High current design?

[Beckman]

3dB is exactly double the sound output at the same volume level.


What do you mean here? Please explain.

He means

10*log(2*Pout) = 10*log(Pout)+10*log(2) = 10*log(Pout) + 3 dB

I think.

[mtrycraft]

He means

10*log(2*Pout) = 10*log(Pout)+10*log(2) = 10*log(Pout) + 3 dB

I think.

At the same volume level?

[hertz]

Issue of perception comes to mind right out of the gate.

mtrycraft,
I have first hand experience with with my amp (nad c 350) and the audio analoque puccini 50 watter which replaced a Marantz pm 7000 which is a 95 watt amp.I am not imagining things here.
I am fortunate to have a dealer friend who stocks high/mid end equipment.I have had the opportunity to try out different permutations/combinations with his resident speakers which are a pair of cadance hybrids.There is a big difference in capability and musicality when you compare serious hi fi brands to the usual japanese recievers / amps.There are exceptions to this rule though but most of them suck big time.I have come to the conclusion that spec sheets are a waste of time.Give the amp some real work to do and you will see the truth.
What you say might be true in a perfect world.But this is not a perfect world.Most run of the mill amps and recievers cut corners all over the place and they can satisfy a casual audio enthusiast, not someone who knows sound.

[skeptic]

It is not the specifications which are flawed. It is the lack of reading the way in which the measurements are allowed to be made and the ability to interpret their limitations which leads to disappointment and misunderstanding. Audiophiles and other amateurs look for a few simple numbers to describe the relative merits of complex products like audio amplifiers and receivers. In fact, a complete description goes well beyond the pile of charts and graphs tediously amassed by one time audio magazines like Stereo Review, High Fidelity, and Audio. Even they only told you the frequency response at one watt. How much attention do people pay to power bandwidth or distortion for example. A 100 watt per channel amplifier at 1000 hz may only be a 20 watt per channel amplifier at 30 hz especially if it has a power supply with a small transformer and filter caps. The FTC stepped in in the 1970s to put an end to the fake horsepower race some manufacturers were running to make their equipment look good, but mass market producers have figured out ways around that and are now right back in there. How many amplifiers or recievers of 30 years ago couldn't handle a 4 ohm load? Not even one I can think of. If you expect something for nothing, you are asking too much. On the other hand, watch out for the 8 wpc guys who tell you "how sweet it is." IMO, they offer nothing for something.

[Mr Peabody]

OK, now I understand your question. I was trying to say that if you had a speaker at 86dB and another at 89dB playing at the same volume level, the speakers that is 89dB will be twice as loud. So 3dB can make quite a difference.

[markw]

OK, now I understand your question. I was trying to say that if you had a speaker at 86dB and another at 89dB playing at the same volume level, the speakers that is 89dB will be twice as loud. So 3dB can make quite a difference.

A 3 db change in loudness is barely audiable. For an apparant doubling of loudness, you need aproximately 10 times the power.

[Mr Peabody]

It takes 10 times the amplifier power to effect a 3dB gain. That's why a 3dB gain is so significant in speaker efficiency. Which is easier and least expensive to achieve more volume, buy a speaker that is 3dB more efficient or buy an amp 10 times as large? It's a fact 3dB is double the sound, that may not be audible to you, but it's a world of difference to my ears.

[mtrycraft]

It takes 10 times the amplifier power to effect a 3dB gain. That's why a 3dB gain is so significant in speaker efficiency. Which is easier and least expensive to achieve more volume, buy a speaker that is 3dB more efficient or buy an amp 10 times as large? It's a fact 3dB is double the sound, that may not be audible to you, but it's a world of difference to my ears.

Actually, it takes 2X the power for a 3dB spl gain and 10X to gain 10dB spl which is perceived as being 2x as loud.

[mtrycraft]

OK, now I understand your question. I was trying to say that if you had a speaker at 86dB and another at 89dB playing at the same volume level, the speakers that is 89dB will be twice as loud. So 3dB can make quite a difference.

Ok, let's try to clarify this too

You have two speakers. One will play 86dB spl with 1 watt input power. Speaker 2 will play 89dB spl with 1 watt input power. Is this what you are saying?

Then, it takes twise as much power, or 2 watts for the lesser speaker to play 89dB spl. that is barely audible in most cases as was stated.

To perceive it to sound twice as loud though, you need 10 dB increase in power, 10x more power. Perception is different from power doubling and spl changes.

[kexodusc]

It takes 10 times the amplifier power to effect a 3dB gain. That's why a 3dB gain is so significant in speaker efficiency. Which is easier and least expensive to achieve more volume, buy a speaker that is 3dB more efficient or buy an amp 10 times as large? It's a fact 3dB is double the sound, that may not be audible to you, but it's a world of difference to my ears.

Wow, if it takes 10 times the power to get a 3dB gain, you've got some dreadfully inefficient components.

With all respect to the good Mr. Peabody (a respected site regular) I think his statements prove Skeptic's point very nicely.
With all the statistical figures, logarithmic functions, and mathematical interdependance of stereo components, it's pretty easy to get lost in the specs really quick. Everyone is capable of making honest interpretive mistakes. And the fact that manufacturer's love to make interpreting their figures a bit harder doesn't help either.

[skeptic]

You rang?

I wasn't too anxious to reply to this area but perhaps a few points just to clarify some of what has already been said would help.. Two things are being discussed which are getting confused. Power and loudness. Power is a scientific term. Loudness which is related to power is a subjective term, which describes how we react to a physical stimulus of sound. When the power of sound or of the output signal of an amplifier increases by 3db, it is twice as powerful. When it decreases by 3 db it is half as powerful. But being twice as powerful doesn't translate into sounding twice as loud. That is because our sense of hearing is logarithmic. If you don't know what that means, just understand that to get something to sound subjectively twice as loud it may have to be four to ten times as powerful. This is why the db scale was invented in the first place. The linear scale is just not suitable for describing the power range of our sense of hearing. From the theshold of human hearing to the threshold of where pain occurs is often said to be 120 db. That's a range of 10 to the twelfth power or 1,000,000,000,000 to 1. A 3 db change is perceptable to most people but not that significant. It was believed for a long time that 1 db was the smallest increment of change most people can hear. That's a change of 20 percent. Some people may under some circumstances be able to hear smaller increments. For many people that is a wish and a delusion. Only careful testing by audiologists can map your particular sensitivity to sound and only you can tell us when a sound is half as loud or twice as loud as another. When you do, we can tell you how many decibels of change it took to make it that way.

I hope this helps clarify this apparant misunderstanding.

[mtrycraft]

Wow, if it takes 10 times the power to get a 3dB gain, you've got some dreadfully inefficient components.

.

Sorry, that will not happen. It wil still take 2X power to get a 3 dB spl change in those insensitive speakers too

[topspeed]

OK, I've been avoiding this thread but now my curiosity is peaked:

Why aren't there measurement standards in place, especially in the US?

There's a completely inane thread on another board regarding taking a 3805 and biamping your mains with the inboard amps in a 5.1 set-up. Forget for a moment that this is an inaudible waste of time, the point is that there are all kinds of screwy calculations going on stating what the receiver is actually delivering with all 7 channels driven. Denon quotes what, 135wpc? Sound and Vision bench tested it and pulled around 70wpc X 7 at clipping @ 1khz (if I remember right. There's 250+ posts in that argument and I'm not looking for it). Considering there is only one power supply, this isn't surprising. What I want to know is why there aren't solid, measurable standards in place? Autos have SAE or DIN ratings, why not electronics?

[skeptic]

Measurements of electronic equipment in this class evolved probably in the 30s and 40s when amplifier performance was so poor that they could tell you usable differences between amplifiers. BTW, even by those limited standards, most of what you read in advertising and magizine tests are very incomplete. Today, most amplifiers are designed to measure textbook perfect by these historical measurements. However, even so, many manufacturers have found ways to manipulate the measurements to their own advantage either by omission or by adding information that may not be particularly useful to most users.

High current capability is one of them. What does it mean. A "high current" 100 wpc amplifier may have enormous filter capacitors in its power supply which can dump 50 amps into a load for a very short period of time. Into an 8 ohm load, that would be 20,000 watts. How long would this be for? 10 microseconds? 2 milliseconds? After a few dozen or hundred milliseconds or so, it would go back to being a 100 watt amplifier. Is this useful? Can some sharp transient attack played back at some monstorous sound level, over some very inefficient speakers with a difficult load show this capability to advantage over its non high current competitors? This arcane performance aspect could be argued at AES seminars by the likes of John Curl and his counterparts who work for his competitors but in the walking around world of you and me, its only real value is probably for advertising something that the other guy doesn't have. And why is that of any value? Because in an industry of mostly me too designs, there is often little else to distinguisl one product of a type from another.

[Mr Peabody]

I agree that amp gain has been confused with SPL. You stated a 3dB amp gain is barely audible, so I think we are on the same page here. Because as we both stated it would take about 10dB of amp gain to make a difference, or as I stated, I have been taught 10dB of amp gain will equate to 3dB of SPL gain. With 3dB of SPL being exactly double. Do you know the relation between amp gain & SPL speaker level? Do you agree that an 89dB speaker will play twice as loud as one 86dB at the same amp power?

Above is what I have been taught. Here are a couple of examples that tends to make me believe what I have learned. I was thinking of buying a Mac receiver from an electronics tech who owns his service shop. When he played it for me, I told him the balance was off. He couldn't really tell it, so he put it on his test equipment and came back to tell me one channel was 2dB down and the problem was in the volume pot which was expensive to replace. The channel embalance was apparent to me.

My son had a pair of Infinity Studio Monitors that were rated in the high 90's SPL or efficiency and I owned a pair of Kappa 7's which were rated at 89dB. One day we were fooling around and I hooked his on one channel and left mine on the other. Granted there is more than a 3dB difference here but I couldn't even hear my speaker when they were both playing, not even the extended low end from my speaker, nothing. I had to unhook his to be sure mine was working.

Also, I put my line of thinking to work in my car audio system with success. I had installed some Infinity Kappa components which were 89dB or less. When I let my daughter take over driving this car she eventually blow a couple of my drivers trying to share with the rest of the world what she was listening to. I told her she had to replace them. She wanted louder, but couldn't aford a larger amp, so I told her when she replaces the speakers to buy more efficient/higher SPL rated speakers. So she bought some Boston Acoustic that were somewhere in the low 90's and with the same amp they will make your ears bleed (figuratively only).

[mtrycraft]

I agree that amp gain has been confused with SPL. You stated a 3dB amp gain is barely audible, so I think we are on the same page here. Because as we both stated it would take about 10dB of amp gain to make a difference, or as I stated, I have been taught 10dB of amp gain will equate to 3dB of SPL gain. With 3dB of SPL being exactly double. Do you know the relation between amp gain & SPL speaker level? Do you agree that an 89dB speaker will play twice as loud as one 86dB at the same amp power?

No, it will not sound 2x as loud. That needs a 10dB spl change which needs a 10 dB of power change. Your example needs 2x the power but audibly is barely audible to most people.

Above is what I have been taught.

There are a number of acoustic books out there. You may want to invest a little in one.

He couldn't really tell it, so he put it on his test equipment and came back to tell me one channel was 2dB down and the problem was in the volume pot which was expensive to replace. The channel embalance was apparent to me.

That may be. All depends on what was playing. Low frequency and you would not be able to tell, nor with high frequency. And, it was affecting the whole audio spectrum not just a small snippit, so you detected it. He didn't.

[skeptic]

Several different ideas and terms still seem to be getting badly mixed up here so I will make a further attempt to untangle them.

"Do you know the relation between amp gain & SPL speaker level? Do you agree that an 89dB speaker will play twice as loud as one 86dB at the same amp power?"

This is really mixed up. If you are referring to one loudspeaker having a sensitivity of 86 db and another one having a sensitivity of 89 db, here is what it means. With each speaker having an input of one watt (this has nothing to do with its impedence but with the electrical power it is drawing from an amplifier at a given moment) then one meter away (about 3 feet) in an echoless environment, the more sensitive speaker will emit twice as much acoustical power as the less sensitive one (at least along its axis.) This does not translate into the subjective sense that it is twice as loud. The perception is more likely to be that it is marginally louder due as I said in my previous posting to the logarithmic nature of the sensitivity of human hearing. Within their linear range which means within their ability to increase their acoustical output proportionally with an increase in electrical input, the relationship will continue to hold so that for the same wattage applied to the more sensitive speaker, it will provide twice the acoustical output as the less sensitive one and will be perceived as marginally louder. BTW, SPL stands for the sound pressure level expressed usually in decibels (db). This is the physical intensity of sound at some given spot. Sensitivity of a loudspeaker is just another way at looking at its efficiency of converting electrical power into sound. Be aware that more sensitive doesn't translate into better sound. There is no correlation between sensitivity and sound quality as examples of both efficient and inefficient speakers run the gamut from awful to excellent.

As power levels increase, each speaker will reach a point where further increases in power will no longer produce further proportional increases in sound level. At this point the speaker will begin to distort badly and if sustained or further increased, the speaker will be damaged. How loud either speaker can ultimately play doesn't depend on senistivity but on other factors related to its construction. Either speaker might ultimately play louder and by a considerable margin given enough power.

"I told him the balance was off. He couldn't really tell it, so he put it on his test equipment and came back to tell me one channel was 2dB down and the problem was in the volume pot which was expensive to replace. The channel embalance was apparent to me."

While the absolute difference in loudness of 3 db may be marginal to our hearing, a difference of 2db between two sound sources emitting the same sound at the same time from different directions may be very noticable. Our hearing meaning both our ears and how our brains interprets what reaches them has evolved to allow us detect the direction of the source of sound quite efficiently. This is undoubtedly an important resource for survival for many animals including man to both avoid preditors and locate prey. We use at least two mechanisms to judge the location of sound, one being which ear detects sound first and another which hears it the loudest. There may be other mechanisms we use as well. In a real musical performance, each instrument has a unique location and the sound from that instrument arrives first and loudest from that location. But in the stereophonic system of sound recording, we use only two channels and two loudspeaker systems to simulate up to 100 musicians and 300 voices all coming from different locations. A musician directly in front of us would have his sound arrive at both of our ears at the same time and at the same loudness. In stereophonic sound reproduction, a recording of that musician should be played equally loudly from both speakers to hopefully fool our hearing into judging that it came from a point between the two speakers and not from either one of them (you can see that after 60 years of this you'd think they could come up with something much better.) If the two electrical channels are not perfectly balanced because one channel of the volume control potentiometer is out of balance with the other or because one speaker is more efficient than the other, the entire effect will be altered but can be compensated for by using the "balance control."

In planning a sound system, many experts advise that the speakers should be selected first. This decision has the greatest effect on the quality of the sound you will hear. Once you have selected loudspeakers, select an amplifier that has sufficient power to allow them to play loud enough to satisfy your needs. This will depend on the size and acoustics of your room and your personal preference. It is also limited by the maximum power your speakers can handle. The requirement can vary all over the place. For example, a highly efficient loudspeaker like Klipschorn in a live room of reasonable proportions may only need a 10 watts per channel amplifier to produce very loud music. At the opposite extreme, inefficient speakers that have a sensitivity of 86 db or less may require 100 to 200 watts per channel or more to achieve the same SPL in a large acoustically dead room. This is not to say either one is better than the other.

I hope this clears up some of your misunderstanding.

One last word of advice. Tell you daughter to turn the car stereo down and keep her mind on her driving. I don't want her crashing into me, I don't appreciate her noise when I am stopped in traffic at a light, and I heard the thumping in my house with all of the windows closed the other night when she drove down my street.