ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Subwoofer Forum => Topic started by: Frederic Tombre on February 11, 2016, 09:06:21 am

Title: Flapping/cracking sound in subs (Soundweb Blue + Crown CTS3000 + JBL SRX718S)
Post by: Frederic Tombre on February 11, 2016, 09:06:21 am
Hi guys,
I want to share a strange issue happening with our PA. Maybe there will be others that have experienced the same issue?

Our PA i basically feeded by a pair of Soundwebs audio processors. They're doing the processing and distribution from the feed coming from the mixer. Our 6 subs are powered by three Crown CTS 3000 amplifiers. They all have a dedicated Soundweb output (no parallel outputs).
We've got issues with a flap noise coming from the subs. It sounds like a low frequent chopper wave. It's not really loud but since it's coming from the subs it can be heared in the whole hall.
We've tried to change the PIP cards on the amps, moved cables from one sub to another, but the noise is still appearing from time to other and seems to appear on different subs.

Anyone that have experienced the same issue?
Title: Re: Flapping/cracking sound in subs (Soundweb Blue + Crown CTS3000 + JBL SRX718S)
Post by: Scott Carneval on February 11, 2016, 09:48:32 am
Are you sure you're not clipping the amps? The CTS clip REALLY hard. It sounds like a pop coming out of the speakers, almost like the cone is bottoming out.


Sent from my iPhone using Tapatalk
Title: Re: Flapping/cracking sound in subs (Soundweb Blue + Crown CTS3000 + JBL SRX718S)
Post by: Spenser Hamilton on February 11, 2016, 10:23:27 am
Hi guys,
I want to share a strange issue happening with our PA. Maybe there will be others that have experienced the same issue?

Our PA i basically feeded by a pair of Soundwebs audio processors. They're doing the processing and distribution from the feed coming from the mixer. Our 6 subs are powered by three Crown CTS 3000 amplifiers. They all have a dedicated Soundweb output (no parallel outputs).
We've got issues with a flap noise coming from the subs. It sounds like a low frequent chopper wave. It's not really loud but since it's coming from the subs it can be heared in the whole hall.
We've tried to change the PIP cards on the amps, moved cables from one sub to another, but the noise is still appearing from time to other and seems to appear on different subs.

Anyone that have experienced the same issue?

Does it happen at random intervals and sounds like a machine gun?

We had an issue with one of our CTS3000s, I had a recording but can't seem to find it, a trip to Crown was neccessary to fix the problem.
Title: Re: Flapping/cracking sound in subs (Soundweb Blue + Crown CTS3000 + JBL SRX718S)
Post by: Frederic Tombre on February 12, 2016, 08:32:58 am
Are you sure you're not clipping the amps? The CTS clip REALLY hard. It sounds like a pop coming out of the speakers, almost like the cone is bottoming out.


Sent from my iPhone using Tapatalk
I don't think so. We hear it also when we're playing at normal sound levels and even without really using them (only vocal microphone with lowcut at 150Hz).

Does it happen at random intervals and sounds like a machine gun?

We had an issue with one of our CTS3000s, I had a recording but can't seem to find it, a trip to Crown was neccessary to fix the problem.
Yes it happens at random intervals and sound like a machine gun. I think I should contact my supplier to get i fixed then.
Title: Re: Flapping/cracking sound in subs (Soundweb Blue + Crown CTS3000 + JBL SRX718S)
Post by: Stephen Kirby on February 12, 2016, 01:48:27 pm
There is a sort of low frequency oscillation that can happen in some amplification circuits that used to be called "motorboating" as it sounded like one of those small single cylinder diesel engines used in motor launches.  A sort of putt putt sound.  Typically a cap has gone bad somewhere that would normally stabilize some gain stage.
Title: Re: Flapping/cracking sound in subs (Soundweb Blue + Crown CTS3000 + JBL SRX718S)
Post by: Brian Dill on March 24, 2016, 03:37:48 pm
Have you checked the entire AC path? Reminds me of an problem I had at a venue, that eventually took out my subs (Smoke and sparks) running off a Crown 5000VZ.

Hi guys,
I want to share a strange issue happening with our PA. Maybe there will be others that have experienced the same issue?

Our PA i basically feeded by a pair of Soundwebs audio processors. They're doing the processing and distribution from the feed coming from the mixer. Our 6 subs are powered by three Crown CTS 3000 amplifiers. They all have a dedicated Soundweb output (no parallel outputs).
We've got issues with a flap noise coming from the subs. It sounds like a low frequent chopper wave. It's not really loud but since it's coming from the subs it can be heared in the whole hall.
We've tried to change the PIP cards on the amps, moved cables from one sub to another, but the noise is still appearing from time to other and seems to appear on different subs.

Anyone that have experienced the same issue?
Title: Re: Flapping/cracking sound in subs (Soundweb Blue + Crown CTS3000 + JBL SRX718S)
Post by: Frederic Tombre on May 26, 2017, 05:43:47 am
Since it could be interesting for other.
The problem was eventually found and was a vacillation/fault contact on some potentiometers. The amps were sent to reparation and since we don't have any problems any more.

Hi guys,
I want to share a strange issue happening with our PA. Maybe there will be others that have experienced the same issue?

Our PA i basically feeded by a pair of Soundwebs audio processors. They're doing the processing and distribution from the feed coming from the mixer. Our 6 subs are powered by three Crown CTS 3000 amplifiers. They all have a dedicated Soundweb output (no parallel outputs).
We've got issues with a flap noise coming from the subs. It sounds like a low frequent chopper wave. It's not really loud but since it's coming from the subs it can be heared in the whole hall.
We've tried to change the PIP cards on the amps, moved cables from one sub to another, but the noise is still appearing from time to other and seems to appear on different subs.

Anyone that have experienced the same issue?