Stereo question - office

Reply

  #1  
Old 12-17-07, 05:27 AM
E
Banned. Rule And/Or Policy Violation
Thread Starter
Join Date: Nov 2007
Posts: 17
Received 0 Votes on 0 Posts
Stereo question - office

A friend of mine had someone come and install 7 speakers in their office to be controller by one stereo system. All the wiring was complete and a stereo was the last thing needed

The installer never completed the job, taking their money.

My friend wired up her stereo to the exisiting wiring and the stereo worked for a while and then stopped. Everything on this stereo works fine, except the speakers.

Its a basic Sony 3 disc changer. i have other info if need.

I am looking for some assistance to help get this working.

Does anyone know what might be missing or what would need to be added to get this to work.

any help will be great, thanks
 
Sponsored Links
  #2  
Old 12-18-07, 04:03 AM
R
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,233
Received 1 Vote on 1 Post
Some more info would be helpful.

Have you tried the stereo with a known working set of speakers?

Are the speakers installed in the ceiling tiles? Does each speaker have a transformer between the incoming line and the speaker terminals? Or are they 8-ohm speakers with the wires directly connected to the speaker terminals?

How many cables come out of the ceiling to connect to the stereo?

The proper way to do this with 7 speakers in an office is to use a constant-voltage system with 25v or 70v transformers. It's usually not stereo; it's mono. The speaker lines connect to a commercial-series amplifier that has a 25v or 70v output. Connecting a home stereo to the line wouldn't produce much sound, so the volume would probably be turned up too high and eventually burn out the amplifier.
 
  #3  
Old 12-18-07, 01:16 PM
E
Banned. Rule And/Or Policy Violation
Thread Starter
Join Date: Nov 2007
Posts: 17
Received 0 Votes on 0 Posts
Thank you for your response.

I will tell you what I know right now and stop by the office and get any additional information you need.

The speakers are installed in ceiling tiles.

I am not sure if the speakers have transformers or not.

From the 7 speakers, all the wires are pulled back to the stereo area. There are 7 pairs of wires, which have then been spliced. So in turn 2 pairs connect to the stereo. (my guess is 2 positive and 2 negative)

Someone connected these wires to the stereo and the speakers worked. I am not sure what volume level they had to turn it up too.

Eventually the speakers stopped working.

The stereo did work with the speakers it came with and does not now.

let me know what else you need
 
  #4  
Old 12-18-07, 02:51 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 10,134
Received 37 Votes on 35 Posts
You can tell if the installed speakers are proper PA speakers by looking to see if there is a transformer attached to the speaker terminals.
She likely has to buy a proper PA amplifier and the stereo is likely burned or a fuse is gone.

Does the stereo work on headphones?
 
  #5  
Old 12-18-07, 04:03 PM
R
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,233
Received 1 Vote on 1 Post
"let me know what else you need"

We need to know if the transformers in or on the speakers are 25v or 70v. We also need to know the wattage "tap" of each speaker. Most times, the transformer is labeled. The transformer is the square thing attached to the speaker (pic below courtesy of Rauland).



Either way, your friend needs a proper amplifier to drive a constant-voltage system. Here are some samples. Most have inputs for a CD, iPod, or radio plus inputs for a microphone and telephone paging.
 
  #6  
Old 12-18-07, 04:19 PM
J
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 7,567
Received 251 Votes on 221 Posts
Since the stereo does not operate now it is good assumption that it is blown. The output of a stereo system not design to be connect to 7 speaker in parallel.
You need to know what type speakers you have and then get an amp to power them. Probably what you need is a PA(public address) amp not a stereo system. The PA amp will have different inputs to connect thing like a satellite service(MUZAK), Microphone for paging, CD player, tuner.
 
  #7  
Old 12-18-07, 05:00 PM
R
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,233
Received 1 Vote on 1 Post
Originally Posted by joed View Post
The output of a stereo system not design to be connect to 7 speaker in parallel.
That's not necessarily true. Eight 16-ohm speakers in parallel would present a load of 2 ohms. Most of today's higher-end amps are designed to run into two ohms, but a cheapo stereo is designed only to run its own (cheapo) speakers.
 
  #8  
Old 12-28-07, 09:06 AM
E
Member
Join Date: Dec 2007
Location: New York
Posts: 22
Received 0 Votes on 0 Posts
Its a NUTONE - Music Distribution Ceiling Speaker
Model: IS-920

The Instructions say:

Amplifier Power

IS-920 should be used with a stereo amplifier with 35 to 70 watts maximum per channel power rating.

OK now that we solved that, where would i go to get this and how much will it cost?
 
  #9  
Old 12-28-07, 01:38 PM
R
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,233
Received 1 Vote on 1 Post
Cool. Glad to see you got that username thing worked out.

Those are 25-ohm speakers, each rated for 70 watts. Any home stereo receiver will work, provided it has at least 35 watts. A 100-watt per channel system is common and will work fine. Make sure it is rated to work into a minimum 4-ohm load.

The wiring is critical, though. I'd pull all of the wires off the pigtails and check for shorts. Use a multimeter set to ohms and read each line. If you read zero ohms on any of the lines, the short needs to be corrected. Also check each wire for a short to building ground. If the installer was sloppy he could have damaged the insulation on the cable and it may be touching the ceiling grid.

Once you've determined that the wiring is good, put three speakers on one channel and four on the other. Pigtail the field wiring to two sets of wires that will connect to the receiver's speaker outputs. Make sure all the reds connect to reds (or white/white), and blacks to blacks.

You'll have an unbalanced load on the two channels of speaker outputs, but both should be well above the minimum:

Four 25-ohm speakers = total load of 6.25 ohms = safe.
Three 25-ohm speakers = total load of 8.3 ohms = safe.

The original system probably blew up because it was a cheapo all-in-one unit, right?
 
  #10  
Old 12-30-07, 03:47 PM
E
Member
Join Date: Dec 2007
Location: New York
Posts: 22
Received 0 Votes on 0 Posts
I have checked the wiring and all seemed fine, polarity was not clearly marked.
The speakers were divided (4 on 1 pigtail and 3 on the other)

The speakers did work for a while, the volume was fine and did not need to be turned up all the way to hear it.

I am still unsure what would have cause the stereo to stop working.

I dont know what the allowable ohm rating is on the damaged speaker. I do however know that there were 2 opening for speakers.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: