SLAA936A September 2020 – March 2021 TAS2563
The task of optimizing the sound pressure level (SPL) and sound quality of a micro-speaker for mass-market, low-power applications can be very challenging. The combination of digital signal processor (DSP), digital-to-analog converter (DAC), and smart amp protection provide the audio engineer with many tools and knobs with which to achieve the best quality sound for the small-form factor speakers popular in portable low-power devices like mobile phones, tablets, laptop computers, and home automation. Micro-speakers are especially limited in maximum SPL and bass response due to the small diaphragm size; however, the smart amp allows the user to tune the speaker to achieve the maximum audio quality from a limited speaker.
For professionals in the audio industry, learning from the target audience (customer) as to what their key audio priorities are is important to make adjustments to their preference. However, there are some universal qualities and characteristics of a good balanced tuning. Most customers generally want the same ideal sound:
Achieving all of these goals is usually very difficult, so tuning is often a matter of determining the customer’s priorities. Some customers are willing to sacrifice SPL to achieve a flatter, more-balanced response. Some customers prioritize SPL at the risk of a narrower tone. A well-designed speaker, combined with the smart amp, typically enables a well-rounded sound which can then be fine-tuned to the customer’s preference.
This application report makes many references to the PurePath™ Console 3 (PPC3) graphical user interface (GUI) used for both integrated and non-integrated smart amp solutions, such as the TAS2563 EVM. This document does not cover proper installation, navigation, and elementary proficiency with PPC3. This application report mainly focuses on the “Tuning and Audio Processing” tile under the device home page of the GUI and expands on certain tuning tools in the GUI.
This report does not address speaker characterization. While proper speaker characterization, is actually quite critical to a good tuning and is integrated into PPC3 and the EVM hardware, this report assumes the speaker parameters, such as the Re, Bl, Xmax, Tmax, Sd, Thiele-Small model, and temperature model are measured and loaded correctly into the .ppc3 file before proceeding with the tuning. Perform a full characterization with the combination of PPC3, the smart amp EVM, and the learning board (sold separately). The user can also import parameters from one .ppc3 file to another or enter them manually if acquired by other means.
This report also assumes that the speaker normalization is complete. Even though speaker normalization is not included in the characterization page of the GUI (and is found in the Audio Processing section), the user must consider this as a required post-characterization step, which is critical to any good tuning. Normalization allows the smart amp algorithm to compensate for the inherent high-frequency impedance response caused by the Le of the speaker. The volume of the test signal in the wizard can be left at the default value of –12 dB.
This report only addresses the mono-tuning mode, and does not address the dual-mono mode used in stereo applications with multiple devices. The user can apply all of the tuning strategy that this report proposes to each speaker of a stereo application. However, note that stereo applications can benefit from additional tuning such as phase alignment, ganged dynamic range compression (DRC), or linked smart amp protection.