Speaker Protection Suggestions

[ojc123]

Or a 12V lamp / Polyfuse wired in series with the tweeters.

 

James.

 

I like this. I've seen old speakers with the lamp in them many years ago. It hadn't occured to me. I could have the lamp /fuse located at low level so I could replace it easily if it pops. How could I work out a suitable fuse rating or lamp size?. Or just trial and error?

[J Pearce]

We have 7 rooms at our school with iPod inputs in the playback racks, and I've never observed damage from mini jack popping. I wouldn't be too concerned about it.

 

The main one to watch is power up in my experience. Power down popping largely depends on the quality of the mixer and amp, but power downs tend to be more of a thump going down to dc, rather than a pop as things get up to speed.

 

Our dance studios use Yamaha amps that soft start and seem to catch power off pops, our music rooms use hifi amps that isolate the outs with relays before power off and the larger more complex theatre rig has a power sequencer built into the control system that Ikon AVS made for us. The setup in our main hall uses active speakers that soft start and shut down cleanly.

[vlfaudio]

The trouble with the light bulb solution is it will increase resistance under high load and this will have the effect of lowering the x - over frequency potentially below what the tweeter is designed for. I worked in a venue previously with light bulb fuses in the wedges. The wedges were regularly driven hard and it soon became apparent we were spending more on replacement bulbs than we had been on replacement diaphragms. Putting in suitably over specified drivers solved the problem completely.

[laolu]

We have 7 rooms at our school with iPod inputs in the playback racks, and I've never observed damage from mini jack popping. I wouldn't be too concerned about it.

 

Same here: Our students often use their iPods/pads/phones or those tiny MP3-players to play music over our PA, and it usually doesn't plop much. We're dealing with line-signals here anyway. The problem occurs when a notebook is plugged in and I was wondering why. I came to the conclusion that anything connected to a power-supply (like the notebook) causes the nasty plug-in / plug-out pops.

[J Pearce]

A transformer isolator might clear up laptop popping which is probably due to a dc potential between the non earthed laptop and the earthed mixer.

Most of our playback racks have a transformer isolator on the mini jack line, though mostly to alleviate the horrendous ground loop whine from dell psus.

[chelgrian]

Most of our playback racks have a transformer isolator on the mini jack line, though mostly to alleviate the horrendous ground loop whine from dell psus.

 

That's not actually a ground loop it's a craptacular switch mode power supply leaking RF noise into both its inputs and its outputs.

 

Even high quality PSUs suffer from this, for example I've had a problem with a convoluted setup involving several Firewire devices attached to the same computer where an A/D converter in the system took exception to some ultrasonic noise produced by the PSU and produced clicks, running off battery power solved it.

[ojc123]

I'd already planned to put an isolator in to prevent the noisy PSU problem. I have them in the main system already because all sorts of visitors turn up with laptops. They do reduce the pop quite a bit as a side effect.

[Doug Siddons]

This might help http://www.tweetaguard.com/ I think CPC stock them

[ojc123]

This might help http://www.tweetaguard.com/ I think CPC stock them

Those look good for this purpose.

 

I've tried the switch it all on at the mains approach. I chose the amp with a slow start and that seemed to work. The start up was next to silent.

I'll fix the mixer so that phantom can't be switched on.

I'll make the 4-way hard to get to and that should stop interference from the inept.

If I have isolators and the tweetaguards it looks fairly safe.

 

It won't be beyond the wit of the PE department to break it but I've tried.

Thanks for the help so far.

 

Final thought

I'm thinking of using the Behringer 4 channel compressor as a limiter for the inputs from laptop and the iThings. That way if they put the volume up on the headphone sockets it won't clip the inputs. Is this a good idea/pointless/risible?

[d_korman]

Or a 12V lamp / Polyfuse wired in series with the tweeters.

 

James.

 

I like this. I've seen old speakers with the lamp in them many years ago. It hadn't occured to me. I could have the lamp /fuse located at low level so I could replace it easily if it pops. How could I work out a suitable fuse rating or lamp size?. Or just trial and error?

 

12V lamp won't work for fast transients though, will it? When cold, the lamp will have quite low resistance, <0.2ohms. The thermal inertia of the filament means that its resistance won't increase fast enough to protect the tweeter - it's more designed to protect against voice-coil overheating due to sustained high levels.

[jamesperrett]

12V lamp won't work for fast transients though, will it? When cold, the lamp will have quite low resistance, <0.2ohms. The thermal inertia of the filament means that its resistance won't increase fast enough to protect the tweeter - it's more designed to protect against voice-coil overheating due to sustained high levels.

 

As I understand it, the main problem is stopping the voice coil of the HF driver from getting too hot and deforming or melting. So the trick is to match the thermal characteristics of the bulb with the thermal characteristics of the driver. While 12V car bulbs are often traditionally used, there may be more appropriate alternatives for a given situation.

 

James.