Hi.

I have a small wiring job to do here at my day job (cabinet shop), I
moonlight as a studio owner.
I've been put in charge of wiring a voice page only intercom setup using
a TOA P-912A amp, and 5 speakers (the farthest one being 150-200 feet
away). I have yet to purchase the speakers and speaker cable.

Any helprecommendations would be great. Can I just wire them in series
using the 70v output from the TOA (with presumably a transformer on each
speaker)?


Please guide me.........
Thanks

e.maynard wrote:
I have a small wiring job to do here at my day job (cabinet shop), I
moonlight as a studio owner.
I've been put in charge of wiring a voice page only intercom setup using
a TOA P-912A amp, and 5 speakers (the farthest one being 150-200 feet
away). I have yet to purchase the speakers and speaker cable.

Any helprecommendations would be great. Can I just wire them in series
using the 70v output from the TOA (with presumably a transformer on each
speaker)?

You wire them in _parallel_ from the 70V output of the TOA, and you buy
speakers with integral transformers.

All you need to do is make sure the total power in watts of the amplifier
output is greater than the sum of the input power listed on each speaker
transformer tap.

You will probably want it to be louder in some places than others. In
a lot of places you can probably use the Speco or Atlas wall-mounted
8" full range speakers which have built-in transformers and are very
cheap. In others you may need high output paging horns so people can
hear over the high ambient noise level.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
e.maynard wrote:

I have a small wiring job to do here at my day job (cabinet shop), I
moonlight as a studio owner.
I've been put in charge of wiring a voice page only intercom setup using
a TOA P-912A amp, and 5 speakers (the farthest one being 150-200 feet
away). I have yet to purchase the speakers and speaker cable.

Any helprecommendations would be great. Can I just wire them in series
using the 70v output from the TOA (with presumably a transformer on each
speaker)?


You wire them in _parallel_ from the 70V output of the TOA, and you buy
speakers with integral transformers.

All you need to do is make sure the total power in watts of the amplifier
output is greater than the sum of the input power listed on each speaker
transformer tap.

You will probably want it to be louder in some places than others. In
a lot of places you can probably use the Speco or Atlas wall-mounted
8" full range speakers which have built-in transformers and are very
cheap. In others you may need high output paging horns so people can
hear over the high ambient noise level.
--scott


Thanks.................

The amplifier is rated at 120 watts at 4 ohms, 60 at 8 ohms, so if I'm
wiring up (5) 8 ohm paging horns (let's say rated at 25 watts each) in
parallel, I should be O.K.?

The amplifier states that the 70 volt output is 41 ohm.

Is 16/2 sheilded wire a good choice or is the sheilding a moot point?



I know this must be more straight forward than I'm making it......sorry
for the dumb questions.

Sheilding is not needed for speaker wire. Cheap single pair 16 or 20
AWG is fine (West Penn etc.) Power is based in the transfomer rating.
So if you have 5 x 20 Watt transformers that's a total of 100 Watts and
a good match for a 120 Watt amp.

Sheilding is not needed for speaker wire. Cheap single pair 16 or 20
AWG is fine (West Penn etc.) Power is based in the transfomer rating.
So if you have 5 x 20 Watt transformers that's a total of 100 Watts and
a good match for a 120 Watt amp.

e.maynard wrote:

The amplifier is rated at 120 watts at 4 ohms, 60 at 8 ohms, so if I'm
wiring up (5) 8 ohm paging horns (let's say rated at 25 watts each) in
parallel, I should be O.K.?

No.

No.

The amplifier states that the 70 volt output is 41 ohm.

How many watts is the 70V output rated? Ignore the impedance.

(A 70V output that is rated for 41 ohms should be rated for a source of
119 watts, by Ohm's law).

The speakers will have taps on the transformer, marked in watts.
They are not 8-ohm speakers, they are 70V speakers with so many
watts input.

With 70V, you don't think about matching impedances, you never think
about loads. All you think about are watts. The power ratings on
the transformers and amps are actually well-disguised impedance ratings.

Is 16/2 sheilded wire a good choice or is the sheilding a moot point?

Shielding is moot. If you're only running 120 watts through the whole
thing, 16 ga. is serious overkill too.

I know this must be more straight forward than I'm making it......sorry
for the dumb questions.

Get the Yamaha Sound Reinforcement Handbook. The system is intended to
be used by idiots... you have the 120W output of the amp, you hang as
many 70V speakers off as you want as long as the speaker inputs don't
exceed 120W. The problem is that if you actually want to know how it
works and think about it, it gets more complicated.

Because the "power" ratings are actually 4900 divided by the impedance
of the device (where 4900 is 70**2). If you have a constant 70V level
on the system with a pure tone, and you have an amplifier rated for 120W,
you will have 120W output to get to 70V. And each speaker will be
taking in as many watts as the tap on the back indicates. But you don't
really need to know any of this stuff. You just need to know that the
output power is higher than the sum of the input powers.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I have a small wiring job to do here at my day job (cabinet shop), I
moonlight as a studio owner.
I've been put in charge of wiring a voice page only intercom setup using
a TOA P-912A amp, and 5 speakers (the farthest one being 150-200 feet
away). I have yet to purchase the speakers and speaker cable.

Any helprecommendations would be great. Can I just wire them in series
using the 70v output from the TOA (with presumably a transformer on each
speaker)?

You should consider the fact that the cable resistance should be more than
enough to bring the 1.6R speaker array up to a safe 4R, so 70V transformers
aren't necessary. I believe Costco has efficient little Teac speakers with
wall-mount brackets for around $40/pr.

On Tue, 28 Jun 2005 15:46:29 GMT, "e.maynard"
wrote:

The amplifier is rated at 120 watts at 4 ohms, 60 at 8 ohms, so if I'm
wiring up (5) 8 ohm paging horns (let's say rated at 25 watts each) in
parallel, I should be O.K.?

As Scot said, you should tap the speakers so that the total power taps
of all the speakers is equal to or less that the amp's rated output.
We want to know the amps 70 volt power output, not the 8 ohm or 4 ohm
output. If the 70 Volt output is 125 W you could tap 5 speakers at 25
W. if it is less, you should tap them at a lower setting. the speaker
transformers usually have multiple taps on them. I suggest you get
ones that do. BTW, tapping at 25 W is a lot. Usually for indoor use
you tap at 1, 2, 5, maybe 10 W.

The amplifier states that the 70 volt output is 41 ohm.

I want to know how much power it puts out at 70 V.

Is 16/2 sheilded wire a good choice or is the sheilding a moot point?

Shielding is moot and 16/2 is more than adequate. You could even use
18/2.

I know this must be more straight forward than I'm making it......sorry
for the dumb questions.

Not dumb, it's a different way of thinking about speakers.

Julian

Julian wrote:
On Tue, 28 Jun 2005 15:46:29 GMT, "e.maynard"
wrote:


The amplifier is rated at 120 watts at 4 ohms, 60 at 8 ohms, so if I'm
wiring up (5) 8 ohm paging horns (let's say rated at 25 watts each) in
parallel, I should be O.K.?


As Scot said, you should tap the speakers so that the total power taps
of all the speakers is equal to or less that the amp's rated output.
We want to know the amps 70 volt power output, not the 8 ohm or 4 ohm
output. If the 70 Volt output is 125 W you could tap 5 speakers at 25
W. if it is less, you should tap them at a lower setting. the speaker
transformers usually have multiple taps on them. I suggest you get
ones that do. BTW, tapping at 25 W is a lot. Usually for indoor use
you tap at 1, 2, 5, maybe 10 W.


The amplifier states that the 70 volt output is 41 ohm.


I want to know how much power it puts out at 70 V.


Is 16/2 sheilded wire a good choice or is the sheilding a moot point?


Shielding is moot and 16/2 is more than adequate. You could even use
18/2.


I know this must be more straight forward than I'm making it......sorry
for the dumb questions.


Not dumb, it's a different way of thinking about speakers.

Julian








The TOA Manual is he
http://www.toaelectronics.com/disc/m.../P-906_12A.pdf

It doesn't state the Power output at the 70 volt
connection........................

Zigakly wrote:
I have a small wiring job to do here at my day job (cabinet shop), I
moonlight as a studio owner.
I've been put in charge of wiring a voice page only intercom setup using
a TOA P-912A amp, and 5 speakers (the farthest one being 150-200 feet
away). I have yet to purchase the speakers and speaker cable.

Any helprecommendations would be great. Can I just wire them in series
using the 70v output from the TOA (with presumably a transformer on each
speaker)?


You should consider the fact that the cable resistance should be more than
enough to bring the 1.6R speaker array up to a safe 4R, so 70V transformers
aren't necessary. I believe Costco has efficient little Teac speakers with
wall-mount brackets for around $40/pr.






"1.6R speaker array up to a safe 4R"

I have no idea what this means.

"1.6R speaker array up to a safe 4R"

I have no idea what this means.

I think the R's might be representing Ohms. I don't know if would go
this route expecting wire resisatnce to up the impedance to safe levels
for the amp. 70 Volt systems are perfect for th intended use.

In article .com,
wrote:
"1.6R speaker array up to a safe 4R"

I have no idea what this means.

I think the R's might be representing Ohms. I don't know if would go
this route expecting wire resisatnce to up the impedance to safe levels
for the amp. 70 Volt systems are perfect for th intended use.

It sounds like a real bad idea to me, and of course you cannot set the
levels individually at each speaker. Just go the 70V route. That's what
it's for, and 70V speakers aren't much more expensive.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article t writes:

The amplifier is rated at 120 watts at 4 ohms, 60 at 8 ohms, so if I'm
wiring up (5) 8 ohm paging horns (let's say rated at 25 watts each) in
parallel, I should be O.K.?

The amplifier states that the 70 volt output is 41 ohm.

Well, if you're really lazy or stoopid, you could wire them in series
and connect the string to the 70V output. 70 volts into 41 ohms is 120
watts, so the arithmetic comes out right. And you'd be putting less
than 25 watts into each speaker, so you wouldn't blow any of them up.

That's not the way you're supposed to do it, though. You should have a
20 or 25 watt transformer on each speaker and wire them in parallel.
The advantage of doing it this way is that if you want the speaker in
the machine shop to be louder than the one in the secretary's office,
you can put a 35 watt transformer (and 35 watt speaker, of course) in
the shop and put a 15 watt transformer on the speaker on the one in
the office.

Is 16/2 sheilded wire a good choice or is the sheilding a moot point?

No need for shielding. You're talking about a current of less than 2A
so 16 gage wire should do for a couple of hundred feet.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

70v line stuff...
I just found this after reading the thread. It's quite a good primer.

http://www.crownaudio.com/amp_htm/am...nt_voltage.htm

Rv!

"Scott Dorsey" wrote in message
...
In article .com,
wrote:
"1.6R speaker array up to a safe 4R"

I have no idea what this means.

I think the R's might be representing Ohms. I don't know if would go
this route expecting wire resisatnce to up the impedance to safe levels
for the amp. 70 Volt systems are perfect for th intended use.

It sounds like a real bad idea to me, and of course you cannot set the
levels individually at each speaker. Just go the 70V route. That's what
it's for, and 70V speakers aren't much more expensive.

The TOA P-912A isn't a zone amp, and doesn't have independent output
attenuators. If a multimeter reads a DC impedence of 3.5R (Ohms) or higher,
the AC impedence will be at least 4R and it'll be 100% safe and offer higher
output, and assuming the speakers don't have wildly variable impedance it'll
sound better too. Granted 70V arrays deal with cable resistance better, but
unless you're wiring up an airport it's just not worth it.

For voice it's really not going to matter much either way, but in clubs it's
better to run zones with 4-6 speakers off a solid power amp rather than a
****y 70V rig. The Peavey CS 800X4 (4 x 300W @ 4R) is a good unit for such
a job.

In article , Zigakly wrote:
Scott Dorsey writes:

It sounds like a real bad idea to me, and of course you cannot set the
levels individually at each speaker. Just go the 70V route. That's what
it's for, and 70V speakers aren't much more expensive.

The TOA P-912A isn't a zone amp, and doesn't have independent output
attenuators. If a multimeter reads a DC impedence of 3.5R (Ohms) or higher,
the AC impedence will be at least 4R and it'll be 100% safe and offer higher
output, and assuming the speakers don't have wildly variable impedance it'll
sound better too. Granted 70V arrays deal with cable resistance better, but
unless you're wiring up an airport it's just not worth it.

No, but the 70V transformers have multiple taps. You need a high level in
one room, you set the speaker transformer on a high tap. You need a lower
level in another room, you set it on a lower tap.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

wrote:
Sheilding is not needed for speaker wire. Cheap single pair 16 or 20
AWG is fine (West Penn etc.) Power is based in the transfomer rating.
So if you have 5 x 20 Watt transformers that's a total of 100 Watts and
a good match for a 120 Watt amp.

Yes, it's advisable to allow 10-20% spare capacity (a) because speaker
impedances aren't constant (b) for expansion.

Office speakers will probably only need 2-3W each.

Parallel 70W wiring is the way to go. I don't understand Americans'
tendendy to use series-parallel arrangements of low impedance
speakers.

Owain
in the UK

wrote:

Parallel 70W wiring is the way to go. I don't understand Americans'
tendendy to use series-parallel arrangements of low impedance
speakers.

I have never seen any of the series-parallel stuff in any commercial
install. It seems mostly to be used in cheap installed systems in homes
for the most part, usually with switch boxes that have all kinds of
fancy built-in attenuation for matching.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
In article , Zigakly
wrote:
Scott Dorsey writes:

It sounds like a real bad idea to me, and of course you cannot set the
levels individually at each speaker. Just go the 70V route. That's
what
it's for, and 70V speakers aren't much more expensive.

The TOA P-912A isn't a zone amp, and doesn't have independent output
attenuators. If a multimeter reads a DC impedence of 3.5R (Ohms) or
higher,
the AC impedence will be at least 4R and it'll be 100% safe and offer
higher
output, and assuming the speakers don't have wildly variable impedance
it'll
sound better too. Granted 70V arrays deal with cable resistance better,
but
unless you're wiring up an airport it's just not worth it.

No, but the 70V transformers have multiple taps. You need a high level in
one room, you set the speaker transformer on a high tap. You need a lower
level in another room, you set it on a lower tap.

This is true... a speaker attenuator would work for my config, but that gets
messy.

On 6/29/05 3:46 PM, in article
,
" wrote:

wrote:
Sheilding is not needed for speaker wire. Cheap single pair 16 or 20
AWG is fine (West Penn etc.) Power is based in the transfomer rating.
So if you have 5 x 20 Watt transformers that's a total of 100 Watts and
a good match for a 120 Watt amp.

Yes, it's advisable to allow 10-20% spare capacity (a) because speaker
impedances aren't constant (b) for expansion.

Well... sorta, more because most folks don't know to include the transformer
loss AND it's often not clear whether the transformer manufacture is rating
the LINE DRAW or the POWER DELIVERED TO THE SPEAKER.


Parallel 70W wiring is the way to go. I don't understand Americans'
tendendy to use series-parallel arrangements of low impedance
speakers.

Mainly the almost IMPOSSIBILITY of finding (or unwillingness to afford)
proper transformers that don't look like a reactive short below 200Hz.

SSJVCmag wrote:
On 6/29/05 3:46 PM, in article
. com,
" wrote:

wrote:
Sheilding is not needed for speaker wire. Cheap single pair 16 or 20
AWG is fine (West Penn etc.) Power is based in the transfomer rating.
So if you have 5 x 20 Watt transformers that's a total of 100 Watts and
a good match for a 120 Watt amp.

Yes, it's advisable to allow 10-20% spare capacity (a) because speaker
impedances aren't constant (b) for expansion.

Well... sorta, more because most folks don't know to include the transformer
loss AND it's often not clear whether the transformer manufacture is rating
the LINE DRAW or the POWER DELIVERED TO THE SPEAKER.

They are supposed to be rating the line draw. If you put the rated load
on the secondary, and you put 70V at 1 KHz on the primary, it will draw
that current. Under any other condition, all bets are off.

Parallel 70W wiring is the way to go. I don't understand Americans'
tendendy to use series-parallel arrangements of low impedance
speakers.

Mainly the almost IMPOSSIBILITY of finding (or unwillingness to afford)
proper transformers that don't look like a reactive short below 200Hz.

There are plenty of them! They are expensive, sure, but they are out
there. Edcor makes some surprisingly decent ones that aren't very
expensive. Plitron makes some excellent ones that are very expensive.
But people in the installed home market aren't willing to spend a penny
if they can avoid it, I suppose.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 29 Jun 2005 15:52:38 -0400, (Scott Dorsey) wrote:

Parallel 70W wiring is the way to go. I don't understand Americans'
tendendy to use series-parallel arrangements of low impedance
speakers.

I have never seen any of the series-parallel stuff in any commercial
install. It seems mostly to be used in cheap installed systems in homes
for the most part, usually with switch boxes that have all kinds of
fancy built-in attenuation for matching.

I did a restaurant installation this way last year. Eight
identical high quality ceiling speakers, four series-parallel on
each channel of an ordinary stereo amp.

Works great in a situation where you have complete control of the
installation and guaranteed requirement of equal volumes everywhere.
Kind of a special case...

Chris Hornbeck
"Chief Assistant to the Assistant Chief" -F&S

On Wed, 29 Jun 2005 17:35:59 -0400, "Zigakly" wrote:


No, but the 70V transformers have multiple taps. You need a high level in
one room, you set the speaker transformer on a high tap. You need a lower
level in another room, you set it on a lower tap.

This is true... a speaker attenuator would work for my config, but that gets
messy.


An autotransformer volume control ( a transformer with a switch that
selects different taps ) allows you to adjust volume on a day to day
basis with a 70V system.

Julian

An L-pad type arrangement might work
OK with a few up to maybe 4 speakers.
With lines as long as is being discussed
wire gauge becomes important.
(no monster threads, please)
The 70V system is the proper way to do it
with long lines.

rd

On 29 Jun 2005 21:51:28 -0700, RD Jones wrote:
An L-pad type arrangement might work
OK with a few up to maybe 4 speakers.
With lines as long as is being discussed
wire gauge becomes important.
(no monster threads, please)
The 70V system is the proper way to do it
with long lines.

rd


It's worth your while to grab a copy of the NEC or the NEC Handbook, or
go to your local library and have the section on Class 2 wiring
photocopied.

Wiring isn't really "difficult" but it is Exacting.

If you're unsure about how to proceed, hire a professional.

Since the original post was about a paging system then the 70V is by
far the way to go.


I've been put in charge of wiring a voice page only intercom setup using
a TOA P-912A amp, and 5 speakers (the farthest one being 150-200 feet
away).