Controlling a Mongrel PA

[junglist]

Hi,

 

PA newbie here,

 

I'm currently running a bit of a mix & match PA system and I need a bit of a steer on how to configure my mongrel PA and bring it under control.

 

In my amp rack I have:

 

1 x Behringer X-18 Air Mixer

 

and the amps -

 

1 x d&b P1200A (used with C6 tops)

1 x Crown XLS602 (used with JBL SRX818S subs)

1 x Crown XLS802 (used with Logic Systems dbl 18 subs)

 

I also run a pair of Pioneer XPRS active subs.

 

Up to now I used the d&b to drive the C6 mid/tops and the d&b amp signal outs to feed the Pioneer subs. I then configure the mixer AUX 1/2 & 3/4 sends to feed both Crown amps.

 

I find it all a bit of a faff and I'd like to know the best way to bring all this under control so that the LR mixer output level applies globally to the whole system.

 

Q1. How do I send the stereo XLR out from the mixer into all the amp inputs? The d&b has signal outs but I can't see anything like that on the Crown amps.

 

Q2. Is there a magic rack line splitter/system eq with enough OUTS that would help me manage all this more effectively?

 

Really unsure as to the best way to tackle this.

 

Cheers,

 

J

 

XLS602 back panel

 

[GR1]

I would use something like a Behringer DS2800 Ultralink with 2 inputs and 4 outputs for each input. It costs £49 plus VAT and delivery from Thomann who should be organised so they pay the VAT before shipping to the UK then you won't have any nasty surprises cost wise. You could just use a cable Y splitter to feed the 2 Crown amps from the D&B link outputs but the Behringer is cheap so why not do it properly? Edited February 11, 2021 by GR1

[sunray]

I would use something like a Behringer DS2800 Ultralink with 2 inputs and 4 outputs for each input. It costs £49 plus VAT and delivery from Thomann who should be organised so they pay the VAT before shipping to the UK then you won't have any nasty surprises cost wise. You could just use a cable Y splitter to feed the 2 Crown amps from the D&B link outputs but the Behringer is cheap so why not do it properly?

I was going to suggest a 2 channel product but the DS2800 looks to be more useful and a decent bit cheaper too. On top of that I like Behringer products. Edited February 11, 2021 by sunray

[J Pearce]

I'd just solder splitter cables. Unless you want something fancier like a speaker processor to handle level/limiting/EQ/crossovers etc.

[junglist]

Thankyou folks,

 

I took GR1's advice , had a quick look at the Behringer and it's exactly what I need. Just ordered from Thomann for £49.

 

 

https://www.thomann.de/gb/behringer_ds2800.htm

 

Thanks for the help, really impressed again.

 

Cheers

 

J

 

 

 

I would use something like a Behringer DS2800 Ultralink with 2 inputs and 4 outputs for each input. It costs £49 plus VAT and delivery from Thomann who should be organised so they pay the VAT before shipping to the UK then you won't have any nasty surprises cost wise. You could just use a cable Y splitter to feed the 2 Crown amps from the D&B link outputs but the Behringer is cheap so why not do it properly?

 

Thanks mate, just the ticket.

 

J

 

Just so I can try and understand the technical side....

 

Does splitting the mixer output like this affect the quality of the original signal in any way? Surely it must?

 

I'd really like to understand the sciencey bit, but only if somebody is prepared to explain what is occurring here as though they were talking to a 5 year old...or a Labrador.

 

Cheers,

 

J

[themadhippy]

Does splitting the mixer output like this affect the quality of the original signal in any way? Surely it must?

Theoretically yes,in practice no.For the science behind it compare the output impedance of most mixers and compare it too the input impedance of most PA amps,the desk will have a low output impedance whilst the amps have a high impedance input

Edited February 11, 2021 by themadhippy

[David Morison]

@OP:

 

How are you effecting the crossover parameters for your subs?

Y-splitting the signal from your desk straight into the sub amps as you'll be doing with that Behringer unit doesn't give you any control over what signal goes to them, so they'll try to reproduce lots of mids as well as the bass range.

That means they're overlapping much of what your C6's should be doing, which might give extra volume but will almost certainly rob you of clarity.

A proper loudspeaker management system AKA DSP unit will allow you to set a proper low pass filter for them so they don't overlap the mains, improving sound quality and reducing the load on the bass drivers and amps.

The D&B amp will already be able to do the relevant filtering so the C6's don't see all the sub info, so even a simple unit like This should be enough for you to manage the subs.

HTH,

David.

[sunray]

Thankyou folks,

 

I took GR1's advice , had a quick look at the Behringer and it's exactly what I need. Just ordered from Thomann for £49.

 

 

https://www.thomann....nger_ds2800.htm

 

Thanks for the help, really impressed again.

 

Cheers

 

J

 

 

 

I would use something like a Behringer DS2800 Ultralink with 2 inputs and 4 outputs for each input. It costs £49 plus VAT and delivery from Thomann who should be organised so they pay the VAT before shipping to the UK then you won't have any nasty surprises cost wise. You could just use a cable Y splitter to feed the 2 Crown amps from the D&B link outputs but the Behringer is cheap so why not do it properly?

 

Thanks mate, just the ticket.

 

J

 

Just so I can try and understand the technical side....

 

Does splitting the mixer output like this affect the quality of the original signal in any way? Surely it must?

 

I'd really like to understand the sciencey bit, but only if somebody is prepared to explain what is occurring here as though they were talking to a 5 year old...or a Labrador.

 

Cheers,

 

J

No problem at all 5 year old.

I used to install night clubs where it was common to run multiple amplifiers, quite often 30, if the amps didn't have loop out sockets I'd make up cables with multiple plugs along the length allowing about 3" of slack between amplifiers. in the back of the rack all that showed was an FST running down the row of plugs.

Typical amp input impedance of say 20KΩ20Kohms. 20 amps in parallel = 1Kohms typical output impedance of mixer/compressor etc of 100 ohms. Theoretically that will drive 200 Amplifiers.

As long as the multiple connexions doesn't introduce a ploblem such as earth loops, there shouldn't be a problem.

In fact the unit I was going to suggest was a basic stereo crossover with a single stereo pair of outputs each for bass mid top and it would have required split leads to feed the multiple bass amps.

The P1200 has internal filtering, are the line outs filtered too? can this be 100Hz low pass out?If so the bass amps could possibly just be multipled directly from there.

In the night clubs we found running stereo bass was very wrong, creating some silly echoes so the filters we used were mono bass o/p.

20KΩ

Edited February 11, 2021 by sunray