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Topic: Bass Response affected by ipod headphone jacks?

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Old 04-06-2005, 11:23 AM
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Bass Response affected by ipod headphone jacks?

This article proposes that the Bass output of the shuffle is better than the ipod.

http://www.pcmag.com/article2/0,1759,1777890,00.asp

I have to admit in back to back testing (same song, same headphone) the shuffle does sound much punchier, fuller and very satisfying).

I have a 3G 40GB ipod using ER6i's
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Old 04-07-2005, 03:06 PM
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The reason that bass is better on the Shuffle than the regular iPods is because the shuffle does not have DC blocking capcitors on the output (though it uses other methods to block DC from reaching the headphones). All non-shuffle iPods have a capacitor on the output to prevent DC from damaging the headphones. The downside to this capacitor that it, in conjunction with the impedance of the headphones, creates a high pass filter. For example, with 32 ohm headphones connected directly to the headphone port of the iPod, a high pass filter is created with a corner frequency of 50hz. The human ear can hear all the way down to 20 hz. The higher the impedance of the headphones, the lower the corner frequency of the high pass filter becomes. Alomst all in ear headphones are 32 ohms or lower, so the bass will seem attenuated. In order to effectively allow all headphones to run all the way down to 20 hz, a headphone amplifier must be used. Alomst all headphone amplifiers have an input impedance of many thousands of ohms. My company, Simpl Acoustics, makes a headphone amplifier for the iPod with an input impedance of about 10,000 ohms. This high impedance moves the corner frequency of the high-pass filter to below 7 hz, well below the threshold of human hearing, and below what an iPod can reproduce anyway.
I dont want this to come off as an ad for Simpl Acoustics. any headphone amplifier should be able to allow the headphone port to operate full range. In fact, it is possible to build a headphone amplifier for very little money that works quite well. Check out http://tangentsoft.net/audio/cmoy-tutorial/ . This is a great tutorial for building your own CMOY style headphone amp into an altoids mint tin.

Jonathon Kennemer
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Simpl Acoustics
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Old 04-07-2005, 06:24 PM
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I've not done any scientific tests, but phones which exhibit 70 ohms or more impedance in the lows seems to recover from the bass loss. As I said, that's not a scientific test but where I have been more thorough is with slightly higher loads... there's definitely no audible difference in the lows from the iPod between a 300 ohm load and a line level load such as with the Simpl HP amp.


It is perfectly possible to power the slightly higher-impedance phones without a headphone amp if you choose carefully, especially given the power of the iPods built in HP amp. Rather than wasting your money in mediocre phones and a headphone amp (making your iPod much less portable), I'd suggest you save and just buy a good higher-impedance phone. The Sennheiser HD25-1 is such an article. It's efficient for a higher-impedance phone, has a punchy bass and accurate sound as standard, which isn't held back by the iPod. It's also quite portable and almost every part is replaceable.



16Gb iPhone...
...but N95 paired with Gear4 BluEye + 32Gb Touch actually FTW.

Last edited by thedodgyguy; 04-08-2005 at 04:27 AM.
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Old 04-08-2005, 02:00 PM
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I broke the story a little earlier here:
http://forums.ipodlounge.com/showthr...threadid=85383

And more discussion here:
http://www4.head-fi.org/forums/showthread.php?t=113315



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Topic: Bass Response affected by ipod headphone jacks?

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