SMT-PBTS is an open source, Hi-Fi Bluetooth speaker PCB designed for the smallest, best sounding portable Bluetooth speaker applications. Just smaller than a credit card, it features multi-channel configurations for an immersive soundstage, a programmable audio DSP, Bluetooth v5.0 technology with external antenna support, 24-bit 192kHz audio support and more.
- Ultra small and compact design; just smaller than a credit card.
- Bluetooth v5.0 specification via Qualcomm’s CSR8675 SoC.
- Connect up to 2 devices simultaneously for shared musical playback.
- Up to 300ft theoretical Bluetooth connectivity range using external antenna.
- Supports nearly every Bluetooth A2DP streaming codec: AAC, SBC, MP3, aptX Classic, aptX-LL, aptX-HD, Faststream
- High fidelity audio playback with up to 24-bits and 192kHz sample rate support (only using aptX-HD codec).
- Incredible frequency response; 40Hz-22KHz @-3dB (only with suggested drivers and enclosure).
- High efficiency eliminates the need for heatsinks.
- Hybrid amplifier design consisting of Class D amplifiers for the bass drivers and linear Class AB amplifiers for the left, right, and center tweeters.
- Ultra low total harmonic distortion, even at maximum power: ~0.03% THD.
- Ultra low signal to noise ratio: > 108dB
- 35W + 35W onboard Class D amplifiers with 3x1W Class AB amplifiers.
- Uses high-end Panasonic acrylic resin film caps for all audio decoupling filters.
The schematic source for this project is located in /src. It is released as an EasyEDA source file. The PNG of the schematic is located in /pic.
PCB sources are located in /src. The sources are EasyEDA PCB design filetypes. PCB gerbers are in the releases.
- BoM is available as a .csv file in
/main - Only parts and components on the PCB are in the BoM.
- Outer enclosure demensions are as follows (in): Length: 10.5; Width: 4.25; Depth: 3.5
- Speaker hole diameters (in): Left and right surround speakers: 1.9; two bass drivers: 3.5; center speaker: 1.9
- Connector, Port, and LED hole diameters (in): Power & AUX connectors: 0.5; LEDs: 3/16; Port: 5/8
- It is recommended to use polyfill in the enclosure for better frequency response and dampening.
- The port of the enslosure is a PVC pipe with a inner diameter of 0.6 inches and is 9.75 inches in length (port tuning is between 40Hz - 45Hz).
- 0.25in thick MDF wood is reccomended for the speaker enclosure build.
- The two bass drivers are 3.5in in diameter and are manufactured by BH Acoustics (see datasheet). They were salvaged from two Samsung WAM1500 smart speakers. Due two the limited availability of these drivers, it is recomended to use these drivers as an alternative.
- The center driver is a tweeter. It is rated at 10w 4ohm and was also pulled from a Samsung WAM1500. There is no other public documentation of this driver. This driver can be used instead.
- The two surround tweeters can be found here.
- Power input via 5.5mm power jack. Buy it here
- This PCB features Bluetooth v5.0 using the BTM875-E Bluetooth module. The module can be reprogrammed to change the device's name as well as other properties. The programmer module is required because you need to flash the custom firmware onto the chip, which contains the code to drive the AIC3254 slave device. Buy this programmer.
- The pre-modulated 4s BMS PCB can be found here. I highly suggest swapping out the main IC on this BMS with this one for better discharge/overcharge protection and best compatibility with SMT-PBTS.
- Samsung 50E 21700 battery cells can be found here (order 4 for 14.4V configuration)
- Buy lithium-ion battery nickel strips here
- To prevent fire, use 20AWG wires or better for the power connections and TPA3128D2 output connections.
- 16.8V 2A lithium ion battery charger can be found here
This repo is licensed under the GPL v3.0. Any images are licensed under CC BY-SA 3.0.