I recently bought a new house that is currently being built. I took the speaker pre-wiring option and had speaker wire run for the surrounds and the subwoofer. The subcontractor used 16-gauge wire for all the speakers.

I was planning to put an RCA connector on the subwoofer wire for the LFE input, but I've been hearing that doing so might cause hum on the line. Is this true? If so, is there any way I can use the in-wall wiring?

Thanks!

I don't understand. usually the Hum is a 60hz hum and it is from a power source. Usually something plugged in backwards or interferance.

Adding a connector to insulated wire will not cause a hum. The hum you get will be caused by something else, the wire is just delivering it to the speaker.

quote:<HR>Originally posted by vlad:
I don't understand. usually the Hum is a 60hz hum and it is from a power source. Usually something plugged in backwards or interferance.

Adding a connector to insulated wire will not cause a hum. The hum you get will be caused by something else, the wire is just delivering it to the speaker.<HR>

Sorry, I didn't make myself clear. What I meant was I was told that using regular 16 gauge wire will definitely cause the hum. Or is it possible that I will be OK with this pre-wiring?

I might be misunderstanding you, but I think you mean that you're going to put an RCA connector on the end of your speaker wire. This will work just fine as long as you keep the speaker wire from running parallel to any power lines. As a general rule keep signal cables away from power cables, and if you have to cross their paths do it at a right angle. This will minimize the interacting of their respective magnetic fields and you shouldn't get any "hum". Hope that helps.

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People say nothing is forever. If that's true how do you explain herpes or the Greatful Dead. I say forever is for people who got the balls to make it last.

Hmmm, pre-wiring option???...are all the wiring will be running hidden underneath the floor???....here's my 2 cents suggestion, may save yourself trouble later on....

For your subwoofer, get a subwoofer cable. AR and Monster Cable make them. Ofcourse, you don't have to buy from either brands (since they are a bit pricey), if you can find another brand selling them for cheaper. Just make sure they are of good quality.

Now, for speaker's wires....Get 12gauge for your main front and center speakers, and 10gauge or even 8gauge speaker wire for your surround speakers(depend how far your surrounds are from your receiver). The bigger the wire the less resistance they are, and make sure they are of quality speaker wires(like Monster speaker wires). Now for explaination in choosing your wires...If you look at the end of the Monster speaker wire(note i'm only use Monster speaker wire as an easy example, since they are widely available...you don't have to get these, if you can find similar quality wire for less) they have very fine and thin copper strands, unlike other cheaply made speaker wire that have very thick copper strands. The thicker copper strand will have more air space in between when they wrapped and twisted them together. Speaker wire like the Monster have thinner copper strands, that means They are higher density. Higher density = broader sound spectrum can carry through your wire = richer sound quality to your speakers.
Hope this help.

I will try to reduce some confusion about the causes of subwoofer hum.

When you are connecting a receiver output to a powered subwoofer, you need to know whether the output is at line level or preamp level. Line level is the kind of signal that conventionally goes directly to speakers, while preamp level conventionally goes to a power amplifier before going to the speaker. The powered subwoofer is a unique type of speaker in that it is often fed by a preamp level signal.

When connecting a receiver (subwoofer) preamp level output to a powered subwoofer, do not use "regular" double stranded speaker wire (Bi-wire)! Instead, use coaxially shielded (monaural) subwoofer cable.

Although this type of cable is considerably more expensive than "speaker wire", it is necessary to prevent the pickup of 60 cycle (electromagnetic) noise from the house wiring (the electric wires in the walls) which will sound like "hum" coming from your subwoofer.

Explanation: Preamp level signals are much weaker than line level signals. While a small amount of 60 cycle pickup is very difficult to notice in comparison to line level signals, a small amount of 60 cycle pickup can be very annoying after it is amplified in the powered subwoofer! The audio cable is especially susceptable to such pickup if there is a long distance between the amplifier and the powered subwoofer.

Some checks:

1) Try powering "on" the subwoofer with no signal cables connected. Turn the subwoofer gain way up, if necessary. If there is hum, the cause is internal to the subwoofer. It is conceivable that reversing the power plug in the outlet could reduce this hum (but I do not believe it), try it. If the hum remains you need to repair or replace the powered subwoofer.

2) Next, with no hum coming from the powered subwoofer, attach the audio signal cable to the subwoofer input. Leave the other end of this cable not connected to anything (open). If the hum appears (as it will if you are using "speaker wire" for the cable) then you are hearing the sound of the AC power that is coupling into the audio cable!
Replace the cable with shielded coax. (If you need convincing before spending a lot of money on the shielded cable, first try this test with a short length of coax: Connect the shielded cable to the subwoofer in place of the original cable, leaving the other end open. You will hear no hum. Now, without touching the shield-metal of the new cable, touch your finger to the center pin on the open end of the coax. The hum comes back because your body (like the speaker wires) also picks up the AC, and your finger now allows this pickup to reach the center wire of the coax and reach the subwoofer input.

Now, go back and exchange the coax for the length you need to reach from the subwoofer the receiver.

3) Ground Loops?: It is possible that when you connect the coax cable to the subwoofer (preamp level) output on the receiver and turn "on" the receiver, you may hear some hum.

There is much dialog about "ground loops" available on-line and the subject is pretty complex.

Some Basic Theory: Your receiver puts out a "clean" signal (with no hum in it). This signal is a voltage between the center and outer (RCA) contacts of your receiver output. You want to cause the voltage at the subwoofer input to be exactly the same as at the receiver output. This will not happen if the cable conductors are exposed to AC signals in the enviroment; but the enviromental signals cannot penetrate the shielding of a coax cable.

When you use coax, the metal shield causes the voltage on the outer contact of the receiver connector to be (virtually) the same as that on the outer contact of the subwoofer connector. Similarly, the voltage on the center contact of both also remains the same. Thus, you have made an ideal connection!

However, there can still be a problem within the receiver or subwoofer. Ideally, the receiver and subwoofer should be designed to reject any changes in "shield" (ground) voltage. If the rejection (filtering) works, then pickup in the shield (ground voltage) is balanced (by the unit) on the center contact so that the difference in voltage between the shield and center contacts is unchanged by the pickup (or any other "noise" in the ground terminal). If this rejection is inadequate, differences in the way each unit is "grounded" (ground loop) can produce an audible hum. Reversing the power plug on either unit (receiver and subwoofer) can affect the level of this hum. Powering both units from the same outlet will ensure that both grounds are in the same phase (the best scenario). Hum from a "ground loop" can be affected by how much AC power is flowing in the same AC circuit as the receiver or subwoofer, (i.e., if the washing maching turns "on", this hum can increase); and the problem is "custom" to how your house is wired, and what appliances are connected where!

Perhaps, the easiest remedy is to find a coax cable that has an "extra" wire attached to the shield with which you can "ground" the shield to the chassis of the receiver. If you can also ground the receiver chassis to a more "ideal" place than the AC power, e.g., the metal water pipes, the "loop hum" should go away. (Ideally, a ground should be so robust that its voltage will not change, no matter how much current flows into it. A coax shield, so grounded, will not pickup environmental electromagnetic noise, no matter how strong it is.

Good luck with this.

Hummm...well I don't want this to turn into yet another "Monster Bash" thread but.....

Personally, I would never, ever buy Monster. While in general nothing wrong with it, it is all about marketing. But something else, anything else. I did buy some AR on a lark and seems pretty well made and in fact surprised that some Best Buys are now stock some of the AR.

As for a dedicated sub woofer cable...I just grabbed a high quality RG6 cable and put two decent screw in F to RCA adapters. So far works great! I had a dedicated sub cable in my old system but it wasn't long enough for my media room. I can't really compare the two as my old system had a different sub. Oh my media room system sounds a ton better, but it has a better sub and I have spent more time in set up.

I'd also be careful about getting something a thick as 8 guage speaker wire. I doubt my speakers could handle something that thick as bare wire. I had trouble getting my Kimber Kable TC4 in my speakers. At least test it before buying a bunch if you are planning bare wire connections.

Bingo!!! We have a winner!!! Monster cable is NO better than using quad-shield RG-6 and the F to RCA adapters. Save the extra $$$ for DVD's!

Sonic

Thanks, but you better give any prize for being a winner to X. He was the one that suggested using RG-6 to me for when I needed a long run of component cables (from my equipment to my ceiling mounted PJ). That worked so well for me, I used the idea for my sub as well.