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  Please explain amplifier output impedance
I have recently read a few loudspeaker reviews which mention that the speakers would likely work best with low output impedance (or high output impedance) amplifiers.

So, what measurement defines low output impedance (or high output impedance) on an amplifier? What's the numerical value of low and high output impedance, and what is "average"?

Also, what specification of a loudspeaker provides info that would indicate using an amplifier with particular output impedance?

Thanks in advance for explaining this in laymen’s terms. :)
Tvad  (Threads | Answers | This Thread)

10-07-06
  Responses (1-72 of 72)
Click title to read one, or click date to read all below it.

10-07-06   Impedence curves of amps is not usually part of the spec's. ...   Newbee

10-08-06   I believe you can model the output impedance of an amplifier ...   Bob_reynolds

10-08-06   I'm not an expert on the subject but always heard that solid ...   Bobgates

10-08-06   Output impedance is defined by the amplifiers damping factor ...   Shadorne

10-08-06   I agree with most of what newbee said. output impedance and ...   Honest1

10-08-06   a solid state amp can put out more power into a 4 ohm speake ...   Audiofeil

10-08-06   Bob's explanation is a more accurate one than mine. the poin ...   Shadorne

10-08-06   Thanks for all the replies. tube amps are notorious fo ...   Tvad

10-08-06   The idea behind having a low output impedance is that the am ...   Bob_reynolds

10-08-06   I have spent most of the past few months designing a couple ...   Audiokinesis

10-08-06   Bob and duke, thanks for your great replies. very helpful. ...   Tvad

10-08-06   Duke, are you suggesting that amplifier impedence has a cont ...   Newbee

10-08-06   Hi tvad, sorry i completely overlooked your basic question. ...   Audiokinesis

10-08-06   Newbee, i don't really know what amplifier output impedanc ...   Audiokinesis

10-08-06   Thanks again duke, that helps. i have noticed the variable ...   Tvad

10-08-06   Duke, no i don't and i don't have the means to measure it. ...   Newbee

10-08-06   Tvad, i think the 10x rule of thumb for impedance matching b ...   Bob_reynolds

10-08-06   Tvad, if you accept solid state amplifier technology and yo ...   Shadorne

10-09-06   Damping factor has less effect on a speaker than most might ...   Atmasphere

10-09-06   Atmasphere, "voltage cannot be produced in the absence ...   Bob_reynolds

10-09-06   negative feedback just ensures linearity - it makes sure th ...   Shadorne

10-09-06   Negative feedback in high levels is quite audible and it doe ...   Sean

10-10-06   Sean's post above is right on but i would like to add a coup ...   Aball

10-10-06   agreed. a badly designed circuit will sound terrible. most ...   Shadorne

10-10-06   Arthur: those are very good points and well worth clarifying ...   Sean

10-10-06   To bring this discussion back around to my original question ...   Tvad

10-10-06   There is no hard and fast threshold but imo, anything over 1 ...   Aball

10-10-06   High damping factor is allways desirable. since speakers are ...   Seurat

10-10-06   Yes, it is impossible to make voltage without current. power ...   Atmasphere

10-10-06   i believe it is this issue that dakiom feedback stabilizers ...   Tvad

10-10-06   I've specifically mentioned the td ( time delay ) of a circu ...   Sean

10-11-06   I'm friends with a physicist who specializes in audio, and a ...   Audiokinesis

10-10-06   i humbly beg to disagree. done properly, negative feedback ...   Shadorne

10-11-06   Atmasphere, not to belabor the point or insult you, but to b ...   Bob_reynolds

10-11-06   Hi bob, in the case you mention, no work would be done. iow ...   Atmasphere

10-11-06   i assume you are refering to intermodulation distortion or ...   Shadorne

10-11-06   Hi shadorne, if you look at the quote you will see that it i ...   Atmasphere

10-11-06   This is one of the reasons why i strive to build gobs of dyn ...   Sean

10-12-06   tvad: "to bring this discussion back around to my ori ...   Benie

10-12-06   Benie, my question was not about low impedance speakers.   Tvad

10-12-06   Atmasphere, interesting. perceived loudness clearly can be ...   Shadorne

10-12-06   Shadorne- yes. this is a major reason why tubes continue to ...   Atmasphere

10-12-06   Tvad: there isn't a specific point where an amp is either co ...   Sean

10-12-06   in your view, what measurement is considered to be a lower o ...   Tvad

10-13-06   Tvad: the speakers that came to mind right away were the coi ...   Sean

10-13-06   Thanks for that, sean.   Tvad

10-13-06   Sean, i recently spent several weeks designing two loudspeak ...   Audiokinesis

10-13-06   Duke notes:indeed it is! how did you go about it --if i'm no ...   Gregm

10-13-06   Duke: i don't need to tell you or anyone else that has truly ...   Sean

10-13-06   much earlier in this thread i suggested 80 as an "idea ...   Shadorne

10-13-06   Success! and in only six days... :)   Tvad

10-13-06   Success? i would consider damping over 20:1 to be excessive. ...   Atmasphere

10-13-06   No success? oh well. i've learned a lot. you guys have fun ...   Tvad

10-13-06   Hi gregm, no problem, that's a fair question. i won't give ...   Audiokinesis

10-13-06   Success. i think we all agree if you accept that my persepct ...   Shadorne

10-13-06   I have been following this thread with interest and doing my ...   Tboooe

10-13-06   not to necessarily critique tboooe's comment, but it prompte ...   Tvad

10-14-06   Tvad: unfortunately, there is no "big dummy's guide to ...   Sean

10-14-06   Sean, well said!   Unsound

10-14-06   There is no universal correct amplifier output impedance. th ...   david@

10-15-06   It should be noted that mr berning is a manufacturer of audi ...   Sean

10-15-06   One more thing. sometimes i'm simply debating something bas ...   Sean

10-15-06   Well let's see how long this thread lasts. i'm betting on la ...   Audiofeil

10-15-06   if so, it'll be too bad. this thread has more useful discuss ...   Tvad

10-15-06: Shadorne
Sean & Dave,

Thanks for talking this discussion even further.

There are quite different design philosophies behind the conflicting views on output impedance;

One philosophy is that the amplifier and cables should have a minimum affect on the speaker response - i.e. the speaker is designed for SS amps of many types and the speaker impedance variation with frequency is NOT intended to affect system frequency response. (provided the amp has enough power to drive the load this philosophy leads to consistent results => the flat speaker response will be maintained provided it is coupled with a low output impedance SS amp.)

The other philosophy is that amplifier and cables should be chosen in order to augment/adjust speaker response by behaving as a kind of "equalizer" or a tuned system; in this case, system response will vary as a function of speaker impedance. (amp ouput impedance - cable - speaker load act together as a filter/equalizer on the sound => this leads to a system which can be tuned to taste, according to the preferences of the user and the selected high output impedance amp)

It is the differing philosophy that leads to different views on amplifier output impedance. There are advantages to both. One is consistent and accurate; but you get what you get. The other approach offers greater flexibility for tweaking to taste.

This is why I qualified my earlier comments in this thread by saying they were generalizations for SS amps an not for tubes. Tubes seem to be desirable to those that like a certain flavor to the sound...a certain warmth or punch to the bass. (and there is nothing wrong with that. Doug Sax, one of the industry leading professional Mastering Engineers, uses tubes for mastering for this very reason. Indeed, most people seem to prefer an equalization curve with a boosted bass and a rolled off treble.

Shadorne  (System | Reviews | Threads | Answers | This Thread)


10-15-06   Apparently my point was missed about the subject of speaker ...   david@

10-15-06   By the way, sean, what would think of an amplifier with nega ...   david@

10-16-06   Thank you, duke. indeed, although rather benign compared to ...   Gregm

10-16-06   i agree that damping is well studied in engineering, howeve ...   Shadorne

10-16-06   Hi sean, i can't think of an amplifier that that qualifies a ...   Atmasphere

10-19-06   David@davidberning.com: i understand that electrical damping ...   Sean

10-24-06   No worries sean! i agree with much of your comments regardin ...   Atmasphere


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