Bluetooth Speaker build using Fosi BT30

[NealfromNZ]

This post is about a DIY Bluetooth Speaker I built a few years ago based on a Fosi Audio BT30. The same could be done with the BT30 pro

Background:

This was a project for my daughter that was around 10 at the time. The idea was to build a retro styled Bluetooth speaker that could work on mains or battery power. Daughter was learning Hip Hop at the time so the idea was to build a 2.1 speaker system with a subwoofer and passive radiators tuned to around 55hz to emphasise a typical hip hop beat. The speaker needed to have enough volume to fill her bedroom or a small dance studio with music. Target level for spl was in the high 90 db mark. But also be portable enough for a carried by an adult. The battery charging stage needed to accommodate ac for quick charging or be able to use 12v outlet socket in the SUV. Daughter also plays electric so speaker is also used as a practice amp using suitable guitar pedal.

This was the end product. ( edit , need to work out maximum size for attaching pictures )

 

[NealfromNZ]

Parts list

• Fosi BT30 2.1 Bluetooth amplifier
• Fosi AC power Supply 24v
• Jaycar Response 100mm Kevlar Coax speakers x 2
• Tang Band W5 5.25 inch subwoofer
• Dayton Audio 150mm Passive Radiators x 2
• Dayton Audio LLB 21 volt dc power supply running 5 x 2650 lithium batteries
• Dayton USB output board for charging phones, providing 5v dc power for guitar preamp
• 5 x quality 2650 lithium batteries ( note low quality batteries can be fire hazard )
• 19mm plywood for outcase
• 12mm plywood for infill , baffles , speaker grill
• Tolex vintage amp covering for wrapping speaker
• Classic style speaker cloth
• Peen recessed handle blank
• Peen chrome guitar handle
• Peen chrome corner protectors
• Peen feet x4
• 24 volt automotive relay
• Old car speaker grill for making vents for amp and psu
• Various screws , chrome finishing screws , pva glue , spray contact adhesive for tolex
• Gasket tape for sealing back panel

 

[NealfromNZ]

Box design

• Outer frame 19mm plywood, strong enough to be sat on, can take some moisture rather than using MDF
• Inner frame , passive radiator baffles , speaker grill inserts , amp partitions 12mm plywood

Bottom bass chamber

• Calculated area size based on TS specs of Woofer and desired bass response
• Accommodates Tand Band W5 subwoofer and 2x Dayton passive radiators
• 8 litres of sealed area to give 55hz bass bump and extension drown to 30hz
• Passive Radiators used to enhance bass whilst keeping
• Drivers recessed to minimise knock damage
• Removable grills sound servicing be needed

Amplifier and PSU chamber

• Top and bottom vented chimney style , cold air intake under speaker amp chamber
• Rear access panel using part of electronic box kit
• Speaker grill inlay

Top speaker chambers

• Approximately 3.5 litres of sealed enclosure space
• Crossovers mounted inside
• Speaker wool added to enclosure to change Q of 100mm speakers
• Note , speakers used are high Q automotive so normal expect Infinite Baffle so bottom end response suffers a bit

Carry Handle mount

• Uses T nuts on underside to ensure no chance of fasteners pulling through
• 40mm feet used to ensure airflow underneath to psu / amp chimney