Clipping & HK525

Discussion in 'Archived Threads 2001-2004' started by Aaron Lock, Feb 2, 2003.

  1. Aaron Lock

    Aaron Lock Extra

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    I figured I was going to be a little bored this weekend, so I thought, hey, let's test out my HK525 and see where clipping starts. So I borrowed a o-scope from work, and thought how am I gonna do this?

    I figured pumping some sine waves off a CD through the receiver and scoping the output would do the trick. I haven't done it yet, but I just wanted to know if there's a better way?

    Aaron.
     
  2. JohnSer

    JohnSer Stunt Coordinator

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    Don't know the best way, but do know that sine waves will get your amps warmed up in a hurry. I have done it with plate amps and receivers to do driver break-in. Alway had to keep the volume down. Recommend using a high wattage resister load vs your speakers. I'll be interested in your results.

    JohnS
     
  3. Aaron Lock

    Aaron Lock Extra

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    I know it is better to use a high wattage resistor, but I don't have one handy.

    I just played a 1 kHz tone off a CD, turned up the volume until clipping started. About 93% of max volume. Not bad, considering most recievers I've heard of start at around 60%.

    I'm sure that number will vary with frequency, but I just wanted a rough idea.

    Kudos to HK.

    Aaron.
     
  4. JohnSer

    JohnSer Stunt Coordinator

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    Aaron, what impedance are your speakers at 1KHz? At the stated 93% max volume, what was the reading on your display? Did you measure the sine wave p-p out of the CD player? If you are over or under driving it, will make a differance. And one last question, was this two channel driven, or more?


    Sorry, for all the questions.

    JohnS
     
  5. Aaron Lock

    Aaron Lock Extra

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    Not sure about the impedance of the speaker, didn't think to measure it.

    Which display? The receiver said +4 dB.

    I was playing through the DVD player, using the PCM, I'm not sure how to measure that signal.

    It was two channels driven.

    Aaron.
     
  6. AaronBatiuk

    AaronBatiuk Second Unit

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  7. Aaron Lock

    Aaron Lock Extra

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  8. Yogi

    Yogi Screenwriter

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    A few seconds clipped signal is good to fry a speaker. You dont need much.
     
  9. JeremyFr

    JeremyFr Supporting Actor

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    Yeah you never want to run a clipped signal to a speaker because it makes for paused movement which causes the speaker to overheat. Also your receiver stating +4 db means that it is already over the point where theoretically should be clipping that you are overdriving the input stage to the amp by 4db so that means nothing and why companys like Denon & HK do that I have no clue.
     
  10. Guy Usher

    Guy Usher Supporting Actor

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    20 seconds is an eternity, put your finger in a light socket for 20 seconds, it only takes an instant to damage your speakers.
    I guess I just dont understand. . .
    Remind me not to buy any used equipment from you. . .
     
  11. JohnSer

    JohnSer Stunt Coordinator

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    Assuming a standard 2-way speaker, most of the energy was to the woofer. Its not something I would do, but doubt that he hurt his speakers. If a frequency was picked that went to the tweeters, probably would have a couple of open voice coils right now. Might not even have to clip, just focusing full output to a high frequency band, that never happens in music, could kill the tweeters.

    JohnS
     
  12. Michael R Price

    Michael R Price Screenwriter

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    Aaron,

    Aaron has it right here. What you need is a load resistor that approximates the impedance of your speaker (4 or 8 ohms usually) and can handle maybe 50-200 watts. You can get those for something like $10 at Parts Express, or maybe the place you work has them if they had an oscilloscope. That way you can run the tones into the load resistors and measure the output voltage. It is quite unsafe to run continuous tones through speakers at high levels. Also, what voltage did the oscilloscope show when clipping started? That is much more important than where on the volume control you were. From there we can calculate the wattage.
     

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