Pre-wired Connections Are Confusing and Don't Seem to Work Properly

[Dasen Luo]

The basement of my home is pre-wired for a 7-channel home theater system. The bundle of speaker wires to be connected to the receiver include a coaxial cable for the subwoofer, two 2-conductor wires seemingly for the two front speakers, and two 4-conductor wires that I assume are for the surround back-left and back-right and the surround left and right speakers. There are 7 junction boxes on the wall and on the ceiling. I have made successful connections between the two 2-conductor wires in the bundle and the two front speakers. I have not tried the connection for the subwoofer yet, but one of the junction boxes on the front wall has a coaxial cable coming out that apparently matches its counterpart in the receiver bundle. So far so good for the connections with the three junction boxes on the front wall (i.e., the two front speakers and the subwoofer), but my confusion starts from this point on.


The junction box on the back-right of the ceiling has a 4-conductor wire coming out, and I connected them to both the surround back left and surround back right speakers and tested one of the 4-conductor wires in the receiver bundle. Both speakers played. However, the wire coming out of the junction box of the back-left of the ceiling is a 2-conductor wire, and I don't have any 2-conductor wire left in the bundle for the receiver that can be used to connect to this junction box. I have near-zero knowledge about the pre-wiring setup, so I have made an effort to learn abut this online. I read somewhere that pre-wiring professionals often start with one 4-condutor wire and then split it into two 2-conductor wires at the other ends for two separate speakers. My confusion is twofold: (1) The wire coming out of the junction box for the surround back-right is not a 2-conductor wire, but a 4-conductor wire that makes both speakers play. (2) The 2-conductor wire coming out of the surround back-left junction box, when connected to the surround back-left speaker, does not activate the speaker. I tried these connections both by using a battery and by the actual receiver playing the sound.


The situation for the two junction boxes designed for the surround left and right speakers are analogous, and I assume the answer to my questions above should also apply to these two junction boxes.


Am I missing anything here? What should I do to make the connection through the surround back-left junction box, which has a 2-conductor wire coming out, work?

 

[WaynePflughaupt]

If the contractor used a 4-conductor cable for the back speakers, it would not be unusual for one of the junction boxes to have the 4-conductor wire coming in, with a 2-conductor cable spliced into two of the wires that would jump over to the other junction box.

It sounds like the contractor didn’t follow through with the proper wiring protocol to get the cable over to the second box.

You should get a wire tracer / tone generator like this. Connecting the tone generator to the wires will generate a strong audible signal that the probe can pick up. This will give you an idea where the mystery two-conductor wires are going.

If you can trace the route of the two-conductor cable, you may very well end up having to remove the boxes with the 4-conductor wires in order to locate the cable splice it in.

Regards,
Wayne A. Pflughaupt

 

[Dasen Luo]

Thanks, Wayne! I bought a Sperry et64220 wire tracker wire tracer from Home Depot and set out to do what you suggested about the curious 2-conductor wire coming out of the surround back-left junction box. I connected the alligator clips of the tracer to the 2-conductor wire and started tracing. As a first-time user of the device, my usage of the tracer is naturally clumsy. I seem to hear beeps when I move the probe in a wide range around the connected junction box. Although I believe I have heard stronger signals along the path from the surround back-left box to the surround back-right box, I am not fully sure, because it could be my predisposition that have misled me to hear things this way. Of course, this is most likely to be my problem, and I probably will try to find a more experienced user of the tracer to help me with this. I’ll update this thread after I have more definitive info from my tracer.

 

[WaynePflughaupt]

A stronger signal is definitely what you’re looking for. Move out a couple of feet from the box, and then moved the probe in a circle around the box. The place where the signal is loudest will show the direction the cable is going. From there, it should be fairly easy to follow.

Regards,
Wayne A. Pflughaupt

 

[Dasen Luo]

Thanks again, Wayne! Following your instruction for using the tracer, I am now more certain that the 2-conductor wire out of the surround back-left box does go near where the surround back-right box and the 4-conductor wire are. What should be my option now?

 

[highfigh]

If the signal needs to be stronger, disconnect one lead from the speaker wire and connect it to something else that's metallic (I have used the metal brace on my fiberglass ladder), but not necessarily grounded (it could be grounded, though). You'll want to set the volume control lower because the signal may bleed into other cables.

These junction boxes- are they the typical ones used by electricians? If they're nailed to joists and studs, you can use a hacksaw blade holder to cut the nails and remove them, to see what's behind. If you need to reinstall them, you can screw through the box and into the wood- it's OK to do this with low voltage boxes but going by the electrical code, it's a violation.

Blade holder-

https://www.target.com/p/stanley-174-6-fatmax-174-multi-saw-with-cushion-grip-20-220t/-/A-14790626?ref=tgt_adv_XS000000&AFID=google_pla_df&CPNG=PLA_Home+Improvement+Shopping&adgroup=SC_Home+Improvement&LID=700000001170770pgs&network=g&device=c&location=9051983&gclid=CjwKCAjwoNrMBRB4EiwA_ODYv97d9DZQTpGEc2XWfg0ZC9qYNCk-abT1vpOaUyKrFeN1JUIIAZH01RoCSRoQAvD_BwE&gclsrc=aw.ds

 

[WaynePflughaupt]

What should be my option now?

It looks like they ran the wire but didn’t get it in the box? May appear to be shabby workmanship on the wiring contractor’s part, but more likely it was the sheetrockers who came behind them who screwed things up.

Regardless, your only option is to remove the box that has the 4-conductor cable in it. As highfigh mentioned, they are typically nailed to the side of a stud. The tool he linked will work; my preference is a sawzall with a metal blade – it’ll take more time to situate the blade between the box and the stud than to actually cut the nail.

Once the box is cut out, you should be able to reach your hand in the hole and find the two-conductor cable. Hopefully there is enough slack to make the connections you’ll need. If not, you can use the old cable to pull in a new one the proper length (assuming the old one isn’t secured with staples or something). Just be sure and use a CL-2 or -3 cable rated for in-wall use. You can use a so-called "old work box" to replace the box you removed.

Regards,
Wayne A. Pflughaupt

 

[Dasen Luo]

I was out of town for the last few days and was not able to follow the thread during these days. Thanks for the replies from both highfigh and Wayne! Attached are two photos of the junction boxes, one showing the 2-conductor wire coming out, and the other showing the two junction boxes in question, with the right one in this photo having a 4-conductor wire coming out. Are they the kind of junction boxes you referred to in your replies?

Thanks!

Dasen Luo

 

[WaynePflughaupt]

That’s not a junction box. It’s just a hole in the drywall with a cover over it. If you want to see what a junction box is, remove the cover from a light switch.

So – the good news is you don’t have to worry about cutting an existing junction box off the stud (or rafter in this case). However, you do need to cut a hole in the ceiling in order to get your hand in to find the missing wire.

If you’re confident from the signal tracer that the missing wire is indeed in the ceiling, then go ahead and cut the holes for your ceiling speakers. Those are typically pretty big holes, so you’ll probably be able to see the missing wire and pull it out.

If you’re less confident about the presence of the missing wire, you can take a more cautious approach by cutting a hole that you can easily cover. Get a so-called “old work box” from your local hardware store. It should come with a pattern that you can trace around on the ceiling, which will mark the hole you'll cut. You’ll need a hand saw to cut the hole in the drywall. The hole won’t be big, but it will be big enough to get your hand through (unless yours are unusually large). You’ll want to do this on the side where the four conductor wire is.

If it all goes south and you can’t snag the wire, the blank cover you took down will bolt to the old work box, and things will look like they do now (or at least like they were before you took the covers off).

Here’s a guide on installing old work boxes. You can also get information in the first two posts of my instructional piece on in-wall wiring, which you can find in my signature.

http://www.hammerzone.com/archives/elect/remodel1/lighting/track2ft/oldworkbox.htm

Regards,
Wayne A. Pflughaupt

 

[Dasen Luo]

Thanks for clarifying my misconception about junction boxes. Please pardon me for being slow to follow your suggestion, as you can apparently see that I have had near zero knowledge about this type of things. You suggested that I cut larger holes to take out the possible missing wire. Did you mean that I cut a larger hole around where the surround back-left speaker should be (with the 2-conductor wire) and another larger hole around where the surround back-right speaker should be (with the 4-conductor wire) to take out a possible missing wire? What kind of missing wire should I look for?

 

[highfigh]

I was out of town for the last few days and was not able to follow the thread during these days. Thanks for the replies from both highfigh and Wayne! Attached are two photos of the junction boxes, one showing the 2-conductor wire coming out, and the other showing the two junction boxes in question, with the right one in this photo having a 4-conductor wire coming out. Are they the kind of junction boxes you referred to in your replies?

Thanks!

Dasen Luo

If these are the only two wires in the area for two speakers, they may have poked the holes at the intended speaker location, so you'll need to determine the position of the holes in relation to the ceiling joists (in order to make sure the speakers will fit between the framing). If you have a piece of stiff wire (a wire coat hanger is good for this), take a straight piece that's about 18" long and bend it about 6" from the end. Poke it through the hole and rotate it- if it rotates freely, you can use the small hole as the center for the speaker hole. If it stops, determine the approximate angle of rotation or poke it in at an angle where it can't rotate and find the distance to the closest joist before centering the pattern for the speaker hole. You can also bend the wire into a curve and insert it in the hole, to poke around and find the distance to the framing.

My guess is that they used the wires to mark each spot for the drywallers, then let the speaker installer cut the hole and make the connections. The four wire cable is probably coming from the head end and the two wire goes from the area of the four wire cable to the hole for the two wire. You would cut the speaker holes, use the White/Green (usually connected to the Left channel) wires for one speaker and Red/Black (usually Right channel) for the other. The unused pair at the end of the four wire connects to the two wire cable.

Using one four conductor to the general area and a two conductor to the second speaker is OK if the configuration won't change. If you decide that you want more than 5.1 or more speakers in that ceiling, you'll need to run more wires and that won't be easy unless the joists run in your favor and you have a closet on the backside of the wall where the cables can be fed.

 

[Dasen Luo]

Thanks, highfigh! My initial plan of installing the speakers is:

(1) Make sure that the pre-wired 7-channel connections work properly.

(2) Install ceiling mounts for speakers such as those listed by the link https://www.crutchfield.com/g_15830/Speaker-Wall-Mounts.html?tp=586#&nvpair=FFBrand|Pinpoint



I am stuck at (1) at present. Please advise whether my thoughts now are on the right track. I will simply cut a larger hole around the surround back-right wire (4-conductor) that has been tested to work for both the surround back-right and the surround back-left speakers and try to find the head of the 2-conductor wire there leading to the surround back-left hole. Once the head of the 2-conductor wire is found, I will connect the head of the 2-conductor wire to its counterpart in the 4-conductor wire so that the speaker at the surround back-left hole will work too.



I know professionals may also frown upon (2) of my plan, but as a person who is not the most handy in the world and not that knowledgeable about home theater setup either, I hope the plan is still in my capacity and will at least work for my Onkyo speakers.

 

[highfigh]

Thanks, highfigh! My initial plan of installing the speakers is:

(1) Make sure that the pre-wired 7-channel connections work properly.

(2) Install ceiling mounts for speakers such as those listed by the link https://www.crutchfield.com/g_15830/Speaker-Wall-Mounts.html?tp=586#&nvpair=FFBrand|Pinpoint

I am stuck at (1) at present. Please advise whether my thoughts now are on the right track. I will simply cut a larger hole around the surround back-right wire (4-conductor) that has been tested to work for both the surround back-right and the surround back-left speakers and try to find the head of the 2-conductor wire there leading to the surround back-left hole. Once the head of the 2-conductor wire is found, I will connect the head of the 2-conductor wire to its counterpart in the 4-conductor wire so that the speaker at the surround back-left hole will work too.



I know professionals may also frown upon (2) of my plan, but as a person who is not the most handy in the world and not that knowledgeable about home theater setup either, I hope the plan is still in my capacity and will at least work for my Onkyo speakers.

I don't know your location, but if you want to avoid cutting overly large holes, you could get one of these-

https://www.walmart.com/ip/Waterproof-HD-5M-7mm-Endoscope-Lens-Mini-USB-Inspection-Camera-with-6-LED-Lights-Borescope-for-Android-Smartphone-PC-Laptop/873783136?wmlspartner=wlpa&selectedSellerId=9869&adid=22222222227079579609&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=192115778316&wl4=aud-310687322322:pla-356277657047&wl5=9052028&wl6=&wl7=&wl8=&wl9=pla&wl10=115780161&wl11=online&wl12=873783136&wl13=&veh=sem

They're available for use with an iPhone, too.

 

[WaynePflughaupt]

That bracket you’re looking at is for wall mounting. If you use it for the ceiling you MUST make sure it attaches to a rafter. It will NOT support a speaker if it is only mounted in sheetrock.

Regards,
Wayne A. Pflughaupt

 

[Dasen Luo]

Highfigh, thanks for recommending the scope tool! It seems to be a tool I do need.

Wayne, thanks for your warning about the use of the ceiling mount.

The whole thing sounds a bit more than I can handle all by myself. I probably should find someone more experienced to help me.

 

[panteragstk]

I don't know your location, but if you want to avoid cutting overly large holes, you could get one of these-

https://www.walmart.com/ip/Waterproof-HD-5M-7mm-Endoscope-Lens-Mini-USB-Inspection-Camera-with-6-LED-Lights-Borescope-for-Android-Smartphone-PC-Laptop/873783136?wmlspartner=wlpa&selectedSellerId=9869&adid=22222222227079579609&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=192115778316&wl4=aud-310687322322:pla-356277657047&wl5=9052028&wl6=&wl7=&wl8=&wl9=pla&wl10=115780161&wl11=online&wl12=873783136&wl13=&veh=sem

They're available for use with an iPhone, too.

I have no reason to get it, but I want that camera too. Sweet.

 

[highfigh]

That bracket you’re looking at is for wall mounting. If you use it for the ceiling you MUST make sure it attaches to a rafter. It will NOT support a speaker if it is only mounted in sheetrock.

Regards,
Wayne A. Pflughaupt

Unless the speakers aren't heavy and toggler/Molly bolts are used.

 

[Dasen Luo]

Thanks, highfigh! The speakers aren't that heavy (a couple of pounds each), and the CrutchField sales person said the mounts should work for my speakers (of course he would say so). However, for the peace of mind, I'll see whether I can mount them on something firm.

 

[Dasen Luo]

Because I am commuting between two distant states, I have not had a chance to attend to the home theater problem since last summer. I want to pick up what I left off last summer and see whether I can continue to learn how to solve the problem.
As I described in my previous posts, I was particularly confused by the setup of the wires coming out of the holes designated for the surround-back-left and surround-back-right speakers. Two wires are found in the hole for the surround-back-right speaker and each wire can be connected to a speaker. Both speakers play when the counterpart wires at the other end are connected to the surround-back-left and -right jacks of the receiver. However, none of the wires at the other end can make the speaker play when the speaker is connected to the wire coming out of the hole for the surround-back-right speaker.
I texted the contractor who initially setup the prewiring for me yesterday and asked whether he could help clarify the confusion for me as one of his customers. Following are the text message exchanges between us.
I first described the problem that has confused me, hoping that he could clarify the problem for me
Contractor: “Did you function the wires?”
I: “Thanks for your prompt reply, but how do I function wires?”
Contractor: “Wire nut the wires together.”
I: “Do you mean that I need to connect certain wires together? Which wires do I need to “nut” together?”
I got no more answer from the contractor.
Any idea what the contractor could have meant by his messages?
Thanks in advance.

 

[Kevin S]

This is how it should be if your contractor did it the way you say.It might not be drawn the exact way,but you get the idea.Sounds like the 2 wire jumper might be missing or up in the ceiling somewhere.Your contractor meant "Junction" not function the wires/splice at each 4 wire location to separate them into 2 wire.