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[Cliff D Ribeiro]

Hello Everyone,

Got a question. Recently, for new years we deployed an 8 double 18 sub system for an event. It was glorious, except for the  time when the dj system started skipping! So, we're at full tilt boogie, and the dj's rig started skipping. Not only was it skipping but his laptop (a macbook pro) started freaking out  - his keyboard light started going on and off at different points, his software started crashing and he had to restart multiple times.

So your thinking well it's just the dj's crappy gear, well turns out, we had 2 dj's sharing the same stage, with 2 different setups, albeit both were macbook pros. And both systems started failing. I think to myself, they are tied to power, maybe we were getting power drops. I meter the power, and a solid 120.2 at the quadbox that they were tied to. I go back to the distro and again all solid.

The dj says, hey maybe there's too much bass. His laptop has a solid state drive, and he was running traktor. This is all digital, buffered to RAM. How the hell is anything skipping? The second dj, also fully digital system, running ableton, skips and his computer freezes.

We grab some foam from some pelicans we had nearby and placed them under the laptop and his control surface, this gave us more headroom, but not as much as we would like. We had to essentially cut back on volume as his rig would skip.

So, could this be a case of too much bass? I'm pretty sure there are stages out there where there are 8-12 doubles on stage alone, let alone for the whole room, and they don't have problems. What do you guys think? How can we prevent solid state systems from skipping in the future?

[John J Saunders]

Since new Mac books have no moving parts I would seriously doubt it is an issue with the actual computer ssd. What I would look at would be the connections to audio IO. I have seen the thunderbolt and usb ports be very finicky and I always tape them to the machine. And if a computer was randomly loosing the connection to a interface the computer and software would not be happy at all. I guess it could also be a connection somewhere inside the laptop but I have opened them up and they are built really well.

As for the keyboard lighting up randomly I suspect that is a separate issue with the auto light sensor not knowing what's going on with flashing/moving stage lighting. That feature can be turned off in the system preferences.

[Scott Helmke]

Could try moving the DJ a bit away from dead center.  Summation of low frequency waves in a room is a rather complex topic, but the power alley is a typically avoidable problem.

[Cliff D Ribeiro]

Since new Mac books have no moving parts I would seriously doubt it is an issue with the actual computer ssd. What I would look at would be the connections to audio IO. I have seen the thunderbolt and usb ports be very finicky and I always tape them to the machine. And if a computer was randomly loosing the connection to a interface the computer and software would not be happy at all. I guess it could also be a connection somewhere inside the laptop but I have opened them up and they are built really well.

As for the keyboard lighting up randomly I suspect that is a separate issue with the auto light sensor not knowing what's going on with flashing/moving stage lighting. That feature can be turned off in the system preferences.

The dj had to bring down his lows on his mixer from 12 o'clock to around 9  o'clock. Anything past 9 o'clock and he would skip. We had all connections taped down. Eventually the second dj just threw in the towel, Some said it felt like an earthquake when the bass dropped.

About power alley. We didn't flank the subs, they were in an arc, and he had fairly even low end coverage in the intended coverage zone, but it would skip. And again, after we added absorption it got better, not 100% but significantly better.

[John Roberts {JR}]

How solid is the mains power that outlet your rig is plugged into? If the amps are drawing down the mains voltage momentarily, the digital gear might get squirrely..

JR

[Cliff D Ribeiro]

How solid is the mains power that outlet your rig is plugged into? If the amps are drawing down the mains voltage momentarily, the digital gear might get squirrely..

JR

I had a meter with me, metered at the quad box by the dj, and metered at our cam input point. Voltage was a solid 120- 121. No crazy oscilliations. What amazed me was that both dj rigs were behaving that way. And in the heat of the moment all you want to do is fix it somehow. For a few minutes I had to run spotify for his machine to stabilize again, and spotify from my phone was solid.

[Ed Walters]

Some physics and vibration basics:

1) everything has mass
2) everything is a spring
3) all spring-mass systems oscillate
4) all oscillating systems have resonance

This includes contact spring fingers against pins or pads. Sufficient level of vibration at the right frequency can cause connectors to electrically fail for moments -- even if it is "taped" because the connector body isn't the issue, the contact vibrating inside is. These contacts could be on the interfaces or internal to the device (say, the SSD connector or the memory connector or, or, or...)

The fact that turning down or isolating the computer reduced the issue, and that both problem rigs had the same computer, suggest that some contact in a MacBook pro is failing under high amplitude vibration.  I do not know if Apple provides the detailed specs needed, but many electronic devices are characterized for maximum shock and vibration over given frequency ranges. Testing over ranges of audio frequencies under extreme levels has come up here before; NASA has a PA system to do this for payload testing. It would suck if the processor controlling something important in a rocket ship crashed due to launch pad vibration...

Ed Walters

[Cliff D Ribeiro]

Some physics and vibration basics:

1) everything has mass
2) everything is a spring
3) all spring-mass systems oscillate
4) all oscillating systems have resonance

This includes contact spring fingers against pins or pads. Sufficient level of vibration at the right frequency can cause connectors to electrically fail for moments -- even if it is "taped" because the connector body isn't the issue, the contact vibrating inside is. These contacts could be on the interfaces or internal to the device (say, the SSD connector or the memory connector or, or, or...)

The fact that turning down or isolating the computer reduced the issue, and that both problem rigs had the same computer, suggest that some contact in a MacBook pro is failing under high amplitude vibration.  I do not know if Apple provides the detailed specs needed, but many electronic devices are characterized for maximum shock and vibration over given frequency ranges. Testing over ranges of audio frequencies under extreme levels has come up here before; NASA has a PA system to do this for payload testing. It would suck if the processor controlling something important in a rocket ship crashed due to launch pad vibration...

Ed Walters

I guess my question is, what is a practical way to avoid this in the future? The foam helped but not as much as it could of helped. I'm sure if I ran into this problem someone else ran into this problem. Are there any solutions out there, commercial or diy? Granted the foam, but anything else?

[TJ (Tom) Cornish]

Some physics and vibration basics:

1) everything has mass
2) everything is a spring
3) all spring-mass systems oscillate
4) all oscillating systems have resonance

This includes contact spring fingers against pins or pads. Sufficient level of vibration at the right frequency can cause connectors to electrically fail for moments -- even if it is "taped" because the connector body isn't the issue, the contact vibrating inside is. These contacts could be on the interfaces or internal to the device (say, the SSD connector or the memory connector or, or, or...)

The fact that turning down or isolating the computer reduced the issue, and that both problem rigs had the same computer, suggest that some contact in a MacBook pro is failing under high amplitude vibration.  I do not know if Apple provides the detailed specs needed, but many electronic devices are characterized for maximum shock and vibration over given frequency ranges. Testing over ranges of audio frequencies under extreme levels has come up here before; NASA has a PA system to do this for payload testing. It would suck if the processor controlling something important in a rocket ship crashed due to launch pad vibration...

Ed Walters

A related thought - in the transition from spinning disks to SSDs, a number of machines still have accelerometers that are designed to park the disk heads if the machine takes a tumble.  I don't know how much of this vestigial functionality exists in the machines you use, but it can happen.

Your only solutions will be things that reduce the vibration to your machines - either by isolating your computers, or by acoustical techniques to reduce bass on the DJ platform - cardioid subs, etc.

[Cliff D Ribeiro]

Some physics and vibration basics:

1) everything has mass
2) everything is a spring
3) all spring-mass systems oscillate
4) all oscillating systems have resonance

This includes contact spring fingers against pins or pads. Sufficient level of vibration at the right frequency can cause connectors to electrically fail for moments -- even if it is "taped" because the connector body isn't the issue, the contact vibrating inside is. These contacts could be on the interfaces or internal to the device (say, the SSD connector or the memory connector or, or, or...)

The fact that turning down or isolating the computer reduced the issue, and that both problem rigs had the same computer, suggest that some contact in a MacBook pro is failing under high amplitude vibration.  I do not know if Apple provides the detailed specs needed, but many electronic devices are characterized for maximum shock and vibration over given frequency ranges. Testing over ranges of audio frequencies under extreme levels has come up here before; NASA has a PA system to do this for payload testing. It would suck if the processor controlling something important in a rocket ship crashed due to launch pad vibration...

Ed Walters

Ed, they both had macbooks but were not on the same computer. 2 completely different macbooks, different generations also. Albeit both macbooks. One was probably pre 2012 mabook running abelton a moto 824, the other was a current macbook running traktor and the traktor interface.

[ProSoundWeb Community]