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Title: So much lowend even a solid state drive skips
Post by: Cliff D Ribeiro on January 04, 2016, 09:51:53 am
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?
Title: So much lowend even a solid state drive skips
Post by: John J Saunders on January 04, 2016, 10:03:57 am
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.
Title: Re: So much lowend even a solid state drive skips
Post by: Scott Helmke on January 04, 2016, 10:05:51 am
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.
Title: Re: So much lowend even a solid state drive skips
Post by: Cliff D Ribeiro on January 04, 2016, 10:26:22 am
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.
Title: Re: So much lowend even a solid state drive skips
Post by: John Roberts {JR} on January 04, 2016, 10:47:08 am
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
Title: Re: So much lowend even a solid state drive skips
Post by: Cliff D Ribeiro on January 04, 2016, 10:53:25 am
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.
Title: Re: So much lowend even a solid state drive skips
Post by: Ed Walters on January 04, 2016, 11:26:54 am
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
Title: Re: So much lowend even a solid state drive skips
Post by: Cliff D Ribeiro on January 04, 2016, 11:32:10 am
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?
Title: Re: So much lowend even a solid state drive skips
Post by: TJ (Tom) Cornish on January 04, 2016, 11:52:52 am
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.
Title: Re: So much lowend even a solid state drive skips
Post by: Cliff D Ribeiro on January 04, 2016, 12:12:42 pm
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.
Title: Re: So much lowend even a solid state drive skips
Post by: Scott Carneval on January 04, 2016, 12:16:15 pm
What about the DJ control interface? Turntables? CDJ's? Fisher Price My First DJ Controller?

Even the digital controllers have pressure sensitive platters, so they could have been freaking out from the bass. Every MacBook Pro I've ever opened has shock-mounted HDD, so I really doubt that's the issue. Most DJ's I know either set their laptop on the neoprene sleeve they carry it in, or use a stand to reduce the vibration.
Title: Re: So much lowend even a solid state drive skips
Post by: Franklin Benjamin on January 04, 2016, 12:28:17 pm

Try going cardioid. It should reduce the low end energy on stage.   I doubt power caused the issue even though the power connector is magnetic, battery should still be supplying steady power.  Unless the continuous vibration of the connector causes it to crash.

I couldn't really tell. What subs are you using?
Title: Re: So much lowend even a solid state drive skips
Post by: Stephen Kirby on January 04, 2016, 01:16:22 pm
Having the subs in an arc like that means that there is a very focused concentration of sound at the center of the arc, in the rear of the subs.  I've seen some MAAP plots of various arc configurations and if you had the DJ booth behind those near the apex of the arc, that was the highest SPL of the entire rig.

I work with a bunch of ex-Apple engineers including several reliability engineers.  They do test the computers under pretty substantial vibration but possibly not what those were seeing in that situation.  They also do bunches of shock loading tests on the connectors to make sure someone tripping on a cord doesn't break anything in the computer.  Which is not to say that a USB type A connector might not glitch under severe vibration.  The design was developed to maintain characteristic impedance rather than use in a helicopter. 
Title: Re: So much lowend even a solid state drive skips
Post by: brian maddox on January 04, 2016, 01:19:45 pm
...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

Yes they do.  I've seen it.  It's pretty impressive...  :)

Maybe Apple needs to borrow it for a test.  :)
Title: Re: So much lowend even a solid state drive skips
Post by: Jim McKeveny on January 04, 2016, 01:29:13 pm
Since new Mac books have no moving parts..

Keys?
Title: Re: So much lowend even a solid state drive skips
Post by: Craig Hauber on January 04, 2016, 01:36:47 pm
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.
Yes -what Tom said-  pretend it's the 70's, 80's and even the 90's again and act like you have turntables (that actually playback the music -yes kids they actually used to do that :-)
I remember all the shenanigans that DJ's used to go through to keep LF from feeding back through the turntables and all the cushions, foam, patio slabs, hanging springs etc.. -some of it would actually work :-)

Other ideas to look into:

-Check the power as John suggested, but with an older needle-style meter that you can actually see pulses -usually a handheld digital meter won't respond fast enough to see the surges from the sub amp's draw.  (the bargraph display on older furman rack light units in FOH racks was great for seeing this)

-From your pictures it looks like the subs are behind the DJ firing through a screen? 
Put the bass on the dancefloor not the DJ booth! Isolate the conducted mechanical vibration from the stage/riser/whatever that the DJ is set-up on.

-try to "cardiod" your setup just enough to get a cancellation right at the DJ table. 

-Fire-up a tone generator and walk the room -you'll hear/feel nodes and dead spots, try to place the DJ in one of the dead spots!  you could go as far as to move the subs to separated blocks to even force cancellation spots.

Also make sure your not killing other spots in the club -I once rattled a bar so much a glass shelf walked off it's mounting, collapsed and dumped the entire top-shelf row onto the floor -including the bottle of Louis XIII -luckily the display case kept bottle from shattering but it dumped out over 3/4 of it :-(
Title: Re: So much lowend even a solid state drive skips
Post by: Hayden J. Nebus on January 04, 2016, 05:07:17 pm
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?

Something like an old-school turntable sandbox isolator might work and is a cheap DIY. you need a 5 sided box, a float plate that fits inside the box without touching the walls, and a bag of play sand. For extra isolation, you can make 6 feet out of 3 racquetballs cut in half and attach to the box.
 
Title: Re: So much lowend even a solid state drive skips
Post by: Len Zenith Jr on January 04, 2016, 05:44:04 pm
What kind of SPL would you figure was at the DJ table?
Title: Re: So much lowend even a solid state drive skips
Post by: Dave Jones on January 05, 2016, 04:02:41 am
As everything else has been eliminated, I'm betting that vibrations somehow triggered keyboard keystrokes or trackpad clicks which caused the randomness.

Dave.
Title: Re: So much lowend even a solid state drive skips
Post by: Stephen Kirby on January 05, 2016, 01:01:11 pm
Asked one of the ex-Apple folks who worked on these and with the force required to actuate the key switches, it's highly unlikely that vibration would cause an actuation.
Title: Re: So much lowend even a solid state drive skips
Post by: Lyle Williams on January 05, 2016, 02:00:57 pm
https://support.apple.com/en-au/HT201666

Probably sold with a HDD and was third party upgraded (or home upgraded) to a SSD.

 
Title: Re: So much lowend even a solid state drive skips
Post by: Luke Geis on January 21, 2016, 11:05:31 pm
It was vibration related for sure.

I had a live band I was hoping to record one night, but had to place the FOH near a sub. Needless to say all was fine until the band started playing and the computer essentially went into lock down. The vibration causes the HDD and even SSD drives to stop. This is the fail safe that many computers have now. It senses free fall or excessive vibration and shuts the drives down to protect the disk and the data.

As soon as the band stopped playing the computer I had would act like normal and as soon as they would start again it would go bonkers.
Title: Re: So much lowend even a solid state drive skips
Post by: paul bell on January 22, 2016, 08:44:03 am
That's an interesting sub deployment. How high was the ceiling? May I ask, what subs are they?
Title: Re: So much lowend even a solid state drive skips
Post by: Steven Eudaly on January 22, 2016, 12:52:04 pm
That's an interesting sub deployment. How high was the ceiling? May I ask, what subs are they?

Look like EAW SB1000.
Title: Re: So much lowend even a solid state drive skips
Post by: Lyle Williams on January 23, 2016, 02:29:14 am
https://support.apple.com/en-au/HT201666

Probably sold with a HDD and was third party upgraded (or home upgraded) to a SSD.

The linked article is specificly about this problem, and does explain how to turn the feature off....
Title: Re: So much lowend even a solid state drive skips
Post by: Jim McKeveny on January 23, 2016, 09:46:21 am
The linked article is specificly about this problem, and does explain how to turn the feature off....

This is why I prefer dedicated, purpose-designed gear in mission-critical positions. Open, flexible, multi-purpose platforms by nature offer unforeseen misfire possibilities.
Title: Re: So much lowend even a solid state drive skips
Post by: Lyle Williams on January 24, 2016, 05:04:11 am
Regardless of the gear, you have to check it and test it.  Rehearse the show/setup.  Once your system can be trusted to be infalible, still "Have a Plan B."
Title: Re: So much lowend even a solid state drive skips
Post by: Lyle Williams on January 24, 2016, 05:08:16 am
A general purpose platform like a PC/Mac can be great.  If you need it to work you need to dedicate it to the role.  It can't be your random-web-downloads box; don't upgrade anything on it until you are sure of continued compatability.  The next OS upgrade might be a cool thing to have, but if your software stops working or behaves differently, you're screwed.