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View Full Version : Running speaker wire a loooooong distance....



kpippen
02-25-2007, 09:37 AM
Hello everyone,

I would like your opinions on the following question(s):

I need to power two JBL JXR125 at 150ft away from the power amp. Is it OK to use two or three twisted pair 12AWG speaker cables in parallel for this connection? Are parallel runs just as good as using a single 8 or 6AWG monster style zip cord? I would prefer to run parallel jacketed twisted pairs if this doesn't present some other kind of problem(s)?...

Three 150ft 12AWG twisted pairs in parallel...............to............One 6ft 14AWG
----------------------------------------------------O
----------------------------------------------------O----------------------------[JRX125]
----------------------------------------------------O

Thanks very much in advance!...:)

kpippen
02-25-2007, 07:06 PM
Advise..opinion....anybody????

Zilch
02-25-2007, 07:19 PM
12 Ga. stranded is 1.71 Ohms per 1000 Ft.

You're running 300 Ft. round trip, 0.513 Ohms for single, by my calcs.

Rule-of-thumb is <1/10 the load impedance....

kpippen
02-25-2007, 07:27 PM
12 Ga. stranded is 1.71 Ohms per 1000 Ft.

You're running 300 Ft. round trip, 0.35 Ohms for single, by my calcs.

Are you saying that one twisted pair 12 Ga. will keep my insertion losses below .5 db?.. This is the goal?

Zilch
02-25-2007, 07:33 PM
Note I fixed the calc. :p

What's your load impedance?

kpippen
02-25-2007, 07:40 PM
Rule-of-thumb is <1/10 the load impedance....

Zilch,

My bad....I read right past this part.. So your saying it all depends on my load impedance 2, 4, or 8 ohms?

This is good information but,....the question stands... Does it make any difference in regards to parallel runs or a large single run?

kpippen
02-25-2007, 07:43 PM
Note I fixed the calc. :p

What's your load impedance?

Zilch,

On one run the impedance will be 4 ohms constant, and on the other run the impedance will be 8 to 2 ohms depending on the amount of stage monitors used...

Zilch
02-25-2007, 07:46 PM
Yes, it depends upon the load impedance.

If it's 8 ohms, the loss is ~0.5 dB.

@ 4 ohms, it's ~1 dB.

Doubling the wires cuts the resistance in half.

If you're driving 4 ohms, and you want to stay at 0.5 dB, you gotta run doubled wire feed....

mikebake
02-25-2007, 07:46 PM
Put the amp right near the speakers and run 150 ft mic cords to the amp from the mixer/source. 150 ft speaker wire runs risk losing bass, punch, etc. In pro audio, the amps live near the speakers.

kpippen
02-25-2007, 07:50 PM
Put the amp right near the speakers and run 150 ft mic cords to the amp from the mixer/source. 150 ft speaker wire runs risk losing bass, punch, etc. In pro audio, the amps live near the speakers.

Hi mikebake,

If I could I would,...but in this particular application I need to keep the amps in the sound booth along with the mixer...

Zilch
02-25-2007, 07:52 PM
[Draggin' out the calculator again, then....]

Triple run cuts the resistance to 1/3,

Looks like you're at 0.7 dB loss running 2-ohm load with triple....

kpippen
02-25-2007, 07:53 PM
If you're driving 4 ohms, and you want to stay at 0.5 dB, you gotta run doubled wire feed....

Zilch,

Other than cost...would it hurt to run a triple?

kpippen
02-25-2007, 07:57 PM
Looks like you're at 0.7 dB loss running 2-ohm load with triple....

OK... does it hurt to run a quad?

Zilch
02-25-2007, 07:59 PM
Nope, assuming your amp can handle 2-ohm load. Just make sure your connections are good. That means clean, tight, and protected.

I wouldn't worry one heck of a lot about stage monitors sounding perfect....

kpippen
02-25-2007, 08:02 PM
This is good information but,....the question stands... Does it make any difference in regards to parallel runs or a large single run?

OK.... By the way the thread is moving I'm assuming the answer to my question above is NO?

Zilch
02-25-2007, 08:07 PM
The answer is "No," as long as you do the calcs to verify the combination is adequate for the load, consistent with your objective, as I believe we just demonstrated.... :thmbsup:

kpippen
02-25-2007, 08:11 PM
Zilch and mikebake,

Thank you for your time and advise...

duaneage
02-26-2007, 03:29 PM
I don't mea to awaken this thread but you could use a 2.4 Ghz audio transmitter and receiver to beam the audio to an amplifier and even use it from different sources,

clmrt
02-26-2007, 04:01 PM
I can see the day when us stagehands (knuckledraggers, we) no longer have to pull snakes.

All class-d amplification, so no more heavy amp racks....

:bouncy:


Now, those dimmer racks.....

kpippen
02-26-2007, 04:31 PM
I don't mea to awaken this thread but you could use a 2.4 Ghz audio transmitter and receiver to beam the audio to an amplifier and even use it from different sources,


I can see the day when us stagehands (knuckledraggers, we) no longer have to pull snakes.

All class-d amplification, so no more heavy amp racks....


duaneage and clmrt,

I wish I had the budget to go wireless... Our church (and the praise team rocks hard!!!) is moving into a new building... Unfortunately I gotta use whatever available to me (or what I can scarf-up)... I was able to get some JBLs though...:D

coherent_guy
02-26-2007, 04:55 PM
The only thing I can think of that might be a problem with multiple runs of cable of that length would be if the inductance and capacitance of the addtional cables would be an issue. Usually, a little more inductance is a good thing from an amps perspective, since many amps have a series inductor on their output and some amps become unstable when used with special low inductance cables. Capacitance is another story, as it may affect frequency response and possibly bug the amp. I doubt any of these factors would be a problem with a good pro amp.

kpippen
02-26-2007, 07:33 PM
The only thing I can think of that might be a problem with multiple runs of cable of that length would be if the inductance and capacitance of the addtional cables would be an issue..

coherent_guy,

This is exactly where I was coming from but I didn't want to make too much out of it... This is my first time on the forum and I didn't want to be alienated… Another thing to consider: does two 12 AWG wires have a larger cross section of conductor surface than say a 6 AWG wire... My ole-school training taught me that 80% of the electricity travels on the conductor surface (called skin effect) as opposed to the conductor core…:)

boputnam
02-28-2007, 07:34 PM
Put the amp right near the speakers and run 150 ft mic cords to the amp from the mixer/source. 150 ft speaker wire runs risk losing bass, punch, etc. In pro audio, the amps live near the speakers.


Hi mikebake,

If I could I would,...but in this particular application I need to keep the amps in the sound booth along with the mixer...
I agree with Mike - any good soundguy would! :p - but I hear your constraint(s).

I think twisted pair will be fine, given this situation. You have no choice, right? An alternative would be shielded twisted pair, or even shielded coax (but you need to keep the gauge low). The shielding will guard from RF, a certainty over long runs.

You have not said the amp Class or brand. You will loose amp efficiency and performance, particularly in the damping factor. That said, if your mains and wedges are of sufficient quality (the JRX are pretty good) you can probably get by on this. If you are biamping (you haven't said...) either the mains or the wedges, you will need to adjust the gain structure between the LF and HF. And, pay attention to the resultant EQ - make some good measurements and adjust.

Try it. Grab a 150-ft run of twisted pair and listen to it both on the mains and on the wedges. If it sucks, lift a choir pew and stuff the amps under there (where they should be). If you can live with it, good - then start planning on an upgrade where the amps CAN be at the front of the worship room.


Are parallel runs just as good as using a single 8 or 6AWG monster style zip cord?I would think twisted pair better for noise rejection. I have used it in "long" runs, but nothing like 150-ft. It's a house of worship, ferhecksake - it WILL work! :rotfl:

coherent_guy
03-01-2007, 05:19 PM
coherent_guy,

This is exactly where I was coming from but I didn't want to make too much out of it... This is my first time on the forum and I didn't want to be alienated… Another thing to consider: does two 12 AWG wires have a larger cross section of conductor surface than say a 6 AWG wire... My ole-school training taught me that 80% of the electricity travels on the conductor surface (called skin effect) as opposed to the conductor core…:)

I wouldn't worry at all about being alienated by the folks in this forum, they aren't a bunch of snobs, audio or otherwise.

Regarding skin effect, while it does exist I've read that it is not much if at all a factor with audio frequency signals. The main purpose of large gauge wire is to keep impedance low with long runs of cable or for high current applications.

Having said that, I use relatively heavy gauge cables for short runs and use litz wire cables that are usually associated with alleviating skin effect problems. Frankly the real reason I use these is audiophile nervosa . . .

mikebake
03-01-2007, 07:58 PM
Hi mikebake,

If I could I would,...but in this particular application I need to keep the amps in the sound booth along with the mixer...
Why?

kpippen
03-03-2007, 02:13 PM
Why?

Hello mikebake,

Very good question...but because of the several variables and reasons it would take a lot explaination and typing to answer... One of the key reasons is: this sound system is for our new youth center and I want to keep all of the sound equipment in one secure and centeralized location...

I was on Crowns website last night and I saw a table that's printed in all of their operation manuals:


Using the guidelines below, select the appropriate size of wire based on the distance from amplifier to speaker.

Distance / Wire Size
upto 25' / 16AWG
25-40' / 14AWG
41-60' / 12AWG
61-100' / 10AWG
101-150' / 8AWG
151-240' / 6AWG

Seeing this information printed in the operation manual from one of the best amp manufacturers makes me feel even more comfortable about the distance I'm running...

boputnam
03-04-2007, 04:35 PM
...One of the key reasons is: this sound system is for our new youth center and I want to keep all of the sound equipment in one secure and centeralized location... It seems you might be able to easily secure the amps (and crossovers?) in a ventilated pen / closet / doghouse closer to the mains/monitors and avoid the long amplified run. Just a thought...


I was on Crowns website last night and I saw a table that's printed in all of their operation manuals:

Using the guidelines below, select the appropriate size of wire based on the distance from amplifier to speaker.

Distance / Wire Size
upto 25' / 16AWG
25-40' / 14AWG
41-60' / 12AWG
61-100' / 10AWG
101-150' / 8AWG
151-240' / 6AWG

Seeing this information printed in the operation manual from one of the best amp manufacturers makes me feel even more comfortable about the distance I'm running...Yea, but as before, just mind that this set-up will be less efficient than having shorter runs. Likewise, stick with twisted-pair (shielded, too :yes: ).


151-240' / 6AWGA thought: my brother in-law had his fabrication shop broken into last week. The crooks cut though the sheetmetal walls. "All" they took was ALL the heavy electrical wiring to the overhead cranes and chain-drive lifts. They took the wiring down, srtipped it and took the copper wire. At $2.74/lb, it sure got their attention. :(