kwkarth, Neruda!

[Val]

To my ears, the AKG graph is right on the money, except they perhaps don't sound that much bass-shy to me. They do sound a bit distant or recessed, just what the droop between 2kHz and 5kHz causes, and a bit, a wee bit silvery due to the small peak at 6kHz.

 

[Xander]

Quote:

Originally posted by Val To my ears, the AKG graph is right on the money, except they perhaps don't sound that much bass-shy to me. They do sound a bit distant or recessed, just what the droop between 2kHz and 5kHz causes, and a bit, a wee bit silvery due to the small peak at 6kHz.

I agree. The uppermids are a bit recessed, and there are a few peaks.

 

[setmenu]

This thread seems full of knowledgable people.
I was wondering regarding these response graphs etc how much
is to do with the enclosure design or the transducer characteristics themselves.
I am at present experimenting with transducer design[planar coil
ribbons] and will shortly be getting some diaphrams etched
and am going to be very curious about their response curves!!!![the complete transducer that is]
I would be very interested in various wire guage/turns/coil diameter specs of different transducers[Probably not really particularly relevent to my design but interesting nonetheless.]

Sorry if this is off the thread topic

 

[Xander]

Quote:

Originally posted by setmenu This thread seems full of knowledgable people. I was wondering regarding these response graphs etc how much is to do with the enclosure design or the transducer characteristics themselves. I am at present experimenting with transducer design[planar coil ribbons] and will shortly be getting some diaphrams etched and am going to be very curious about their response curves!!!![the complete transducer that is] I would be very interested in various wire guage/turns/coil diameter specs of different transducers[Probably not really particularly relevent to my design but interesting nonetheless.] Sorry if this is off the thread topic

A lot. The frequency response itself is changed a lot by the enclosure, mostly by the earpad so I've found. The enclosure plays a large part in sealed cans, however in open ones I don't think it has a huge ammount to do with how the can sounds. I could be wrong, though. So take that with a huge grain of salt.

The impedance magnitude graph, shows what the impedance is of the phone while responding to a specific frequency. Very little headphones are perfect, so at 40hz the impedance may be a bit higher then at 10khz and so on.

The driver itself and all of its components, especially the diaphragm, is the most important factor in defining the frequency response, the impedance curve having more to do with the voice coil itself. In a sealed enclosure on the other hand, more resistive energy towards the driver itself can cause the impedance for any given frequency to rise or fall in magnitude.

EDIT:

Everything in this post is complete hogwash.

I'm going to learn why in a minute.

 

[Xander]

I was quite wrong in my previous post, kwkarth corrected me and taught me quite a few things on the subject. I've asked his permission to post the private message here so that anyone reading this post would have the correct information, and not be misinformed by my post.

re:

quote:
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The impedance magnitude graph, shows what the impedance is of the phone while responding to a specific frequency. Very little headphones are perfect, so at 40hz the impedance may be a bit higher then at 10khz and so on.
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All transducers have one or more resonant frequencies. It is at these resonant points, because the transducer's acoustic impedance changes (from the resonant energy and it's effect on back-emf) that the electrical impedance is altered as well. Occasionally, in a multi-driver system, you'll see impedance irregularities caused by electrical resonance in the R/C crossovers circuits. It is the mark of a good design to locate these resonances outside the audible frequency range, or to otherwise minimize their magnitude.


quote:
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The driver itself and all of its components, especially the diaphragm, is the most important factor in defining the frequency response.[
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Where did you get this idea? You can look at a headphone or speaker design as a "system." All the components of that "system" affect the final quality of the result. You could have a great diaphragm design, but if the centering/locating spider, or the voice coil, or the vc former, or the magnet structure, or the diaphragm suspension, or the enclosure, or the wiring, or the voicing/crossovers were of poor design for any number of reasons, their "poorness" would obviate any "goodness" in the design of the diaphragm.


quote:
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the impedance curve having more to do with the voice coil itself. In a sealed enclosure on the other hand, more resistive energy towards the driver itself can cause the impedance for any given frequency to rise or fall in magnitude.
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The impedance "curve" has very little to do with the voice coil itself, as mentioned earlier. The bumps in the impedance are the result of the electromechanical phenomena. (system resonance producing varing degrees of back emf) So it is the entire system comprised of diaphragm and voice coil mass and stiffness, coupled wth the syspension compliance of the centering spider, diaphragm surround, and damping from acoustic loading coupled with damping from amp output impedance interacting with magnetic field that the voice coil is immersed in all together creating moments of inertia and system resonances from mass/compliance interaction.
The fundamental impedance is "set" by the voice coil, but cannot really be decoupled from the rest of the "system" at work here.

 

[Neruda]

man, kwkarth is a veritable fountain of knowledge, is he not?

But we're still arguing over whether or not line arrays increase efficiency!

 

[Xander]

Quote:

Originally posted by Neruda man, kwkarth is a veritable fountain of knowledge, is he not? But we're still arguing over whether or not line arrays increase efficiency!

Yes. And I'm a veritable LEARNING machine. He has absolutely no idea what he's gotten himself in to. This is definatly not a good mix.

 

[Tomcat]

"All transducers have one or more resonant frequencies. It is at these resonant points, because the transducer's acoustic impedance changes (from the resonant energy and it's effect on back-emf) that the electrical impedance is altered as well.
[...]
It is the mark of a good design to locate these resonances outside the audible frequency range, or to otherwise minimize their magnitude."

kwkarth,
now that you have been dragged into this, let's compare some more impedance curves:

kwkarth,
would you say that there is a certain sonic behaviour attributable to a certain impedance curve? Would you say that there are sonic effects from a large impedance hump even when the phone is driven by an extremely stable amp? What does it all mean?

 

[kwkarth]

Quote:

kwkarth, would you say that there is a certain sonic behaviour attributable to a certain impedance curve? Would you say that there are sonic effects from a large impedance hump even when the phone is driven by an extremely stable amp? What does it all mean?

Good questions. In almost all cases, there will be sonic attributes that correlate with measurable impedance bumps that fall within the audible spectrum, but they are greatly ameliorated by high damping factors of the driving amplifier. That's why the HD-600's will tend to sound bloated with a wimpy amp that does not "take control." They sound much more civil when driven by something like the Max that takes charge of the situation. (pun intended)

Even when driven by a very low impedance source, mechanical resonance is never a good thing under any circumstances in an audio system.

Resonance is only desirable in sounding boards of acoustical instruments.

Actually, bass reflex and other ported speaker designs like Bose's acoustic wave guide take advantage of resonance to acentuate certain frequencies. How do they typically sound to your ears?

 

[Tomcat]

Hmm, the 770 Pros are a bass reflex design. Doesn't seem to hurt their impedance behavior, though. Quite the contrary, together with the DT 250-250, they seem to have the most linear impedance curve of all the higher end Beyer phones. However, I am convinced that no single measurement will tell us all there is to know about the sonic merits or flaws of a component. I guess impedance curves tell us something about how easy it might be to take the path of the triode, for the path of the triode is the path to enlightenment.

I have always felt if an amp is built to exhibit the ultimate power and control, that's it's likely that something else has to give, as simplicity of the circuit or shortness of the signal path - and, in the end, some musicality.

What I find rather puzzling is the fact the only nastiness in the K 501's impedance curve occurs in the highest treble regions. But most people claim that the K 501 profit from a high power amp like no other phone, especially in their bass response. I guess we still have more questions than answers.

 

[kwkarth]

I know that Beyer says the 770’s are a “bass reflex” design, but that’s not really possible in the strictest sense with headphones, that aside, whether they are or aren’t, does not necessarily say anything about their impedance curve. You are absolutely correct in that no single measurement tells us all there is to know about how something sounds, heck all the measurements we know about still don’t tell the whole story, but they do paint a reasonable picture. I won’t mess with the triode issue...

The 501’s are difficult to drive simply because they’re inefficient. By observation, they are heavily damped mechanically in the low end and relatively undamped in the high end, and having an amp powerful enough to overcome the stiffness of the diaphragm surround compliance is part of what makes them inefficient. Always more questions than answers!! Else we wouldn’t be asking the right questions!!
Cheers