THE ALL CHANNELS DRIVEN FALLACY

[anamorphic96]

The Sony only puts out 100 watts into each individual channel. But not with all channels driven at once. It also definitely does not put 700w into each channel. Sony also has questionable ways in which they measure this. They alot of times ony measure the power into 1khz. Which is a very easy frequency to produce and obtain 100 watts with.

Why dont you give us the model number of the Sony so we can better help you interpret the specs.

Also let us know what kind of speakers you are using and what there specs are as well. So we can help you get matched up with something that will work for you better.

Audioholics also has reviews of sub 500 dollar receivers as well. So do alot of other publications. You just need to look some more.

 

[mtrycrafts]

If you are still stressed out and want to throw the receiver against the wall, find a less stressful hobby. Perhaps fishing

LOL. What will he do when the hooks don't catch any fish? Throw them against the wall too?

 

[hydro]

Hi All
Its a str de-897. I am using cerwin vega v-15s for left and right cerwin vega v10's for rears and a klipsh center speaker and I mean there is a HUGE difference before I never turned the dennon up more than half I run the sony 70 out of 75 to watch movies sometimes max and for music even max is not loud enough when we have a few people over.

 

[markdi]

I have a old hk avr 5 - I use it in the bedroom now.

a buddy of mine dropped his avr 5 down a flight of stairs.

I installed his power transformer in parallel to the one in my avr5.

I put a big 40 amp metal bridge rectifier and much larger capacitors in the supply.

a little lm 317 regulated power supply - set at 8 volts powers 4 little 12 volt fans blowing air up thru the stock heat sink - they make no noise - cant hear them.

a simple 555 timer circuit and a relay and a resistor - powered by the lm317 supply provides power up current inrush limmiting.

using my tektronics 794 d ociloscope and pink noise generator - and some music my avr 5 went from about 38 watts - all channels driven to about 78 watts - all channels driven at the same time.

the avr 5 has pre outs for all 5.1 of it's channels

so I used my 3 adcom gfa1a amps to power the woofers and the amps in the avr 5 to power the mid - tweeter drivers.

I used a simple little passive crossover circuit I found on a website to split the audio signal between the amplifiers - 12 db per octave and no added noise - crossover frequency 400 hz.

the adcom amps had more gain than the amps in the avr 5 - easy I just used 5 little trim pots.

the switched outlet on the avr 5 turned on 40 amp relays that turned on the adcom amps - the whole system was powered by 3 seperate 120 volt 15 amp feeds.

5 - 15 inch 3 way speakers and a projector.

I kinda miss that setup.

a panasonic dvd a7 with dvd audio was my main signal source - it rocked - scared children and the elderly.

the hk avr 5 has a pretty good signal to noise spec at it's pre outs.

 

[hydro]

Ok folks can some one tell me what this is really saying?

Fully Discrete, Equal Power 7 Amplifier Channels, 75 Watts Each
Front 75 W + 75 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)
Center 75 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)
Surround 75 W + 75 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)
Surround Back 75 W + 75 W (8 ohms, 20 Hz - 20 kHz, 0.08 % THD)
For optimum Dolby Digital and DTS reproduction, the AVR-486 features high quality, wideband audio amplification, providing 75 watts power output for each of the 7 main channels. A large capacity power supply includes a high current power transformer along with discrete power output devices on all 7 amplifier channels for highest dynamic range and superb reproduction clarity.

Did that say 75 watts divided by 7 or multiplied by 7?

 

[Nick250]

They are saying 75 times 7. In the real world it will most likely be less than that because they ususally fudge the numbers some.

 

[Buckeyefan 1]

hydro:

Did that say 75 watts divided by 7 or multiplied by 7?

Neither. They are saying the amplifier will deliver 75 watts rms into one or two channels maximum at those given parameters. Now for your homework, figure out rms (root mean square).

 

[hydro]

Neither. They are saying the amplifier will deliver 75 watts rms into one or two channels maximum at those given parameters. Now for your homework, figure out rms (root mean square).

Well here goes.
So what does root mean square (RMS) really mean?
First square all the values, then find the average (mean) of these square values over a complete cycle, and find the square root of this average. That is the RMS value. Confused? Ignore the maths (it looks more complicated than it really is), just accept that RMS values for voltage and current are a much more useful quantity than peak values.

Or the short version

Instead we use the root mean square voltage (VRMS) which is 0.7 of the peak voltage (Vpeak):

VRMS = 0.7 × Vpeak and Vpeak = 1.4 × VRMS
Now isn't that clear as mud.

Ok buckeyefan but you are saying that when all channels are running the 75 watts are split into all seven channels meaning 10 watts a channel.

 

[mike c]

does the claim "equal power (for all channels)" by denon equate to all channels driven?

 

[mtrycrafts]

does the claim "equal power (for all channels)" by denon equate to all channels driven?

No. It means that each channel can deliver 75 watts of power. Some, or in the older days had lesser power to the surround channels, such as 25 watts or 50 watts while the fronts had 75 or 100 watts. So, equal means each ch are the same.

 

[westcott]

does the claim "equal power (for all channels)" by denon equate to all channels driven?

The tests I saw on Sound and Vision for the 3805 show that they are "fairly" equal with all channels driven. I think the figures say that it provided 105 watts per channel with five channels driven.

 

[gene]

Neither. They are saying the amplifier will deliver 75 watts rms into one or two channels maximum at those given parameters. Now for your homework, figure out rms (root mean square).

RMS power is a bit of a misnomer:

Here is a good reference to why: RMS Power Article

 

[gene]

The tests I saw on Sound and Vision for the 3805 show that they are "fairly" equal with all channels driven. I think the figures say that it provided 105 watts per channel with five channels driven.

A test that uses a VARIAC to hold the line voltage constant and does a momentary sweep (NOT Continuous power) with all channel driven into clipping.

 

[hydro]

Neither. They are saying the amplifier will deliver 75 watts rms into one or two channels maximum at those given parameters. Now for your homework, figure out rms (root mean square).

Sooooooooo
Lets say I am watching "The Gladiator" and he is in the arena and th crowd is roaring so the sound has to come from all the speakers at the same time is there 75 watts to each speaker or about 11 watts? That is what I want to know and how do I get the former not the later
Joe

 

[westcott]

A test that uses a VARIAC to hold the line voltage constant and does a momentary sweep (NOT Continuous power) with all channel driven into clipping.

Agreed. Definately not RMS. I tend to use the numbers generated from these tests to compare one unit against another at that particular site, and not as true values for continuous or peak power or data generated in other manners.

Every site seems to test equipment differently based on resources available. I understand this and can appreciate the limitations of budget and resources. As long as the tests are relevant and consistant, the results can be useful for comparison but are usually exclusive to that site.

 

[gene]

Sooooooooo
Lets say I am watching "The Gladiator" and he is in the arena and th crowd is roaring so the sound has to come from all the speakers at the same time is there 75 watts to each speaker or about 11 watts? That is what I want to know and how do I get the former not the later
Joe

I am not sure where this 11 watt nonsense is coming from but you will almost never be running the same continuous signal into all channels simultaneously. Crowd cheering is not a continuous sine wave like the typical all channels driven test is. Also with most speakers, a few watts driven into them will fill the room with sound, especially with 5 or 7 of them in the room. Most of the power is consumed by your subwoofer(s), not the speakers, especially if you applied bass management to all of your speakers.

I suggest reading this thread from the beginning to get better insights as to how power is rated and measured.

 

[hydro]

Hi Gene I have read the whole thread up till here, And basically what I have learned is that the manufactures bend the equations to make themselves look good, the retailers use those numbers to imply things they are no where near close to delivering and even the reviewers can't be compared except to themselves. And I know this my 175 watts per channel amp makes 175 watts for 20-20k on the right channel "AND" 175 watts on the Left channel, and draws 1200 watts to do it. My Av receiver makes up to 100 watts to any one channel or 50 to two and so on and can do it while drawing only 285 watts, And it should not take any power to run the sub it has its own 300 watt amp. And the real burning question that started this whole soap box rant for me is this...... the two channel amp has a meeter on the front admittedly not laboratory accurate but at 1 watt it is louder than my 100 Sony that even the reviews say 80 to both channels in stereo mode. WHY??????
Sorry to vent, but I don't think I am the only one that wants a real answer
Joe

 

[MDS]

Hi Gene I have read the whole thread up till here, And basically what I have learned is that the manufactures bend the equations to make themselves look good, the retailers use those numbers to imply things they are no where near close to delivering and even the reviewers can't be compared except to themselves.

You failed the course.

 

[mike c]

please correct this "theory" if right or wrong ...

Given:
Yamaha has 130wpc (2600) 130 for two
HK has about 75-90wpc (HK635) 75 for ALL, 90 for two.

Conclusion:
Yamaha is capable of higher peaks than HK.

yes? no?

 

[Buckeyefan 1]

please correct this "theory" if right or wrong ...

Given:
Yamaha has 130wpc (2600) 130 for two
HK has about 75-90wpc (HK635) 75 for ALL, 90 for two.

Conclusion:
Yamaha is capable of higher peaks than HK.

yes? no?

Well, that depends. You brought "peaks" into the equation. Peaks, or short bursts, can require quite a bit of current. You would need to compare the power supply (transformer) in each unit, and then compare the capacitors. I would say the unit with the more robust power supply and larger caps would be able to deliver the higher peaks.

Gene usually provides internal pics of AVR's. The higher end Yamaha's seem to have beefy guts, and the 2600 weighs in at almost 40lbs. The HK 635 also weighs around 40lbs. No doubt both have some large heat sinks to dissapate heat. My guess is you'd have a hard time telling one from the other if driven to reference levels and assuming the trims matched as far as tone goes.

One point that's rarely mentioned when comparing "watts" is the speaker itself. An 8 ohm speaker with a mid 90's dB (spl) rating will play plenty loud in the largest rooms with budget surround receivers, while a 4 ohm, mid 80's dB speaker may struggle in a moderate sized room with a higher end AVR.

Bass management, as Gene stated, takes the weight off an AVR's ability to drive demanding speakers. If you are using a separate powered subwoofer, and are crossing over your system at the THX recommended 80Hz, there really isn't any reason to spend large amounts of money on high powered AVR's.

If you enjoy listening to two channel music without a sub at high levels, and have demanding towers, you can always add a separate two channel amplifier for much less than what a flagship AVR will run.