Simple resistance and simple impedance are not the same because impedance has a phase component to it.
For the sake of thinking about speaker impedance and amplifiers you can simplify it to resistance.
Speakers however are complex, and the impedance varies by frequency. Take a look at any Stereophile speaker measurement. The phase angle also matters as high phase angles vs. low tend to stress amplifiers more.
Most amps can handle most speakers, but knowing that a speaker has low impedance in certain areas can explain and help guide matching of a speaker to an amp. Not something you care about with normal, commonly available speakers.
It's the exotic speakers and too often, high end speakers, which have impedance issues to be aware of.
I know where you're coming from. Had the same problem as a kid trying to understand cars, how the engine runs, etc. All the other kids seemed so well versed. Wasn't until I got a shop manual and did my own tune ups that I came to realize they were bantering jargon back and forth not really understanding a GD thing.
The more things change, the more they stay the same.
Resistance and impedance are the same in that both describe opposition to the flow of current. The main difference is that resistance depends only on the material and its dimensions, and temperature. Almost all electrical theory is just that, theory, and so with resistance we are dealing with an imaginary "ideal" conductor. So keep that in mind and don't be bamboozled when people try and baffle you with BS.
Resistance then is opposition to flow of current. What about impedance? With resistance we are talking a steady state. But with music we do not have a steady state. Never. It is not a steady flow, it is constantly changing. Every time it changes there is opposition to the change. The amount of this type of opposition is no longer just down to materials, dimensions and temperature. This opposition to change varies with frequency. So we have two different yet related things going on at the same time- the resistance to current, and the way the conductor reacts to changes in current. Which is called, guess what? Reactance!
Impedance includes both resistance and reactance.
So not a troll after all, but just a guy with a good question. Hope this clears it up.
No one can make you feel less confused if you aren't in the habit of learning and doing a little math.
To make this as simple as possible, impedance usually varies by frequency. Resistance does not. So no, you may not substitute one for the other. Take a lookt at the Stereophile speaker measurements to understand this better.
When it comes to speakers, 4 or 8 Ohms is usually literally an eyeball average. At best you may be lucky to get the minimum impedance of a speaker as well.
Reactance is associated with coils (inductors) and changing voltages.
While you are correct that a resistive load is equivalent to impedance with a zero phase angle, impedance can go from purely resistive to purely capacitive to purely inductive, and how pure it is of either of these is the reason for the phase angle.
Speakers with passive crossover have a number of all of these three components. This is why the phase angle of your average 2-way speaker is complicated.
perhaps @carlsbad’s understanding is not incomplete, but i do agree with you that his description was... of course he was trying to keep it simple for our o-p
the reactivity of speaker loads in real world use playing music at practical volumes (not test tones, etc etc) is at the heart of why amplifier to speaker matching (and synergy) is such an important concept, and so central to building a well performing system
From a speaker perspective the spec is a rather complex chart of impedence vs frequency including the phase angle component, often called load. There is no single amplifier spec of an amplifiers ability to “ deal “ with the complex load w real music, so we end up using square waves ( made by using sine waves of many frequencies ), a simulated speaker load and then looking at power output and distortion at various loads. For a SS amp the accepted benchmark is ability to double power in watts as impedence is cut in half. This is also imperfect. Great amp designers are measure and listen people.
as a bit of an aside, my mentor , teacher and friend Richard Vandersteen engineers his speakers to be a relatively easy load and provides matching. power amplifiers optimized for those loads. An unfair advantage some would say…..
@carlsbadnice post on the simplified explanation, i had pegged you as a follower , i am sorry if i misjudged you.
@oldhvymec Time to hit the edit button. To reduce BY 1/10th is to reduce by 10% so reducing 100 by 1/10th leaves 90. To reduce TO 1/10th, in the case of 100, would leave you with 10, which is your tendered defintion of decimate.
funny you should mention your closeness with richard vandersteen
just now, this afternoon, i was goofing around in my listening room, i have a pair of maggies coming in soon, to try again, after all these years, so i shuffled my big spendors aside to prepare for their arrival, and just for giggles, i moved a set of vandy 3a sigs i have had in the back closet for many years now, into position for a listen, i already had the big pass labs integrated hooked up waiting for the maggies
it is soooo nice to hear richard’s lovely, now legendary speakers, so open, musical, details present but not forward, lovely vast soundstage, voices tall and life-size, full warm bass (not the fastest, but deep and easeful) - the pass int150 is just a touch forward, but warm with incredible bass drive and grip, and the combo is just terrific
these 3a-sigs are worth what, less than 2 grand a pair these days??? geez... lot's of aspiring hifi aficianadoes should back away from the newest hottest sexiest thing and just get a set of these... if i weren’t my crazy gear a holic self, i could easily live with these forever ... driven by the lovely pass... i am so happy i never sold these off
anyways, sorry to ramble and threadjack for a just moment, thought i would share that with you and the rest... 🙏
@jjss49;-) lovely..i will pass that story along as we chat weekly. I understand the “ speaker closet “, mine is full of Quad, A/D/S, , Etc… Then there are the out on loan.
IMO having run the 3a-sig w many amps in a few rooms over a decade, they require an amp w grip, drive and control due to the rear mounted acoustic coupler. Your amp is a perfect match :-) My brother a 40 year audiophile has my old pair, he uses a Threshold w ARC tube pre, SOTA table. The Threshold doesn’t care about the load, sounds sublime…. Nelson and Richard aint newbies…
I always thought resistance was what is measured as ohms. Impedance included capacitance and inductance. All three combined are considered reactance, and as so impede a signal. Hence the need for the phase angle information when matching equipment, mostly amps with speakers. My thinking is fostered by the need to understand for my own purposes.
@jjss49 loved the ramble. I once owned a pair of original model IIs. Think made in 1977, I bought used in 1985. Drove them with my B&K ST 140. Seems to me all his speakers have the strengths you describe. Maybe more dynamic with more resolution as one moves up the line.
@emergingsoul I assume you know the difference between direct current (dc) and alternating current (ac). DC current has a constant amplitude and will not change with time. Amplitude of the ac current will change with time or frequency. Your ac power outlet looks like a sinusoidal waveform with 60 Hz frequency.
Think of your music signal as a collection of ac currents with frequency between 20 - 20,000 Hz. Audio signals are NOT dc, that will be highly problematic. There are protection circuits to prevent any dc current getting into the amplifier and then the speaker.
Impedance Z = R + jLw +1/jCw where
R = Resistance, L = inductance, C = capacitance, w = frequency and j = Square root (-1)
for dc current w = 0
Then Impedance Z = infinity. Which implies that dc current will not pass through a capacitor. You may have heard of dc blocking capacitors and that is how it blocks dc current.
As I said earlier, for musical signals w>0
Hence Z is a function of w assuming R, L, and C are fixed values. In short impedance can be written as Z = A (Cos x + j Sin x) where A is the amplitude and x is the phase angle. Cosine and Sine are trigonometric functions. Value of Z will vary based on frequency and that is why there are two plots speaker impedance. One is the amplitude as a function of frequency and the other is the phase angle as a function of the frequency.
When w = square root (1/LC), then Z = R. This is a special frequency where phase angle = 0. This is the only frequency where impedance equal to resistance. Rest of the instances, they are not the same.
Impedance and resistance are not the same thing when considering audio signals as shown above with the one exception.
Any time. Reminds me of x-ray school physics. They teach all these mathematical formulas that almost everyone memorizes and learns by rote. Even the teachers, most of whom don’t really understand they just have learned the jargon and formulas. I don’t know why people put so much emphasis on arcane math when they could just as easily be teaching in a way everyone can readily understand.
Like impedance between source and amp, preamp and amp, whatever. Electrically the same as with speakers, at least in the sense of technical definitions. In terms of real world results however, very different.
With speakers we want to get a lot of work done, to move a lot of air. Moving air takes power and since high impedance increases resistance to power flow it is harder to get that work done and this is why for example the Tekton Moab is 4 ohms even though it could easily be 8 (and is an option) but sounds better at 4. In spite of what many will say looking at it from a purely amplifier distortion point of view while ignoring the the fact we need that power to do the work of moving air. Their misunderstanding blocks them from getting good sound.
With amplifiers it is a different story. With amps the input signal doesn’t need to move air, it just needs to maintain low distortion. Different story, different use of impedance. With the amp we want a very high impedance, so that it does NOT require a lot of current with even the most dynamic highest levels to drive the amp. This is why we see amplifier input impedance in the tens of thousands of ohms. A really high input impedance makes it easier for the preamp to "drive" the amp with low distortion. We can get away with this here because we aren’t "driving" the amp in the same sense as we are driving the speaker.
Even so, you will notice when people try and go direct from source to amp they invariably find better sound quality adding a preamp in between. Why? Because even though the power needed to maintain the current needed to drive a preamp or amp is very low, it is not zero. Source components typically are made with very weak output stages. This is why virtually everyone who goes from running direct to using a preamp reports a nice improvement in dynamics, bass and slam. These are the things that call for more current. The preamp has the current to drive the amp a lot better than the source alone does.
I am deliberately oversimplifying in order to make this all easily understandable. Because I have learned over the years it is far better to understand imperfectly but USEFULLY than to memorize a lot of arcane jargon without really understanding much at all.
Glad you found that helpful. Hope you find this helpful as well.
You have to be kidding me, a true squint's answer, I'm impressed, but still no answer for the OP. Like me talking the guy off a 40 foot telephone pole. "Jump, just try to hit the grass". Splat! Ops, wind changed by .21760943% X 21 -.33456. LOL
@erik_squiresI am a physicist. My understanding is pretty darn good. This is a simplified explanation for the layman. You seem to be struggling to execute that.
Better to struggle withe truth than be comforted by falsehoods.
"Impedance is resistance which changes with frequency whereas simple resistance is constant with frequency."
There is NO frequency with DC, which is WHY, "resistance is constant".
With ONLY a single strand of solid wire: passing an AC current (ie: with a frequency) through, will cause that wire’s effective cross-sectional area to be reduced, via skin effect*, thus: an increase in measured Ohms (knowledge regarding electricity that has been around since the late 1800s).
SIMPLY: the semantics applied by the scientific community to measuring electrical flow, as concerns those two types of current and their performance through conductors.
btw: DC = no waveform, while AC= sinusoidal
Perhaps some fail to understand that, in any sinusoidal waveform, VOLTAGE rises and falls, changing the math completely.
So far, I thought impedance meant the same as efficiency. That is why I chose 8 ohm speakers. Not sure why someone would purchase 4 ohm speakers because wouldn't that require a more powerful amplifier? So, why then do manufacturers make 4 ohm speakers? I didn't realize Tekton manufactures some of their speakers in both 4 ohm and 8 ohm.
I think Carbon Miller has a lot of knowledge.
I wish this forum could provide Zoom seminar so we could learn more from some of those who have a lot of knowledge to share. I think just knowing the basics could save us all a lot of money to avoid making some mistakes. Perhaps, Audiogon could think about providing Zoom seminars. This would really provide those like myself who don't have the knowledge a way to gain better understanding. Otherwise, I think a lot of us still do not have the sound they are looking for. Carbon Miller would be an excellent teacher along with others in this group. Perhaps provide Zoom meetings to allow us to see one another and to have discussions.
I still wonder why some speaker manufacturers design their speakers with a 4 ohm design as opposed to 8 ohm. Vienna Acoustics comes to mind. I also wonder why some manufacture their speakers with soft dome speakers vs Beryilium. I know soft dome tweeters sound less bright. When I listened to Vienna Acoustic speakers I noticed they sound nice for classical music. However, I thought they lacked the detail such a cymbals when listening to jazz.
In simple electronic models, a resistor is considered perfect as is a capacitor and an inductor. In practice, they all are flawed and have small elements of each other in their behaviour. For example a simple inductor can be a coil of wire, but obviously a length of wire has resistance.
Impedance is the real-world aspect of a circuit made up of resistors, inductors and capacitors. It accounts for e.g. voltage and current not being always in phase. In domestic audio, the measurement is encountered most reliably when describing loudspeakers with passive crossovers.
"There is NO frequency with DC, which is WHY, "resistance is constant".
The above is NOT true. You can still apply AC to simple resistance and its resistance will still NOT change, whereas a capacitor and/or an inductor’s resistance WILL change with AC.
Here is a table which shows how various components will respond to application of AC or DC voltage:
It seems many of these replies may be a bit more complicated than the OP is interested in. Both resistance and impedance are the opposition to current flow. Both are measured in ohms. The difference is resistance is a function of direct current electricity (DC) and impedance is for alternating current (AC). With audio components we are dealing with AC. For someone wishing to properly match components there are three main connections of concern: phono cartridge into phono pre-amp, system pre-amp into power amp and power amp into speaker. Ignoring the can of worms of cartridge loading, the input impedance of a power amp wants to be at least 10X the impedance of the pre-amp output for proper signal transfer. Most good pre-amps and amps easily meet this and so can, largely, be ignored. Speakers are another story. Yes, impedance does vary with frequency. In speaker measurements we see graphs of frequency vs. ohms. The speaker impedance will often vary from 4 to 20, or more, ohms. It is the lowest value we care about. Some power amps will have a hard time driving speakers that dip too far below 4 ohms because they cannot provide enough current and will get hot, distortion will rise and, in extreme cases, output transistors can be damaged. If you are considering speakers that get down to two ohms or less make sure the amp is capable of driving low impedances.
A final note of caution is if one is considering setting up two stereo amps in bridged mono for the increased power and reduced distortion, understand that a 4 ohm speaker looks like 2 ohms to an amp in mono and should only be done with speakers which do not go below 8 ohms.
The resistance is related to a DC circuit. The impedance is related to an AC circuit.When we talk about impedance we should consider capacitive and inductive elements in the circuit. Measuring the impedance of a speaker driver will show a difference between the DC value of the voice coil and measurements taken at different frequencies showing the behaviour of the inductive part of the coil in action and the capacitive part of the whole. The DC measurement is taken when, for exemple the speaker driver's cone doesn't move (static) while the AC measurement of impedance is taken with a sweep of frequencies (10 Hz to 10k Hz). A 8 ohms impedance woofer may have 6,5 ohms of DC resistance. I hope it helps to clarify the difference.
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