Spectra1 Users Manual

Thank you for using Spectra1!

Spectra1 is a real-time audio spectrum analyzer that operates in full stereo.

It is designed to monitor, in real-time, audio signals that are routed through your personal computer’s soundcard.

The Interface…

Spectra1’s primary interface (or GUI) is broken into 3 major components.

1 – This area is the primary spectrum analyzer display.

2 – This area is called the waterfall spectragraph. It display frequency changes in time as bands of lighter and darker areas.

3 – This area is the primary controlling area for adjusting specific analyzer settings.

- FFT Window

The FFT window type selects the kind of smoothing window the Spectra1 will use to process frequencies.

- Average Hold

Average hold checkbox allows you to turn on and off the graphical line display that indicates the average spectrum currently in play.

- Peak Hold

Peak hold checkbox allows you to turn on and off the graphical line display that indicates the peak spectrum currently in play.

- Peak Bars

The peak checkbox allows you to switch from a graphical line display or to a graphical bar display.

- Peak Hold Speed

This slider can be adjusted to change the speed of how fast the peak hold indicators reset.

- Fade Rate

This slider can be adjusted to change the speed of how fast the spectrum updates its display bars.

- Start/Stop

This button is used to start and stop the real-time display.

4 – This is the gain slider. You can use this to artificially amplify the signal going into Spectra1.

Setting up Spectra1

The primary location for changing settings for Spectra1 is located in the Options menu, under Settings:

By selecting “Settings…” the following window pops up:

At this window, you want to be sure that the soundcard that you intend to use is selected. Also, you must select the sampling rate you wish to record in. Spectra1 requires the sample input to be at least 44,100hz or 48,000hz. This minimum frequency was selected because of a fundamental rule of digital audio (Nyquist theorem) which states that the highest accurate frequency reproduction is determined by the sample rate, divided by two. In this case, the minimum frequency of 44,100hz yields a maximum high frequency reproduction of 22,050hz. If the sample rate was lower, we would not be able to analyze the higher frequency content of our audio, and the upper frequency bands of Spectra1 would be rendered useless.

FFT Window Size is the amount of samples that Spectra1 uses to analyze the sound stream. Because of the way FFT works, this is always a power of two. The larger the FFT window size, the better resolution you will have with lower frequencies. However, too large of a window could result in choppiness of the display, due to the large amount of data required to process each frame. The default window resolution of 4096 should usually be just fine for standard analyzer activity.

Selecting the audio input line…

Spectra1 uses the windows recording mixer to monitor audio. It is important to have the right input selected to analyze.

To select the proper record line, you need to select “Options” from the file menu, and the “Select Record Line…”.

This should bring up the Windows record mixer (note that the windows mixer controls are also usually available by double clicking on the volume control icon in your task tray):

The box surrounding the “Select” checkboxes, are the actual Windows record selection mechanisms. By selecting a checkbox, you are selecting the record line that Spectra1 will use. For instance, “Line in” represents the actual line in of the computers sound card. Input gain may be adjusted with the sliders.

If you wish to analyze the spectrum of an MP3 or a WAV file from another player, you would want your input line to be the global mix line, “Stereo Mix”, or “Wave Mix”, or “What-U-Hear”. Some sound cards may have the global mix labeled as something different. If the recording line you want does not appear in the Windows mixer, by selecting “Options”, and then Properties (in the Recording Control window), you can make sure your recording line is available and selected, and that the mixer device is actually the sound card you intend to use.

If the record line volume level becomes too high, you may notice a clip light display on Spectra1’s main window:

When this occurs, you can try to eliminate the clipping by lowering the slider in the Windows Mixer (recording control) for the selected record line.

Attaching To A Recorder

There are usually many ways to allow Spectra1 to monitor in real-time a feed from a multi-track unit. One common way to do this is by attaching a cable from an Aux Out channel of the multi-track, and into your PC’s line in. This way, when you want to monitor the spectrum of a particular track, you simply turn up the Aux Send of that track, which feeds the signal to your PC so Spectra1 may examine it. This is particularly handy when the spectrum analyzer of your multi-track may take up one of your valuable effects processing systems.