Electro
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- Mar 30, 2011
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It does not matter whether the amp is underpowered ,overpowered or indeed just the perfect power for the speakers if you push the amplifier into clipping then the end result will be the same in all cases , the only difference is how long it takes to damage the driver . 
Another way to fry you speakers is to use the speakers and the amp to their capable limit even without clipping for a long period of time and then turn the system straight off , the voice coils can heat up and melt even after the system has been turned off because suddenly there is no cooling from the movement of the cone .
The latent heat causes the drive units to get hotter after the amp is switched off and this is when the failure occurs :O
The best thing to do after a party or a long loud listening session is the play the system at a low level for 10 minutes before swithing off to allow the drive units to cool .
I have heard of many people complain that their speakers where all right when they switched off but the next day when they tried to use their system the drive units were blown
Another way to fry you speakers is to use the speakers and the amp to their capable limit even without clipping for a long period of time and then turn the system straight off , the voice coils can heat up and melt even after the system has been turned off because suddenly there is no cooling from the movement of the cone .
The latent heat causes the drive units to get hotter after the amp is switched off and this is when the failure occurs :O
The best thing to do after a party or a long loud listening session is the play the system at a low level for 10 minutes before swithing off to allow the drive units to cool .
I have heard of many people complain that their speakers where all right when they switched off but the next day when they tried to use their system the drive units were blown
Vladimir said:Dude, you didn't read the Ken Kantor links.
I did and I have. He argues well but he is one voice among many, and the many, equally well qualified think differently.
Furthermore it does not reflect the reality of the way speakers are blown in real life. The vast majority of cases that dealers see involve low powered amplifiers driven into distress and destroying speakers with higher power ratings. As I said earlier, I pretty much guarantee you that somewhere in the country hi-fi shops are dealing with such issues right now. It is a monday, when most blown up kit is returned.
And by the way, the JBL paper that he believes to have been written by the marketing guys was actually produced by JBL's Professional Products division headed up, at that time by John Curl. I know this because I was there, being trained by John, among others for the post of Professional Applications Engineer for the UK.
More by the way, someone mentioned guitar amps as an example of distortion not destroying speakers, the person clearly has no experience of the industry at pro level where guitar and other musical instrument amplification blow speakers all the time. This is despite the fact that the drive units used are designed for ruggedness and reliability and usually way overspecced to deal with the amplifier output. For example, the legendary Fender Twin guitar combo, a 60 watt valve amplifier, used 2 x JBL D120F speakers each with a nominal 75watt rating and the ability to handle over 100watts if the distortion content was allowed to rise to 10%.
Vladimir said:
It is, but as always in hi-fi and audio, nothing is ever quite clear cut.
Given my engineering background I find having at least some degree of understanding helps when trying to work out why certain hi-fi components and systems behave the way that they do. My expertese, such as it is, is mostly practical rather than theoretical, I have for example wound voice coils and used them to build speakers which were then tested to distruction in the labs at Northridge. Lessons like that tend to stay with you.
At that time the focus of JBL Professional was on studios, JBL were developing their new 4 way studio systems and I was being trained, in part, to liase with EMI in England who were likely to be one of their biggest customers. EMI's technical people, then in Hayes, close to the record pressing plant, had pre-production models for test and provided JBL with very useful feedback.
Our work was successful and EMI bought the 4343 system, at the end of the contract I think they bought 84 pieces ( my memory says 84prs, but that is too many I think). I helped install the first pairs in Abbey Rd, some in Paris and some as far afield as Lagos. EMI were truly a world wide company in those days.
Apologies for another DDC anecdote......
The JBL 4343 story isn't finished yet. The famous Kenrick Sound in Japan produces the KRS 4343 based on the JBL 4343 today.
I quite enjoyed this video. https://www.youtube.com/watch?v=qArzARmoRG0
I quite enjoyed this video. https://www.youtube.com/watch?v=qArzARmoRG0
Vladimir said:
That is a hoot....... :clap:
The 4343 was the best JBL speaker in that series but was massively overshadowed by the 'Texas Bookshelf' itself, the mighty 4350.
When I moved on (in the wake of the Harmon takeover) I had a pair of 4333, the classic 3 way system. One of my last jobs was overseeing a new pair of 4350s being installed in a west end studio. I had the option to aquire their old 4350s for a song, they needed a complete refurb which I could have done myself at modest cost but I had absolutely nowhere to put them.......
If that happened to me, I would nibble my arm off during a nightmare.
Closest I've gottent to similar situation was an offer to buy these JBL 4756A for 1000 euros with one broken compression driver. LOL close but not quite a 4350!
Closest I've gottent to similar situation was an offer to buy these JBL 4756A for 1000 euros with one broken compression driver. LOL close but not quite a 4350!
Vladimir said:If that happened to me, I would nibble my arm off during a nightmare.
Closest I've gottent to similar situation was an offer to buy these JBL 4756A for 1000 euros with one broken compression driver. LOL close but not quite a 4350!
That is a 'second generation' blue baffle but still has the early 2230 bass drivers if I remember correctly. Several of the bass drivers were blown so I could have easily rebuilt them all as 2231s and I think one of the 2440s was a bit crackly. Again a full degauss (the wonders of alnico magnets) and a good clean followed by a rebuild would probably have sorted that out.
Actually that reminds me, another west London studio was having trouble with their '50s, a sharp cracking sound in the mid range at anything resembling normal (studio) levels. It was quite obvious the moment they were played, I checked and it looked like everything was wired correctly, so I put a scope across the input terminals (easy, the amps are outboard) of the mid/highs and was horrified to see the amplifier clipping hard at quite a low output voltage, the Crown D150 that should have been outputing the best part of 100watts was barely outputing 20......!
Anyway it turned out that the D150 was being run from a stepdown transformer as it quite clearly stated 110/120 volts on the rear (its an American amp) however a quick call to the distributer confirmed that all amps supplied to the UK market were converted internally to 240 volt. In this case the lable giving the correct voltage had simply fallen off.....!
Remove the transformer, plug the amp in normally and problem resolved. Of course by my own theory the clipping amp should have distroyed the drive units, but in this case the ruggedness of the pro-level drive units and the fact that the problem was discovered the moment the system was installed (not by me in this case) saved the day.
WTH are you doing here commenting cheap amps and speakers on WHF Dave. Move to Japan, you will be considered royalty there.
Vladimir said:
The JBL thing was interesting, they took the time and effort to put me through a fairly serious training program to fulfill a role in the UK and Europe but when the Harman take over took place in '76 they, Harman, had their own people who had come up through the Tannoy organisation, then also part of Harman International.
I found myself surplus to requirements, so moved into live sound production at the beginning of the punk era. In the spirit of the age I learned FOH and stage monitor engineering on the job and given the exponential rise in live music it took only a couple of years to build my own company with my own sound rigs, lighting and the rest.
Vladimir said:
Naturally, that is my photo in my sig........
Actually it is my cross siamese called Lucy, who, as I type is curled up on the sofa next to me. She is Andalucian, but speakes fluent siamese, a lot.
She is a cutie. Lucy from Andalucia.
I have a male cat that came in my living room through the window one day, starved, skinny and lost. He just flopped on the sofa and asked whats for lunch and here we go 3 years later, still unemployed eating my food, hasn't paid a single bill. :doh:
I have a male cat that came in my living room through the window one day, starved, skinny and lost. He just flopped on the sofa and asked whats for lunch and here we go 3 years later, still unemployed eating my food, hasn't paid a single bill. :doh:
plastic penguin
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davedotco said:Vladimir said:
Naturally, that is my photo in my sig........
Actually it is my cross siamese called Lucy, who, as I type is curled up on the sofa next to me. She is Andalucian, but speakes fluent siamese, a lot.
The crucial question: Does the cat prefer active or passives? :twisted:
plastic penguin said:davedotco said:Vladimir said:
Naturally, that is my photo in my sig........
Actually it is my cross siamese called Lucy, who, as I type is curled up on the sofa next to me. She is Andalucian, but speakes fluent siamese, a lot.
The crucial question: Does the cat prefer active or passives? :twisted:
Much as it pains me to say it, she is a very laid back individual, definitely in the passive, 'pipe and slippers' camp.
The only time I recall her taking an interest was back in Spain when she seemed a little disturbed by something coming from my ribbon (hybrid) speakers. Certainly nothing that I could hear though, made me worry a bit about superfluous hi frequency energy or maybe RF.
The reaction was noticeable but entirely random, which made me think about RF........... :?
Vladimir said:
Sorry Vladimir, but Bull!!!.
Example: Said speaker has a thermal rating of 50 watts at 8 ohms. V2/R says that 50 x 8 =400. Square root of 400 is 20 so said loudspeaker can take 20 volts AC continuously without overload as long as it is a sine wave.
30 watt amplifier into 8 ohms using the above equation gives a voltage of 15.5 volts sine wave. Now allow for transients that relate to about 2.5 times the rated power of the amp and it's gonna generate a square wave or, to put it another way, clip. Loudspeakers don't like square waves or any DC at all and that's what welds the voice coil to the pole piece.
Amplifier of 150 watts into 8 ohms produces 34.6 volts AC but, because it's over on power, you won't turn it up like the 30 watter so you won't clip it. Loudspeakers carry on singing happily. Basic maths, nothing more.
Vladimir said:First Dave, now Richard. Ummm...
There's no "Ummm" about it Vlad. C'mon. You know as well as I do that if you stretch the amp past its comfort zone it's gonna play up and the poor old loudspeaker's on the sharp end of it all.
I haven't seen Daves post so I can't comment on that but surely even you can see what I'm on about.
ray:PS: Why you hiding under a chair??? :rofl:
I wasn't expecting a rock quarry avalanche of authority pile on me! I was more hoping me and Kev discuss "electronics", me a graphic designer and he probably a lawyer. Now I have to rethink the amp clipping stuff again, I was set on it.
This hobby is masochism.
This hobby is masochism.
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