Speakers

[pbelectrical]

Is it possible to connect four speakers in a series/parallel configuration to still give a total 4 ohms impedance. e.g./

I----4ohm------4ohm-----I
I I
I I
I----4ohm------4ohm-----I
I I
I I
+ve -ve

If this is possible can I then use a 2 channel relay to isolate one of the series pairs to then give one pair in series with an impedance of 8 ohm.

The reason for this is that my client would like to split one zone over his kitchen and outdoor deck with the option of isolating the deck speakers so as not to disturb the neighbours. Both areas would be best served by two speakers and not one. Regards, Peter Brown.

[Nobes]

Hi Pete,

Hope you had a good Christmas.

Is it Clipsal Multi Room Audio?

[RatDeSewer]

The amplifier will quite happily drive either 4 or 8 ohm loads (less power with 8). Just meet the requirement for minimum load and all should be good.

Cheers

RDS

[pbelectrical]

Thanks for the quick replies. Chris, it is the Multi Room Audio. RDS, I will be powering the amps to give me 25W and the client really only wants to use it as background music so I dont think the loss of power will be an issue.

This is my first MRA install so if anyone has any advice or tips I would appreciate them.

Install consists of three zones - Lounge - Kitchen/Deck - main bedroom. Matrix switcher with three inputs - MP3 from computer - radio - cd player. Three remote amps located in the top of built in robes.
10 speakers - 4 lounge - 4 kitchen/deck - 2 bedroom. The groups of 4 will be installed 2 in parallel to the right speaker ouput and 2 in parallel with the left speaker output. Using the clipsal 8 ohm speakers this should give me an impedance of 4 ohm per side. If this is incorrect or not possible please let me know before I get too far down the track. Thanks all.

Regards, Peter Brown.

[JohnC]

Your series arrangement is sensible and the maths is correct.

2 x 8 ohm in series = 4 ohms.

Put a centre-tap in there so you can isolate one speaker and you will end up with 1 x 8 ohm = 8 ohm.

Note that the isolation relay should be used to SHORT CIRCUIT the outdoor deck speakers. In other words, when you are running each channel in series like that, you don't "isolate" the ones that you don't want - rather you short circuit them so that they are replaced with a wire...



+ >----Kitchen----o----Outside----o
| |
| |
A VOLTAGE o |
FREE RELAY / |
ACROSS HERE o/ |
| |
| |
- <---------------o---------------o


When the relay contacts are open (off), the power flows through BOTH speakers.

When the relay contacts are closed (on), the power flows out of the first speaker and back to the negative.

[pbelectrical]

Your series arrangement is sensible and the maths is correct.

2 x 8 ohm in series = 4 ohms..

My math says;

2 x 8 ohm in series = 16 ohm

2 x 8 ohm in parallel = 4 ohm

2 x 8 ohm in series connected in parallel with another 2 x 8 ohm in series = 8 ohm.

Regards,

Peter Brown.

[Nobes]

John,

cant argue with his maths :D

Pete,

ignore right and left channel and look at it from one channel only. Clipsal speakers are 8 ohm.

Both speakers need to be in parrellel to obtain 4 ohms.

Put the second speaker on that channel through a relay channel to switch it.

When both speakers are active you will have 4 ohms (8ohm speakers) and when only one is active you will have 8 ohms.

See attached.

Then again it is Monday.....I could be completely wrong.

Chris.

[pbelectrical]

Chris,

Thanks that is exactly what I was talking about (couldn't get it to draw properly, kept getting left justified, I assume you created your diagram elswhere and then attached it to your post).

Only question now is if it safe to switch the second pair of speakers in and out while the system is in operation. I realise that it will effect the volume but will it be detrimental to the amplifier.

Peter Brown.

[Nobes]

Yep, just used the high Tech 'Paint' :D .

The problem in the above situation is that you have to have a relay in the field or run the speaker cabling back to the board.

Have you considered just adding another secondary amp to that zone. That way it will have:
The same input as the kitchen,
Independant Volume control
You can turn it on and off when you like
And you don't chew up relay channels.

Cheers,

[JohnC]

he he - and I thought I was so bluddy clever with that Notepad picture :cool:

2 x 8 ohm in series = 4 ohms <<< Yep, JohnC IS WRONG !

I always stuff up the terminology (not the concepts) - I have done so since I was about 10 when I first started with electronics and audio stuff.

HOWEVER :

In the first post pb said :
client would like to split one zone over his kitchen and outdoor deck with the option of isolating the deck speakers

Here is pbelectrical's first diagram (redrawn to show my interpretation of zoning arrangements)

I----4ohm------4ohm-----I << KITCHEN AREA
I I
I I
I----4ohm------4ohm-----I << DECK AREA
I I
I I
+ve -ve

This will present 8 ohms per "area", and present a 4 ohm load to the amplifier channel. Nothing wrong there.

But then pb went on to say something completely different :
10 speakers - 4 lounge - 4 kitchen/deck - 2 bedroom. The groups of 4 will be installed 2 in parallel to the right speaker ouput and 2 in parallel with the left speaker output. Using the clipsal 8 ohm speakers this should give me an impedance of 4 ohm per side.

So based on the info provided I could assume that there are 2 speakers (connected in parallel) on the right channel in the Kitchen, PLUS 2 more speakers (connected in parallel) on the right channel for the Deck. Also, that 8 ohm speakers were being used, and not 4 ohms. So this is considerably different to the wiring and impedence indicated in the first diagram.

If there are in fact only 2 speakers per channel, Chris Nobes' wiring diagram is correct in this application - a parallel connection would be preferable and present a 4 ohm load with both speakers connected. In that case you'd simply switch one speaker out (and present 8 ohms to the amp channel).

But pbelectrical implied that there are FOUR speakers per channel, and within each "area" the pairs would be wired in parallel, and the speakers are 8 ohms. If so, then the impedance within EACH AREA is 4 ohms per channel. Thus you cannot parallel the 2 areas together, since this would present a 2 ohm load to the amp - the only way that those can be connected to the amplifier is by wiring the 2 AREAS in series...

So if there are 4 speakers per channel, then my original diagram is still valid, however I have further clarified it as follows :

2 x 8 ohms 2 x 8 ohms
= 4 ohms = 4 ohms

+ >---- o KIT A o ----o----o DECK A o----o
| | | | | |
o KIT B o | o DECK B o |
| |
| |
A VOLTAGE o |
FREE RELAY / |
ACROSS HERE o/ |
| |
| |
- <-------------------o------------------o

My sincere apologies for the confusion, but I probably made it even worse with this post. Furthermore, after reading and re-reading I am now completely confused as to exactly how many speakers are on each channel... 2 or 4 ?

After almost an hour of editing I give up trying to understand what pb is actually doing, and trying to make myself clear... I simply throw it to the lions to attack and tear me to shreads...

Cheers, JohnC

[Frank Mc Alinden]

Hi Guys

How about using one of the devices ...........

http://www.hacs.com/ab8ss.html

HTH
Frank

[Nobes]

Now where did I leave those lions...............:D

Yep, you have got me John.

I think peter needs to clarify a bit further.

Chris.