Power hungry speakers

Guest · Mar 13, 2004

AP,
I don't think anyone here is really forgetting what you brought up.  Your recent observation has been a non-issue throughout the length of this thread.  No one here is discussing the perceived increase in loudness (db) between varying amounts of power output.  You bring up an important point, but no one here is arguing over it, so sorry to dissapoint you.  

For anyone unaware of this phenomenon, one must double the amplifier's output to notice a 3db increase in loudness.  

best,

Guest · Mar 13, 2004

Zumbo,
You must remember to be very careful with your 4ohm setup.  Properly designed amplifiers should (theoretically) increase (double) their output as the resistance goes up.  The 1400 and 2400 have a limiter built in to reduce current as the impedence # drops.  This is to protect the unit from damage.  Just remember to not crank it up too much with your 4ohm speakers and you should be fine.   If you do this, then the speakers will be requiring more juice while your amp is dishing out a reduced amount.  In reality, an amp should be putting out more juice in relation to the demand(s) of your speaker(s), not less.  

Please ignore this post if you are using external amplification in your setup!

Oh yeah, I would rather keep my 2400 than get an H/K unit.  But that does not mean that H/K doesn't have their strong points as well.  

best,

zumbo · Mar 13, 2004

I have ordered a Adcom GFA-7605 amp that is rated @175x5 into 4ohms. SIMULTANEOUSLY

My Yamaha is stable down to 2ohms! It drives the Quarts with ease. But, like you said, it looses some authority. This is why I decided to upgrade!

P.S. I think you have to choose to lower the resistance by setting output to 6ohms on the receiver. I left it set to 8ohms in order to get the full available output of the amp.

zumbo · Mar 13, 2004

Can't seem to find where H/K is stable at anything less than 8ohms.

Only poor quality amps can not handle low impedance loads!

Guest · Mar 13, 2004

Zumbo,
Congrats on the purchase of your new toy!  Be sure to let us know how it works out for you.

"P.S. I think you have to choose to lower the resistance by setting output to 6ohms on the receiver. I left it set to 8ohms in order to get the full available output of the amp."

True.  However, if you leave it in the 8ohm position, it has a higher chance of damaging the internal amp if you push it too hard.  Product lifespan will most likely be reduced.  But then again, hopefully the limiting circuit will kick in before something serious happens.  I'm on a tight budget at the moment so I can't be as risky as others.  If you like living life on the edge,,,then go for it!

best,

zumbo · Mar 13, 2004

Yeah, that's why I chose to add the amp. I hope it will sound as good as it does now. Hopefully, it will be more dynamic. I will certainly be back to brag, or due to my honesty, inform everyone of how it let me down. I am my own worst critic.

I would like to add that the sound is quiet impressive at the moment. I am satisfied with the performance. I am adding the amp to take stress off of my receiver & hopefully increase soundstage & get the peak performance out of each of my MB Quarts. I also got an unbelievable deal on the amp from an authorized dealer with a full five year warranty! I have no warranty on my receiver. I couldn't resist the price.

pam · Mar 14, 2004

Hi

I get the part about W=VxA. I also get the 55% of A/B amplifier class.

Now, if I use a 8 ohm speaker and I get 100 Watt and with a 4 ohm speaker then I will get more watts (let say 165 Watt).

If we have 55% efficiency with 100 Watts in 8 ohm. Then the total Power used is about 181 Watts. Getting 165 watts in 4 ohm would means 91% efficiency.
This would also mean that their is less heat with 4 ohm speakers than with 8 ohm.

Thanks

zumbo · Mar 14, 2004

More heat and distortion when running 4ohm speakers on an 8ohm amp. Also, not all amps can handle this load!

annunaki · Mar 16, 2004

pam : Hi

I get the part about W=VxA. I also get the 55% of A/B amplifier class.

Now, if I use a 8 ohm speaker and I get 100 Watt and with a 4 ohm speaker then I will get more watts (let say 165 Watt).

If we have 55% efficiency with 100 Watts in 8 ohm. Then the total Power used is about 181 Watts. Getting 165 watts in 4 ohm would means 91% efficiency.
This would also mean that their is less heat with 4 ohm speakers than with 8 ohm.

Thanks

IF, an amplifier is capable of running a 4 ohm load, it may or may not give you more power into the 4 ohm load. It depends on the amplifier design. If it is a regulated design, it may actually output the same amount of power into 4 ohms as 8 ohms. Some (really well made) amplifiers will double their output as you decrease the resistance (8 ohms to 4 ohms, 4 ohms to 2 ohms). MOST receivers do NOT follow the latter description. However, in any case, this CANNOT improve the efficeny of the amplifier class. Remember that power flows more freely into lower impedences. Also, remember that the wattage (and or current) draw from the wall, on almost all receivers and amplifiers is tested with an 8 ohm load on the channels. By putting a 4 ohm load on an amplifier, it will draw more from the wall if the design allows (being it will double it's power into half the impedence). Power output is a product of current drawn times the efficency. The amount of current drawn is in direct correlation with the output of the amplifier minus wasted power (efficency, power to run displays, ect.).

In your equation above, if an amplifier were capable of 100 watts rms power at 8 ohms all (7) channels driven simultaneously, the receiver would draw from the wall, roughly, in the neighborhood of 1,273 watts of power or 10.6 amperes.
To figure this out we take 100 watts x 7= 700 watts divided by amplifier (class A/B) efficency average of 55% we get 1272.72 watts. To find amperage simply divide by 120 = 10.6 amperes. Now, IF that amplifier were capable of nearly doubling it's power (roughly 2/3's more) to 165 watts into 4 ohms x 7 simultaneously the wattage draw would increase to about 2100 watts (17.5 amperes) of current draw.
We arrive at these numbers by the following:
165 x 7= 1,155 watts
1,155 watts divided by .55 (55% efficency class A/B) = 2,100 watts
2,100 watts divided by 120 volts = 17.5 amperes
If a receiver or amplifier were capable of this kind of power, it would require it's OWN 20 AMPERE CIRCUIT!!

As far as heat goes, heat increases as the impedence drops as the aplifiers devices have to work somewhat harder into the lower impedence. If a receiver or amplifier were truly capable of the above, there would most likely not be a large difference in heat. If you were to go to 2 ohms, there would be a definite increase.

annunaki · Mar 16, 2004

Guest : Actually, I'd be a little cautious when reading rags like HT-magazine. The have rated prior 2000 series yamaha's in the past with higher power output than current models. Its highly questionable, considering the newer 2400 model has larger caps, transformer, and is built better. Given that they recently rated the 2400 with significantly less wattage, it makes one wonder what the boys over in their lab are smoking. Also, their figures used to match up more closely with sound and vision's, but now they don't...go figure...

jdueitt,
As you duley noted, there are many more variables and factors involved with an amplifier's true output, despite a given "power consumption" label on the back. The retention/storage of the capacitors and their voltage wasn't even mentioned in the long-winded debate that this thread endured.

best,

Sound & Vision discovered the same thing with the April 2003 review of the Yahmaha RX-V730. Yahmaha does't cut it when driven all channels simultaneously.
RX-V730 Yahmaha rated to do 75 watts rms x 6.
Actual output at clipping (1% THD) into 8 ohms
26 watts rms x 6 all channels driven simultaneously at 1khz
85 watts x 2 two channels driven simultaneously at 1 khz

Guest · Mar 16, 2004

"Remember that power flows more freely into lower impedences."

I don't follow you on this point.  The lower the impedence of the speakers, the more they will resist the power going to them.  Thus, more strain will be put on the amp to keep up with the resistance the speaker is presenting.  The only way this resistance is overcome is to throw more power at the speaker.  Throwing more power at the speaker is something a properly designed amp should do.  However, as you noted above, most companies either limit or restrict the output instead of increasing or doubling, in order to not damage the unit.  At the ~$1000 price point, I wouldn't expect to see this level of performance.  But at a certain price point one should demand it!

The wattage formulas you presented are a little too simplistic, they would be better suited in calculating the output of a perfectly designed amp in a test environment with all controlled variables.  However, amps, especially those in $1000 units in real world situations do not go by the guidelines you listed.  The "power consumption" on the back does not give one an accurate starting point in the determination of the capabilities of the amp inside.  There are many more factors, capacitance and switching power supplies being some of the major ones.  Most of the amps being discussed here are those in units like the 3803 and 2400.  These types of units are not strict class A/B discrete designs.  Those types of amps usually double as space heaters in the winter time.  Most of the units in the discussion at hand are MOSFETvariants.

best,

annunaki · Mar 16, 2004

In response to some of the posts about capacitors and such in the amplifier sections. Most capacitors are designed for  power storage (in the output section), which are released when needed, i.e. dynamic peaks and such. When a receiver is being tested for contiuous output power, there MIGHT be enough power in reserve for a peak increase of around 1db or so. Some amplifiers may be capable of 2db or even 3db dynamic output, however, these statements usually are not accompanied by any sort of time frame measurement. At least in dealing with the capacitors on the output stage of the amplifier.
As far as caps for the power supply are concerned, most are used as filtering capacitors not so much for storage.

Guest · Mar 16, 2004

"At least in dealing with the capacitors on the output stage of the amplifier.
As far as caps for the power supply are concerned, most are used as filtering capacitors not so much for storage."

True, there usually are a good number of  filter caps in a unit like we are describing, but they pale in comparison to the much larger (higher voltage and capacity) caps on the power output side of the equation.  Generally there are 2 larger caps in the retention and output stage(s).  And, you can not just "turn off" the larger output caps when doing benchmark testing, they are always a factor when testing a receivers capabilities.  Unless you know how to deactivate the output caps???  When these receivers are being tested for their power output with 5 or 6 channels driven (until clipping usually, which I would consider dynamic), the caps are most certainly being put into 5th gear and are being fully exploited!

Are you still asserting that speakers with lower impedence ratings are easier to drive?

Are you saying that in a MOSFET structured amp, the caps are not a factor in power output and dynamic capability?

best,

annunaki · Mar 16, 2004

Ross, power flows to the path of least resistance. 4 ohms presents less retsriction to the power flow than does 8 ohms. 0 ohms, if there was such a thing, is a short circuit. The lower one goes in impedence the closer you get to short circuit. Why do you think an amplifier would shut down or burn up if you put a 2 ohm speaker on it, when it is not stable to that impedence? We as consumers should demand receivers and amplifiers with competent enough power supplies to drive 4 ohm loads on every channel simultaneously while doubling the power from 8 ohms. A well made amp will double its power with the halving of impedence. 8 ohms to 4 ohms to 2 ohms (100watts>200watts>400watts).

To be honest Ross, if you can show me one of the current receivers out (other than the digital path receivers[full range class D, or a Tri-Path design]), that does not have a Class A/B topology I would be VERY surprised. Sure some may use a PWM (pulse width modulated) power supply but they are still in effect Class A/B topology. How is my formula too simplistic? Sure I generalized the efficency, and left out the draw of the pre amp (very minimal), but in effect it is pretty close.

An amplifier CANNOT produce more power than it uses. The best it could do, would be to output exactly what it draws, giving it 100% efficency which really is not possible as there is always some loss in the devices What you are saying is that an amplifier can produce more power than it draws making its efficency higher than 100%. Granted an amplifier can draw more current from the wall, if you put 4 ohm loads on the channels, but what you are talking about is free power. Basically that the amplifier is making more power out of what is already there.

The most efficent designs currently available would be Full range Class D and the Tri-path design (which fundamentally is full range Class D). Their efficencies usually are around 70%-85%. Meaning minimal losses in heat.

annunaki · Mar 16, 2004

Guest : "At least in dealing with the capacitors on the output stage of the amplifier.
As far as caps for the power supply are concerned, most are used as filtering capacitors not so much for storage."

True, there usually are a good number of filter caps in a unit like we are describing, but they pale in comparison to the much larger (higher voltage and capacity) caps on the power output side of the equation. Generally there are 2 larger caps in the retention and output stage(s). And, you can not just "turn off" the larger output caps when doing benchmark testing, they are always a factor when testing a receivers capabilities. Unless you know how to deactivate the output caps??? When these receivers are being tested for their power output with 5 or 6 channels driven (until clipping usually, which I would consider dynamic), the caps are most certainly being put into 5th gear and are being fully exploited!

Are you still asserting that speakers with lower impedence ratings are easier to drive?

Are you saying that in a MOSFET structured amp, the caps are not a factor in power output and dynamic capability?

best,

I NEVER stated that a 4 ohm load was easier to drive than a higher one on an amplifier. Power flows more easily into a 4 ohm load than an 8 ohm one. NOT a 4 ohm load is easier to drive than an 8 ohm one.
Ross, I think you misunderstood what I was saying about impedence. Yes, a lower impedence load is harder for an amplifier to drive, as it requires higher current run through it.
As far as the caps go no. I do believe that they are factored into the ouput. At near clipping, like you stated, the caps are usually at about four fifths or so drawn. How can they really benefit any more? At this point the amplifier would be drawing at or near it's wattage consumption from the wall. Any higher and you will either get a lot of clipping and/or the current limiting circuitry kicks in.  

annunaki · Mar 16, 2004

Ross, are you insinuating that when a manufacturer rates a receiver at say, 75 watts rms x 6, 20hz-20khz, into 8 ohms, at .1% thd, all channels driven simultaneously, that the amplifier can produce more power without drawing any more current from the wall?
In this case or any it is not possible. Why because the caps and power supply are nearly fully taxed before clipping. If we go any higher in wattage output at this point distortion will increase significantly, as will our current draw. If we drop the impedence on our system to say 4 ohms and power output doubles to 150 x 6 we have also now doubled the current draw. Unless of course the efficency of the amplifier could somehow increase, but it can't. As total output power decreases so does our current draw from the wall.

Guest · Mar 17, 2004

Reading this tread entirely makes me crave for more. While JDueitt put a strong critique to halt all arms  and nonsense for Zumbo,  Annunaki and all others, he (JDuett) did not succeed. Forum is just like a knowledge data base -- for the ignorant to pickup helpul input from the knowlegables. How accurate the input is up to one's digestion and discretion.

I took (others may not)  Annunaki's input of increased signal for HK than Yammy if both has the same watts ratings in surround mode. Almost a week now I bought an Onkyo 701 6.1  100 x 6. From the specs below, can Anunnaki

a) Let me know what my true watt rating in surround mode.
Ampifier Section:
Continuous average power output (FTC)
All channels:
100 W per channel min. RMS at 8 ohms, 2 channels driven from 20 hz to 20 khz with no more than .08 % THD.
125 W min. RMS at 6 ohms, 2 channels driven from 1 khz with no more the .1 % THD.

Continuous power output (DIN) 130 W at 6 ohms
Maximum power output (EIAJ    160 W at 6 ohms
Dynamic power output (stereo) 2 x 230 W at 3 ohms
                                          2 x 170 W at 4 ohms
                                          2 x 115 W at 8 ohms

b) Then what HK AVR mode will be =or> to this Onkyo 701 so I could switch.

Thanks,

Guest · Mar 17, 2004

Annauki,
You must remember that with the yamaha's and onkyo's tested in S&V in recent years have most all had their capabilities published in a consistent maner.  Their wattage output was measured in a very respectable manner, and the low specs you stated were taken after the limiting circuitry had already kicked in.  The actual measurements that these units attained were much closer to their actual spec sheets.  Even though they weren't exactly at or above their specs with 5 channels driven, we can't expect that kind of performance on units costing 1k or less.  In 2 channel mode, they routinely did better.  Go back and check out the review of the marantz 7200 if you want to see piss poor performance with high levels of distortion!  You must be up and above a couple thousand ( for a receiver ) before you reach the performance of even cheaper separate amps.  

I guess the major point I was trying to get across is that most all amps are doing different things in their operation(s).  I don't think broad generalizations and simplified formulas can be applied to the vast pool of amplifiers we use in our systems.  The published spec sheets from manufacturers are usually the last place I look for solid facts.  They are usually just one-sided, biased marketing tools.  

"We as consumers should demand receivers and amplifiers with competent enough power supplies"

I wholeheartedly agree, but at a different price bracket than you do.  

brochini,
My whole point is that none of us here can simply look at the spec sheets the manufacturer of your receiver publishes and accurately formulate its output.  Due to the diversity, proprietary variances, numerous variables, etc., we can not incinuate much about your unit.  However, most of us have been in the hobby for a number of years and can make assumptions or estimates based on prior versions and experiences.  

I will tell you that the H/K 7200 is on closeout (authorized sellers) for roughly $700 bucks right now.  AND IT WILL ABSOLUTELY SMOKE THAT ONKYO YOU HAVE!  How much did you spend on that 701?

best,

annunaki · Mar 17, 2004

Guest : Annauki,
You must remember that with the yamaha's and onkyo's tested in S&V in recent years have most all had their capabilities published in a consistent maner. Their wattage output was measured in a very respectable manner, and the low specs you stated were taken after the limiting circuitry had already kicked in. The actual measurements that these units attained were much closer to their actual spec sheets. Even though they weren't exactly at or above their specs with 5 channels driven, we can't expect that kind of performance on units costing 1k or less. In 2 channel mode, they routinely did better. Go back and check out the review of the marantz 7200 if you want to see piss poor performance with high levels of distortion! You must be up and above a couple thousand ( for a receiver ) before you reach the performance of even cheaper separate amps.

I guess the major point I was trying to get across is that most all amps are doing different things in their operation(s). I don't think broad generalizations and simplified formulas can be applied to the vast pool of amplifiers we use in our systems. The published spec sheets from manufacturers are usually the last place I look for solid facts. They are usually just one-sided, biased marketing tools.

"We as consumers should demand receivers and amplifiers with competent enough power supplies"

I wholeheartedly agree, but at a different price bracket than you do.

brochini,
My whole point is that none of us here can simply look at the spec sheets the manufacturer of your receiver publishes and accurately formulate its output. Due to the diversity, proprietary variances, numerous variables, etc., we can not incinuate much about your unit. However, most of us have been in the hobby for a number of years and can make assumptions or estimates based on prior versions and experiences.

I will tell you that the H/K 7200 is on closeout (authorized sellers) for roughly $700 bucks right now. AND IT WILL ABSOLUTELY SMOKE THAT ONKYO YOU HAVE! How much did you spend on that 701?

best,

Why then in reviews, is it not stated that the limiting circuitry kicked in, thus lowering the power output. If a receiver's limiting circuitry is kicking in at .1% thd, or even 1% thd it is a pretty poorly made unit in my opinion.
What I do not get is how many people defend these so called world class companies that are basically ripping people off because current laws and regulations allow. The current FTC rating on surround receivers is the same for 2 channel stereo units. This is bad. Why? Because the receiver only needs to meet the power spec while driving 2 of the 5-7 channels at a time. SOME receiver manufacturers have realized they can maximize profits because of current rating specifications (regulations). Instead of using a power supply capable of driving all channels to rated power continuously they simply use a smaller one to get 2 channels up to rated power. They still meet the guidelines and they just saved a lot of money. While I do not doubt most receivers performance into two channels, multichannel operation leaves MUCH to be desired on many.

Why can't we or shouldn't we expect that kind of performance less than a $1,000. Harman Kardon and NAD seem to have no troubles doing that whatsoever. Are they doing something different than everyone else? You bet, they are giving you the power you expected from the receiver. Exactly what it stated on the box literature, ect.

Separate amplifiers are definitley a great alternative, and I do understand that they do outperform their "all in one" counterparts. However, is it so much to ask to get what is expected?

Why does everyone think electronics amplifiers, wattage current draw, ect. is so difficult. (I x V)= Wattage, That was tough. (I meaning current in amperes V meaning voltage). The only broad generalization I used was efficency. Current consumtion specifications are much more tightly controlled than wattage. All amplifiers try to do the exact same thing amplifier a lesser signal without adding anything extra. Nearly all receivers are Class A/B (other than the digital path units). If one class A/B amp does something different than another, generally speaking, it is most likely a SMALL efficency difference. An amplifiers output is directly proportional to its current drawn. Show me an amplifier that disobeys this principle and I will buy it, as it just does not happen any other way.

I do not trust manufacturer's specs that often either. However, there are certain things they have to be honest with and power consumtion is one of those. The last place you or I may look for specs may be the manufacturer, but many consumers take those specs as truth, unfortunately. That is why manufacturers need to be honest.

Cheers!

Guest · Mar 17, 2004

"Why then in reviews, is it not stated that the limiting circuitry kicked in, thus lowering the power output."

It does actually refer to this in the "LAB NOTES" section at the end of the review.  I have also spoken with yamaha reps, and some of their engineers regarding this matter.

I do agree that if not one is a newbie or not privy to all this "truth", that they are getting ripped off. I just don't let it bother me because I know joe-six-pack that picked up a sony unit from Best Buy and is pushing some cerwin vegas will never know the difference.  But yes, we should expect more from the "world rekown" companies we all gab about.

best,

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