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Impedance, low vs high benefits

post #1 of 5
Thread Starter 

Why is it that you have what I call for this topic Group A including  the HD800 and the T1 at 300 & 600 ohms, and then at the other side  Group B including  the LCD3, PS1000 and TH-900 at respectively 50, 32, and 25 ohms ?  Group A is much harder to drive, even amplified. Obviously, the engineers design them  and  have the reasons for each, but I consider all these high end models and in the same league. Like you don't need high or low impedance to have high end performance, but  do you get some other benefit when you  design 300 ohms or higher while giving up the ease of drive with low impedance ? Beyer has their own T5p at 32 ohms, but it does not look in the same level as the T1.

post #2 of 5
Generally speaking, it is easier to design a headphone that performs better that has a high impedance. A higher impedance allows for more turns of wire to be used in the voice coil and this results in a better 'motor system', higher impedance headphones also require less current, which reduces distortion. Furthermore, higher impedance headphones are more resistant to poorly-designed amplifiers that have high output impedance. If your amplifier has an output impedance that is more than 8x lower than the headphone's impedance, you can experience some degradation in sound quality, particularly in the bass as damping is reduced.

So for example, if you are using a 600 Ohm headphone, your amp's output impedance needs to be lower than 75 Ohms. If you have a 32 Ohm headphone, the output impedance needs to be lower than 4 Ohms. Nearly all amps available today do not have output impedance that exceeds 75 Ohms, but it is somewhat difficult to find an amp that has an output impedance that is lower than 4 Ohms. Ideally, an amp should have an output impedance as close to 0 Ohms as possible, but in practice this is rather rare.

Nowadays, since we have a lot of very good portable sources, headphone makers often design their flagships with low impedance in order to make them compatible with portable gear.

In the end, it all depends on your amplifier. If you have a well-designed amplifier with low output impedance, it is safe to assume that low-impedance headphones will perform very well with them. On the other hand, if your amplifier has high output impedance, it is a bad idea to use low-impedance headphones with them as you will get degraded sound quality. Furthermore, many tube amps also are known to perform poorly with low-impedance headphones.

With today's technology, it is entirely possible to design a low-impedance headphone that performs extremely well, you just have to be aware that some of your older sources might not be compatible with them. I actually think a lot of people drive their low impedance headphones with amps that have high output impedance and this is what contributes to the general consensus that they sound worse than high-impedance headphones.
Edited by jupitreas - 12/3/12 at 4:53am
post #3 of 5
Thread Starter 

Wow, that was perfect explanation. Thanks a lot. Now you got me digging to get the specs of my headphone amp and compare. I got them. My phones are 50 ohms, and my amp output impedance is 2 ohms unbalanced, and 4 ohms balanced, so I should be fine from impedance point of view.


Edited by zeiter - 12/3/12 at 1:01pm
post #4 of 5

except for the case of the same model, offered with different Z, where  its mostly wrong....

 

given the same magnetic circuit, gap, voice coil dimensions - the number of turns can be changed by making a corresponding change in wire size to fit the same dimensions, have the same total conductor weight

 

the electro-acoustic parameters are then identically scaled by terminal Z - you would get the same result with the inclusion of a ideal transformer

 

the motor relations aren't any better for the high Z case - things like electromechanical damping ratio, resonance frequencies stay the same - only the ratio of V,I at the terminals is scaled by the turns ratio

 

there are limits imposed by larger faction of the coil cross section being insulation with extremely fine wire so practical implementations may not meet this ideal - but it is a very basic relation for dynamic driver motor design

 

of course there's no knowing if the headphone designers even try when offering differing Z of the same model - if the sensitivity stays the same in dB/mW, the bass mass-spring hump looks the same except for the sale factor constant, then there's a chance they followed this principle


Edited by jcx - 12/3/12 at 7:35pm
post #5 of 5
Quote:
Originally Posted by zeiter View Post

Why is it that you have what I call for this topic Group A including  the HD800 and the T1 at 300 & 600 ohms, and then at the other side  Group B including  the LCD3, PS1000 and TH-900 at respectively 50, 32, and 25 ohms ?  Group A is much harder to drive, even amplified. Obviously, the engineers design them  and  have the reasons for each, but I consider all these high end models and in the same league. Like you don't need high or low impedance to have high end performance, but  do you get some other benefit when you  design 300 ohms or higher while giving up the ease of drive with low impedance ? Beyer has their own T5p at 32 ohms, but it does not look in the same level as the T1.

I think what ready affect the Ohms of the headphones is the manufacturing cost and what part of the market the headphone makers are trying to sell to.

Expect a headphone manufacturer to use the cheapest materials they can get away with, anything to keeps cost down.

Also R & D is an expense, so the less changes or improvement you do, the less costs are incurred.

I think in the past most people used their home receivers to drive their 250-Ohm & 300-Ohm & 600-Ohm headphones, so headphone manufacturers that have been making the same 250, 300 & 600-Ohm headphone for the past 30 years, just keep

using the same basic diaphragm for the "receiver" crowd, Head Amps have only been built into sound card for about 4 years(?).

So I'm saying there are not really any newly designed 250, 300 or 600-Ohm headphone diaphragms, there are just old designs with a few tweekes.

I guess Beyerdynamics is one of the few headphone manufacturers do have some new designs for high Ohm headphones.

 

I think with the rise of portable audio players with decent audio support (thanks Apple), it became worth it for headphone manufacturers to spend R & D for good sounding (mosty portable type?) low Ohm headphones.

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