I need to wire for 2 XLR Wall Plates for 2 Subwoofers on either side of a theater room. The Jacks will be around 20 feet away from the equipment rack. We are using a krell pre-amp and 2 martin logan descent subwoofers. I was wondering what the best options are for wiring to the XLR wallplate locations and what are the best wallplates available for this task. I was thinking just a run of some good 4 conductor 12ga speaker wire to each location and using some corresponding jacks that adapt the 4 conductor wire to an XLR connection on the front side. Is there a better way to do this or is this the only or best way? Any information on this subject would be usefull. Additionally, Is there a good way to run a 15 pin VGA cable around 30 feet to a projector or should I just stick with Component, S-video, and composite?? Thanks for the assistance...

Joe

This message was edited by joe sexton on 09/26/02 12:16.38.

First off, let me say I'm not a custom installer. I do work in the broadcast industry however, and do a LOT of work with XLR cable. I don't understand why you want to run 4 conductor cable, then use an adaptor. I would suggest finding a 3 conductor cable, then connect directly to the XLR connector. You should be able to find cable, wall plates, and everything else at Markertek (www.markertek.com) or Clark Wire & Cable (www.clarkwc.com).

Hope this helps.
SamG

you can use 4 conductor because the 4th ( shield ) is soldered to the connector as a ground (balanced).

Next your projector. What is it? What are the sources ? and are you using a scaler/ optimizer?

For VGA what we tend to do is buy a good prefab cable (25') then attach normal VGA cables at either end for the rest of the length (i.e. one probably came with the projector). Those prefab 25' cables tend to be thick and not as flexible (but have better insulation) as the smaller cables. So you have a thick insulated cable for most of the run and thin flexible cable so it does not become an eyesore

Twix, that is exactly what we were thinking about doing, unless someone had any better ideas. we are using a sharp dlp projector, the 9000. we aren't using a scaler. Our sources will be cable and dvd. I know I know we should be using a scaler but the client doesn't think the video aspect of this system is very important. He is more concerned about the audio. We are just adding a projector and DVD player to his audio system pretty much. Thanks

What kind of a signal are you going to be running to the subs? An amplified speaker level from an amp to the sub....or a line-level signal to the subs?

Nick

Well, I would say 12 gauge 4 conductor wire is crazy, and that unshielded cable is even crazier...if it indeed is a true Balanced line level signal your running.

I am confused. Four conductor speaker wire to a subwoofer? I assume, then, that you are using the high-level inputs of the sub.

Large gauge wire is preferred when it is necessary to carry lots of current to a loudspeaker. Subwoofers, though, if they have their own built-in amplifier (you don't say, but most do), have a relatively high input impedance, so you could probably get by with 22 gauge wire! But I would run 18 just for the heck of it.

SamG, twix, if he is using 4 conductor speaker wire, then two conductors come from the main amp's grounds and two come from the main amp's hot leads. There is no fourth wire that could be the shield. Standard practice is NOT to connect the two grounds together, even though they may electrically be identical.

Let's not forget that XLR connectors come in different pin configurations. A Google search for XLR-4 comes up with many listings, and there are also 5, 6 and 7 pin XLR connections.

You should solder your speaker wire directly to the back of the XLR connectors, then come out of the wall to a cable that has wire soldered directly to connectors, the other ends of which go to the sub. There is no need for adaptors, right?

Anthony's reply for the VGA feed is right on. The larger cable also has less loss of high frequencies (image detail) than the skinnier wire. That is why longer cables are usually bigger.

Ernie

We normally use 22 Gauge 4 conducter Shielded wire and have had no problems.

We are running a line level signal to the sub not an amplified speaker signal. It will be LFE. the 4 conductor wire is just for behind the walls and will be converted to XLR at both ends unless someone has any better ideas for running an XLR line through the walls. I know I could use coax for an rca type connection but we want to use XLR. I am just wondering if anything would be better than that. I don't know if speaker wire would work well for that or a smaller gauge line-level wire. That's what I am trying to figure out. Thanks.

Joe

Normal XLR connections use a cable with two insulated conductors that are shielded, and, if the shield is a foil, a bare wire, called the "drain" that makes contact with the entire length of the shield, and makes connecting to it easier, and is normally connected only to the chassis.

This type of connection is called "balanced", because there are two wires, neither at chassis ground, that carry the signal, unlike a standard coax, called "unbalanced", which has only one insulated conductor and the shield, which means that one of the conductors is actually "exposed" to noise.

The two insulated wires in a balanced cable will pick up induced noise equally, and "in phase", so an amp input with a "common-mode noise-rejection stage" will cancel out the noise, resulting in a quieter signal. The shield is used only as it's name implies.

This is why they're normally used in professional areas, and benefit longer cable runs the best. If your sub amp has only standard RCA-type inputs, there is no real benefit of using the XLR connectors.

As a compromise, if you're set on using them, use a two-conductor-plus-shield cable as described, and connect the shield and one conductor to the ground at the source end, and the grounded conductor only at the sub end. The shield will be grounded only at one end, and should help reduce noise pickup and maybe even ground loops a little.

Larry
www.fineelectricco.com

Larry has it pegged. You did not tell us from the outset that your signal was line level, and you told us you were thinking of using speaker wire, so we all went off in the direction of "high level connections" to the sub.

If it is line level, it definitely has to be shielded, so all "speaker wires" I have heard of are immediately wrong for the job. We have to remember that "speaker wire" does not have a single definition, so someone could make a shielded wire and call it a speaker wire, but in general, they have no shield.

There is a distinct advantage to using the XLRs, but you won't think of it if you are thinking of electrical signals, hum, noise, ground loops: because of their latch mechanism, they can't accidentally "fall" out of the wall, and if someone runs into the wire, that someone is going to fall over before the connector comes out. That probably has a lot more value on a liver performance stage than in a theater room, but it is still a plus.

Ernie

First, thanks for the lesson LF, seems you know more than the average electrician! Certainly in my area.
Second, Joe the video can be as important as the sound. If the guy spent the $ for Krell he can be convinced of the merit of a scaler. Sources (especially cable) can look like shit next to 480i 0r 480p(depending on your DVD) and the scaler built into most DLP's can vary too much. Using a outboard scaler you can "balance" your sources and your projector ( it also works well on Plasmas ). You simply run a 15 pin cable from the projector to your rack and you have a similar result as "balancing" your speakers and sub using XLR cables.

It can be added ( provided you ran the cable) later but I suggest talking to your client before hand so he get's the idea and you can demo it to him.

Just a thought,

Twix

nice system

Me, again. I recently "won" this on eBay. It's a 25' cable that sounds like exactly what you're asking about. It's for the projector I just bought. It will connect the output of my quadrupler to the RGB inputs on the projector. I don't know where to look, other than here, but they're not cheap, especially the longer lengths.

By the way, Ernie, I've never seen a liver perform onstage, but it sounds like an 'organ' recital I once attended. (Sorry, couldn't resist!)

Larry
www.fineelectricco.com


This message was edited by Larry Fine on 09/27/02 18:59.07.

Another location for that same cable is www.markertek.com. They've got lengths from 6ft-25ft with prices from $55-$83.

I don't know how that relates to what Larry suggested.

SamG

SamG