Loudspeaker Measurement Import: Supported File Formats

FIR Designer and FIR Creator can import loudspeaker measurements in a variety of text based and binary file formats.

The files can be in the form of impulse response sample vectors or transfer functions (freq/mag/phase/coherence).

FIR Creator can import all the same file formats as FIR Designer.

Measurement averaging is an option within (only) FIR Designer; up to 200 imported measurements can be combined into a single measurement for use in filter design.

  MEASUREMENT RESAMPLING
The “Design sample rate” parameter doesn’t need to match the sample rate of any imported measurements & target responses.
The imported measurements & target responses are stored in their native form and sample-rate converted to the “Design sample rate” as necessary.
Learn More.

Klippel Impulse Response text (*.txt)

To load a loudspeaker measurement from Klippel’s dB-Lab software into FIR Designer….

In dB-Lab, open an “Impulse response h(t)” plot. Right-click on the plot and in the pop-up menu, select “Customise…”

Loudspeaker Measurement Import: Klippel dB-lab Impulse Response plot

In the “Impulse Response h(t) Customization…” Dialog, select the “Subsets” tab and select either “Measured” or “Windowed.” Press “Apply” and “Ok” to close the dialog.

Loudspeaker Measurement Import: Klippel dB-lab Impulse Response plot Customize

Rick-click on the plot and in the pop-up menu, select “Export & Print…” In the “Export Graph” dialog, select Export “txt (For excel import)” and To “File.” Press “Save…” to save the text file.

Loudspeaker Measurement Import: Klippel dB-lab Impulse Response plot Export

In FIR Designer, load the txt file on the “Import” tab.

Text (*.txt) and CSV (*.csv)

The following checks are run when importing text files.

  • If the file contains only 1 or 2 columns of numbers, the file is assumed to contain impulse response samples.
  • If the file contains 3 to 9 columns, the columns are assumed to start with frequency, magnitude, phase and optionally coherence.
  • If the file contains 10 or more columns, the 1st line is assumed to contain impulse response samples.

Values should be separated by a ” ” (space) or “,” (comma).

The decimal mark should be a “.” (dot, full-stop or period) and not a “,” (comma).

Optional comment lines, before the data, can begin with “#” or “/*” (without the quotes) and are ignored.

Columns Rows Data Description Comments
1 Impulse response samples (-1.0 to 1.0) See notes 1 and 2.
2 Column 1 : Ignored.

Column 2 : Impulse response samples (-1.0 to 1.0)

See notes 1 and 2.
3-9 Column 1 : Frequency (Hz)

Column 2 : Magnitude (dB)

Column 3 : Phase (degrees)

Column 4 (optional) : Coherence (0.0 to 1.0)

Columns 5 to 9, if present, are ignored.
1 Impulse response samples (-1.0 to 1.0) See notes 1 and 2.

Any subsequent rows are ignored.

Note 1: FIR Designer & Creator use the “Design sample rate” value at the moment of importing. After importing, the “Design sample rate” can be changed to the desired rate for the FIR filter design.

Note 2: The impulse response samples are loaded in one of two ways:

  • If the filename ends in an integer number, for example “my measurement 213.txt”, the number is used as the [zero-based] sample index for time=0. During importing, the measurement is time-advanced or shifted by the sample index. Also, the import process loads impulse response samples from N/2 samples before the sample index, or the first sample of the impulse response – whichever is closer to the sample index.
  • If the filename does not end in an integer number, the import process finds the sample index of the peak in the impulse response, then loads samples starting from 1500 samples before the peak, or the start of the impulse response – whichever is closer to the peak. Time=0 is assumed to be the first sample loaded; i.e. no time advancement or shift is applied.

This “filename ends in an integer number” is useful for maintaining time alignment of measurements when designing filters for a multi-way loudspeaker. To maintain relative time alignment between measurements (and prevent peak finding), ensure the filenames have the same integer number. (“0” is also valid.)

Wave (*.WAV)

FIR Designer & Creator can import 16, 24 and 32 bit integer, and 32 bit float WAV files.

Only the first channel is loaded. Other channels are ignored.

Note: The impulse response samples are loaded in one of two ways:

  • If the filename ends in an integer number, for example “my measurement 213.txt”, the number is used as the [zero-based] sample index for time=0. During importing, the measurement is time-advanced or shifted by the sample index. Also, the import process loads impulse response samples from N/2 samples before the sample index, or the first sample of the impulse response – whichever is closer to the sample index.
  • If the filename does not end in an integer number, the import process finds the sample index of the peak in the impulse response, then loads samples starting from 1500 samples before the peak, or the start of the impulse response – whichever is closer to the peak. Time=0 is assumed to be the first sample loaded; i.e. no time advancement or shift is applied.

This “filename ends in an integer number” is useful for maintaining time alignment of measurements when designing filters for a multi-way loudspeaker. To maintain relative time alignment between measurements (and prevent peak finding), ensure the filenames have the same integer number. (“0” is also valid.)

SysTune Overlay (*.sto)

SysTune overlay files contains measurement, reference and impulse response data along with metadata including the measurement sample rate.

The impulse response data is loaded as is; that is, with no time adjustment.

The coherence spectrum is also loaded.

(Since the SysTune impulse response is the result of a DFT/FFT calculation, the last 5% of the impulse response is moved to the end of the FIR Designer internal transform, to ensure the SysTune impulse response lead-in (prior to time=0) is maintained correctly.)

EASERA Measurement (*.etm)

EASERA ETM files contain various data elements and metadata; including the measured impulse data and the sample rate.

The impulse response data is loaded as is; that is, with no time adjustment.

(Since the EASERA impulse response is the result of a DFT/FFT calculation, the last 5% of the impulse response is moved to the end of the FIR Designer internal transform, to ensure the EASERA impulse response lead-in (prior to time=0) is maintained correctly.)

SMAART Trace (*.trf)

SMAART trace files contain various data elements including the complex spectrum.

The complex spectrum is loaded as frequency (Hz), magnitude (dB) and phase (degrees).

The coherence spectrum is also loaded.

Monkey Forest Measurement (*.spk)

Monkey Forest measurement files contain various elements including the complex spectrum.

The complex spectrum is loaded as frequency (Hz), real and imaginary data.

The file does not contain coherence.

FIR Designer Target (*.fdt)

This is an intermediate file format specifically for use in FIR Designer and FIR Creator. FIR filters can be designed in “Direct Design” mode, exported in this format, and re-imported on the Target tab in the default mode or workflow.

The format includes the sample rate and the bulk impulse response delay – the peak index of the FIR filter impulse response – so that the bulk delay can be removed.

This file format can be exported and imported even when FIR Designer/Creator is unlicensed; that is, when running trial or demo mode.


FIR Designer cannot directly import *.MDAT measurement files from Room EQ Wizard (REW).

In REW select “Export -> Measurement as Text” or “Export -> Impulse Response as WAV”, save the file, then import the *.txt or *.wav file into FIR Designer.