Why Did My Speaker Blow!

[stardust 0]

Hi all, I'm new to the forum and also new starting up in the digital DJ market -

 

I played a gig last week, which was in a smallish town hall - It was a small gig where the music was fairly loud

(for a town hall - they have the traffic light system!!)

 

I have brand new kit comprising of the following:

 

- Behringer EP1500 Amplifier (700 + 700 watts)

- Skytec SKY300 15 inch Speakers

 

The rest of the kits is Macbook pro, traktor, mixer etc

 

Towards the end of the Gig one of the speakers blew!! with a burning smell...

 

Before i ask Why? i did notice that one of the sound channel dials on the Amp was turned up nearly full tilt

and the other one (right speaker) was set half way (Lesson No 1 - during the panic of setting up within half an hour always check your amp setting in case they have been fiddled with)

- Could this be why it Blew????

(i did not realise that the amp channels were out due to controlling the volume on my mixer + the output sound sounded fine to me)

 

Secondly i was using bannana connectors on the amp and a screw on connector on the speaker where i stuck the live cable into - In hindsight this does seem pretty bad for a live gig setup - could this be why???

 

Any advice or reasons/clues to this problem would be appreciated, many thanks.

 

p.s. since this i have purchased a better brand speaker set with speakon connectors

I am just very paranoid that this will happen again especially when this Gig wasn;t even that loud!!

 

 

 

 

 

 

 

[spinner 0]

I don't know a lot about Skytec equipment but I believe that the cabinets you were using have a 300 watts maximum rating, which probably means peak. In which case the rms rating is likely to be 150 watts. I'm assuming the impedance is 8 ohms.

 

The EP1500 produces 280 watts per channel rms at 8 ohms.

 

If the gain on one channel was too far up, that's the likely reason for the failure.

 

Coincidentally I read a post on another forum where someone used the same cabinets for a wedding but both HF units had blown right at the start, leaving him with bass only. He couldn't carry on and had to refund his fee.

[MobileDamo 0]

to me it sounds like the speakers couldt handle what was coming out from the amp.

 

theirs an amp and speaker tuteriol on this site some where it gives you basic info on choosing the right speakers for your amp..

 

many thanks

[dh140770 0]

He couldn't carry on and had to refund his fee.

 

Forget the fee. He also probably ruined the wedding party. This is why it is imperative to carry backup equipment for all aspects of the show, but PRIMARILY the sound (and sources).

 

Sorry to sound harsh, but if you were on the receiving end of this on your big day, how would you feel ?

 

[Ste Owens 0]

I had these speakers a while back and was using a peavey amp with them and worked fine. Problem is with bannana connections when you put them through if they touch they create a circuit and ultimately blow the speaker. I had this once but luckily I had my spares with me. That is one other reason but its probably you done it with the amp.

 

Ste

[BK Sound 0]

Do you know which amplifier channel blew your speaker, i would hazard a guess it was the channel that wasnt turned fully up...

 

The level/volume/gain controls on a power amplifer are attenuators not volume controls

They are designed to be run flat out, fully clockwise unless you dont have a mixer inline, which of course you do.

 

The reason speakers get hot is rarely from pure amplifier power but more often from a continued distorted signal, or square wave distortion as its sometimes called.

 

What happens is the coil of wire inside the magnet of your bass driver gets hot if it is receiving a 100% strength from the amplifier, cheaper drivers do not have good ventilation so heat builds up pretty quickly, which heats and distorts the coil giving you the horrible scraping sound as the coil rubs against the side of the magnet.

 

This constant heating of the coil is caused by the mixer outputting a distorted signal by having the levels so high to try to achieve a loud sound, if instead you set the amplifer to zero attenuation (ie full up), you will not have to drive the mixer so hard, therefore reducing the chances of outputting a nasty distorted signal to the power amplifer, reducing the chances of speaker burnout.

 

However there are other reasons - sustained microphone feedback, poor mains in amplifer, badly connected cables causing electrical spikes in the system, and of course a faulty amplifer.

 

The rule of thumb in the pro pa industry is to have twice the amplifier your speakers require...if your speakers are rated at 250w rms (NOT PEAK/PROGRAMME) then use a 500wpc rms amplifier.

I regularily run 250 watt speakers off 2000 watt per channel amplifiers without problems so i know that rarely does pure power cause driver overheating issues.

 

 

Also (belt & braces)

 

Get yourself a volume limiter to avoid a nasty signal ever getting to your amplifier at all...i use a Formula Sound AVC2 - amazing bit of kit, it automatically monitors the levels coming out of your mixer and reduces them if they stray too high, its so good it allows me to hire out system to anyone without me having to babysit it all night, it cannot be bypassed, it is hard wired in a rack and has no user controls.

Details Here Formula Sound

 

These are expensive units but they occasionally appear on Fleabay for about £100....a very very good investment if you keep blowing drivers it will soon pay for itself.

 

 

[Daniels Mobile Discos 0]

Dont mean to but in but what do u advise I have for my spare set of speakers or do i realy need them ?

[Ste Owens 0]

Daniels Mobile Discos Posted Today, 08:23 AM

Dont mean to but in but what do u advise I have for my spare set of speakers or do i realy need them ?

 

Yes you do need a spare yet, what if yours fail at a gig? You cant say whoops sorry gears failed time to go home. Ive had this my speakers didnt work but luckily I had a spare set of 300w speakers which done me ok. I think someone mentioned in recently in an earlier post of yours. You wouldnt like it if the DJ messed up your wedding day by not having any sound.

 

Ste

[BK Sound 0]

Its not really practical to carry a spare of everything, you just need to be careful with your gear, and dont be tempted to turn everything up just because someones moaning its not loud enough, a clean sound at lower volume sounds way better than a loud, distorted and eventually blown system ever will, treat it well and you'll get years of service from your gear.

 

If you're really worried about spares i'd have a pair of speakers & an amplifier, see if you can pick up some used or cheap speakers, ebay or some boot sales/secondhand stores are good sources (listen to them with one of your cd's so you know if they sound "right" before buying them - make sure they are playing bass (bass, bass drum & low sounds) midrange (vocals, guitars) and treble (cymbals & high sounds).

If you can get some active speakers (built in amplifiers) this saves space, £250 will get you a pair of 250 watt active speakers new, less used obviously.

 

Having extra gear also means you can play in bigger rooms if required, or have some monitors for yourself to mix with.

 

 

I dont want to recommend a brand name to you cos i'm an equipment retailer & i sell lots of brands at various prices, obviously i would be biased towards the brands i sell...... if i HAD to recommend a few brands i would say Funktion 1, Turbosound, D&B, EAW, Martin Audio, Meyer, Nexo or RCF but these are top dollar speakers costing thousands of pounds, there are lots of less expensive brands suitable for various requirements, like Carlsbro, Skytec/tronic, W-Audio, Kam etc etc which would be fine for you, please ensure you do your research by reading online user reviews before buying.

 

Guys can anyone else help Daniel out with specific budget speaker recommendations?

 

 

[spinner 0]

Forget the fee. He also probably ruined the wedding party. This is why it is imperative to carry backup equipment for all aspects of the show, but PRIMARILY the sound (and sources).

 

Sorry to sound harsh, but if you were on the receiving end of this on your big day, how would you feel ?

 

 

It is, of course, imperative to carry back-up equipment.

 

Although I've never had to use them, I carry spare speakers, amp, CD players and mixer.

[Bolan-Boogie 0]

 

 

Guys can anyone else help Daniel out with specific budget speaker recommendations?

 

If your on a budget i think its been widely debated here that the Class D stuff is excellent for little cash.

I'm going to stick my neck out here and state also the Soundlab range have improved immensley over the last couple of years.

 

I run a pair of 15 tops and 15 inch bins Active / Powered (Studiomaster VPX range) on my main show. But about 10 months ago we bought a pair of ACTIVE /POWERED Soundlabs for samller gigs / 2nd show/ backup

 

Here

 

http://www.djkit.co.uk/product.php?id=1175&cat=237

 

http://www.discostudio.co.uk/images/shopimages/1558.jpg

 

Got to be honest these had a real hammering over the xmas and stood up to everything 250 watt RMS and sound excellent !!!

 

There's a guy over on the Red Forum who repairs kit for a living (grahame, username Sound Shop) and he reckons the soundlab amps are as robust as hell !!!

Edited January 27, 2008 by Bolan-Boogie

[stardust 0]

BK Sound -

 

You mentioned the following about the power Amp -

 

"They are designed to be run flat out, fully clockwise unless you dont have a mixer inline, which of course you do".

 

Just to confirm - the channel 1 & 2 dials on the Amp should always run fully clockwise (at full power)??

 

I thought they were treated as volume and i was leaving them both half way - sorry if i am being thick!!!!!!

 

Once again thanks for all the great help guys

 

[Andy Westcott 0]

The speakers burnt out because you ran them too hard - no magical combination of level controls or distortion. They just couldn't dissipate the wattage without damage, plain & simple.

 

I'd suggest a far higher rating of speaker to be able to accommodate a bit of abuse - in this case preferably higher rated than the amp, or I can see you getting the same problem again. (puts on armour in readiness!)

 

Got no suggestions though, as I build my own speakers and don't really know much about what's commercially available ready-built.

[superstardeejay 0]

Its unlikely that clipping the mixer alone will damage your speakers, but clipping the amps certainly will..its a totally different thing.

 

If you can't calibrate your mixer output levels to match your amp then position your amp somewhere so you can keep an eye on the peak lights on that. It isn' square waves that damage speakers...most 80's synths for example generate either square, sine or sawtooth waveforms. It's when the amplifiers output stage clips, this allows large, broad chunks of low frequency or DC current through the speakers which the impedance can't regulate so the dissipation sky rockets.

 

For the non-technical, you probably ran it too loud...

 

 

[BK Sound 0]

If i can defend my comments for a secnd please....

 

By square wave i wasn't referring to an synthesized audio generated signal i was referring to a constantly clipped signal waveform.

 

Copied from Sounds Live Website

 

DC Burn (Direct Current Burn) is where the user is misusing either the amplifier stage or the mixing desk output stage. In most cases, this fault is caused by the amplifier ‘clipping’ the input signal due to the user trying to get more out of the amplifier than it will give. This causes an increase in input level, therefore a larger sine wave. If this sine wave is pushed too hard, the amplifier will ‘clip’ (A red light is normally an indicator of this) the top and bottom of the wave and produce a square wave output which your speakers don’t like. At the peak of a sine wave, the voice coil of the speaker is pushed out and therefore, if a square wave is produced (by clipping the amplifier) the voice coil is spending more time out of the gap than it would like. This leads to a poor heat distribution through the magnet which overheats the voice coil and burns it. In the case of DC Burn, you could, as long as your speakers will handle the power, move to a larger output amplifier in which you have more headroom, and less chance of ‘clipping’ the signal. As a loose rule of thumb, in the case of professional speakers, your amplifier should give an RMS output rated higher than the RMS rating of your speakers. In some cases you should double the power to give plenty headroom. If you are unsure, your PA Dealer should be able to confirm this. If budget is a concern, then there are options available that you could use to lessen the chance of your amplifier clipping. These are called limiters, and are available from manufacturers including, Alesis, Behringer and Samson , among others. It must be stressed that these units only work if they are set up correctly and the user doesn’t attempt to get that “little bit more”!

 

The other posters are also correct in what they say regarding speaker power...also quoted from Sounds Live

 

Signal Burn is caused by the amplifier in use working fine, but the user attempting to use more power than the speakers are capable of dealing with. A knowledgable PA dealer will be able to match the power of an amplifier to your speakers (or vice versa) to stop this happening.

 

So both a correct & clean signal path plus a matched amplifier & speaker system is crucial.

 

Just buy the best you can afford, cheap things are usually cheap for a reason.

[DJ Marky Marc 0]

We have done this topic over and over.. and there still seems to be some resistance from people to spend money on amps and speakers that are correctly rated for the job in hand.

 

you can never have too much sound.. thats why there are level controls on your mixer to turn it down..

 

you can have not enough sound.. and thats when these little topics pop up becuase the speakers cant deal with the event you were at.. if they could then you would never have had them up so loud and caused this damage..

 

any system you invest in should cope with the kind of work you do.. if you dont invest enough into your sound and as a DJ the sound is more important than the light show in my opinion.. then you will have problems..

 

avoid the bad comments, refunds and tarnished rep buy not taking on work you can not do.. if the gig is too big then hire some more sound...

 

Quality PA speakers normaly work at there best with amps rated arround 2x the RMS of the speaker.. forget peaks look just at the RMS and ohms..

 

Budget PA speakers dont seem to deal with this level of power so well so and amp 1x to 1.5x the power of the speaker is what i would try...

 

Never run your system flat out.. even with the most expensive PA on the market if you run it flat out for a long time your asking for trouble.. bit like driving your new BMW round the M25 in 1st gear somthing will give if you keep doing it... add more sound so you dont have to run things flat out ever...

 

whilst budge speakers like the soundlab / skytecs do have a place in the market. if your running a business and your reputation is important to you then avoid them, invest in your future and get something better so you dont have to keep rebuying and fixing things or messing up peoples weddings ..

 

 

[Andy Westcott 0]

I'd just like to pick up on a technical error in the passage quoted by BK Sound:

(coz I'm cussed, see?!)

 

"if a square wave is produced (by clipping the amplifier) the voice coil is spending more time out of the gap than it would like."

 

The duration of the waveform between zero crossing points is the same no matter whether it is clipped or not, therefore this statement, regardless of the 'pedigree' of its origin, is nonsense as the voice coil is oscillating at the same frequency, clipped signal or not.

 

The above damage condition is purely due to too much power being fed to the speaker.

 

The above quoted section was in reference to a DC burn, which this is most certainly not:

A DC burn is where DC is passed to the speaker due to an amplifier fault and forces the voice coil out of the gap in one direction only and it stays there until either the amp cuts out or the current stopped my another means - nothing to do with distortion or clipping. This damage is characterised by the coil being burnt more at one end only - the end out of the cooling influence of the pole-pieces.

 

A coil burnt out by simply overloading it - clipped signal or not - exhibits heat damage fairly evenly along its length.

 

The application of a clipped signal to a speaker does not automatically damage it - as mentioned earlier many signals are hard clipped anyhow, either by design as with certain synthesizers or in the music production process. The speaker cannot tell the difference between these clipped signals of different origin assuming theyare of the same amplitude/frequency, whether from a synthesizer or a clipping amplifier.

[Dukesy 0]

We have done this topic over and over..

 

Clearly, there are new members who may not be as experienced as others. One of the great benefits of a 24/7 forum is being able to leave advice for all. So it doesn't really matter if a question is asked once or in a thousand differnet ways, if someone is looking for help, we offer and continue to help for the benefit of the profession - making a difference. :Thumbup:

 

If there is a particular post folks that one can be guided to for advice, please include the link in a reply post.

 

 

 

 

 

[datamoonking 0]

Dont mean to but in but what do u advise I have for my spare set of speakers or do i realy need them ?

Hi Danny yes you realy do need some spare speakers i have a set of peaveys as my spares now which do me great. If you need some spares look round second hand shops see what you can find. Hope it helps

[spinner 0]

 

Sorry to sound harsh, but if you were on the receiving end of this on your big day, how would you feel ?

 

 

I do hope that wasn't directed at me.

[andyw 0]

I do hope that wasn't directed at me.

 

don't think that was aimed at you spinner,more a general statement about the situation you described,dont think anyone could question your professionalism.my brother and sister was at a party nye,something went wrong with the disco,the dj had no back up gear,he went home and came back about an hr later with what looked like hifi speakers(so i'm told).and plugged them in but the music wasn't very loud or clear.the worse thing they said was he shouted over top of the decks(no mic) i make it 5 to midnight ,does everyone else make it the same.next thing they new he let off a partypopper and shouted happy new year.

[Gary 0]

I've never been a fan of the "turn the amps all the way up" idea. Unless its followed on very quickly with the advice of "unless you have a compressor/limiter fitted between the mixer outs and the amps ins".

 

OK, I'm "in" on the idea that to drive a 300watt speaker, its better to use a 600watt amp just "ticking over", working "halfway" as it were, only hearing a 50% signal from the mixer, so only giving 300watts to the speaker. But, without a compressor/limiter constantly checking the mixers output, and "instantly" reducing any signals that are "too loud", a faulty mixer pot, or shorting lead could suddenly give the amp a maximum level of sound to play - possibly damaging the speakers.

 

So...yes, go for far more powerful amps than the speakers need, but don't skimp on £80~ for a compressor/limiter as part of the set-up. Compressor/limiters also ensure that you, the dj, is able to keep the sound at a constant level all evening, even when the temporary threshold of your own hearing steadily becomes accustomed to the volume in the room and keeps making you think that the sound has got quieter and quieter, meaning that you keep turning it up and up all night - one glance at the compressor/limiter display will tell you that your output is just the same at 11:30pm as it was at 9pm...etc. £80 well spent.

[HalfPint 0]

Gary, it makes no difference if the amp knobs are all the way up or not.

 

You can drive an amplifier to full power even if the knobs are half way... all these knobs are doing is limiting or attenuating the input.

 

Especially you use a quality desk (like the ones you demo) you can easily drive the amps to full power with the knobs half way.

 

 

 

[Andy Westcott 0]

Yes - those knobs aren't a power tap. I get the impression this is a popular misconception amongst DJs.

[dh140770 0]

I do hope that wasn't directed at me.

 

Here is what you posted

 

"Coincidentally I read a post on another forum where someone used the same cabinets for a wedding but both HF units had blown right at the start, leaving him with bass only. He couldn't carry on and had to refund his fee."

 

It wasn't aimed at you, but it was aimed at anyone daft enough not to carry backups/spares where the end result is that they have to end the party early. For a wedding especially it really isn't on.