Is it acceptable to 'jumper' speaker wire through a switch?

[ChrizK]

Firstly, I hope it is ok to discuss the wiring of speakers here. TBH my ignorance in all things electrical knows no bounds, and I am guessing it is a discussion about ohms, of which I have less idea about than watts.
To that end, I would appreciate any responses in the simplest of terms. Once again, I apologise if this is the wrong forum, as I suspect it is attended by many large brains that would rather speak in 'scientific' terms. However, my question is more 'theory' rather than 'straight electrical'.

The question relates to using a sound system with a TV on one wall which is perpendicular to a projector screen on another. The TV has Front Left and Front Right speakers located above it ...the idea is to 'switch' the Front Right to becoming Front Left (the projector), and Front Left to a separate speaker.
I bought a two-way speaker switch box from Amazon. I guess it is obvious to say that this is normally used to switch the input to two pairs of output.
In my case, I have speaker cable running to a single speaker on Pair(1) Right BUT ALSO 'jumpering' to Pair(2) Left.
As you may surmise, Pair(1) Left goes to a speaker, and Pair(2) Right goes to a speaker ...so three speakers in total.

If I think of this as 'direction of flow' when I select Pair(1), the Input(amp) is directed to Pair(1) Right speaker, and is 'dead ended' to Pair(2).
I turn off Pair(1) and select Pair(2), in which case, Input(amp) is directed to Pair(2) Left speaker, and Pair(2) Right jumpered to the twisted/join in Pair(1) speaker.

Hopefully I have explained that well enough (don't think a picture would actually provide any clarity)

This works ...but, sometimes my speakers just 'cut out'. Strangely (and please don't shout at me), if I increase the volume on the TV, it suddenly comes on and I deafened until I quickly turn the volume down. My initial theory was that it was the amp cutting out, but I considered that turning the volume up shouldn't resolve the problem, and so I believe it to be the switch.

So, my question is 'could this be considered a legitimate use of the switch, or am I doing something so stupid that I should expect it to cut-out?'

Thanks for your time.

 

[James]

i think a diagram would be helpful here.

 

[DPG]

i think a diagram would be helpful here.

Not just me then!

 

[davesparks]

If turning the volume up cures it then I'd hazard a guess at a loose connection somewhere.

 

[ChrizK]

If turning the volume up cures it then I'd hazard a guess at a loose connection somewhere.

In my ignorance, I was thinking along the same lines. Given that the speaker wire is just terminated into standard 'grips', I was thinking that it is possibly an internal fault with the switch. However, I was concerned that I was causing my own problem by attempting to do something that was fundamentally 'silly'.

The switch does allow Pair(1) and Pair(2) to be selected, ie both on. I suspect this might cause issues and so I have put a note on it to say switch both off first, before selecting the required pair. Not wishing to blow a speaker ...or even the amp(?), I have never tried having them both on.
Theoretically (appreciating that you have to visualise what I am attempting), could I damage the speaker or amp by having both pairs 'on'?

 

[DPG]

The main way any damage could be done when combining speakers is if you have multiple speakers wired in parallel and it reduces the impedance (resistance to all intents and purposes in this case) to a value lower than the amplifier can handle. This could damage the amplifier.

 

[ChrizK]

i think a diagram would be helpful here.

 

[ChrizK]

i think a diagram would be helpful here.

I hope you are not requesting a switch diagram, as I am afraid I am not competent. Hopefully the above is adequate.

 

[DPG]

View attachment 105656I hope you are not requesting a switch diagram, as I am afraid I am not competent. Hopefully the above is adequate.

Ah I see. No, don't connect the two speaker switch outputs together. That is what will be causing your problem.

 

[ChrizK]

The main way any damage could be done when combining speakers is if you have multiple speakers wired in parallel and it reduces the impedance (resistance to all intents and purposes in this case) to a value lower than the amplifier can handle. This could damage the amplifier.

If my diagram is sufficient, is that effectively what I am doing?
Given the switch allows both pairs to be 'on', would it also result in the reduction in impedance you mention?
Or, could it actually enhance it and negate the problem?
If so, given my 'misuse' of the switch, could it make things better or worse?

TBH This is where Ohms start to lose me ...why the reduction can cause damage ... although your wording perhaps has given me a clue. Is it that having more and more speakers reduces the resistance, so 'more gets through'? Again, I am not totally sure 'of what' ...is it equivalent to more 'power' getting through, and therefore the much spoken about 'blowing up the amp'?

 

[DPG]

I still can't quite picture what exactly you are trying to achieve with the whole left/right/crossing/whatever. But you don't want to connect the left speaker output of the TV with the right speaker output.

I'm pretty certain you won't need a speaker switch box either, as you are wanting it set up permanently - you don't need any switching. The worse you may need is a couple of dummy load resistors I reckon.

 

[ChrizK]

Ah I see. No, don't connect the two speaker switch outputs together. That is what will be causing your problem.

Oh ...
I know I asked not to have a technical explanation, but would you mind explaining a bit more?
ie, why does the sound cut out, and am I potentially damaging the amp or speaker?
Also, is there a reason why increasing the volume makes it come back (and does that too increase the risk of damage)?

Is it the case that there is no possible way to achieve what I want, other than having two pairs of speakers (resulting in two speakers right next to each other, which is what I wanted to avoid)?

 

[ChrizK]

...as you are wanting it set up permanently ...

Perhaps this is where the confusion is ...it isn't permanent. Either I will be watching TV with one pair, or the Projector with one 'switched' speaker + the additional speaker on the right of the projector. Hopefully that makes sense.

 

[DPG]

Perhaps this is where the confusion is ...it isn't permanent. Either I will be watching TV with one pair, or the Projector with one 'switched' speaker + the additional speaker on the right of the projector. Hopefully that makes sense.

Ah sorry, I didn't quite grasp that bit.

However you do this, you can't cross connect the left output with the right output. That will be why you have the cutting our problem.

I would reconsider to be honest - for the best sound results you want a matching pair of speakers in use and positioned properly, especially when you are using the projector. Also then you could use your switch box as it is intended.

The 'technical' reason is that you are interconnecting the outputs of two separate amplifier circuits. They designed to feed two separate speaker loads.

 

[davesparks]

However you do this, you can't cross connect the left output with the right output. That will be why you have the cutting our problem.

Unless ive misunderstood that switch box selects between pair 1 or pair 2. So as its drawn a cross connection doesn't happen because only on of the linked sets of terminals will ever be connected to the amp.

If it was a cross connection it shouldn't work at all, not just cut out after a while.

 

[DPG]

Unless ive misunderstood that switch box selects between pair 1 or pair 2. So as its drawn a cross connection doesn't happen because only on of the linked sets of terminals will ever be connected to the amp.

If it was a cross connection it shouldn't work at all, not just cut out after a while.

Yes that's a fair point. To be honest it has confused me this thread.

I think some phase reversal might occur though - I need to draw it out but I'm going to have a beer instead!

 

[ChrizK]

Unless ive misunderstood that switch box selects between pair 1 or pair 2. So as its drawn a cross connection doesn't happen because only on of the linked sets of terminals will ever be connected to the amp.

If it was a cross connection it shouldn't work at all, not just cut out after a while.

Appreciate the input ...almost a pun there.
It is unfortunate that I can switch both Pair(1) and Pair(2) into the on position at the same time. Although I don't fully understand resistance, I had a feeling this would be a bad thing to do ... so always ensure both are off before selecting one or the other. Again, I don't fully appreciate the technicalities of cross-connection, but my 'theory' was that having one or the other would effectively be 'straight through' and not a problem (accepting the risk that I may inadvertently select both and blow something!). Wasn't Scotty always warning Kirk about Phase Reversal
It is interesting reading the comments in the linked Amazon listing for the switch, as I note that the negative reviews mention things like "When switching a speaker output on, one channel can occasionally (often) not switch on. Rocking the switch back and forth can then convince it to come on, but that's far from ideal".
Given your comment and the information from @DPG , I am thinking that, although there is a significant risk having both 'on', the theory is ok, and it is very likely to be poor manufacturing. It is a great shame we allow Chinese manufacturers to sell items with little to no quality control, invariably producing unsustainable waste

And I do appreciate @DPG advice to reconsider, although I am no 'audiophile', and only had a practical solution in mind. TBH I don't use the projector screen that much, and would rather has less kit (and the middle speaker is by the TV, which would send said audiophile to an early grave).

Really appreciate everyone's time to help explain. Thank you.

Being really cheeky, would you guys know anything about RF interference?

 

[Lucien Nunes]

OK, I can guess what is going on here, disconnect it in case you damage the amp. I suspect the speaker switch does not work the way you have assumed, i.e. that it routes the signal to either output 1, or 2, or both in parallel.

Instead, a normal 2-way speaker selector connects both sets of speakers in series all the time, but short-circuits (i.e. bypasses) the speakers that are not in use. If both are selected, it does not short anything, and if neither, it open-circuits the amp. There is a reason that it works this way: With both speakers active they are connected in series so the impedance seen by the amp is higher than either speaker alone, rather than lower as it would be if they were in parallel. Also, with only one set active, the speakers that are not in use are shorted to damp the cones against sympathetic resonance.

This being the case, your problem is not about impedance but about the series configuration of the switching, in which all speakers are always connected to the amplifier even when bypassed. In this non-standard application, the cross-connection for the 'middle' speaker is tying the two amplifier channels together which can damage it, and could cause the cutting in and out that you describe as one or both amp channels go into protect mode and stop fighting each other, or all sorts of unsavoury effects could be going on. What you want to achieve is perfectly feasible, but we will either have to start with a different switch, or modify this one. Please post some pics of the innards and if it is possible to make the necessary modification I will guide you how to do that.

If for any reason your switch does not work the way I describe, we can pursue alternative explanations, but I thought I would jump on that bandwagon in a hurry because of the potential for damage. Possibly, the switch is configured for parallel switching, which is unusual but not impossible. Then a likely explanation for the sound to cut-in at high volume is that the product is substandard, using switch contacts that are unsuitable for audio, which are maintaining a high resistance until a certain minimum 'wetting voltage' is placed across them by increasing the output.

 

[ChrizK]

What you want to achieve is perfectly feasible, but we will either have to start with a different switch, or modify this one. Please post some pics of the innards and if it is possible to make the necessary modification I will guide you how to do that.

What a fabulous offer. Hopefully I can provide what is needed at the weekend ...TBH 'when' it gets to the point of soldering in components, I may get cold feet, but I find the discussion very informative.

 

[ChrizK]

If for any reason your switch does not work the way I describe, we can pursue alternative explanations, but I thought I would jump on that bandwagon in a hurry because of the potential for damage. Possibly, the switch is configured for parallel switching, which is unusual but not impossible. Then a likely explanation for the sound to cut-in at high volume is that the product is substandard, using switch contacts that are unsuitable for audio, which are maintaining a high resistance until a certain minimum 'wetting voltage' is placed across them by increasing the output.

Hi, I cannot apologise enough given your good intentions. I totally appreciate that this was raised in January, and my interest appears to have been lost. Life issues keep getting in the way of my 'projects'. In this case, the switch has not been used for the fear of breaking things, but I would still like to reach the solution. To that end, I have included some photographs. Funnily enough, since taking the unit to pieces, it seems to have stopped cutting out, but that is a limited observation due to lack of use.
NB Stupidly or not, I did actually try switching 1 and 2 on at the same time, and it seems to result in 'all' speakers working (I didn't have the confidence to play with this, as it is not intended use, so no idea if reduced performance, or even if it causes a problem, as I switched back to 'position 1' quickly).
As you will see, the wiring is incredibly simple. As it looks 'secure', I guess the actual rocker switch is not good quality, hence causing the cutting out and my concerns. I would however appreciate your expert point of view, if you can forgive me.

NB You will see I took the pictures in April, and still didn't have time to get back here ... really sorry
Furthermore, the casing is horrible and I didn't manage to align it properly when putting back together (as feared).