This is a question for you audio engineers.

I use a Yamaha MG102c mixer to disperse audio from my live keyboard rig.  I am looking for an output source to experiment with a sub woofer.

The Main, Monitor, and Aux. outputs are already being used.  What I have available are stereo unbalanced RCA outputs labeled REC OUT.  The mixer manual states that they send “...the same signal that is being output via the STEREO OUT jacks”.
Since the sub woofer I want to utilize also has stereo unbalanced RCA connections for line inputs (these are summed by the sub amp), it would be simple for me to send this signal to the sub (BTW, the sub woofer is set up to receive full-spectrum frequency input which it then filters for low-pass).

Will this signal work for this application?  The specifications for the other mixer outputs mentioned are uniformly: Impedance=150 and nominal level=+4dBu.  The REC OUT jacks, however, are rated as: Impedance=600 and nominal level=-10dBV.  What is -10dBV, and why is the nominal level for these outputs not stated as dBu like the others?

Beyond just stating whether or not this output signal is appropriate for use with a powered sub woofer, any additional information to help me understand the real world difference between these very differently rated mixer signal outputs and why they are so different is appreciated.

Not appropriate for the XF forum heading…

The use of dBV and dBu are because the outputs you mentioned use two difference references for calibrating zero. The low impedance +4dBu uses a reference of 0dBu = 0.775Volts
While mid impedance RCA (consumer) uses 0dBV = 1.000Volts.

They are simply difference calibration references. The Rec Out is typically to go to a consumer recording device… So if that input on the subwoofer is looking for a typical tape or hand held playback device this should work extremely well.

Line level for consumer gear is -10
Line level for pro gear is +4

They are both considered line level just two different calibration references are used.

cmayhle - 06 October 2012 03:53 PM

[...]Will this signal work for this application?  The specifications for the other mixer outputs mentioned are uniformly: Impedance=150 and nominal level=+4dBu.  The REC OUT jacks, however, are rated as: Impedance=600 and nominal level=-10dBV. [...]

The signal at the REC OUT jacks will be fine as long as the sub woofer amp has enough gain to work with the level it will be fed. It’s likely there will be no problem, but do you have specs for the input drive requirement for the sub?

Decent coverage of the general topic:
http://en.wikipedia.org/wiki/Decibel

Thanks Bad_Mister and 5pinDin for the information.  I’ve never even looked in this Forum, guess I should get out more...!

5pinDIN, I don’t have specifications for the sub inputs, which might have given me some additional clues, but I believe my question(s) have been answered.

Since the sub woofer I want to utilize also has stereo unbalanced RCA connections for line inputs (these are summed by the sub amp), it would be simple for me to send this signal to the sub (BTW, the sub woofer is set up to receive full-spectrum frequency input which it then filters for low-pass).

Since you say the sub woofer has a stereo unbalanced RCA connection for line input, I’d bet dollars against donuts it is designed for consumer devices and therefore the signal you are sending is exactly what it is looking for