70 Volt Wiring

Archived from groups: rec.audio.pro (More info?)

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

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> e.maynard <heartwood-erik@mindspring.com> 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.

Archived from groups: rec.audio.pro (More info?)

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.

Archived from groups: rec.audio.pro (More info?)

> 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.

Archived from groups: rec.audio.pro (More info?)

Julian wrote:
> On Tue, 28 Jun 2005 15:46:29 GMT, "e.maynard"
> <heartwood-erik@mindspring.com> 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 here:
http://www.toaelectronics.com/disc [...] 06_12A.pdf

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

Archived from groups: rec.audio.pro (More info?)

>>"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.

Archived from groups: rec.audio.pro (More info?)

In article <phewe.447$aY6.413@newsread1.news.atl.earthlink.net> heartwood-erik@mindspring.com 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 (mrivers@d-and-d.com)
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 here: double-m-eleven-double-zero at yahoo

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news9s40n$m8h$1@panix2.panix.com...
> In article <1119981128.823034.293260@g47g2000cwa.googlegroups.com>,
> <tymish@hotmail.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
pissy 70V rig. The Peavey CS 800X4 (4 x 300W @ 4R) is a good unit for such
a job.

Archived from groups: rec.audio.pro (More info?)

tymish@hotmail.com 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

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news9uqc6$m24$1@panix2.panix.com...
> In article <GwBwe.1$0p.0@read1.cgocable.net>, Zigakly <zigakly@nope.no>
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.

Archived from groups: rec.audio.pro (More info?)

SSJVCmag <ten@nozirev.gamnocssj.com> wrote:
>On 6/29/05 3:46 PM, in article
>1120074410.126388.75150@g47g2000cwa.googlegroups.com,
>"spuorgelgoog@gowanhill.com" <spuorgelgoog@gowanhill.com> wrote:
>
>> tymish@hotmail.com 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."

Archived from groups: rec.audio.pro (More info?)

On Wed, 29 Jun 2005 17:35:59 -0400, "Zigakly" <zigakly@nope.no> 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

Archived from groups: rec.audio.pro (More info?)

On 29 Jun 2005 21:51:28 -0700, RD Jones <annonn@juno.com> 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.