Hello there,

I've recently started a small business and have a shop with 4 small floors all needing music in. We have a very limited budget so need to spend as little as possible which rules out all normal multi-room solutions.

I have 4 small floors, all needing a small stereo pair of speakers running from one source.

So, if I get a four channel amp like this:
http://www.richersounds.com/product/amplifiers-receivers/teac/ag790/teac-ag7090

Then put 2 sets of 8omh speakers into each pair of channels (totaling 4 pairs of speakers). Speakers like this:
http://www.richersounds.com/product/bookshelf-speakers/gale/3010s/gale-3010s-bch

That that would mean 4ohms into each pairing and the amp wouldn't blow right?

Any help would be much appreciated. All my local High-Fi shops are telling me NOT to do it but I get the feeling this is just because they don't want to be held responsible to any unfortunate consequences.

It's so hard for small businesses these days, every penny counts!

Thanks so much,

Welcome Nigel. I would think* you'd be ok if you're not running the speakers in parallel off of the same channel (where the ohms would drop considerably) but with 4 channels. Alan Lofft wrote an article that may help you.

You may possibly require an impedence matching selector switch(not expensive at places like Parts Express)....I've never tried this, so hopefully someone with more knowledge will pipe in.

Using a speaker selector switch should work.

Here's an article refering to them.

Thanks for your help!

Should something like this connected to a standard inexpensive amp and 4 sets of speakers do it?

http://www.amazon.co.uk/4-Channel-Stereo...4881&sr=1-1

Blimey, this bit of kit's only £20, would this do the job for me?

http://www.maplin.co.uk/4-way-stereo-speaker-switch-box-97929

Nigel,

I'm not familiar with that particular switch box, but the specs mention that the box maintains impedance at 4 ohms, so you should be alright with it provided you use an amplifier/receiver that will drive 4 ohms without triggering its protection circuitry.

Look at Denon, which here at Axiom, have been very reliable driving the Axiom 4-ohm M80 v3 tower speakers.

Impedance-matching switch boxes do involve sonic compromises, but for your application it should be OK.

For better quality, you could, as my colleague Brent mentioned to you in the private email, go to Russound or Niles for constant-impedance switchers.

Regards,
Alan

I have to ask, why not connect the speaker pairs in series and not worry about the effect of dropping to 4 ohms? To wire in series you'd connect each pair as rcv+ to spkrA+, spkrA- to spkrB+, spkrB- to rcv-.

Wired in series would present a 16 Ohm load. Not really a big deal, but you'd need to increase the volume level to get the same output.

The real problem with wiring speakers in series, is they are not a fixed 8 Ohm load, but a reactive load that changes impedance depending on the frequency of the signal driving them. The driver's native impedance is balanced with the crossover network to allow a linear frequency response. When the loads in are series with each other, the impedance peaks grow even larger, while the low points don't pile up as much. Since the peaks usually exist in the treble range, this would have the effect of rolling off the highs, and thus causing a less than linear response.

You really want each speaker to be connected to its own amplifier output, no parallel wiring, and definitely no series. Impedance-matching switches only go so far. They're still not some thing you want involved in a high quality playback system. But for in-store music, who cares? And he's not thinking about using Axiom speaker in the shop either; quality is not high on the list.

I would be looking at using a multi zone/channel amp to run all those speakers, something like this......

http://www.ada.net/products/ht/ptm_8100.php

Nigel, welcome. Since you haven't really described "needing music" in detail, I'm left wondering if the discussion so far hasn't been at an unnecessarily complex level. If the music isn't directly related to your business activity, but is just for a pleasant background, it would seem that placing an inexpensive compact stereo system in each room might be satisfactory. This would probably be less expensive and certainly would be less complicated.