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engels 9th September 2007 08:47 PM

Another bargain = another question
Visiting good old Europe I went to a second hand shop and found this:

It is a speaker cabinet, apparently very old, worm holes all around. 5 euros including the speaker and the transformer inside.

The 8" speaker is wrapped in cloth and have a transformer attached to the frame. I was afraid it's a field-coil but there seem to be a magnet. The inpedance (5 ohms) is stamped on the magnet.

At first I was puzzled as it appears to be a speaker with a long cord, so why the transformer? The transformer is unsoldered and I wonder what it was before it was converted into a speaker. There are no signs of previously mounted chassis inside.

The transformer is definitely a SE output. It's primary is unsoldered from the terminal strip and is hanging in the air. the strip is used for the cord and speaker connection.
The transformer's secondary is coming out right in the middle of the bobbin through the paper (is that paper? maybe pergament?). One terminal is soldered to the frame and the other is not connected - that's that solder spot on the black bobbin.

I was trying to measure the impedance and here's what I've calculated:

resistance: Primary 596ohm, secondary 1.4ohm
impedance: I fed the primary with 24.6V AC and got only 0.4V AC on the secondary. Considering it's a 5 ohm speaker the primary impedance should be 19.000 ohm - a bit too much!!!

So I wonder what this thing was originally and if I may use this OT somehow.
The plan for today is to convert it into "antique" combo amplifier with some funny-looking ST tubes. Or maybe a champ 5W with metal 6V6 and 6SJ7.

The 19K is something annoying. Do I have a mistake somewhere in the calculations? Is there any tube working with 19K load???

dnsey 9th September 2007 08:55 PM

It used to be normal practice to have the OPT in an external speaker cabinet, and to feed it at high impedance.

No doubt one of the valve experts will be along soon to tell you what was driving it!

planet10 9th September 2007 09:31 PM

Even without the driver out of the bag, i'd guess it is a Philips.


engels 9th September 2007 09:57 PM

huh huh

Originally posted by planet10
Even without the driver out of the bag, i'd guess it is a Philips.

low impedance speaker + high load = philips???

actually I'm pretty close to Eindhoven at the moment, but the speaker has something stamped on it, something pretty long in gothic letters. I'm not sure what it says but it's not philips. here's the logo:

rcavictim 9th September 2007 10:14 PM

5 ohms eh!? Is that half metric? :D

I HAVE TO ASK THIS. Is this a Bag End loudspeaker???? :D

OK so much for my comedy routine. I have seen that particular driver show up on ebay for big bucks. Presumably it is a pretty good near FR driver. Big alnico magnet.

Toss that toy xfmer into the parts box and put that baby in a nice cabinet driven from a nice SE tube amp.

engels 9th September 2007 10:25 PM


Originally posted by rcavictim
Toss that toy xfmer into the parts box and put that baby in a nice cabinet driven from a nice SE tube amp.
I cannot imagine any cabinet nicer than the original. :)

rcavictim 9th September 2007 10:31 PM

Re: cab

Originally posted by engels

I cannot imagine any cabinet nicer than the original. :)

Well yes it is darned pretty alright but sonically it`s 1930`s engineering will be easy to improve hugely upon with any number of modern cabinet designs now designed specifically for single FR drivers. Search this place and they are all here. Check specifically the Full Range Forum.

planet10 9th September 2007 10:58 PM

Re: huh huh

Originally posted by engels
low impedance speaker + high load = philips???
No. I've had philips thru here that looked just the same (except for the OPT) in their little cloth bags with the alnico "oil can" sticking out.


Dave Cigna 10th September 2007 12:05 AM

PA systems usually were 75 volt and had a step down transformer at each speaker, though 19k:5 doesn't seem right. Maybe the transformer is pooty?

I agree that the cab is beautiful even if it isn't the ultimate in sound quality. But who knows, it might be surprisingly satisfying for listening to radio in the shop. NPR might never sound better. :)

-- Dave

uvodee 10th September 2007 08:25 PM

Not 100pct sure yet but

a) 5 ohm speakers ar estill amongst us, Adelaide has ready them available, amongst others

b) speaker looks like it's from a russian ship, i remember seeing one very very similar on board of an old Latvian ship (ENGURE) in the captain's cabin ... but have no clue where it originated from.

maybe a try to rubb some graphite on the letters could reveal a bit more.

Jean- Pierre

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