1920s vintage speaker with a guitar amp (Impedance problem)

[bzblues]

Hello everyone!

(I apoligize in advance if I ask noobie quiestions, but I'm a beginer in this matter)

I have a 1920s vintage speaker that is in a pristine condition! I intent to use this speaker with a small powered guitar amp that I've built. The guitar amp is called "ruby" wich is a 9v powered 1watt amp and it works well with 4ohm and 8 ohm speakers.

This vintage speaker is 1000 ohms and obviously doesn't work out porpperly with the guitar amp because of the impedance. So, I started to do some research and I found out that you would have to use a "step down" or "step up" impedance transformer. Now, here is when I hit the wall because its an unknown territory for me (yet)

I found out a website that allows you to calculate the type of transformer that you would have to use, but it seems that the results are not "realistic" but still, maybe I'm missing a few things.

What would you recomend to do in this particular scenario? again, its a small guitar amp (1 watt, 9V powered, works well with a 4ohm speaker) and I want to use it with this 1920's vintage speaker that is a 1000 ohm.

Is it possible to do?

Thanks a lot in advance!

Brian.

[glebert]

Hi BZ!

If the speaker is really from the 1920s then it will be a "field coil" speaker.as opposed to a "permanent magnet" speaker which came around after WWII(ish). So my first question is what that speaker really is, and is it working properly. If it really is a field coil speaker I doubt you will be able to drive it from a 1 watt 9V type amplifier because it needs considerable voltage and current to energize the coil to create a magnet.

I would post some pics of the speaker and some folks here can probably chime in on the best way to proceed.

[mozz]

You should be able to measure (d.c resistance) of the voice coil and the field coil separately. That will give you an idea what you are going to need to do. I wouldn't run a guitar amp into it, i can bet the old speaker will blow from the square waves.

[Helmholtz]

On diyAudio it was suggested it could this type of very early speaker: https://www.jogis-roehrenbude.de/Nora-LS.htm

[nosaj]

Hello everyone!

(I apoligize in advance if I ask noobie quiestions, but I'm a beginer in this matter)

I have a 1920s vintage speaker that is in a pristine condition! I intent to use this speaker with a small powered guitar amp that I've built. The guitar amp is called "ruby" wich is a 9v powered 1watt amp and it works well with 4ohm and 8 ohm speakers.

This vintage speaker is 1000 ohms and obviously doesn't work out porpperly with the guitar amp because of the impedance. So, I started to do some research and I found out that you would have to use a "step down" or "step up" impedance transformer. Now, here is when I hit the wall because its an unknown territory for me (yet)

I found out a website that allows you to calculate the type of transformer that you would have to use, but it seems that the results are not "realistic" but still, maybe I'm missing a few things.

What would you recomend to do in this particular scenario? again, its a small guitar amp (1 watt, 9V powered, works well with a 4ohm speaker) and I want to use it with this 1920's vintage speaker that is a 1000 ohm.

Is it possible to do?

Thanks a lot in advance!

Brian.

Honestly try these guys They will put you in the right groove.
https://antiqueradios.com/forums/sea...ch_id=newposts

[nosaj]

https://www.radiolaguy.com/Showcase/...#39;s%20radio.

[The Dude]

A picture or two would help immensely.

[Chuck H]

A picture or two would help immensely.

Indeed!?! A 1000 ohm speaker? most headphones come in below that. Could this even be intended as a public listening device?

[The Dude]

I'm thinking that's a field coil measurement, as glebert theorized. But, that's pure speculation without seeing pictures of what we're talking about.

[bzblues]

Hello, everyone! thanks for the replys

Here are some pictures. I have 3 speakers of this kind and they all have the same type of coil and magnet. The screw in the back acts as a On/off switch I would say. You screw it and it makes contact and you can hear the speaker work.

Sorry for the messy pics, its not easy to shove the cellphone. The back lits are not possible to open except for one.

Here is more info about one of the speakers: http://earlywireless.com/celestion_c12_picinfo.htm

Cheers!

[Helmholtz]

So it's actually one of these early "reed" type speakers with the horseshoe magnet and not having a voice coil.
Now it would be important to know if 1000 Ohm is impedance or DCR.

[Chuck H]

Well here's what Wiki has regarding impedance for this type of speaker. I did some other reading elsewhere and it seems that the actual impedance of any given model could be very different at the whimsy of the designer. So I'm not sure how to determine the actual impedance of unknown units. They aren't like familiar speakers where DCR is often somewhat analogous with impedance.

[mozz]

Still saying you will probably ruin these using any guitar amplifier. As was mentioned, go to the forums at https://antiqueradios.com/ for info on these, and value.

[Helmholtz]

The OP also has a thread on diyAudio.
Here's what I just posted:
<From what I've read these speakers were directly connected as plate load (no OT) to the output tube of a low power SE amp.

The impedance is mostly inductive, so rises with frequency.
If not driven by a "current source" (tube), treble response will suffer.">

[Helmholtz]

As always the impedance can be found from voltage and current at some frequency, e.g. 400Hz.
As said, the impedance varies almost proportional to frequency.
Minimum impedance is the DCR.

Another method is calculating the impedance from DCR and L.