very strange

[hammy]

Ok, I set my rig up last night and all switched on the sound check went well an sounded good.

20 mins later when the disco was due to start I switched on again and my jbl`s sounded like pooh, The only way I can describe it is really really dull sounding, After 10 - 15 mins of changing cables and power leads it still sounded pooh, I switched on my mic turned up the volume a bit too much which caused a bit of feedback, As soon as the feedback came on the jbl`s sounded crisp and perfect again apart from one side which seemed to catch up after an hour.

Is this something thats wearing out ??

jbl eon 315`s

[Excalibur]

It's sounding like a loss of the HF units, but why they went off in the first place,and why they came back after you got the microphone feedback is the big question? :confused: :confused:

You haven't got an active crossover in the chain have you? Or subs with a built in crossover? Somewhere in there would be my bet.

[hammy]

Easy answer to that is no, They are coming straight from the mixer.

[Excalibur]

Easy answer to that is no, They are coming straight from the mixer.

Guessed as much. :(
Right, now we're into fantasy land. Only thing I can suggest is to see iof you can get to the internal crossover in the cabs easily, and look for any loose connections, or poor looking solder joints. Modern solder is notoriously unreliable, since they modified the stuff on Elf and Safety grounds!

I believe the JBL's are quite "pronounced" in the top end, so losing that would indeed make them sound muddy and woolly. Best I can do, sorry.

[hammy]

Hey Peter that sounds a perfect explanation "muddy and wooly", The store I bought them from is open today so I might just take them in for them to look at under the warranty

[DiscoPromotions]

As you going direct from the mixer. Did you check the mixer? Food for thought

[hammy]

As you going direct from the mixer. Did you check the mixer? Food for thought

No I didnt

[Excalibur]

As you going direct from the mixer. Did you check the mixer? Food for thought

True, but: There shouldn't be any filters in the mixer to cut the HF.

:lightbulb: Aha!!!!! Possibly well done that man. Tone controls on the mixer. I have a KAM 1500 which has a couple of channels where the tone controls are shot. Just looking at them causes the sound to go from booming bass to screeching tops. Another possible cause.

[hammy]

I should have added I also checked them in different channels ;)

[Booche]

I had a similar situation last night with my Class D's with them sounding a bit crackled then after 10minutes they were fine :eek:

[hammy]

I had a similar situation last night with my Class D's with them sounding a bit crackled then after 10minutes they were fine :eek:

Hi Dave, Its not a crackling sound its as Peter says "muddy, Woolly, Muffledy, Dull", Its sort of like they are holding back on their true sound

[Booche]

Hi Dave, Its not a crackling sound its as Peter says "muddy, Woolly, Muffledy, Dull", Its sort of like they are holding back on their true sound

Yeah sounded similar and the tops sounded abit crackly but like i say 10mins of "Background" music and all seemed well :confused:

Anyway wont hi-jack your thread mate :D hope you manage to sort the issue.

[Daryll]

Certainly sounds like a dry joint somewhere in the HF path , hope you get it sorted mate.

Daryll

[hammy]

just had a peek inside and its the top bit thats not working, I have swapped it over with the other unit to check its not any wires and it worked perfect, dont know what you call the top one but its the top endv, The small speaker bit ;) would this be covered under warranty????

Figuring it ou its the neodymium high frequency compression driver

[Booche]

Tweeter :sofa:

[Excalibur]

just had a peek inside and its the top bit thats not working, I have swapped it over with the other unit to check its not any wires and it worked perfect, dont know what you call the top one but its the top endv, The small speaker bit ;) would this be covered under warranty????Figuring it ou its the neodymium high frequency compression driver

Good question, I don't know. Obviously, it should be, but the word "Thrashed" may be brought into play, in an attempt to avoid paying for the repair.

Under the circumstances, I'd be looking for having new crossovers fitted, and new HF units. Why did one or both fail? If you don't replace the x-overs, will a new unit fail also? How old are they?

[hammy]

Yep its the driver http://www.jacksmusicfactory.com/default.asp?productid=91475_JBL_2414H-1_Driver they are only 4 months old so they will repair or replace, what causes a driver to fail though?? I never thrash them and treat them with kid gloves

[Excalibur]

Yep its the driver http://www.jacksmusicfactory.com/default.asp?productid=91475_JBL_2414H-1_Driver they are only 4 months old so they will repair or replace, what causes a driver to fail though?? I never thrash them and treat them with kid gloves

Faulty crossover is a possibility. Thrashing is a definite possibility. ( For some folk)

[hammy]

Well the thrashing bit is out then as I have never even seen the clip light come on, Only the green signal light, The shop tech is going to ring me tuesday when he is back so we will see what happens

[Excalibur]

Well the thrashing bit is out then as I have never even seen the clip light come on, Only the green signal light, The shop tech is going to ring me tuesday when he is back so we will see what happens

Aha again. :lightbulb: They're active, aren't they? More possibilities appear.

Let us know how you get on.

[hammy]

Yes peter they are active, What are the other possibilities???

[Excalibur]

Yes peter they are active, What are the other possibilities???

Well to put it simply, if they were passive, there is a filter inside the cab. This splits the frequencies into hi and low after the amp. Thus why I wanted the filters checking.

In an active cab, it's the other way round. The signal goes into the filter, and is split hi and low, and then fed to two separate amps. Thus you could possibly have a fault in the amp driving the tweeter as well.

Fault could be in crossover, tweeter, or hi amp therefore.

[mattydinx]

As you going direct from the mixer. Did you check the mixer? Food for thought

+1 - I've got a tempremental right channel out of my mixer when using the balanced outputs, I'll sometimes lose all bass completely before it springs back into life.

I've had to settle on the Phono out's until I can get it repaired/replaced

[hammy]

just had a peek inside and its the top bit thats not working, I have swapped it over with the other unit to check its not any wires and it worked perfect, dont know what you call the top one but its the top endv, The small speaker bit ;) would this be covered under warranty????

Figuring it ou its the neodymium high frequency compression driver

time for a re-read matty

[spin mobile disco]

Ahh may be able to help on this one. Did the venue or storage of speakers etc come in to touch with a high humidity?
I had the same problem several times with a particular venue a childrens indoor play park. Because of the high humidity the speakers internal protection came on and shut the high frequency drivers down.
After half an hour of panicky trial and error one of the speakers came back on. So i switched to a mono signal to continue the evening. Then hald an hour later again other speaker did the same. The speakers were brand new and the bags ordered had not arrived yet so I suspect that due to lack of protective covering they got a bit colder than usual in transit so when i entered the high humidity they condensed the moisture in the speaker. I dont know why the hf unit seem to be affected first but may shed light on it.

[hammy]

Should have ended this by saying "the hf driver was shot" so i bought a new one

[DAVESOUNDS SERVICES]

May i please ask?
was the compression driver expensive for the JBLs?
or did you simply fit a new diaphragm?
Cheers
Dave

[hammy]

May i please ask?
was the compression driver expensive for the JBLs?
or did you simply fit a new diaphragm?
Cheers
Dave

The diaphragm in the 315`s hf driver cant be repaired for some strange reason, all in all vat, postage etc cost me £87

[hammy]

Oh well its time to re-open an old thread of mine.

Since this thread ended the HF driver has blown twice on me and last night it has gone again. A new driver seems to last about 6-7 gigs and then gives up the ghost.

Its not the mixer as I now use an MC 6000

Volume on the speakers is at 10 oclock.
Gain on the mixer is at 9 oclock (MC 6000)
master on the mixer is at 2 oclock
Gain on VDJ is 12 oclock.

I have looked inside and there are no loose wires, I do not thrash them at all.
I am totally stumped on this now.

[Excalibur]

Oh well its time to re-open an old thread of mine.

Since this thread ended the HF driver has blown twice on me and last night it has gone again. A new driver seems to last about 6-7 gigs and then gives up the ghost.
.

Hmmmm. Sort of gives the lie to "With active speakers you won't blow drivers, cos they're perfectly matched to the amp".

Hammy, there's got to be a fault somewhere. Perhaps one of the soldering iron men will cast light on it, but I'd be inclined to suspect either the HF amp inside the cab, or the crossover unit, in case it's feeding LF to the tweeter. They don't like that at all. Is it always the same cab? If so, I'd definitely say I'm on the right lines.

[hammy]

Hmmmm. Sort of gives the lie to "With active speakers you won't blow drivers, cos they're perfectly matched to the amp".

Hammy, there's got to be a fault somewhere. Perhaps one of the soldering iron men will cast light on it, but I'd be inclined to suspect either the HF amp inside the cab, or the crossover unit, in case it's feeding LF to the tweeter. They don't like that at all. Is it always the same cab? If so, I'd definitely say I'm on the right lines.

Im not sure if its the same one yet Peter, I will be examining it today after my boys footie match.

I will add that before they are switched on and off the volume is fully off and they are the last things to be turned on and the first things to be turned off (as per manual).

[Alchemy]

Hi Hammy,

I found an interesting youtube video by an American JBL service dealer. They were replacing a diaphragm on a JBL HF driver and the guy says that the driver is dead but there is no evidence of over powering, he goes on to say that in cases like this it's normally caused by corrosion on the flex lead connections of the diaphragm. If you have an ohm meter just test across the terminals of the disconnected driver, if you get a reading its probably not corrosion. Have you taken one of the blown drivers apart? It would be interesting to see if they are damaged or if they are simply open circuit. Are you storing your speakers in a garage or somewhere that could allow corrosion to take place? Just a thought.

Here's the video in case it helps

JBL Speaker Repair Replacement Diaphragm JBL 2418H Installation by Simply Speakers - YouTube

[hammy]

I took one apart Steve and the metal coil thing that connects each side to the driver was broken. Pa is stored in my house.

On watching the video, If you go to 2:25 on top of the driver you can see a copper wire each side of the driver, Its one of them that keep breaking, It is a different driver but principle is the same.

[Excalibur]

If you go to 2:25 on top of the driver you can see a copper wire each side of the driver, Its one of them that keep breaking, .

Well unless there's an awfully bad batch of tweeters floating about, I'd back a fault elsewhere. ( Unless of course it actually is a design fault in the units )

Keep us posted.

[Alchemy]

I'm sort of with Pete on this, you need to work out if it's the same speaker each time to start with. If it is (and you haven't been a victim of a bad driver batch) then it must be further up the signal chain. If, as Pete mentioned the crossover or the HF amp is sending a distorted signal to the HF driver you could change it as many times as you like and it would still happen. Maybe you should get it checked over by someone with an oscilloscope to rule this out.

[hammy]

Bit of an update, Its not the same speaker that keeps blowing, I know this as the last HF driver I put in had no markings and this one has all the stickers on it, So now I`m lost.

[Excalibur]

So now I'm lost.

I had a different phrase in mind. ;) That might lean towards a bad batch of tweeters, but even so, the failure rate is so high that I'm inclined to think there's another factor involved.

I'm sorry mate, but I have no useful suggestions for you. In the old days, with cheap passive cabs, wiring in a resistor, or adding a couple more piezos in series could offer protection to the tweeters. I have no idea whether it's possible to add such safeguards to actives with compression drivers. :confused:

[Alchemy]

Bit of an update, Its not the same speaker that keeps blowing, I know this as the last HF driver I put in had no markings and this one has all the stickers on it, So now I`m lost.

?????? OK, well that means that it's either a bad batch of drivers (where are you getting them, are they JBL?) or somehow a square wave is being produced by your playout, are you sure there is no clipping occuring?

[Excalibur]

?????? OK, well that means that it's either a bad batch of drivers (where are you getting them, are they JBL?) or somehow a square wave is being produced by your playout, are you sure there is no clipping occuring?

Oh don't ask him that, I nearly had to scrape him off the ceiling when I suggested he'd thrashed them. ;)

There is a faint possibility that it's a crossover problem, cos it's a curious arrangement in there. They apparently use one amp with two channels to drive the thing. I'm still wondering if it's getting some low frequency into the tweeter.

I've not got any useful suggestions left though.

[hammy]

?????? OK, well that means that it's either a bad batch of drivers (where are you getting them, are they JBL?) or somehow a square wave is being produced by your playout, are you sure there is no clipping occuring?

100% sure im not overdriving them, They are genuine parts and have bought from all over the world never the same shop.

[katman]

Having just spoken to Hammy on the phone I suspect that there may be some frequencies above the range of human hearing being fed to them long term which is gradually cooking them.

As its the other cabinet that has now failed that would preclude any fault with the crossover or amps in the cabinet itself so points to an external factor.

Thinking about the best way to test for this with no specialised equipment I came up with the following idea.

1. Set everything up in a typical setup but with faders in the positions they would be during normal playout but with nothing actually playing.
2. connect a multimeter to the horn and measure the voltage on the terminals.

There will almost certainly be a slight DC offset but this should be well below 200mV, probably less than 10mV

Then measure on AC. There should be no discernable voltage present. if there is then something is driving the horn and if you cant hear it, it will be above the range of human hearing.

Should you see that then you need to find the source. Start closest to the speaker cabinet and work backwards along the audio chain.

Disconnect the input - it should disappear - if not, it is coming from within the cabinet. - Reconnect if OK

Next turn the master output to zero on the mixer - it should disappear - if not something in the mixer is generating noise after the master fader.

Also try powering off various pieces of kit. Almost everything these days has switch mode power supplies operating above the audio range and if one of those was generating noise it would cause problems.

Its a difficult one to track down without being able to get at the problem "hands on" :(

[Excalibur]

Having just spoken to Hammy on the phone

Since I didn't understand anything after that, I'll bow out now the cavalry have arrived.

There may be advantages to actives, but I'm happy being able to substitute components more easily for fault finding. :D

Aha! Cracked it. Hammy, leave the Sonic Screwdriver at home. ;)

[Alchemy]

I have been doing a bit of lateral thinking and I've come up with a possible scenario. What if you have in your music collection a number of very heavily compressed tracks that have been ripped from CD's or downloaded. If you have been playing these tracks on a regular basis it's possible that heavy over compression will produce a square wave that will fry your HF driver without any obvious clipping. Do you have any audio software such as Adobe Audition or Soundforge Audacity that you could check the waveforms of some of your regular tracks on?

[hammy]

I will try Steves idea first as it seems as easy as just clicking a button. Ok Steve how the hell do I use adobe audition to check the waveforms and what am I looking for?

[Alchemy]

I will try Steves idea first as it seems as easy as just clicking a button. Ok Steve how the hell do I use adobe audition to check the waveforms and what am I looking for?

Hi Hammy,

If you load a track into Audition and go to the edit screen you will see a white line at -1dB if the track has been heavily over-compressed and is clipping you will see the wave form exceeding this line. You can zoom in to make things easier to see as a track like this would probably appear as a solid block of green at normal viewing size.

[hammy]

Hi Hammy,

If you load a track into Audition and go to the edit screen you will see a white line at -1dB if the track has been heavily over-compressed and is clipping you will see the wave form exceeding this line. You can zoom in to make things easier to see as a track like this would probably appear as a solid block of green at normal viewing size.

:whoosh:

[Alchemy]

:whoosh:

:Laugh: :Laugh: :Laugh: :Laugh:

Believe me, it's not as complicated as it sounds :)

[Alchemy]

I found this example of the change in compression and hard limiting over recent years in order to increase the volume of music on CD's, this is what you are looking for. You'll notice the 2000 waveform is heavily clipped in places.

Hope this helps :)

[hammy]

I found this example of the change in compression and hard limiting over recent years in order to increase the volume of music on CD's, this is what you are looking for. You'll notice the 2000 waveform is heavily clipped in places.

Hope this helps :)

But when I zoom in it just goes to a solid line, If I zoom out it goes green as in the above clip, I still dont know what im looking for. :daft:

[Alchemy]

If you zoom in does the solid line (waveform) consistently break the -1dB line at it's peak?

[Alchemy]

Any news Hammy?

[hammy]

Any news Hammy?

I really dont understand the waveform thing at all Steve so im going with Katmans advice first :D.

I spoke with Paul at audioloudspeakers, And he thinks I am overdriving them, How i dont know as my top (treble) never goes past 12 oclock my gain on MC 6000 is at 3 oclock, my settings (top, Mid and bottom) on VDJ are at 12 oclock as is the gain on VDJ, The channel gain on MC 6000 is at about 9-10 oclock, The only thing that is full is the 2 volume sliders on VDJ, The speakers are 10 - 12 oclock on flat, So if thats overdriving them then I need to start doing silent disco`s.

[Excalibur]

I really dont understand the waveform thing at all Steve so im going with Katmans advice first :D.

I spoke with Paul at audioloudspeakers, And he thinks I am overdriving them, How i dont know as my top (treble) never goes past 12 oclock my gain on MC 6000 is at 3 oclock, my settings (top, Mid and bottom) on VDJ are at 12 oclock as is the gain on VDJ, The channel gain on MC 6000 is at about 9-10 oclock, The only thing that is full is the 2 volume sliders on VDJ, The speakers are 10 - 12 oclock on flat, So if thats overdriving them then I need to start doing silent disco`s.

Never mind where the knobs and buttons are, do you get any red lights? Anywhere in the signal chain? That 6000 is quite a high output, and I got a significant improvement in John's by turning the master volume down.

If I read the JBL manual correctly, try setting the tone control on the cabs to "Boost" or whatever it is. This apparently boosts the low end a bit, and you may find you can thus back off the master a bit more, and lower the signal to the HF units.

PS. Which Old Git told you from the outset that you'd be accused of thrashing them? :whistle: :D :D :D

[hammy]

Never mind where the knobs and buttons are, do you get any red lights? Anywhere in the signal chain?

PS. Which Old Git told you from the outset that you'd be accused of thrashing them? :whistle: :D :D :D

They do not clip at all, Trust me I keep my eye on them after the first time the hf driver went.

I dont thrash them :Censored: :Censored: :Censored: :Censored: :p :p

And the lights on the volume control on Mc 6000 never go past 0Db

[katman]

If I read the JBL manual correctly, try setting the tone control on the cabs to "Boost" or whatever it is. This apparently boosts the low end a bit, and you may find you can thus back off the master a bit more, and lower the signal to the HF units.

I just looked at the manual and it says....

EQ -Boost

when the control is switched to the Boost setting low frequency and high frequency equalization is applied; +3dB @ 150Hz and +2.5dB @ 4kHz. With the Boost applied low level music playback will sound much fuller with increased high frequency clarity

... so it will drive the horns harder and as 3dB represents a doubling of power the 2.5dB boost to the treble will drive the horns almost twice as hard.

I also note from the block schematic that the limiter is BEFORE the EQ section so you could be just before limiting level and then add another 2.5dB of gain with the EQ.


I really dont understand the waveform thing at all Steve so im going with Katmans advice first :D.

I spoke with Paul at audioloudspeakers, And he thinks I am overdriving them, How i dont know as my top (treble) never goes past 12 oclock my gain on MC 6000 is at 3 oclock, my settings (top, Mid and bottom) on VDJ are at 12 oclock as is the gain on VDJ, The channel gain on MC 6000 is at about 9-10 oclock, The only thing that is full is the 2 volume sliders on VDJ, The speakers are 10 - 12 oclock on flat, So if thats overdriving them then I need to start doing silent disco`s.


Never mind where the knobs and buttons are, do you get any red lights? Anywhere in the signal chain? That 6000 is quite a high output, and I got a significant improvement in John's by turning the master volume down.

It also mentions that it features a "dynamic limiter". To me this suggests that it isnt just a simple limiter but more of a compressor/limiter introducing some soft compression to reduce the dynamic range before the onset of hard limiting to protect the amps from clipping.

If that is the case and it is compressing then the net effect of that is that due to the reduced dynamic range of the signal, the average level being fed to the speakers will be higher resulting in the temperature of the voice coils being higher.

As you are suffering the failures after several gigs that would seem to fit the pattern that you are seeing.

What type of music do you mostly play ?

I have noticed with a lot of the modern stuff that there seems to be "too much going on" a lot of the time and the levels never really drop like they used to with 70's and 80's music. That doesnt give the amps or speakers any resting time and the average power levels are a lot higher and probably accounts to some extent why we need a lot more power than we used to.

[hammy]

I dont boost it, I have it on flat, which is the setting the manual says for normal use.

[Excalibur]

I just looked at the manual and it says....

EQ -Boost

when the control is switched to the Boost setting low frequency and high frequency equalization is applied; +3dB @ 150Hz and +2.5dB @ 4kHz. With the Boost applied low level music playback will sound much fuller with increased high frequency clarity

... so it will drive the horns harder and as 3dB represents a doubling of power the 2.5dB boost to the treble will drive the horns almost twice as hard.
.

My mistake there Sir, I read that passage more than once, and still didn't spot that it boosted the top as well. :o :o :o :o :o :o :o :o :o :o :o :o :o :o Well spotted that man, thanks for that.


All the time, I was thinking "that doesn't seem right". I missed the bit about boosting the high frequencies as well.
Right, well if boost doesn't work, then conversely "Cut" might offer some help perhaps?

Let's throw these two bits into the mix then, first what about changing the units for some lower cost, repairable ones of a similar rating. I have no idea if it would alter the sound too much, but I'd have been heading down that road when the second unit blew.
Second, is there any form of protection that could be added, to prolong the life of the correct units?


Hammy, a thought suddenly occurs, you haven't been thrashing them, have you? :sofa:

[Alchemy]

Hammy, a thought suddenly occurs, you haven't been thrashing them, have you? :sofa:

:eek: :eek: :eek: :Laugh: :Laugh: :Laugh:




I have noticed with a lot of the modern stuff that there seems to be "too much going on" a lot of the time and the levels never really drop like they used to with 70's and 80's music. That doesnt give the amps or speakers any resting time and the average power levels are a lot higher and probably accounts to some extent why we need a lot more power than we used to.

This is what I have been trying, (unsuccessfully) to explain when I was getting Hammy to look at the waveforms. I still think it's a possible contributory factor.

[hammy]

Ok a bit of an update.

I have bought a cheap HF driver http://www.ebay.co.uk/itm/200687316656?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649,
bloomin thing just fit in the casing, Everything is working fine and it is now set up so a 4 year old couldnt even thrash it (just in case I was :Censored: :Censored: ), Lets see how it goes on Saturday.

[Excalibur]

Ok a bit of an update.

I have bought a cheap HF driver http://www.ebay.co.uk/itm/200687316656?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649,
bloomin thing just fit in the casing, Everything is working fine and it is now set up so a 4 year old couldnt even thrash it (just in case I was :Censored: :Censored: ), Lets see how it goes on Saturday.

I bet that one lasts forever mate. ;) If nobody picks up on it, I'll tell you why later. ;) ;)

[katman]

Hope that solves your problems Hammy.

[hammy]

Hope that solves your problems Hammy.

Me too.

[hammy]

Ha, The other one went on and off a few times yesterday (not the cheapo one) so I guess thats gonna go in the next couple of gigs.

[katman]

Get another one order before it goes !!!

I would have changed both anyway becuase there is probably a difference in the sound.

[hammy]

Get another one order before it goes !!!

I would have changed both anyway becuase there is probably a difference in the sound.

Already bought.;)

[hammy]

Ok, We are now back to square one, The new one was going on and off at my last gig. My next step is to put a 10UF 100V capacitor between the live and the driver, Will this be the right capacitor to use?.