Help with shop speaker system


Novice Member
I am trying to help my parents with their speaker system in their salon but I have no idea what I’m doing so if anyone can provide any advice it would be greatly appreciated.

My dad bought a Denon RCD-M39DAB some years ago and they’ve been using that to listen to the radio/play cds/play music on a usb. It’s a small salon with 3 rooms and each has a wired speaker. On the back of the Denon there are black negative and red positive connectors for the right speaker and black negative red positive connectors for the left speaker. My dad has wired one speaker to the right connectors, and cut and joined the other 2 speakers to the left connectors so that the twin cables coming from the back of the 2 speakers have been paired together and then connected to either positive or negative twin cable connected to the Denon left speaker connectors.

Does this mean that when a stereo sound is being played, you have a different sound coming out the single speaker connected to the right and the two connected to left? What would I need to do to get all speakers to produce the same mono sound? Also I am assuming it doesn’t matter if either of the twin cables coming out the back of the speaker is connected to positive or negative, as long as the circuit is complete a sound is produced?

One of the speakers connected together appears to be louder than the other 2, however when the volume on the Denon is reduced all the speakers volume goes down so the volume for the other 2 speakers ends up being not high enough. When the cut cabling is moved around this appears to reduce the sound although this may just be due to a bad connection as the copper wires have just been wrapped around each other.

Is there a way of connecting a potentiometer to just one of the speakers? Alternatively if I buy something like the Adastra mixer amplifier would I be able to connect all 3 speakers and independently control their volume? Do these have build in FM radios or would I be able to connect it to the Denon?

Ideally I want to keep cost to a minimum and use what they already have, and the Denon cost around £240 at the time so want to make the most of it. However, if we were looking to get a completely new system and idea how much this would cost?

Also some channels on the Denon FM radio stop and start as you’re listening. I’m assuming this is due to bad signal? They’re using the twin wire copper cable aerial that came with the Denon. Not sure if it’s any good? If I were to change this to some sort of indoor DAB aerial this should resolve the issue? Any suggestions on aerials?

If anyone can provide any assistance that would be greatly appreciated. Thank you very much.



Joe Fernand

Distinguished Member
AVForums Sponsor
Highly surprising the amplifier has not fried one or more channels looking at the spliced wiring.

Time to disconnect everything from the mains power socket and start over.

You have a stereo amp therefore you would normally install three pairs of speakers (one pair per zone) not three speakers.

As you surmise unless you have the system set to 'mono' you are hearing the audio from one channel in one zone and the audio from the other channel in the other two zones.

Can you add an additional speaker cable and in-ceiling speaker to each zone?



Active Member
Sounds to me that you might needto consider something new before your parents’ customers end up with the Sound of silence. LoL. Have you thought about a cheap multi room system such as the audio pro Addon C3 . This would depend on them having wi-fi present. Here’s an example of a package although this comes with the larger C5 speaker so you could probably get two C3s and get a cheaper deal if you shopped around.


Well-known Member
AVForums Sponsor
My friend owns a salon and he has purchased three Alexa's which work perfectly in his unusually shaped room and I suspect that will be the same for what you are trying to achieve.

Yes I know it may lock you into a subscription service, but having heard it as background music, you cannot fault the simplicity of the system


Distinguished Member
You have the completely wrong choice of equipment for the job. I'd agree with @ShanePJ, replace with three Echo Dots & stick with radio. Their clients can then choose what radio station to listen & the only extra cost is a PRS/PPL licence, which they should have anyway.

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