30 watts!?

Discussion in 'Beginners, General Questions' started by jeff_c, Jan 29, 2006.

  1. jeff_c

    jeff_c Auditioning

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    I have been looking into some in ceiling speakers and some say they are 30watts rms. Is this good or crappy? I've been in car audio for years and 500 watts on highs and 1500 on subs is common place. How can 30 even be heard. Some car speakers don't recommend going below 45 watts. But I'm sure home audio is very different. Can someone pls explain.
     
  2. Wayne A. Pflughaupt

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    Ever heard the background music in a restaurant or doctor’s waiting room? You were listening to probably 5 watts or less.

    There are all kinds of speakers for all kinds of applications. The speakers you're looking at obviously are not intended to be the main speakers in a high performance home theater system. They're most likely for background music in a second zone, especially with a rating like that. For that application, 30w is more than enough.

    Regards,
    Wayne A. Pflughaupt
     
  3. JeremyErwin

    JeremyErwin Producer

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    post a link, mention the model name.

    Speakers aren't normally rated in terms of watts, but in terms of sensitivity, A 88db/W/m would produce, in an anechoic chamber, a SPL of 88 db at a distance of 1 meter. Most of us place the speakers farther away then one meter, and usually, the sound is reinforced by reflections off walls. Add 3 db if it's near a wall, 6 db if it's in a corner. Subtract 3db for every additional meter.

    consult this spl caculator for more details

    Your average, every day, run of the mill 8 ohm speaker has a sensitivity of 88-90 db/W/m. 32 W per channel. fed into two speakers, 9 ft away, will produce 100 decibels at the listening position.

    As for enormous power demands, I can only conclude that a car is a terrible place for audio-- no wall or corner reinforcement is really possible. And you don't get the benefit of a large, well designed cabinet.

    I have a 100 Watt subwoofer in my living room. It's essentially a rectangular box, 12--16 inches on side, and it contains a 10 inch driver. It weighs about 40 lbs. Your really can't build this kind of enclosure for car audio purposes, so the alternative is to use a high powered amplifier, figuring that most of the sound will be absorbed, or directed out of the car.
     
  4. Cees Alons

    Cees Alons Moderator
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    Jeff,

    Welcome to the forum.

    A piano, playing at full strength produces about 1W of sound energy. Granted, speakers are very inefficient, but a real and constant 500 Watts in a car is simply impossible. Probably those numbers are gross exaggeration anyway, or else they denote a maximum that's hardly ever (if ever) reached in practice. Your ears would be gone.

    And 500 Watts / 14 Volts would mean 35.7 Ampères. Constantly? Ever?

    That all said: 30W per channel is indeed just enough for not too big a room. For high-quality audio a bit more would be recommended, especially to have some headroom for the very loudest peaks.


    Cees
     
  5. Jack Briggs

    Jack Briggs Executive Producer

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    Please remember that one of the all-time great audiophile speaker systems is the venerated and still-made Klipschorn, a horn-loaded corner speaker of enormous size. It is also one of the most efficient speaker systems ever made. All one would need to drive it is about 20 watts per channel for very loud sonics.

    A speaker system's efficiency (or lack of) is not the overriding determnination of its sound quality. And those numbers you cite for car audio are badly inflated.
     
  6. JeremyErwin

    JeremyErwin Producer

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    Does Klipsch make it in an in-ceiing, or in-wall model?
     
  7. PaulT

    PaulT Supporting Actor

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  8. Cees Alons

    Cees Alons Moderator
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    The horn-loaded driver is indeed considered to be the most efficient speaker housing design. By far.


    Cees
     
  9. JeremyErwin

    JeremyErwin Producer

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  10. ChrisWiggles

    ChrisWiggles Producer

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    Remember not confuse efficiency with sensitivity! Usually you're concerned about sensitivity when it comes to speakers, efficiency doesn't really matter so much except in dealing with heat when designing the drivers and things like that.
     
  11. Ralphie_B

    Ralphie_B Stunt Coordinator

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    As for enormous power demands, I can only conclude that a car is a terrible place for audio-- no wall or corner reinforcement is really possible. And you don't get the benefit of a large, well designed cabinet.

    I think what you're saying is correct. I will note, though, that in my commuter car (a Toyota subcompact), I'm running Infinity Reference 2-way speakers (4" front, 6x9" rear) driven by a cheap Panasonic head unit (45Wx4 peak, 21Wx4 RMS). Even at those low power levels, the volume inside the car gets too loud before the head unit starts clipping. I get surprisingly good bass response too -- perhaps this is because the 6x9" speakers in the back are using the entire volume of the trunk as an enclosure...?
     

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