Could someone please help a new audiophile learn a little about Impedance, Ohms, and Hertz?
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HyperTooth

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   Can someone please explain to me how Ohms and Hertz affect the quality of a headphone? I've recently got into the hi-fi world, I am a completely confused as how this all works. I recently bought a pair of Harmon/Kardon CL's and a Creative Sound Blaster ZX sound card. With it comes a built in DAC and 600 Ohm impedance built in amp, I thought this would power my HK and give it a little more oomph since they tend to run a little low (My traveling headphone since they're compact, closed-backed, and the cups swivel).

   Now, I have had plans to buy a cheap FiiO E6/E03k (Upgrading to the better E17/E09K when I bought my Beyerdynamic/AKG's) Amp/DAC combo on amazon for my sennheiser HD449's and Fisher Audio FA-004. The HK's sound really bad with the built in amp of my sound card, like I am underwater. The Sennheiser HD449's sounds a lot better with the amp, the bass is much more responsive. So I know it works. What combo for the HK would work best for a amp/DAC combo, I was thinking the E6/E03K combo from FiiO but I am afraid I will not purchase the right items. I just want a little more power out of my HK's. Here the sound card specs below- 

 

Audio Processor: Sound Core3D
Audio Resolution: 24-Bit
Digital Audio Convertor (DAC): Cirrus Logic
Signal to Noise Ratio (SNR) (20kHz Low-pass filter, A-Wgt): 116dB
Maximum Playback Quality: 5.1 : Up to 96kHz
Stereo Direct: Up to 192kHz
Frequency Response @96kHz: 5.1 : Up to 96kHz
Front Channel Out : 10Hz to 45kHz
Rear Channel Out : 15Hz to 45kHz
Center Out : 10Hz to 45kHz
Headphone (33 ohms): 10Hz to 45kHz
Frequency Response @192kHz (Stereo Direct Only): Front Channel Out : 10Hz to 88kHz
16-bit to 24-bit Recording Sample Rates: 8,11.025,16, 22.05, 24, 32, 44.1, 48, 96 (kHz)
16-bit to 24-bit Playback Sample Rates: 8,11.025,16, 22.05, 24, 32, 44.1, 48, 96, 192 (kHz)
Maximum Recording Quality: Up to 24-bit/96kHz
I/O Ports (Main Card): Headphone : 1 x Amplified 3.5mm jack
Speaker Out : 3 x 3.5mm jacks(F/R/C-Sub)
Line / Mic In : 1x shared 3.5mm jack
Optical Out : 1x TOSLINK
Optical In : 1x TOSLINK
600 Ohm Amplified Headphone Output: Maxim MAX97220A
 
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MindsMirror

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None of those specs really tell you anything about how it sounds or why you had that experience with your HK headphones. The output impedance might be able to explain it, but they don't specify it. I have the Z (not ZX), I don't know how much they have in common, but I can tell you from my own measurements that mine has about 28 Ohm output impedance. Do a google search for something like "headphone amp output impedance" if you want to learn more about it and how it can affect the sound in your headphones. That 600 Ohm number is just them saying it is powerful enough to drive 600 Ohm headphones, it has nothing to do with the amp's output impedance.
 
I don't know if one of the cheaper Fiio DACs will improve anything over the ZX. The Fiio E06 might. If you're going to try one of the cheaper Fiio alternatives before upgrading, I'd say try just the Fiio amp first using the SBZX's DAC and see how that sounds.
 
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HarleyZH

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The Hertz range given for headphones on spec sheets don't really matter. We hear between 20 Hz and 20,000 Hz (20KHz) for the most part. When looking at Graphs, spikes at frequencies like 6 KHz or 10 KHz will tell you that the headphone has a spike in the treble and may be bright. Big bumps around 100Hz tell you that the headphones may have a bass boost. While spikes around 2-4KHz are in the "presence region" and may create a feeling of shoutiness in the sound signature. Human hearing is at its weakest at the extremes of bass and treble, the mid range is the easiest heard to the ear. As volume raises this curve changes in our hearing, louder listening levels will sometimes change a headphone from sounding more neutral at a lower volume, to being over bearing in the bass and treble. This is often called the Fletcher Munson curve.
 
The Impedance is represented by a resistance (ohm rating). Basically a higher ohm rating, by ohms law, means less current going through the headphone. You then need a higher voltage to provide that current. Basically if two headphones are equally sensitive, then the one with the higher impedance will require more drive/power to get it to the same volume level as the lower impedance headphone. 
 
Sensitivity is one of the other more important stats to figure out what amp you may need. Sensitivity comes in two types of ratings. The Decibel Rating / Watts rating e.g. 100 Db/Mw. This means to reach 100Db you need 1 Mw of power. This does not take into account dynamic peaks and all that of course, you will want a fair bit of power more than that lest you get clipping and distortion. The other representation is Db / Volts eg. 105 Db/V. There is a method to convert but I won't go into it here.
 
Headphone amplifiers have an output impedance rating, the higher this is, the higher the headphone rating need be for optimal operation. Headphones with lower ratings paired with high rating amps can often change the sound signature of the headphone, and create distortion. Likewise, headphone cables have impedance ratings, some have noticed that a headphone called the Philips X1 had a high ohm cable and sounded slightly better with lower rated cables. Just some things to take into account for the future. This is a rarer problem than amp impedance problems. Amplifier and headphone ratings have what some believe to be a golden ration of 1/8 or better. So a 4ohm amp output pairs best with 32+ohm rated headphones.
 
So a high ohm headphone with a low sensitivity rating is going to be very hard to drive. Some headphones have been driven off speaker amps to achieve their best. 
 
For future reference here is a calculator for headphones amps and volume.
 
http://www.headphone-amplifier.com/calculator.htm
 
There is also a quick and easy calculator for ohms, volts, current and power on google.
 
Hope this helps.
 
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