adding volume control to office speaker system

[chuck clark]

Hi,
I need to add separate volume controls to an existing 9 office speaker
system.
So as it stands, the 9 speakers have impedance-matching transformers on them
and they are wired in parallel to the 70v tap on the amp.

Figure 7-16 of the article below has a diagram of how it is setup (with
out the one volume control)
http://www.partsexpress.com/resources/70volt.html


A picture of the back of the amp and a speaker with a transformer is here
http://www.largeprojections.com/speakers/

So it works fine. I bought 9 of these controls with impedance-matching
control.
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=185-020
They are stereo, i know, but i got them very cheaply.


I went and added 4 volume controls in between the amp and
4 speakers. This sort of works for the 4 speakers. 3 of the volume
controls seem
to work as expected. They adjust the volume for the speaker they are
controlling.
The 4th speaker is much louder then them all and the volume control
adjusts the
volume for all 9 speakers including the ones the have volume controls.

I need to add 5 more controls but I am unsure if i am doing this correctly.

Should I bypass the transformer on each speaker now that I am using the
volume controls?

Any Advice is Greatly appreciated.

Chuck

 

[the Wiz]

Hi,
I need to add separate volume controls to an existing 9 office speaker
system.
So as it stands, the 9 speakers have impedance-matching transformers on them
and they are wired in parallel to the 70v tap on the amp.

If you are using "generic" speaker volume controls (not 70 volt line), then the
volume control goes between the transformer and speaker at each location.

If one control acts "oddly", then check the wiring of that control and check
that the transformer - speaker connections are like the others


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[burbeck]

On Fri, 30 Jul 2004 00:23:14 GMT, chuck clark

hi Chuck
its not clear on the spec that these controls are for 70V system
these are
http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=300-046&DID=7
regards
bob