Question Tell Me About Power Please

Discussion in 'AV Receivers & Amplifiers' started by nheather, Jun 16, 2015.

  1. nheather

    Distinguished Member

    Oct 6, 2004
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    Horsham, West Sussex
    I've been looking at low-profile AVRs such as the Pioneer VSXS310 and the Marantz NR1504.

    Yes I know a full-height one would be a better proposition but I may be short of space. I am trying to rearrange things but let's assume it won't be possible.

    Firstly, this is a secondary installation intended to be done on a budget so I'm not looking for audiophile performance. I will only be using small speakers, like Tannoy TFX, Wharfdale DX-1, Boston Acoustics Soundware (not decided yet).

    I am used to AVR receivers being capable of delivering about 100W per channle into the correct load, but I'm not sure how much I actually use. I don't tend to have it turned up loud.

    My question is particularly about the Marantz.

    The Pioneer claims to be 110W per channel on their website but 65W per channel on the Richer Sounds website

    The Marantz is consistently listed as 50W per channel.

    So what does 50W per channel mean in the real world? Is it ample for small speakers? Will I be driving it close to limits even for moderate volume?

    This is how I think it works. Take the Tannoy TFX with a sensitivity of 85dB.

    1W >> 85dB
    2W >> 88dB
    4W >> 91dB
    8W >> 94dB
    16W >> 97dB
    32W >> 100dB
    64W >> 103dB
    128W >> 106dB

    I can't imagine that I would want to listen above 91dB


    Last edited: Jun 16, 2015
  2. dante01

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    Mar 5, 2009
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    The reason for the differences in rating between Pioneer's site and Richer Sounds' is that the Pioneer site gives a rating in relation to a 4ohm impedance load while the Richer Sounds site state one for an 8ohm load. For most purposes, the 8ohm rating is more generally accepted as being the one to look at unless actually wanting to power speakers with an impedance of 4ohm. Speakers more typically impose a nominal impedance of 6 - 8ohm as opposed to 4ohms, but there are speakers out there rated with a 4ohm nominal impedance.

    Note that when looking at the rated wattage you must ensure that the ratings you are comparing relate to the same impedance imposed. You basically want to be looking at the rating for 8 ohm loads. Also make sure that the number of channels driven is at least two and preferably all of them. While you may get 60 watts two channels driven then you'd get less with more channels driven. I believe the ratings relating to the Pionerr receiver are in fact all channels driven as opposed to 1 or 2 channels driven? 60 watts in this instance would be quite healthy and this is to be expected from a D Class amp such as that employed by the Pioneer receiver.

    The issue wont be driving the speakers, the issue is the size of your room and the distance you are from the speakers. The further you are from the speakers then the more power is needed to drive those speakers to a level that equates to reference level as measured from your primary listening position. A less powerful amplifier can struggle if the distance from the speakers you are is more than you'd expect in an average sized UK room. This means you'll start to hear distortion and the receiver will begin to overheat the louder you need to play the output to attain reference level.

    The receivers you are looking at shouldn't have an issue driving the speakers you have to reference level within a small room, but may struggle in larger than average rooms?

    You may also find this of interest:
    What's up with watts; how many watts do your speakers need? - CNET

    and this:
    Secrets of Amplifier and Speaker Power Requirements Revealed

    The more sensitive the speakers you are powering then the less power they need to attain the reference level or levels of volume you require. Speakers also have a sensitivity rating expressed in decibels. This represents the SPL a speaker can attain per watt of power when measured 1m from that speaker. The higher the sensitivity then the less power those speakers need to attain high volume levels. The sensitivity of a speaker doesn't increase the more power you supply, it remains the same irrespective of the power.

    The reference level I refer to above will be 75 - 85db as measured from your primary listening position during the initial configuration and setup of the receiver and speakers. The receive uses a test tone to measure this via a mic coonected to the receiver. THe reference level is standardised thoughout the movie industry and is the same level used during mixing and in cinemas. It is relatively loud and many find it too loud for home listening, but a receiver and speakers should ideally be able to attain this within the intended listening room. Note that prolonged listening at levels above 90db can cause hearing damage.

    Again, you may find this of interest:
    THX reference level explained - Acoustic Frontiers
    Last edited: Jun 16, 2015

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