Thanks,
~mark

I’m not sure why the volume is low, it could be due to differences in the speakers found in old handsets or the audio drive capability of different bluetooth headsets.

I would start by double checking your wiring and solder connections, just to be sure a hairline short isn’t killing the audio signal. If everything looks ok, you could try a different speaker from another brand of handset to see if one type works better than another. Alternatively, you could scrounge the original speaker out of the bluetooth headset and glue it to the back of the earpiece – kind of a hack but a good backup plan. Even the tiny 8 ohm speaker out of a small electronic toy or greeting card should work.

Another option – If you are comfortable with building simple electronics, you could build a small audio amplifier using an LM386 chip (see Make’s cracker box guitar amp) and power it with the headset battery, assuming the 386 can go that low in voltage.

Hope this helps,
Jeff

Thanks,
~mark

Someone actually did something very similar to what you are looking for, check this out:

http://www.vonslatt.com/proj-handset.shtml

That should give you a head start!

nice work! i’m interested in modifying an old handset like this to connect to a cellphone (motorola razr) with the original squiggly wire. as far as you know, is there any way this could be done (some kind of adaptor, or something)? i know they make reproduction vintage handsets, but i want an *actual* vintage handset. the weight and sound can’t be duplicated! feel free to email me – thanks a lot!

I took a pack apart from a model airplane that had one cell starting to go bad (swell up) and I now get over 8 hours of talktime in a very similar setup to yours.