Safe way to disconnect speakers from a live amp

[buggyboy]

Is there a safe way to disconnect speakers from a live amp?

The main issue I see depends on the type of connector. a 1/4 inch connector would reverse polarity as it is removed. that isn't an issue with an xlr or speakon.

what other issues am i overlooking? it feels like this isn't safe, but i do't know why.

thanks.

[buggyboy]

I thought i'd piggy-back a small related question.

Is it dangerous to connect an 8ohm system using the 8ohm and common spring terminals on an amp...and also connect a 70v system to the 70v and common terminals at the same time?

[tropicalfish]

If it's Neutrik Speakon, it's safe. XLR... I don't think those are used anymore for speakers. I've seen 1/4" disconnected with the amp on without any problems, but I'd definitely avoid it because the tip and ring briefly short when being pulled from the jack.

What do you mean by common spring terminals?

[buggyboy]

So provided the amp outputs simply disconnect (i.e. no shorts, cross connections, etc) it won't harm the amp to go from driving a load to driving no load? and safe for the speaker as well?
I just want to be clear on the physics involved. my system is so cheap that it isn't a big issue, but if I ever am in the position of running a more expensive setup I want to be sure of myself.


One of my amps is an old pa mixer/100 watt amp. the outputs accept a bare wire stuck into a spring loaded clamp.

There are about 5 or so of these spring terminals. marked "common", 8 ohm, 16 ohm, 70v, etc.

To connect a normal speaker you put the + wire into the "8 ohm" terminal and the - wire into the "common" terminal.

to connect a 70 volt speaker you use + wire to 70v and - wire to common.

The question is whether you can run both at the same time, or if only one type of output at a time is safe. (I'm going on the assumption that the amp has enough output power to handle the combined loads).

[Brad Weber]

The answer is "it depends" and that really is the only answer since it is product dependent. Some amps may have no problem dealing with shorted or open loads, others may quickly let out the magic smoke. Some amps may handle multiple and/or mixed loads, others may not. And even if you know that an amp will work with mixed loads, how it does so might affect the individual outputs.

[buggyboy]

I can't say i'm surprised by that answer. So little in sound is written in stone.
I just had to ask, it might have been a simple answer. Thanks for the conclusion of the matter.

[waynehoskins]

It depends, certainly, but I'll add a few generalizations. Most pro audio amps made in the last, oh, 20 years will be fine with instantly adding/losing a load, so long as the load impedance is within the range it can safely handle. It's not uncommon to connect or disconnect a speaker live, especially if the connection is made with Speakon connectors. In high-power systems you probably don't want to do this, certainly not repeatedly, at full power since that could cause arcing and pitting of the contacts.

With the amp you describe (having both specific-low-impedance and 70V output terminals), my guess is you can only safely use one at a time. The output transformer wants to put a particular load impedance on the output transistors, and the presence of two loads on the same transformer could make the output stage unhappy. That's why these have, say, 4-ohm, 8-ohm, and 16-ohm terminals, so you can select the appropriate terminal to properly load the output stage so it's working into its design impedance. We don't have this problem with modern pro audio amplifiers because they're transformerless and have a crazy-low internal output impedance, so that changing the speaker load doesn't dramatically affect the overall impedance the output devices are looking into.

There you go. It depends, but if it's a modern transformerless amplifier with sufficient load range and open/short protection, it doesn't usually care exactly what load it's looking into so long as the input current and, what do they call it, the transistor equivalent to plate dissipation, are within tolerance. They're quite forgiving.

[buggyboy]

Thanks Wayne, my education continues.

One question. You say it's not uncommon to disconnect a speaker live... is this usually an accident? (stagehand tripping over a wire?)

[tropicalfish]

My church uses passive monitors connected to Speakon connectors in the stage pockets, which are connected to amps that are turned on with the console. They are disconnected and reconnected frequently without problems.

[buggyboy]

Thanks for the input fish


What language would I be looking for in the amp manual to indicate whether this sort of hot-plugging is safe?

[SamG269]

At one of our locations our connections come loose all the time from both the amp and the speakers and monitors. No problems so far. And Its been happening for 2+ years now.

[Les]

Originally Posted by buggyboy

What language would I be looking for in the amp manual to indicate whether this sort of hot-plugging is safe?

I doubt you'll find anything in the in the amp manual stating that it's ok to Hot swap/plug.

I don't know of any 1/4" connectors that are rated to be hot swappable. Looking at Neutrik and Switchcraft I didn't find anything specifically saying one way or the other that they are/are not hot swappable, but since you can/do technically short it out for a split second I can see why they are not rated to be hot plugged.

Speakons are specifically said to be NOT hot swappable/pluggable (same with their original PowerCon connectors).

Now, in practice it's usually fine and I normally don't hesitate to do it but you likely won't find any manufacture's endorsing it.