Wiring Speakers with Very Different Lengths

[hankallan]

Hi,

Here's an interersting situation - I have a performance space that's wired so one speaker is 10 ft from the amp and the other is almost 90 ft from the amp. When the two 8 ohm speakers are wired in series as 16 ohm there is no sound. In parallel as 4 ohm, only the closer speaker has output.

How can both be connected to get a decent output without rewiring the room? The manual for the amp mentions using a line transformer.

Any ideas?

thanks in advance,
Hank

 

[Hartono]

something doesn't seem to be right here, did all the speaker have sound if hooked up individually ?

 

[joe carrow]

My initial thought was that the long run of wire would add up to a lot of extra resistance that would harm things, but even checking at 16 ga, the added resistance of the 90 ft run is less than 2 ohms.

What model of amp are you using?

 

[JasonB]

Hi,

Here's an interersting situation - I have a performance space that's wired so one speaker is 10 ft from the amp and the other is almost 90 ft from the amp. When the two 8 ohm speakers are wired in series as 16 ohm there is no sound. In parallel as 4 ohm, only the closer speaker has output.

How can both be connected to get a decent output without rewiring the room? The manual for the amp mentions using a line transformer.

Any ideas?

thanks in advance,
Hank

Sounds like you either have a broken wire or a broken speaker. A 90ft run of wire may not be the best situation but even if it's a tiny high gauge wire you would still get a reasonable amount of output.

Start off by swapping the two speakers, if the problem swithes sides to the shorter run of wire then you know the problem is with the speaker, if not then it's the longer wire that's the problem. A way to double check the wire is to dissconnect it from both the speaker and the amp, then twist the two leads together at one end. Now check the resistance between the two leads at the other end with a multimeter. If you have used a reasonable gauge wire it should read less than a few ohms. If it reads very high or not at all you have a break in the wire somewhere.

Hope this helps,

Jason

 

[Willitwork]

Is this a PA setup? If so check if the amp is set to mono.

 

[CONVERGENCE]

If you tell us more about your amp Speaker terminals and the speakers themselves. Perhaps we could be of more help.

What I know as a rule.When wiring multiple speakers to an amp it is best to wire each speaker directly to the amp and not in a daisy chain fashion.This will improve the ability of the amp to control the speaker movement. This control is known as dampening factor.

I won't go further for now untill we hear from you.


Here is a table for wire gauge

24awg 22awg 20awg 18awg 16awg
8 ohm 20 feet 35 feet 50 feet 85 feet 115 feet
4 ohm 10 feet 15 feet 25 feet 40 feet 60 feet

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[tinitus]

I agree .... "with the speakers in series = no sound ... and in paralel only one unit playing" .... somethings definately broken

 

[hankallan]

Ok to answer some of the questions about this strange problem:

The amp is Radio Shack MPA-101 (not Jamo). It's a PA system, yes. I did find the manual online and no mention of a MONO button nor did I see one on the unit.

Funnier thing is the two speakers worked for a few minutes when initially hooked up. Then the far one went out so I switched from series to parallel wiring and then got output from the close speaker only.

So I could swap speakers or try hooking them up individually to test.

As for series vs. parallel I thought series might be better because if parallel, then the long loop would have drastically different power and sound poor.

btw, whats an easy way to doublecheck the polarity (+ - on which wire) from end to end on the far loop? The short loop is easy with a meter.

thanks,
Hank

 

[CONVERGENCE]

First test both speakers seperately.

If speakers are working then it should work in paralell or series.

Check if in phase . Use a 2 volt battery to see if woofer is pushing or pulling.

Once that is determined. If your speakers are working individually
. They should be working in paralell or series.

If no sound.

Either your amplifier is defective or your speaker is defective.

...................................................

 

[tinitus]

Are we talking about two different speakers in seperate rooms, wired to the same channel ?

 

[CONVERGENCE]

I checked the amp specs . It's for PA app. Rated 100watts.
Output 4,8,16,70V. GND.

I'll let him answer your question about speaker placement.

.....................................

 

[v-bro]

Check if in phase . Use a 2 volt battery to see if woofer is pushing or pulling.

That's my method!

Perhaps good to add that most cones move forward when the battery + is connected to the speaker +, an AA battery will do

Some awkward speakers move backwards

But it doesn't matter, as long as both are moving in the same direction....

The transformer they mention in the manual is when really really long cables are necessary (for public adress sytems for instance) you can crank up the voltage of the audio (they mention 70V, but 100V systems are common too) and step it down with another transformer at the speaker end....it saves energy and makes thinner and much longer wires possible...

http://support.radioshack.com/support_audio/doc14/14623.htm