Film-Tech Forum ARCHIVE: Need help with wiring speakers to play intermission music in restrooms

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Posted by Justin Hamaker (Member # 2165) on 03-22-2012, 01:45 AM:

We have a UltraStereo distribution amp with an extra channel we would like to use to play our intermission music in the restrooms. Unfortunately I'm having trouble getting it to work.

Each restroom has a single speaker which simply has a black and red terminal. I am wiring the speakers in a "daisy chain" where input comes in to the speaker in the women's room and then a lead attached to each terminal goes over to the same terminal on the speaker in the mens room.

I have two runs of single pair wires running from the distribution amp to a Pyramid SEA-2500X Professional Home Studio Pre Amp.

At the distribution amp the reds are wired to the left and right and the two blacks are wired to the commons.

At the amp, I used a stereo mini-jack to RCA cable and cut off the mini-jack. I wired the reds from my cable runs to the red and white from the mini-jack cable and then the commons were wired with negatives(?) from the mini-jack cable.

Similarly, the output run of a single pair was wired with the red to the red and the black to the white of a stereo mini-jack to RCA cable. The negatives(?) from the mini-jack cable were twisted together, but not wired to anything else.

When I plug the input and output wires into the appropriate jacks on the amp, I get no output from the speakers. However, when I use an RCA to RCA adapter to directly connect the input and output, I get a very faint output from the speakers.

When I plug the input into the amp and then use a pre-made RCA to RCA cable, I do get output from the amp into Non-Sync 1 on a CP500.

When I plug the input into the amp and then use an RCA to stereo mini-jack to plug into a powered iPod speaker, I do get output from the amp.

The only thing I have not been able to do is get output from the amp to the speakers. I have tested this cable run by twisting both wires together at one end and testing the resistance at the other end, and the wires seem to be fine.

Posted by Monte L Fullmer (Member # 2797) on 03-22-2012, 02:20 AM:

First - what is the speaker resistance?

Going "daisy chain" isn't the best way since that's a lot of line resistance for a single run making the one line drive two speakers from one source.

You should do separate runs to each speaker from the MDS.

What does it sound like when you take one speaker out of the equation?

Posted by Justin Hamaker (Member # 2165) on 03-22-2012, 02:27 AM:

There is no perceptible difference between one or two speakers in the configurations where I have been able to get a signal to the speaker. The problem is I can't seems to get it to work when outputting from the amp and the signal going straight from the distribution amp is too weak - even with both left and right turned up all the way.

Posted by Frank Cox (Member # 6258) on 03-22-2012, 03:28 AM:

Maybe you just haven't got enough oomph left by the time the signal reaches the destination. How far are you running it?

Perhaps you should look at a self-amplified ceiling speaker like a Bogen

Posted by Monte L Fullmer (Member # 2797) on 03-22-2012, 04:14 AM:

"Yo"..Justin..

Coming from any "Pre-amp", the output of the pre-amp needs a power amplifier to drive the speakers.

Output alone from a preamp is so very low in itself even with it's volume control up all the way- why it needs the power amp to make the attached devices heard.

I looked at the manual of this "Pyramid SEA-2500" and you definitely need a power amp between this unit and the speakers.

Thus, coming from a MDS unit, you're kinda going backwards heading the signal into a pre-amp.

You should drive those signals from the MDS directly to a power amp and skip this pre-amp thingey.

The USL MDS unit should volume adjustments on the one channel to set the volume needed to go into the power amp.

Try this one out: If you got an old AM/FM receiver hanging around the house, these make great power amps to drive your two speakers since they have AUX imputs to receive signals from any source.

Posted by Louis Bornwasser (Member # 3063) on 03-22-2012, 06:40 AM:

Daisy chain is OK, if you get a suitable power amp (10 watts or less is enough).

Speakers will need line matching transformers to use the daisy chain system. Be sure the amp has a 25 volt or 70 volt output to match the speaker transformers, Louis

Posted by Louis Bornwasser (Member # 3063) on 03-22-2012, 12:14 PM:

Shouldn't the restrooms have their own music, considering the task-at-hand?

Posted by Randy Stankey (Member # 64) on 03-22-2012, 12:45 PM:

What? Should the restroom speaker play songs like "Singing in the Rain" or "Bridge over Troubled Water" or something?

[Wink]

Posted by Larry Zuverink (Member # 1483) on 03-22-2012, 01:22 PM:

Do the speakers already have transformers? If they are already 70v and the amp is not you will not get much signal there. You can buy transformer for the output of the amp. Also go parallel. Do you really want all the speakers to go out if one is bad?

Posted by David Buckley (Member # 2600) on 03-22-2012, 07:53 PM:

Yeah, lack of a power amplifier. That's easily fixed for less than 50 bucks on eBay, hunt for "paging amplifier".

But don't buy one just yet...

The question as noted above is to do with loudspeaker impedance; are the red and black terminals actually on the speaker driver itself, or on the outside of a box containing the loudspeaker? Is there anything written on the box or loudspeaker? Things like 4 or 8 of 16 ohm, or 70V or 2W / 4W /6W / 10W are all good clues. if its just the loudspeaker is there a transformer or other odd lump attached to the frame?

The reason this need to be known is that the output of the paging amplifier needs to match the speaker load, and hence the questions.

Posted by Michael Voiland (Member # 5386) on 03-22-2012, 10:35 PM:

The old TOA amplifiers the silver 900 series was good. They will do standard impedance and 25 and 70 volt so you cant really good wrong with one. Toa 900 Series A-903A 6

Posted by Kenneth Wuepper (Member # 1174) on 03-23-2012, 07:22 AM:

If you are playing with speakers at voice coil impedances, here is a little graphic program that will assist you in "seeing" what is happening.

http://www.bcae1.com/spkrmlti.htm

Posted by Dave Macaulay (Member # 813) on 03-23-2012, 10:27 AM:

1: You need a power amp.
2: the mini-jack white and red are the left and right signals, the shield is the return. To get a signal you would go from red or white to the shield.
3: Assuming you want mono (what else, with one speaker in each bog?) and the n/s feed is stereo you should switch the MDL output to mono: there's a dip switch on the DA card to do this for any output channel. Just twisting together the red and white wires works but is not optimal. Then you only need a simple mono PA amp, Radio Shack used to have inexpensive ones. You only need a few watts of output power, probably you don't want disco toilets.