Film-Tech Forum ARCHIVE: Terminating heavy-gauge speaker runs

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Posted by John Hawkinson (Member # 1135) on 08-18-2006, 06:59 PM:

Hi, all.

We're getting ready to clean up some heavy-gauge speaker runs that were run in a hurry a while back, and I'm curious what people use to terminate such runs.

At the moment, we have 8AWG coming off of dual banana connectors into amps, and running straight into the speaker. This has proven a bad idea, because 8 AWG is really hard to work with. There is a lot of strain and weight on the amp-side connectors. And, of course, on the speaker end, getting 8AWG under screw terminals is painful (this was no surprise).

We'll switch out the speaker end to a Neutrik Speakon NL8. Ideally we'd like to terminate the wire run in a wall plate near the speaker -- how should we connectorize that? One thought is to use a Speakon there as well, but they're a tad pricey and (more importantly) don't accomodate 8AWG. We could butt-splice the 8AWG down to 12AWG and run the 12AWG into an NL8 receptacle, and then use a short 12AWG jumper NL8FC cable between the speaker and receptacle.

Historically, we've used NEMA twistlock connectors for those receptacles (who knows why? They don't seem to be cheaper than Speakons, and they top out at 5 conductors anyhow, which doesn't work for triamped speakers). An NL8 mated pair is ~$15, versus about ~$50 for a mated NEMA L23-20 pair.

On the amp side, we have a mix of QSC amps (EX and PLX series),
both with 5-way binding posts and NL4 Speakons. It seems clear we want to use the 5-way posts with dual banana plugs, since that lets us swap amps and channels much more easily than the Speakon would (because we use some amps in bridged mono configurations and some in 2-channel mode, and switching between requires rewiring the Speakon, whereas the we can just rotate a dual banana plug 90 degrees).

A couple of previous topics touch-on these issues, but not too deeply:

"Splices in speaker wire runs" (2003) discusses wire nuts for splices, debates about soldering, with a brief mention of Speakons (and their 12AWG limit)
"long interconnect (balanced) to amp..." (2000) also talks about Speakon size limitations.

Questions:Anyhow, at the speaker end, how should we get from 8AWG into an NL8 male (or other) panelmount? A few of inches of 12AWG seems the right answer, but should we buttsplice, wirenut (seems dodgy), barrier strip (excessive?), or something else?

Similarly, on the amp side, it seems clear we need something less weighty feeding into the dual banana, what's a good choice for stepping it down?

Thanks for your thoughts.

--jhawk

Posted by Steve Guttag (Member # 268) on 08-18-2006, 10:13 PM:

OMG...not the twisting of speaker cables thing again!

John, there are Bannana plugs that are designed for #8 and even larger wire (gold plated even) so at the amp end, you are safe.

I would make a pigtail splice at the speaker end though. If you have the time, soldering and then wirenutting the splice in a Jbox will be just fine.

Ever looked at what wire is on the other side of the speaker terminals in a typical speaker? Pretty scary stuff!...rather small often. Even when you get to the driver you have the connection at the driver terminal, then the tensil lead to get to the voice coil wires...so there is no such thing as splice-free. At least a splice you make you can control the quality.

Dont forget on the 8-pole speakons that you double up on the LF section for a 3-way speaker system so you can get two #12s to feed the LF or even two #14s should be just fine unless your interconnect cable is to be absurdly long.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 08-18-2006, 10:35 PM:

quote:
OMG...not the twisting of speaker cables thing again!

Fuckin a right Bubba!

Posted by John Hawkinson (Member # 1135) on 08-18-2006, 11:04 PM:

We have banana plugs for #8. At first we thought they would be a good idea.

But what experience showed is that the cable is sufficiently
heavy that the weight of the #8 is almost sufficient to pull the banana out of the amp, so it needs to be very carefully strain-relived and tie-wrapped in a rather awkward way.

Add to that that, despite being for #8, it's still a royal pain
making them fit.

--jhawk

Posted by Steve Guttag (Member # 268) on 08-18-2006, 11:14 PM:

Oh come on...you are from MIT and I don't mean Moving Image Technologies....this should be a snap for you guys! It isn't like making a cue-marker!

Perhaps you should have used a finer strand cable that was easier to work with. [Wink]

I've made the bananna plugs thing work in the past...now that most of the amps we use have screw terminals, we normally use them instead.

Steve

Posted by Louis Bornwasser (Member # 3063) on 08-19-2006, 09:24 AM:

I would look at the electrical supply store for a suitable #8 terminal block. On the other side, reduce to a short, smaller cable suitable for your bananna plug.

Alternatively, you could butt splice to a smaller cable and cover with heat shrink.

Note: you may have to fold the smaller cable once or twice to get good connection to the (very) large #8 fitting.

As previously stated, very small wire is inside your cabinet. Short runs of small wire are OK; long runs are to be avoided due to loss. Louis

Posted by Monte L Fullmer (Member # 2797) on 08-20-2006, 04:15 AM:

quote:
not the twisting of speaker cables thing again!

..which brings the intesting question on this - I have some old 6 plexes that had two mono houses that were converted to stereo, and the left/right and surrounds were run with 14g twisted pair - and the twisted pair was done on site by taking two rolls of 14g put these rolls on a broom handle, with a person holding the broomhandle to keep the two rolls taught, with the person handling the drill, playing tug-of-war with the holder by operating the drill and to make the twisted pair runs.

What I couldn't get over, with all of this twisting, tuggin and fishing all of this through rather small conduit, why not use the simple 14/2 braided wire by itself since I've seen other installs using this much simpler version instead of all of this twisting?

I know that of the twist is to keep the flux lines from each wire at a minimum, but with the other, it seems that there is no difference no harm in the sound reproduction .....

...have to ask .... - thx_monte

Posted by Mark Gulbrandsen (Member # 72) on 08-20-2006, 05:08 AM:

quote: Monte L Fullmer
and the twisted pair was done on site by taking two rolls of 14g put these rolls on a broom handle, with a person holding the broomhandle to keep the two rolls taught, with the person handling the drill, playing tug-of-war with the holder by operating the drill and to make the twisted pair runs.

Don't tell Guttag about this [Eek!]

.

Actually twisted pair has several advantages with one major advantage being that the twisted pair cancels out any RF interference that the wire itself might pick up... its a long antenna! It also helps eliminate mututal coupling between close runs in a rack or conduit.

Mark

Posted by Louis Bornwasser (Member # 3063) on 08-20-2006, 06:12 AM:

Because of the very low impedance, mutual coupling is not much of a problem with speaker runs.

Conduit is required: the antenna effect is real. One consideration is the effect of high power AM stations nearby (CB & broadcast). Another is lightning: Today's modern amplifiers have only one weakness; they are somewhat not tolerant of high voltage spikes on their output lines. One theatre we modernized the contractor did not want to use conduit so he tacked up romex (non shielded) cable on the underside of the roof beams. Over time, the amplifier failure was 10 times the usual failure mode. Later, conduit was installed, and no amplifier has failed since. Failures corresponded with stormy weather. Louis

Posted by Steve Guttag (Member # 268) on 08-20-2006, 11:27 AM:

I can see we are going to have to go through this again...

The coupling is actually quite real...long lines run together will impress signals across each other. So tiwsting is a good idea for that too. Keeping audio and speaker lines separated from power lines, even in conduit is a good idea.

As for twisting...there are many wrong ways and few correct ways. It is impractical to twist very long runs of cable in the field due to the space and time needed unless one wanted to make a machine to aid in doing it.

The essentials of properly twisting wires would be a farris-wheel type contraption to hold the various wire spools. Just in front of that would be a mandrel that is attached to the farris-wheel so that the hole in the mandrel that the wire passes through is always in front of its respective spool. You then have a take up spool for the now twisted wire. The speed relationship of the take up spool versus the mandrel/ferriswheel motor sets the twists per inch.

When twisting wire, the individual conductors should not receive any additional twisting. That is, if you were to mark the top side of the wire before twisting, it should stay on top after twisting and not also twist around like a barbar pole.

Posted by Stephen Furley (Member # 1277) on 08-20-2006, 12:01 PM:

A stranding machine; but do you think I can find a decent pictute of one at the moment?

Posted by John Hawkinson (Member # 1135) on 08-20-2006, 11:43 PM:

Oh, Steve. The problem with the MIT thing is that we spend a little too much time overanalyzing [Smile]

. Nobody's really comfortable with the wire nut approach, and butt-splicing #8 without solder is of questionable reliability, as is putting on ring terminals, so we look for a fancy terminal block solution with clamping terminals...

You say, "Don't forget on the 8-pole speakons that you double up on the LF section for a 3-way speaker system..."

err...I just went and checked the speaker in question with a multimeter (screw terminals, not the speakon, because it was easier). 4- and 4+ are not paralleled with anything else inside the speaker. (This is a JBL PD5322/64 with a 339335-001 "input plate, NL8" and a 352565-001 "PD, NL8, input cup overlay").

Unless the screw terminals 4+/4- are not in paralled to the Speakon, they are unused, not doubled up for LF.

As for the cue markers--oh jesus. I AM SUCH A SLACKER.
"I'll do it Real Soon Now(tm)."

Maybe you guys could take the twisting crap back to the twisting crap thread?

--jhawk

Posted by Bruce Hansen (Member # 281) on 08-21-2006, 05:56 PM:

I am not saying that this is a good thing to do but, if you have no other choice, after striping the (stranded) conductor you can cut several of the strands off in order to fit the cable in a small connector. The strands are all touching each other inside the cable, so all the strands will still be used to carry the signal. You may want to put some tape (or heat shrink) around the area where you cut off the strands.

Posted by Monte L Fullmer (Member # 2797) on 08-22-2006, 05:28 AM:

quote: Bruce Hansen
The strands are all touching each other inside the cable, so all the strands will still be used to carry the signal.

... and if you really want to get brave, solder the wires in the connector,along with the crimp after taking off the crimp plastic, then use the right size diameter of shrinktube to cover over the soldered connections to really give it a good connectivity and longetivity.

Posted by Steve Guttag (Member # 268) on 08-22-2006, 09:45 AM:

quote: John Hawkinson
err...I just went and checked the speaker in question with a multimeter (screw terminals, not the speakon, because it was easier). 4- and 4+ are not paralleled with anything else inside the speaker. (This is a JBL PD5322/64 with a 339335-001 "input plate, NL8" and a 352565-001 "PD, NL8, input cup overlay").

Unless the screw terminals 4+/4- are not in paralled to the Speakon, they are unused, not doubled up for LF.

Trying to make me look bad, eh? Yes you are correct that JBL did not double up on the terminals. They are considered "loop through" terminals.

But, bright guy...you can place jumpers on the screw terminals to double up the +/-1 with the +/-4 terminals so that the smaller gauge snake cable wires are not an issue for the LF section. Don't forget to match + for + and - for - [Wink]

Steve

Posted by John Hawkinson (Member # 1135) on 08-22-2006, 09:50 AM:

Ooh. Sometimes the brightness fades. That's brilliant! [Smile]

--jhawk

Posted by Jon Miller (Member # 163) on 08-22-2006, 07:53 PM:

But if the fortune cookie that came with my lunch today is any indication, it's only temporary. [Smile]

Posted by Steve Guttag (Member # 268) on 08-22-2006, 08:43 PM:

But that is YOUR forune...it does no good for John (even spelled differently than your Jon). [Wink]

Posted by Jon Miller (Member # 163) on 08-23-2006, 12:13 AM:

Those things are so generic anyway I felt I could pass it on. FWIW, Steve, it was just a lame attempt to expand on jhawk's original pun. [Smile]

Posted by John Hawkinson (Member # 1135) on 08-24-2006, 07:23 PM:

For what it's worth, we went with Speakon NL8MPRs mounted in flushmounted handyboxes chase-nippled to junction box on the other side of the wall, and then a eurostyle terminal block in the j-box.

I am not impressed with the termination on the NL8MPR. It's 3/16" quick-disconnect, but the terminals are really close to each other and it's possible to bend the connectors to short if there is a cramped space. Also, a 1 1/2" handybox was not deep enough for it, at least with 12AWG; had to switch to 2 1/8".

Looking now, I belatedly discover that the Speakon STX (Weatherproof) version, the NLT8MP, supports 1/4" quick-disconnects and goes down to 10AWG. If I had to do it over, I guess that would have been a better choice (and it's supposedly compatible with the NL8 series). On the other hand, it doesn't look like many vendors stock the STX receptacles...

Rack termination is still TBD. But we will likely use DIN-rail mounted modular terminal blocks.

--jhawk