2. cables
  3. 175151-164950

Another Subwoofer Cable Topic

Sorry folks, I cannot find a reasonable answer to this quandary and not many people are willing to answer it properly.

Powered subwoofers seem to enjoy having a left and right RCA input, despite the driver being 100% mono. Practically all manuals say the same thing, choose one of the RCA inputs (usually Right) and everything will be fine.  I have not found this to be true.

Somewhere, in the annals of the internet(s) I had found an audio discussion where someone explained it. On a basic level, the mono driver requires 2 incoming volts to properly drive. One single RCA output delivers 1 volt of signal. Using that one input will cause the driver to activate and make bass, this is true.  But using both RCA inputs doubles the voltage and the driver functions much better.

In my floor standing system I have two subwoofers that both use NHT monoblock amps. They both have left/right input RCAs. When I connected a SINGLE connection to the block, I had to crank the volume to the maximum to get any reasonable bass out of the subwoofers.  At that time I bought a splitter so that the single LFE out on the receiver (I have left and right LFE outputs, hence two subs) could split into two to cover both left/right inputs and suddenly there was more bass than could possibly be endured and I had to crank the volume way down. So, that seems to prove the theory that using one single RCA input is not correct.

So, on to my quandary.

In my office reference system I have a powered sub that currently connects via two RCA.  The sound quality is pleasant and enjoyable. I wouldn't mind tightening the bass down a bit more. To that end I want to switch to actual Subwoofer cables, that have been specifically tuned to amplify bass. The question is, should I buy two subwoofer cables or buy one cable and two splitters?  Yes, buying two cables is more expensive.  However, ANYTIME you split a signal, there *WILL* be signal quality loss.  That's just the way it is. The more point to point the connection is, the better the signal flow. So...has anyone actually tested whether two sub cables works better or the same as a single sub cable split?

 

128x128guakus
audioman58's avatar
audioman58
3,896 posts
 

Rel work more direct line level ,direct from the amplifiers audio output signal.

knighttodd
197 posts
 

From what I understand is if you have a sub out on your AV amp or pre amp you need only one run going to the life on sub. If you run separate  pre and amplifier then two runs are required  from left and right.  As far as splitting one run to two I don't know.  If it increases the output  and sounds like bass then do it.

socalml528's avatar
socalml528
121 posts
 

Apologies if not reading your question correctly; I'm using two subs.  My IA has left and right sub RCA outputs. Each sub has L and R RCA inputs.  I'm simply running the L IA output to the L input on one sub and the R IA output to the R input on the other sub.  My sub RCA cables are Audioquest BlackLab.

No problem with volume or realistic bass, only challenge was getting cross-over and level just right for the room and intended effect.

IA = McIntosh MA352

Subs = Martin Logan Dynamo 400s

lordrootman's avatar
lordrootman
359 posts
 

I’m pasting this for you to read it will answer your questions 

 

Quote:

Using a Y adapter on most, but not all, subwoofers will increase the sound level from 3 to 6 db.

Aperion Audio Subwoofer Y Cable
"Why, oh why do you need a subwoofer Y cable? Most AV receivers come with a single sub output while most powered subwoofers come equipped with left & right inputs. By using a subwoofer Y cable for both the left and right subwoofer input, you can increase the bass output of your subwoofer by about 3dB."

HDMI cable for home theater and high-performace audio video cables.
"Attach this cable to an existing subwoofer cable to split the signal into two inputs. 
Instantly improves your home theater or home audio experience.
Many subwoofers have increased clarity and bass response when both inputs are fed with a mono signal."

Wye Y Cable
"Typically, powered subwoofers will come equipped with either a single RCA connector, or double RCA connectors. However, both connections typically only require a mono (single) connection. Therefore, if you have both right and left inputs, a single cable connected to the "left" input will probably work just fine. However, you can get anywhere from a 3dB to 10 dB gain from your subwoofer by plugging into both stereo inputs. To plug into both inputs with a single cable, simply purchase our Y adapter Cable along with your subwoofer cable."

This is the science behind it:

There are two formulas used to find the db ratio between sound levels.

The first is used ONLY FOR POWER (watts): 10 . log (P2/P1). This formula is used when comparing Sound Intensity, measured in watts.

The second is used ONLY FOR VOLTAGES (and SPL levels): 20 . log (V2/V1). This formula is for voltage relationships and Sound Pressure Levels.  

Using a Y adapter will add two correlated signals. When you sum two equal correlated audio signals (i.e., mono sources from sub output on the receiver/preamp), you will get twice the signal level (A1 + A2 = 2A1, since A1=A2).

Therefore , since V2 = 2 V1 and the log (2) = 0.30103, it follows

20 . log (2V1/V1) = 20 . log (2) = 6dB gain in voltage.

For power, it will be 

10. log (2P1/P1) = 10 . log (2) = 3dB increase in power.

These are a few advantages (some real and some claimed) to using a Y adapter:

  • If you leave one of the RCA inputs open, dirt may get in there.
  • Using a Y adapter may add a few dbs to the subwoofers's output.
  • Some claim that the subwoofer works better at lower levels with the Y-cable.
  • The auto-off mode of some older subwoofers (e.g, Velodyne CH-12) may not come on at lower levels without the use of a Y-cable.
  • Some older subwoofers may actually need a Y cable because the left channel L may not default to mono signal.
  • Another benefit of using a Y-cable at the sub input jacks may be for reducing the amount of Radio Frequency (RF) and Electomagnetic (EM) interference, because you are not leaving the other input open and active. Subwoofers can be affected by annoying buzzes and hums.

Conclusion: Since Y adapters cost a few dollars and there is no significant risk involved, I would recommend using a Y adapter (2 male, 1 female) at the subwoofer's RCA input jacks. Make sure you use a good quality Y adapter that is shielded. Otherwise, you may hear hum and noises. 

lordrootman's avatar
lordrootman
359 posts
 

If you want to read more here’s the link 

 

https://forum.blu-ray.com/showthread.php?t=95817

 

 

 

More to discover