Sub new wiring help

[bigbossbarton]

Ok, Im having a issue with a new house i moved into and pre wired subwoofer system.

I have a denon receiver and a velodyne sub.

The devon receiver has a sub out single coaxle and the velodyne sub takes that just fine with the LFE in. But i now want to use the sub with the pre wiring so it won't be right next to my tv in the way. So my problem is this...

The house is wired with one cable and inside that one cable is 4 smaller cables (red,black,white,green) how do i hook the sub up when my denon receiver only has the single coaxle out?

I tried to buy a single coaxle out today. Only used the red and black wires and soldered them on. solder job was done correctly but when plugged in the sub it had really bad and loud feedback. I then tried to wire the sub with the red and black in the speaker level input that it had, i got no feedback but was so low it barley made a sound with a tone test done.

Im really stumped. I keep reading the old ways of running the two front speakers in parallel to the sub but was wondering if there was a better way. If not and i do need to run them in parallel then do i run both front left and right to the speaker level inputs? Would it be loud enough?

Thanks in advance for any help.

 

[Adam]

Welcome to the forum!

I'm guessing that you're trying to use in-wall speaker wire for this, and if so, this sounds like a fairly common issue that people run into. Some comments based on that assumption:

1. If you did make the solder connections correctly, then you're likely experiencing the hum that's caused by not having shielded wire. The low-power signals that are sent over the coax connection between the receiver and the sub are susceptible to interference from other electrical signals, such as electric power lines. Therefore, those cables have an electrical shield around the central conductive core. Speaker wires don't have that because the power going through them is high enough that the interference typically isn't noticeable. When you tried to use two speaker wires (one as the conductor, one as the shield) for the coax, it's not the same as a regular coax. If there wasn't any interference, it would have worked (and it does for some people).
2. If you're unsure if the coax connections were made correctly, you could get two of these cables from Radio Shack (or similar cables somewhere else) to try that connection one more time.
3. When trying out the speaker-level connections to the sub, make sure that the crossover frequency selector on the sub itself is set pretty high so that the sub isn't filtering out the sound (just to check this out - you'd set that frequency properly once you're done troubleshooting).
4. To run speaker-level connections to the sub, you would run both the left and right front speaker connections from the receiver to the sub's speaker-level inputs, then from the sub's speaker-level outputs to the front left and right speakers. So, you'd actually need eight wires in the wall, not just four.
5. Outside of trying to use the in-wall speaker wires, you can get a wireless system such as the Soundcast Subcast (about $160 at Amazon). Certainly not inexpensive, but it's an option for locating your sub away from your receiver without running wires across the floor.

 

[bigbossbarton]

Adam:
With step 2 are those coax cables ok quality for a sub? Will i get feedback because of the cheapness of the cable? Im gonna try it later today.

Thanks

 

[Adam]

Hi. I don't think that you'll get feedback because of the build quality of those cables. They should help you troubleshoot the issue. Just make sure to keep power cords away from them while you're checking because they aren't shielded.