Possible to connect two head units to one pair of speakers?

[Peter C]

I'm proposing to re-fit a period Becker head unit and move the modern (MP3 compatible) head unit to the glovebox. I would like the Becker to work (radio and tapes), which involves making connections to the same pair of speakers that will be connected to the modern unit. I obviously wouldn't attempt to use both units at the same time.

 

Is this possible without causing damage to either unit? Would an incoming speaker signal have any effect on the innards of either unit whilst it is switched off?

 

Has anyone else tried something like this?

 

Any advice would be appreciated.

[dean36014]

Not sure, but i do remember you could buy a speaker switch box from the days you could buy separate cassette players.

[Negative Creep]

In theory it would, since the speakers don't send any sort of current to the head unit so I can't see how they'd damage it

[dean36014]

A quick google on hifi sites and they say no, use a speaker switch as it can do nasty things to your amps. I'd imagine the same thing would apply to in-car equipment too.

[mat_the_cat]

You could use a DPCO relay, connecting the L and R speaker +ve wires to the common terminal for each pole. To operate the relay use the accessory signal from the modern radio, so that whenever you turn that on it switches the speakers to its output. You could go one further with another relay to cut the power to the old unit at the same time...

[NorfolkNWeigh]

For my first professional ICE Install*

 

Factory head unit, complete with front AND rear speaker. Top of the range Executive - that was how I rolled .

Plus Binatone Stereo Cassette with hi-power (8w!!!!!!) speakers.

Plus 8 Track multi something stereo .

Plus another pair of super quality hi-power speakers

.

 

Everything was powered by one wire straight off the battery and all 3 components connected to all six speakers( with bell wire)

The Cassette and 8 track were attached to the transmission tunnel with Meccano and self tappers into the carpet and sound proofing.

 

The cassette and 8 track were nicked and I replaced them with an auto reverse cassette and some sort of surround sound/ graphic equaliser thing. ( my Dad worked for Binatone and once brought home a complete Motor Show display complete with slot mags and a brand new Beetle Bonnet and wings- scrapped long before Hitlerwagens were worth anything, although the bonnet saw service as a sledge for many winters)

 

This Zodiac never caught fire, well depends on the definition of fire I suppose.

[Kiltox]

Why not just get the modern audio into the old head unit using a FM transmitter or cassette adaptor plugged into an iPod?

[Peter C]

Thanks for your input guys, I've put my plans on hold until I have everything I need to do the job properly.

[Peter C]

  On 27/08/2016 at 11:36, Kiltox said:

Why not just get the modern audio into the old head unit using a FM transmitter or cassette adaptor plugged into an iPod?

Good suggestion but I like good quality sound and neither will provide the desired effect. Also, I have an amp and sub, which the Becker cannot be readily connected to.

[Dave_Q]

Does your modern have a line in option?

 

If so you can get a small widget to convert the speaker wires of the oldie into an rca audio out type thing.

 

Like this: http://www.ebay.co.uk/itm/281083866827

 

Then your Becker would be the aux-in on your modern and only 1 set of speaker/amp wiring.

[Asimo]

Don't connect the outputs of two units together to connect to one loudspeaker.

There is a real risk of instantly ruining one or both, even if the other one is not powered up;  exactly what will happen depends upon the exact circuit detail of the amplifiers in both units.

It is possible that both are configured in such a way that nothing bad will happen so if anyone tells you "oh I did that, it was ok" they may well be telling the truth but don't take that as evidence that your two boxes will be ok.

Not worth the risk to find out.

Use the aux input as suggested above or a changeover switch / relay.