Reference Earphones with REW and Convolver

[Ayreonaut]

If you are interested in dialing in a more perfect headphone response, then have a look at the Linkwitz site about reference headphone equalization. It's pure gold.

www.linkwitzlab.com/reference_earphones.htm

Equalizing headphones is like equalizing any other speakers, but most of the correction will be in the treble where headphones get pretty rough. Instead of using an SPL meter, you'll do it by ear. This is surprisingly possible because your hearing is much more sensitive to the treble frequencies than it is to low bass.

I use my PC as a source, and instead of building a hardware network to implement equalization, I use software to do the same thing. I recommend the free media player Foobar2000 with the Convolver DSP. (Windows Media Player will also use the Covolver DSP.) I'll walk you through the equalization process for the software.

1. Turn your headphone amp down. Then use the Room EQ Wizard Generator to listen to sine sweeps. Try a 30 second Log Sweep from 1 kHz to 20 kHz while watching the frequency display. Loop it and listen to it a few times. You should be able to identify frequencies on which treble peaks are centered.

2. Use the Room EQ Wizard EQ Filters to design an EQ curve to attenuate those treble peaks. Your first attempt will be an educated guess.

3. Export the Filters Impulse Response as WAV.

4. Install the Convolver DSP. Open your media player and configure Convolver to reference the Impulse file that you just made.

5. Export a sine sweep from a free tone generator. Listen to it with your media player. Do your filters have the right gain and width? Do you still hear peaks or do you hear dips where the peaks used to be? The sweep will sound flat when the filters are right. This will take a few iterations of adjusting the filters in REW and listening again through the media player.

[This back and forth between REW and your media player may be eliminated in the future. In a future development of REW you may be able to listen to sweeps through your filters.]

6. Now you can add wide band filters if you want to adjust the tone.

For example, listening to my Sennheiser HD 650 I identified mild peaks near 3 kHz and 5 kHz, and stronger peaks near 8 kHz and 14 kHz. I also wanted to tone down the mid-bass a little. My final filters to accomplish this were:

Filter 1: ON PK Fc 3,000.0Hz Gain -4.0dB Q 3.5
Filter 2: ON PK Fc 5,250.0Hz Gain -3.0dB Q 7.0
Filter 3: ON PK Fc 7,750.0Hz Gain -5.0dB Q 7.0
Filter 4: ON PK Fc 14,000.0Hz Gain -6.0dB Q 7.0
Filter 5: ON PK Fc 120.0Hz Gain -3.0dB Q 0.500

8. Headphone paradise. It sounds so good I can't believe it. Convolver works flawlessly.

Feel free to ask me for help if you get stuck!

[terry j]

Hi naught

not really to do with headphones as such, but how did you learn all this convolver stuff. This is the same sort of stuff used in DRC yes??

I've looked at that and my poor Pooh brain just shuts down, it seems that a (rather large) degree of computer skills are required, which I totally lack.

Is there a helpful site/instructions on this convolver/DRC stuff, as helpful and useful to idiots like me as the REW helpfiles were as useful to idiots like me???

On the question of high frequencies and headphones, I wonder how much it relates to the closeness of the driver to the ear. As we all know, high frequencies drop off much more rapidly than low, which is why we can hear the bass from the Pink Floyd concert two miles away. A speaker which is flat on axis and from a meter will not sound that way in the room, due in part to room interactions etc but also due to the natural HF dropoff with distance. Flat headphones on the other hand have no HF dropoff due to either room or distance.

So yeah, I think the idea of compensating for that is an excellent one.

[JohnM]

You can also find an extensive library of headphone response measurements on the Headroom site at www.headphone.com, those can be used to make a response file REW can import to use to derive some inital filter settings, but bear in mind that at the higher frequencies the locations of the peaks and dips depend on the shapes of our ears so the listen and adjust route is the only reliable way to get the correct settings. Applying filters within REW will certainly make all that a lot easier.

[Ayreonaut]

I don't know very much about convolver. This is the most basic thing that it does, and I just stumbled across the capability in REW.

Most of the Digital Room Correction stuff is over my head. You can learn a lot about it just by doing a Goolge search for "digital room correction" but implementing it seems very, very complicated. I'm not a computer programmer either.

All I wanted was a parametric equalizer to use with Foobar2000. Every time I went looking for one I would read in a forum that you should use Convolver. That's easier said than done, for the unlearned like me. Installing Convolver is a cinch, but it needs a "suitable impulse response generated by a tool such as DRC." I couldn't figure out how to generate that impulse response. I had been using REW for my sub, but for months I did not realize that REW could make the impulse response for Convolver. I had been sitting on the answer!

A lot of the Digital Room Correction stuff is over my head, but thanks to John's REW the parametric equalization stuff is easily within reach.

I have read that an individual's ear will affect the way that they hear treble from an transducer located so close.

I also look at the HeadRoom measurements. I found them to be relatively useful for judging overall tone and evenness.
For example my HD650 has a very smooth treble response (for a headphone) and a bit of a mid bass hump.

graphCompare.JPG

But when I listen to the HD650, I hear a different shape than I would expect from the HeadRoom graph.
Here are my filters inverted, which approximates what the uncorrected HD650 sounds like to me.

ccc.jpg

Not entirely dissimilar, but you definately have to listen for yourself.