Sound System – Stereo and Surround

This wizard will guide you through a full sound calibration of your stereo or home theater system.

For more details and guidelines on 5.1 systems, click the help button to view "The Dolby Laboratories Guide to Home Theater Sound".

You will need Adobe Acrobat Reader to read this document (www.adobe.com).

The loudspeaker positioning is very important to obtain the best sound quality.

You should measure at all potential loudspeaker positons in order to find the best position.

If you are measuring a surround system, the help document in the previous wizard step gives you useful tips on the loudspeaker positioning.

Click help for an example on calibrating a studio. This is useful literature even if your room is not a studio.

If you have not already loaded the settings for your sound card, go to Setup→Load Sound Card….

Note: This will close this wizard and open the sound card wizard. You should reload this setup after you have finished setting up your sound card.

To measure the correct delay times of your sound system, the sound card must be able to measure the delay time.

(The problem is that for most sound cards the input latency is not the same as the output latency, and the difference is not constant from one measurement to another.)

If your sound card does not measure correct delay time and the sound card wizard does not give instructions, click help.

From now we assume the sound card is OK.

When calibrating the sound system, check that:

- the frequency responses of the loudspeakers are even and matched

- all loudspeakers play at the same sound level (relative or absolute)

- all loudspeakers are connected with correct polarity.

- all loudspeakers are synchronized with respect to time arrival at the listener position

Place the microphone at the listening position in ear-height, about 1.2 meters (4 feet) above the floor. Mount the mic. on a stand and point it straight upwards (some mic. types require a proper mic. stand to prevent low frequency rumble via the stand.)

Connect the microphone cable to the sound card input. If using a separate mic. amplifier, use the sound card line input, left channel.

If your mic. is not flat you may correct for this . TODO: Click the Help button below for more information.

Your A/V receiver will normally have RCA(phono) inputs as shown in the picture. If there are no external decoder inputs, use the CD or AUX inputs instead.

Turn down the volume. Connect the left output channel of your sound card to the left channel (main) on your receiver. The subwoofer must be turned off.

Make sure that any signal delay or processing is turned off on your A/V receiver.

(When connecting balanced-unbalanced devices, tie low to ground.)

If the mixer in the wizard picture is shown, WinMLS controls the sound card mixer.

Use the faders to set the input and output levels.

If not, see next wizard step.

If the mixer looks like the upper part of the picture, WinMLS does NOT control the Window mixer and you should note the following:

It is not possible to set any levels from the mixer, it is used for monitoring only. Set levels either from your sound card software or hardware mixer.

To set the output level, go to Measurement→Settings…. Click the Levels tab shown in the bottom part of the picture.

Click help for more info.

Turn down the Receiver volume!

Press the blue TEST button.

Turn up the volume on your receiver. You should hear the test signal. Turn it up to a suitable level.

Adjust the input level to show between-40 dBFS and -3 dBFS.

Go to Measurement→Start to start a measurement.

Observe the levels. A red light on top of the meter indicates input level overload.

If this happens, lower the input (if possible) or output level and start again.

The next wizard steps will discuss the first measurement.

- The upper plot shows the frequency response.

- The left lower plot displays sound pressure level.

- The middle lower plot displays polarity.

- The right lower plot displays the time delay (the time it takes sound to travel from loudspeaker to microphone).

Observe the continuous line that represents the frequency response in the upper plot.

In a common room without any acoustical adjustments/treatments, the smoothed frequency response will normally not be flat (10–15 dB variation).

A major goal for the sound system calibration is to minimize this variation in the frequency response. An effective way of doing this is to change the loudspeaker positioning.

Move the loudspeaker and repeat the measurement, observe the plot.

Use this plot to compare the level of each speakers and adjust the levels so that they become equal.

Todo: It is clear recommendations for the level, insert these here.Insert picture

The bars in the lower middle plot display the speaker polarity.

All bars must have the same polarity (+ or -). In the picture, all bars have positive polarity (+).

It is difficult to measure polarity if the speaker is positioned near reflecting surfaces (floor, wall) and the mic is far from the speaker.

Therefore, if you are not sure you have the right polarity, move the microphone 10 cm (4 inches) in front of the speaker element when measuring.

Delay is the time it takes for the sound to travel from the loudspeaker to the measurement microphone. The bar in the lower right plot displays the delay.

For a stereo system, the delay for the left and right channels should be equal. If not, move one of the speakers or the listening position.

If you have a surround system, you should adjust the delay (or distance) internally within the A/V receiver to match each speaker. See the next three wizard steps for more information.

If your A/V receiver has internal delay settings for each channel, you can enter the delay measured with WinMLS.

This should be done when the speaker has different distances to the listening position.

It may not be possible to place your speakers in a perfect circle around you. And even if it is possible, this may not give the best results for the frequency response.

Some A/V receivers ask you to enter the distance in meters or feet instead of time delay in milliseconds (ms).

To change this, first click the Delay plot window to activate it. Then go to Plot→Plot Type Settings→Time Data….

Set the horizontal axis to Distance (meter) or Distance (feet) as shown in the picture.

Note: You may have to refresh the plot to apply the changes.

When the frequency response plot is active, the status bar (found at the bottom) will display the full, half and quarter wavelength of the cursor position as shown at the top of the picture.

This allows you to see e.g. at what wavelength a certain peak in the frequency response is found.

To switch to feet, go to Plot→Plot Type Settings→Time Data… and change m/s to ft/s as shown to the lower right in the picture.

You can save a measurement by clicking the apropriate button on the Measurement Panel toolbar.

Press the Left button as shown in the picture to save the measurement of the left speaker.

The measurements which are not assigned to the measurement panel can be removed using Plot→Erase Curve(s)….

Click help for more info.

You may rename the measurement panel buttons to fit the system you are calibrating.

Do this by clicking the … button shown in the picture.

Click help for more info.

You should now have achieved a good measurement of the main left speaker and saved it to the Measurement Panel toolbar.

Now turn down the output volume of your receiver to protect your speaker. Move the connection from channel L main to R main.

Repeat wizard steps 13-16 for the remaining speakers in your system (except the subwoofer which will be covered later).

Remember: When you have done a successful measurement, save it to the Measurement Panel button.

The picture shows a typical example of a left and right speaker measured in a studio. The frequency response curves should be as flat and similar as possible.

To obtain this, you may:1. Try different loudspeaker positions2. Change the listening position (if possible)3. Adjust the gain (volume) of each speaker so that the curves are equal in level (dBC).4. If available, apply equalizing to flatten the frequency response curve.

Click help for more info on measuring a studio.

A dedicated setup for positioning the subwofer is available. You may load this from Setup>Load…. Warning: If you do this, you will exit this setup.

Here we will measure how the subwoofer matches one of the main speakers.

Connect the left channel sound card output to mains (connect to L first, afterwards you can connect to R). Connect the right channel sound card output to the subwoofer input.

Start a measurement. You should hear sound from both the sub and the left main speaker.

The goal is to get an even transition between the subwoofer response and the other speakers. The red curve in the picture shows a good transition while the blue curve shows problems in the transition region between the subwoofer and the main loudspeaker.

To improve the transition, you can: 1. Move one of the speakers (if possible). 2. Switch the phase invert for the subwoofer. 3. Change available/relevant settings in your A/V receiver such as crossover frequency.

Note: The delay and polarity results for the subwoofer measurement should not be trusted.

You have now finished this wizard.

The following wizard steps are for special needs.

Some figures in this wizard are used by kind permission by Dolby Laboratories.

We thank all those that have contributed to this wizard, we'd like to especially mention:Andrew GoldbergJens Jørgen DammerudMika NiilonenTobias Kirchner

For surround systems, it is recommended to calibrate the microphone input since the volume should be set to 85 dBC at the listening position.

This is because movies are mixed at 85 dBC, and the frequency response of the ear depends on the level.

Calibrating the microphone input should be easy if you know the sensitivity of your microphone. You can also calibrate if using a sound calibrator.

Click help for instructions.