Dulci "Speaker" Units - What are they? - UK Vintage Radio Repair and Restoration Discussion Forum

cynfelyn · 23rd Oct 2025, 4:59 pm

Hey all.

I'm new here and hope you are all well!

I've just inherited a couple of Dulci units that I believe are some sort of "speakers". Pictures are attached.

I searched online for "Dulci: and found this forum post (https://www.vintage-radio.net/forum/showthread.php?p=1594050), yet still couldn't work out the possible original use-case for them.

Does anybody know what they might have been used for, and if it's worth restoring them at all?

Any information would be very welcome!

Thank you.

Cyn.

23rd Oct 2025, 5:25 pm

Interesting. It looks like a little amplifier in one cabinet with a tweeter, with the other containing the 'bass' speaker. What I fail to spot, is the input to the blue unit.

TonyDuell · 23rd Oct 2025, 5:29 pm

Could they be a 'baby monitor' one-way intercom? The light grey unit goes near the baby's cot, it contains a microphone (the Acos transducer) and a 2-valve amplifier. Wired to the dark-coloured unit which is a speaker and volume control, placed near the parents.

23rd Oct 2025, 5:31 pm

Quote:

Originally Posted by TonyDuell

Could they be a 'baby monitor' one-way intercom? The light grey unit goes near the baby's cot, it contains a microphone (the Acos transducer) and a 2-valve amplifier. Wired to the dark-coloured unit which is a speaker and volume control, placed near the parents.

You might have a point there, since ACOS made mics. and that would explain the absence of an input!

Beesmart · 23rd Oct 2025, 6:15 pm

No l did not get my eBay purchase Dulci running, as noted here, they are most probably Baby Monitors from the sixties. So they would receive a signal and send it to a receiver in another location, or vice versa. My project is now early valve hi-fi.
I Think Tony Duell has the answer above.

julie_m · 23rd Oct 2025, 8:29 pm

What are the valves?

It might be worth taking some resistance measurements from each of the mains plug pins (Live, Neutral and Earth) to the metal chassis and each of the screw terminals to which the interconnecting plug connects. Just because there's a transformer, doesn't mean a set is isolated. I suppose the audio interconnection is on the secondary side of the loudspeaker transformer, at least .....

cynfelyn · 28th Oct 2025, 6:54 pm

Thanks all! Really appreciate the input. Do you think anyone would want to buy them if I put them up for sale?

I really like the housing and would happily have kept them if they were normal loudspeakers!

23rd Oct 2025, 4:59 pm	#1
cynfelyn Diode Join Date: Oct 2025 Location: Crickhowell, Wales, UK. Posts: 2	Dulci "Speaker" Units - What are they? Hey all. I'm new here and hope you are all well! I've just inherited a couple of Dulci units that I believe are some sort of "speakers". Pictures are attached. I searched online for "Dulci: and found this forum post (https://www.vintage-radio.net/forum/showthread.php?p=1594050), yet still couldn't work out the possible original use-case for them. Does anybody know what they might have been used for, and if it's worth restoring them at all? Any information would be very welcome! Thank you. Cyn. Attached Thumbnails

23rd Oct 2025, 5:25 pm	#2
guest Guest Posts: n/a	Re: Dulci "Speaker" Units - What are they? Interesting. It looks like a little amplifier in one cabinet with a tweeter, with the other containing the 'bass' speaker. What I fail to spot, is the input to the blue unit.

23rd Oct 2025, 5:29 pm	#3
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 6,104	Re: Dulci "Speaker" Units - What are they? Could they be a 'baby monitor' one-way intercom? The light grey unit goes near the baby's cot, it contains a microphone (the Acos transducer) and a 2-valve amplifier. Wired to the dark-coloured unit which is a speaker and volume control, placed near the parents.

23rd Oct 2025, 6:15 pm	#5
Beesmart Triode Join Date: Oct 2023 Location: Leicester, Leicestershire, UK. Posts: 22	Re: Dulci "Speaker" Units - What are they? No l did not get my eBay purchase Dulci running, as noted here, they are most probably Baby Monitors from the sixties. So they would receive a signal and send it to a receiver in another location, or vice versa. My project is now early valve hi-fi. I Think Tony Duell has the answer above.

23rd Oct 2025, 8:29 pm	#6
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 8,006	Re: Dulci "Speaker" Units - What are they? What are the valves? It might be worth taking some resistance measurements from each of the mains plug pins (Live, Neutral and Earth) to the metal chassis and each of the screw terminals to which the interconnecting plug connects. Just because there's a transformer, doesn't mean a set is isolated. I suppose the audio interconnection is on the secondary side of the loudspeaker transformer, at least ..... __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

28th Oct 2025, 6:54 pm	#7
cynfelyn Diode Join Date: Oct 2025 Location: Crickhowell, Wales, UK. Posts: 2	Re: Dulci "Speaker" Units - What are they? Thanks all! Really appreciate the input. Do you think anyone would want to buy them if I put them up for sale? I really like the housing and would happily have kept them if they were normal loudspeakers!