Can you great people help me with a PA setup issue?
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Posted on Jun 29, 2009 03:26 pm
Bluelaw
Member Since: Jun 29, 2009
I've been devouring the Live Sound Reinforcement Forum. Everyone is incredibly helpful with initial responses and follow up; I'll try to do the same in the guitar forums I participate in, where I actually have some expertise -- generate good karma. I'm still a bit confused about crossovers, subs, etc., and hope that I can get my mind cleared by asking about a particular setup. My 5 piece blues (2 guitars, bass, keys, drums, 3 vocals) is moving into small/medium clubs. We have the following:
Peavey XS 684 power mixer (2 x 200W at 4 ohms; 420 W at 8 ohms bridged). This handles all inputs we need and we like the EQ and effects.
2 No-name wedge monitors (each is 100 W at 8 ohms)
1 Hotspot Monitor (16 ohms)
Available for a good price:
Mackie FR1400 Power Amp - 2ohms: 800 W // 4 ohms: 450 W // 8 ohms: 310 W /// Bridged Mono Operation, 20 Hz to 20 kHz: 4 ohms: 1400 W
Peavey PR-12N (400 watts program and 800 watts peak) speakers (Nice and light, which I like)
I am thinking that we run the monitors off of the Power Mixer, send the unamplified monitor out signal to the Mackie to drive the FOH speakers. Simple enough, but I don't think these speakers will handle enough low end in rooms where we want to send the bass and keys direct and/or mic the kick drum. So I guess we need to add a subwoofer. But where and how do we hook it up? Is it possible to do this without buying another power amp, crossover (or both)? Do we have to have two or will one suffice? On the monitor side of the equation, by my calculations, using the Hotspot takes us a bit below 4 ohms resistance -- too dangerous for the power mixer?
Thanks in advance!
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Doug BabbittSound as good as you playMember
Since: Dec 23, 2008
Jun 29, 2009 05:26 pm I faced a very similar situation last week. A friend called and asked if his band could rent one of my Mackie SWA1501 powered subs for their first gig. The answer was yes, but I wanted to know how it fit into the overall PA, especially what they were using for a crossover. Good thing I asked, because he didn't know what a crossover was.
I gave him a couple of options. He could run his main L&R line signals into the sub, through the sub's internal 120Hz crossover and from the sub's high pass outs to the power amp and finally to the passive tops. The second option was to run out of the sub's high pass to a pair of Mackie SRM350 powered speakers that I offered to him for no additional "rent" (they bought my beers at the show). He took the latter option and it worked well.
My point is that an alternative to buying a crossover, passive sub and amp would be to buy a unit like the SWA1501, using the highpass signal to feed the amp driving the tops.
Stay tuned for better options.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Jun 29, 2009 10:01 pm Rob should hopefully catch this and get you pointed in the right direction.
Doug has given you a good start though.
Jun 29, 2009 11:20 pm Hey BlueLaw.
You can add a crossover to run a sub top set up with your system. The only bummer is, that it will be a mono FOH.
Which is not the end of the world. In small rooms, you can't hear the stereo separation anyway.
I just would not recommend running the FOH from the monitor out. There should be a main out. And that is what you want to use.
Now, it maybe wired in a stereo out. I don't know your model. So, I don't know how they have that.
But, that is a matter for later on.
Now Doug has a good point. With just about all self powered subs on the market today have a built in crossover. So, with that option, you don't need to buy any more pieces.
Your powered outs will still run your speakers. And the line out will go to the subs. All self powered subs have an input attenuator.so you can adjust the level of the subs.
I know that you wanted to use the self powered outputs for monitors. But that is a difficult way to run monitors. You have to uses the main faders as the monitor sends. And this leads to a big problem for FOH.
Reason being that you will have a problem with separation for your mix one and mix two. Since they are wired for left and right.
Now you can pan for the two mixes. Left for one Right for two. But if someone needs a vocal in both, but not as loud in one, and more in two, you can't do it. And can lead to some hard nights with the band.
With a crossover, you will need the subs, amps, and crossover. Plus additional cabling. The signal flow will be: Main outs to EQ. (Forgot the additional EQ that you will need.) EQ to crossover, Crossover to amps, Amps to speakers.
Think about how you want to add the subs to your system first. Then we will try and give you pointers on how to set it all up.
In the mean time, please read this article that I wrote on this subject. It will help you with how all the pieces go together.
www.homerecordingconnecti...ory&id=1578
Jun 30, 2009 10:43 am You guys really are the best -- I appreciate your time and thoughtful responses. I am not sure that I understand Rob's concern about using the powered mixer to run monitors and mix the FOH. That could be because I am having trouble figuring out the capabilities of the Peavey XR684. Here is info from the manual (www.peavey.com/assets/lit.../80304400.pdf):
The XR 684 can be configured as either a stereo or dual mono amplifier. The default setting is Left Main to the upper EQ and Right to the lower EQ (There are two 9-band EQ's on the face of the unit). Dual mono switches the lower EQ to (mono) PA Left + Right. The upper EQ then becomes the monitor signal only, as Peavey says, "creating an entire PA and monitor mixing system in one small, easy-to-carry package."
Besides the speaker outputs, on the front you find:
MONITOR OUTPUT: This 1/4" jack provides an output from the monitor mix to supply external power amp/monitor combinations. The level of this signal is determined by the Monitor Level control.
LEFT/MONO OUTPUT: This 1/4" jack provides an output from the Left Main mix to supply external amp/speaker combinations. The level of this signal is determined by the Main Level control. When no plug is connected to the Right Output then the right signal is mixed with the left, and both can be accessed at the Left/Mono Output. This works well when you use the internal amps for monitor and external amps for Main. Only one patch cord is required to get the Main out to the external amp.
RIGHT OUTPUT: This 1/4" jack provides an output from the Right Main mix to supply external amp/speaker combinations. The level of this signal is determined by the Main Level control.
POWER AMP INPUTS: Plugging into these jacks allows the user to go directly into the Graphic Equalizer, then into its respective power amplifier channel.
Okay, I am totally confused. I have no clue what the "Power Amp Inputs" would be used for. I am just smart enough to understand that I don't want to be sending an amplified signal from the mixer to a power amp to the FOH speakers, but it isn't clear to me whether those L/Mono and R outputs have power or not.
With regard to subwoofers, I would like to avoid powered ones if I can. At this point my band is playing small enough places that I hope a single subwoofer would take the low end pressure off the FOH speakers and give some substance to bass/keys/kick. With a large enough power amp (and crossover -- I get that much), could we send SW to one channel and the rest to the other channel, then daisy chain the FOH speakers? I don't think sacrificing stereo is that big a deal for us.
Thank you again!
Jun 30, 2009 04:28 pm I'll have to get back to you on this one. I'm still at work. And I have to read your manual to see how everything is laid out, and wired.
Jun 30, 2009 08:57 pm OK, after reading the manual, and looking at the powered head. I think I see what your after now.
Your looking to do one mix of monitors, and run a mono FOH correct?
I hope that is what your looking for. Because, after reading the PDF, that is all you can do.
The one thing that I don't fully understand about this powered head, is the fact that it states that it's stereo, when it does not have a pan pot. Not to sure why it would be stereo? If you can't stereo image the signal.
This is why I thought you maybe looking to do two monitor mixes from the unit. Utilizing the left for mix one, and the right for mix two. Bing that you cannot pan between left or right, you cannot have two mixes. And so, no reason to think that your looking for a separate mix then.
For running one mix at 4 ohms, your fine. You should have no problem there.
Now, for the FOH signal, you can only use Mon 1 output. The Left/Right outputs are now dedicated towards the monitors. You cannot split the same signal, and try to get two different results.
This means that you will have a mono FOH. Which, once again is fine.
You just need to find a single channel crossover for your system. Now I think that you are going to need more then one sub. All systems are set up of a one to one ratio. So, one top to one sub is what your going need to get the kick and bass to a level that is not destroying the sub that you purchased.
If you have only two top boxes per side right now, you maybe able to get away with just two subs.
You should be able to find used gear to suite your needs on Ebay and other sites for a reasonable price. If you would like, we can help recommend brand names and models.
Doug BabbittSound as good as you playMember
Since: Dec 23, 2008
Jul 01, 2009 04:00 pm Just a comment on how you could rig a 2 subwoofer system per Rob's recommendation with powered subs as I mentioned earlier.
On the SWA1501s that I use, the mono FOH signal would go to the left input of one sub, with the left high pass output going to the left channel on the amp powering your tops. The full range output on the left channel on this first sub would then send the signal to the second sub's right input, sending the right high pass signal to the right input on the amp feeding the tops.
[You can use either left or right ins and outs on the subs. I just find it easier keeping all the rights and lefts separated.]
It's not the most sophisticated solution, but it will get the job done and keep the rig fairly simple, which is good when showtime is looming.
Good luck!
Jul 02, 2009 08:01 pm Doug and Rob, thank you so very much for your help. I had been scratching my head with a "what's wrong with this picture" regarding the power mixer. It makes no sense to refer to this unit as "stereo," does it? Oh well -- with your advice it can suit our purposes. We purchased a QSC GX-5 power amp and used Peavey PR-15 speakers. I'll follow your suggestions when we gig with the "new" system this weekend.
Thanks again!
Jul 02, 2009 08:58 pm Cool. Let us know how it goes.
