PA Issue...

Danny1969

Any amp needs a certain level on the input before it can drive it's maximum power into a load. Lets say you might need 2V rms on the input of the amp before it can drive it's full 40 volts across 4 Ohms which is 400 watts of power. Now give the amp only 1V rms on the input and it's only ever gonna drive 200 Watts across the speaker. This is called sensitivity 

Impedance plays a small part but not a big part since most output stages will be opamps and quite happy to drive hard into 600 Ohms or lower

ICBM

simonbeckwith said:

What sort of specs do we need to be looking at to sort this out? Is this a similar issue to how some pedals behave dependant on output/input impedance? Do we need a certain type of output impedance to help drive the signal more, or is it a case of a couple of DI boxes as previously mentioned.

Ideally you need a pro-quality desk with balanced outputs, as Danny said. That will almost certainly have the correct levels to drive the Mackies. DI boxes *might* work and are worth trying if you've got a couple. Be aware that the Mackies won't supply phantom power so you will need to make sure they've got fresh batteries in them.

I can't restate this enough though - if you're putting bass and kick drum through the PA then you need subs, or at the very least, one (they're essentially non-directional, so position and projection isn't an issue). If you try to put bass and kick through the Mackies you will drastically limit their headroom and clarity for the rest of what's going through them. A powered sub would probably be easier now that the old ones have gone, and allow you to go to an unpowered desk - although if you're going to keep the Behringer then you could make use of its power amp and drive a passive sub. Currently you're carrying around a 1600W power amp which you can't use for anything.

Personally I think you've done this the wrong way round - you should have got better passive tops to run from the Behringer's power amp, and powered subs rather than powered top cabs. The Behringer even has a dedicated output to drive one, with a sub filter frequency control (the Mono Out). Or you could patch that into the Power Amp Inserts to use it to drive a passive sub.

https://media.music-group.com/media/PLM/data/docs/P0A8O/PMP6000_PMP4000_PMP1000_M_EN.pdf

simonbeckwith

Buggar! I'll break the good news to him

Jalapeno

ICBM said:

Jalapeno said:

If the old speakers were 4ohms and the new ones 16ohms that'd make a difference.

No it won’t. The Mackies are powered cabs so impedance matching is irrelevant.

There are no 16-ohm PA speakers anyway, after about 1975...

Missed that, my bad

simonbeckwith

He said just tested a tested at a lower volume using a jack to xlr lead and its noticeably louder...... couple of new leads should sort it out by the sounds of it, no pun intended! Fingers crossed. Going to look into subs as and when more functions are booked

maltingsaudio

simonbeckwith said:

He said just tested a tested at a lower volume using a jack to xlr lead and its noticeably louder...... couple of new leads should sort it out by the sounds of it, no pun intended! Fingers crossed. Going to look into subs as and when more functions are 

Yup balanced and unbalanced cables do make a difference as you have found out

simonbeckwith

I've only seen a video he's sent me but the difference is crazy! Very surprised!

robinbowes

The Behringer outputs are unbalanced or unbalanced, depending on which page of the manual you read (page 13 vs. page 18 of https://media.music-group.com/media/PLM/data/docs/P0A8O/PMP6000_PMP4000_PMP1000_M_EN.pdf).

The Mackie input are combo sockets and will accept balanced or unbalanced jack, or balanced XLR connections.

If it were me, I'd do some tests like plug in a TRS plug to an output of the Behringer and test whether the ring is shorted to the shield or not. If it's balanced, I'd make up a TRS jack to XLR cable; if unbalanced, I'd just use a regular jack-jack cable.

R.

simonbeckwith

I think he used a trs to xlr and that's what brought everything to life so he's gonna get a couple and test the lot as he only had one at home in his box of leads. It was like night and day the difference between trs to xlr and just standard jack to jack

robinbowes

simonbeckwith said:

I think he used a trs to xlr and that's what brought everything to life so he's gonna get a couple and test the lot as he only had one at home in his box of leads. It was like night and day the difference between trs to xlr and just standard jack to jack

If he wants to buy good quality leads, I can make them to order - Neutrik connectors, Van Damme cable (see here for a few more details). It would be about £24 for a 10m lead - male TRS Jack to male XLR. Message me if interested.

R.

ICBM

It does sound like - slightly surprisingly, since it isn't mentioned in the manual - the Behringer outputs are balanced, so essentially there is a 'DI box' built in.

Your choice now is to either get passive subs to run from the Behringer's own power amp, or to start on an upgrade path with powered ones which will mean you can replace the Behringer with a standard desk eventually. You can keep the cost down initially by only buying one sub, if you want.

If he hasn't got rid of the spare passive top cabs, make sure he doesn't - for now, you've still got the backup option of running them from the Behringer if you need.

simonbeckwith

@robinbowes I'll speak to him and see what he wants to do

@icbm yeh, need to have a discussion about which step is next, I've already said keep hold of the tops for backups!