Solving Speakers Popping Problem

[Manheim]

This isn't a homework problem or anything, but a problem plaguing me at home.

I have a set of speakers that pop occasionally. The pop is uniform across all satellites and subwoofer of the speaker set (there are 5 satellites and 1 subwoofer). The speakers are 500 watts RMS, 1000 watts peak.

The speakers pop whenever the mini-fridge in my dorm room turns on or off. They also pop if I have the speakers at home and I turn my fan on or off, or from one mode to another.

The fan and mini-fridge are on the same circuit. In the case of the fan, it's in the same surge protector. The speakers still pop if I turn the fan on/off when it's plugged into a wall outlet on the same circuit.

Some people have told me electromagnetic interference may be causing it. To test it, I plugged the fan into another circuit in my house through an extension cord, and placed the fan where it normally rests. I turned it on, and the speakers don't pop.

The speakers don't pop at all if they're turned off.

My suspicion is that there's too much power being drawn from all the devices on the current circuit, so how can I alleviate the popping? Which would be more suitable, a backup power supply (UPS) with automatic voltage regulation or a home theater type power conditioner?

And if my speakers pop when I do something as simple as turning a fan on, why aren't my other peripherals affected? Say, the other two computers on the same circuit. Could the sag in power when I turn my fan on be harming these components?

Thanks for any insight.

 

[chroot]

You're probably not drawing too much current from the circuit. If you were, the circuit breaker would open. It's also not caused by (steady-state) voltage drop on the circuit, so don't bother

Devices with large motors (like fans and fridges) typically have large inductance. When you turn them on and off, they'll produce a voltage spike on the circuit. It's normal.

Your audio amplifier (it's the amp that's popping, not the speakers), on the other hand, appear to have a very poorly design power supply. Your other devices (including the computers) probably have much better power supplies.

Your best bet, other than isolating the audio amplifier on another circuit, is to use some kind of a power conditioner, which should smooth out the spikes. A typical "surge surpressor" is not going to kick in until the spikes reach thousands of volts, so they won't help any, by the way.

- Warren

 

[Cliff_J]

The power conditioners come in a variety of configurations, from the 'surge protector' kinds with 5 cent MOVs that offer a tiny amount of protection for a tiny amount of time, to autotransformer types with multiple taps that switch to adjust the in/out ratio, to active switching power supplies that will generate a pure sine wave at a fixed voltage.

Price goes from a few dollars to hundreds to a thousand or more. I highly question marketing claims of automatic voltage regulation, there is too much grey area allowed to those who put the labels on boxes. To do it right is going to cost money, its not a 5 cent upgrade.

It would be cheapest to either find new speakers with a better power supply in the amplifier, or if it uses an external power supply, find another one with better output regulation that supplies the same volts/amps and that would work too.

By the way, we could also guess that if you used a UPS and had to actually use it on battery power, that the speakers would buzz like mad. Again, its the power supply for the amplifier not doing such a great job of supplying clean power. But for an amplified computer speaker, price is all that matters almost all the time, people can't discernt that quality difference until they get the product home.

 

[DaveC426913]

Actually, this raises a question for me, and I apologize in advance for hijacking the thread.

How good a job do power supplies for computers do (they're usually ~$30)? Are they a waste of time? As someone who knows about this stuff, what do you do/recommend to do an acceptable job of protecting your computer?

 

[turbo]

Manheim, do the speakers pop with no input device energized? In other words, if the amplifier is on and idling, do the speakers pop when you energize the offending devices? If not, you should start checking the grounds of your input devices (turntable, CD player, radio receiver, etc). Amplifiers are designed to amplify tiny input signals, and any little bit of static riding on an input signal can turn into a big "pop" if you've got the volume up. (and at 500W RMS, you may be the type to turn the volume up a bit).

If I were in your situation, I would unplug every input device from the amplifier, turn it on at a modest volume, and turn on the fan, etc. If there is no "pop", then add input components back in one at a time until you find the one that is causing the problem. I hope this helps.

 

[turbo]

Actually, this raises a question for me, and I apologize in advance for hijacking the thread.

How good a job do power supplies for computers do (they're usually ~$30)? Are they a waste of time? As someone who knows about this stuff, what do you do/recommend to do an acceptable job of protecting your computer?

I used to have an office in a building that browned-out and surged frequently when the photographers turned on their floodlamps. I lost several PC power supplies (and once, a HD and drive controller) until they got a dedicated circuit for their lights. The PC power supplies are OK if you feed them a diet of clean steady power. I have not lost a power supply in my home computers, despite being out on a long rural line with frequent interruptions - I use Blackout Buster UPS, and it seems to do the job.

 

[Manheim]

If I were in your situation, I would unplug every input device from the amplifier, turn it on at a modest volume, and turn on the fan, etc. If there is no "pop", then add input components back in one at a time until you find the one that is causing the problem. I hope this helps.

The speakers are actually 5.1 PC speakers -- the Logitech Z-5500's to be specific if anyone's interested. The amp, subwoofer, and speakers are all in one package.

I disconnected my only input line to them, my computer. The amplifier still popped when I turned my fan on and off. I suspect it probably is a poor power supply in the amp then. There's no grounding plug on the speaker's power plug -- does that matter at all?

I'm really just interested in giving clean power to my components, and perhaps giving me some time to save files and shutdown my computer if a power outage were to happen. From what I've gathered, a high end UPS with pure sine wave output would do the job. Given, it wouldn't be cheap, but I like to buy expensive stuff anyway. Furthermore, I wouldn't run the speakers off of battery power, so the "buzzing while on battery power" issue isn't an issue.

I guess my next question is, how powerful of a UPS would I need? Of course the pure sinewave output -- but what rating?

Often there are outlet plugs for battery backup & surge protection, and surge protection only (no battery) on a UPS. Does the VA rating only apply to devices on the battery backup outlets?

Would the pure sine wave power output come out of the surge-only outlets, or the just the battery backup & surge outlets?

If I were to have the speakers plugged into the surge only outlets, would I be straining the UPS in any way by having 500 watt speakers on a UPS that only supports X watts? (X being enough watts to power my computer and monitor through the battery backup outlets)

Sorry about the massive barrage of questions, but when it comes to UPS's, the industry starts getting very vague.

 

[Cliff_J]

A typical product market is vague, it makes it easier to sell product. Watch the episode of Seinfeld call "The Move" where Jerry needs to get his car fixed. In discussions with George, they essentially say that a honest auto mechanic is more valuable than other things, the car is just too mysterious and its too easy to be sold on something you don't need when you don't understand what you need or want fully.

Lets say you just wanted a decent surge supressor, that's easier. Forget MOVs, you want something with reactive components (coils and capacitors) acting as a LP filter on the power lines, I've got an APC brand that has this feature, only $30, and while it may not be enough at least its a step in the correct direction. I've visited a home with lightning damage (neighbors too, lightning hit power transformer) where the homeowners had to replace coffee makers or curling irons and other mundane devices plugged in at the time. But the Panamax brand filter on the home theater, after replacing it, had protected all that gear by taking the hit and preventing the transmission of that surge.

I have a friend who has 3 TiVos and the one not protected by a Panamax lost its modem after a thunderstorm (big deal on a lifetime subscription box, $120 to fix).

While on anecdotes, my neighbors have had to replace their linksys router, dsl modem, and other small items after a recent thunderstorm, and I've had a my HVAC control box fry and a refridgerator blower fan coil open up as well (seems like a freak occurance). But my computers and TVs are all protected with Panamax devices, and I have reasonable certainty that even the inexpensive Panamax devices will live up to their reputation to sacrifice itself like a fuse should it need to in order to protect the gear plugged into it. The MOV variety might offer a tiny bit of protection, but are really bad because there is no indication when it stops protecting which means they are like rolling the dice in comparison.

The Furman types are suppossed to be sacrifice free, but are a little spendy.
http://www.musiciansbuy.com/Furman_PL8II_Series_II_15_Amp_Power_Conditioner_with_Free_PL8IIKIT.html

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On to UPS devices. Most are inactive 99.99% of the time, they only kick in when there is an event that means they are needed like the voltage drops too low or too high. So when they do not have the circuitry activated to create a nice sine-wave output, they just simply switch regular mains power right through them. So when not on battery power, they are just an expensive surge strip.

Only a special UPS will be a 100% active device where your equipment is powered off a circuit-created perfect sine wave output. Some hints are it will have a heatsink because it will generate heat continously and its pricetag will be too high to be practical for all but industrial markets. These are rare beasts typically found in datacenters, like one I used to work in where the size of the UPS was on the order of 15kVA! There was an entire wall of large truck batteries, 480VDC!

And think about it, if you could find one, only the powered outputs would be circuit-created, the surge outlets are again just a cheapie surge strip.

You're likely going to have better luck looking for a power line conditioner (or regulator, marketing messing with terms again) with good filtering and be done with it. Finding a unit with active regulation of a sine wave output with batteries as a UPS is going to be really challenging, maybe near impossible at a price you'd be willing to pay. Caveat Emptor - unless the description is explicit, assume its just the same stuff as everyone else.

This model is only a multi-tap but in theory is a repected way to cleanly power audio equipment that otherwise can be noisy. And is going to be much cheaper than a fully active device. And I'm impressed they included a zero-crossing detection circuit, I've got an Alpine H701 DSP processor in my car and it has zipper noise that seems to be caused by it ignoring zero-crossing when changing volume levels.

http://www.musiciansbuy.com/Furman_AR1215_Voltage_Regulator_AR1215AR1215.html

If you're ambitious, you could DIY it:

http://www.dansdata.com/diyups.htm

That's a lot of money to avoid a pop! I would just run an extension cord myself, if a second circuit is at all available.

 

[Manheim]

Cliff,

Thanks for your in-depth reply. I learned quite a bit, but I still have some questions.

Are all Panamax surge protectors made with reactive components? How can I tell the difference between a quality surge protector and something that uses MOVs?

What's the difference between the two Furman devices you showed me? The first seems to be an expensive surge protector but is marketed as a "power conditioner" which leads me to believe that it smooths the power output. However, the second more expensive Furman you linked seems to market the smooth power output more prominently and is quite a bit more expensive.

I'd pay $130-$200, but not $500. And for $130, I'd like to get a battery backup in there too, for my computer components.

 

[Cliff_J]

The second Furman has more filtering. They are spendy though, I'd like to either see like an ASTM standard and the test data or just experiment myself before spending that much, and then again wonder why I bought such cheap audio gear I'd need one as well if I was doing audio recordings for a living.

The APC one I bought has a picture on the box of the components. I don't know if all the Panamax protectors are using reactive components, but do like to believe that at least if they are using something cheap like MOVs that they continue their philosophy that the protector is sacrificial. But as they say, ignorance is bliss, I keep it that way because I'm far too cheap to buy their large $200 units all around the house. So I rationalize they must work better than some $7 no-name, that's my story and I'm sticking to it.

I have a friend who is an EE at an industrial controls place. He thinks its all marketing as far as any lighting protection, he has done a post-mordem on some of the componets that have been subjected to tests involving the closest we can come to copying to a lightning strike (still only like 1% of the real thing). In short, its just a lot of energy to dissapate, and since it has to go somewhere it finds pathways anywhere and everywhere. That's maybe a worst-case scenario, but there'a also a big difference between a direct lightning hit and a secondary effect from that strike that covers a larger area with less energy.

I did loose a computer power supply while on my old APC surge strip a few years ago, but it was a home-built machine so I question the quality of the power supply in the first place. Bad part was it took out nearly everything, the motherboard and PIII800 chip, HDD, RAM, etc and all that still worked was the NIC and video card.

I use a $18 Panamax for power/phone protection around the house and after that a $50 UPS (750VA on sale) for battery backup for the computer. If there's a bad storm, I unplug both the phone and power plug from the wall, just in case, just like only using cordless phones.

And my cheapie Altec Lansing speakers don't pop when other devices on the circuit turn on/off or buzz on battery backup, but they make a heck of a pop when turned on/off. That's the amplifier circuit though, not the power supply. Cheap seems to means you pay a price in a different way (like quality) instead of dollars. Really good engineering is about hiding the difference in quality, because cheap is pretty much a fact of life in manufacturing.

 

[rogerperkins]

I believe you could just solder a small capacitor across the terminals of the speaker, as a low pass filter, though I don't know what size would be good, perhaps 1 pf.

 

[Wetmelon]

I believe you could just solder a small capacitor across the terminals of the speaker, as a low pass filter, though I don't know what size would be good, perhaps 1 pf.

Of course, you'd have to do it retroactively by about FOUR years. Check the date before you post :/