APx515B Series Audio Analyzer

Ideal for production test and entry-level R&D applications

APx515B Series Two-Channel Audio Analyzer

The APx515B Series is a performance audio analyzer optimized for production test. It is a best-in-class instrument, offering a powerful combination of speed, performance, automation, reliability and ease-of-use. It can make all key audio measurements in less than three seconds.

Despite its low cost, APx515 still has excellent performance, with a typical THD+N of –106 dB, 1.2M point FFTs and up to 216k digital I/O, as well as the one-click automation and ease-of-use of all APx B Series audio analyzers. Like all AP instruments, APx515 comes with an ISO:17025 Accredited Calibration and three-year warranty, so its results are trusted everywhere. The APx515 operates either as a stand-alone test unit with its own user interface, or it can be controlled by a master .NET or LabVIEW application. In either case, an operator can control the APx515 with a keyboard, foot switch or barcode scanner, or the system can be totally automated. Switchers and external devices such as pass/fail lights are also supported.



Multiple Simultaneous Input Types

APx500 software release version 6.0 brings the multi-input capability to APx, allowing engineers to activate a second input type on any APx modular audio analyzer, or APx515 analyzer, and make measurements simultaneously on analog and digital signals. This new capability, paired with the highest channel count and widest range of digital I/O available, provides APx users critical cross-domain insight and the opportunity to reduce testing time. Watch a Multi-Input Demonstration

Code-Free Automation and a Complete API

APx500 Measurement Software is the most advanced audio measurement interface available. Complex procedures that include user prompts, limits and calls to external applications can be created directly in the GUI, saving time and money while ensuring painless updates over time with no development required.

Create custom interfaces and application-to-application automation using the comprehensive APx API. Extensive documentation and examples are provided for Visual Basic.NET, C#, MATLAB, LabVIEW, and Python. Projects and automation can be shared with other APx units anywhere in the world.

Open-Loop Chirp

APx500 software enables open-loop measurements using the logarithmically-swept sine, or chirp, test signal. This signal provides multiple, high-resolution results in a brief period of time and now APx users can employ the chirp in test scenarios where the signal may originate, or terminate, as a file on the device under test (DUT) or on a server connected to the DUT. This capability is especially helpful to those developing smart devices (e.g., smart speakers, smartphones).

Use of the open-loop chirp capability with APx515 analyzers requires at least one software option or bundle that contain a supported chirp measurement (e.g., APX-SW-ACR, APX-SPK-RD).

Transfer Function

The transfer function measurement provides the complex frequency response function for a device, including the magnitude and phase (or real and imaginary components), using any broadband signal.

This feature, a powerful addition to APx software’s Sequence Mode, allows any APx analyzer to be used as a multichannel dynamic signal analyzer or as a so called dual-channel FFT analyzer. With transfer function and any broadband signal, including speech, music or noise, APx users can now assess the complex frequency response, coherence, and impulse response of their device or system.

AP’s transfer function provides gapless and overlapped analysis of multiple acquisitions. It also includes a ground-breaking signal-based triggering that eliminates the need for a pilot tone in open-loop test applications, making it ideal for test of “smart” audio devices.

Common Software Platform

APx audio analyzers use a common software platform, making tests and results easier to share. All settings for a test are saved in a single project file, making it easy to replicate test setups between R&D and production facilities anywhere in the world. Project files are compatible with both B Series and legacy APx instruments and each project is self-contained, so there’s never any worry about dependencies or broken links. Users can even embed waveform files and images within a project file.

For sharing measurement results with customers, contract manufacturers or management, APx automatically generates rich graphic reports, with highlighted pass / fail limits and options to export as PDF, HTML, Excel, CSV, RTF or MATLAB files.

Digital Protocol Analysis
Modern consumer devices such as televisions, Blu-ray players, and receivers typically use a digital interface such as S/PDIF, Toslink, HDMI to transmit audio signals.  In addition to the digital audio data, these interfaces also carry auxiliary information about the audio signal, metadata. The APx Metadata monitors decode and display metadata values as they are received from the device under test.

APx515B Series Standard Measurements

(Advanced measurements available for the APx515 are listed in the Options tab or the APx515B Series datasheet.)

  • Crosstalk
  • DC Level
  • DC Level Sweep
  • DUT Delay
  • Frequency Measurement
  • Frequency Response
  • Interchannel Phase
  • Level & Gain
  • Level Ratio
  • Measurement Recorder
  • Noise
  • Pass / Fail
  • Q-peak Noise
  • Signal Acquisition
  • Signal-to-Noise Ratio
  • Stepped Frequency Sweep
  • Stepped Level Sweep
  • TEDS Data
  • THD+N
  • Transfer Function



AES/SPDIF (B Series APx515 standard)
Provides AES3, AES/EBU balanced digital I/O on XLR; unbalanced SPDIF digital I/O on BNC; and TOSLINK optical digital I/O.

ASIO (B Series APx515 option)
Direct connection to ASIO-enabled devices. Supports up to 16 channels of ASIO at one time (with v4.0 software or later; two channels only when using earlier APx software versions). Requires either APX-SW-ASIO or one of the optional B Series APx515 software bundles (APX-SWB-2 or APX-SWB-6).


APx500 software options provide measurements and functionality beyond the core set of capabilities standard for the APx515. A variety of options are offered, suited to different specific test applications and requirements.

For B Series APx515 analyzers, and Legacy APx515 analyzers running version 5.0 software, software option licenses are electronically activated and are tied to a specific analyzer via serial number. For Legacy APx515 analyzers running APx software version 4.6 or earlier, software option licenses are enabled by one “iButtons” that mount on the rear of the instrument.

Electro-Acoustic Production Test (SW-SPK-PT)
The SW-SPK-PT option enables high-speed production test of electro-acoustic devices, providing key loudspeaker measurements in a single one-second sweep. Results include Rub & Buzz detection, essential Thiele-Small parameters, and impedance magnitude and phase. A proprietary modulated noise measurement is also provided to aid in detecting enclosure air leaks.

Electro-Acoustic R&D (SW-SPK-RD)
The SW-SPK-RD option delivers a complete suite of measurements and results tailored to the needs of designers and engineers developing electro-acoustic audio products. It includes key measurements and results such as complete Thiele-Small characterization; time-gated, quasi-anechoic Acoustic Response; Impedance analysis; plus the Loudspeaker Production Test measurements.

High-Speed Test (SW-HST)
SW-HST adds high-speed multitone and continuous sweep measurements to the APx515 B Series.

Advanced Measurement Library (SW-AML)
SW-AML is a library of 17 measurements to increase your B Series APx515’s capabilities, including the addition of IMD, Maximum Output Level, dynamic range, and FFTs.

Acoustic Response (SW-ACR)
This option adds five measurements for acoustic response testing with the APx515 B Series.

ASIO Interface (SW-ASIO)
SW-ASIO adds software connectivity for PC audio interfaces to the B Series APx515. Supports up to 16 channels of ASIO at one time (with v4.0 software or later; two channels only when using earlier APx software versions).

Bench Mode (SW-BEN)
SW-BEN adds Bench Mode capability to the B Series APx515 (requires APx515 Software Bundle (APX-SWB-2)).

APx515 Software Bundle 2 (APX-SWB-2)
Combines the ACR, AML, ASIO and HST software options for B Series APx515 into a single, cost-effective bundle. ASIO option supports up to 16 channels at one time (with v4.0 software or later; two channels only when using earlier APx software versions).

APx515 Software Bundle 6 (APX-SWB-6)
Adds Bench Mode (SW-BEN) to the measurement options and ASIO capability included in SWB-2 (listed above).

Perceptual Audio Test: POLQA (SW-POLQA-2)
Perceptual audio measurement returns a subjective assessment of speech quality using the next-generation POLQA algorithm for wide-band speech devices or devices with acoustic coupling. (Successor to PESQ with support for HD Voice, 3G, 4G/LTE and VoIP technologies)

Speech Intelligibility: ABC-MRT Measurement (SW-ABC-MRT)
The APx ABC-MRT plugin is a software option for APx500 audio measurement software that provides speech intelligibility measurement based upon the ABC-MRT speech processing algorithm developed by the Institute for Telecommunication Sciences (ITS) of the United States National Telecommunications and Information Administration (NTIA).

Speech Intelligibility: Speech Transmission Index (SW-STI)
SW-STI is a plug-in for conducting Speech Transmission Index (STI) measurements using the STIPA method.



  • Residual THD+N (20kHz BW)
    -102 DB +2.0 µV
    Typical <-106 DB (1kHz, 20.V)


  • Maximum Rated Input Voltage
    125 Vpk
  • Maximum Bandwidth
    >90 kHz
  • IMD Measurement Capability
  • Amplitude Accuracy (1 kHz)
    ±0.05 dB
  • Amplitude Flatness (10 Hz–20 kHz)
    ±0.010 dB
  • Residual Input Noise (20 kHz BW)
    1.4 µV
  • Individual Harmonic Analyzer
  • Max FFT Length
    1024K points
  • DC Voltage Measurement

APx515 B Series Full Specifications


  • System performance is sensitive to processor speed; faster processors will yield faster results.
  • APx500 is data intensive and it is recommended that other data-intensive applications not be run concurrently. This includes Audio Precision AP2700, APWIN or ATS.


  • Sine Frequency Range
    2.0 Hz to 80.1 kHz
  • Frequency Accuracy
    3 ppm
  • IMD Test Signals
  • Maximum Amplitude (balanced)
    16.00 Vrms
  • Amplitude Accuracy
    ±0.05 dB
  • Flatness (5 Hz–20 kHz)
    ±0.010 dB
  • Analog Output Configurations
    Unbalanced, balanced, common mode
  • Digital Output Sampling Rate
    27 kS/s to 200 kS/s
    27 kS/s to 108 kS/s Optical
  • Dolby / dts Generator
    Yes (encoded file)


  • Microsoft Windows 10 (64-bit) operating system
  • USB 2.0 or USB 3.0 (two are required for optional switcher or DCX-127 use)
  • Intel i5 or better processor running at a clock speed of at least 2.5 GHz (AMD processors with similar specifications are also supported)
  • At least 8 GB RAM. 16 GB is highly recommended.
  • Internet connection or an USB Type A port (to access APx500 software for installation).
  • At least 1.5 GB of free hard disk space (an SSD for the operating system drive is recommended)
  • A color monitor and video card with at least SXGA (1280 X 1024) video graphics support (video resolution of 1900 x 1080 or greater is recommended)
  • More detailed information is available on our AP Software and Windows Compatibility chart