RE: Whole house audio

["Brown, Andy [Infrastructure]" <andyb@xxxxxxx>]

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Spent the weekend cabling up my kitchen and study.  Each room now has two
cables each for stereo.

I then went to Comet and bought four smallish speakers, rated at 8 ohms,
max
75Watts.  My amp (a Kenwood) has Speaker A+B with a 100watt output.

I plumbed in the four new speakers into a Maplin speaker switch box taking
the output from the amp's speaker B sockets.

The amp's self protection kicks in when the volume reaches a certain point
(and not that loud either).  It's actually quite neat - it flashes
"PROTECT"
on the display!

This is where I start to get out of my depth.  I understand I'm getting
into
some "impedance matching" problems here (which I only found out
about after
doing all this cabling and buying the speakers!).

Can anyone offer any advice on how to get round this?  Replace speakers
with
16ohm versions? Solder on additional resisters?  Build something involving
a
transformer?

Help!

Cheers

Andy



At 16:06 01/09/00 +0100, you wrote:
>channel per room (left speaker upstairs, right speaker in kitchen - and
yes
>I know it's crap!).

I've got two rooms (3 if you count the wiring cupboard!) with one speaker
only, all fed from one central amp.  It was supposed to just be temporary,
but I'm now not convinced I need stereo in the kitchen or bathroom anyway
(in both rooms folk are moving around so many different places that stereo
imaging is fairly meaningless) so they'll probably stay mono...

>but can't really find a definitive guide to this.  Assuming I could get
CAT5
>(or whatever is best) wired cleanly around the house, what kit would I
need

At the moment, I've got everything just passively wired together at line
level, on Krone blocks.  One block is Left, one is Right, it's feeding a
variety of equipment, audio sources are Comfort and the TAPE OUT of a Denon
receiver, and it works remarkably well.  All the line level wiring is cat5
UTP.

If you try that for starters, it's not complex to add isolation
transformers at a later point if necessary.  If you're planning now, I
would highly recommend Krone stuff, it's made the installation and
subsequent repatching of cables very easy for me.  I've got one box with
audio, video and phone connections, and an adjacent one with alarm, control
and IR connections.  I'd originally planned to use phonos for patching a/v
and wire other cables directly to their controllers, I'm _very_ glad Keith
D pointed me towards Krone at the time!

It's probably worth having a cable dedicated to audio, with separate one
for video, control etc, but if you have to put video on the same cable it's
unlikely to be a disaster- you can never have too much spare cable
though!  I have audio and video on the same cable currently.

I've got a total of 7 rooms with audio connected (I think!), some are
currently "PC multimedia speakers" (ick!), some are just on a
line in to
existing stereos.  All currently come out of the wall on a 3.5mm minijack
(I had some anyway and yes, I'm surprised that joining the 0V's together
doesn't cause any problems too!), with the video on a phono (the video is
also passively commoned).  I had expected that it would be too noisy to
use, but the mains hum is barely audible and crosstalk between channels
isn't bad.

I've said here before, if someone's paying you to do it, best to aim to do
it 'right' from the start, but there's no harm in the 'suck-it-and-see'
approach for home stuff!

>?  At the moment I'm driving speakers directly from the speaker output,
but
>would it be better to drive a line-out to other amps in each room?

It'll be less prone to interference if the speaker cables are longer and
the line level cables are shorter, and all the amps are plugged in at the
same point on the ring main, but then you need some sort of control signal
from the room to the amps.  I'll stick to an amp in the wiring cupboard for
the kitchen and bathroom, and a stereo one for other rooms where I don't
want an amp 'on view' (dining room etc).

>Any definitive guides out there?

I think some of the guides from my retro-wiring page at http://ha.orrs.net
have particular reference to audio wiring, but you've probably read them
already!

>Which kit would you recommend?

For starters, lots of UTP, try it, and add what you find you need.  If you
can, try a couple of things connected together with the cable just dangling
around the house so you can get a feel for how good it should be before
installation under the floor, in the walls etc.

>quality.  This RF solution would be very easy to set up and assuming I
could
>buy additional speakers all tuned to the same frequency, I'd only need
one
>transmitter.

If you _really_ can't run cables, then you'll have to go RF, but they'll
need power anyway, so you might as well run a 2.5mm T&E cable from the
wiring cupboard for speaker connections as run a new mains cable.  And even
a long run of horrid bell wire from a cheap amplifier to cheap speakers
might sound better and will be less prone to interference from phones,
microwaves or whatever.  IMHO :-)

When Keith's magic boxes appear (sorry, had to mention them!), I might add
them as needed, but what was to be a temporary system until I had the
resources to add the appropriate electronics works really well as it is-
give it a try, and make sure you run your cables well clear of mains ones!

Nigel