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Author Topic: need help with a 70volt speaker install  (Read 4199 times)

Dennis Butterworth

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need help with a 70volt speaker install
« on: June 16, 2008, 10:36:55 pm »

Our apartment complex is installing 20 ceiling speakers in the club house and 2 surface mount speakers outside. I believe this means we will need to go with the speakers with transformers. However, I have no experience with these at all. Right now the only source equipment they have is a stereo receiver. Can someone suggest some options for this type of install? Also some guidence on the 70volt speakers would be appreciated.
Thanks again!
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Ivan Beaver

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Re: need help with a 70volt speaker install
« Reply #1 on: June 17, 2008, 02:00:41 am »

YOu will need a step up transformer on the otuputs of your amp.

Just add the wattages the loudspeakers are tapped at and make sure that the number does not exceed 90% of the rated power.

Be informed that the "ratings" on consumer gear are often VERY suspect, so you might want to only go to half of the rating for saftey sake.

Trying to do "stereo" in a ceiling speaker situation is pretty much a waste of time.

Go to Atlas sound and look up 70V systems for some good info.

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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Hal Bissinger/COMSYSTEC

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Re: need help with a 70volt speaker install
« Reply #2 on: June 17, 2008, 01:23:36 pm »

You might want to read through this- http://www.rane.com/note136.html

I also STRONGLY advise that you throw that consumer stereo receiver away and purchase the correct amplifier that will have the constant voltage output and multiple inputs that you need. You DON'T want stereo anyway.

-Hal

Don Boone

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Re: need help with a 70volt speaker install
« Reply #3 on: June 17, 2008, 03:18:28 pm »

Some consumer receivers can't tolerate a 70 volt transformer on it's outputs. Decades ago I remember a DIY install that used a JVC receiver from Circuit City driving a 70 line. The receivers would last about a month. After the third replacment Circuit City cried foul and the customer had to buy a proper TOA 70 volt amp.

Don
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Dennis Butterworth

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Re: need help with a 70volt speaker install
« Reply #4 on: June 17, 2008, 03:49:36 pm »

 Thanks! I checked out Atlas Sound and they had everything I needed. They also had a handy Excell spreadsheet that told me how many speakers I needed and at what watts to tap them
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Craig Hauber

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Re: need help with a 70volt speaker install
« Reply #5 on: June 20, 2008, 03:37:20 pm »

I've found some really good economy 70V gear for those consumer-ish type jobs on the Parts Express website.
They have some in-ceiling speakers with or without backboxes as well as plastic surface mount stuff that looks like what most people are used to for home installs ("Dayton" branded, as well as Atlas and other premium brands) -and prices listed.  

Excellent source for those 1-off jobs by people who normally don't do 70V for a living.


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Craig Hauber
CSA Productions Inc.
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Hal Bissinger/COMSYSTEC

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Re: need help with a 70volt speaker install
« Reply #6 on: June 20, 2008, 08:48:21 pm »

I've found some really good economy 70V gear...

Probably just about OK for PA and voice. God help you if you want to use it for music- unless of course you like a 200Hz- 10Khz response.

-Hal

Karl P(eterson)

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Re: need help with a 70volt speaker install
« Reply #7 on: June 20, 2008, 09:44:07 pm »

Hal Bissinger/COMSYSTEC wrote on Fri, 20 June 2008 20:48



Probably just about OK for PA and voice. God help you if you want to use it for music- unless of course you like a 200Hz- 10Khz response.

-Hal


That'll be the -10 down-points for you sir Smile

Karl P
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Craig Hauber

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Re: need help with a 70volt speaker install
« Reply #8 on: June 22, 2008, 01:49:07 am »

I tried a few for bathrooms and such and they had better bottom-end and a less pronounced HF than the EVIDS we use normally.

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber= 300-416

I ran them at 4 watt tap and they still had decent LF.  I will be trying them on some larger applications soon.  I found them to be a really good deal at only $35ea.  Came out of my own pocket, but client's ecstatic, landed 4 more contracts for new-builds.

YMMV




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Craig Hauber
CSA Productions Inc.
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Hal Bissinger/COMSYSTEC

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Re: need help with a 70volt speaker install
« Reply #9 on: June 23, 2008, 12:05:58 pm »

Might be worth a try. Looks like the went up in price though.

-Hal

Christian Tepfer

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Re: need help with a 70volt speaker install
« Reply #10 on: August 15, 2008, 06:58:10 am »

In order to achieve good sound (as good as it gets) use high quality transformers and cable.

Eric Madson

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Re: need help with a 70volt speaker install
« Reply #11 on: August 15, 2008, 10:16:34 am »

This can be achieved with a consumer piece, but as everybody else indicated, you should look at purchasing a pro 70V amp.

determine the rated output of your amp and find a relevant transformer at the following link.
http://www.eidusa.com/Electronics_Trans_Audio_117_119.htm

ex: 60watts/8 ohms= EID-119Y60

wire the amps output to the txfrms 8ohm-common taps. Wire the speaker output side to the 70v-common side. This will give you the correct voltage ratio for a 70v tap at each speaker. Each speaker requires a 70v/watt tap and the total wattage of all the speakers tapped cannot exceed 60 watts. The txfrmr is rated for 50-10k but I would try to High pass the audio so it sees nothing below 80hz. Transformers do not like low frequencies because they saturate and look like a short to the amp. Jensen also use to manufacture some good audio transformers but I cannot find any on the web.
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Eric Madson-CTS
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Hal Bissinger/COMSYSTEC

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Re: need help with a 70volt speaker install
« Reply #12 on: August 15, 2008, 11:44:40 am »

Looks like we are going around in circles. This was posted earlier by Don Boone:

Some consumer receivers can't tolerate a 70 volt transformer on it's outputs. Decades ago I remember a DIY install that used a JVC receiver from Circuit City driving a 70 line. The receivers would last about a month. After the third replacment Circuit City cried foul and the customer had to buy a proper TOA 70 volt amp.

-Hal

Eric Madson

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Re: need help with a 70volt speaker install
« Reply #13 on: August 15, 2008, 12:06:41 pm »

I believe Don is referring to "Directly" driving a 70V line. If you step the amplifiers rail voltage up to 70V you have a known voltage output making the tap settings relative.
If you have a "consumer" or "pro" piece that is only rated at 100w@8ohms then the max rail voltage is only about 28v. If you try to tap off multiple 70v speakers for a total of 100w you will load the amp down past its rating.
If you step the output voltage up to give you 70v at rated out you will have no issues.
I have done this countless times with no problems. The only issues I have had is cheaper transformers that don't like lower frequencies. If you high pass you should not saturate the transformer at higher power levels. Make sure you purchase a good quality Audio transformer.

Maybe Don can clarify
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Eric Madson-CTS
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Don Boone

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Re: need help with a 70volt speaker install
« Reply #14 on: August 15, 2008, 02:08:42 pm »

I was referring to connecting 2 good quality transformers on the 8 ohm speaker outputs of a JVC consumer receiver and connecting 12 70 volt ceiling speakers. The JVC would die within a month.

BTW 100 watts of 70 volt speakers would be a 50 ohm load. The JVC could have handled that load with no problem as long as the bass was turned down. The level would be pretty low though.

Don
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Eric Madson

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Re: need help with a 70volt speaker install
« Reply #15 on: August 15, 2008, 02:32:39 pm »

BTW 100 watts of 70 volt speakers would be a 50 ohm load.


Yes, assuming the amplifier is capable of reaching 70v.
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Eric Madson-CTS
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Hal Bissinger/COMSYSTEC

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Re: need help with a 70volt speaker install
« Reply #16 on: August 15, 2008, 08:48:13 pm »

Yes, assuming the amplifier is capable of reaching 70v.

Well yes. A 100w amplifier with a 70 volt output will deliver 70 volts across a 50 ohm load or more. A 100w amplifier with an 8 ohm output connected to the proper transformer (8:50) should deliver the same 70 volts at 100 watts, again across a 50 ohm load or more. So the amplifier would not need to deliver 70 volts, but as you say only about 28 volts at 100 watts. This is actually the way most constant voltage amplifiers operate. They use a transformer to produce the 70.7 or 100 volt output but they are also designed for it.

If you have a "consumer" or "pro" piece that is only rated at 100w@8ohms then the max rail voltage is only about 28v. If you try to tap off multiple 70v speakers for a total of 100w you will load the amp down past its rating.

No, not true. You will be putting a 50 ohm load on that 8 ohm output. Of course you will only be supplying about 16 watts to all of your speakers. The amplifier and speakers will operate quite happily though, assuming that's what you want.

Keep in mind also that consumer gear is not held to the same testing standards as commercial gear. The output power of consumer amps is usually hype. So that instruction book wattage you think you are getting could be much less. If you hang a transformer off the output and use it to feed a constant voltage system based on that assumed power output you may very well wind up overloading it.

-Hal
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