True Speaker ratings??

Discussion in 'Speakers' started by Andrew Harvey, Feb 21, 2012.

  1. Andrew Harvey

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    so, i understand the basic tricks given to speaker rating (peak power vs RMS), but recently i have learned a lot about amp scams and dont know what to believe about speakers anymore.. EX: I thought when an amp says 110Watts per Channel it really meant 110WPC... however when i looked at the power consumed it only uses 250Watts, i ran that through the 88% rule, and divided by 7 channels and am only getting 32WPC! That just blows me away that the numbers can be so fudged. So my question is this... I use a pair of Infinity SM 155s which are 'rated' for 300RMS each.. that cant be right.. they make my ears bleed at 110WPC (250W amp using only front 2 channels) and with entire 7.1 surround (32WPC) they still sound KILLER! There's no way they sound that good at only 10% of their power. can anyone explain to me why and how these numbers work?? How much power can they truly handle? is there a good formula/ test i can run?? Thanks in advance guys! Andrew
     
  2. David Willow

    David Willow Babbling Idiot
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    The speaker rating is how much the speaker can handle, not how much it needs. What is the 'sensitivity' of the speakers? That number will give you a better idea how loud you can play them. The higher the number, the easier it is to drive them, the louder they can play. Check out this article from Axiom Audio for good primer on amp and speaker power.
     
  3. John Garcia

    John Garcia Executive Producer

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    Speaker ratings are PEAK, unclipped, before something in the speaker fries. That rating has NOTHING to do with the amount of power required to give you adequate sound levels in your room.
     
  4. Robert_J

    Robert_J Lead Actor

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    And that's not a musical rating. They find RMS with a sine wave. Normally it is at 1,000 hz. If you sent 150w at 10zh into that speaker you would completely destroy the woofers even though they supposedly can handle it. Ignore the speaker and amp power ratings. Get quality speakers and a quality receiver and they will work together.
     
  5. Andrew Harvey

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    Hmm! So why do they give ratings if not to follow them??? plus i cant in all circumstances just buy the best of the best speakers and amps. :P My home theater system is great, but i cant also have a crazy family room system, car system, boat system, etc. lol. If im shopping for a budget system for a boat (i know its different than home audio. but wattage and rms follows the same concept for car 12v systems.) what do i look for in speakers? i feel that i understand amps enough! but as for speakers... im just frustrated that people manipulate the numbers so much!
     
  6. Andrew Harvey

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    david willow: Wow! good article! thanks
     
  7. John Garcia

    John Garcia Executive Producer

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    As David mentioned, sensitivity is one of the main things that you can use to compare one speaker to another. The higher the sensitivity, the easier it will be to drive, more or less. If you look at something like Klipsch, they tend to be high 90s and some even over 100dB sensitive, which means you can get decent volume with less power. Not everyone loves the way they sound though. The REAL thing you need to look for in a speaker though is whether or not you like how they sound, since speakers have the largest impact on what you hear.
     
  8. Andrew Harvey

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    Good tip! Thanks Question: Klipsch have that higher sensitivity rating because they generally use horns, right? Do horns generally have more of a midrange sound to them? Also. whats the i guess you would call 'industry standard' for sensitivity? i mean is 50 really bad? or is 70 the bottomline of a good speaker? True, its mainly about what sounds best to each person, but im looking for a baseline! Thanks
     
  9. Robert_J

    Robert_J Lead Actor

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    They use horns for their mids and highs but their woofers are designed similar to pro audio woofers. Horns have a sound like they were designed to have. You can have a horn loaded sub. There's no standard even for measuring sensitivity. Most of the time you will see 1w / 1m which means 1 watt of power at 1 meter. Or you will see 2.83v / 1 m. Same thing if you are talking about 8 ohm speakers. If it is a 4 ohm speaker measured at 1w, that means 5.66v or twice the voltage. That's not a fair comparison. Basically it's marketing and half truths.
     
  10. Andrew Harvey

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    Is anything straight forward?? lol.
     
  11. John Garcia

    John Garcia Executive Producer

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    The sensitivity range is somewhat shallow. A "typical" speaker would have somewhere in the range of about 90dB sensitivity and 8 Ohms impedance, so something within a few dB of that would be relatively easy to power for most receivers. When you get to lower sensitivity speakers, in the 84-85dB range (see that article from David, -6dB from 90 is a 100% drop in output) would be relatively low. Something in the 95-96dB range would be considered high, which is why some of the Klipsch around 100dB are considered rather high sensitivity.
     
  12. Robert_J

    Robert_J Lead Actor

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    Not when the marketing department is involved. That's why I like the smaller companies. They have technical guys that write their marketing and it's closer to what is true. Look at SVS. No outrageous claims. eD - no claims at all, just specs and pictures of how they build stuff. What more is required?
     
  13. Mr645

    Mr645 Stunt Coordinator

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    Watts per channel is really a rather useless figure. I recently tested a receiver rated at 110wpc and then an external amp rated at 85wpc. The 85wpc external amp delivered 5 db more sound then the 110wpc one, meaning that the 85wpc amp was nearly 4 times more powerful then the 110wpc one.
     
  14. heart123

    heart123 Auditioning

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    Great photos!Thanks for sharing![​IMG]
     
  15. raehza

    raehza Stunt Coordinator

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    Sorry to highjack this thread but I also have a quick question about dB's. I read the article David Willow posted. For example, my Center channel is at 92 db sensitivity. Does that mean that when I set my Receiver to 0 db (reference volume), my center is running at 92db + 4db due to it being in a room - 6db since I sit 6 feet away from it = 90db? So at 0db on my receiver, my receiver sends out 1 Watt to the speaker? And if I set it to +6db on my receiver (which I think is the max it let's me, I never tried), my speakers will run at 96db @ 6 WPC? I don't think that this is correct, I probably misunderstood something here. Ray
     
  16. Mr645

    Mr645 Stunt Coordinator

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    typically a 92 db rating means that with a 1 watt signal, the speaker should be playing at 92db when measured from 1 meter away. Go up to 2 watt and you should be at 95db. Everytime you double the power, you add 3 DB in volume
     
  17. Al.Anderson

    Al.Anderson Cinematographer

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    Here's a couple sites you may find useful. http://myhometheater.homestead.com/splcalculator.html http://www.engineeringtoolbox.com/adding-decibel-d_63.html (Links codes don't always work for me, so I included text versions too.)
     
  18. pfar

    pfar Stunt Coordinator

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    I know exactly what you are trying to say. I'm wondering if this is correct as well. At 0 dB on the reciever volume level if that means it is just making the 1 watt of power to bring the speakers up to their speaker sensitivity level
     
  19. John Garcia

    John Garcia Executive Producer

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    No, because there are quite a few more factors than just how far you sit. Room size, whether or not the room is "active" adding more SPL, and power draw is not a straight forward thing - it depends on what you are listening to as impedance varies with frequency played, so the power used will vary. Yes, typical listening is generally only using a few watts, however large peaks (explosion or heavy music passage) may demand 10X power from the amp.
     
  20. apn73

    apn73 Stunt Coordinator

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    To continue the earlier conversation about speaker ratings in terms of wattage, it is important to remember that you may be producing 90 db with only 1 watt, that's pretty darn loud. What does it say about all of these ratings when you can throw that kind of sound with only 1 watt? As Robert pointed out above, take those ratings with a very fine grain of salt because they do not mean as much as you might think. To the OP, there are several writers within the audio world that can spell all this out very clearly, and even make your head spin about. Here is a short list, Google some of them and read their writings, very enlightening. D.B. (Don) Keele David Clark Floyd Toole Siegfried Linkwitz John Eargle Tom Nousaine David Rich Peter Aczel
     

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