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Damping factor. Why it is not always as important as some make it out to be. - Page 5

post #61 of 128
Quote:
Originally Posted by Chris J View Post

 

 

If you did then you would see that impedadance matching does not normally apply to audiohile loudspeakers.

 

 



So long as the amp is worth its salt.


Edited by Mauricio - 3/14/12 at 4:40am
post #62 of 128
the power transformer? duh. the power transformer takes care of matching the impedance...actually more likely the voltage to that specific impedance. the power transformer will take care of all the voltage fluctuations that occurs through out the frequency range on a well design amp and well design power transformer. that's the only reason why they're used in audio equipment(besides blocking EMI and RFI and preventing DC getting inside the amp and destroying the components).


it's more about voltage matching then impedance matching. this was practiced when solid state was first popularized for not only the consumer market but professional market cause it was way to costly and tests showed impedance matching is not important with audio equipment as long as the amp has a low enough output impedance it will allow perfect power transfer across the complete frequency range of the speaker. impedance matching is only still done in power lines and phone lines and still fellow the whole ''600ohm'' standard. the 600ohm standard does not imply for audio equipment. that's why voltage matching is more important with audio equipment. as long as the amp has a high enough input impedance it will have no issues dropping down enough voltage across the mulitple sources plugged into it with maximum power transfer.

impedance matching with audio gear is just bunch of marketing. it's only important with some tube equipment when it comes to matching the power transformer with the right tubes. once that it done correctly the power transformer if implanted correctly and perfectly matched with the tubes then it will be the transformers job to do all the impedance matching for it but int reality all it's doing is matching the specific voltages for that specific impedance spike.
post #63 of 128
Quote:
Originally Posted by RexAeterna View Post

the power transformer? duh. the power transformer takes care of matching the impedance...actually more likely the voltage to that specific impedance. the power transformer will take care of all the voltage fluctuations that occurs through out the frequency range on a well design amp and well design power transformer. that's the only reason why they're used in audio equipment(besides blocking EMI and RFI and preventing DC getting inside the amp and destroying the components).
it's more about voltage matching then impedance matching. this was practiced when solid state was first popularized for not only the consumer market but professional market cause it was way to costly and tests showed impedance matching is not important with audio equipment as long as the amp has a low enough output impedance it will allow perfect power transfer across the complete frequency range of the speaker. impedance matching is only still done in power lines and phone lines and still fellow the whole ''600ohm'' standard. the 600ohm standard does not imply for audio equipment. that's why voltage matching is more important with audio equipment. as long as the amp has a high enough input impedance it will have no issues dropping down enough voltage across the mulitple sources plugged into it with maximum power transfer.
impedance matching with audio gear is just bunch of marketing. it's only important with some tube equipment when it comes to matching the power transformer with the right tubes. once that it done correctly the power transformer if implanted correctly and perfectly matched with the tubes then it will be the transformers job to do all the impedance matching for it but int reality all it's doing is matching the specific voltages for that specific impedance spike.


The Power Transformer:
If by "power transformer", you mean power supply transformer, then the primary purpose of the power transformer in an audio amplifier is to step the Line Voltage (i.e. the voltage at the wall receptacle, 120 Vac in North America) down from 120 Vac to the voltage required for the amplifier power supply.  In a power amp this may be approx. 50 Vac, higher or lower depending on the maximum output of the power amp.  The amplifier power supply then converts this AC voltage into DC for the amplifier.

The power transformer does not take care of voltage fluctuations throughout the audio bandwidth.

 

Impedance matching:

Impedance matching has no relevance on low frequency stuff like audio. The wavelengths are far too long. By low frequency I mean analogue signals below 1 MHz.

Impedance matching is not used in power lines. The important thing in powerlines is keeping power losses down, i.e. keeping efficiency high. This is normally done by using high voltage transmission (27,000 Volts and higher), keeping line losses down and using transformers with a low output impedance.

 

Voltage Matching:

Virtually all Audio Power Amplifiers are actually Voltage sources. The input is voltage and the output is voltage. The "gain" that we are normally adjusting on an amp is voltage gain.

The idea is to apply the voltage across the loudspeaker as accurately as possible. One of the ways to do this is to keep the output impedance of the power amp as low as possible throughout the audio bandwidth.

It's not about maximum powe transfer, it's all about efficient and accurate power transfer.

 

Output Transformer:

In a vacuum tube stereo power amplifier there are normally three transformers: one power supply transformer and two output transformers.  The output transformers are matched to the tube characteristics and are used to reduce the output impedance of the output tubes. 

A transistor amplifier normally will only have one power transformer and does not require output transformers as the output transistors have a sufficiently low output impedance.

post #64 of 128

Two separate issues here:

  • One is the impedance matching for high frequency (much higher than audio) signals due to transmission line effects.  This is due to the fact that at very high frequencies signals start to behave as if they are waves rather than particles.
  • The other is the impedance matching so that the amplifier output resistance is much lower than the load's so that the amp's power is not wasted on its own output stage.
post #65 of 128
Quote:
Originally Posted by Mauricio View Post

Two separate issues here:

  • One is the impedance matching for high frequency (much higher than audio) signals due to transmission line effects.  This is due to the fact that at very high frequencies signals start to behave as if they are waves rather than particles.
  • The other is the impedance matching so that the amplifier output resistance is much lower than the load's so that the amp's power is not wasted on its own output stage.

 

Basically true, but:
The first issue is called impedance matching.

The second issue is not called impedance matching, it is more properly called impedance bridging. It is maximizing voltage transfer to the load.

When you maximize voltage transfer from a voltage source to the load, then you are optimizing electrical efficiency, increasing damping factor and reducing frequency variations between source and load from the variations in the load impedance. 
 

 

post #66 of 128

I recently picked up a pair of old Pioneer SE-30a headphones at a yard sale. There is a badge on the side of the cups that boldly advertises 8 ohms.

 

They sound good (good being a relative term compared to modern headphones) when plugged into my more "period-correct" integrated amp and receiver. When I plugged them into my Objective2, they sounded horrible.

 

I assumed that it was an impedance issue, but now I'm not sure. I'm on the fringes of understanding some of the concepts discussed here, but I found this experience interesting so I thought I'd bring it up.

 

FWIW, I have some headphones that sound much better sourced by the O2, and some headphones that sound the same out of both.

 

Is damping factor at play here or is it something else?

post #67 of 128
Quote:
Originally Posted by palmfish View Post

I recently picked up a pair of old Pioneer SE-30a headphones at a yard sale. There is a badge on the side of the cups that boldly advertises 8 ohms.

 

They sound good (good being a relative term compared to modern headphones) when plugged into my more "period-correct" integrated amp and receiver. When I plugged them into my Objective2, they sounded horrible.

 

I assumed that it was an impedance issue, but now I'm not sure. I'm on the fringes of understanding some of the concepts discussed here, but I found this experience interesting so I thought I'd bring it up.

 

FWIW, I have some headphones that sound much better sourced by the O2, and some headphones that sound the same out of both.

 

Is damping factor at play here or is it something else?


 

Yes, this is an impedance issue.

I assume you are hearing distortion?
If they really are 8 ohm headphones then they pulling way too much current out of the O2, there are very few Headphone Amplifiers designed to drive an 8 ohm load.

 

I did some calculations, a receiver headphone jack should have enough voltage and current to drive 8 ohm headphones, but the O2 will not.

 

I'm not surprised that some headphones sound better out of the O2.

The O2 has a very low output impedance, some headphones need this damping factor, some do not.

The O2 was designed to drive almost any modern headphone with an impedance between 32 and 600 ohms.

 

 

post #68 of 128
Quote:
Originally Posted by Chris J View Post


 

Yes, this is an impedance issue.

I assume you are hearing distortion?
If they really are 8 ohm headphones then they pulling way too much current out of the O2, there are very few Headphone Amplifiers designed to drive an 8 ohm load.

 

I did some calculations, a receiver headphone jack should have enough voltage and current to drive 8 ohm headphones, but the O2 will not.

 

I'm not surprised that some headphones sound better out of the O2.

The O2 has a very low output impedance, some headphones need this damping factor, some do not.

The O2 was designed to drive almost any modern headphone with an impedance between 32 and 600 ohms.

 

 



I don't hear distortion with the Pioneers, they just sound sound dull and lifeless through the O2. But what you said does make sense to me (from the little that I know).

 

My Denon AH-D7000's are rated at 25 ohms and they sound the same through every amp and portable device I've tried. I can only assume that their flat impedance curve keeps frequency response relatively flat and their driver design is such that electrical damping isn't needed (heavy magnet, physical damping, etc?).

post #69 of 128
Quote:
Originally Posted by palmfish View Post



I don't hear distortion with the Pioneers, they just sound sound dull and lifeless through the O2. But what you said does make sense to me (from the little that I know).

 

My Denon AH-D7000's are rated at 25 ohms and they sound the same through every amp and portable device I've tried. I can only assume that their flat impedance curve keeps frequency response relatively flat and their driver design is such that electrical damping isn't needed (heavy magnet, physical damping, etc?).



Dull and lifeless also makes sense.  That's what I have heard when I tried to drive a pair of large 4 ohm Infinity speakers with a very small 2 Watt amp many years ago! The amp was not designed to drive 4 ohm loads.

 

Your assessment of the Denon AH-D7000 makes sense to me.

The beauty of the O2 is you can forget all that stuff (damping, frequency variation) and be confident that the O2 will drive almost any 'phone you may buy in the future, unless the 'phone is ultra power hungry or ultra low impedance.

 

I've never even heard of an 8 ohm headphone.

What can I say?  I have a pair of 2,000 ohm headphones! Probably same vintage as your Pioneers.

 

post #70 of 128
Quote:

Originally Posted by Chris J View Post

 

I've never even heard of an 8 ohm headphone.

 



Wow, I've never heard of 2kOhm headphones.

 

Don't worry though, you're not missing much - these 8 ohm phones are not particularly impressive sounding.

 

Although they do look cool though - in a Kubrick sci-fi sort of way...

 

IMG_0903.JPG

 

IMG_0902.JPG

 

IMG_0905.JPG

post #71 of 128
Quote:
Originally Posted by palmfish View Post

Wow, I've never heard of 2kOhm headphones.

 

Don't worry though, you're not missing much - these 8 ohm phones are not particularly impressive sounding.

 

Although they do look cool though - in a Kubrick sci-fi sort of way...
 

 

They look like something out of Dr. Strangelove!

 

The 2,000 ohm 'phones are Sennheiser HD424, vintage 1980.

post #72 of 128

I was thinking 2001 Space Odyssey or Clockwork Orange, but Dr. Strangelove works too.  wink.gif

 

My dad had a pair of HD 430's of about the same vintage, I think. I had no idea they were so high impedance.

 

Designed for the high output impedance headphone jacks of the period?


Edited by palmfish - 3/22/12 at 7:55pm
post #73 of 128
Quote:
Originally Posted by Chris J View Post

I've never even heard of an 8 ohm headphone.
What can I say?  I have a pair of 2,000 ohm headphones! Probably same vintage as your Pioneers.

lot of vintage headphones especially just random packaged ones for consumer system stacks were between 4-16ohms and most of them were just left over paper cone tweeters or midrange drivers thrown into a random enclosure with no mechanical damping whatsoever and just had a driver too large for the plastic enclosure giving most vintage headphones the well known ''boxy'' sound associated with vintage headphones. most of them worked great off of speaker outputs since most had a very low sensitivity and being a speaker driver it handle it well with no background noise issues from high gain issues.

i had pair of pioneer monitor 10's once in near perfect condition and fully functional. was rated at 4-16ohms but did not respond well out most receiver or amps jacks and need to turn the dial up past 12 o' clock to get reasonable volume out of them. the manual claimed 100db sensitive and not recommended for speaker output use but i though it was just b/s cause i knew these headphones could use some extra juice. made an adapter, hooked it up to some speaker outputs of a receiver and vola it sounded better and far more headroom on the gain but some amps i had to use the -20db muting switch cause gain was too high but they sounded great.

for your headphones it's probably cause the pioneers you had used a piezoelectric driver. piezoelectric drivers are usually always reccomended for speaker output use. only other headphone had that kind of impedance was pair of sennheiser hd414 and 424 i believe on the older models and changed to 600ohm models. reason why cause those headphones use dynamic mic drivers instead of your typical dome headphone driver to try to achieve a perfect flat response. they were very unique headphones by sennheiser indeed.
post #74 of 128
Quote:
Originally Posted by palmfish View Post

I was thinking 2001 Space Odyssey or Clockwork Orange, but Dr. Strangelove works too.  wink.gif

My dad had a pair of HD 430's of about the same vintage, I think. I had no idea they were so high impedance.

Designed for the high output impedance headphone jacks of the period?

most headphones then fellowed the ''600ohm standard'' in studio and professional use, so lot of well design headphones were made with a 600ohm or higher impedance to be used of high impedance gear. only odd ball at the time was the pioneer monitor 10's for studio and live field use. it had a 4-16 ohm rating but using aluminum voice coils gave it some extra resistance for extra power handling since it had a 700mw power handling and of course cause aluminum is much more resistive.

also i almost forgot too.... beyer had some 600 ohm dt48 models but are pretty rare and were mainly around 4 or 8ohms. they used pressed aluminum voice coils as well so they do like decent amount of torque like the monitor 10's.
post #75 of 128

Very interesting Rex, thanks for the info.

 

The drivers in these Pioneers are big paper cones - maybe almost 3". They look like something out of an old television or clock radio. I bought them just for the novelty (I love vintage gear) and out of curiosity. I'll probably never listen to them since they are sorely outclassed by even a $25 pair of Koss UR55's I keep near my computer.


Edited by palmfish - 3/30/12 at 5:54am
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