RE: whole house audio

["Keith Doxey" <ukha@xxxxxxx>]

Hi Scott.

You can connect any number of speakers to an amp IF you wire them
correctly.

The problem you will have will be volume control. To use volume controls in
each room you will have to use matching transformers and that gets
expensive. Also a volume control can only turn things down. You have to
drive the amp at a fairly high level and then reduce the volume in each
room. This is inefficient generating lots of heat in the amp and volume
controls.

6 is an awkward number. 2,4 or 8 are much nicer numbers to work with. I
assume that all the speakers you will be using will be the same impedance
(normally 8 ohm). Placing 2 x 8 ohm speakers in parallel halves the
impedance giving effectively a 4 ohm load. Most amplifiers will handle this
quite happily. Putting 2 x 8 ohm in series will give 16 ohm. All solid
state
(transistor,mosfet,integrated circuit) amps will happily handle load of
higher imedance than their rating, or even no load at all. A Valve amp MUST
NOT be driven open circuit or with a mismatched load.

If your amp can handle a 4 ohm load and you have 6 x 8 ohm speakers you can
do the following

3 series connected pairs eg -----SPKR-----SPKR----  each will be 16 ohm,
connected in parallel. That is the same as 3 x 16 ohm speakers in parallel
and will drop to a third of the impedance eg 5.333 ohm

l-----SPKR-----SPKR----l
+ ---l-----SPKR-----SPKR----l---- -
l-----SPKR-----SPKR----l

Each speaker will get an equal amount of power eg with a 60W amp at full
power each speaker will get 10W. The two problems are that you have no
individual control and unless you have 6 rooms of exactly the same size,
some of the rooms will sound much louder than others.

You could run in mono (YUK) in which case you could feed 3 rooms from the
left channel and 3 from the right. In this case you could simply disconnect
the pair of speakers in a room to turn it off without any ill effects on
the
amp. You may get a slight change of volume in other rooms on that channel
though.

Another alternative is to scour the secondhand shops for cheap HiFi amps
(old ones that still work OK but dont have many inputs) and connect them to
the tape out of your main amp. that would give you individual volume
controls but obviously not in the actual rooms although you could set the
rooms to different levels.

DO NOT have speaker cables joined in inaccessable places. For the cost of
the extra cable (only a few quid) you can homerun them all to one point and
make any interconnections there. You WILL regret it if you skimp on cable
and wire them all together above the ceiling. Multiroom audio is becoming
more affordable and KAT5 will have that feature as well. The one thing all
Multiroom systems need is cable back to a central location.

Hope that helps

Keith



-----Original Message-----
From: Scott Crowther [mailto:scrowther@xxxxxxx]
Sent: 15 November 2001 11:57
To: 'ukha_d@xxxxxxx'
Subject: [ukha_d] whole house audio


Having only recently moved to a company working in the HA field,
I am now being unbelievably hooked (but unbelievably poor!), so I'm
thinking of making Whole House Audio my first project, with as little
outlay as possible.

I reiterate (those of you who know me), I am not very technically minded...

I'm happy to run a one-zone system off of my existing hi-fi amp (I
belive its powerful enough), and am happy to attempt cabling in my 1890's
terraced house.

I'm planning to set up speaker-end volume controls, rather than IR
(small house, easy to walk about), but am struggling with impedance
matching(?)

I'm sure I shouldn't connect 6 pairs of speakers straight into my amp,
so how do I avoid blowing my amp to pieces? I won't be daisychaining
my speakers, and my amp only has one output...

Cheers,

Scott.

PS - I'm learning fast by reading all your posts, BUT I struggle with
some of your jargon, although I do know what a grommet is     ;-)
Bear with me.


For more information: http://www.automatedhome.co.uk
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