508
Item nr.

Gerard BigTooth Speaker

Multipurpose big Bluetooth set.

The Design

From the junk store I got a pair of Philips 22AH491 speakers for 6 euros. These units from 1978, of type open baffle, are basically wood crates with a single, but dual cone, loudspeaker. Philips Vintage: The impedance is 4 Ohm, the power up to 13W (in high sensitive units this produces a lot of noise!), the resonance frequency is 75Hz, and the frequency range is 55 to 18000 Hertz. To plan your woodcarving actions, the side panels are 9.5mm thick and the front panel is 19.5mm thick.

In one speaker I mounted a small Bluetooth unit, obtained for just over 3 euros from AliExpress. The unit also receives FM, plays from USB drives and flash cards, and has AUX input. It is controlled by four front buttons or by infrared remote. Unlike the Bluetooth unit in Dr Watson, this is a unit with on board amplifiers.

This model has fewer options than Dr Watson: no earphone, no Mono operation, no using without the internal speaker. Besides the speaker box and bluetooth unit, a power socket for 5V DC, power switch, speaker jack to connect the other speaker, and whip antenna complete my design.

This Object

Mode	mA	W
Off (by power switch)	0	0.1
Standby (from BT)	8	0.3
Standby (from FM)	33	0.5
Bluetooth - No Conn	35	0.5
Bluetooth - Connected	23	0.4
Bluetooth - Low volume	50	0.6
FM - low vol	100	1.0
AUX	56	0.6
USB

I measured the energy taken by this stereo unit in various modes, both at the DC entry (in mA) and with a Watt meter from the mains. The power draw is surprisingly low when there is a Bluetooth connection, but no sound is played. So I conjecture, that the processor is able to switch off the amplifier (or put it in sleeping mode). The FM mode is quite expensive, power wise. Further, I note that the unit has two different standby modi, because the consumption differs wheter standby is entered from Bluetooth or FM mode.

The BigTooth was heavily used during the pandemic, and in February 2023 I replaced the battery cell in the remote control.