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Author Topic: 70v system / "dance studio"  (Read 7716 times)

Tai Dirkse

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70v system / "dance studio"
« on: February 06, 2012, 02:58:34 pm »

Our contractor (for some reason) installed a 70v (w/e the actual voltage is here in Japan) system (What they call a "High Impedance System" here in Japan) for our Dance Studio  sound system...

I've never seen a 70v system used in this type of "Music System" - I've seen them paging systems for announcements, etc

Is there a problem with using a 70v system for music? I am worried that the speakers won't be able to fully produce the bass sounds needed in an dance studio...


The speaker is a TOA HS-1200BT which has variable impedance so I'm sure we can change to a Hi-Impedance system if we rewire everything...
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Charlie Zureki

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Re: 70v system / "dance studio"
« Reply #1 on: February 06, 2012, 03:48:51 pm »

Our contractor (for some reason) installed a 70v (w/e the actual voltage is here in Japan) system (What they call a "High Impedance System" here in Japan) for our Dance Studio  sound system...

I've never seen a 70v system used in this type of "Music System" - I've seen them paging systems for announcements, etc

Is there a problem with using a 70v system for music? I am worried that the speakers won't be able to fully produce the bass sounds needed in an dance studio...


The speaker is a TOA HS-1200BT which has variable impedance so I'm sure we can change to a Hi-Impedance system if we rewire everything...

  Taid..

  You must comply with the requirements of the Forum rules... Please, go back and include your FULL name.

  And...I thought the typical voltage used in Japan was 100 volts for distributed systems?

  Hammer
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Tai Dirkse

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Re: 70v system / "dance studio"
« Reply #2 on: February 06, 2012, 04:06:52 pm »

woops... sorry.
done.

Yes, i guess it would be 100v...
Either way, I've never seen it used in a single room to power four speakers...

Are there what are the advantages/disadvantage to such system?
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John Roberts {JR}

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Re: 70v system / "dance studio"
« Reply #3 on: February 06, 2012, 04:21:51 pm »

Our contractor (for some reason) installed a 70v (w/e the actual voltage is here in Japan) system (What they call a "High Impedance System" here in Japan) for our Dance Studio  sound system...

I've never seen a 70v system used in this type of "Music System" - I've seen them paging systems for announcements, etc

Is there a problem with using a 70v system for music? I am worried that the speakers won't be able to fully produce the bass sounds needed in an dance studio...


The speaker is a TOA HS-1200BT which has variable impedance so I'm sure we can change to a Hi-Impedance system if we rewire everything...
Constant voltage systems are used for background music all the time. You should be able to find specs on the speaker... they rate response to 70Hz, so not going to rattle the room with massive bass notes.

In general constant voltage systems (100V in Japan) are not very accommodating of high level low frequency content because of all the transformers in the path stepping up the signal to 100V and back down to low voltage for the speakers. Extending the response to lower frequency requires more iron and copper (in other words more Yen). To pass full audio power at 60Hz the output transformer needs to be roughly the same size as the power supply transformer. To pass that same power at 20 Hz the audio transformer needs to be 3x larger than the power transformer.. 

You can probably add a few low voltage subs to the system, HPF the constant voltage feed to make their life easier and get all the bass you want. It depends on how loud and low you need to go.

JR

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Hal Bissinger/COMSYSTEC

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Re: 70v system / "dance studio"
« Reply #4 on: February 06, 2012, 05:48:19 pm »

I think a constant voltage system is just fine- with the speakers you have which are background/foreground music speakers.
 
As said they only go down to 70hz, that is the spec for the cabinet so the internal transformer is going to be included in that spec. So it certainly should be large enough to handle 70 hz. 
 
You don't say what amp is being used, there are many transformerless "direct drive" 70.7 and 100v amps that will eliminate any loss from a transformer on the output of the amp.
 
Although you say that this is a dance studio it looks like your interpretation is different than somebody elses. You talk about technical concerns, I assume the system is operational. You say that you are worried that the speakers won't be able to fully produce the bass. Don't know why nobody has asked- what does it sound like?
 
-Hal
 
 
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Greg Ruddell

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Re: 70v system / "dance studio"
« Reply #5 on: June 12, 2012, 12:47:27 am »

70 volt often gets a bad rap. many reasons and advantages for a 70 volt distributed design, and not all 70 volt components are created equal. The traditional "commercial" application is one end of the spectrum, but over the years, the fidelity and frequency response depending on the transducers used has greatly improved.

Transformers play a huge part, and really decent transformers with low saturation cores are available. Output has always been an issue, but you can actually realize some decent output without the usual power compression if you have a high quality transformer. With that said, there is really no need to design a high impedance system with transformers and extra potential connection and failure points if long distances or an insane amount of transducers isn't required. So.. back to commercial applications. This is where 70 volt makes sense and really shines.

In this situation, you could rewire the facility (evaluate that cost), or you could do as John Roberts suggested and add some subs. I will add a twist to this...If you can easily get signal conductors to these subs, then add powered subs. You can find low cost 70/100 volt to line level passive transformers and then you can pull the signal from any of the speakers in the circuit. This should do it because the TOA's have very high quality transformers and also the speakers have inherently good overall sonics capable of delivering some decent fidelity @ high impedance (would a transformerless solution be a little better?  yes, but not a deal breaker in this situation).  Just make sure that you have at least 30% more headroom of amplifier power at all frequencies for the TOA's.  I'd think about using CROWN CTs series amplifiers. The subs will provide a lot of the psychoacoustic results and nobody will know the difference unless much higher sound pressure levels are required.
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Ryan C. Davis

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Re: 70v system / "dance studio"
« Reply #6 on: June 12, 2012, 12:58:05 am »

so, if the response is only good to 70 Hz, is that a function of the transformer in the amp or the speaker? Just wondering if you'd get enough LF information out of your 70v to line level converter to feed the subs.
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Greg Ruddell

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Re: 70v system / "dance studio"
« Reply #7 on: June 12, 2012, 02:57:14 am »

so, if the response is only good to 70 Hz, is that a function of the transformer in the amp or the speaker? Just wondering if you'd get enough LF information out of your 70v to line level converter to feed the subs.

Depends on the amplifier. Mostly, the frequency response is compromised at the transducer in a  high impedance system. But don't expect to use above average transducers and mediocre amplifiers. Typical 70 volt amps such as  run of the mill Bogen...Toa, or Inter M ...Univeristy Sound....the list goes on..are designed for a specific application. They fulfill that very well. When they are asked to provide more than their intended use.....they ultimately fail.
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Brad Weber

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Re: 70v system / "dance studio"
« Reply #8 on: June 12, 2012, 04:52:00 am »

Depends on the amplifier. Mostly, the frequency response is compromised at the transducer in a  high impedance system. But don't expect to use above average transducers and mediocre amplifiers. Typical 70 volt amps such as  run of the mill Bogen...Toa, or Inter M ...Univeristy Sound....the list goes on..are designed for a specific application. They fulfill that very well. When they are asked to provide more than their intended use.....they ultimately fail.
You could add a 70V transformer to virtually any amplifier or speaker, the frequency response in constant voltage systems is usually limited by the transformer rather than the transducers (speakers) or amplifiers.  Some amps can 'direct drive' a 70V or 100V system without an output transformer while a number of 'contractor' amplifiers are designed to drive 70V systems with virtually the same performance as for a low impedance load.
 
I think the problem is that people often associate constant voltage systems with PA and paging type applications and while they are certainly common in such applications and there are many products specifically oriented at such applications, there is also a number of manufacturers offering higher quality/performance speaker and transformer packages, although you usually pay a price for that quality and performance.
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Ryan C. Davis

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Re: 70v system / "dance studio"
« Reply #9 on: June 12, 2012, 11:55:34 am »

Depends on the amplifier. Mostly, the frequency response is compromised at the transducer in a  high impedance system. But don't expect to use above average transducers and mediocre amplifiers. Typical 70 volt amps such as  run of the mill Bogen...Toa, or Inter M ...Univeristy Sound....the list goes on..are designed for a specific application. They fulfill that very well. When they are asked to provide more than their intended use.....they ultimately fail.

I'm aware of the pitfalls of 70v systems, where I'm getting hung up is how (from other postings) there is virtually no low frequency information below xx Hz depending on what transformer is used. That being said, if you use a...

Quote from: Greg Ruddell
low cost 70/100 volt to line level passive transformers and then you can pull the signal from any of the speakers in the circuit.

to feed the subs, AND there is virtually no LF information present at that point, what good are the subs? It's like connecting a fire hose to an empty hydrant.
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Ryan Davis

ProSoundWeb Community

Re: 70v system / "dance studio"
« Reply #9 on: June 12, 2012, 11:55:34 am »


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