electronic crossover network

Discussion in 'The Projects Forum' started by hindiikawayos, Jun 8, 2011.

  1. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    what current rating is required for electronic crossover network?
     
  2. Audioguru

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    Dec 20, 2007
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    A crossover network for a speaker system divides frequencies to a woofer, midrange speaker and a tweeter. It uses coils and capacitors (and maybe some resistors) and is not powered so it uses no power supply current.

    An active crossover network uses transistors or opamps and uses a very small amount of power supply current because it drives the high input resistance of the power amplifiers.

    The power amplifiers use fairly high amounts of power supply current. It is easy to calculate when you know the efficiency, load impedance and power output from the power amplifiers.
     
  3. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    thank you audioguru.
    one more, what maximum current rating may i apply for active crossover network? tnx!
     
  4. Audioguru

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    An active crossover network uses low current opamps to make the active filters. It is not a power amplifier that has a maximum current rating.
     
  5. hindiikawayos

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    Jun 8, 2011
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    thank you again audioguru!
    Can I use 1amp? what will be the effect if i use 15Amp? tnx!
     
  6. Audioguru

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    I don't know why you ask about high currents in an active crossover network that uses low current opamps. A TL071 audio opamp uses a power supply current of about 1.4mA (0.0014A).
     
  7. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    I'm only asking because I have already a 12V, 15A power supply and I want to use it in a car audio crossover(DIMPS XM-3A). Thank you for giving the figure. You help me a lot. hopefully you will help others too. Tnx again audioguru! God bless...
     
  8. Audioguru

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    Your 12V 15A power supply will power the active crossover unit and the current used will be less than 20mA (0.02A).
    Your car battery will also power the active crossover unit. Its available current is about 800A but the crossover will still use less than 20mA.
     
  9. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    thank you mr. audioguru. you'r so nice. can i use my available 12V 15A power supply to an active crossover network without damaging the unit? thank you again... more power...
     
  10. Audioguru

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    I don't know if your 12V 15A power supply has too much mains hum to power your active crossover circuit. The circuit uses only as much current that it needs which is less than 20mA.

    If the 12V power supply also powers some power amplifiers then their total output power is about 1.3W per channel into 8 ohm speakers or 2.2W per channel into 4 ohm speakers if the amplifiers are single-ended.
    If the amplifiers are bridged then their output power is about 5W into 8 ohm speakers or 7.7W into 4 ohm speakers.
    Then most of the power from the power supply will not be used because its voltage is too low for much amplifier power.

    The active crossover circuit does not develop power. It simply filters frequencies so that the sub-woofer plays only very low frequencies, the woofer plays only low frequencies and is not damaged by very low frequencies, the mid-range speaker plays only mid-range frequencies and the tweeter plays only high frequencies and is not damaged by low frequencies. A sub-woofer or woofer usually sounds awful when it tries to play high frequencies.
     
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    You cannot use a single ended supply to power an audio crossover buddy.
    It needs a dual rail supply like ±12V or ±15V with ground as the center or level.

    Your 15A supply for a crossover is over kill. Even two 9V batteries can run ur crossover for a day or two continues.

    If you plan to power a power amp too then ur should need ur high amp supply.
    IF you only need to power a cross over, u have to make a DC to DC converter that uses 12V input and outputs ±15V with a virtual ground.

    I believe Bil's blog has a dual supply circuit that you need.
     
  12. Audioguru

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    WRONG!
    of course an opamp circuit can run from a single polarity supply if the opamp input is biased properly at half the supply voltage and input, output and feedback to ground coupling capacitors are used like in my sketch:
     
  13. R!f@@

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    Guru...Try not to confuse the OP.

    I know very well what I have said. No need to show who's is macho...
     
  14. Audioguru

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    What you said is completely wrong.
    I have used a single-polarity supply with audio crossover circuits for about 33 years and they work perfectly.
     
  15. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Darn it guru...I know that and I have too.

    I am trying to help OP make it as simple as possible.

    I dunno what kind of OPAMP OP has and what type of crossover for that matter.
    If he has a ready made one that all he need is the supply or if it is for the car, then he will need a 12V only.
    or if OP had a schema and trying to make one thinking his single ended one will work on his crossover so he can put it in his car but it does not turn out that way....or may be OP does not know that car cross overs have dual supplies inbuilt and all it needs is just 12V to operate.

    The real problem will be pop up noises and ignition noises due to these kinda things
     
    Last edited: Jun 15, 2011
  16. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    The OP had a car model. I've never located the spec sheet on it, but I have seen the pics of it. Internally the device has a DC-to-DC converter from the limited information I've found.
     
  17. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    Thank you very much auodioguru! You help me a lot and I appreciate it much. More power and God bless!
     
  18. hindiikawayos

    Thread Starter Member

    Jun 8, 2011
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    Thank you very much! I've learned a lot from you. more power and God bless...
     
  19. hindiikawayos

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    Jun 8, 2011
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    okay. you mentioned earlier that you can calculate the current needed to supply an amplier if you know already the efficiency, load impedance and the output from the amplier. I would like to ask how to calculate? thank you!
     
  20. Audioguru

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    A class-AB amplifier is about 55% efficient because 45% of the total power creates heat. But a modern class-D amplifier is about 90% efficient.
    Most car speakers are 4 ohms but some are only 2 ohms like in my car.
    Car amplifier power is rated when the alternator is over-charging the battery at 14.4V, not at only 12V.

    Use four TDA7240A bridged amplifier ICs powered from 14.4V and driving 4 ohm speakers. Each amplifier will have a max output of about 30W with lots of clipping distortion or 15W when it is just beginning to distort. Then all four amplifiers have a total output power of 60W plus about 32W of heat so the power supply must produce 92W. The current at 14.4V is 92W/14.4V= 6.4A.
     
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