[RexAeterna]

sounds like a lesser pioneer model. the monitor 10's i use to have used a 57mm mylar cone driver for it's very light mass and stiffness. they were heavy headphones but the weight of them actually never bothered me for hours and hours of use. they sealed insanely well and blocked outside noise nicely and used them for movies when i had them. i say though they sounded insanely good and almost completely flat and very neutral to me. they had good powerful bass extension and good high frequency extension well and sounded also bright on lot of modern stuff. good clarity and impressive stereo separation for a closed headphone and sounded more like open headphones. they did lot more things right than most headphones out today labeled as ''audiophile'' or ''studio'' or ''reference'' headphones especially with the midrange.

mine was in very good condition with leather pads still in great shape and no rotted foam. they worked pretty well out of low output impedance sources but seemed a pain to get volume out of most of my receivers that worked tons better with my 600ohm headphones i have. they sounded really great off of speaker outputs though but just if volume too high there might be resonance issues with the enclosure even though its genuine leather so at low listening to moderate listening levels they sounded nice with no enclosure resonance issues. they overall did sound great. there is a pioneer monitor 10 II and monitor 10R i believe it's called but from what i seen and read they're not same level in sound like the older original pioneer monitor 10's.

even though i loved them i traded them off to try something else i was interested in. i miss them but i have no regrets, cause you live and you learn. way of life.

 

[palmfish]

They look newer than mine. Late 70's to early 80's would be my guess. Definitely higher quality.

 

[Chris J]

You are saying that the 2,000 ohm Senn HD424 and similar Senns are piezo-electric?
 
On a slightly different topic, subjectively they are very trebly and very bass light.  A bit harsh, too.
 
 

 

[RexAeterna]

You are saying that the 2,000 ohm Senn HD424 and similar Senns are piezo-electric?

On a slightly different topic, subjectively they are very trebly and very bass light.  A bit harsh, too.

no. the senns used a mic driver instead of your typical dome dynamic driver. it's another reason why their impedance was so high. they tried to use a mic driver to achieve a much flatter response. i was mentioning also that lot of piezoelectric headphones were very high impedance as well. i never heard the hd424 myself so i can't say how they sound. only thing maybe i can suggest to try maybe and might help with them is drive them directly off of speaker amp. lot of headphones during late 60's to early 70's used adapter boxes made by Koss to drive your headphones off the speaker outputs. easy way also is you can try using pre-outs via RCA to 1/4'' adapter on a preamp since they're meant to drive anything 600ohms and above just to try it out and see how it sounds then.

 

[Chris J]

A microphone transducer?
Very, very wierd.
 
Thanks for the ideas, Rex.
The Senn HD424 are more of a curiousity to me now. Thanks for the suggestions, but I have better 'phones
They basically sound "good" driven from:
 - A Matrix M Stage
 - A La Figaro 336C OTL tube amp
 - the headphone output of a Bryston 2B-LP
any of these will drive the phones to ear bleeding volume.
Can't say any of them make the HD424s sound amazing.   That's OK, they sounded fine in 1979 when my brother bought them.
 
I like to use them to prove one point:   this headphone amp can drive really high impedance 'phones with ease.
I know what you mean though, any pre-amp that's worth a damn will drive a 2,000 ohm load without breaking into a sweat.
 

 

[germanium]

Quote:

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.

It is not the power transformer that does the impedance matching in tube amps, it is the output transformer. For example my friends tube amp that he designed & built has tubes with an output impedance of 2100 ohms. The output transformer converts the high voltage high impedance tube to the lower voltage lower impedance speaker. When properly matched the output impedance without feedback matches that of the speakers impedance. Note that all tube amps that have output transformers do this & will closely match the output impedance of the tube to the speakers impedance when feedback is removed as this is where they get the best performance. Feedback lowers the output impedance that the speaker sees but the impedance match as far as the tubes are concerned is still maintained for best power transfer from the tubes to the speakers. Even with feedback if the impedance of the tube to speaker impedance is not matched distortion goes up & power goes down if it is a poor enough match.
 

 

[Chris J]

Quote:

When properly matched the output impedance without feedback matches that of the speakers impedance. Note that all tube amps that have output transformers do this & will closely match the output impedance of the tube to the speakers impedance when feedback is removed as this is where they get the best performance. Feedback lowers the output impedance that the speaker sees but the impedance match as far as the tubes are concerned is still maintained for best power transfer from the tubes to the speakers. Even with feedback if the impedance of the tube to speaker impedance is not matched distortion goes up & power goes down if it is a poor enough match.
 

You're not saying that the transformer output impedance = speaker impedance? Most efficient power transfer occurs when transformer output impedance is << speaker impedance.
You're not saying best performance occurs when feedback is removed? Feedback lowers distortion, increases bandwidth and output impedance.
 

 

[germanium]

Quote:

You're not saying that the transformer output impedance = speaker impedance? Most efficient power transfer occurs when transformer output impedance is << speaker impedance.
You're not saying best performance occurs when feedback is removed? Feedback lowers distortion, increases bandwidth and output impedance.
 

The second sentance is completely false when dealing with tubes. Why? Tubes are high impedance devices in general. There are very few tubes that can drive spealers directly & then only if run in paralell.

Feedback improves measured performance not nessessarily audio performance. You will get the best performance with most tube amps if the output impedance without feedback matches the load impedance. This is true whether you add feedback or not. You will get better measured performance with feedback if you match the impedances before adding feedback. Feedback lowers output impedance as the speaker sees it but the tubes still need the matching impedance before adding feedback to perform best as they see the load.
 

 

[Chris J]

Quote:

The second sentance is completely false when dealing with tubes. Why? Tubes are high impedance devices in general. There are very few tubes that can drive spealers directly & then only if run in paralell.

Feedback improves measured performance not nessessarily audio performance. You will get the best performance with most tube amps if the output impedance without feedback matches the load impedance. This is true whether you add feedback or not. You will get better measured performance with feedback if you match the impedances before adding feedback. Feedback lowers output impedance as the speaker sees it but the tubes still need the matching impedance before adding feedback to perform best as they see the load.
 

 
You have mis-read my second sentence.
Removing feedback does not remove the transformer.
I was not talking about removing the output transformer.
I agree, tubes work best when driving a high load impedance because they have a high output impedance, can output a lot of voltage but cannot output a lot of current.
I agree that in a vacuum tube power amp the output tubes normally drive the primary side of the output transformer which presents a high impedance load to the output tubes.
 
Feedback improves bandwidth (therefore reduces phase shift across the audio bandwidth), decreases distortion, and decreases output impedance (therefore increases damping factor). It can also improve transient response.  Doesn't that improve audio performance?  
 
But the secondary side of the transformer (the output of the transformer) almost always has a much lower output imedance than the speaker impedance.
This is to increase electrical efficiency of the amp, among other things. Transformers are only efficient when secondary impedance is much lower than load impedance.
You will normally get better measured performance too, i.e. higher damping factor.
There are a few SET amps and guitar amps out there where the output impedance is almost as high as the speaker impedance, but those are exceptions.
 
To say that an amp sounds better without feedback is a very subjective statement.
I think you must have a preference for very coloured tube power amps.  Which is fine, I enjoy the sound of a good tube amp as much as I enjoy the sound of a good solid state amp. 
 
 

 

[germanium]

Quote:

 
You have mis-read my second sentence.
Removing feedback does not remove the transformer.
I was not talking about removing the output transformer.
I agree, tubes work best when driving a high load impedance because they have a high output impedance, can output a lot of voltage but cannot output a lot of current.
I agree that in a vacuum tube power amp the output tubes normally drive the primary side of the output transformer which presents a high impedance load to the output tubes.
 
Feedback improves bandwidth (therefore reduces phase shift across the audio bandwidth), decreases distortion, and decreases output impedance (therefore increases damping factor). It can also improve transient response.  Doesn't that improve audio performance?  
 
But the secondary side of the transformer (the output of the transformer) almost always has a much lower output imedance than the speaker impedance.
This is to increase electrical efficiency of the amp, among other things. Transformers are only efficient when secondary impedance is much lower than load impedance.
You will normally get better measured performance too, i.e. higher damping factor.
There are a few SET amps and guitar amps out there where the output impedance is almost as high as the speaker impedance, but those are exceptions.
 
To say that an amp sounds better without feedback is a very subjective statement.
I think you must have a preference for very coloured tube power amps.  Which is fine, I enjoy the sound of a good tube amp as much as I enjoy the sound of a good solid state amp. 
 
 

You are severely misreading my statements. I'm not talking of removing the output transformer only of using or not using feedback. Feedback can be used to make a bad amp look good but won't nessessarily make it sound better. Adding feedback to a properly designed tube amp will only improve specs & possibly sound in some situations. other situations specs will improve but sound will not. Many of the specs really do not correlate well with sound & hense are suspect means of addressing amp quality.
 

 

[Chris J]

I thought this was my second sentence:
Quote:

Most efficient power transfer occurs when transformer output impedance is << speaker impedance.
 

????? I'm Confused ???
 
Or were you referring to this statement?
 
"You're not saying best performance occurs when feedback is removed? Feedback lowers distortion, increases bandwidth and output impedance."??
 
If you disagree, then that is your opinion. Fair enough. You like what you like. I can't argue with your taste.
 
But very few tube amps are actually designed to run without feedback.
I'm sure that we both agree, tube amps with feedback almost always use less feedback than solid state amps.
 

 

[germanium]

Actually most tube amps can easily be run without feedback & sound great doing so whether they were originaly designed that way or not. Most transister amps though cannot be run without feedback & even if you could most would sound terrible. One exeption would be Pass Labs Aleph amp. This is a transistor amp designed to work without feedback, It is run pure class A1 & as a result run very very hot in spite of it's huge heatsink.

 

[RexAeterna]

lot of solid-state can run with minimum to none negative feedback and sound great . lot of older Harman Kardon power amps use the limited to no feedback approach and believed in ultra-wide bandwidth and TIM/IIM distortion was more audible compared to THD and they're considered very accurate and clean sounding amps that fellowed Dr Matti Otala designs in the past. i don't know if Harman Kardon in their newer power amps/receivers/integrated fellow the same design or not. i just know that Dr Matti Otala was one of the most respected in amplifier designing and believed in no negative feedback.

 

[xnor]

Quote:

[..] and believed in no negative feedback.

That's the problem right there.
 

 

[RexAeterna]

That's the problem right there.

yes, you are right. i was gonna ask why at first but then i read up on it for a bit. i spoke too soon on my part. so what i really meant Dr Matti Otala believed in ''minimum'' negative feedback,but was also more focused on T.I.M and I.I.M distortion than THD cause he believed that T.I.M and I.I.M was up to 10x more audible to the human ear than THD and was one of the more important aspects of an amplifier's output stages. i don't know much, but that is what i read so far, so it's my fault on my part earlier. i also forgot to tell every here happy easter and hope you guys are enjoying yourselves.