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Help with understanding Ohms and Hertz?

post #1 of 12
Thread Starter 

   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
 
post #2 of 12

There is a Computer Audio section of the forum.

post #3 of 12

From practical point of view, headphone impedance will tell you how much power the amp can output into them, usually amps have their performance peaks at 20-40ohms. Amp output impedance can affect your headphone frequency response, and it should be as low as possible (at least 8 times less than impedance of the headphones you use, most high quality amps are below 2 ohms).

 

Frequency response spec of amps usually mean nothing. You should be looking for an amp that is flat (+/- 0.3dB) from 30Hz to 16kHz.

 

Also don't bother with high resolution support, 16bit / 44kHz is perfect for reproduction of any audible sound.

post #4 of 12
Thread Starter 
Quote:
 "There is a Computer Audio section of the forum."

 

 

 Ah, sorry if my question didn't come out correctly. I wasn't really concerned with my Sound Card at all, more so how Ohms and hertz affect my headphones. Why a 600 Ohms Amp/Dac would be bad for these but not those so to speak. (It works very well for my Sennheiser HD449's but not my Harman/Kardon CL's).

 

Quote:
 "Usually amps have their performance peaks at 20-40ohms. Amp output impedance can affect your headphone frequency response, and it should be as low as possible (at least 8 times less than impedance of the headphones you use, most high quality amps are below 2 ohms)."

 

 

   Hm, well then it seems then that the amp is really bad then isn't it? At 600 Ohms. . . I though this was like Watts or something, like a car amp hahah. I though it was like a 50 watt amp vs a 1000 watt amp. I know, I am ignorant, yet like I said I just entered this whole world of higher-end audio equipment. So, then, would you recommend a decent Amp that would be both portable and work well with my headphones? Also, once I kinda get attuned, a more full understanding of how audio works, would you reconmend the AKG K701, Beyerdynamic DT880 Pro or Sennheiser HD600's?

 

      --Thanks guys!!

post #5 of 12
Quote:
Originally Posted by HyperTooth View Post
 

   Hm, well then it seems then that the amp is really bad then isn't it? At 600 Ohms. . . I though this was like Watts or something, like a car amp hahah. I though it was like a 50 watt amp vs a 1000 watt amp. I know, I am ignorant, yet like I said I just entered this whole world of higher-end audio equipment. So, then, would you recommend a decent Amp that would be both portable and work well with my headphones? Also, once I kinda get attuned, a more full understanding of how audio works, would you reconmend the AKG K701, Beyerdynamic DT880 Pro or Sennheiser HD600's?

Maybe it's not that bad, but probably it will color your headphones a bit (like by adding 2dB to mid-bass, you can google "Headphone & Amp Impedance" for a set of articles describing this phenomenon), and some people might like it.

 

For portable audio, I would just use my phone internal amp and headphones that are tuned for portable use. I think that external amps/dacs are a waste of space.

 

Can't recommend any of those headphones, since I have never heard any of them, but judging by the subjective reviews I have read, HD600 is very often recommended as "entry level audiophile headphone". And objectively (looking on the measurements), they have a very balanced frequency response vs. others (K701 - too much 2kHz, high distortion; DT880 - too much 9kHz).

post #6 of 12

Far from being entry level headphones, the  K 701, DT 880 and HD 600 are all former flagships.  However, they have quite different sound signatures.  See these excellent summaries of the three (with the similar K 702 standing in for the K 701):

 

http://www.head-fi.org/t/634201/battle-of-the-flagships-58-headphones-compared-update-audeze-lcd-2-revision-2-6-4-13#user_HD600

 

http://www.head-fi.org/t/634201/battle-of-the-flagships-58-headphones-compared-update-audeze-lcd-2-revision-2-6-4-13#user_DT880

 

http://www.head-fi.org/t/634201/battle-of-the-flagships-58-headphones-compared-update-audeze-lcd-2-revision-2-6-4-13#user_K702

 

If interested in the AKG, don't overlook the newer sibling--the Q 701.

post #7 of 12
Thread Starter 
Quote:
 "For portable audio, I would just use my phone internal amp and headphones that are tuned for portable use. I think that external amps/dacs are a waste of space."

 

 

   What would you recommend then for a decent on/around ear portable headphone then? I've the Fischer Audio's but they seem to lack a decent bass and the treble sounds really odd to me. I like them for light listening occasions but they mostly collect dust in my closet. Thankfully my dad re-gifted them to me last year for Easter and I paid nothing for them. I love the Sennheiser's but they seem too bulky to carry with me at all times and the lack of swiveling heads makes it uncomfy to wear these into town. 

 

Quote:
 "judging by the subjective reviews I have read, HD600 is very often recommended as "entry level audiophile headphone". And objectively (looking on the measurements), they have a very balanced frequency response vs. others (K701 - too much 2kHz, high distortion; DT880 - too much 9kHz)."

 

 

   Sheesh, your ears must be really accustomed to this to be able to pick up on a single frequency haha. I really like the AKG's though, they look. . .well awesome. I know, letting supercilious, non-important things get in the way of awesome sound haha. Anyway, a family friend is giving me his old HD558's since he has bought something called an Audeze (They look cool but I bet his wife shot him once she saw the receipt.)  recently and has since begun liquidating all his sound equipment. If you can't tell already I am a college student and this dude is kinda the on who got me into all this. Before, hate to say it, I was using SOL's haha. . .

   Are amps really something I should look into for home listening then? If so, throw me some idea's. Remember, college budget so I am trying to be realistic. . . As much as reality sucks sometimes. (Looking at you 70 inch SHARP curved beauty).

post #8 of 12

Ohms are a measure of resistance to electrical current.  When the electric current is AC current, to make things simpler than they really are, we call it impedance.  The higher the number the more resistance to current.  Hertz is a measure of the frequency of the AC current or signal.  The audible frequency spectrum runs from around 20hz to around 20,000hz.  The frequency of radio signals is higher.  The db or decibel is a measure of sound pressure or loudness.

 

Amplifiers are good at handling loads with a higher impedance (ohms) than its own output impedance.  So amplifiers normally have a low impedance and the load they drive will have a higher impedance.  As indicated above, the higher the impedance, the more amplifier power is required to reach a given volume level.  But we want a higher impedance in the load than in the amplifier output.  You said the sound card has an output impedance of 600 ohms.  The HK cans you bought probably have a lower impedance than 600 and that is why you had poor performance.  The Sennheiser likely have a higher impedance and therefore work better with the amp on the sound card.  Most high fidelity amplifiers have a very low output impedance - just a few ohms.  So the problem is likely that the sound card's amplifier is has an output impedance that is too hight for your particulary headphones.  You fix that by using a low impedance amplifier like the headphone jack on a stereo receiver or a dedicated headphone amplifier.

 

Ideally, we want the sound system to reproduce every frequency throughout that 20hz to 20khz audible spectrum with exactly the same volume.  That would make the sound have higher fidelity or the ability to sound more like real life.  Most amplifiers can do this or at least do it well enough that they don't alter sound.  Microphones, speakers, headphones and any device that converts mechanical energy to sound energy or vice are called transducers.  Transducers cannot reproduce all the frequencies at the same volume.  There is always some audible variance because the impedance varies with frequency and it varies differently for every transducer.  Because of that all transducers sound different from each other when they are operating.  No two headphones will sound exactly alike.  No two speakers will either.

 

We measure the variances in the volume by the db or decibel.  When the sound is louder than normal at a given frequency we give it a positive variance measured in db and when it is softer than normal we give it a negative one.  So the specification will include the frequencies  of that 20hz to 20khz spectrum the unit can produce and how much it varies from normal at the maximum positive and negative point.  So if the specification calls for 20hz ro 20khz -12db to +3db, then those two numbers represent the maximum variation from normal.  This figure is measured by playing test tones at a given volume and various frequencies and the measuring the sound pressure or volume for each frequency.  Modern equipment simply transmits all the frequencies at once and uses a computer to draw a graph of the response of the unit to the frequency spectrum.  The graphs tell you more because they tell you, for instance, at which frequencies the maximum sound variations occur.

 

I hope I didn't confuse you.  I'll just repeat that your headphones will probably sound better with a proper amplifier with a low output impedance.


Edited by blades - 7/12/14 at 2:48am
post #9 of 12
Quote:
Originally Posted by HyperTooth View Post

 

   Sheesh, your ears must be really accustomed to this to be able to pick up on a single frequency haha. I really like the AKG's though, they look. . .well awesome. I know, letting supercilious, non-important things get in the way of awesome sound haha. Anyway, a family friend is giving me his old HD558's since he has bought something called an Audeze (They look cool but I bet his wife shot him once she saw the receipt.)  recently and has since begun liquidating all his sound equipment. If you can't tell already I am a college student and this dude is kinda the on who got me into all this. Before, hate to say it, I was using SOL's haha. . .

Frequency peaks can sound very bad (for example 6-8kHz peaks can cause sibilance in vocals), change perceived sound signature (one peak in mid treble that is above other frequencies can make seemingly neutral headphone sound very bright), or even damage your hearing (especially in sensitive 4-8kHz region). If you want to learn more how each frequency range influences the perception of sound I recommend this chart.

 

If you're on budget I recommend being highly skeptical about any audiophile claims. Just get fairly neutral headphone (like HD600), amp with plenty of power (Monoprice desktop amp+dac seems good) and you will have your cheap audiophile end-game setup for less than $500. But it's better to ask first here on the forum for the recommendation, perhaps there are better headphones for you than HD600 (some say that they are slightly dark sounding).

post #10 of 12
Thread Starter 
Quote:
 "I hope I didn't confuse you.  I'll just repeat that your headphones will probably sound better with a proper amplifier with a low output impedance."

 

 

     Geez, you guys really know a thing or two behind the science of sound. It's amazing how much I am learning here, thanks guy! Keep it coming if you have anything to add to the conversation, I am all ears. So I figured out that the Harman/Kardon's have a lower Ohm rating than my sound card, it's 32 ohms and I am currently looking at that Monoprice Amp Ieee754 recommended. Nice price and if an audiophile is recommending it as an entry level 'end all' then you bet I am going to look into it.

 

Quote:
 "If interested in the AKG, don't overlook the newer sibling--the Q 701."

 

 

   Hey thanks Jag, those were all great reads and a plethora of knowledge. It's really made me think about the AKG's a little bit more, than again I have a deal lined up for a pair of K 702's for $150 bucks. I'm going to mull it over, defiantly see what they look and sound like in person before I sink my cash into them. I really am leaning towards the HD's though if I can find them for the right price. So far I've not seen a pair under $250 other than amazons third party sellers to which I am very skeptical. I might just pounce on those AKG's if they fit the bill, I couldn't really get into the looks of the Q 701.  . too animated for me in that lime green color.

 

Quote:
 "Frequency peaks can sound very bad (for example 6-8kHz peaks can cause sibilance in vocals), change perceived sound signature (one peak in mid treble that is above other frequencies can make seemingly neutral headphone sound very bright), or even damage your hearing (especially in sensitive 4-8kHz region). If you want to learn more how each frequency range influences the perception of sound I recommend this chart."

 

 

   I suppose you would be right, a high peak at higher frequencies would sound atrocious and be painful haha. I went ahead and took a look at that chart, along with most information on this post haha, and it really interesting to see the guitar and the harp have such depth of range. One thing I was confused about is the type of Bass. Isn't a low a low? Why would there be sub-bass and then just bass, how do you perceive the difference? 

 

Quote:
 "If you're on budget I recommend being highly skeptical about any audiophile claims. Just get fairly neutral headphone (like HD600), amp with plenty of power (Monoprice desktop amp+dac seems good) and you will have your cheap audiophile end-game setup for less than $500."

 

    This is better than the FiiO I assume, so I am starting to really read up on what makes a good audiophile amp and DAC on the forums now. Cheap doesn't always have to mean bad, in my experience something that is cheap can be good. Therefore I am not looking at price as a cause to overlook a certain item. I've read a couple forums where a $60 dollar headphone surprised the heck out of the user, like the Creative Aurva! or something like that haha.
 

post #11 of 12

If it makes any difference the Q701 is available in three colors, including white and black.

post #12 of 12
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