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Do digital signals (CDJs/Serato) output a special signal that can damage speakers?
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| Dojomaster26 |
So I have a friend who owns some nice JBL loudspeakers. I don't know the model numbers, but they are only a few years old, and they are large (~5ft. tall.) There is also an amplifier that runs into these, but I don't know the brand or model number of that. The tweeters/high-end cones on these speakers blew out twice recently, once at a wedding gig and again at a local gig where we had a few DJs some to spin.
Friend gets his JBLs serviced by some person who (supposedly) did sound engineering for Studio 54. When friend asked this serviceman why his tweeter went out twice in two weeks, serviceman said that the tweeters were blown because of a certain high frequency from digital signals. The serviceman elaborated and apparently said that anything digital could cause this frequency, and that the only way to avoid this risk was to use only analog equipment in shows from now on.
Let me give you some background info before going any farther: Friend is very negative towards anything digital. He doesn't like CDJs or Serato, does everything on vinyl, and even uses only analog gear to work on tracks. He's even talking about a reel-to-reel 4-track recorder that he bought and will get me the model number later so that I can look up a manual for him. I know people love their vinyl, but sometimes I feel like this guy is on a crusade against anything that isn't vinyl!
So I was a little skeptical about the serviceman's statements, especially coupled with the insinuation that this guy worked at Studio 54. I'm pretty sure that's bogus, but until I know that guy's name I can't know for sure. I went online to see if anyone else had their tweeters blown because of this digital-only signal. My Googling didn't turn up anything, and I don't remember seeing anything on any forums about it either. What I did find was lots of information about why speakers blow/overheat in general. It is recommended to use an amp whose power output matches the continuous wattage rating of the speaker, taking care not to exceed the program wattage rating through clipping or other means. I got that information from a document on Peavey's official site called "HOW MUCH POWER"
Speakers components can literally melt if too much power is pumped into them. According to an official JBL paper (called "Low Power",) they can also have issues if you are putting not enough power in because the amplifiers can produce more power than they are rated to, produce distortion, and as a result generate clipping waveforms that damage the speakers.
On none of these sites (and JBL's official site especially) does anyone state that playing on CDJs or Serato can cause harm to speakers. Everyone says that you need to make sure that you pushing the correct amount of power to the speakers by using an amp with the correct wattage.
I feel like my friend is being blinded by his bias against digital and is not being objective about his speaker issue. I'm almost certain that his JBLs will blow out again regardless of whether there are analog or digital components hooked up to them, because I have a sneaky suspicion that his amp is not matched up with the speakers and is putting out too many or too few watts.
I am not knowledgeable about speakers or PA systems in general, but I may lose gigs because of this! Can someone please shed some light on this issue before I get banned from using this guy's speakers due to using CDJs?!? |
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| clay |
my first thought is: lacking/wrong set up crossover!!!
my second though is: too weak amplifier who distorts!
these might be passive PAs which require either a passive crossover or a active crossover before the amps, which means you need separate amps for bass and treble if it does not have a passive crosover. i didnt have patience to read all your text so if you just find speaker model i can help you more with this.
if the speaker has suited passive crossover my guess is that your amp is either too weak or too old / something wrong with it making it distort. If its a hifi amp or similar it might have bass and treble knobs which people somehow but on max. dont do that it will distort.
the digital frequency destroying stuff is the most terrible bull i ever heard - its complete rubbish. yes if it clipping it will easily ruin the speakers but i doubt you have it clipping right? the same problem is for analog too. clipping AC -> DC -> burned coils.
tell me what speakers, amps, mixer you use. your problem is most likely the amp eventhough it could also be the crossover.
using CDJs or Serato DOES NOT DESTROY SPEAKERS.
man this service moron is clearly a moron. |
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| DjWoody |
What Clay said. Another thing to consider is to see if you were clipping anywhere in your chain? That means anywhere from Serato it self, all the way down to the amps. Clipping causes distortion which can blow up your speakers.
I did sound for many years and I blew up my fair share of tweeters. It was always a careless mistake.
Serato doesn't output any weird digital signal. The SL1 (SL2, SL3, SL4, or the 57, 68 or MP4) all output audio only. The digital signal it self comes from the control vinyl/control CD. It's called Timecode and it's the beep you hear if you listen to the record/cd on through mode. However, this signal is only used to send commands to the software and it's never sent out unless YOU send it out. Which out I doubt you do. No one does. |
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| Dojomaster26 |
| quote: | Originally posted by clay
my first thought is: lacking/wrong set up crossover!!!
my second though is: too weak amplifier who distorts!
the digital frequency destroying stuff is the most terrible bull i ever heard - its complete rubbish. yes if it clipping it will easily ruin the speakers but i doubt you have it clipping right? the same problem is for analog too. clipping AC -> DC -> burned coils.
tell me what speakers, amps, mixer you use. your problem is most likely the amp even though it could also be the crossover.
using CDJs or Serato DOES NOT DESTROY SPEAKERS.
man this service moron is clearly a moron. |
I didn't clip when I played. My tracks stayed in the yellow...but I also didn't babysit any of the other DJs. The amp was turned down to 3 out of 10 for the club gig, and down to 1 for the wedding.
The amp is a brand that I don't recognize, which is why I don't remember the name. We were on a DJM-2000 mixer (aka the Star Destroyer! "Which button blows up Alderan?") The speakers are JBLs. I will get the model numbers for those and the amp. I also need to check on the crossover.
Thanks guys. |
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| clay |
if i dont remember wrong theres a little gain knob on the backside of pioneer mixers too, you should calibrate that one so that the mixer doesnt play louder than a normal CD player when its on max. if that little knob is on max and your mixer is on yellow it will probably be way too loud for the input on the amp. another indication on this is that you have to reduce the level on your amp so much (1/10). i think i would put the amp on like around 12 o clock and rather lower the mixer master out or the gain im talking about on the back. its all about avoiding clipping and yellow is above 0dB just so you know. keep it at green and turn down the gain im talking about (if its there on the djm2000, it was on djm500).
edit: djm2000 seems to have a -6dB switch instead of the gain im talking about. could be smart to put that on to make sure you arent sending to loud signals out to the amp. and then rather raise the gain on the amp. and then make sure you keep it on green. |
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| Brandt Slater |
| Basically in short, have your friend go through the audio signal chain. Meaning check every single gain pot on your mixer, eq, amp, etc. Something in the line is causing the dead tweeters because its overloading/distorting the signal. Serato, Torq, 1200's, CDJ, whatever digital/analog doesn't blow up speakers. Only overloaded signals do. Truthfully it sounds like someone is driving the rig too hard. Which could be the guest DJ's. In an ideal world everything in his rig (pre speakers), talking signal only, should be the same across the board. If your setting the mixer at will say 0db, that should follow through to the next piece of gear and so on. Also you said you turn your amps down. Personally I would open the amps volume more and control your overall output from your mixer. Everyone of my amps are turned up all the way. Regardless. Every input signal routes through a Yamaha O1v96 and it controls the world from that point. |
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| DjWoody |
Every sound company I have worked with has always told me this. Amps are supposed to be turned up 2/3 of the way. Believe it or not, some older amps don't even have gains. You're supposed to set all the individual gains in your mixer to 0db and only and control the volume using the master volume of your mixer.
Also, Mics can blow up speakers. It has happened to me. Rule of thumb with mics is that you're supposed to speak loud into the mic and raise its volume until it barely touches red. Than, you lower the volume just a tad bit so you can have some headroom to work with. |
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| Brandt Slater |
| quote: | Originally posted by DjWoody
Every sound company I have worked with has always told me this. Amps are supposed to be turned up 2/3 of the way. Believe it or not, some older amps don't even have gains. You're supposed to set all the individual gains in your mixer to 0db and only and control the volume using the master volume of your mixer.
Also, Mics can blow up speakers. It has happened to me. Rule of thumb with mics is that you're supposed to speak loud into the mic and raise its volume until it barely touches red. Than, you lower the volume just a tad bit so you can have some headroom to work with. |
Over at Clair Bros, all amps go to 0db which is full open. Anything turned down is usually done at the matrix outs. We usually do the turning down in the processing as what the speaker can do. But you're correct on the mics. I usually ride the input fader, pad, or I'll compress the hell out of it. |
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| DjWoody |
| quote: | Originally posted by Brandt Slater
Over at Clair Bros, all amps go to 0db which is full open. Anything turned down is usually done at the matrix outs. We usually do the turning down in the processing as what the speaker can do. But you're correct on the mics. I usually ride the input fader, pad, or I'll compress the hell out of it. |
I've seen some sound companies do that too, and I my self do it sometimes. That's the gray area where it becomes personal preference. But at the end, we both agree to not control the volume using the amp gains. |
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| Brandt Slater |
| Totslly agree. I was taught to open up the amps and just leave them. Only adjust those as a last resort because you want every ounce of power those amps can dish out. I've seen on a few occasions actually repair jobs, where the amp blew up because the operators where trying to force so much into it and so little was getting to the speakers. Actually causing a few amps to thermal out. |
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| clay |
| thats probably whats happening here too as his levels are on 1/10, resulting the djs to push the mixer at max to get any level at all. so the output on the mixer distorts, the input in the amp distorts, resulting a clipped signal being amplified sending DC current to the speakers burning the coil. |
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| Dojomaster26 |
The amplifier that was used had a built-in limiter. The amp is rated to put out 800 watts. The JBL speakers are rated for 800 watts continuous, so I'm guessing that they can take 1200 watts peak.
I have no clue if the -6dB switch was turned on for the DJM2000/Star Destroyer. It wasn't my mixer, so I tried not to poke around it too much. Its a bit pricey to be messing around with that!
The part # for the JBL tweeter is JBL TR 225.
Apparently the tweeters on the JBLs have crossovers built in.
| quote: | | thats probably whats happening here too as his levels are on 1/10, resulting the djs to push the mixer at max to get any level at all. so the output on the mixer distorts, the input in the amp distorts, resulting a clipped signal being amplified sending DC current to the speakers burning the coil. |
I have a friend of the "crusading" friend who is going with him to visit the tech and take a look at the busted parts. I asked him to let me know if he sees anything that is melted, burned, or otherwise shows signs of extreme heat. The friend mentioned that the tweeter runs really hot (he did the wedding gig.) What is a normal operating temperature for a loudspeaker?
I will let the guys know that we are doing it wrong with the amp volume. So we really should have the amp at somewhere between 5 and 7 (out of 10) and turn the mixer way down? It would make sense that things blew because I usually see the volume turned up the other way, turned up on the mixer first and then on the amp.
Thanks again guys. I hope to get to the bottom of this, for my friend and MY sake. |
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