5.1 system possible with only 3 separate 2 core cables?

[jdawson2402]

I would like to set up a 5.0 / 5.1 surround sound system in our new loft bedroom. We asked the electrician to wire in appropriate cables within the wall and ceiling for 4 in-ceiling speakers (which would provide 2 x rear and 2 x front speakers). We can positiion a centre speaker and sub-woofer separately.

But the electrician has only run 2 separate lengths of 2 core wire, 1 for the left channel (2 speakers) and 1 for the right channel (2 speakers). I think that means we have to attach a cable to the front speaker and then run it on from the front speaker to the rear speaker (rather than having independent cables from the AV receiver direct to each speaker).

I do not know if this 2-cable setup for front and rear speakers can support surround sound with a 5.1 AV receiver. Or does this mean we can really only now support stereo sound. The plaster board is in and it's impossible to add 2 further 2 core cables without removing the plaster board!

If this means only stereo sound, can we still get decent TV and movie audio if we hook it up to the 4 in-ceiling left and right channels (plus a centre speaker and sub-woofer)? Is that then a 3.1 system?! Or would we better off simply using the TV's own speakers given the cabling issue?

Any advice welcome, thank you...

 

[MajorFubar]

You say he's only run 2 separate lengths of 2 core wire. Is it possible you left him with the impression that he only had to install cable for the two rear channels and that you would do the front 3.1 separately?

 

[jdawson2402]

It's certainly possible that I gave him the wrong impression when we first discussed the setup! I'm unfortunately no expert in AV or surround sound, although I now understand a lot more than I did when we discussed wiring a couple of weeks ago. I also (incorrectly) assumed that he as electrician would understand the cabling requirements for "surround sound" TV knowing that we were putting 4 speakers into the ceiling. But he admits that he did not and thought it would be OK to run 2 channels - one left and one right. Unfortunately we now cannot add any additional cabling (to either the position of the front or the rear speakers) because the cable would need to run through ceiling joists that now sit behind plasterboard and fresh plaster!

So I'm wondering if we can still salvage any sort of home cinema experience with 4 ceiling speakers but only 2 ceiling cables! As I said, we can still add a centre speaker under the TV and sub-woofer from the AV received, if needs be...

 

[stavvy]

If you can still access the speakers themselves then you can get adapters that effectively turn the speakers into wireless speakers. I have no experience of them myself, or indeed have I read into the workings of them so they may not be appropriate, I'd like to imagine there would be something along these lines to sort you out.

A quick google found this:

http://www.tuaw.com/2014/04/01/logitech-bluetooth-audio-adapter-makes-any-speaker-wireless/

I'm sure there are other options. Good place to start reading though! Good luck! Also with ceiling speakers installed you could get more speakers for 7.1 and have a full on dolby atmos setup at your fingertips

 

[stavvy]

actually may have got it wrong, something more like this is what you need (i think)

http://www.amazon.com/KEF-Universal-Wireless-Discontinued-Manufacturer/product-reviews/B000U6XE7U

 

[jdawson2402]

Thanks for these ideas stavvy. The main problem I see with those wireless adapters is that they seem to need power at the point of each speaker itself. We'd have the same problem running power cable up in the ceiling as we do running speaker cable!

But I take it from your reply that we really can't run a 5-channel system if we only have 3 x 2 core cables wired in? And a 3-channel system (but still with 4 speakers in the ceiling) really isn't adequate for TV audio. Is that correct in your experience?

 

[stavvy]

hmm i never thought about the power. I know you say its impossible to run more cable as everything is plastered in but i take it you have access to teh cable that is in obviously? i.e. at the receiver end and at your left/right speakers? can you not use this wire to pull through another set of wires? sorry i know you have said its impossible but its difficult to picture the setup exactly without seeing it.

yes, as far as I can see you wont be able to have discrete 5.1 i.e. seperate audio feeds for each channel. Worst case scenario though a 3.1 system can still sound good and the stereo effect in movies still adds a lot (if not the bulk of the sound experience).

 

[MajorFubar]

One way or another, a two-core cable has to go to each speaker for its + and - terminals, so with six speakers that's up to six runs of cable, or if you have an active sub, five runs of speaker cable and a phono-to-phono to the subwoofer.

 

[jdawson2402]

OK, that's good to know that we could still have a 2-channel stereo system which would sound OK. I thought we'd maybe have to give up on wiring the TV into the ceiling at all, because it would sound weird (and perhaps just opt for music playing through the ceiling speakers). But presumably if we add a centre speaker beneath the TV (so not all the sound is in the ceiling), we then just run all speakers in stereo? Or would we set up the ceiling speakers as "front" and have no "rear"? Effectively a 3.0 / 3.1 (with sub-woofer) system...

I spoke to the electrician about using the existing cables as "draw wires". But unfortunately that's not possible either - he drilled holes through the lateral ceiling joists and also looped, so there's no way to tug the wires through. We'd have to remove the plaster to get to them.

 

[jdawson2402]

Thanks Major Fubar - that clearly answers my question! So it's either more cabling or no 5-channel...

 

[stavvy]

ah, thats a ******. no, you should still be able to run 3.1 setting your front ceiling speakers as fronts and your centre channel as centre obviously. I dont know if your receiver is able to detect such a thing as a 3.1 setup or if it will just decode as 5.1 and try to send a signal to speakers that are not there.

if you can stand it, there is cable conduit that comes in a variety of decorative finishes that you can run along skirting board and perhaps up the corner of the room to you ceiling speakers. Not the tidiest of solutions of any means but if you use very thin speaker cable you could get away with as an unobtrusive conduit as you can.

http://images.cableorganizer.com/articles/speaker-wire/corner-duct.jpg

not the best ever, but if you're set on full 5.1 but cannot get access to the ceiling. to limit the conduit required you can also get flat speaker cable that you can run under the carpet (if the room is carpeted) to the rear of the room then run it up the corner of the wall

 

[stavvy]

p.s. receivers can "mix" stereo sources (a soundtrack that only has left and right sound) to create a surround effect that can sometimes be quite effective. but you still need your rear speakers to be connected up somehow...

 

[Tonestar1]

Hi,

If putting three speakers at the front is out of the question due to space/aesthetics but you are ok with a centre then why not try a soundbar type solution for your front three speakers all from one box? You could still use your in ceiling speakers as rear surrounds. Not as many of them on the market as most soundbars are for full 5 channel but it's still possible to find good quality bits of kit out there. Something like this would do the trick

http://www.quad-hifi.co.uk/Series.aspx?lang=En&Tab=L-ite%20Plus%20LCR%20Sound%20Bar

or

http://www.daytonaudio.com/index.php/bs36-36-lcr-speaker-bar-black.html

or

http://www.ebay.co.uk/itm/like/151367708257?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108

 

[jdawson2402]

And just adding to this (and thanks for the further posts everyone), is it even possible and effective to run the same 2-core cable from the AV receiver to one speaker and then on again from that speaker to the next speaker (e.g. 1 cable for 2 speakers in the "left channel")? I understand that we might have to sacrifice 2 front ceiling speakers, leaving the other 2 as "rear" and then putting the "front" speakers somewhere else (e.g. on the wall / use a soundbar). But I'd like to know if our electrician was ever correct to think that it's possible to run two separate speakers off a single length of 2-core cable - perhaps this works for stereo music playing only? If it never works (or at least is never how speakers are supposed to be wired) then he has made a mistake because he knew we had 4 speakers. And in that case, we may be able to get him to put in the correct cable (even if re-plastering is required) before it's too late. We haven't started painting yet!

 

[stavvy]

no you cant run two speakers from the one wire. even if you could wire the speakers in series you could damage your amp!

 

[stavvy]

tbf though you are right, the electrician should have known better than run a single wire (and if he didnt he should have double checked!)

 

[jdawson2402]

OK, thanks stavvy. I'll have to use that to argue that they need to open up the ceiling again!

On top of that, I'm not convinced that he's bought the legally required 2-core for in-wall / in-ceiling wiring. I now know that it has to be low smoke / zero halogen. He claims that he bought good mid-range wire and that it's fine with fire regs, but it doesn't look sufficient to me (from looking at the casing). Do you know how I might check that for certain? If they haven't put the correct wire in for building control, I have a stronger case to get them to try again!...

 

[stavvy]

im afraid its never something ive had to consider, im sure though you should be able to search for the relevent markings and then see if they are on the jacket of the cable or not. my first argument would always be though that he never done the job you tasked him to do!

 

[RobinKidderminster]

Only two wires shows total lack of knowledge and I would insist he puts it right. He may chase the wire into the board which with a good plasterer should be ok. Check wire regs on Internet. Hopefully he knows more aboit mains if he has done any - and has the proper legal qualifications & training

 

[abacus]

Yes it’s possible to connect 2 speakers to 1 channel; you just have to make sure that the combined impedance can be handled by the receiver.

Connecting the speakers in parallel will half the impedance seen by the receiver and connecting in series will double the impedance seen by the receiver.

Parallel 2x8 ohm speakers = 4 ohms, 2 x 4 ohm speakers = 2 ohms

Series 2 x 8 ohms =16 ohms, 2 x 4 ohms = 8 ohms

Most receivers will handle 4 ohms and above but will probably have problems with 2 ohms. (If in doubt connect in series as there are very few speakers that have a nominal impedance of less than 4 ohms)

Very few cables do not meet the appropriate British Standard so they are probably fine. (The BS standard is usually marked on the cable somewhere)

Hope this helps

Bill

 

[jdawson2402]

OK thanks Bill - that advice seems to differ from what others are saying but I understand the logic!

So, in summary you're saying:

1. We CAN use a single 2-core cable to connect 2 in-ceiling speakers on a left channel (and then a second 2-core cable for the right channel)? That's not only technically sound but a perfectly acceptable series setup.

2. In that scenario, we'd have a stereo speaker set-up so would not be able to support the idea of both "front" and "rear" speakers for surround sound.

3. Our speakers are each 8 ohm so in this scenario, we'd need our AV receiver to output 16 ohm per channel (that might be an issue with the amp we had in mind).

4. If the 2 core cable is British Standard it is also by nature safe for in-ceiling / in-wall wiring - i.e. it is low smoke / zero halogen.

Are all four of those statements correct?

 

[abacus]

Basically yes, its low impedance's that cause problems for receivers.The BS number on the cable can be checked against the British Standard website to double check.Hope this helpsBill

 

[jdawson2402]

OK, thanks again Bill. Perhaps it’s best for me to just describe the products we were planning to purchase. Because I’m now a little confused over whether it’s the AV receiver’s maximum or minimum output to / from the speakers that we need to be worried about.

In-ceiling speakers:[/b] 4 x Apart CMX20T: http://www.apart-audio.com/Category/Details5?cat2=APART&cat3=01.LOUDSPEAKERS&cat4=1000_BUILTIN&cat5=1010_CEILING&productcode=CMX20T. These are 16ohm impedance, but we can also get 8ohm versions.

AV receiver:[/b] Yamaha YXV477: http://www.richersounds.com/product/av-receivers/yamaha/rxv477/yama-rxv477-blk. This is supposed to support a 5.1 system. It’s spec states “Maximum power output per channel - RMS into 8 ohms” and then “80 x 5 (6 ohms)”.

So if we wire the 4 ceiling speakers using 2 series circuits (and add a fifth “central” speaker) would that Yamaha amp be able to cope? As you say 16ohms in series = 32ohms for a single channel. And 8 ohms in series still = 16ohms. These are both greater than the “maximum power output per channel” stated above.

Incidentally, even if you confirm that the AV-receiver and series speaker wiring can all work together, it’s still true that we can’t support a 5-channel surround sound with this setup, isn’t it? That’s what we wanted our electrician to wire!

 

[jdawson2402]

Thanks Tonestar. We're trying to integrate everything into the ceiling / walls as much as we can. That was the whole point whilst we had the beams and joists exposed (it’s a loft conversion). The TV itself will sit in a recess in the wall. We’re also trying to hide the AV receiver and things like Sky TV box around the corner from the TV in a concealed corner of the room, and then run cables from the AV receiver to the TV within the wall as well. So everything tucked away.

We could potentially have a small central speaker that protrudes from the wall beneath the TV, but we may opt for another in-wall speaker there as well. And the problem with those sound bars is that a) they're quite large and wouldn’t be set into the wall with everything else, b) we then have 2 redundant ceiling speakers (I think). So we’d prefer to sort it via the cabling but it looks like we’re never going to get what we need based on what has currently been wired in! (see my latest post to abacus)

 

[Xanderzdad]

To be honest I would dig a channel through the plaster that is big enough for all the cables to give you the extra channels you want. If you place the cables in a conduit and DON'T loop or clip them, then you can always add more later by pulling them through.

Replastering over this channel is a simple job for any competent plasterer - I've even managed a few metres myself with polyfilla and readymix plaster. Once sanded and painted you cannot see the channel.

If you stick with the current cables you are going to miss out massively on the full sound effect of 5.1 - don't underestimate the impact this has on TV / film enjoyment.