Pub. Address volume & wiring?

[DaveC]

I think I understand the purpose of PA wiring: increase impedance and voltage
over the speaker runs to minimize the loss percentages. I'm unsure, however,
how to adjust relative volume at each speaker due to difference distances
from the amplifier.

I have seen that PA audio transformers have several secondary winding taps.
This is to match the impedance of the speaker, correct?

How do you adjust for relative volume for each speaker?

Also, since voltage is high (~100v, I seem to remember...), does PA require
code-compliant wiring? What type is this?

Thanks,
--
DaveC
me@privacy.net
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[Michael A. Terrell]

DaveC wrote:

I think I understand the purpose of PA wiring: increase impedance and voltage
over the speaker runs to minimize the loss percentages. I'm unsure, however,
how to adjust relative volume at each speaker due to difference distances
from the amplifier.

I have seen that PA audio transformers have several secondary winding taps.
This is to match the impedance of the speaker, correct?

How do you adjust for relative volume for each speaker?

Also, since voltage is high (~100v, I seem to remember...), does PA require
code-compliant wiring? What type is this?

Thanks,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group

The taps are on the primary. you select the tap to give the required
level at each speaker. the total should be close to the amplifier's
rated output power, in watts. The wiring requirements depend on the
voltage, and your local codes.
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Central Florida

 

[Richard Crowley]

"DaveC" wrote ...

I think I understand the purpose of PA wiring: increase
impedance and voltage over the speaker runs to minimize
the loss percentages.

Assume you are talking about "70-volt" (or similar)
wiring systems also known as "constant voltage".

*NOT ALL* "PA wiring" is of this "constant voltage" variety.
If you don't use the accepted terms, you will get faulty responses.

I'm unsure, however, how to adjust relative volume at
each speaker due to difference distances from the amplifier.

Or differences in: room size, noise, desired levels, speaker
efficiency, etc. etc. etc.

I have seen that PA audio transformers have several secondary
winding taps. This is to match the impedance of the speaker,
correct?

If they are "constant voltage" transformers, they will typically
have serveral PRIMARY taps to adjust how much power/volume
you feed to that particular speaker. If you are using "70v"
transformers on a 70v line, the taps are typically labeled directly
in "watts" (how convienent!)

SOME constant voltage transformers ALSO have SECONDARY
TAPS. But most of them that I have ever seen are "hard-wired"
for 8 ohms output/secondary. Typically labled "4 ohm", "8 ohm",
"16 ohm" etc.

How do you adjust for relative volume for each speaker?

With the PRIMARY taps.

Also, since voltage is high (~100v, I seem to remember...),
does PA require code-compliant wiring? What type is this?

Depends on your local jurisdiction. I believe the National
Electrical Code (widely used across the USA) allows 70v
to use "class 2" wiring. 100v may have to use the same
wiring as power circuits.

 

[DaveC]

On Wed, 14 Jan 2004 20:28:05 -0800, Richard Crowley wrote
(in article <100c5mr9gg4cl4a@corp.supernews.com&gt:

"DaveC" wrote ...

I think I understand the purpose of PA wiring: increase
impedance and voltage over the speaker runs to minimize
the loss percentages.

Assume you are talking about "70-volt" (or similar)
wiring systems also known as "constant voltage".

*NOT ALL* "PA wiring" is of this "constant voltage" variety.
If you don't use the accepted terms, you will get faulty responses.

Indeed, I've refreshed my memory and it says "70 volt" on the amp's output
terminals.

Also, since voltage is high (~100v, I seem to remember...),
does PA require code-compliant wiring? What type is this?

Depends on your local jurisdiction. I believe the National
Electrical Code (widely used across the USA) allows 70v
to use "class 2" wiring. 100v may have to use the same
wiring as power circuits.

I'll ask the local building inspectors about 70 volt audio wiring.

Thanks,
--
DaveC
me@privacy.net
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[DaveC]

If I have an amplifier that doesn't have 70-volt output, can I use a
constant-voltage transformer in reverse, putting the 8-ohm winding to the
amp? Then I could connect the 70-volt winding to the wires to carry the
current to the speaker where there would be a traditionally-connected c.v.
transformer.

Accepting the absolute of loss in the transformers, this should work OK,
shouldn't it?

Thanks,
--
DaveC
me@privacy.net
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Please reply in the news group

 

[Michael A. Terrell]

DaveC wrote:

If I have an amplifier that doesn't have 70-volt output, can I use a
constant-voltage transformer in reverse, putting the 8-ohm winding to the
amp? Then I could connect the 70-volt winding to the wires to carry the
current to the speaker where there would be a traditionally-connected c.v.
transformer.

Accepting the absolute of loss in the transformers, this should work OK,
shouldn't it?

Thanks,

How do you think they get a 70 volt output in the first place? They
install the same transformer on the chassis to convert the low impedance
to 70 volts.
MCM carries three transformers for this:

555-6450 50 Watt
555-6452 100 Watt
555-6452 200 Watt

4 or 8 Ohm primary, and a single 70.7 volt secondary. All three are
on sale till Feb. 20, 2004 at:
http://www.mcminone.com/

--
We now return you to our normally scheduled programming.

Take a look at this little cutie! ;-)
http://home.earthlink.net/~mike.terrell/photos.html

Michael A. Terrell
Central Florida