Speaker fuses

[Jupton24]

Hi,

 

Recently we had 2 of our Ev zx1 -90's horns break and had to get them set away for repair. I have been tasked with finding a solution to prevent this from happening again. I have seen elsewhere on google about fuse for speakers so if the volume or power goes over a certain limit it would trip. The trouble is that this sound system gets used by teachers and students that don't know how to correctly shut it down. there is 2 EV ZX1-90 and 2 EV ZX3's they come off a QSC 1450 and a QSC 1850HD I believe of the top of my head. Is there any way that I can make the system using fuses or shall I look into USP's

 

Cheers

James

[paulears]

Older EV speakers often had light bulbs inside which acted as protection, but the reason your speakers are failing is not teachers and students not knowing how to shut them down, it's squirting too much volume into them. 200W is their limit and those amps can supply more than that. However, before they fail they sound simply awful so people normally just turn them down. I assume the smaller amp powers the small speakers and the larger one does the 12" ones?

 

To be honest, at their price point repairs out of warranty are not cost effective unless there is a technician on staff who's labour is free.

 

Fuses don't really help - you need sensible people to operate them.

 

No idea what a USP is?

[Jupton24]

Older EV speakers often had light bulbs inside which acted as protection, but the reason your speakers are failing is not teachers and students not knowing how to shut them down, it's squirting too much volume into them. 200W is their limit and those amps can supply more than that. However, before they fail they sound simply awful so people normally just turn them down. I assume the smaller amp powers the small speakers and the larger one does the 12" ones?

 

To be honest, at their price point repairs out of warranty are not cost effective unless there is a technician on staff who's labour is free.

 

Fuses don't really help - you need sensible people to operate them.

 

No idea what a USP is?

 

okay, that is great to know. the trouble is the amp rack is in the same room as the sound desk so, therefore, the teachers' fiddle with it obviously now I will have to invest in a door for the cabinet to prevent this happening. They did sound awful to much bass so that made the school take them down and take them to a repair shop. they did the opposite when they sounded bad they just turned them up further. yes, the lager ones are powered by the larger amp. they originally had the larger one powering the smaller ones when I first got there that is when the speakers worked perfectly.

 

unfortunately, I did not have a say in to get new speakers or to fix them. it will still be teachers and students operating with limited knowledge.

 

a USP is an Uninterrupted Power supply as they turn the amps off constantly. without shutting it down properly.

[Jivemaster]

IMO horns go if fed a distorted signal, bass drivers go if fed too much power. If the sound is being pushed too much then something speaker will tell you (quietly!).

 

A UPS will hold the amp on with everything else til the battery dies (30 sec to 3 minutes) NOT sequence the power off. Power sequencers are available.

[paulears]

Ah understand now a ups is normally a unique selling point sp vs ps!

 

My main pa in the theatre has been powered down by flicking the power switches or killing the entire rack by the Mcbs for years. Not sure what they can do to kill speakers doing this. With students and staff doing what they normally do volume is going to be the killer because the horns in smaller units are fragile. Probably more fragile than a fuse! If you’re the technician can’t you exercise some control over these people?

[Jupton24]

Ah understand now a ups is normally a unique selling point sp vs ps!

 

My main pa in the theatre has been powered down by flicking the power switches or killing the entire rack by the Mcbs for years. Not sure what they can do to kill speakers doing this. With students and staff doing what they normally do volume is going to be the killer because the horns in smaller units are fragile. Probably more fragile than a fuse! If you’re the technician can’t you exercise some control over these people?

 

 

Yeah I am the senior technician I suppose it is just now down to the fact that I need to lock the amps away so no one can touch them and teach them the proper way of shutting it down but I don't think they will listen as we are talking 14 - 16 year olds. I guess a backup battery would be pointless as well because it get used Fridays and Tuesdays only. I suppose I can't fit it with a volume button limiter (if that makes sense)

 

Also do you know of a amp that can power the EV zx1 successfully. Ideally a one that could fit into a amp rack is apreacieted

[paulears]

I think you need to have a rethink. I've never ever had anyone put a bog standard amp on a UPS. Totally pointless. I'm also fairly sure you've got this shutdown thing out of all proportion. The speakers you have are lower tier speakers, designed for musicians with less than huge budgets. If you power them from a rack mount amp - then just turn the switch on or off.There is no need for any elaborate switch off or on system. These amps are protected and unless they are faulty they do not go bang when turned on or off, and therefore no transients to pop a coil out of the slot. Are you doing all the turn the controls down, then switch off and switch on then turn up routine. While this still may have a place on very high power systems, your's isn't. The controls on my amp racks have not required this doing for a very long time now. There are 5 in a rack - each one more hefty than yours. Whoever powers up the sound system just applies power and flicks 5 switches. That's really it. If somebody is careless and turns off the mixer before the amps, then there's a large pop. Never done any harm, because modern kit is built to take it. Powered speakers are a good thing to consider - flicked on and off trouble freely - with nobody turning things down before inserting a jack, or plugging in a phone.

 

Of course you can fit a limiter, but it's going to be an expensive piece of kit that these people will bypass. Are you thinking that they are killing the HF drivers with the loud hums and cracks of connecting things up with the volume turned up, or are you just worried about the volume.

 

As chief technician, why not simply make up some pads? you only need a handful off resistors and you can make the amps incapable of being as loud as they can be - BUT - if you do this, the users will complain.

 

If you have to put things in cupboards to stop staff and kids abusing them, you have more than a volume problem. It's a management problem or an attitude one.

 

If the people abuse the system, it's because it's the wrong system, or because they need technical input to keep them going. If you don't have time to supervise the use, then no teacher is going to put up with equipment meant to be used being hidden away. This kind of technician vs teacher way of working went out years ago in the places I have experience of. If the equipment is unsuitable for their purpose, then somebodies budget needs to fund bigger and better ones, or you throw them away if you cannot fix them.

 

I'm really sorry, but I don't get this at all. Crazy ideas about UPS on amps. Look at this logically - they are designed to prevtmn things like computers crashing when the mains is removed intentionally or accidentally. If the mains is removed from an amp - it goes quiet and no damage is done to anything. What on earth are you expecting a UPS to do differently?

 

Personally, I'd just buy a batch of replacement HF drivers, stick them on the shelf and fit as required - if you use one a term, then that's probably cheaper than you spend on new lamps for old lights!

 

Modern kit is designed for incorrect use. People like Thomann give these products very long warranties. If they died regularly from being switched on and off, they'd stop selling them.

 

The usual school technician's way of doing this is to tell the head of department there is no more in the kitty and if X blows up one more speaker, then there will be no more music till the next budget fund release.

 

Are your members of staff completely thick? Surely when they blow them up, THEY know exactly why, because they were there. Get some extra budget and buy better and louder ones, don't start imposing crazy start ups and shut down systems that nobody outside of education really does for something so simple. In the pro world we do have power sequencers to do this kind of thing when required, but for an amp and a pair of speakers, it's just not needed. The QSC1450 is open and short circuit protected, very quiet and mine starts and stops by killing the mains totally silently - it just comes on a few seconds later and sound comes out. It's never annoyed by having the speaker disconnected when running hard and apart from making me jump does no harm. Over excursioning speakers by applying full power suddenly has happened to me once in my career, but I've killed quite a few by overdriving.

[Jupton24]

Yeah I agree I think I was going a bit above what is actually needed. It was just the IT person said a UPS would be useful but now like you said it is pointless any way. Thanks for the help

[laolu]

As jivemaster seems to suggest, add a power sequencer, if you think turning and and off amps is the problem. We have one on our theater PA, with just one button for turning the system on and a different button to turn it off. Never had a problem from that point of view.

 

If your HF drivers blow regularly, then the PA-users (= students, teachers) are responsible. Maybe invest in something like a dbx driverack, even if you only use its limiters.

 

My 2 cents

[john-sp]

I used to encounter this problem in schools, mainly with JBL Control speakers, The EV ZX1s seemed harder to pop, but determined schools could still manage it. The issue was teachers/students not understanding that the knob on the front of the amplifier is an attenuator, not a volume control. There would be a complaint that the sound in the hall was too loud, so somebody would go in and turn the amps down to make it quieter. The next time the system was used, somebody would realise that it wasn't as loud as last time, and whack all the gains on the desk up to get it to the same level as before. This would result in a virtual square wave being delivered to the speakers, which eventually would take out, more often than not, the HF drivers.

 

I spent many a training session in schools trying to make people understand that turning down an amplifier doesn't make it quieter, just makes it harder to go as loud as before.

[ojc123]

Many years ago we had this problem in school. As has been said above, the best answer is to get better speakers. For a while I had a stock of cheap horns from ebay and just regarded them as disposable. In fact my first visit to the Blue Room in 2005 was to find out what to do about a broken HF unit.

 

My argument with the bean counters was that replacing the horns every month or two in parts and (my) labour was soon going to cost more than getting more reliable speakers.

 

I've found powered speakers less prone to this possibly because they're more matched up speaker to amplifier and/or they power on and off more effectively? We've had a pair of these for about ten years and they put up with all kinds of abuse.(Other makes and suppliers are available.)

[timsabre]

Powered speakers usually include limiters so are much harder to destroy, but that's only any good if you have budget to replace the whole shebang.

[sunray]

1575388221[/url]' post='578946']

Many years ago we had this problem in school. As has been said above, the best answer is to get better speakers

 

I've found powered speakers less prone to this possibly because they're more matched up speaker to amplifier and/or they power on and off more effectively? We've had a pair of these for about ten years and they put up with all kinds of abuse.(Other makes and suppliers are available.)

 

Ive. Found the opposite is true. An amateur youth drama group were forever popping tweeters and I lent them an old pair of single 12" cabs with no hf units.Schools and powered speaker have always been a recipe for disaster, especially if it's a portable system.

[ojc123]

Ive. Found the opposite is true. An amateur youth drama group were forever popping tweeters and I lent them an old pair of single 12" cabs with no hf units.Schools and powered speaker have always been a recipe for disaster, especially if it's a portable system.

I can see that would work in a different way. If there isn't a tweeter to pop then that solves the problem. I haven't found the powered speaker to be a "recipe for disaster" but everyone has different experiences.

 

Edit to remove duplication.

Edited December 4, 2019 by ojc123

[Jupton24]

Thanks for the help everyone. I don't actually have a budget get to update the speakers. Powered speakers would work for me as they are so high up in a sports hall and it has cabling for passive layed beneath the floor and up the wall. I am going to look into the drive rack a bit more as it does come with quite cool features that is not there currently e.g fbq and eq. But reading what you all say has helped in actually identify the problem. It was originally fine and then someone whacked the amps up therefore the speakers made terrible noise. They left them for a while at it and obviously the HF broke eventually. When it broke they just wacked the amps up even further. (This is the teachers I am talking about)