Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[john McBride]

Hi, totally new here.

The Church I am volunteering at has a sound system that I am learning as I go along.

Although it works, there is a part of the wiring I don't understand.

There are four speakers in the system. Two are mounted up high, on either side of the dais, facing the congregation. The other pair of speakers are on the floor, just in front of the dais, also facing the congregation.

The av area is near the entrance, where I sit while setting up. There is a mackie fx8 mixer wired to a snake that routes everything up to the dais area.

The mackie manual shows the output pair as being line level, yet they run directly into the upper deck speaker pair. The power input for the mackie is 20 watts from the wall, so apparently it has enough power to make sound come out of the upper speakers.

The upper deck speakers have parallel jacks, and these are being run to the line inputs of a power amp. The left/right outputs of the power amp are being run into the biamp woofer jacks of the floor speakers.

So, just describing one side :
mixer line level --> 150 watt passive speaker --> power amp input --> power amp output --> 150 watt woofer.

Although it doesn't match the drawings in the mackie or yamaha power amp manuals, it does seem to work: the top speakers sound okay but quiet if the power amp is off, and the bass is enhanced quite a bit if the power amp is on.

I am planning to rewire it more traditionally so the mackie line level outputs go directly into the power amp inputs, and the power amp outputs drive the four speakers as 4 ohm pairs.

My two questions are :
Is this a setup in common use? It's kind of biamped.
Any pitfalls to changing it?

It's all easy to unplug and rewire so I can change it back if something strange happens.

Thank you for reading this far and participating in the forum with me.

John

[Paul G. OBrien]

My two questions are :
Is this a setup in common use? It's kind of biamped.
Any pitfalls to changing it?

No it's not common because it's all wrong, I'm sure whoever installed this had to create some special cables to connect the snake to the speakers and that should have been a red flag... but you know how that goes.

The only reason you get any sound at all is because high frequency compression drivers really don't need much power to generate audible SPLs, the Mackie might generate a 1-2 volts at max output and that equals 90-100dB when directly connected to a CD.

So yes rewire the system so the mixer goes straight to the amp and connect the speakers in fullrange mode, that will produce better results overall and if you can add an EQ to the system at some point it will get even better.

[Taylor Phillips]

So, just describing one side :
mixer line level --> 150 watt passive speaker --> power amp input --> power amp output --> 150 watt woofer.

...

My two questions are :
Is this a setup in common use? It's kind of biamped.
Any pitfalls to changing it?

Something is definitely off here.  Are you certain the flown speakers (i.e. the ones mounted high) are passive?  If they were active (i.e. they have built in amplifiers), then this setup would kinda make since. Line level isn't enough to drive a speaker, and amplifier inputs are not made to accept speaker level signal. If you can find out the brand and model of the speakers, then someone could tell you a lot more about it.  As for the floor speakers, if the amp is intentionally only driving the woofer, then it looks like it may have been somebody's attempt at a DIY subwoofer.  Usually with speakers mounted up high, ones on stage facing the audience would be for front fills covering the area not adequately covered by the main speakers, and they would need to be full range.  Perhaps there's just enough power coming from the Mackie to make the HF drivers in the flown speakers work (I certainly wouldn't think it would be loud enough for even the smallest of church services though) and then turning on the amp makes the LF drivers in the floor speakers work, but this is definitely an unorthodox and ineffective way to do it.  The amp needs to be between the mixer & the speakers in the signal chain.

[john McBride]

Are you certain the flown speakers (i.e. the ones mounted high) are passive?

The flown speakers are Yamaha SV12's and I don't see any power wires leading to them or power connections shown in the manual.

The SV12 manual shows a traditional power amp setup driving them in the example illustration.

I have some XLR cables on the way and will be looking at room EQ tools soon.

Regards,
John

[Mike Caldwell]

It maybe helpful to bring in someone who knows how set up and trouble shoot a sound system to help you straighten things out from years of helpful hands trying to fix things.

Finding that right person is key.
Depending on your locations maybe someone here could help.

[john McBride]

bring in someone who knows how set up and trouble shoot a sound system

The issue is "tape input" music from a laptop sounds acceptable, but live mics are very hushed, even with the master output set well above unity.

They did seek two opinions before asking me to look into it :
Keyboardist: Replace the mixer.
A/V Consultant : Replace everything.

My own belief is someone tried to upgrade it for bi-amping and made a wiring error.

[Dave Pluke]

They did seek two opinions before asking me to look into it :
Keyboardist: Replace the mixer.
A/V Consultant : Replace everything.

I understand where both those suggestions were coming from. A much less expensive option would be to simply wire this system correctly, as others have advised.

My only comment would be to propose (since you only have one power amp) you wire one channel to the flown speakers and the other to the ground mount speakers. That way, you can use Pan or the Channel Inputs to control the relative SPLs.

Dave

[ProSoundWeb Community]