Pls explain ohm to me in the nooby term.
Feb 27, 2006 at 5:29 PM Thread Starter Post #1 of 10

Qsilver2001

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Hi all,

Please do not laugh at me from the title.

I roughly knows that lower ohm can be use unamp with portable.
Higher ohm are harder to drive them, when amped it brings out the potential of a headphone. Hope I am right after reading many posts in this forum.

What I like to know is does it need a monster amp to drive those 600ohm cans?
What will happen to a 32ohm or 80ohm cans if use with a monster amp?

At present I have a cmoy2 & pa2v2 amp, SR80 & ATH-Pro700ms. In future might get a good for home base.

Hope answers will help me to decide on which ohm cans to get.

Thank you all in advance.
 
Feb 27, 2006 at 6:05 PM Post #2 of 10

upstateguy

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Hi Qs

I'm not really sure what you would like to know....

ohms are a measure of resistance.... the more resistance in a pair of headphones, the more power will be needed to drive them, but they are still just headphones and not speakers, so I'm not sure how "monster" applies. For instance, I can plug my Beyerdynamic DT880s directly into a little mp2 player and listen to the music. (see below) However, if I want any kind of volume I will have to use an amp.


In an amp like the Hornet, for example, there is a gain switch in the back that allows you to choose one of three gain settings, so you will be able to use low resistance headphones and in the ear models and still have a usable range for your volume control, instead of just "barely on" or "too loud".

My understanding about some of the low impedance in the ear phones, is that sometimes there is an audible noise floor which is usually described as hissing. You'll have to ask some of the owners of those phones if you need a better answer.

Regards

USG

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Feb 27, 2006 at 6:11 PM Post #3 of 10

Publius

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Higher impedance phones require a higher voltage to drive the same amount of power through them. Headphone loudness is rated in terms of power input, not voltage input. Therefore, for two headphones of the same efficiency with one a higher impedance, that one will require more voltage.

The usual wisdom is that most amps are not designed for particularly high voltages, and could do nasty things at the limits (clip, distort etc). Therefore you need something that could potentially swing +-10V p-p to drive all headphones acceptable.

Noise levels for amplifiers are highly impedance-dependent for all sorts of reasons, which is why low impedance phones get the reputation for noisiness. In reality, low impedance cans are just as hard to design amps for as high impedance cans. One is very voltage dependent and the other is very current dependent.
 
Feb 27, 2006 at 6:16 PM Post #4 of 10

Qsilver2001

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Thanks upstateguy for the reply,

I was wondering why some choose a 600ohm cans rather than those 32-250ohm cans. What is the benefits of having those high ohms? What are the negatives of those lower ohms cans?
 
Feb 27, 2006 at 6:26 PM Post #5 of 10

dkjohnso

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Many high end cans have high impedances becuase they sacrifice efficiency for awesome sound. It's like a Ferrari or Porsche - they have awesome performance due to huge engines, but crappy gas mileage.
 
Feb 27, 2006 at 6:31 PM Post #6 of 10

Qsilver2001

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Ah, ok if i read it correctly.
Low impedance cans can be use w/o amp and yet have sufficent volumes but will or tends to have hissing sound.
High impedance cans will need amp using gain to boost the volume and yet less or no hissing sound/noise floor?

Also high impedance cans will product awesome sound but need high end amps to achieve that kinda awesome sound? "Expensive Hobby"
biggrin.gif
 
Feb 27, 2006 at 6:44 PM Post #7 of 10

jagorev

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1. Power (volume, roughly) = Voltage x Current

2. Voltage = Current x Resistance (impedance)

or

3. Resistance = Voltage/Current

So...putting right hand side of equation 3 into equation 2, we get:

Power = Current^2 x Resistance

Hence, to get a certain power or volume level, with a low-resistance (ohm) headphone, you need higher current. With a high resistance headphone, you need high voltage (which conversely implies low current).

The water pipe analogy is a good one, explained quite well in this page.

The PA2V2 you have is a high-current design good with low-impedance headphones like the Grado or ATH. A CMOY or PIMETA or MINT has a high-voltage design, which is much more preferable for high-impedance Sennheisers or Beyerdynamics.

Also, impedance itself doesn't tell the whole story. You need to look at sensitivity (measured as sound pressure level in dB/mW). A very sensitive headphone rarely needs an amp - Ety er-6i is an example of a headphone with ridiculously good sensitivity...while low-sensitivity headphone (like the Sennheiser HD 201) might need an amp even if its impedance is only 24 or 32 ohms. The thing to keep in mind about sensitivity is that it increases on a logarithmic scale rather than a linear one. So a headphone with an SPL of 103 dB is about twice as sensitive as one at 97 dB.
 
Feb 27, 2006 at 6:55 PM Post #8 of 10

Qsilver2001

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Quote:

Originally Posted by Publius
Higher impedance phones require a higher voltage to drive the same amount of power through them. Headphone loudness is rated in terms of power input, not voltage input. Therefore, for two headphones of the same efficiency with one a higher impedance, that one will require more voltage.

The usual wisdom is that most amps are not designed for particularly high voltages, and could do nasty things at the limits (clip, distort etc). Therefore you need something that could potentially swing +-10V p-p to drive all headphones acceptable.

Noise levels for amplifiers are highly impedance-dependent for all sorts of reasons, which is why low impedance phones get the reputation for noisiness. In reality, low impedance cans are just as hard to design amps for as high impedance cans. One is very voltage dependent and the other is very current dependent.



Headphone Loudness driven by power input.
High impendance cans require more voltages to drive than low impedance cans inorder to produce good/quality sound. Right?
Amps that do not have high voltages at the limits can create etc clips, distortion that can be heard by both high or low impedance cans?

Will a high voltages amp damage a low impedance cans?

Sorry can't get you this part which one is voltage depandent.(my guess is headphones) So the current dependent?(Amps?)
 
Feb 27, 2006 at 7:04 PM Post #9 of 10

Qsilver2001

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jagorev,

Ah now I understand more as in amps are design differently.
Some are high current designs where others are high voltages designs.

So for picking up cans or amps, one need to match it in order to get the best/quality sound.

Man, this hi-fi thing is so complicated.

Thank you all for the input to help me understand more!

How can i tell from an amp if its design for high current or high voltage? From its tech spec?
What should I look for?
 

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