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Trying to understand wattage

Discussion in 'Beginners, General Questions' started by TomPowerGranger, Aug 25, 2012.

  1. TomPowerGranger

    TomPowerGranger Auditioning

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    Sorry for this pathetic question haha, but I am building a budget home theatre and would love some advice about speakers.
    I've used a Z-5500 for over 7 years now and it's done me fine. I've ran TrueHD etc through analogue from my PC. However I'm thinking of upgrading and want to grasp an understanding of how speakers work.
    So far I know that the amplifier has to have a higher wattage than all of the speakers combined. The amplifier is equivalent to my logitech receiver, but has the flexibility of more inputs (HDMI for example) and I will be able to connect any speakers I want to it. What I don't understand is which speakers to get, which amplifier to get and what difference they make.
    For example, I've seen a Onkyo TX-SR608 on ebay for around £200 which looks like it would fit my basic needs. It says it's a 100watt receiver though - so if the speaker system I want to get it say, 1200watts - will I be able to connect them? Do higher wattage speaker systems make a difference and what difference does the amplifier wattage make?
    My budget is around £350. I've seen this Onyko receiver/amp (are they the same?) on ebay and I've seen low-price 1200watt speaker systems on ebay but before I buy I just want to understand it all better, thanks for reading
     
  2. gene c

    gene c Producer

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    A receiver, or avr (audio-video receiver) has a processing section, an amplifier section and an AM/FM section. It takes in all the audio and video signals, processes them (example: decodes Dolby digital, adds bass/treble adjustments and adjusts speaker volumes), switches the signals to the proper inputs (DVD, SAT, BD, etc) and amplifies them before sending them to the speaker outputs. It also sends the video signal to the display.
    An amplifier only amplifies incoming signals and sends it/them to the speakers. There's also a pre-amp which is pretty much a receiver without the amplifier section. And there's also a an integrated amp which is a stereo receiver without the AM/FM section. If any of this is incorrect I hope someone clarifies.
    Unless you're buying 4 ohm speakers you shouldn't worry too much about a receivers amplifier ratings. Most any receiver will power 8 ohm speakers to ear bleeding levels when setup properly and used with a powered subwoofer. If you're buying 4 ohm speakers then you need to get a receiver that can safely power them or it might go into self-protect mode and shut itself down to prevent damage. Power supplies need a certain amount of resistance to keep from losing control. Think of it like peddeling a bicycle down hill. It's real easy at first, but eventually you start going to fast and your feet can't stay on the peddles any longer (no resistance). Then you crash. Same thing happens to a receiver.
    Speaker wattages are even less important. All a decent speaker (I said decent) needs is good clean power. If you push the amp too hard it will start to distort. It's this distortion, not too much power, that usually damages speakers (tweeters first in most cases). Asking a speaker to produce a frequency lower than it's capable of can also damage it. Using a powered subwoofer and the proper crossover setting in the receivers setup menu will help to prevent this.
    The two most important things to look for when buying speakers and receivers is the ohm ratings and the speaker sensetivity, or SPL (sound pressure level). Make sure the receiver can handle the speakers ohm rating. The higher the SPL the louder the speaker will play. 88-90 db is average, 86 or lower are some-what less efficient and 93 or higher will require much less power to drive them. But don't equate louder with better because it isn't. It's just louder.
    The Onkyo 608 with a decent name brand 8 ohm speaker system (and powered subwoofer) should be very enjoyable.
    And there's no such thing as a decent "low-priced 1200 watt speaker system" on ebay or anywhere else. Most often you really get what you pay for.
     
  3. Mr645

    Mr645 Stunt Coordinator

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    Gene gives you solid advice. When it comes to a receiver and the rated "watts", that comes right below the color of the display in importance. Having information like "110 watts per channel" is like a car saying "top speed of 170" Without more information, you don't know if this is KPH, MPH, FPM etc.
    To know the power output, you need to know watts and voltage. On top of that, the power supply and transformers inside the unit can also limit total power output.
    Stick with any name brand receiver and you will have enough power for just about anything, and if you need more, add an external amplifier. Again, regardless of "ratings" just about any external amp will be more powerful then a receiver.
     

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