"Arny Krueger"


The transformer is designed to present twice the nominal impedance of the
speakers to the amplifer, and uses boot/buck winding configurations to
minimize the actual power the transformer needs to handle.


** Purest gobbledegook.




...... Phil

"MK"

This will do it.
http://cpc.farnell.com/_/bt936/louds...all/dp/AV01580

It's a transformer-based design (presumably a variable auto-transformer,
like a Variac). A bit more expensive than a couple of 5-10 watt
resistors, but the extra flexibility is worth-while.

There is something odd about that part - a pair of audio transformers
rated 60W with 20Hz to 20kHz response in package 140mm x 85mm x 45mm - and
variable as well - and for £20. Don't expect it to sound very good.


** Expect it to blow your amplifier.

Here is a nice pic of the insides:

http://www.avstorm.co.uk/Switch_boxe...36_17 63.html

Consists only of a multi-position switch and 2 tiny auto-transformers.




...... Phil

Serge Auckland wrote:

"Chris J Dixon" wrote

My amplifier has two outputs. One is switched, and used for the
speakers in the living room. The other is taken via a separate
switch box to speakers in the dining room and kitchen.

Originally, the relative sound levels in all three rooms were
reasonably matched. However, during a kitchen refit, I had to
get rid of the conventional speakers, and fitted a pair of small
KEF in-ceiling units. These have a rather lower output level. If
I deselect the dining room pair, the kitchen is well enough
matched to the living room.

As a least cost work-around, it strikes me that I might be able
to improve the situation by inserting series resistors in the
feed to the dining room. Would this work? Living in a semi, I
don't run at particularly high sound levels.

If the dining room application is for background music during meals, then it
should work fine by attenuating the 'speakers relative to the others. Unless
you know how many dBs you need to attenuate, and can then calculate the
series resistance value,

It is hard to say exactly, my ear isn't calibrated ;-)

I reckon that if I picked a figure out of thin air, then bought
two resistors for each speaker totaling that figure, ( say 1R &
2R2) by experimenting with using them singly or series/ parallel,
I would get quite a range.

If I wanted, for example, 3 dB attenuation, what resistor would
you calculate?

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

In article , Chris J Dixon
wrote:
Serge Auckland wrote:



If the dining room application is for background music during meals,
then it should work fine by attenuating the 'speakers relative to the
others. Unless you know how many dBs you need to attenuate, and can
then calculate the series resistance value,

It is hard to say exactly, my ear isn't calibrated ;-)

I reckon that if I picked a figure out of thin air, then bought two
resistors for each speaker totaling that figure, ( say 1R & 2R2) by
experimenting with using them singly or series/ parallel, I would get
quite a range.

For an 8Ohm speaker using those in series would give 1dB and 2dB. Chances
are that you'd hardly notice the change in volume.

If I wanted, for example, 3 dB attenuation, what resistor would you
calculate?

The answer will vary with the spectrum of the music and the
impedance-frequency variations of your speakers. Unless your speakers have
the same impedance at all audio frequencies... which seems unusual.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Chris J Dixon" wrote in message
...
Serge Auckland wrote:

"Chris J Dixon" wrote

My amplifier has two outputs. One is switched, and used for the
speakers in the living room. The other is taken via a separate
switch box to speakers in the dining room and kitchen.

Originally, the relative sound levels in all three rooms were
reasonably matched. However, during a kitchen refit, I had to
get rid of the conventional speakers, and fitted a pair of small
KEF in-ceiling units. These have a rather lower output level. If
I deselect the dining room pair, the kitchen is well enough
matched to the living room.

As a least cost work-around, it strikes me that I might be able
to improve the situation by inserting series resistors in the
feed to the dining room. Would this work? Living in a semi, I
don't run at particularly high sound levels.

If the dining room application is for background music during meals, then
it
should work fine by attenuating the 'speakers relative to the others.
Unless
you know how many dBs you need to attenuate, and can then calculate the
series resistance value,

It is hard to say exactly, my ear isn't calibrated ;-)

I reckon that if I picked a figure out of thin air, then bought
two resistors for each speaker totaling that figure, ( say 1R &
2R2) by experimenting with using them singly or series/ parallel,
I would get quite a range.

If I wanted, for example, 3 dB attenuation, what resistor would
you calculate?

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

For a 3dB attenuation on an 8 ohm 'speaker you need a series resistance of
3.27 ohms. For 6 dB you need 8 ohms. But note that this assumes a nominal 8
ohm load, and loudspeakers are not pure 8 ohm loads. Also, by putting such a
series resistance in the loudspeaker lead you will change the frequency
response of the loudspeaker considerably. However, as this seems to be for
background music rather than critical listening, it will probably be
perfectly acceptable. I suggest you use 10 watt resistors. Alternatively
again, a 20 ohm 10 watt wire wound pot wired in series will allow you to
make adjustments.

S.

--
http://audiopages.googlepages.com

"Chris J Dixon" wrote in message
...
My amplifier has two outputs. One is switched, and used for the
speakers in the living room. The other is taken via a separate
switch box to speakers in the dining room and kitchen.

Originally, the relative sound levels in all three rooms were
reasonably matched. However, during a kitchen refit, I had to
get rid of the conventional speakers, and fitted a pair of small
KEF in-ceiling units. These have a rather lower output level. If
I deselect the dining room pair, the kitchen is well enough
matched to the living room.

As a least cost work-around, it strikes me that I might be able
to improve the situation by inserting series resistors in the
feed to the dining room. Would this work? Living in a semi, I
don't run at particularly high sound levels.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

Hi Chris,

have a look at the Wilmslow Audio site - they used to do a high-power L-pad
that might be useful for padding down one of the outputs.


Kind regards

Mike

fredbloggstwo wrote:

have a look at the Wilmslow Audio site - they used to do a high-power L-pad
that might be useful for padding down one of the outputs.

Thanks for that, all I needed was the right terminology.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

fredbloggstwo wrote:

"Chris J Dixon" wrote in message
.. .
My amplifier has two outputs. One is switched, and used for the
speakers in the living room. The other is taken via a separate
switch box to speakers in the dining room and kitchen.

Originally, the relative sound levels in all three rooms were
reasonably matched. However, during a kitchen refit, I had to
get rid of the conventional speakers, and fitted a pair of small
KEF in-ceiling units. These have a rather lower output level. If
I deselect the dining room pair, the kitchen is well enough
matched to the living room.

As a least cost work-around, it strikes me that I might be able
to improve the situation by inserting series resistors in the
feed to the dining room. Would this work? Living in a semi, I
don't run at particularly high sound levels.

have a look at the Wilmslow Audio site - they used to do a high-power L-pad
that might be useful for padding down one of the outputs.

I boxed up an L-pad
http://cpc.farnell.com/_/lp-200-8/speaker-l-pad-stereo/dp/LS00544?Ntt=LS00544
and installed it a while ago, but it doesn't really seem to have
sufficient adjustment.

I am now wondering about a completely different approach.

I could have totally separate control using something like

http://www.ebay.co.uk/itm/New-Mini-TA2020-Stereo-Audio-Amplifier-Power-Adapter-for-Car-MP3-iPod-Motor-/111246826219?pt=UK_AudioTVElectronics_HomeAudioHiF i_Amplifiers&hash=item19e6d3daeb

Fed from the phono socket tape output of my main amplifier.

I understand that quality may not be great, and I would always
have two volume controls to adjust, but these are tiny ceiling
speakers, so it will probably be fine.

Any better ideas?

Chris
--
Chris J Dixon Nottingham UK


Plant amazing Acers.

On 27/01/2014 16:41, Chris J Dixon wrote:
I boxed up an L-pad
http://cpc.farnell.com/_/lp-200-8/speaker-l-pad-stereo/dp/LS00544?Ntt=LS00544
and installed it a while ago, but it doesn't really seem to have
sufficient adjustment.

I find that odd, as if it's wired correctly, an L-pad should give an
adjustment range from 0- 100% of full power.

Another alternative would be to install a 100 volt speaker system with
independent volume controls in each room, but that would mean buying a
new amplifier,and some matching transformers and volume controls.
--
Tciao for Now!

John.

John Williamson wrote:

On 27/01/2014 16:41, Chris J Dixon wrote:
I boxed up an L-pad
http://cpc.farnell.com/_/lp-200-8/speaker-l-pad-stereo/dp/LS00544?Ntt=LS00544
and installed it a while ago, but it doesn't really seem to have
sufficient adjustment.

I find that odd, as if it's wired correctly, an L-pad should give an
adjustment range from 0- 100% of full power.

Well, AFAUK I have done it right, but I suppose that is a bit of
a circular argument. ;-)

Another alternative would be to install a 100 volt speaker system with
independent volume controls in each room, but that would mean buying a
new amplifier,and some matching transformers and volume controls.

So, significant expense, compare with my proposal which you
snipped. Just for the record, what would its advantages be?

Chris
--
Chris J Dixon Nottingham UK


Plant amazing Acers.