Sunday, March 28, 2010

Equalizer settings for the 2010 Subaru Outback

This article is in response to a question on the SubaruOutback.org forum. I recently got a 2010 Subaru Outback, and its Harman-Kardon sound system includes an equalizer controllable from the multifunction display. The manual says very little about how it works, and Subaru was not much help. It includes the cryptic comment "The larger the value of Q Factor (degree of acumination) is, the more the gain of the center frequency is enhance.” (P.G. 197, 2010 Legacy/outback Navigation System, book.)". Here's what I've learned and how I've set it.

Band & Frequency: The EQ has four bands, each with a setting for Frequency, Q, and Gain. This is known as a Param
etric Equalizer, which is different from the Graphic Equalizer that many of us are more familiar with. On a Graphic EQ, there may be many more bands, but the central frequency for each band is fixed. On this Para EQ, the central frequency can be selected for each band, but there are only four of them.

In Hz, the frequency choices
are:
Band 1: 60, 80, 100, 120, 160, 200
Band 2: 250, 315, 400, 500, 630, 800, 1k
Band 3: 1.25k, 1.6k, 2k, 2.5k, 3.15k, 4k
Band 4: 5k, 6.3k, 8k, 10k, 12.5k, 16k

Gain: This is the 'boost' or 'cut' that will be applied to frequencies in the selected range.

Q: What is this mysterious setting? It determines the width of the range of frequencies to which the Gain setting will be applied. As in a Graphic EQ, a bell-shaped range of frequencies, centered on the Freq setting, will be boosted or cut. Q is inversely related to the number of octaves affected, surrounding the center frequency. Here's the relationship:

Q Octaves
0.25 4.1
0.5 2.5

1.0 1.4

2.0 0.
7

An octave is defined as the distance from a frequency to double that frequency (or downward to half of it). Look back at the Freq choices, and you'll see that it takes three steps up or down to go an octave. Since the range is centered on the Freq selected, you can think of it this way: if Q=1, the frequencies affected will be about one and a half steps on either side, both up and down. If Q=2, barely one step each way will be affected. if Q=0.5, about three steps either way. If Q=0.25, about 5 steps either way. A good depiction of this can be found here.

So back to the question: how do I get rid of that excessive booming bass? Which frequencies should I cut? By how much? And what Q should I use? This is actually a fairly tricky question. It's hard to tell frequencies by listening unless your ear is well trained. If the spans affected by multiple bands overlap, then the effects are additive (boost+boost, or boost-cut, or cut+cut). One ends up boosting or cutting the ranges that are the most out of whack, then boosting and cutting adjacent ranges to try to mitigate the side effects and get a smoothly improved frequency curve. It's very tricky, and hard to do with music alone.

I happen to have a Graphic Equalizer with a frequency spectrum analyzer and a sound generator (I used to have it installed in my home stereo system.) One can use such a device to send a "known" sound (consisting of equal amounts of all frequencies, called pink noise) through the car's sound system and see what comes out the speakers. Fortunately the Outback has an AUX input, so this is pretty easy to do. This is much more precise than fiddling blindly with EQ settings. Here's how the sound input looks before the car sound system messes with it (note that my EQ's ranges differ from the car's):
Then I pumped the pink noise through the Subaru's sound system, plugged a microphone (held at the driver's head height) into the analyzer, cranked up the volume, and here's how it looked with no correction.
You can see that there's a peak at 125 Hz and one at 4 KHz. Actually in some samples the valley between them looked much worse. The 125 Hz peak is responsible for the booming bass that the other poster and I dislike. The 4 KHz peak and the dropoff of the higher frequencies contribute to a lack of clarity of some instruments and words. (The rolloff at the top and bottom may not really be as bad as they look - I could not find my good microphone and used a cheap one that was handy, and it may not be sensitive enough for the extreme ends.)

So what to do about it? We now know which ranges the Subaru H-K sound system overemphasizes, but futzing with the screen to set them is tedious at best. As mentioned above, tweaking a Freq actually tweaks its neighbors, so choosing a good set of settings r
equires solving several equations with many unknowns. I wrote a spreadsheet many years ago to do that math, but I can't find it now, so I hand-equalized it using the 10 ranges on my external EQ. Here are the settings I chose.

This may look kind of "all over the map", but if you draw a bell curve around each setting, and add them up, it becomes a smooth correction curve.

When I turn on the pink noise, apply the external EQ settings, and capture the sound with the mic, the results are not half bad. There's still a dropoff at the top and bottom, but that might be the mic. This sample still shows some peaks, and loss of the 63 Hz range, but some samples were quite a bit flatter, and it sounds less boomy already.

Now we need to translate this to the H-K EQ settings, with only four Freq bands available but a variable band width (the Q). My strategy is to use as narrow a range as possible for the problem bands , so I started with a Q of 2. For the peaks we need to seriously cut, I chose:

Band 1: Freq=125, Gain=-5
Band 3: Freq=4k, Gain=-5

To offset the side affects and level out the middle, I chose Band 2: Freq=500, Gain=2.
I'm not sure what's happening with the top end (music sounded OK to the ear), so I chose Band 4: Freq=12.5K, Gain=0, in effect doing nothing at the moment.

When I turn on the pink noise, apply the para EQ settings, and capture the sound with the mic, the results are pretty flat - which is what we want!

Now I switched to music instead of pink noise to see how it sounded. The first thing up on my iPod was "Listen to the Music" by the Doobie Brothers, which sounded like excellent advice! Never having worked with a Parametric EQ before, I played around with getting the low end flatter. I switched Band 1 from 125 down to 80 and even 60, and spread the range out by using a Q of .25. I had to cut the Gain as far down as -9 to get rid of the booming bass and make it sound like a real drum. I didn't write down any more results from the analyzer (music is much more dynamic than pink noise), but I could tell from the display that it was much more balanced.

The H-K sound system has different EQ settings for each audio source, so I had to go enter the settings into each one. I began to notice differences right away:
  • FM radio didn't sound as clear. Well, radio transmission does not have the same fidelity as a digital source, so that made sense. I had to boost the top end quite a lot to get clarity. (Remember I said the top end sounded OK to the ear? That was probably with digital sources.) Settings:
    Band 1: Freq=80, Q=.25, Gain=-9
    Band 2: Freq=500, Q=2, Gain=3
    Band 3: Freq=4k, Q=2, Gain=-3
    Band 4: Freq=125, Q=2, Gain=7

  • iPod, XM Satellite Radio, and CD were pretty similar to each other, being all digital sources, except the top end.
Now, this was all done in my driveway, with no road noise, so it was time to hit the freeway. You can't adjust the EQ settings when the car is in Drive, you can only switch between Default and Presets. So I stopped a few times to make adjustments. The bass was much improved. But the high end was very harsh with digital sources, almost painful. By experimenting, I settled on Band 4: Freq=16k, Q=.25, Gain=-3. In other words, lower a broad range of the top end, but only by -3. I think this confirms my suspicion about the quality of the mic I used for the measurements: it had poor high-frequency response, misleading me to think I needed to boost the top end, when really I needed to cut it a bit. (The mic was from a home karaoke machine, so since it is for picking up human voice, it doesn't need to be good in the upper ranges.) To summarize the settings for digital sources:

Band 1: Freq=80, Q=.25, Gain=-9
Band 2: Freq=500, Q=2, Gain=3
Band 3: Freq=4k, Q=2, Gain=-3

Band 4: Freq=16k, Q=.25, Gain=-3

So I cut the top end for all the digital sources, and now it sounds pretty darn good! I played several songs from my iPod that I know very well, and found some familiar tunes on the XM, so I'm pretty happy. I won't be able to listen in detail for a while - my wife is taking the car on a weeklong trip - but I look forward to hearing the results in the future, and will probably do some more tweaking. Maybe I can record pink noise onto my iPod and a CD, so I can analyze them in more detail. And I need to find my good mic!

This is quite a long post, probably much more than the forum posters were looking for. But I wanted to show the process one goes through to actually analyze the system and what I learned about choosing the parameters for a Parametric Equalizer. It's not a simple process without a frequency analyzer!

20 comments:

  1. I think the car manufacturers should give a brief information how to install a sound system in their car model.

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  2. Excellent article. I have been tweaking the EQ on the HK and still haven't found an adequate mix. I will try yours as a start to see where it leads.

    BTW - the "hack" on the NAV system is pretty easy, and frees up the system tremendously. I downloaded the steps from the OB forum and had a local shop do it for $40.... You could then tweak on the road.

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  3. Great post, can't wait for my OB to arrive so that I can try them out. Thank you!

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  4. As someone in the Forum commented, I believe this info is good if you have the NAV system, but for those of us with the SAME stereo and no NAV, is it possible to use any of your info? I think the system without NAV has many EQ choices, like Acoustic, Voice, etc, so which one of these would perform the best 'fit'?

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  5. many thanks for an excellent post - just helped me out in trying to get to grips with my equalizer on a Liberty - Subaru's manual less than helpful. Thanks Roger.

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  6. After many tuning sessions without any satisfaction and zero guidance from subaru, I found this post and glad I did. You saved me a bunch of money as I was going to get some upgrades. Thanks as I found your settings in line with my taste. I'll live with the HK system for now. Bob

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  7. Hey Roger

    Do you have any updated settings for this. It is a 1000 x's better using your settings but something is still a lacking. It could be that I am tone deaf! lol

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  8. Not really, I think I may have taken down the high end a bit. I have noticed that there is some variety in frequency balance between CDs. Some older tracks ripped from cheap compilation CDs can be thin and harsh on the top end. I did not want to take down the top end too much just for those few, so I just have to tolerate them. It would be possible to create a different preset for those, but then I'd be switching back and forth by song... not worth it.

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    Replies
    1. Great! It is still way better. Take care.

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  9. Hey Roger, the Premium Legacies which do not have Navi or HK Radios, offer a only Bass, Mid Range and Treble controls on the stock HUs. I replaced the stock speakers with Alpines 601 series (components in front, coaxials in the rear). I also added Subaru's Sub woofer (really not worth it). Maybe you have some "secret" mix to eliminate the boomy bass notes even with the new speakers. It's better, but my audio guy says that the HU needs need to replaced. Then I will hear a big difference. The stock HU offers standard settings, CS 1 and CS 2. CS= Center stage - which is a sort of equalization or phoney surround gimmick. I am able to get to sweet spots but if I change the audio sources : FM radio to CD or worse iPod (that seems the tiniest with way too much Treble), I lose the sweet spots and need to keep varying the controls. I hate that. BTW, the stock radios in the Subbies SUX.

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  10. Hi Roger - Thanks for the tips here. What's your opinion of the fader (front/back)? In your car, is the rear speaker output almost non-existent?

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    Replies
    1. No, my rear speakers seem to work fine, and the fader works. I keep the rear up a notch or two, but nothing extreme. Maybe your unit's amp is a little weak on on the rear channels -if it's under warranty have Subaru check it out.

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  11. Hi Roger. I've just gotten my 2014 Forester with HK Nav and Amp. My HK Equilizer screen shows a lot more than 4 bands. I think it shows 8 or 10. Could you give me a some figures to set each one at for its optimum settings. I know these settings are subjective but I'm a real idiot when it comes to these things.

    I'd really appreciate your help.

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    Replies
    1. Actually it has 7 bands -

      50, 160, 400, 1k, 2.5k, 6.3k, 12.5k

      Thanks again

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  12. Hi Roger. I've just gotten my 2014 Forester with HK Nav and Amp. My HK Equilizer screen shows a lot more than 4 bands. I think it shows 8 or 10. Could you give me a some figures to set each one at for its optimum settings. I know these settings are subjective but I'm a real idiot when it comes to these things.

    I'd really appreciate your help.

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  13. My 2014 Forester HK Equalizer has a lot more than 4 bands and I have no idea how to configure them for optimum sound. Could you help me out with that please?

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  14. Hey J-Me..
    Any word back from Roger. I'm in the same boat with my 2014 XT

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    Replies
    1. Not yet. See below he makes some suggestions and has promised to get back to us. I'm looking forward to it.

      Enjoying the XT though :D

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    2. Not yet. See below he does make some suggestions and promises to get back to us with more. Looking forward to it.

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  15. Since I don't have that EQ or its manual, I don't have any specific suggestions. I have been thinking about this and have a few ideas.

    1. If it has 8-10 bands, you could set the Q pretty narrow (a big number like 2.0) and the parametric EQ would behave much like a Graphic EQ. You could then set each band to what you think is needed. In my article above, the Graphic EQ has 10 bands.

    2. I have written a new Graphic EQ simulator - I mentioned in the article that I had written one years ago (I'm a programmer) but could not find it. I've been very busy with family activities this spring, so it's not quite finished. When I get it finished, I will make it available for download. I have envisioned how I would put a Parametric EQ screen in front of it, which will enable us to simulate these HK EQ's. Now that you've pointed out that the new ones have 8 to 10 bands, I'll make it flexible enough to handle that many,

    3. How can we measure the frequency response of a car, so we know what to correct, since most people don't have frequency analyzing EQ's? I have looked on the Internet and have found freeware frequency analyzing software. One of these programs on a laptop (I'm on a MacBook), with a good microphone, would enable us to take measurements. I have not tried any of these yet, but they are not hard to find by Googling. Heck, one of them might have an EQ simulator which would obviate the need for the one I'm writing.

    Thanks for the interest. I do plan to get back to this topic when the family stuff settles down. In the meantime, if you find useful software or develop some good HK EQ settings, please comment again.

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