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#1
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70 Volt Wiring
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 |
#2
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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." |
#3
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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. |
#4
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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. |
#5
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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. |
#6
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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." |
#7
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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. |
#8
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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 |
#9
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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........................ |
#10
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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. |
#11
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"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. |
#12
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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." |
#13
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#14
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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! |
#15
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"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. |
#16
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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." |
#17
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#18
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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." |
#19
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"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. |
#21
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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." |
#22
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#23
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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 |
#24
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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 |
#25
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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. |
#26
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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). |
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