (or "nulls") at many distinct frequencies. The nulls occur when, at a particular frequency and room location, the amplitudes of the direct sound wave (from the speaker) and all the reflected sound waves (from the walls or even from furniture in the room) sum to zero, or close to zero.

I don't think the "comb filtering" at high frequencies is as annoying to our ears as the graph might suggest. That's partly because each null occurs within a very narrow frequency range, and partly because the nulls are due to reflected sound that is time-delayed (at the listener position) relative to the direct wave. The time delay makes the reflected waves less audible than the earlier direct wave. (That's why we're told to concentrate on treating "early reflections" in room acoustic treatments; the early reflections affect our perception of the sound more than the later reflections.)

Notice that your graph appears flatter than mine below 200 Hz, and significantly flatter below 100 Hz. That may well be the result of the room treatments (absorber panels and cushion): I haven't gotten started with room treatments yet.

The next graph presents some evidence that the comb filtering is due to "reflections" that arrive later than the direct sound from the speakers (if my interpretation of the data is correct). This is a graph of exactly the same measurement as before (same speaker, microphone position, and REW data set); the only change is that I reduced the pre-ref and post-ref time domain widths (under Impulse Response controls) from the standard -125 ms to +500 ms, to a range of only -3 ms to +3 ms, which (I think) eliminates even "early" reflections.
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=73757&stc=1

The broad peak at 6kHz, followed by a steady rolloff toward higher frequency (in all the graphs being considered here), may be due to the non-flat frequency response of the RS meter. The frequency response corrections that we're using apply only to the low bass region, so we don't know what the RS meter frequency response looks like in the top two or three octaves.

Suppose you want to measure the "inherent" or "room effect free" frequency response of a speaker over the full 20 Hz - 20 kHz range? I believe there are some inexpensive microphone models with relatively flat response and known correction curve from 20 Hz to 20 kHz. But how can the "room effects" on the measurement be minimized? In addition to the time domain narrowing trick (that I already described), the ratio of the direct to reflected sound can be increased by placing the microphone close to the speaker, rather than at the listener position. In fact, the microphone can be placed very close to each driver or "port" on the speaker, and a "near-field" measurement can be done for each driver or port. I've seen these types of "near-field" measurements in audio magazines.

For example, here are some measurements from a recent Stereophile review of a speaker with several drivers and ports, the Monitor Audio RS6 (see the color curves in Fig. 3):
http://stereophile.com/floorloudspeakers/306monitor/index3.html
And here is a picture of the speaker being reviewed:
http://stereophile.com/floorloudspeakers/306monitor/index.html

Anyone else have thoughts or information on doing "full-range" (20 Hz - 20 kHz) speaker measurements at home? This topic may have been discussed at some point on the Speaker (rather than Subwoofer) forum, but I haven't tried a search yet.

Sonic icons,

Thanks for the response.

My response under 200hz is due to bass traps I have in the room, as well as the BFD eq I apply to my sub.

Another trick to get rid of the extreme zig zags is smoothing, like going from NONE to 1/12 or 1/6, or even 1/3.

I posted further measurements here:
http://www.hometheatershack.com/forums/22634-post9.html
With full frequency response, the sub+speakers with bass traps but BFD disabled, and more from the bass region.

Anyway, other feedback I've heard is that the RS meter isn't accurate above 4~8KHz. Like you said, I'd need a better mic to get accurate readings for anything other than the bass region.

I was wondering how accurate or inaccurate the newer digital RS meters are in the higher frequencies. I know they are pretty close in the bass region.

But I ask because this is the result I got with REW from my Ascend 340SE center channel (I had the receiver in DPL II Movie) + sub, with the meter on a tripod in the LP aiming diagonally up, as well as aimed forward (attached).

In my room I do have absorber panels on the left/right sides, and I have a large 3~4" thick floor cushion that I put on top of the large square coffee table.

Any idea why the frequency response looks like this in the highs?

I commented about the accuracy of the analog RS Meter compared to a better microphone a little in a different thread. As you can see, my RS meter was inaccurate in the same range as you see in your graph. I took mine at very near field to minimize the comb filtering...

Even if you add 3db to the graph on the right, it still is significantly different. The two should be identical below 2khz for your reference.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=61543

I thought having a RS analog meter #33-2050 which I purchased many years would be all that I would ever need to set up my speakers. That is until I read every message in this thread.

If I'm just concerned about setting proper volume levels in a 5.1 spkr system (versus making absolute measurements of individual spkrs), is it that significant that the RS meter falls off at low freqs? Let's presume all 5 main spkrs are the same & I want to adjust the volume so that they all are equal. Since I am adjusting the spkr sound levels relative to one another, would the meter readings I get be "accurate" for this purpose?

Is there any standard for the spkr test signal that most receivers generate? For example, let's say it is limited in range from 100Hz to 5KHz, then would the poor linearity of the RS meter should be a moot point?

I just got a subwoofer a couple weeks ago so I brought out the RS meter. That's when I started reading all these postings & figured there would be more to setting up the sub than I had planned on. FWIW, I just looked at the Owner's Manual and the response curve for C weighting if flat from about 1.5KHz all the way down to 20Hz. My manual is dated 1993 and the meter is about that old.

The posted correction tables indicate the meter is off about 1dB or less in the 80Hz to 100Hz range of crossover freqs that I've been playing with.

1) Do you think I should just use the meter as is for my application?
2) Any possibility that my meter is so old that it was made to tighter specs than newer ones of the same model, since the response graph indicates flat to 20Hz ?
3) Should I get a new model analog meter?
4) Should I modify my existing meter & swap capacitors as per this thread?

Any comments would be appreciated.
Thanks in advance,
Mike

As long as you make sure your batteries are fresh, you should be okay. If your meter is anything like the newer analogs (digitals are separate, newer ones are much more accurate in the bass range), then it's approximately 2dB off in most of the range played in test tones to set up the subwoofer. This means that if the meter says 75dB, it's actually about 77dB. The roll-off is steeper the lower you go, so after a certain point between 30~40Hz or so, you'd have to add 3dB+, down to 6~7dB in the 20s, etc.

Basically, don't worry about it. :D

cyberbri,

Thanks for the reply. My initial thought was I better modify my meter or use a correction table, which would be easy. But there seems to be basically 2 different tables that keep getting mentioned. Then I figured since I'm not really too concerned about anything below about 80Hz, I should not get too anal about setting spkr levels.

Thanks again.
Mike

cyberbri,

Thanks for the reply. My initial thought was I better modify my meter or use a correction table, which would be easy. But there seems to be basically 2 different tables that keep getting mentioned. Then I figured since I'm not really too concerned about anything below about 80Hz, I should not get too anal about setting spkr levels.

Thanks again.
Mike

Not concerned about anything below 80Hz? Do you not have a subwoofer?

If this has been answered already I apologize and ask to be pointed to my answer. I have a digital RS SPL meter, but from what I have seen the correction numbers are for the analog meter. Do the same numbers apply to the digital meter or is it accurate enough not to need correction numbers?

Thank you

Not concerned about anything below 80Hz? Do you not have a subwoofer?

I guess I should re-phrase that. At this point I am trying to figure out the best crossover freq & level for the subwoofer. So I am concentrating on the range from 80Hz to 100Hz and trying to make sure it's relatively flat at the crossover freq. So I'm playing with that first. Do I want response flat down to 20Hz? Sure I do. I may be wrong & will gladly stand corrected, but I figured the crossover settings should be adjusted first, or at least roughed in.

Sorry for the confusing comment.
Mike

If this has been answered already I apologize and ask to be pointed to my answer. I have a digital RS SPL meter, but from what I have seen the correction numbers are for the analog meter. Do the same numbers apply to the digital meter or is it accurate enough not to need correction numbers?

Thank you


The newer digital meters are much more accurate, to within 1/2dB ~ 1dB for most of the bass range.

I use one, and calibrate for music to 0~1dB over, and for movies 2~3dB over my speakers (with the sub eq'd very flat first).

I guess I should re-phrase that. At this point I am trying to figure out the best crossover freq & level for the subwoofer. So I am concentrating on the range from 80Hz to 100Hz and trying to make sure it's relatively flat at the crossover freq. So I'm playing with that first. Do I want response flat down to 20Hz? Sure I do. I may be wrong & will gladly stand corrected, but I figured the crossover settings should be adjusted first, or at least roughed in.

Sorry for the confusing comment.
Mike


Not at all. Yeah, the speaker placement, listening position, and phase setting on the sub will all effect the frequency response from below the xo to nearly 200Hz. Which is why Avia is nice - it has frequency sweeps from 200Hz down to 20Hz for each of the 5 channels, which are fed through the receiver's bass management so you can measure response.

The newer digital meters are much more accurate, to within 1/2dB ~ 1dB for most of the bass range.

I use one, and calibrate for music to 0~1dB over, and for movies 2~3dB over my speakers (with the sub eq'd very flat first).

Does this mean that I don't need to apply any correction numbers to what the meter reads for my sub?

None, or 1dB at the most. So if you are calibrating your speakers to 75dB, getting your sub to 74dB~75dB is probably about even. But unless you have super-flat response, the meter will probably jump around at least 3~4dB. Just take the mean or average from the sub reading.

Does this mean that I don't need to apply any correction numbers to what the meter reads for my sub?
http://www.hometheatershack.com/newrsdigital.cal

Go to Sonnie Parker's site (above) and there you will find the correction values for the digital meter - (which DOES require a bit of correction in the very lowest region.)

Thank you guys, now I need to re-calculate my sweep numbers, I was using the old correction numbers for the analog meter.

http://www.hometheatershack.com/newrsdigital.cal

the digital meter - (which DOES require a bit of correction in the very lowest region.)


Yes, below 30Hz. Which calibration test tones probably don't even get near...

10 -7.29
11 -6.85
12 -6.35
13 -5.70
14 -5.10
15 -4.60
16 -4.30
17 -4.00
18 -3.70
19 -3.55
20 -3.25
21 -3.15
22 -3.00
23 -2.90
24 -2.80
25 -2.65
26 -2.58
27 -2.45
28 -2.25
29 -2.09
30 -2.01
31 -1.91
32 -1.80
33 -1.71
34 -1.55
35 -1.40
36 -1.27
37 -1.15
38 -1.07
39 -1.00
40 -0.98
41 -0.93
42 -0.86
43 -0.75
44 -0.69
45 -0.63
46 -0.59
47 -0.55
48 -0.50
49 -0.49
50 -0.46
51 -0.46
52 -0.45
53 -0.46
54 -0.47
55 -0.47
56 -0.48
57 -0.49
58 -0.50
59 -0.51
60 -0.53
61 -0.55
62 -0.57
63 -0.59
64 -0.61
65 -0.63
66 -0.65
67 -0.67
68 -0.68
69 -0.72
70 -0.75
71 -0.77
72 -0.79
73 -0.79
74 -0.80
75 -0.82
76 -0.83
77 -0.84
78 -0.86
79 -0.85
80 -0.86
81 -0.87
82 -0.88
83 -0.91
84 -0.94
85 -0.94
86 -0.93
87 -0.92
88 -0.92
89 -0.91
90 -0.90
91 -0.89
92 -0.88
93 -0.87
94 -0.86
95 -0.85
96 -0.84
97 -0.83
98 -0.83
99 -0.82
100 -0.82
101 -0.81
102 -0.80
103 -0.78
104 -0.76
105 -0.73

Sorry couldn't get a smaller pic to work! Are these the correct #'s to add to my raw #'s using the 33-4050. Also any fast link to full #'s from 10-20k please. I see #'s for the OLD RS but having trouble finding full chart for the NEW rs analog. Thanks

Not at all. Yeah, the speaker placement, listening position, and phase setting on the sub will all effect the frequency response from below the xo to nearly 200Hz. Which is why Avia is nice - it has frequency sweeps from 200Hz down to 20Hz for each of the 5 channels, which are fed through the receiver's bass management so you can measure response.

I have the Avia disc but find it difficult to watch the RS meter and the TV simultaneously to correlate the readings with what frequency the sweep is currently moving past. Do you record the Avia sweeps using software so you can analyze them properly?

No, if I'm using Avia, I'm either holding it in front of my head, or have it on a tripod on the couch. I can dart my eyes back and forth reasonably fast enough, and I can always rewind if I want to see a section again.


But I also use Room EQ Wizard, a free computer program, in conjunction with my SPL meter, to do instant (10 seconds or so) sweeps and have graphs made automatically like this:
http://farm1.static.flickr.com/130/379646377_10d38b2f75.jpg

cyberbri, is Room Eq simple to use? Do I just download it, connect my laptop to my receiver and my spl meter to my laptop? IF so, that would be so much easier then doing the sweeps manually.

Yes, it's that easy. There might be some hiccups initially when you try to set it up, and initial setup does take a while because you have to measure your sound card's response, etc., but once you have it down, it's very easy. I can set it up now in about 3 minutes, including getting the meter and tripod out and hooking up all the wires. Sweeps take about 10 seconds each.


Here's the best place to ask REW questions:
http://www.hometheatershack.com/forums/bfd-rew-forum/

Here's where to download the program:
http://www.hometheatershack.com/roomeq/

Here's the setup guide, hosted on hometheatershack:
http://www.hometheatershack.com/roomeq/wizardhelp/help_en-GB/html/index.html

Thanks cyberbri, I will look into it.

Sorry if I missed the response but I believe someone asked about using the Scosche SPL meter that seems to be available from Wal-Mart for about $20. Any opinions on this meter - will it do the job of setting speaker levels on a surround sound system? I don't need to balance all sorts of frequencies, just set sound levels.

An interesting mic calibrating paper.

ARTA Chamber for the Lower End Microphone Calibration (english version - pdf 352kB)
http://www.fesb.hr/~mateljan/arta/AppNotes/AP5_MikroMeasChamber-Rev03Eng.pdf
home page
http://www.fesb.hr/~mateljan/arta/index.htm

And another mic calibrating paper.
How Earthworks Measures Microphones, Khenkin (pdf document)
http://www.earthworksaudio.com/tech/ew_measures_mics.pdf

OK, all those analog meters on ebay look like the old RS meter. I've searched for a schematic on the ebay ones but came up empty. Anybody else with any luck. Oh, btw, the NADY (ASM-2) and Velleman (AVM2050) meters also fit that look-a-like category.

10 -7.29
11 -6.85
12 -6.35
13 -5.70
14 -5.10
15 -4.60
16 -4.30
17 -4.00
18 -3.70
19 -3.55
20 -3.25
21 -3.15
22 -3.00
23 -2.90
24 -2.80
25 -2.65
26 -2.58
27 -2.45
28 -2.25
29 -2.09
30 -2.01
31 -1.91
32 -1.80
33 -1.71
34 -1.55
35 -1.40
36 -1.27
37 -1.15
38 -1.07
39 -1.00
40 -0.98
41 -0.93
42 -0.86
43 -0.75
44 -0.69
45 -0.63
46 -0.59
47 -0.55
48 -0.50
49 -0.49
50 -0.46
51 -0.46
52 -0.45
53 -0.46
54 -0.47
55 -0.47
56 -0.48
57 -0.49
58 -0.50
59 -0.51
60 -0.53
61 -0.55
62 -0.57
63 -0.59
64 -0.61
65 -0.63
66 -0.65
67 -0.67
68 -0.68
69 -0.72
70 -0.75
71 -0.77
72 -0.79
73 -0.79
74 -0.80
75 -0.82
76 -0.83
77 -0.84
78 -0.86
79 -0.85
80 -0.86
81 -0.87
82 -0.88
83 -0.91
84 -0.94
85 -0.94
86 -0.93
87 -0.92
88 -0.92
89 -0.91
90 -0.90
91 -0.89
92 -0.88
93 -0.87
94 -0.86
95 -0.85
96 -0.84
97 -0.83
98 -0.83
99 -0.82
100 -0.82
101 -0.81
102 -0.80
103 -0.78
104 -0.76
105 -0.73

Sorry couldn't get a smaller pic to work! Are these the correct #'s to add to my raw #'s using the 33-4050. Also any fast link to full #'s from 10-20k please. I see #'s for the OLD RS but having trouble finding full chart for the NEW rs analog. Thanks

I have RS meter 33-2050. Do these files work with it? I use my meter with REW often. However, obviously, I don't believe it is completely accurate, because I don't know how to "load" or "import" or whatever these files. How do I apply these cal numbers to my meter? Do I "import" them as txt file? Please direct me to a post that explains how to apply these correction files, tables, or whatever you guys are calling them to my REW/RS SPL setup. I'm frustrated because I can't find the info anywhere.

I have RS meter 33-2050. Do these files work with it? I use my meter with REW often. However, obviously, I don't believe it is completely accurate, because I don't know how to "load" or "import" or whatever these files. How do I apply these cal numbers to my meter? Do I "import" them as txt file? Please direct me to a post that explains how to apply these correction files, tables, or whatever you guys are calling them to my REW/RS SPL setup. I'm frustrated because I can't find the info anywhere.


If you have REW, go to Home Theater shack to the download section. They have updated numbers that you can download and save in REW so that the changes are done automatically.

Thanks very much. JohnPM posted on another thread and walked me through it. Thanks again.

Radio Shack "SPL" Meter Characteristics
As I wrote in another forum.
The June 2007 issue of Audio Xpress magazine has a 4 page article by Daisuke Koya:
"Radio Shack Sound Level Meter Characteristics"
Although I don't agree with his protocol, it's still interesting reading.

Radio Shack "SPL" Meter Characteristics
As I wrote in another forum.
The June 2007 issue of Audio Xpress magazine has a 4 page article by Daisuke Koya:
"Radio Shack Sound Level Meter Characteristics"
Although I don't agree with his protocol, it's still interesting reading.

Is a link to the article available? I couldn't find one without signing up. Would be nice if you could link your comment to a readable article. Scanned would do as well.

EDIT:

Got it. Link (http://www.audioxpress.com/magsdirx/ax/addenda/media/koya2811.pdf)

Quick question. Do I need to use correction values if im simply just using the RS SPL meter as a mic for Room EQ Wizard?

Did any of you calibrate your system using the receiver test tones and Radio Shack SPL Meter?

If so, did you calibrate everything at 75db, including the sub? Is it true that the SPL meter doesn't pick up low frequencies well so you need to calibrate the sub hotter (i.e. 85db or more?)

Quick question. Do I need to use correction values if im simply just using the RS SPL meter as a mic for Room EQ Wizard?

You can use a .cal file in REQ that automatically adds the correction values.



Did any of you calibrate your system using the receiver test tones and Radio Shack SPL Meter?

If so, did you calibrate everything at 75db, including the sub? Is it true that the SPL meter doesn't pick up low frequencies well so you need to calibrate the sub hotter (i.e. 85db or more?)


Yes, 75dB for receiver tones. To compensate for the meter being less sensitive at lower frequencies, adjust 1~3dB below 75dB if you want it even. If the meter says 75dB, you're at about 76~78dB.

And because of the meter is most accurate at the neutral point (70, 80, whatever you set it to), it might be easier to find the -5 point on your volume dial (may be -5, or 22, or wherever), and calibrate to 70dB.

What hz is the subwoofer setup noise in Avia?

I think it's 40~80Hz.

Hello, maybe im thinking or trying to hard with my RS SPL and Rives disc. Im not sure if i have the old or new analog RS SPL or if the old is analog and new would be digital??? So if someone could plz help with what #,s i would need to +- to/from my samples i have taken. Im using an RS Analog SPL bought it 4 months ago and the Rives disk tracks 32-62. A simple wich post here (Name/Date posted) #'s to use would be fine to. Thanx for any help and sorry if i seemed confused I am :) Edit= OK searched alot more now i know i got the NEW anolog meter 33-4050 so is there any correction tables needed for this or has Rives realy done all the compensation needed if i use tracks 32-62 ?I haven't visited this thread in a looong time. However, the "corrected" sections that are on the Rives CD 2 disc are supposed to have been corrected for the RS #33-4050 meter. This is the meter that this thread is referring to.

The subsequent information in the latter half of this thread, should be updates. As you know, each meter has slightly different response characteristics. Remember that to make the correct measurements, the meter should be placed at the listening position (preferrably on a tripod - vibrations through your body will effect the low frequency response) and pointed straight up. Pointing it towards the front of the room (even slightly) will result in inaccurate measurements.

BTW, the "old" RS SPL meter, that I also have, is the #42-3019. There is also an even older model (real klunky looking), but it doesn't have a model number on it (except for a "No. 3110711" on a tag on the bottom of mine - labled "Realistic SPL").

http://www.audioxpress.com/magsdirx/ax/addenda/media/koya2811.pdf

That's an interesting article. My "old" model (the 42-3019) is apparently a slightly older version of the 33-2050 (Fig 2) pictured in the article, but it looks the same.

Here is a picture of my really old RS SPL meter:

These are for the current digital meter used as a microphone.

10 -5.66
11 -5.25
12 -4.66
13 -4.20
14 -3.80
15 -3.50
16 -3.30
17 -3.10
18 -2.90
19 -2.70
20 -2.50
21 -2.30
22 -2.10
23 -1.95
24 -1.80
25 -1.60
26 -1.40
27 -1.15
28 -1.00
29 -0.90
30 -0.75
31 -0.65
32 -0.55
33 -0.44
34 -0.33
35 -0.22
36 -0.11
37 0.00
38 0.08
39 0.15
40 0.22
41 0.34
42 0.36
43 0.41
44 0.45
45 0.49
46 0.52
47 0.55
48 0.59
49 0.60
50 0.62
51 0.64
52 0.64
53 0.64
54 0.63
55 0.62
56 0.60
57 0.59
58 0.56
59 0.53
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 0.37
78 0.38
79 0.39
80 0.42
81 0.42
82 0.43
83 0.43
84 0.43
85 0.43
86 0.43
87 0.44
88 0.45
89 0.45
90 0.46
91 0.46
92 0.47
93 0.48
94 0.48
95 0.49
96 0.49
97 0.50
98 0.50
99 0.50
100 0.50
101 0.50
102 0.50
103 0.50
104 0.50
105 0.50

I am quite confused. Are these the corrections that I should use when taking measurements with my SPL model 33-2055 SPL meter, C-weighted?

My onkyo HT-R510 is currently what I use to set up the sound, with its pink noise. I set up the SPL meter where I sit, set all the adjustments on it correctly and then turn up the volume (0-75, higher number = louder) on my amp until the Meter reads 75db. All amp settings are at 0db when I start. It starts with the left speaker and then goes all the way around. The left speaker is what as a reference to adjust the others. The Subwoofer reading has always been out of wack, never knew how to get that right. After I read through this though, seems like it should be set to 85db, correct? Also, what Hz is the onkyo test tones putting out, so that I can set the meter accurately according to the charts posted in this thread? Thanks in advance.

http://www.smr-home-theatre.org/Sub-woofer-Set-Up/Sub-woofer-Information.html

I have read the entire post and would like to achieve a more uniform and deeper low end from my subs. I have the analog rs meter, I do not have access to a laptop computer. Am then out of luck with the correction tables?

From one of the first posts on the SVS site FAQ

So find out what your subwoofer(s) are REALLY doing, and add the following numbers as appropriate to your SPL meter readings:

At 10Hz add 20dBs to the meter's readings and at ...

12Hz add 16.5dB
16Hz add 11.5dB
20Hz add 7.5dB
25Hz add 5dB
31.5Hz add 3dB
40Hz add 2.5dB
50Hz add 1.5dB
63Hz add 1.5dB
80Hz add 1.5dB
100Hz add 2dB
125Hz add .5dB

This excerpt is valid for the spl meter I own. Also in this thread they mention equalizers that will adjust at this low frequency. I think that possibly I can save the time and effort of selling my existing sub(s) for a new model and tweak what I already have to achieve a bit lower response. Two equalizers were mentioned a Rane and another brand. If the cost is less than a new sub which it should be that is the avenue to explore I think.

The chart above reads in part, at 10 hz add 20 db to the meter's readings etc.

Does this mean if the meter is reading a steady 75db as compared to the other speakers it is actually 95db?
Or I have to add 20db at that frequence level?

If I could borrow/rent a lap top, I understand it is a free program that is then loaded with the correction values. Is the RS spl meter then connected to the laptop?

Could someone in layman's term explain to me what I need to do for accurate results?


I just calibrated my system. Set the meter to 70, set the volume on my receiver so the needle hovers around 0db. I then adjusted everything to the +5db setting. Supposedly I'm at 75db for my speakers, and my sub is 85db at my reference level.


What do I need for more accurate results?

Could someone in layman's term explain to me what I need to do for accurate results?


I just calibrated my system. Set the meter to 70, set the volume on my receiver so the needle hovers around 0db. I then adjusted everything to the +5db setting. Supposedly I'm at 75db for my speakers, and my sub is 85db at my reference level.


What do I need for more accurate results?

All you need to do now is turn down your sub's volume so that the sub also reads at 75db. The +10db compensation for the sub is already taken care of by your amplifier/receiver, in other words your running your sub too hot.

Looks like my last post was one of the "lost" ones. I bought the RS 33-4050 yesterday and did a room test. I applied the dB adders from post #70 here. I generated an Excel file with results. Is there a way to change the x-axis of an Excel graph to log? I attached the file here, zipped because .xls won't upload.

Looks like my last post was one of the "lost" ones. I bought the RS 33-4050 yesterday and did a room test. I applied the dB adders from post #70 here. I generated an Excel file with results. Is there a way to change the x-axis of an Excel graph to log? I attached the file here, zipped because .xls won't upload.


Under custom types you can set it up for log. Your's seemed to do the y-axis instead of the x-axis. Doublecheck your setup. HTH

I know there are a few of these out there but I made a really useful Excel sheet that is RS meter corrected, as most of these sheets do. But, you can remove or, put in any offsets you want for 3 different logs (3 full frequency sweeps). Mine is REALLY useful because it plots all 3 pages of logged sweeps on 1 graph for comparison. I have a notch filter in my receiver and I wanted a start graph line (before tweaking) for reference to make sure I am getting the results I want and not affecting other things. With my sheet you can record all your readings (start, change 1 and change 2) and see exactly what you did and if you got the results you were looking for. Good Luck and happy tweaking.

I need a MIC for ROOMEQ....I know very little about them and wanted to get some recommendations. I thought maybe I'd look on ebay for one. Is there such a thing as a $20 MIC from a local guitar/music store and it be good enough for calibration purposes?

I need a MIC for ROOMEQ....I know very little about them and wanted to get some recommendations. I thought maybe I'd look on ebay for one. Is there such a thing as a $20 MIC from a local guitar/music store and it be good enough for calibration purposes?

least expensive one I know of is the mic within the Radio Shack SPL meter ($40), but thats not the best for full range, but good enough for sub to speaker calibration. Typically, if you want something better, you are in the 120$ range. ECM8000 Behringer Mic $50 + XLR Mic cable $15 + Eurorack UB802 60$ (for phantom power).

If you want something for PEQ purposes, you will have to go the more expensive route. If you want something just to get subwoofer level matched to Speakers, you only really need the Radio Shack SPL meter.

least expensive one I know of is the mic within the Radio Shack SPL meter ($40), but thats not the best for full range, but good enough for sub to speaker calibration. Typically, if you want something better, you are in the 120$ range. ECM8000 Behringer Mic $50 + XLR Mic cable $15 + Eurorack UB802 60$ (for phantom power).

If you want something for PEQ purposes, you will have to go the more expensive route. If you want something just to get subwoofer level matched to Speakers, you only really need the Radio Shack SPL meter.

Ok..I got the RS digital meter. I was just thinking I needed to use a microphone in order to use the REW program for room response. I'm just bored looking for a project itching to spend money on something. :)

Ok..I got the RS digital meter. I was just thinking I needed to use a microphone in order to use the REW program for room response. I'm just bored looking for a project itching to spend money on something. :)

For normal sub/speaker level matching, your meter will do fine.

If you want to take like 10hz-20khz sweeps, you want a mic like I listed (110$ overall though). RS Meter can do it, but it is not very accurate below 50hz and above 6khz. Using cal numbers is kind of gray area as well because those cal numbers arent for your exact RS meter, there are variances between meters.

The value of doing full sine sweeps would be to see that your room sucks acoustically just like 'everyone' else's (most likely). It will show you big problem areas and that you may want to invest (more money) in room treatments and bass PEQ. The values from 10-80hz will help immensely for pin-pointing PEQ settings.

Doing that sweep will lead to you spending quite a bit more money. Sometimes ignorance is bliss? HAHAHAHA. Its a long journey, my friend. But, it can be great fun in terms of balance between academics, hobby, and the all important "smile on one's face" at the end of the day.

ECM8000 Behringer Mic $50 + XLR Mic cable $15 + Eurorack UB802 60$ (for phantom power).

So if we get the Behringer Mic and XLR cable and UD802/502 mixer, don't we still need an upgraded sound card?

I'm going this route to be able to do good full frequenncy sweeps but one thing I didn't figure on was the external sound card to connect the Mixer/Amp through. Do you use the RCA output/inputs of the UB802 connected to the laptop sound card? If so then the only one I've seen with RCA in/out was the SoundBlaster MP3+. IS there any others that have RCA ins/outs?

So if we get the Behringer Mic and XLR cable and UD802/502 mixer, don't we still need an upgraded sound card?

I'm going this route to be able to do good full frequenncy sweeps but one thing I didn't figure on was the external sound card to connect the Mixer/Amp through. Do you use the RCA output/inputs of the UB802 connected to the laptop sound card? If so then the only one I've seen with RCA in/out was the SoundBlaster MP3+. IS there any others that have RCA ins/outs?

It works with my desktop's Creative Audigy 2ZS card. I do a 1/8" from the sound card Line IN to 1/4" Output of the mixer. The Behringer does a XLR between itself and the Mixer. My mixer does not use the RCA, it uses the 1/4 headphone adapters. I understand that Parts Express has updated their mixers, but I dont know the details of those updates.

To calibrate SPL level, I just hold the SPL meter for pink noise. Thats all I use my RS meter for now.

It works with my desktop's Creative Audigy 2ZS card. I do a 1/8" from the sound card Line IN to 1/4" Output of the mixer. The Behringer does a XLR between itself and the Mixer. My mixer does not use the RCA, it uses the 1/4 headphone adapters. I understand that Parts Express has updated their mixers, but I dont know the details of those updates.

To calibrate SPL level, I just hold the SPL meter for pink noise. Thats all I use my RS meter for now.

You said your "my mixer does not use the RCA" but since the UB802 does have RCA in and out, it could be used, couldn't it?

I'm gonna get a ECM8000 and XLR cable into the mixer. Then use the RCA's into a laptop USB sound card inputs. Then the sound card rca outputs would feed into my pre-pro aux inputs >> amplifier >> speakers.

Does this sound correct?

You said your "my mixer does not use the RCA" but since the UB802 does have RCA in and out, it could be used, couldn't it?

I'm gonna get a ECM8000 and XLR cable into the mixer. Then use the RCA's into a laptop USB sound card inputs. Then the sound card rca outputs would feed into my pre-pro aux inputs >> amplifier >> speakers.

Does this sound correct?

Could be, but if you want to make sure, check out this hometheater shack. That forum supports REQW and has helpful information for getting it to work with the mic and the UB802 (amongst other things)

link (http://www.hometheatershack.com/forums/rew-forum/) I learned everything from that site, and found it very helpful. I haven't had to calibrate my system for a year and a half, so my memory is a little foggy. I just noticed that it has RCA Tape input and output. I happened to use the 1/4" though.

Is there anything new on this front that can be added to THIS (http://www.avsforum.com/avs-vb/showthread.php?p=10118822#post10118822) thread?


Thanks In Advance.

Just in case anyone is interested, recently I "blew" my RS Digital SPL Meter via a static electricity discharge. I was going to toss it out, but I decided to "repair" it. The mike element went bad, so I replaced it.


Now, the interesting part. A few days after I repaired the SPL meter, I thought that with all the so called calibration files out there how much of the error is electronic and how much of it is mike related.


Here is the answer. I removed the mike, and swept the electronics via True RTA (1/24 octave no smoothing). Green is C scale, Red is A scale. This proves that the basic filters are pretty accurate A scale and C scale filters.


The accuracy of the mike used in the SPL meter determines SPL meter "accuracy" relative to the well known electronic A scale and C scale filters in the SPL meter.


http://hyperphysics.phy-astr.gsu.edu/hbase/sound/acont.html#c1

.

If you are measuring max SPL LFE peaks with the meter set to "C" and "fast" response, is the meter still off and needs to have the SPL Meter Correction Table value applied assuming you know the freq the bass peak you are measuring is at?

For example lets say I am taking a LFE peak measurment of a movie scene that the bass is centered about 40hz and I read 115db on the meter would this actualy be a 117.5db LFE peak since the meter is down 2.5db at 40hz and you would need to add this 2.5db to 115 to get your true measurement which would be 117.5 in this case?

This is apparently the accepted response for the radioshack 33-4050 analog meter (and the 33-2055 digital meter as well).
(Taken from Home Theater Shack forum / REW RADIOSHACK-33-2055_4050.cal file.) I am just posting this for quick and easy reference...

Hz dB (so, for example, add 16.91 dB to a meater reading taken at 10Hz to obtain the actual level)
7 -27
8 -22.55
9 -19.37
10 -16.91
11 -15.27
12 -13.74
13 -12.42
14 -11.33
15 -10.28
16 -9.28
17 -8.53
18 -7.86
19 -7.12
20 -6.56
21 -6.18
22 -5.77
23 -5.41
24 -5.1
25 -4.9
26 -4.54
27 -4.27
28 -4.03
29 -3.73
30 -3.53
31 -3.25
32 -3.04
33 -2.84
34 -2.61
35 -2.54
36 -2.44
37 -2.28
38 -2.13
39 -1.97
40 -1.8
41 -1.75
42 -1.6
43 -1.54
44 -1.51
45 -1.43
46 -1.34
47 -1.23
48 -1.12
49 -1.02
50 -0.9
51 -0.82
52 -0.68
53 -0.64
54 -0.58
55 -0.5
56 -0.46
57 -0.38
58 -0.37
59 -0.36
60 -0.35
61 -0.34
62 -0.33
63 -0.32
64 -0.31
65 -0.31
66 -0.31
67 -0.22
68 -0.22
69 -0.23
70 -0.23
71 -0.19
72 -0.19
73 -0.17
74 -0.1
75 -0.1
76 -0.07
77 -0.06
78 -0.03
79 -0.01
80 0.00

And from 80 Hz out to 200 Hz (in 1 Hz steps) the values are all listed as 0.00.

Man this thread gives me a headache the more I re-read it! :D

What are the currently accepted correction values for the Radio Shack RS-2055 digital SPL using the meter as a standalone unit? i.e. I am reading the values from the LCD display on the meter.

I think the values in my post just above are the corrections you are looking for, although I'm not sure what to do above 200 Hz yet.

Hai I am new to this site. I am unable to understand the topic on which the comverstion was going on.

ToTo Man, try these:

LF corrections for Radio Shack 33-2055 meter
These are for the current digital meter used as a microphone.

10 -5.66
11 -5.25
12 -4.66
13 -4.20
14 -3.80
15 -3.50
16 -3.30
17 -3.10
18 -2.90
19 -2.70
20 -2.50
21 -2.30
22 -2.10
23 -1.95
24 -1.80
25 -1.60
26 -1.40
27 -1.15
28 -1.00
29 -0.90
30 -0.75
31 -0.65
32 -0.55
33 -0.44
34 -0.33
35 -0.22
36 -0.11
37 0.00
38 0.08
39 0.15
40 0.22
41 0.34
42 0.36
43 0.41
44 0.45
45 0.49
46 0.52
47 0.55
48 0.59
49 0.60
50 0.62
51 0.64
52 0.64
53 0.64
54 0.63
55 0.62
56 0.60
57 0.59
58 0.56
59 0.53
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 0.37
78 0.38
79 0.39
80 0.42
81 0.42
82 0.43
83 0.43
84 0.43
85 0.43
86 0.43
87 0.44
88 0.45
89 0.45
90 0.46
91 0.46
92 0.47
93 0.48
94 0.48
95 0.49
96 0.49
97 0.50
98 0.50
99 0.50
100 0.50
101 0.50
102 0.50
103 0.50
104 0.50
105 0.50

Hi,
I am trying to get the most current correction table for the Digital RS SPL meter to be used as a standalone unit. i.e not in combination with REW or anything similar. I have looked and found conflicting info. Is there kind of a consensus as to which correction table is the best/most current? Any help will be appreciated.

Hi,
I am trying to get the most current correction table for the Digital RS SPL meter to be used as a standalone unit. i.e not in combination with REW or anything similar. I have looked and found conflicting info. Is there kind of a consensus as to which correction table is the best/most current? Any help will be appreciated.
Does it really matter? The unit to unit variations are large. The meters have been manufactured for a long, long time. All stages of the manufacturing process may have changed several times. It's difficult to keep tight tolerances on the mic capsule element (some of the higher priced calibration mic manufactures get lots of mic capsules and select the best ones). Also the mic elements drift with time, temperature and humidity.

Wow that far off for cheap Realistic Tandy analogue SPL metre. I’ll think I’ll use the RTA instead.

Im plan on getting a radioshack meter soon but im a little confused about how it works.

Why is the meter readings not accurate? how do i know what to add or subtract? i want to calibrate my speakers and if i understand correctly there all suppose to read 75db spl including the sub?
since the meter is not accurate how do i know if its the right number?

And what direction do i point the mic, i have a tripod should i use that?

Is it ok to the receives test tones?

I’ve been using the nifty little thing at the cinema for basic reference like the Empire Leicester Square because its so superior over six-million dollars!:rolleyes:

I'm about to dive into the world of manual calibrations which means I have a dumb question. Uh....how do I know what hz the test tone on my denon 989 is for the sub (I don't need to correct anything for the speakers do I?). Or do you guys just use a CD containing different tones? And whats the consensus for analog vs digital meters?

I went to my local radio shack which is called the source now and was looking to buy a spl meter. The only one they had was a scosche boomstick spl1000 digital meter. Has anyone tried these and know how accurate they are?? I couldn't find an analog version. Which one should I get?? Thanks

Is there a correction table for the Galaxy CM-140 or am I good to go out of the box?

There are files based on other user's units, but you should understand that there are within model variances that limit the usefulness of such data.

If you want references, you need to buy a calibrated mic or have a mic or meter calibrated or profiled so that the data is valid for your unit.

Which correction table is one to use? I just looked at several for the same RS Meter, and the correction values are all very different on each link.

anyone know what to compensate for above 100hz? with the newer spl meters

I have a digital Radioshack meter.

It must be at least ten years old and it's model number is 33-2055.

What correction values do i use for this particular model ?

ToTo Man, try these:

LF corrections for Radio Shack 33-2055 meter
These are for the current digital meter used as a microphone.

10 -5.66
11 -5.25
12 -4.66
13 -4.20
14 -3.80
15 -3.50
16 -3.30
17 -3.10
18 -2.90
19 -2.70
20 -2.50
21 -2.30
22 -2.10
23 -1.95
24 -1.80
25 -1.60
26 -1.40
27 -1.15
28 -1.00
29 -0.90
30 -0.75
31 -0.65
32 -0.55
33 -0.44
34 -0.33
35 -0.22
36 -0.11
37 0.00
38 0.08
39 0.15
40 0.22
41 0.34
42 0.36
43 0.41
44 0.45
45 0.49
46 0.52
47 0.55
48 0.59
49 0.60
50 0.62
51 0.64
52 0.64
53 0.64
54 0.63
55 0.62
56 0.60
57 0.59
58 0.56
59 0.53
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 0.37
78 0.38
79 0.39
80 0.42
81 0.42
82 0.43
83 0.43
84 0.43
85 0.43
86 0.43
87 0.44
88 0.45
89 0.45
90 0.46
91 0.46
92 0.47
93 0.48
94 0.48
95 0.49
96 0.49
97 0.50
98 0.50
99 0.50
100 0.50
101 0.50
102 0.50
103 0.50
104 0.50
105 0.50

Ignore the above post if these are the correct values ( i need to read more of the posts )