Small Speaker and Class-D Amp Selection Guide

Concept render

Start from target SPL at 10 cm and speaker sensitivity, then compute electrical power with P = 10^((target SPL − sensitivity) / 10) watts. Compare that power with what the amplifier can deliver from your battery voltage. The TAS2563 datasheet shows one cell limits output unless boosted. Battery draw follows from power, efficiency and duty cycle.

A small wearable speaker has three limits: how loud it must be, how much power one battery cell can deliver, and how much battery the product can spend on sound. This guide connects them in one chain of arithmetic. It uses published amplifier datasheet values as of October 31, 2026, and marks every other input as one you replace. It contains no Duobay price and no measured result.

What does the amplifier datasheet say about battery limits?

The table lists the rated operating points from the TI TAS2563 datasheet. The voltage and current columns are our own arithmetic from P = V²/R, so you can re-check them. The battery-current column is a floor: it is P divided by the supply voltage with 100 percent efficiency, so real draw is higher. We do not cite an efficiency figure, because the vendor curve must be read from the datasheet at your operating point.

Both battery rows need more than 3.6 V at the speaker: 4.94 V rms for the 4 ohm row and 6.32 V rms for the 8 ohm row. An unboosted single cell cannot supply that.

The datasheet says the integrated look-ahead Class-H boost "dynamically adjusts boost voltage during playback, increasing efficiency and saving battery life in battery-powered systems" (TI TAS2563 datasheet, accessed 2026-10-31). It also states that current-and-voltage sensing speaker protection permits pushing peak SPL without damaging the speaker.

For contrast, the TI TAS2780 datasheet (accessed 2026-10-31) states: "The Class-D amplifier is capable of delivering 25 W of continuous power into a 4 Ω load with less than 1% THD+N at a supply voltage of 18 V." That is the kind of part you do not need to size for a small wearable.

How do you get from target SPL to electrical power?

The relation is standard acoustics. Use it to estimate, then measure.

SPL_10cm = S + 10 × log10(P)             S: dB SPL at 1 W, 10 cm; P: W

P        = 10^((SPL_target − S) / 10)

If S is given at 1 W and 1 m:
S_10cm   = S_1m + 20 × log10(1 m / 0.1 m) = S_1m + 20 dB

V_rms    = sqrt(P × R)                    R: ohm
I_rms    = sqrt(P / R)

The number that matters is the gap, SPL_target − S. Here is the formula applied to four gap values. This is arithmetic only, with no real speaker behind it.

Every 3 dB of extra level doubles the power. A gap of +10 dB asks for 10 W, which is above the 6.1 W battery-powered peak figure in the table. A gap of 0 dB asks for 1 W, which is below it. Your own gap decides where you land, so compute it with the sensitivity from the datasheet of the speaker you shortlist.

How do you turn power into battery draw?

I_batt_play = P_play / (η × V_batt)      A, while playing
I_avg       = d × I_batt_play + (1 − d) × I_q
mAh per hour of use = I_avg in mA        (a current of 1 mA for 1 hour is 1 mAh)

Here is a check on the peak case from the table. At the 3.6 V battery operating point the supply current floor for 6.1 W is 6.1 / 3.6 = 1.69 A. That is a floor at 100 percent efficiency, and it applies only at peak. Average draw uses P_play, the average power of real material, and your duty cycle d. Both are yours to measure.

Variables and their status:

This article cites no amplifier efficiency figure. Read the efficiency curve in the current datasheet at your power and supply voltage. Battery life for your product is not published by the vendor and needs a test on your board.

What are the common traps?

These follow from the datasheet values above. They come from engineering reasoning about how the numbers behave. None describes an incident at any company.

• A single cell limits the output. The TAS2563 datasheet quotes 6.1 W into 4 ohm at a 3.6 V battery only with its integrated 11.5 V Class-H boost. An amp that runs straight from the cell cannot swing more than the cell voltage allows, so a power figure from another operating point does not carry over to your design.
• A rating at a supply you do not have. The 10 W figure for the TAS2563 needs boost bypass and an external 12 V supply. A battery wearable has no such rail, so that row shows what the part can do at 12 V. A battery wearable cannot reach it.
• Mixing peak and average power. The 6.1 W figure is peak power. Battery draw follows the average power of your program material, which is lower than the peak. Using peak power for the battery model overstates the draw. Using average power for the amp rating understates the headroom you need.
• Sizing the part for the biggest number. The TAS2780 datasheet states 25 W continuous into 4 ohm at an 18 V supply. That part is built for much larger systems than a small wearable and needs a supply the product does not have.
• Free-air sensitivity applied to an enclosed speaker. The SPL formula starts from a sensitivity number. A vendor sensitivity is measured under the vendor test conditions. Your housing, sealed volume and any leak change the result, so treat the formula as an estimate until you measure it in the enclosure.
• Impedance picked after the amp. The same amp lists 6.1 W into 4 ohm and 5 W into 8 ohm. The speaker impedance you choose changes the deliverable power from the same battery, so choose speaker and amp together.

What should you measure on your own board?

No real SPL, battery life or distortion result for a specific wearable appears in this article. Datasheet values describe the part. Measure your own product.

Set the pass line for each test from your product requirement, and record the basis for it. Set it before you run the test.

What should you ask before you choose?

Take this list to your team and to any supplier who proposes a speaker or amplifier.

• What SPL at 10 cm does the product need, who set it, and in what room and use case?
• Which sensitivity does the speaker datasheet state, at what power, distance and baffle?
• Does the amp reach the computed power from the battery voltage we will really have at end of discharge?
• Do we need a boost converter, or is the power we need inside what the unboosted cell can deliver?
• Which load impedance gives the amp the most useful output from one cell, and does a suitable speaker exist in that impedance?
• Does the amp protect the speaker from over-excursion, and who tunes that protection?
• How much of the playback is speech and how much is music, and what is the average power of each?
• What is the quiescent current in the idle mode we use, and how often does the amp wake?
• What happens to the battery rail when the speaker plays its loudest prompt?
• Which numbers in our model come from a datasheet, and which are still guesses we must bench-test?

If you want help choosing the speaker, amplifier and enclosure for your device, tell us about your device. You can also read about our audio and voice hardware development.

Sources

All pages accessed October 31, 2026. Datasheets are revised, so re-read the current version before you decide.

• Texas Instruments, TAS2563 datasheet: https://www.ti.com/lit/ds/symlink/tas2563.pdf (accessed 2026-10-31)
• Texas Instruments, TAS2780 datasheet: https://www.ti.com/lit/ds/symlink/tas2780.pdf (accessed 2026-10-31)