Why didn't this work??

[I-Love-Ratm]

Hi guys,

My band has a PA consisting of a Mackie CFX16 and 2 dB Opera 205 powered speakers (400w 15" speakers). This works great for small bar gigs etc. Recently we had a function in a larger room so we decided to add a sub to fill out the sound.

So we borrowed an 18" passive Behringer bin and a power amp from a buddy. The Mackie desk has a designated "Sub Out" that apparently has a built in Crossover at 75Hz. So it should be a simple set up right?

For some reason I could only get a little bit coming from the sub when I cranked the kick drum channel way up. Can anyone explain why it didn't work properly??

Was it because it was a stereo power amp? Or the gear was Behringer and kinda crappy? Or something else?

Any help is appreciated guys!

Cheers!

 

[Zooberwerx]

Interesting but not enough information. Could be operator error / misapplication...not like that ever happens, eh? Personally, I hate the preset 75 hz as there's a lot of kick drum & bass energy in the 80-110 hz region. Any way you can set it up in a "sterile" (non-venue) environment for diagnostics? Will you have ongoing access to the sub and power amp? If so...sweet!

Edit: define the Behringer sub and power amp (make / model). Could be a bridged configuration may help but, as mentioned, we need the full dope.

Riis

 

[ggunn]

Hi guys,

My band has a PA consisting of a Mackie CFX16 and 2 dB Opera 205 powered speakers (400w 15" speakers). This works great for small bar gigs etc. Recently we had a function in a larger room so we decided to add a sub to fill out the sound.

So we borrowed an 18" passive Behringer bin and a power amp from a buddy. The Mackie desk has a designated "Sub Out" that apparently has a built in Crossover at 75Hz. So it should be a simple set up right?

For some reason I could only get a little bit coming from the sub when I cranked the kick drum channel way up. Can anyone explain why it didn't work properly??

Was it because it was a stereo power amp? Or the gear was Behringer and kinda crappy? Or something else?

Any help is appreciated guys!

Cheers!

My guess is that the sub is switchable between line level and speaker level at the input; it was set to "speaker" and you fed it a line level signal.

 

[flatfender]

Subs take a lot of power so maybe the amp wasn't up to it the way you were using it. Maybe bridged output vs stereo

75hz is pretty low for the sub xover point. Not much audio information there. I crossover my subs at 200-225hz

The sub output relies on the master level output so maybe if you're running your masters low where there wasn't enough input for the sub amp to work with.

You'll probably need to add a outboard crossover to set it up right

 

[RattleSnack]

Is it possible you are not feeding it with low frequences? Ie, you have high pass filter on kick drum channel? Just to be sure, you could use signal generator (smartphone with signal generator app, connected via phones-out should do).
Sorry if I am in the wrong ballpark, it just crossed my mind...

 

[Zooberwerx]

My guess is that the sub is switchable between line level and speaker level at the input; it was set to "speaker" and you fed it a line level signal.

Suspicious but the OP described it as a passive bin. Good point when dealing with powered enclosures, though!

Edit: as mentioned, make sure to defeat any 100 hz hpf's on the kick drum mic channel. It's easy to engage by accident and appropriate more for vocal channels.

Riis

 

[taurus1]

Subs take a lot of power so maybe the amp wasn't up to it the way you were using it. Maybe bridged output vs stereo

75hz is pretty low for the sub xover point. Not much audio information there. I crossover my subs at 200-225hz

The sub output relies on the master level output so maybe if you're running your masters low where there wasn't enough input for the sub amp to work with.

You'll probably need to add a outboard crossover to set it up right

it depends on how you're running your system.
if his main speakers aren't x-overed, then 75 Hz would be a good x-over point for just the sub alone.
you don't want the sub and main speakers pumping out the same frequencies because it will cause all kinds of negative side effects.

 

[Zooberwerx]

it depends on how you're running your system.
if his main speakers aren't x-overed, then 75 Hz would be a good x-over point for just the sub alone.
you don't want the sub and main speakers pumping out the same frequencies because it will cause all kinds of negative side effects.

Good point. Once you get your sub output figured out and have continued access to the enclosure / power amp, you may want to consider adding an inexpensive crossover...like a Behringer. I see some going for $60-80 on E-bay.

The preset 75 hz sub-out was intended to supplement the mains as, historically, this is where we begin to see significant roll-off in the lower freq's. That being said, there's still a lot of bass energy (>75 hz) which I'd rather see carried by a decent, adequately powered sub enclosure.

Riis

 

[I-Love-Ratm]

It was a Behringer 1800X. The power amp was sufficient too. I think the 75hZ crossover is too low. A lot of good kick drum stuff is missing from that.

 

[DWBass]

Old band I was in. Had a similar experience but using a powered sub. Mixer had a dedicated Mono out (Sub out) but the signal was extremely low. Could have been user error as it was the first time us trying to set it up that way. Sub was all the way up as was the channel on the mixer. I'm no longer in the band but I still wonder what happened.