How to make a hardware switch for stereo to surround speakers?

[ShadowTek]

I was thinking about making a hardware switch that would allow me to run
the front channel speaker outputs to the rear speakers when I'm only using
stereo media, then I can just flip a switch have the rear speaker receive
their usual rear channels. This will allow me to fully utilize all
speakers at all times.

I was thinking about getting a small box with 4 switches built into it,
and doing something like what I drew in this picture:
http://img14.imageshack.us/img14/152/speakerswitch.jpg (The yellow is
where each switch would be.)

The front speaker are always receiving their input, but there would be an
extra leg from the front speaker input that would be connected to the rear
speaker when the switch is in one position, and then that would be
disconnected and the rear channel input would be connected when the switch
is in the other position.

If all four switches are connected so that they have to all be thrown in
the same direction at the same time, that would be OK wouldn't it?

Anybody got a better idea?

 

[Andy]

I was thinking about making a hardware switch that would allow me to run
the front channel speaker outputs to the rear speakers when I'm only using
stereo media, then I can just flip a switch have the rear speaker receive
their usual rear channels. This will allow me to fully utilize all
speakers at all times.

I was thinking about getting a small box with 4 switches built into it,
and doing something like what I drew in this picture:
http://img14.imageshack.us/img14/152/speakerswitch.jpg (The yellow is
where each switch would be.)

The front speaker are always receiving their input, but there would be an
extra leg from the front speaker input that would be connected to the rear
speaker when the switch is in one position, and then that would be
disconnected and the rear channel input would be connected when the switch
is in the other position.

If all four switches are connected so that they have to all be thrown in
the same direction at the same time, that would be OK wouldn't it?

Anybody got a better idea?

Hi,

IF.... you're using a Creative sound card, it MAY (might be model dependant)
have the CMSS-3D Surround settings available from the Creative audio control
panel. What this feature does is to automatically convert stereo to
surround, and you can use a slider to specify how much volume you want sent
to the rear speakers so you can place yourself in the sweet spot.

Hope this helps


Andy

 

[Dave]

I was thinking about making a hardware switch that would allow me to run
the front channel speaker outputs to the rear speakers when I'm only using
stereo media, then I can just flip a switch have the rear speaker receive
their usual rear channels. This will allow me to fully utilize all
speakers at all times.

I was thinking about getting a small box with 4 switches built into it,
and doing something like what I drew in this picture:
http://img14.imageshack.us/img14/152/speakerswitch.jpg (The yellow is
where each switch would be.)

The front speaker are always receiving their input, but there would be an
extra leg from the front speaker input that would be connected to the rear
speaker when the switch is in one position, and then that would be
disconnected and the rear channel input would be connected when the switch
is in the other position.

If all four switches are connected so that they have to all be thrown in
the same direction at the same time, that would be OK wouldn't it?

Anybody got a better idea?

It won't work, and could damage your receiver. First, it would take two
switches on each speaker. Or, in your drawing, it would take eight
switches. That's because there is a + and - lead on each speaker. But if
you got that ironed out, there would be a bigger problem. You can't just
hook up two speakers in parallel on a single channel of your receiver. This
will cut the impedance of the (speaker) in half. Your receiver MIGHT handle
that OK, but more likely, you'd damage the amplifier, which is designed to
drive a speaker of a certain impedance level. For example, your speaker is
4 ohms (if it is). But you hook up two speakers in parallel, and now your
receiver is driving what is essentially one speaker with twice the number of
drivers, and that single speaker is 2 ohms impedance. Only one of two
things will happen at that point. It either works fine, or it destroys your
amplifier output stage. Only one way to find out which, but it's a heckuva
gamble.

Or the short version, don't do it. -Dave

 

[Dave]

It won't work, and could damage your receiver.

It will work, and probably won't damage the receiver (amp),
but it's possible it could damage it.

Yes, which is why I said don't do it.

Not necessarily, a SPDT switch would work, and are easy to
find.

Well yes, but I was assuming the OP wouldn't know what a single pole dual
throw switch was.

Except for some class D amps, the ground is common to all of
them, will not need switched.

And you're assuming that the receiver is a certain class of amplifier. I
don't know what class, probably B. If it's higher than that, what is it
doing in a computer hardware forum?

Actually no, more than likely the impedance of the speakers
is around 6 Ohms, rated for 8 Ohms, and hooking them up in
parallel won't damage the amp unless it is playing quite
loudly. If not playing so loudly it will handle the
current.

At BEST, the current will be increased. MTBF will increase, as well. And
that's at BEST.

If loud play or a safety precaution is warranted (if someone
else might have their hand on the volume knob), they could
be wired in series instead of parallel.

I wouldn't recommend it.

Why assuming it's 4 Ohms, when that is typically car
speakers?

I've seen plenty of computer speakers rated at 4 ohms. Not sure why, but
that is quite common. But then, if the speakers are being used with an
actual receiver, they could be 4 ohms, or something else.

Why assume a typical amp can't handle 2 Ohm loads
at moderate output levels?

Most aren't engineered to handle 2 Ohm loads...or even loads of "lower"
impedance. IE, it's not a good idea to run 4 ohm speakers off of a 8 ohm
rated amp.

Is it really, or it is only an amp and if it doesn't do the
job it is worthless towards the needed goal?

Well, if you want to go totally off-topic, I would suggest that the best
solution for the OP would be to buy a different receiver. Most cheap
receivers have output modes that would drive 4 or more speakers in stereo
mode or simulated surround mode.

But I was responding to the OP question about modifying existing hardware.
I still say don't do it. -Dave

 

[Andrew Smallshaw]

I was thinking about making a hardware switch that would allow me to run
the front channel speaker outputs to the rear speakers when I'm only using
stereo media, then I can just flip a switch have the rear speaker receive
their usual rear channels. This will allow me to fully utilize all
speakers at all times.

I was thinking about getting a small box with 4 switches built into it,
and doing something like what I drew in this picture:
http://img14.imageshack.us/img14/152/speakerswitch.jpg (The yellow is
where each switch would be.)

The front speaker are always receiving their input, but there would be an
extra leg from the front speaker input that would be connected to the rear
speaker when the switch is in one position, and then that would be
disconnected and the rear channel input would be connected when the switch
is in the other position.

If all four switches are connected so that they have to all be thrown in
the same direction at the same time, that would be OK wouldn't it?

Anybody got a better idea?

More information please. If you are using analog rather than
digital ouput on your soundcard put the switch in there. That is
a line-level signal which you can safely be a lot more carefree
with. If not, the discussion between Dave and Kony is about
something that is unlikely to affect you, but it is possible.

There are ways of resolving an impedance mismatch on your amplified
signal (that is what audio transformers are for) but it sounds as
if they would be above your head. In any case, at a stroke it
makes the project a lot more complicated.

If you must work with the amplified signal my hunch would be a 4PDT
switch will fit the bill when properly wired. However, the obvious
way of wiring one in, and geting the speakers in series to prevent
any possibility of overload, would invert the phase in one
configuration. This isn't a big deal _unless_ there are other
speakers that you haven't mentioned such as a subwoofer or centre
speaker. So, are there any more speakers?

 

[ShadowTek]

IF.... you're using a Creative sound card, it MAY (might be model
dependant) have the CMSS-3D Surround settings available from the
Creative audio control panel. What this feature does is to automatically
convert stereo to surround, and you can use a slider to specify how much
volume you want sent to the rear speakers so you can place yourself in
the sweet spot.

I *am* using a Sound Blaster Live! EMU10k1, but Creative only designed
their proprietary control panel for Windows systems, and I use Linux OSs
mainly.

ALSA *does* properly handle the EMU10k1, including surround sound output.
I even found a website describing how to properly configure ALSA to do
exactly what I am trying to do. However, I'm looking for a hardware
solution that would eliminate the need to configure each OS individually.

Also, if I can get this to work properly, I would like to apply the same
hardware solution to my home theater 4.1 surround receiver, as it natively
lacks the ability to generate this dual stereo effect for the rear
speakers.

 

[ShadowTek]

...my home theater 4.1 surround receiver...

That should have been 5.1

 

[ShadowTek]

...my home theater 4.1 surround receiver...

That should have been 5.1

 

[ShadowTek]

If you must work with the amplified signal my hunch would be a 4PDT
switch will fit the bill when properly wired. However, the obvious way
of wiring one in, and geting the speakers in series to prevent any
possibility of overload, would invert the phase in one configuration.
This isn't a big deal _unless_ there are other speakers that you haven't
mentioned such as a subwoofer or centre speaker. So, are there any more
speakers?

I was thinking about applying this idea to 2 different systems. One is the
4.1 system connected to my computer, and the other is a 5.1 system that is
connected to my TV, so using the line-level outputs from the sound card
wouldn't be applicable with my 5.1 receiver.

 

[ShadowTek]

...my home theater 4.1 surround receiver...

That should have been 5.1

 

[ShadowTek]

If you must work with the amplified signal my hunch would be a 4PDT
switch will fit the bill when properly wired. However, the obvious way
of wiring one in, and geting the speakers in series to prevent any
possibility of overload, would invert the phase in one configuration.
This isn't a big deal _unless_ there are other speakers that you haven't
mentioned such as a subwoofer or centre speaker. So, are there any more
speakers?

I was thinking about applying this idea to 2 different systems. One is the
4.1 system connected to my computer, and the other is a 5.1 system that is
connected to my TV, so using the line-level outputs from the sound card
wouldn't be applicable with my 5.1 receiver.

 

[ShadowTek]

If you must work with the amplified signal my hunch would be a 4PDT
switch will fit the bill when properly wired. However, the obvious way
of wiring one in, and geting the speakers in series to prevent any
possibility of overload, would invert the phase in one configuration.
This isn't a big deal _unless_ there are other speakers that you haven't
mentioned such as a subwoofer or centre speaker. So, are there any more
speakers?

I was thinking about applying this idea to 2 different systems. One is the
4.1 system connected to my computer, and the other is a 5.1 system that is
connected to my TV, so using the line-level outputs from the sound card
wouldn't be applicable with my 5.1 receiver.

 

[ShadowTek]

...my home theater 4.1 surround receiver...

That should have been 5.1

 

[ShadowTek]

If you must work with the amplified signal my hunch would be a 4PDT
switch will fit the bill when properly wired. However, the obvious way
of wiring one in, and geting the speakers in series to prevent any
possibility of overload, would invert the phase in one configuration.
This isn't a big deal _unless_ there are other speakers that you haven't
mentioned such as a subwoofer or centre speaker. So, are there any more
speakers?

I was thinking about applying this idea to 2 different systems. One is the
4.1 system connected to my computer, and the other is a 5.1 system that is
connected to my TV, so using the line-level outputs from the sound card
wouldn't be applicable with my 5.1 receiver.

 

[CBFalconer]

.... snip ...


Is it really, or it is only an amp and if it doesn't do the
job it is worthless towards the needed goal?

It would be safer to wire them in series, but any decent amp
should be able to drive a parallel pair of typical 8 Ohm rated
speakers per channel. If by chance it did blow the output
transistors, one could replace them with higher current rated
parts if endowed with a soldering gun, or of course use a
different amp. If someone is extra paranoid, they could even
place a low ohm power resistor in series with the load (speakers
in parallel) to prevent the amp seeing a load below the chosen
resistance. One way or the other, it's quite do-able.

In fact, audio amplifiers normally have a much lower output
impedance than that of the receiving speakers. The ratio is known
as the damping factor, which I would expect to be in the 10 to 20
area. So output speaker amplitude will probably be highly
dependant on the resistance of the connecting wires. There should
be no damage. The result may be distortion.

 

[Andy]

You probably have at least two separate channels for an A and a B set of
speakers.
If you are going to switch anything I would switch the B output with the
rear speakers.
Try that first in any event.
There *will* be a beat problem wher the sound from the front and back tend
to amplify and cancel each other. This might limit where you can sit to
listen.

I was just thinking about a similar solution...

If ShadowTek has an amp that can switch between speaker set A and B he could
splice the cables coming out of chan A to Fronts and insert them into the
front outputs from speaker set B and then splice the cables coming out of
chan A Rears into the same chan B Fronts output.

In other words...

When using speaker set A the Front out goes to Front speakers and Rear out
goes to rear speakers as per norm.

When using speaker set B the Front out goes to Front and Rear speakers.

This way set A and B share your current wiring to speakers so no dual
cabling or having to lift the existing out from under the carpet.

CHAN A Front -> Front Speakers
CHAN A Rear -> Rear Speakers
CHAN B Front -> Front Speakers
CHAN B Front -> Rear Speakers


Andy

 

[Mike Painter]

I was just thinking about a similar solution...

If ShadowTek has an amp that can switch between speaker set A and B
he could splice the cables coming out of chan A to Fronts and insert
them into the front outputs from speaker set B and then splice the
cables coming out of chan A Rears into the same chan B Fronts output.

In other words...

When using speaker set A the Front out goes to Front speakers and
Rear out goes to rear speakers as per norm.

When using speaker set B the Front out goes to Front and Rear
speakers.
This way set A and B share your current wiring to speakers so no dual
cabling or having to lift the existing out from under the carpet.

CHAN A Front -> Front Speakers
CHAN A Rear -> Rear Speakers
CHAN B Front -> Front Speakers
CHAN B Front -> Rear Speakers

My reciever allows A or B as well as A and B.
If A is the "main" set, your idea should work if there is no signal from A
to the rear and probably would work anyway. If there is any delay to the
rear it might give a bit of strange sounds.

 

[ShadowTek]

I was just thinking about a similar solution...

If ShadowTek has an amp that can switch between speaker set A and B he
could splice the cables coming out of chan A to Fronts and insert them
into the front outputs from speaker set B and then splice the cables
coming out of chan A Rears into the same chan B Fronts output.

lol, that just reminded me that the amp for my 4.1 PC system automatically
activates dual stereo if the rear speaker input is unused. Unfortunately,
the I can't just install a cut-off switch in the rear channels input line
since the dual stereo trigger works by detecting the physical presence of
the plug, and not by the input of a signal. (I just tested that by
unplugging the rear channels line at the sound card, while leaving the amp
side of the line plugged in.)

So, if I don't make some kind of switch-box, the simplest solution would
be just plugging and unplugging the rear channels input line when
switching between media types, although that's a little inconvenient to
have to do all the time.

This way set A and B share your current wiring to speakers so no dual
cabling or having to lift the existing out from under the carpet.

lol, all my wiring is run up the wall, stapled to the ceiling, an spread
out all over the place, but I don't really care how it looks as long as it
works.

CHAN A Front -> Front Speakers
CHAN A Rear -> Rear Speakers
CHAN B Front -> Front Speakers
CHAN B Front -> Rear Speakers

My amps only has one set of outputs for each speaker. I've never even
owned a system that has any more than one set of outputs per speaker.