Extension speaker query

[Audio1950]

I've just been given the bass and tweeter speakers from a scrapped Bush SRG86 radiogram, which I can at last use as an extension for one channel of my own identical machine. However, when I looked on the back of mine, I find for each channel two wander plug sockets marked A and B, and a screw to disconnect the internal speaker. So far, so good, but what does the printing underneath them mean? Quote:

" Apply a potential +ve to A, -ve to B to move cone of internal L/S outwards"

What is a "potential positive and negative" and why would this be necessary?

Barry

[Radio Wrangler]

This is in case both speakers are in the same room. If the cones move in opposite phase, then particularly for lower frequencies, cancellation will occur. Get the phasing wrong and the amount of bas will be reduced, in other words.

You can always try it both ways round and just listen.

If the extension speaker is the only one going and the internal one is disconnected, then phasing doesn't matter.

David

David

[dseymo1]

I think it's just specifying the phase relationship, and saying that terminal A is connected to the speaker terminal which would produce a forward movement of the cone if a postive voltage were applied to it. In other words, 'A' would usually be coded red.

EDIT: Cross-posted with David, but if I understand correctly the idea is to have an external speaker for one stereo channel, in which case the phasing needs to be correct. You could just listen, try connecting a 1.5V cell to the extension speaker, or match the wiring of the extension to that of the existing speaker, seeing that they're identical.
Don't forget that you'll need some sort of crossover (possibly just a capacitor in series with the tweeter).

[Audio1950]

Thanks! The "new" speakers came with the relevant capacitor, so if I connect the extension speaker in exactly the same way as the internal one is, I should be ok.

Barry

[RojDW48]

Stereo set up records were all the rage way back when stereo recordings first came out - usually featuring a recording of Chabrier's ESPANA! and a plummy BBC lady announcer saying things like...'I am now speaking out of phase...' and advising you to reverse the connections on one speaker if you heard her in phase. Happy days!

[camtechman]

a plummy BBC lady announcer

Mary Maroussia

[Audio1950]

Originally Posted by RojDW48

Stereo set up records were all the rage way back when stereo recordings first came out - usually featuring a recording of Chabrier's ESPANA!

I just got a copy of "A Journey into Stereo Sound", a Decca LP which does have "Espana" on it, as well as trains hurtling between the two speakers, and a gentleman inviting us to play Ping (right speaker) Pong (left speaker. Great fun!

Barry

[camtechman]

and a gentleman inviting us to play Ping (right speaker) Pong (left speaker.

And he may be David Gell.

[Audio1950]

Originally Posted by camtechman

And he may be David Gell.

It's Geoffrey Sumner, whoever he is (or was!)

Barry

[paulsherwin]

https://en.wikipedia.org/wiki/Geoffrey_Sumner

[emeritus]

You should be able to check the phase without using a special test record by simply feeding the same mono audio signal to both speakers from the same source. If the speakers are in phase, then the sound will appear to come from midway between them. If they are in antiphase, then the sound will appear to come from the sides. This is the method I use when rewiring headphones or earpieces to ensure the phase is correct.

I remember a radio programme about the resistance in Europe mentioning that a way that was found effective against jamming was to listen to the same BBC broadcast on two different radios spaced some distance apart, I think tuned to different frequencies. To the listener, the jamming signals appeared to come from the direction of the individual radios, whereas the wanted audio signal combined in phase so as to appear to come from a direction different from either of the interfering sounds. The ability of the human ear to discriminate between sounds from different directions allowed the wanted broadcast to be clearly understood.

[camtechman]

PAULSHERWIN

Thanks for that, I used to keep a notebook with names of various "Voice Artistes" but lost it in my move to Milton Keynes.

I did a little voice work back in the day and knew most of the various 'yappers'.

I aspired to be a 'Richard Burton' but that entailed drinking copious amounts of scotch & smoking 60 a day......too much for my liking.

Tony

[Tim]

I have a "Scotch boy " test tape, the voice on which sounds very like John Snagge.