speaker switching

[gkgsr]

hi all,

just need some info on switching speakers.. I have about 5 pairs of speakers i need to switch.

have considered using relays but i don't want them to pop every switch, and i think i should be able to use something else triacs/transistors or something simliar.

what can i use?

thanks

 

[Nigel Goodwin]

hi all,

just need some info on switching speakers.. I have about 5 pairs of speakers i need to switch.

have considered using relays but i don't want them to pop every switch, and i think i should be able to use something else triacs/transistors or something simliar.

what can i use?

Use relays or mechanical switches, nothing else is suitable!. As there's nothing to charge or discharge, you don't get any pops or clicks - except the obvious change from no noise to noise!.

 

[gkgsr]

so even the top end commercial units would use relays??

just wondering cause also there will be a click from my switchbox..

thanks for ur help so far.

 

[audioguru]

Relays or switches certainly would cause a "pop" unless they changed the speakers at exactly the zero-crossing time of the output signal.

If your switchbox has a capacitor that must be charged or discharged quickly when switching it, then it would also cause a "pop".

I have seen switchboxes that force the input signals into zero-crossing:
They mute all input signals when you touch the switch. The muting and unmuting is fairly slow so that the signals fade instead of muting and unmuting abruptly. :lol:

 

[Nigel Goodwin]

so even the top end commercial units would use relays??

Yes! - top end ones in particular would use relays, because anything other than a mechanical contact is going to reduce quality.

The 'slow' change that 'audioguru' suggests isn't likely to be done in any quality unit, because it introduces lots more complexity and reduces performance.

 

[audioguru]

Most top end amplifiers use a relay to connect the speakers after a delay for the amplifier to power-up and become stable. The relay also disconnects the speakers very quickly when you turn off the amplifier, so that you don't hear a "pop" as the amplifier's capacitor's discharge. :lol:

 

[Dr.EM]

Yeah, mine does that. It takes a few seconds, then you hear the relay click and its ready.

 

[Nigel Goodwin]

Yeah, mine does that. It takes a few seconds, then you hear the relay click and its ready.

Yes, it's usually connected to safety circuits as well, so if the output transistors go S/C the relay will disconnect the speakers to avoid the DC output blowing the speakers.

On REALLY top end equipment you generally don't have a relay, or even a fuse, on the grounds that anything like that might reduce the audio quality fractionally (at least in the users imagination!). So if the amp goes it's likely your speakers would as well :lol:

 

[eblc1388]

On REALLY top end equipment you generally don't have a relay, or even a fuse, on the grounds that anything like that might reduce the audio quality fractionally (at least in the users imagination!). So if the amp goes it's likely your speakers would as well :lol:

A speaker protection that applies a direct short across the amplifier's speaker connections using relay would not affect audio quality when not in use and could protect the expensive speaker. Wonder why no such scheme in use?

 

[Nigel Goodwin]

On REALLY top end equipment you generally don't have a relay, or even a fuse, on the grounds that anything like that might reduce the audio quality fractionally (at least in the users imagination!). So if the amp goes it's likely your speakers would as well :lol:

A speaker protection that applies a direct short across the amplifier's speaker connections using relay would not affect audio quality when not in use and could protect the expensive speaker. Wonder why no such scheme in use?

Probably because it sounds better having none, to maintain the quality?. But on the more practical side, putting a dead short across the speaker terminals with a relay is likely to cause some serious damage inside the amp (assuming the relay contacts will handle it). These sort of amps have seriously large PSU's.

 

[eblc1388]

Probably because it sounds better having none, to maintain the quality?. But on the more practical side, putting a dead short across the speaker terminals with a relay is likely to cause some serious damage inside the amp (assuming the relay contacts will handle it). These sort of amps have seriously large PSU's.

The protection is activated only after the amp is faulty, causing large current to flow into speaker. Who bl**dy care about it cause damage to the amp if the speaker is saved?

 

[Nigel Goodwin]

The protection is activated only after the amp is faulty, causing large current to flow into speaker. Who bl**dy care about it cause damage to the amp if the speaker is saved?

Perhaps the fire brigade and the insurance company :lol:

 

[eblc1388]

The protection is activated only after the amp is faulty, causing large current to flow into speaker. Who bl**dy care about it cause damage to the amp if the speaker is saved?

Perhaps the fire brigade and the insurance company :lol:

There is no increased risk as in the case of without the protection.

You should know that the speaker is a low impedance to the amplifier output and without protection it is passing all the faulty current already.

So you think it is better to let the faulty amplifier pass current to the coil instead of bypassing the current using a pair of contact.

Parallelling a contact to a speaker connection only bypass the current to the contact instead of it flowing out to the speaker coil. Mind you, a bit of current still flow in the coil but the magnitude would not be so high as to overheat/damage it.

 

[Nigel Goodwin]

There is no increased risk as in the case of without the protection.

The speaker will rapidly go O/C, acting as a fuse (an EXPENSIVE one), which is a FAR less risk than a direct short across the speaker terminals.

You should know that the speaker is a low impedance to the amplifier output and without protection it is passing all the faulty current already.

Yes, noramlly 8 ohms impedance, about 6 ohms to DC.

So you think it is better to let the faulty amplifier pass current to the coil instead of bypassing the current using a pair of contact.

Not 'better', but safer, the coil will go O/C which is a fairly 'fail safe' result.

Parallelling a contact to a speaker connection only bypass the current to the contact instead of it flowing out to the speaker coil. Mind you, a bit of current still flow in the coil but the magnitude would not be so high as to overheat/damage it.

Very little power to the voice coil, obviously depending on the contact and wiring resistance, which should be negligible compared to the voice coil.

But the fact remains, they DON'T do it, and I've never even heard it suggested before?.

 

[eblc1388]

But the fact remains, they DON'T do it, and I've never even heard it suggested before?.

Oh you are absolutely right. There is a very good reason people don't use it but fire/damage to amplifier isn't among the considerations. 8)

 

[audioguru]

Most amps with relays connecting the amp to the speaker disconnect the speaker when a DC fault occurs, not short the output of the amp. :lol:

 

[eblc1388]

Most amps with relays connecting the amp to the speaker disconnect the speaker when a DC fault occurs, not short the output of the amp. :lol:

But purist would argue that the relay contact affect sound quality.

So I suggest why not put a contact across the speaker in case of fault because the normally opened contact would not affect the sound signal in any way.

There is no issue in shorting the output of an amplifier or a power supply. My 16A power supply if faulty would fire a SCR and short the output to protect my external circuit against high voltage.

No one forces you to keep the AC suppy ON forever when this happens to result in a fire. As soon as the relay closes, one can also trip the AC power along with it. It isn't rocket science.

 

[audioguru]

If a transistor shorted in an amplifier's push-pull output and tried to put the supply rail at the output, I wouldn't want to have relay contacts short it with a big spark welding its contacts, I would want the relay contacts to disconnect my expensive speaker. :lol:

 

[eblc1388]

If a transistor shorted in an amplifier's push-pull output and tried to put the supply rail at the output, I wouldn't want to have relay contacts short it with a big spark welding its contacts, I would want the relay contacts to disconnect my expensive speaker. :lol:

I know. But as Nigel said, these really really really TOP end audio amplifier do not have speaker relay. What can you do in this circumstances except like he said, use the speaker as an expensive fuse.

 

[Nigel Goodwin]

I know. But as Nigel said, these really really really TOP end audio amplifier do not have speaker relay. What can you do in this circumstances except like he said, use the speaker as an expensive fuse.

I would suggest buying a more reasonably priced amplifier WITH a speaker relay, where you can't hear any difference anyway :lol: