[sparktikus]

hello i have teac cd /dab amplifier crh240
i need to run 8 single speakers (4 pairs) off the one stereo output..(output says 6 ohm)
all speakers are 8 ohm and i will be connecting all speakers up to a radio shack 4 way selector switch

Radio Shack 40-137 4-Way Speaker Audio Selector Switch - eBay (item 290378156314 end time Apr-10-09 14:12:44 PDT)

can i do this?
will i damage the stereo?
if one pair of speakers were 4 ohm would it make a diffference?

thanks

[Moonfly]

Hi and welcome to the forums.

If your using the switcher so only 1 pair at a time runs then you wont have any problems. The 4 ohm speakers arent going to be any good for you really though as your amp will struggle to drive them properly. Basically the lower the ohm figure the harder they are to drive.

If your planning on running more than 1 pair of speakers at a time its whole different ball game though.

Jees its 1 o'clock, I'm going bed

[BlueWizard]

Take the impedance of one speaker, and divide it by the number of speakers on that amp channel, and you will have the total load impedance, assuming all speakers are the same.

As an example, FOUR 8 ohm speakers connected in parallel -

Rt = 8/4 = 2 ohms

Your amp is not very likely to handle 2 ohms and survive.

Expand on what you have already said if you want more information.

Why are you doing this?

As already asked, are you planning to use more than one or two speaker sets at once?

What amp?

What speakers?

and...again...why?

Steve/bluewizard

[sparktikus]

I am planning on using all speakers on at the same time, and generally just using the radio shack selector box as a glorified connection box for all speakers
I want 8 speakers all on at the same time, these are for use in a shop
any ideas

thanks

[Moonfly]

You'll need 2 amp capable of running at 4 ohms, you could then add 4 speakers to each amp as long as they are 8 ohm rated speakers. Of course you would need some method of controlling the amps so at least one would have to be integrated.

What amps do you have if any, same question for the speakers. If you need to buy stuff what sort of budget are you looking at. With the speakers being i a shop I take it they arent ever going to be played above moderate volumes which helps. I take it sound quality doesnt really matter as long as its decent enough for a shop/ There really are a whole heap of options but if your answer those questions you'll get some good suggestions.

IMO, that Teac just isnt going to do the job.

[BlueWizard]

When MoonFly says '...4 speakers on each amp...', he means two speakers on each amp channel for a total of 4 attached to a stereo amp.

It is possible to wire four speakers in such a way that the total per channel inpedance is equal to that of a single speaker.

You wire the speakers in gangs. Meaning you wire two speakers in parallel, then take those two gangs of two, and wire them in series.

Two 8 ohm speakers in parallel equals 4 ohms. Now take two gangs of 4 ohms, and wire them in series, and the total is 8 ohms.

This can be done in two gangs of two in parallel, then connected in series. Or, it can be done in two gangs of two in series, then connected in parallel.

This assumes all the speakers are 8 ohms. Also, this would allow you to use just one stereo amp.

We still need a few more details to give a clear and complete answer to your question.

Steve/bluewizard

[sparktikus]

yes because it is a shop it will be moderate background music not loud
is it a no no to connect all speakers to radio shack selector box
i dont want to rewire really as i have already ran all cables back to this selector box

is there any kind of splitter to buy that will do the job

thanks

[BlueWizard]

You can wire the speakers as I've shown them in my diagram, back at the amp.

If all the wires converge at the amp, that actually makes if very easy to wire as my diagram indicates. You just need to know which wires go to which speakers.

I will also warn you that you can't NOT want to do something simply because you view it as inconvenient. We are dealing with electrical and physical realities here that must be adhered to. You can't wire large gangs of speakers willy-nilly. It has to be done in a logical and systematic way.

The Radio Shack switch box doesn't help UNLESS, it is wired for impedance matching. That is, it uses a combination of resistors and wiring as indicated in my diagram to keep the impedance fixed within an acceptable range for most standard amps.

Steve/bluewizard

[sparktikus]

i only have 1 output channel of the amplifier unit
is it possible to wire 8 speakers into this???
thanks
and how does impedance matching work
thanks

[ben.bayliss]

TBH I'd be looking at using a cheap-n-nasty amp designed for PA use. None of them have trouble at 4ohms, and most would be happy within reasonable limits at 2ohms.

You may think that being a shop we're talking low levels, but just think about how loud the insides of many shops are once you've got music+outside noise+talking+people moving around etc. etc... It's probably going to be running quite loud.

Can't see how the switcher helps you at all tbh, apart from acting like a posh terminal block for cramming all the cables in to!