Headphone Impedance: Dont understand the differences
Mar 26, 2002 at 5:35 AM Thread Starter Post #1 of 33

gloco

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For someone who has so many posts, i feel like a schmuck.

Why are some cans high impedance (ohmage) while others are low? After reading that some of the more expensive cans are low impedance (like the W2002, the HP1000), then why are the Sennheisers high impedance? In other words, would Sennheiser and AKG be able to create low impedance versions of the HD600 and 501 and maintain identical sound characteristics?
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Mar 26, 2002 at 1:00 PM Post #2 of 33

Lizard_1

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Quote:

Originally posted by gloco
For someone who has so many posts, i feel like a schmuck.

Why are some cans high impedance (ohmage) while others are low? After reading that some of the more expensive cans are low impedance (like the W2002, the HP1000), then why are the Sennheisers high impedance?


At 300 ohms, the HD 600 can be insensitive to cable length and capacitance which can affect high frequency. This also gives a stable performance.
 
Mar 26, 2002 at 1:14 PM Post #3 of 33

Audio-Me

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Yup, gets rid of nasties, instead of shuving the sick grain and noise in your face.

Why do some people like myself prefer large engines over efficient toy motors? They don't whine and rattle, and just flat out feel good to drive (there's tons more reasons but they're don't correlate to audio).
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Mar 26, 2002 at 4:48 PM Post #4 of 33

markl

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Doubt it's much of an issue. Most regular speakers are between 4 and 8 ohms. Are they all full of "hashy nasties"? No.

markl
 
Mar 26, 2002 at 5:17 PM Post #5 of 33

pedxing

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Higher resistance usually means the headphones do not require as much current to drive. Grado are 32 ohms and require a relatively more powerful amp to drive because it draws current. HD600's or HD580's for example need more voltage swing to drive them to their potential.

Also, high resistant headphones are better for an array of headphone jacks that are driven by one power source. Assuming each headphone has the same resistance, if you plug them into a simple headphone jack array, the current is divided equally between them. This is not good if they require a lot of current. With high resistant headphones, the current becomes a minor issue.
 
Mar 26, 2002 at 5:37 PM Post #6 of 33

kwkarth

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Due to time constraints, I'm gonna make this short, but please feel free to ask questions.

Headphone impedance is a function of the resistance, inductance and capacitance of the total "system." Plug, cord, and driver voice coil. The Sennheisers use aluminum wire for the voice coil rather than OFC copper, presumably for lower moving mass. The higher resistance of aluminum than copper probably is not a significant factor here given the total length of the voice coil wire, however, it is a factor.

Headphone impedance has no direct correlation to efficiency. The efficiency of a headphone is determined by the relative strength of the magnetic field that the voice coil is immersed in as well as the strength in flux that the voice coil is able to produce from voltage/current applied to it. All of this is then factored into the ability of the diaphragm to move the amount of air necessary to wiggle your eardrum appropriately.

One generally axiomatic truth to remember is that as you lower impedance in a system, you also lower the relative effect that inductive and capacitive loads in the rest of the system have on your sound, but you also typically raise the general harmonic distortion products of the amplifier.

So, all of these factors are balanced against one another by the designer in creating a headphone.

I'm sure I left something out since I dashed this off as I was on my way out the door to a meeting. So, please ask lots of questions so we can get to the bottom of all of this!!

Cheers!
 
Mar 26, 2002 at 6:04 PM Post #7 of 33

Beagle

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kwkarth: Thank you very much for that explanation. I have been waiting over 10 years to hear a concise accurate explanation of what governs headphone efficiency/impedance.

Moderators, please put this in the archives.
 
Mar 26, 2002 at 7:06 PM Post #8 of 33

pedxing

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Quote:

Originally posted by kwkarth

One generally axiomatic truth to remember is that as you lower impedance in a system, you also lower the relative effect that inductive and capacative loads in the rest of the system have on your sound, but you also typically raise the general harmonic distortion products of the amplifier.


What type of effects do inductive and capacative loads have on the sound? Why does lowering impedence lowers these effects?
 
Mar 26, 2002 at 10:49 PM Post #9 of 33

kwkarth

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pedxing wrote:
"What type of effects do inductive and capacitive loads have on the sound? Why does lowering impedance lowers these effects?"

Great questions! Following are very simplistic explanations designed to help us understand the nature of the beast.

Inductive and capacitive loading affect the frequency response of a system in the following ways;

A capacitor conducts high frequencies and by nature blocks low frequencies. A capacitor conducts AC and blocks DC. As capacitive value rises, the amount of low frequency conduction increases. So if capacitive loading is in parallel with your signal it shorts or shunts more and more high frequency information away. So in a cable for example, the higher the capacitive value of that cable, to more high frequency information will be lost through that cable.

An inductor conducts or passes low frequency information by nature and impedes the flow of high frequencies. An inductor conducts DC and blocks AC. As inductive value rises, the amount of high frequency conduction decreases. An inductive load in parallel with your signal will diminish low frequencies.

The “impedance” of a circuit has two primary components. The real or pure dc resistance part and the “imaginary” component comprised of purely inductive and capacitive reactance values. Those reactive values as noted previously, vary with frequency.

At audio frequencies, resistance is typically the major component of the total impedance of a circuit. As you can imagine in a circuit, if this series resistive value increases, the parallel capacitive component becomes an increasingly important part of the circuit in terms of its effect on overall frequency response. The converse is true as well.

I hope this helps. Please feel free to continue asking questions because I’ve made a lot of assumptions and generalizations here to keep things simple and brief.

Cheers!
 
Mar 27, 2002 at 2:07 AM Post #10 of 33

Lizard_1

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Quote:

Originally posted by markl
Doubt it's much of an issue. Most regular speakers are between 4 and 8 ohms. Are they all full of "hashy nasties"? No.

markl


I do not know how you gonna mount those speakers on your head and shoulders, anything of this nature will really be in your face! But if you chose to listen away from them, ambience noise, conversation, the tv ... can help mask alot of these irregularities.
 
Mar 27, 2002 at 4:40 AM Post #11 of 33

delenda est Sony

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Pedxing---

don't Grados need a less powerful amp to drive em due to their low impedance? I thought the Senn 300 Ohm models needed more power to driver because of their high impedance...

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Mar 27, 2002 at 5:05 AM Post #13 of 33

skippy

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sensitivity is representative of the power needed to drive the cans. you just need a higher voltage swing for the higher impedance cans.
 
Mar 27, 2002 at 5:19 AM Post #14 of 33

delenda est Sony

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ahh--voltage vs current! Got it; thanks RMS! Do these different needs have any mandatory effects on sound or can the design compensate?
 
Mar 27, 2002 at 5:20 AM Post #15 of 33

gloco

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Quote:

Originally posted by RMSzero
Power isn't a good term. They both need power, but different ones need different kinds of power. 300 ohm Senns need high voltage gain, where 32-ohm Grados need high current.


Can you please elaborate "high current?"
 

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