Whats All The Noise About?

[davo]

While reading through the 'all channels driven' debarcle, someone (I think it was Clint) breifly mentioned a 'white noise' test that would supposedly clear up the mess of how amps are rated.
Is it possible to find out more about this i.e. how would it work, how does it stop brand names from manipulating figures for their own benifit, are we likely to see it any time soon?

 

[mtrycrafts]

While reading through the 'all channels driven' debarcle, someone (I think it was Clint) breifly mentioned a 'white noise' test that would supposedly clear up the mess of how amps are rated.
Is it possible to find out more about this i.e. how would it work, how does it stop brand names from manipulating figures for their own benifit, are we likely to see it any time soon?

Manipulate the figures? Not sure what you mean?

 

[davo]

Whats all the noise about

Sorry I didnt clarify a bit more. It's common knowledge that most manufactures will embelish the figures on how powerful their equipment is. A classic example is PMPO. Technically speaking it might be true, but it doen't describe the level of distortion occuring at the same time, or if the unit will last more than 5 minutes while performing said PMPO. The same can be said of a car manufacturer claiming a peak power of 300kw (not sure what that is in bhp) at 6500rpm in a vehicle. Technically it might be true but the engine wont last a week if you drive it around trying to keep the revs at 6500rpm. And if your not driving at 6500rpm then you are operating at a lower, and much more realistic, power level. Then you start to look at tourqe levels etc, and you start to get more idea of what it will be like to drive.

So unless manufacturers make power/distortion graphs readily available with their products (dont hold your breath), they will continue to make claims of better products with out really giving you a better product. The reason I wanted to know more about the 'white noise test' is because it will hopefully give people a real bench mark to assess products with. (I'm not sure if it was Clint that mentioned the white noise test. I went back through the entire thread but didn't see it again).

 

[MDS]

Everything you mention was covered in the all channels driven thread.

Excepting useless ratings like PMPO which is only used on 'boom box' like products, manufacturers follow testing guidelines from the FCC, DIN, or EIJA.

There is a good article on this site about 'managing receiver product releases' (can't think of the exact title right now). It goes into all of the possibilities for deriving a power rating. One brand might choose .8% distortion and yield one power rating while a comparable brand might choose .08% distortion and yield a slightly lower power rating. The first is not 'lying' as is commonly alleged. The person wanting a specific number is lying to themselves by imposing their own interpretation of the specs rather than taking the time to understand the tests and actually read what is written.

A classic example is the Yamaha HTR vs RX series. Nearly everyone on this site including the Audioholics love Yamaha and yet some of the members make the claim that Yamaha lies on the specs for the HTR series because they claim something like 140 wpc when the identical RX model only claims 110 wpc. If you actually READ the specs, you see that the HTR model is rated using DIN (1 kHz) and the RX is rated using the FCC (20-20 kHz) rules. Apples to Oranges.

White Noise is noise where the amplitude is equal at all frequencies and would not be a good test for power as it does not correlate with real music. Even if a white noise test were adopted all of the same issues will apply and the same arguments will start all over again.

The only valid argument is whether or not the tests as defined are adequate for rating equipment. The manufacturers rate their equipment according to the rules and the rules allow them some latitude to cast their equipment in the best light to the uninformed consumer.