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10-07-06
Impedence curves of amps is not usually part of the spec's. ... Newbee
10-08-06: Bob_reynolds
I believe you can model the output impedance of an amplifier as an impedance in series with the impedance of the speaker cable and the impedance of the speaker. Thus, Z(total) = Z(amp) + Z(cable) + Z(speaker).
Within their design limits amplifiers are voltage sources, i.e., they will hold the voltage constant. So for a given output voltage the current drawn will be I = V / Z(total).
For Z(amp) << 1 ohm, Z(total) will be determined primarily by Z(speaker) and the voltage drop across R(amp) will be small. Thus, most of the output voltage reaches the speaker. This is the case for typical solid state designs.
For Z(amp) > 1 ohm, Z(total) will not be independent of Z(amp) and the voltage drop across R(amp) will not be negligible. Thus, a smaller fraction of the output voltage will be available to the speaker. This is the case for typical tube designs.
Z(amp) typically increases with frequency. Then for a nominal 8 ohm speaker load, a low Z(amp) will yield a relatively flat frequency response and a high Z(amp) will yield a rolled off high frequency response.
Z(speaker) is also determined by frequency. So, if Z(speaker) is relatively high across the audio band, then a Z(amp) of higher value could be tolerated and still yield a flat frequency response. On the other hand, if Z(speaker) is relatively low across the audio band, then a Z(amp) of low value would be required to yield a flat frequency response.
That's my reasoning. It may be completely wrong.
Bob_reynolds (Threads | Answers | This Thread)
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
Sean & dave, thanks for talking this discussion even furthe ... Shadorne
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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