ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Installed Sound/Contracting => Topic started by: Richard Hedderly on December 30, 2020, 11:16:37 pm

Title: 70/100V speaker / amp questions...
Post by: Richard Hedderly on December 30, 2020, 11:16:37 pm
Hi,

I'm doing a tech refresh on our UK church audio setup. Going over from analogue mixer to digital / Dante.

Our existing passive speakers are fine and want to keep them. Each 300W 8Ω. The old analogue mixer /amp is a 300W per channel at 4Ω.

On new replacement amplifiers they are listed as 70/100V compatible, yet nowhere in the speakers' or the mixer's manuals is there any mention of 70/100V, just the ratings. Neither speaker has a tapping dial.

The speakers are Yamaha S112IV (very retro) and made in the USA. I suspect being made in the States, they are 70V.

Am I OK getting a new amp, setting it to 70V and feeding 300W 8Ω to the speakers?

Cheers

Richard
Title: Re: 70/100V speaker / amp questions...
Post by: John Roberts {JR} on December 31, 2020, 12:24:13 am
Hi,

I'm doing a tech refresh on our UK church audio setup. Going over from analogue mixer to digital / Dante.

Our existing passive speakers are fine and want to keep them. Each 300W 8Ω. The old analogue mixer /amp is a 300W per channel at 4Ω.

On new replacement amplifiers they are listed as 70/100V compatible, yet nowhere in the speakers' or the mixer's manuals is there any mention of 70/100V, just the ratings. Neither speaker has a tapping dial.

The speakers are Yamaha S112IV (very retro) and made in the USA. I suspect being made in the States, they are 70V.

Am I OK getting a new amp, setting it to 70V and feeding 300W 8Ω to the speakers?

Cheers

Richard
no...  a 70v line feeding 8 ohms would be a lot more than 300W, if it didn't release its smoke.   

you need to find better manuals...

JR

Title: Re: 70/100V speaker / amp questions...
Post by: Kevin Graf on December 31, 2020, 08:35:38 am
Let's see:
70 Volts and 8 Ohms is 600 Watts.
70 Volts and 300 Watts is 16 Ohms.

Are those the only two settings on the amp?

* * * * * * * * * *
Rod Elliott on Commercial 70 Volt systems:
https://sound-au.com/articles/line-amps.html

Rane Note on 70V Constant-Voltage Audio Distribution Systems:
https://www.ranecommercial.com/legacy/note136.html
Title: Re: 70/100V speaker / amp questions...
Post by: Richard Hedderly on December 31, 2020, 11:41:13 am
Let's see:
70 Volts and 8 Ohms is 600 Watts.
70 Volts and 300 Watts is 16 Ohms.

Are those the only two settings on the amp?

* * * * * * * * * *
Rod Elliott on Commercial 70 Volt systems:
https://sound-au.com/articles/line-amps.html

Rane Note on 70V Constant-Voltage Audio Distribution Systems:
https://www.ranecommercial.com/legacy/note136.html

---------------------------------------------------------------

Hey Kevin,

This is certainly a "trying to understand what they had / have got" scenario.

Some background.

The church is over a hundred years old and when I went under the floor near where there the speaker cable feed is, there was a label around the cable of 70V.

Now, the current sound system is circa mid 1990s. That's not to say they didn't have a old 70V distributed system before in the 60's until then and reused the speaker cables.

I'm new to the PA side of things. I wanted to make sure that there wasn't a hidden setting somewhere that needed to be enabled.

Given they only have one set of FOH speakers and a smaller stereo pair in a side room, I'd prefer to use this Behringer which has no mention of 70/100V setup.

https://www.thomann.de/gb/behringer_nx4_6000.htm

So if it's a case that there are non 70/100V systems and 70/100V systems, that's great.

It points to that they did reuse the old 70V speaker wire and that the 90s kit is in fact a non 70/100V system.

Would love your take on that.

Best wishes

Title: Re: 70/100V speaker / amp questions...
Post by: Erik Jerde on December 31, 2020, 12:04:07 pm
---------------------------------------------------------------

Hey Kevin,

This is certainly a "trying to understand what they had / have got" scenario.

Some background.

The church is over a hundred years old and when I went under the floor near where there the speaker cable feed is, there was a label around the cable of 70V.

Now, the current sound system is circa mid 1990s. That's not to say they didn't have a old 70V distributed system before in the 60's until then and reused the speaker cables.

I'm new to the PA side of things. I wanted to make sure that there wasn't a hidden setting somewhere that needed to be enabled.

Given they only have one set of FOH speakers and a smaller stereo pair in a side room, I'd prefer to use this Behringer which has no mention of 70/100V setup.

https://www.thomann.de/gb/behringer_nx4_6000.htm

So if it's a case that there are non 70/100V systems and 70/100V systems, that's great.

It points to that they did reuse the old 70V speaker wire and that the 90s kit is in fact a non 70/100V system.

Would love your take on that.

Best wishes

It would probably be helpful to know exactly what equipment is currently installed and (as beat you can determine) how it is hooked up.  The suspect 70v line may be appropriate for high voltage audio or it may not.  Knowing what the cable is will help with that.  For instance you can run 70v systems through a building on category cable and often be fine.  A high voltage system would have major problems doing that.
Title: Re: 70/100V speaker / amp questions...
Post by: John Roberts {JR} on December 31, 2020, 12:11:58 pm
---------------------------------------------------------------

Hey Kevin,

This is certainly a "trying to understand what they had / have got" scenario.

Some background.

The church is over a hundred years old and when I went under the floor near where there the speaker cable feed is, there was a label around the cable of 70V.

Now, the current sound system is circa mid 1990s. That's not to say they didn't have a old 70V distributed system before in the 60's until then and reused the speaker cables.

I'm new to the PA side of things. I wanted to make sure that there wasn't a hidden setting somewhere that needed to be enabled.

Given they only have one set of FOH speakers and a smaller stereo pair in a side room, I'd prefer to use this Behringer which has no mention of 70/100V setup.

https://www.thomann.de/gb/behringer_nx4_6000.htm

So if it's a case that there are non 70/100V systems and 70/100V systems, that's great.

It points to that they did reuse the old 70V speaker wire and that the 90s kit is in fact a non 70/100V system.

Would love your take on that.

Best wishes
It is still unclear what hand you are dealt.

The behriger nx4_6000 seems like a lot of power for a church instal.

70/100v "constant voltage" systems are confusing because they are neither constant voltage or always 70V. I won't attempt to deliver a full tutorial, there are several easy enough to find on the WWW. A few high points, these constant voltage systems are popular for industrial background music installs. They generally standardize on a relatively high voltage output and load that high voltage feed with higher impedance speaker loads, often using step down transformers. Any number of these modest power 70v speaker loads can be added in parallel as long as you don't exceed the total amplifier power output.

If you use your 4 channel high power amp, it is simple enough to drive 4 low impedance speakers individually. 

To answer your speculation about driving low impedance speakers through 70V speaker wiring, one intended benefit from 70V systems is lower current in the speaker wires meaning you can get away with cheaper, thinner gauge wire. Also 70V wiring would probably put all speakers in parallel unless designed to support different zone. You can use thinner wire to drive low impedance speakers, just don't tell your audiophile friends. They won't catch fire, and you seem to have power to burn...

Good luck.

JR
Title: Re: 70/100V speaker / amp questions...
Post by: Kevin Graf on December 31, 2020, 01:12:45 pm
Most modern pro amplifiers (300 Watts and larger) can drive most 70 Volt systems, without any modifications or special transformers.
Title: Re: 70/100V speaker / amp questions...
Post by: Lee Douglas on December 31, 2020, 02:44:28 pm
It would appear that unless somebody modified it with a transformer, the SM112IV and the rest of that line were 8 ohm speakers:

https://usa.yamaha.com/files/download/other_assets/4/320994/ClubIV_E.pdf
Title: Re: 70/100V speaker / amp questions...
Post by: Richard Hedderly on December 31, 2020, 08:51:42 pm
It would probably be helpful to know exactly what equipment is currently installed and (as beat you can determine) how it is hooked up.  The suspect 70v line may be appropriate for high voltage audio or it may not.  Knowing what the cable is will help with that.  For instance you can run 70v systems through a building on category cable and often be fine.  A high voltage system would have major problems doing that.

As it is hooked up, there are two FOH Yamaha S112IV-OAK speakers and their + - cables go down under the floor and come up next to the console desk into a speakON 4 pole panel socket. A speakON 4 pole plug into it then splits into two speakON 2 pole plugs that plug into the back of the Harmon Spirit Soundstation 600 analogue mixer / amp. [Manual picture attached]

There isn't a distributed speaker system installed around the church for announcements. I can't find any specific transformers for any 70/100V lines. It looks like all the power the FOH speakers need comes out the back of the mixer and that the label on a cable that says 70V is of a long gone legacy install.
Title: Re: 70/100V speaker / amp questions...
Post by: Richard Hedderly on December 31, 2020, 09:11:41 pm
It would appear that unless somebody modified it with a transformer, the SM112IV and the rest of that line were 8 ohm speakers:

https://usa.yamaha.com/files/download/other_assets/4/320994/ClubIV_E.pdf

Right, that's the manual I have and to double check, I got a ladder and it says it on the back of the speakers as well.
Title: Re: 70/100V speaker / amp questions...
Post by: Richard Hedderly on December 31, 2020, 09:58:26 pm
It is still unclear what hand you are dealt.

The behriger nx4_6000 seems like a lot of power for a church instal.

.
.
.
.
.

JR

The NX4_6000 is for covering over 4 channels 440W at 8Ω. The FOH speakers are 300W working up to 600W at 8Ω. We have two smaller 8Ω speakers in a side room.

I've seen recommended that an amp have twice the power as needed so you steer clear on distortion driving it.

That said, the FOH speakers in the church are mostly vocal, with some hymn music tracks playback. We're not feeding a band through it. 440W PC should be OK. Do you think I should get 600W PC?

Also the current amp is pushing 300W PC at 4Ω into 8Ω speakers.

https://www.thomann.de/gb/behringer_nx4_6000.htm
Title: Re: 70/100V speaker / amp questions...
Post by: Scott Holtzman on January 01, 2021, 03:41:35 am
The NX4_6000 is for covering over 4 channels 440W at 8Ω. The FOH speakers are 300W working up to 600W at 8Ω. We have two smaller 8Ω speakers in a side room.

I've seen recommended that an amp have twice the power as needed so you steer clear on distortion driving it.

That said, the FOH speakers in the church are mostly vocal, with some hymn music tracks playback. We're not feeding a band through it. 440W PC should be OK. Do you think I should get 600W PC?

Also the current amp is pushing 300W PC at 4Ω into 8Ω speakers.

https://www.thomann.de/gb/behringer_nx4_6000.htm (https://www.thomann.de/gb/behringer_nx4_6000.htm)


Lord have mercy please don't use the word push when describing the capability of an amplifier.  Watts is truly a useless specification out of context but in no context is there any difference between two equally speced amplifiers unless power is doubled.  Amplifiers supply or source power.  They do not push anything.


I just reread the thread and I did not see the impetus of the purchase?  If the current system is broken then you will be find, of you are hoping for any audible change that is unlikely. 
Title: Re: 70/100V speaker / amp questions...
Post by: Richard Hedderly on January 01, 2021, 08:42:37 pm

Lord have mercy please don't use the word push when describing the capability of an amplifier.  Watts is truly a useless specification out of context but in no context is there any difference between two equally speced amplifiers unless power is doubled.  Amplifiers supply or source power.  They do not push anything.


I just reread the thread and I did not see the impetus of the purchase?  If the current system is broken then you will be find, of you are hoping for any audible change that is unlikely.

Thank you for the clarification.

The impetus of purchase is that the analogue mixer amp keeps cutting out. It is getting on for 25 years old. This plus we want to be able to have the advantage of a digital mixer, means we will require a new amplifier. The reason why 70/100V systems were brought up was because a cable with a label saying 70V was found under the church near the mixing console's cables. As discussed, this now appears to be from an old distributed system that no longer exists.
Title: Re: 70/100V speaker / amp questions...
Post by: Frank Koenig on January 01, 2021, 10:23:52 pm
Lord have mercy please don't use the word push when describing the capability of an amplifier.  Watts is truly a useless specification out of context but in no context is there any difference between two equally speced amplifiers unless power is doubled.  Amplifiers supply or source power.  They do not push anything.

The loudspeaker is a weak, fickle, some might say floppy, creature that really doesn't know what it's about. Its (complex, very complex?) impedance varies all over the place and even is subject to things outside itself. The amplifier is the consummate, some might say brutal, voltage source, that forces its will upon the facile loudspeaker. This ultimate dominance is only attenuated by too thin speaker cables or crappy connectors. Alas, or maybe for the best, this relationship obeys conventional laws of physics and can be modeled accurately enough by assuming that the amplifier is a voltage source capable of a maximum voltage and maximum current (long-term thermal limits not withstanding). The loudspeaker can be assumed to be a resistor equal to its nominal impedance and any intervening transformers can assumed to be ideal, trading voltage for current in equal proportion perfectly. Forget about 70V, 100 V, whatever, and do the damn math. You'll be close enough.

Happy New Year. Hope we all get back to work and play soon.

--Frank