Calibrating Your Sound System with Diamond Cut Test CD's

[Craig Maier]

The following procedure can be used to flatten out (sometimes referred to as sounding out) your sound system and listening room using Diamond Cut Test CD #3. If you do not have this test CD, you can either purchase it from us at our online store located at www.diamondcut.com or make your own. To make your own, download AN3 - (Using DC5* or DC Live/Forensics To Create 3 Audio Test CD?s). Follow the procedure outlined in the Application Note to make your own using the Diamond Cut Software Make Waves Generator, etc.

*Note: DC 6 can also be used.

Additionally, you will need the following to set up a room with the Diamond Cut Test CD's:


1. SPL Meter having a "C - Weighting" (Radio Shack sells a good one at a reasonable price)

2. 1/3rd Octave Graphic EQ connected in line with the signal path of your sound system.

3. A High Quality CD player

4. An audio system to be calibrated

Procedure:

1. Set all controls on your stereo for flat.

2. Set all controls on the Graphic EQ for flat

3. Set up the SPL meter on a tripod near your normal listening location. Place it in "C - Weighting" mode which produces a maximally flat SPL meter response. Do not use "A - Weighting" because it rolls off its response below 500 Hz. You can use either the fast or slow response setting, whatever makes adjusting the system easier for you. I tend to use the slow response setting.

4. Play the following signal through your system found on Test CD #3:

1 Kilo Hertz Centered Narrowband Random Noise at a ?
6 dB Average Level

5. Adjust the loudness of your stereo so that the SPL meter reads 0 dB on one of its scales; a good choice is the 80 dB scale.

6. Now, using Test CD number three, play each of the following signals and adjust your 1/3 Octave graphic EQ so that each signal produces the same output SPL as read on the SPL meter. You will find that the lower frequencies will not be able to be reproduced at a "flat" level unless you have an enourmousely powerful sound system with a very large subwoofer. Do not worry about that and adjust it as best as possible nonetheless.

7. Proceed through all of the following signals on Test CD #3, adjusting each for an equal response on your SPL meter.

8. You will probably have to go through this process twice due to interactions between adjacent bands.

9. Done

--------------------------------------------------------------------

Signal Listing for Sounding Out a Listening Room

05 / 06

20 Hz Centered Narrowband Random Noise at a ? 6 dB Average Level

07 / 08

25 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

09 / 10

32 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

11 / 12

40 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

13 / 14

50 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

15 / 16

63 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

17 / 18

80 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

19 / 20

100 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

21 / 22

125 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

23 / 24

160 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

25 / 26

200 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

27 / 28

250 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

29 / 30

315 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

31 / 32

400 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

33 / 34

500 Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

35 / 36

630 Hz Centered Narrowband Random Noise at a ? 6 dB Average Level

37 / 38

800 Hz Centered Narrowband Random Noise at a ? 6 dB Average Level

39 / 40

1 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

41 / 42

1.25 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

43 / 44

1.6 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

45 / 46

2 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

47 / 48

2.5 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

49 / 50

3.15 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

51 / 52

4 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

53 / 54

5 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

55 / 56

6.3 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

57 / 58

8 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

59 / 60

10 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

61 / 62

12.5 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

63 / 64

16 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

65 / 66

19 Kilo Hertz Centered Narrowband Random Noise at a ? 6 dB Average Level

[Craig Maier]

Someone emailed me and asked where the 1/3rd octave graphic EQ should be connected. There are a number of options as follows:

1. Between your Pre-Amp (or Soundboard/Mixer) and your System Power Amplifier.

2. If you have a bi-amped or tri-amped system, connect the EQ between the preamp (or Soundboard/Mixer) and the input to the active crossover network.

3. If your preamplifier or receiver has an External Processing Loop (set of 4 conections - - - two inputs and two outputs), you can connect the EQ in that circuit.

4. You can connect the EQ in a tape monitor loop if your preamp or receiver has an extra one not being used.


If you do not have a 1/3rd octave EQ and do not want to purchase one but have an extra old computer available, consider using the Diamond Cut 30 band EQ operating in real time feedthrough mode. However, this alternative is only available if you own a copy of Live/Forensics. The DC6 version does not include a 30 band, 1/3rd octave graphic EQ.