Simple audio system tuning

HouseCurve Manual

  1. Main Screen
  2. Plot Area
  3. Setup Screen

Main Screen

housecurve main screen controls

Page Control

HouseCurve displays measurements on power, phase and group delay plots. Tap the page buttons to move between plots. Alternatively, swipe from the left or right edge of the screen to change plots.


Tap for Help screen


Tap for Setup Screen screen


Tap the Measure button to start measurement process. Tap again to to stop. This button is disabled when not connected to an audio system.


Tap the Undo button to discard the most recent measurement. This button is disabled when there are no measurements.


Tap the AirPlay button to select from available AirPlay and Bluetooth audio outputs. The analog (wired) output is automatically selected when something is plugged into the iPhone/iPad headphone connector. See connecting to an audio system.


Tap to discard all measurements.

Save overlay

Tap to create an overlay from a measurement. This button is disabled when there are no measurements on the plot.

Plot Area

housecurve plot area

Selected Reference Curve

The selected Reference Curve is displayed on the power plot in yellow with +/- 3 dB bands.

The phase and group delay plots always have a reference of zero.

Selected Overlay

The selected Overlay is displayed in grey. The name of the overlay is displayed in Setup Status.


Measurements are displayed on the plot in green.


Tap plot area to show cursor, move with a single finger, tap again to hide.

Measurement Status

HouseCurve displays the status of the measurement process in this area. The status disappears after a few seconds.

Setup Status

HouseCurve displays setup information in this area. The status disappears after a few seconds.

Plot zoom / scroll

To zoom into a plot, pinch anywhere on the plot area. The plot can be scrolled left or right with two fingers.

Plot zoom and scroll only change the horizontal frequency axis. HouseCurve automatically sets the vertical axis of the plots to show the measurement.

Setup Screen

Display Mode

HouseCurve can display measurements to suit a given task.

Average mode (default) is used to capture how an audio system sounds in a listening area. Use this mode when tuning the audio system to match a reference curve.

History mode is used to see the effect of an adjustment from a single microphone location. Use this mode for initial audio system setup, such as speaker position or time alignment.


Smoothing can be applied to measurements to make it easier to see trends. The selection is applied to all measurements and the selected overlay. To remove smoothing, select None.

Coherence Blanking

Coherence blanking hides portions of the measurement that are low quality and should not be used for tuning.

Blanking occurs wherever the measurement falls below the selected signal to noise ratio (blanking threshold). To disable blanking, select Off.

This setting also controls the threshold at which HouseCurve will automatically discard measurements.

Frequency Scale

The frequency axis can have an Octave or Decade scale. This setting applies to all plots.


Overlays are used to display a previous measurement on the plot for comparison. Available overlays will be displayed in the list. Select None to disable overlays.

Overlays can be created from the main screen or by tapping + at the top of the Overlay screen. If an overlay with the same name exists, it can be overwritten. Overlays can be removed by tapping Edit.

Overlays are created from available measurements based on the Display Mode. In Average mode, the average measurement is used. In History mode, the most recent measurement is used.

When an overlay is created, it will appear underneath the measurement it is based on. The overlay will remain on the plot for all subsequent measurements.

Reference Curve

A Reference Curve is displayed on the power plot to serve as a guide for tuning an audio system.

The curve is positioned on the power plot based on the Reference Curve Fit setting.

HouseCurve ships with some common reference curves. Additional reference curves can be loaded by tapping + at the top of the Reference Curve screen. Reference curves can be removed by tapping Edit.

Reference Curve Fit

By default, the selected Reference Curve is automatically fitted to measurements based on the Display Mode. In Average mode, the average measurement is used. In History mode, the most recent measurement is used.

Coherence Blanking also affects how the Reference Curve is positioned. Portions of the measurement below the blanking threshold are ignored for fitting.

When automatic fitting is disabled, the curve can be manually positioned by setting a desired dB level at 100 Hz. This is useful when separately adjusting speakers to a common reference level, such as main speakers and a subwoofer.

Chirp and Sweep Channel

The “chirp” and “sweep” sounds of the test signal can be played on different channels (see measurement process). This is mainly used for subwoofer measurements.

Internal Mic Compensation

The built in iPhone/iPad microphones have a reasonably flat response and are quite acceptable for tuning an audio system. However, when compared to an external calibrated microphone, they do show some roll off at the extreme ends of the frequency spectrum.

Internal Mic Compensation applies a moderate boost below 60 Hz and above 16 KHz to measurements made with the built in iPhone/iPad microphone.

External Mic Calibration

HouseCurve supports calibrated external microphones. Available calibrations will be displayed in the list. Select None to disable calibration.

Microphone calibrations can be loaded tapping + at the top of the External Mic Calibration screen. Calibrations can be removed by tapping Edit.

HouseCurve supports the following Curve file format.

Stimulus Type

Stimulus Type controls the test signal used to measure the audio system.

In most cases, the Sine Sweep should be used as it will produce measurements with a higher signal to noise ratio. In this mode, HouseCurve requires a connection to the audio system in order to play the test signal.

External Sine Sweep mode does not require a connection to the audio system. Instead, the test signal must be manually transferred to the audio system (ex: using an SD card). During the measurement process, the audio system is responsible for playing the test signal and HouseCurve listens for it.

The test signal can be exported to a WAV file when this mode is selected. Note - chirp and sweep channel setting will be used to produce the test signal file.

Pink Noise is provided for interest sake. Measurements based on pink noise will have a lower signal to noise ratio.

HouseCurve uses coherent averaging. This has an interesting effect on Pink Noise measurements. In a sonically treated room, such as one with sound absorbing panels on the walls, Pink Noise noise measurements will closely match Sine Sweep measurements. In a more typical “reflective” room, Pink Noise power measurements tend to be lower above ~2 KHz. The degree to which the Pink Noise and Sine Sweep measurements match is an indication of how “dead” the room is.