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bmc

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Posts posted by bmc


  1. Only the first paragraph in quotation marks is from Wikipedia.

     

    https://en.wikipedia.org/wiki/Clipping_(audio)

     

    I wrote the rest.

     

    6 hours ago, Snoopy8 said:

    It says may be able to run 2 channels to a decent level/ but is not definitive. 

    I chose not to make a sweeping statement about an entire class of audio product.

     

    6 hours ago, Snoopy8 said:

    The author was being kind saying not exactly BS.  If putting 1 channel numbers at 1 kHZ with high or no THD levels is not BS, what is?  It is designed to trick the uninformed

    To me BS is an outright lie. Figures quoted in this manner are not lies, but I agree they are designed to portray the product in a favourable light to influence the uninformed.

     

    6 hours ago, Snoopy8 said:

    I can imagine the best Class A/B amps can operate at 70% but I doubt that the cheap ones in AVRs can reach 60% efficiency.  There are not many AVRs with Class D amps.  I know the Anthem MRX 1120 uses Class D for surrounds.  The NAD 778 uses better Class D.

    I'm not sure what your point is here.
     


  2. From Wikipedia:

     

    "When an amplifier is pushed to create a signal with more power than its power supply can produce, it will amplify the signal only up to its maximum capacity, at which point the signal can be amplified no further. As the signal simply "cuts" or "clips" at the maximum capacity of the amplifier, the signal is said to be "clipping". The extra signal which is beyond the capability of the amplifier is simply cut off, resulting in a sine wave becoming a distorted square-wave-type waveform.

    Amplifiers have voltage, current and thermal limits. Clipping may occur due to limitations in the power supply or the output stage. Some amplifiers are able to deliver peak power without clipping for short durations before energy stored in the power supply is depleted or the amplifier begins to overheat."

     

    With multichannel amps each channel draws what it needs form the power supply. When the total drawn by all the channels reaches the maximum capacity of the power supply you get clipping. There is no "allocation" of power.

     

    Cheap AVRs will have an inexpensive power supply which may be able to run 2 channels to a decent level but will be unable to run all channels at that same level.

     

    More expensive AVRs (Arcam) will have bigger power supply which will enable all channels to run at  a high power level simultaneously. They will produce even more power per channel if only running 2 channels (subject to output stage and thermal limitations).

     

    Naturally cheap AVRs specs won't quote power with all channels driven as it will be a low figure. They might also quote power into 6 ohms instead of 8 ohms, at just 1kHz instead of 20-20kHz, and with high or unspecified distortion levels. Not exactly BS but not very informative.

     

    You can use the max power consumption as a rough guide to the capacity of the AVR's power supply, keeping in mind that different amp classes have inherently different efficiencies (i.e class A/B 60-70% efficiency, class D over 90%) and hence different power supply requirements. 

     

     

     

     


  3. I'm not sure what you mean by smart re-allocate power. 
     

    The limiting factor is usually the amps power supply. Each channel draws what it needs from the power supply. If some channels are not operating that leaves more power supply capacity for those that are. 
     

    All AVRs using a single power supply will produce significantly more power per channel into 2 channels than 5 or 7 or 9.


  4. The specs given by Yamaha for the RX-V3073 are pretty clear 

     

    Rated Output Power (20Hz-20kHz, 2ch driven) 150W (8ohms, 0.06% THD)

     

    Those for the Powernode are somewhat vague

     

    60 Watts x 2 into 8 ohms

     

    i.e no frequency range or distortion level given.

     

    The Yamaha will definitely deliver significantly more power in stereo mode and plenty to drive Dynaudio Emit 20.

     

     


  5. 46 minutes ago, blybo said:

    Do LSX have active crossover control? I'm not sure if damage is prone in the tweeter or bass driver, just repeating what I've read previously

    The LSX has a hi-pass filter adjustable from 50-120 Hz for use with subs.

     

    Also, though I've seen pictures of damaged LS50 base drivers which have been overdriven, but I'm pretty sure the active LS50W and LSX use DSP to prevent this.


  6. 1 hour ago, blybo said:

    I'd be really happy with LSX or LS50 as long as you aren't after high volumes. Anecdotally I've heard the UniQ drivers are prone to damage if driven hard. I'm still looking at a pair of LSX for my home office, but they will not be listened to loudly.

    Surely this wouldn't be a problem if the bass was filtered off and sent to the subwoofer(s).


  7. I have no angst against Bose. The OP was looking for alternatives to Bose, so I put forward the Sony's which have been often been cited in reviews as being superior to the  Bose (which are themselves top class NC performers). I also noted that some people have had reliability issues with the Bose, just as some people have apparently had issues with the earlier Sonys. 


  8. Gold 50 was the replacement for the GX50. Surface of the Gold 50 woofer has dimples kind of like a golf ball. GX50 woofer has radiating ridges. Gold 50 has a fabric grill while GX50 has a perforated metal grill. Otherwise they look the same. I don't know if they sound much different.


  9. You are correct that low frequencies appear to be non directional, but the idea of using 2 subs is not to create a stereo effect but rather to smooth out peaks and nulls in the frequency response caused by the acoustics of the room.

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