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May 25, 2005

What is a Parametric Equalizer and how to use it on Rio Karma.

Filed under: Audio — Manish Bansal @ 11:46 am

In it’s simplest form, a speaker is just an energy conversion device. It converts electrical signals to sound waves of various frequencies. Ideally, all the frequencies in the speaker output should be at the same level of loudness. If we plot the frequency repsones curve of such an ideal speaker, with frequency (in Hertz) on x-axis and loudness (in Decibals) on y-axis, it would be a flat line at 0db. But such ideal speakers don’t exist. It’s really really difficult to construct such an ideal device. Even if it could be built, it would be too expensive to be practical. That means that we are stuck with ordinary speakers that don’t sound so great, atleast not without some tuning.

The frequency response of an ordinary speaker looks like the outline of a mountain. I.e. the low and high frequencies are not amplified as much as the middle ones. My Sennheiser MX500 headphones have this frequency response, taken from Headroom:

The sole purpose of an equalizer is to compensate for this bias in the speakers. It brings all the frequencies to the same level of loudness. In other words, it equalizes them and hence the name “Equalizer”.

Equazliers on sotware based players (Winamp, iTunes etc.) are typically 10-band and those on digital audio players are typically 5-band. A typical 10-band equalizer:

The frequency shown under each bar is called the center frequency. Just as there are no ideal speakers, there is no ideal equalizer either. I.e. instead of being a straight vertical line, each of these bars is more like a bell. And the range of frequencies falling under this bell is called a frequency band. So a 10-band equazlier can amplify/attenuate 10 separate, but overlapping, frequency bands. Because these bands extend to some distance on either side of center frequency, boosting the center frequency actually boosts this whole band, with the effect being maximum at the center frequency.

In a normal equalizer, the only thing that a user can control is the amount of amplification for each band. But in a parametric equalizer, in addition to the amplification, you can also change the center frequency and the width of each band. This additional level of control comes in handy when matching a pair of headphones to a particular device. I have set the Equalizer on my Rio Karma as:

Center frequencyuency Gain Width
12000 Hz +6.0 db 4.0 octaves
2500 Hz +0.0 db 4.0 octaves
500 Hz -2.0 db 4.0 octaves
150 Hz +6.0 db 4.0 octaves
40 Hz +8.0 db 4.0 octaves

This setting makes MX500 give an almost flat response when used with Rio Karma. The nice player that the Karma is, it offers 3 custom equalizers. So I have set the other one to match my Philips HP800 cans (Based on subjective tests, since I could not find the frequency response curve for it).

To match your headphone to Rio Karma, you need the frequency response curve of Rio Karma and a way to see how your headphone and Rio karma interact at various equalizer settings. This is exactly what John M has done with his KarmaEQ application. But the headphone response curve given by headphone.com is not usable as it is. It has to be converted to a text file having frequency-gain pairs. There are many examples of this on John’s site. I created a file with 30 sets of frequency-gain pairs for Sennheiser MX500. The values don’t have to be highly precise. Just a simple eyeballing would do.

Now all that you have to do is import your headphone response file in the KarmaEQ and start experimenting. The idea is to have the resulting curve as flat as possible. When you are satisfied with the results in KarmaEQ, try that in Rio Karma and see how it sounds. Since sound quality is a subjective thing, the flat curve may not be up to your liking. But take that as the starting point and explore from there on. Happy EQing.

Update:The HydrogenAudio thread on this post contains lot of interesting points on the differences between listening on headphones and listening on speakers. A highly recommended reading. Also my Rio Karma is dead :-(. I did everything I could but it just won’t boot. Well..

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May 12, 2005

Why iTunes worked and why Yahoo music would work too!

Filed under: Audio,Opinions — Manish Bansal @ 11:27 am

Yahoo annoucnes it’s music store.

Way back in 1998, when I started collecting digital music, I used to use Windows Explorer to organize my music and Winamp to play it. It was not the best of setups but I didn’t know any better; Until i got an iBook.

The organization scheme used by iTunes completely blew me away. I actually spent 3 days cleaning up all my ID3 tags just so that I could use iTunes. It was that good. Just type a few letters and the song is there. No more mucking around with folders here and there and remembering where you put what. When iTunes for Windows was released, I made it my default player. Even though Winamp 5 has it’s own media library which works similarly, it’s no match for iTunes’ interface.

Now, iTunes for windows is a 20 MB download but I didn’t mind in the least. I just had to have it. The fact that I could buy songs through it was last thing on my mind. And that’s exactly why iTunes music store is such a success and so would be Yahoo music. If you want to buy songs from any online music store, you need a special software, which is different for each store! Imagine Amazon.com and BN.com each asking you to download 20 MB big software just so that you could buy books from them! Whereas you can buy books online using just your browser, you can’t buy music that way. No special software, no music. So how do you get people to download your special software? You do it the Apple way.

You make it so damn good that they start using it for their personal use, without any obligation to buy any stuff from you. The keyword here is “good”. I didn’t download iTunes to buy music. I downloaded it to organize the music that I already had. And that’s where Real and other stores fail. Their software is designed to make it easy for you to buy music, not to organize your existing collection. You can, of course, use it for that purpose but it is torturous to use. And this is where Yahoo gets it right (as did Apple). Infact, their music player is almost a copy of iTunes but with certain new features. It can play and encode OGG and FLAC, in addition to AAC and MP3. It has a UNIX-style shell. It supports open XSPF playlist format. How much more geeky can you get? It lets you share music through Yahoo Messanger and burn CDs. It even supports iPod for non-DRM files.

Being a beta release, it is missing a few things like an Equalizer and is quite slow to load. The best thing that I personally like about Yahoo music engine is that it supports FLAC format (playing and encoding) right out of the box. Since I rip all my CDs in FLAC and iTunes does not support it, I an switching over to YME. But I’ll keep Winamp around just in case and, of course, my trusty foobar2000.

Update 1:
I just ripped a few CDs using YME to FLAC format and the tags it fetched for those songs were the best I had ever seen. All the fields (song title, singer, album etc) were nicely formatted, with proper cases. I tried the ripping the same CDs in EAC and the freedb tags just made me cringe. All CAPS, wrong titles, and incomplete information. I guess YME fetches the tags from its own database instead of freedb. Well, one more reason to use YME.

Update 2:
I am really disappointed at the pace at which YME is being developed. There is still no equalizer, there are hardly any plugins, and there are some weird bugs in it. It cannot “see” an audio CD unless I login as Administrator. iTunes can read the same CDs just fine with a normal user account. It also shows Nero CD burning plugin as a removable device!

The weirdness does not end here. Turns out that YME uses Windows Media Player (or a part of it) in the background to play music. I think it is limited to just protected WMA files but I am not sure. The problem is that it even uses the graphic equalizer settings of Windows Media Player! So if you are not happy with the sound, YME help pages recommend to turn graphic equalizer off in WMP. How much more un-intuitive can you get?

Update 3:
Even though there is no built-in equalizer for YME, you can still use the equalizer on your soundcard. Some on-board soundcards (mostly found in corporate PCs) may not have one but otherwise every decent soundcard should have it. My Creative Soundblaster has a really good 10-band equalizer. And the nice thing about using soundcard EQ is that it is not limited to a particular player. It would work the same whether you use Winamp or Yahoo Music Engine.

Update 4: (Feb 13, 2005)
A new version of YME is out. Still no luck with CDs. Still no equalizer. It is now taking 77 MB of memory even if I am not playing anything! It does have some new features but nothing of interest to me (I do not buy songs from them). Disappointment again.

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