Expert: Antonio Delgado - 2/1/2007

Question
I want to run a line level cable about 50 to 60 feet from my A/V controller to my sub woofer.  Would this length be a problem to carry the signal?

Answer
If you are planning to run a line cable (shielded cable) I should assume you have a powered subwoofer (a subwoofer that has a built-on amplifier).  If not, you will need a speaker cable (non-shielded cable).  Either being the case, 50 to 60 ft is okay as long as the gauge of the cable is appropriate.  

Keep in mind, the longer the cable the higher the resistance value, therefore, a lower output voltage.
Note:  Line signal tends to be in the mV (millivolt = no more than 500mvolts) range on most standard devices and products.  Having a very long cable with a very small gauge will increase your overall resistance at the load (subwoofer), thereby minimizing your overall output amplitude (volume at the subwoofer at this point).

In short, there will always be some loss of signal due to the amount of distance.  The loss at the load is very minimal if you have a standard (16-22 AWG) or a thick (under 14 AWG) cable.  The key is to shoot for a standard gauge at minimal for such an application and of course all dependent on amplification, cable gauge and distance factors.  If this is for a residential environment, most amplifiers range in a minimal scale (40 to 200 watts for subwoofers).  If this is the case, a 14 to 20 gauge cable would do the trick without getting too technical.  I put together the following table to give you an idea of the amount of signal loss prior to reaching the load.  



       (50 watts)(100 watts)(150 watts)

24 AWG                
50ft line   -0.05   -0.09   -0.14   
               
22 AWG               
50ft line   -0.03   -0.06   -0.09   
               
20 AWG               
50ft line   -0.02   -0.04   -0.05   
               
18 AWG               
50ft line   -0.01   -0.02   -0.03   
               
16 AWG               
50ft line   -0.01   -0.01   -0.02   
               
14 AWG               
50ft line   0   -0.1   -0.01   


These days, companies are manufacturing cables with higher shielding ratios.  The higher the shielding ratio for a line cable the better suspectability to interference factors.