Speaker Hook-Up Problems

[Jacb Robinson]

I hope I am missing a simple and obvious solution to this because I am tired of mind wrestling it over and over. Here is what I am trying to do:
I bought a Behringer B205d personal monitor speaker, just web search B205d for specs (for the sake of time, we'll leave my choice of products out of the equation, I know Behringer is probably not a favorite of too many members here) and I want to use it as a keyboardist/P&W Leader monitor. This way She can have control over the keyboard volume and vocal mix without affecting the other floor wedges. I only have two AUX sends so I can't dedicate a send to the B205d alone so I am trying to send the same signal to the B205d as to the amps that feed the other wedges.

*Note the stage box where our snake terminates has both a 1/4" and XLR jack for each send (I would think that the 1/4" jack is TRS balanced, but not positive). The problem here is that if I plug something into the 1/4" it cuts the signal to the XLR using both jacks at the same time is not an option.

Here are the ways I have tried to hook it up so far:

Stage box 1/4" >>> TRS Y cable >>> one side to floor wedge amp >>> other side to B205d.-------This does exactly what I want it to but it creates a buzz in the system. (ground loop I assume)

Stage box XLR >>> XLR Y cable >>> one side to floor wedge amp >>> other side to B205d.-------Same problem as above.

Stage box XLR >>> B205d input >>> B205d output >>> floor wedge amp--------No humming problems, but the mini mixer on the front panel alters the mix sent out from the B205d, this defeats the purpose of being able to independently control the volume of the keyboard.

Stage box >>> floor wedge amp input >>> input/thru on floor wedge amp >>> B205d-------The creates the mix I want and there are no humming problems, but I get very little volume out of the speakers. (is this due to an impedance mismatch? (still grasping impedance and how it affects things)

It seems to me the best solution is splitting the signal right out of the stage box, is there a way to eliminate the hum or ground loop without lessening the signal?


I hope this makes a little sense; it is hard to put this all into words. This has been posted in another forum, I hope this does not break any rules, I am just trying to get as many suggestions as possible.

[pdc]

When you split signal passively, with a Y cable or on your amp (which has a sub par input section by the sound of it) you are splitting the voltage in half more or less, and that yields artifacts in sound quality and noise. Add to that the fact that the two input stages are not the same and have different impedances.

Use the "through" connection to pass signal to the floor monitor amp from the Behringer. If the mixer main output affects that volume, the "through" would not be a true "through". Now, you must realize that the input gain will affect it, and must. So, you might have to set the gain input, mark it, and tell them not to touch it, so that the "through" voltage is sufficient to drive the floor wedge amp. If none of this works as I described, then I would return the Behringer and buy something else.

[Jacb Robinson]

The documentation from Behringer states that the "THRU" gets its signal from just before the "Main Level" and "EQ" section and combines with the "MAIN IN" signal. so I guess in a round-about way it does say that the individual channels contribute to the THRU signal, which to me is the wrong title for the jack it is closer to an "OUT" than "THRU" to me.

[daver2]

When I checked the Behringer site the "THRU" connector appears to be marked as "Link" (i.e. link to other Behringer B205d's). My reading of the Behringer documents lead me to suspect that the "THRU" or "Link" is not just a passthrough of what is fed in - but a mix of what is fed in plus the mix signal (but before the MAIN LEVEL and EQ). This would backup what you have already found - that the "local" mix affects what is passed on to the next unit (which is not what you want).

The level switch in the Behringer documentation also looks a bit strange. They refer to adjusting the level of the THRU signal - but nowhere (on a quick scan at least) have they identified the input sensitivity for the MAIN IN signal? What setting (LINE or MIC) have you used here?

Splitting the signal to two devices (using a passive Y lead) will reduce the impedance of the overall circuit - which will reduce the voltage - which will (in turn) reduce the apparent volume. It should have not caused a hum (unless there is a ground loop somewhere) - but any reduction in the signal to noise ratio would have you turning the amps up and whatever noise was being picked up would be amplified (hence the hum possibly?)

I would also be tempted to check the cables you are using and the connectors. Are things balanced before you use your 'Y' lead - but the 'Y' lead is connected up in a non-balanced manner?

What make and model is your wedge amp (or have I missed it in the post)?

Dave

[D.R.HADDOCK]

Try balanced y-split from yeyboard,
One side goes to stage box,
The other side goes to balanced to unbalanced transformer,
then to monitor.
This should solve buzz problems.
However you will have to run keyboard output higher,
because you are now driving two lines,
instead of one.

Remember the balanced to unbalanced transformer is important,
to maintain isolation and stop buzzing.

[Jacb Robinson]

I ended up having success using a 1/4" TRS Y cable directly out the of the stage box and sending one side to the amp and the other side to the Behringer speaker. Turns out my hum was just coming from having the amps and Behringer plugged into different phases of the electrical panel. I switched them to the same outlet and away went the humming and I got the mix I was looking for.


Thanks for all you input!