Amp for garden rock speakers

Mark M · 10 Apr 2020 at 15:07

I’ve got 4 outdoor rock speakers that were given to me but they have no information with them so I don’t know the ohm rating or wattage. They will only be used for quiet background music so less concerned about the wattage but wondering what amp would be suitable? Ideally looking for something as budget friendly as possible.

I’d like to have 2 zones with 2 speakers in each zone all playing the same source (Amazon echo dot). Could this be achieved by connecting 2 speakers to one channel of an amp and then other 2 to the second channel?

The next issue I have is that I wired in some cables when the patio was being laid but I only put 2 x 2 core cables down and there’s no way of pulling more through. Can the speakers be wired one after the other? Is that wired in series? Not really sure on the correct terminology but any help appreciated. Worst case scenario I could just use 2 of the speakers.

lucid · 10 Apr 2020 at 17:30

Mark M said:
I’ve got 4 outdoor rock speakers that were given to me but they have no information with them so I don’t know the ohm rating or wattage.

The chances are that the speakers are either 4 Ohm or 8 Ohm, but could equally be 100V line, and so that has an immediate implication for the sort of amp you should buy. It would be better to work from a position of knowledge, so, if possible, check out Ebay or Google images to see if you can find a match visually, then work from there. You could also try opening one of the speakers. If 100V Line, then there'll be a transformer in each.

Mark M said:
I’d like to have 2 zones with 2 speakers in each zone all playing the same source (Amazon echo dot). Could this be achieved by connecting 2 speakers to one channel of an amp and then other 2 to the second channel?

For that to work, the source signal would have to be converted to mono before reaching the amp (or buy a s/h amp with a mono switch) otherwise your stereo mix will be split across the two zones. That would sound odd.

Mark M said:
The next issue I have is that I wired in some cables when the patio was being laid but I only put 2 x 2 core cables down and there’s no way of pulling more through. Can the speakers be wired one after the other? Is that wired in series? Not really sure on the correct terminology but any help appreciated. Worst case scenario I could just use 2 of the speakers.

Series is safer. The speaker impedances add-up, so if you have two 4-Ohm speakers, the combined impedance is 8 Ohms and that'll make most amplifiers happier than 2x 4-Ohm speakers wired in parallel resulting in a 2-Ohm load.

Here's how to wire: LINK

Your amp choice depends largely on your budget, but there's obviously a lower price/performance limit. The concerns with outdoor speakers are the efficiency; and how much extra power they need just to play quietly because the sound dissipates quickly where there are no walls and ceiling to contain it; and competition from ambient noise; and the voltage drop across the cables because the signal has to travel a long way.

Some will suggest small T-class amps simply because they're cheap. On the plus side, apart from price, they are fairly tolerant of low Ohms loads. What they're not good at is generating a lot of power cleanly so as to cope with low efficiency speakers where they need a lot of power to fight the background noise and voltage drop over the cabling. The other issue is that the manufacturer/reseller claims for power are a complete work of fiction. Whatever they're quoting in Watts, divide the figure by 10. That'll give you the real-world operating power.

What is your budget?

Akagi · 10 Apr 2020 at 17:36

Can you easily take them apart? Specs should be on the back of the speaker magnet.

Mark M · 11 Apr 2020 at 08:25

Thanks for the replies.

I got the speakers off my father who thinks he got them from B&Q or Homebase so I’m guessing they aren’t going to be up to much but better than nothing I guess.

He used to run them off a little Sony hifi system so I assume they aren’t 100v? The speakers are completely sealed so I can’t open them up sadly.

Budget for an amp would be under £150 if possible?

@lucid - the link you posted doesn’t seem to work.

thabks again

lucid · 11 Apr 2020 at 11:29

Now you've added some more info, yes, they're just low-Ohms speaker rather than 100V line. These sound a bit like the rock speakers B&Q was selling in the mid-2000s. They were £25/pr, so likely to be a single driver in each. If he was running all four from a Sony midi/mini Hi-fi then you shouldn't have much trouble with a more powerful amp.

Try the wiring link again now.

Mark M · 11 Apr 2020 at 16:31

Yeah sorry, should have added a bit more detail in the OP.

Can you suggest a suitable amp that has a mono switch? I’ve not been able to find much in the budget range (assume it’s a higher level feature) but there are some PA amps that have a mono feature but not sure if that means it converts the 2 channels into one mono channel with twice the power which won’t be suitable?

lucid · 11 Apr 2020 at 23:30

A PA amp in bridged mode won't do what you want. It expects a source signal on one channel only; so the signal has to be made mono before it gets to the PA amp. All bridge mode does is take a mono input, and then combine the two speaker outputs to a single output so there's more power. i.e. a 2x 100W stereo amp that drives two speakers becomes a 1x 200W mono amp driving a single speaker.

Regarding an amp with a mono switch, you're right, you're very unlikely to find it on a new stereo amp within your price range. I've even looked at the odd-ball Chinese karaoke-type amps (not that I'd recommend them) but found nothing.

I could probably put together an amp and external box to convert stereo to twin mono so you could drive both speaker cables with a very robust 8 Ohm 50W per channel signal and fit it within your budget, but it would mean looking at a good used amp, but that's not a solution for everyone so you might not be interested.

I take it you'll control volume for the Echo Dot from the app?

Mark M · 12 Apr 2020 at 07:56

Ah ok that makes sense, thought I may have been able to pick up a cheap pa amp when I saw mono mentioned.

I don’t mind going down the second hand route with audio equipment so if you could suggest some models to keep an eye out for I’ll check ebay and av forums etc for them.

Yes I was planning on using my phone to control everything via the Alexa/Spotify app.

lucid · 12 Apr 2020 at 11:50

You can still use a cheap PA amp, just run it in stereo mode (2 channels in - two speakers out) and then add a Monacore stereo to mono converter at the front end.

Mark M · 13 Apr 2020 at 09:10

Is there any benefit of going for a pa amp over a hifi amp lucid? I have no preference either way. Given the quality, or lack of, of the speakers will it make any difference?

Would say the Pioneer A10AE offer anything over this Behringer amp? Appreciate the stats are way off on the Behringer but I’m not looking for loud volume in the garden.

maybe the other consideration is that if the cheap rock speakers break or sound absolutely rubbish I might replace them with something better further down the line so an amp that could pair with better speakers may be sensible?

Thanks.

lucid · 13 Apr 2020 at 11:32

Pioneer - reasonably accurate specs, creature comforts such as tone controls, multiple inputs. Probably going to run a bit cooler, but that's only a guess. Sound quality: If you A/B demoed indoors with decent speakers then my gut feeling is that the Pioneer would sound sweeter, and the Behringer more raw and ragged, but not unlistenable by any means.

Behringer - more basic, more of the budget going in to the power side of things, despite the fantasy power figures it will be a little more powerful than the Pioneer. The voltage rail tracking should help keep the heat dissipation down when the amp is on but not actively driving the speakers, but it's all relative to similar PA amps without the feature rather than being directly comparable with Hi-Fi amps.

One important consideration is what happens when the power switch on either amp is pushed. I suspect the Behringer might give quite an audible thump whereas the Pioneer won't.