Weirdness in a waveform

[pucho812]

This is a head scratcher.
Have a mono bass drum track that sounds big and full and lots of low end when coming from the center speaker in an lcr arrangement.
If I take that same track and and use divergence control to have it be phantom center, the big beautiful low end kick signal changes sounding thin and much different. Any ideas as to why? It’s the only track I have ever seen this happen on.

 

[JohnRoberts]

I don't know what a divergence control is or does, but the bass drum may have a low frequency fundamental that happens to be out of phase, when "diverged" .

JR

 

[pucho812]

I don't know what a divergence control is or does, but the bass drum may have a low frequency fundamental that happens to be out of phase, when "diverged" .

JR

Basically when working in surround sound5.1, 7.1, atmos, etc) divergence adjusts the left/center/right panning parameters to control the portion of front-placed sounds mixed to the center channel vs phantom center.
So if I place this sound up the middle I get it out the center speaker. If I crank up divergence to fill the same sound now fills the phantom center coming from
Left and right speakers and not the center speakers.

 

[JohnRoberts]

OK so phantom center means "mono" same in both L and R.

I still do not know, but may be related to the relatively low frequency content... don't surround processors scrub low bass out of center dialog channels and steer them to the sub channel?

Pure speculation on my part...

JR

 

[pucho812]

OK so phantom center means "mono" same in both L and R.

I still do not know, but may be related to the relatively low frequency content... don't surround processors scrub low bass out of center dialog channels and steer them to the sub channel?

Pure speculation on my part...

JR

Not always in a mix you have separate controls for that.

 

[RachelBirdy]

What happens if you mute either the left or right speaker while it's in phantom center? Assuming the speakers are capable of the same low end reproduction, my first thought is maybe some sort of phase cancellation between the speakers

 

[sodderboy]

I’m with Rachel.
That issue is on more than one punch list over the years, usually with wired distributed cue systems. When it’s on your ears, it makes your head dip to the side. Patch around normals.
Check the monitors first, then through your chain.
I keep the Alan Parsons test disc on my phone for that stuff.
Mike

 

[pucho812]

All l,c,r, speakers are the same, so yes maybe some phase cancellation except if I dial divergence back from full phantom center to center I get low end back with sound on all 3 speakers

 

[JohnRoberts]

sure appears to be cancellation.

JR

 

[Youngwhisk]

Hypothetically, I wonder how it would perfom if you reversed the polarity on one of the speakers as a test?

 

[pucho812]

Hypothetically, I wonder how it would perfom if you reversed the polarity on one of the speakers as a test?

With fill divergence in, phantom center only, I get an even worse sound.

 

[JohnRoberts]

With fill divergence in, phantom center only, I get an even worse sound.

its not nice to fool mother nature....

JR

 

[Gold]

Can you do a frequency sweep? First I’d figure out if it’s an acoustic or electrical problem. It sounds more like an electrical problem to me but I wouldn’t bet my life on it. If you hear peaks and nulls that match the problem it’s the room.

 

[pucho812]

electrical, hmmm. Let’s see.
Digital signal from the daw, digital input into a digital desk channel, out of the digital desk master to a digital input on the speakers. The entire signal chain is digital until it becomes acoustical. So I think it’s ultimately an acoustical issue and the previous answers are correct.

 

[Gold]

electrical, hmmm. Let’s see.
Digital signal from the daw, digital input into a digital desk channel, out of the digital desk master to a digital input on the speakers. The entire signal chain is digital until it becomes acoustical. So I think it’s ultimately an acoustical issue and the previous answers are correct.

Just because the signal path is digital doesn’t mean nothing can go wrong. For instance the TC M5000 is well known for flipping left and right channels if it misses a leading edge. I could imagine an accidental polarity flip somewhere.

I would also sum L+R and feed the mono signal to the left and right speakers. Then compare that to mono sum in the center channel speaker. If they sound very different I’d doubt it’s a acoustics problem. If it does sound different drag the the left speaker to the center position and see if it now sounds like the real center speaker.

 

[pucho812]

Well it’s a mono signal the entire path until it hits the master bus which is a full surround.

 

[Gold]

I’d play it through either the left only or right only speaker. Then try the same thing in the center. Then physically swap the left (or right) speaker with the center speaker. Hopefully with the same cabling. If the same problem follows the speaker it’s an equipment problem. If it happens in the same way with speakers swapped it’s the acoustics.

 

[pucho812]

more testing on this today as I had a moment. The same sound of panned hard left or right does the exact same drop out of low end in the kick as I was getting with the divergence knob.

 

[Gold]

I’m still a little confused about the signal path. Mono out of the DAW into a channel on a digital console. I’m not so sure how the routing to the speakers is being done. Is there a panning matrix in the console? Where is the Divergence control?

 

[pucho812]

There is a panning matrix in the desk doing 7.1 that is where there is divergence control.