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      11-28-2016, 06:53 PM   #1
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F30 335i HK System mic'd, measured and EQ'd

Ever since I bought my 2014 335i over a year ago I've always wanted to take one of my Smaart rigs out to take some measurements/tune my car. Well I've been on tour now stop in this last year and never really had the time. Today I got bored and I decided to go out to my car take some quick measurements and see what's really going on...

Equipment used:

Lenovo x230t running windows 7
Smaart 8
Smaart iO
Isemcon EMX-7150 mic with calibration file

Car volume at half.

Mic was put in a clip and attached to the headrest approximately wear my head would be. Pink noise was generated from Smaart to use as a reference, split and fed into the car's stereo via the aux 3.5mm input.

Here is a trace with the EQ flat and L7 on. If you ever wondered why it sounded phasey, thin and odd... It's because it's exactly that. It's a great example of what happens and the challenges faced when adding more speakers into the mix.



Here is a trace with L7 turned off and the EQ still flat. I had it overlap the L7 trace so you can compare the difference. As you can see phase is improved and so is frequency response as a result. No, I'm not digging any deeper here as to what exactly L7 is doing, so deal with it. Frankly, I just don't have that kind of control over the factory system. The green line is L7 off and pink is L7 on.



Now here is the trace of the system with the limited EQ that is available on the F30 335i SEDAN HK system. Keep in mind, this is about the response I am going for with subwoofers in a large format concert PA system. The low mid 100-250hz region is really content and mix dependent. I will probably mess with the 200hz a bit as I listen to it more. That being said, I will probably adjust the "bass" a bit as well.



To achieve all of this my settings were as follows: (Newest settings at bottom of post)

Bass +5
Treble +2

100hz +3
200hz -3
500hz -4
1khz +4
2khz -4
5khz +3
10khz -2




I listened to a variety of music from CD after to verify. The CD's ranged from:

Jennifer Warnes - "The Hunter"
Norah Jones - "Come Away With Me"
Gojira - "l'Enfant Sauvage"
Modest Mouse - "We Were Dead Before The Ship Even Sank"

I found myself adjusting the bass for each, but will finally settle on something I'm sure.

**EDITED**

Went back out to the car today and took some better measurements and have a few more things to share. I ended up listening to about 20 more CD's as well and think I've settled on some settings. I'm sure I will end up constantly adjusting things though... All measurements and EQ'ing done today were with the car's volume 1/2 way up (THIS IS IPORTANT). I generally listen to my stereo at 1/2 so that's why I chose this volume. I also discovered there is about 34ms of delay in the stereo from input to microphone. I don't know whats going on under the hood but that is a ton.

Here we have a new trace of the EQ flat and L7 on.



Here is the new trace with EQ flat and L7 off. As you can see, the phase response is greatly improved.



Now the two overlaying one another. L7 on being red and L7 off being blue.



Here are is the new tune with the old. New being blue and old being red.



Now with some smoothing applied. New is blue and old is red.

]

Have you ever wondered why the stereo seems like it sounds completely different at different volumes? It's because it actually does. These next measurements were taken at 1/4, 1/2 and 3/4 volume. The phase shift from the different volumes/EQ is pretty normal.

**EDITED**
Apparently BMW does use their own sort of loudness curve for the different volumes. This feature drives me a little crazy. I find myself constantly grabbing the bass knob and turning it down at lower listening levels. Personally I think it still does a pretty poor job... Thank you to Integral Audio for clarifying this!

The orange is 1/4 and blue is 1/2.



Now here is 1/2 compared to 3/4. 1/2 is blue and 3/4 green.



All three.



All three with some smoothing.



**MORE EDITS**

Because Integra Audio brought some very good points to the table I felt like going back out to the car for more measurements...

Due to the simplistic nature of what I am doing, the lack of any sort of jig to hold mics (for consistency) and being limited to only a quad matched set of microphones, everything done below are single microphone measurements for demonstration. If I were to actually be designing a system for the vehicle, I do not believe I could get away with anything less than 4-8 microphones. I would essentially position them 2-4 per a side of the headrest, simulation where the ears would be located and at different heights for different listening levels for people of varying heights. Where you actually place this as far as distance from the steering wheel is a whole other decision. I feel as though with a set up as such you would be able to make more educated decisions as to phase, timing, delay, EQ, etc. Making these decisions inside of a vehicle is nothing but give and take and compromise. I do not envy anyone who wants to design car audio systems for a living. For everything I did above, I centered the microphone about where the center of my head would be to give me some sort of balance between what is happening on the left side of my head to the right. If I had any more control of or had anything other than the simple EQ available to me in the car, I would done multiple measurements and averaging to start. For my purposes, I did not deem it necessary.

Here we have 6 measurements of the HK system FLAT with no EQ and L7 OFF. 3 of which were done at the bottom of my headrest, left, center and right, and 3 were done at the top of my headrest, left, center and right. All of these measurements were done only a few inches from one another, but look at how different they vary!!! Time was reset for each measurement, of course, and smoothing is at 1/12 Octave.



Below is an average of the result of the above with 1/3 octave smoothing.



Here is an overlap of the initial measurement in blue and our new average in yellow. As you can see they are very similar, but definitely do differ! This is exactly why Integra Audio is 100% correct in saying that a measurement that is corrected in one particular area, will be very wrong in another. 1/3 octave smoothing has been applied here.



A comparison between the initial in blue and the new in yellow with octave smoothing applied.



Here we have the same 6 measurements, but with the tune I applied to the system. 1/12 octave smoothing here.



Now here is the tuned average with 1/3 octave smoothing.



A comparison of the initial tune measurement in blue and the new average in green. Again, looking similar, but they definitely differ! 1/3 octave smoothing here.



Here are the same to compare, but with octave smoothing applied.



Here is a comparison of the two new averages we just did. The factory HK system FLAT with no EQ is yellow and the new tuned version is green. 1/3 octave smoothing.



Here are the same two with octave smoothing.



Just for fun, here is a comparison of a target curve for an engineer I work with regularly in the concert world. Now his curve is just that of a 3 system with low, mids and highs, but no subwoofers. Very similar and it is no accident that my ears wanted to hear same 18dB difference between 60hz and 1khz here. Also of mention you'll notice his curve has quite a bit less, 200-500hz in it. This target curve is dedicated for arenas and in such a reverberant space, a lot of that body that is missing comes from the room. Quite different from what's happening inside of our cars. Dealing with ~80 open microphones on stage presents another set of challenges as well.



**EDITED**

Now some of you may ask, "what about with L7 on?". Here you go!

L7 on with no EQ is purple while the EQ I applied is green. There's a touch more low end in it than I wanted, but with the car'a factory EQ, I compromised.



Smoothed out.



Here are both of my tunes on top of one another. L7 ON is green while L7 OFF is yellow.



Smoothed out.



That's all for now. Thanks for taking a look!

My newest Logic 7 OFF EQ settings are:

Bass +2
Treble +1

100hz +4
200hz -2
500hz -4
1khz +5
2khz -5
5khz +3
10khz -1

My newest Logic 7 ON EQ settings are:

Bass flat
Treble +1

100 +7
200 -6
500 -4
1k +5
2k -4
5k +2
10k -1

The fun part about this is, sound is VERY subjective. Just because one person finds one setting pleasing, the very setting can be overwhelming for another. In no way shape or form am I saying this is the end all be all. Have fun with it and mess around. See what works best for you!

Comments are welcome. Thanks.

Last edited by HKD126; 12-02-2016 at 04:00 PM..
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      11-28-2016, 08:45 PM   #2
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Nicely done! I actually thought about doing the same thing with REW. There are some crazy advances being made in DSP right now.
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      11-29-2016, 12:00 AM   #3
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Wow, the coherence is crazy above 1500 Hz, and the phase curve as well, but I would think that multiple arrivals in time do contribute to some of the mess there (look at the live IR)! Otherwise, what you did looks much better considering what tonal controls you have to work with. You have to wonder what the HK folk did "under the hood" in the factory processor/amp that is doing more harm than good?

I'm hoping for some good weather this week to measure and optimize my factory system (hifi 676 here, with Bimmertech Amp/DSP and factory audio system) to get by until I get a chance to upgrade my speakers next year. Not happy with the settings I downloaded from the site, but I was pressed for time with these shorter days. Looks like they used every control on the 31 band eq, eek!!! As the saying goes... less is more.

So when are you going to get that external DSP/AMP and MOST adapter happening in your car? I suspect that you're feeling a bit handicapped with that 7 band eq, kinda a throwback to the good old days of 10 channel powered mixers with built in eq!! I know, I know, I'm good at spending other people's money!!!

Cheers!

Arthur
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      11-29-2016, 05:36 AM   #4
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Quote:
Originally Posted by Arthurrs View Post
Wow, the coherence is crazy above 1500 Hz, and the phase curve as well, but I would think that multiple arrivals in time do contribute to some of the mess there (look at the live IR)! Otherwise, what you did looks much better considering what tonal controls you have to work with. You have to wonder what the HK folk did "under the hood" in the factory processor/amp that is doing more harm than good?

I'm hoping for some good weather this week to measure and optimize my factory system (hifi 676 here, with Bimmertech Amp/DSP and factory audio system) to get by until I get a chance to upgrade my speakers next year. Not happy with the settings I downloaded from the site, but I was pressed for time with these shorter days. Looks like they used every control on the 31 band eq, eek!!! As the saying goes... less is more.

So when are you going to get that external DSP/AMP and MOST adapter happening in your car? I suspect that you're feeling a bit handicapped with that 7 band eq, kinda a throwback to the good old days of 10 channel powered mixers with built in eq!! I know, I know, I'm good at spending other people's money!!!

Cheers!

Arthur
Arthur,

If you get the chance, I'd be quite interested in seeing what you come up with for the Hifi system.

I've been toying around with the idea of going with MusicarNW 3 way system, but would like to play around with this quite a bit more. I definitely would like to take some more measurements, averages and do a bunch more listening. That and I need to stop purchasing performance goodies for the car...

Thanks for commenting and taking a look!
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      11-29-2016, 09:17 AM   #5
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This is awesome. Thank you for doing this. I turned off L7 the day I got my car, I thought it made everything sound even more muddled than the system already does. After a lot of tinkering, my settings are not far off from yours but I still feel it sounds a little thin on the highs and muddled mid-bass.
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      11-29-2016, 09:35 AM   #6
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I'm not wild about the hump at 40Hz, although that's a matter of taste. It's caused by the bass tone control, because it's a shelving filter. I'd reduce the bass to pull that hump down, then increase the 100Hz EQ if it sounds thin. One thing you're not seeing in the chart is the subs struggling to handle content below 40Hz. It's not on the chart, because the subs are rolling off response, but unless they're high passed (who knows? Maybe they are.) whatever content that is down there they'll try to reproduce, resulting in long cone excursion and high THD as a result.
As to the phase plot, I wouldn't even look at it. You'll go nuts trying to make it better, while for all intents and purposes you can't hear it anyway. Phase only matters when the outputs of two or more drivers arrive at the listening position at or close to 180 degrees apart, and when that happens you'll see it on your SPL chart as a deep notch in the response.
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      11-29-2016, 10:15 AM   #7
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The response you see is the result of a 3 way system that has been set up to recreate that of a 4 way. You are right about the woofers. As a result the body of the system from 100-200hz is severely lacking. With such broad filters and limited EQ the only way to bring that up, brings a whole lot of unwanted tones with it. Tuning a full range system I generally go with a 15-18dB difference from 60hz-1khz. I went a little bit more on this though....

As far as the phase plot, I would look at it. My point was that with the L7 turned on, there were phase issues and as a result you were seeing massive dips at the 125hz, 550hz and the 1.5khz region.

This was just me playing around in the car for 30 minutes. I have more time today and will go back out to do more measurements, averages and different EQ. I'll report back with what I come up with.

Last edited by HKD126; 11-29-2016 at 04:54 PM..
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      11-29-2016, 10:50 AM   #8
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Quote:
Originally Posted by HKD126 View Post
I generally go with a 15-18dB difference from 60hz-1khz.
Call me old school, but +/-3dB still does it for me.

Quote:
there were phase issues and as a result you were seeing massive dips at the 125hz, 550hz and the 1.5khz region.
I don't see any 'massive' dips, which would be at least 18dB deep to qualify as massive. It's not usual for phase sourced cancellation notches to be even 24dB deep. Phase sourced cancellation notches also tend to be no more than 1/12 octave wide.
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      11-29-2016, 11:17 AM   #9
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Between the L7 on and off, the 6db difference at ~130hz, 5db at 550hz and the 4db at 1.5k are substantial. All I'm saying is this is a direct result in the phase coherency and time arrivals of the sources. Not only can you see it on the graph, it is very apparent to the ear. At each one of those points it's essentially double the output with it off. Waveforms do not need to only be 180* out of phase to affected. The slightest shift in phase affects summation and cancellation between two waveforms.

I'm about to go back out to the garage for more tinkering.
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      11-29-2016, 12:01 PM   #10
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Great work - I look forward to your final results and settings.
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      11-29-2016, 01:44 PM   #11
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More results posted.
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      11-29-2016, 02:12 PM   #12
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Fascinating! Would you say they're doing a bit of dynamic equalization with the changing curve according to output level to mimic our perception of high and low frequencies at different SPL levels? Seems like this is a moving target. Now you got my curiousity with regards to what happens with the hifi version of the car audio system and whether it does the same thing. Got another report to finish up before I can run outside and fiddle with the car, hopefully I have a bit of time before the sun sets and the rain starts....
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      11-29-2016, 02:22 PM   #13
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I do not believe the change in frequency response is intentional. If it were, it would tend to want to go the other way, would it not? Meaning, at lower volumes you'd want to accentuate the highs and tame the lows and the opposite at higher volumes. With my current settings, when listening quietly I definitely need to pull the "bass" control down for everything else to keep up. At 3/4 volume the highs tend to taper off around 4khz which makes it a bit more bearable to listen to.
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      11-29-2016, 02:28 PM   #14
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Ok, maybe I couldn't tell the different colours of the curves apart to know which one is which. So to be clear, at lower volumes it increases the level of the high and low frequencies, and at higher volumes it "flattens" out the frequency response? And of course, what happens when you're driving and you start to get the contribution of road and engine noise to the mix? Does it simply increase or decrease the overall level, or does it do some kind of frequency shaping as well? I guess I need to figure out a way to drive and handle my Smaart rig at the same time!! Shh, don't tell anyone!
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      11-29-2016, 02:32 PM   #15
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At lower volumes it increases the lows and decreases the high. Higher volumes decrease both.

I haven't done any driving with these settings yet... I've only been playing with it in the garage.
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      11-29-2016, 02:46 PM   #16
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Quote:
Originally Posted by HKD126 View Post
At lower volumes it increases the lows and decreases the high. Higher volumes decrease both.
That indeed seems to be odd behaviour, I would expect both lows and highs to increase a bit at lower volume levels, and both to decrease at higher volume levels. The big implication here is at what level do you want to try to equalize the system for greatest consistency? Furthermore, if you compensate for too much low frequency information at lower volume levels, then when you crank it up, you'll find it lacking in low frequency response! I'd go nuts!!

https://en.wikipedia.org/wiki/Fletch...3Munson_curves
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      11-29-2016, 02:49 PM   #17
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Everything I did was with the car at 1/2 volume as that's where I do my most listening.
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      11-29-2016, 03:07 PM   #18
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SO... I just tried out your latest settings in a quick ride around and have to say that sound quality is better. Thank you for doing the leg work on this.
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      11-29-2016, 03:51 PM   #19
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Quote:
Originally Posted by HKD126 View Post
Waveforms do not need to only be 180* out of phase to affected. The slightest shift in phase affects summation and cancellation between two waveforms.
You might want to have a gander at the homepage in my profile. Most of what you're seeing is related to the position of the mic in the car.
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      11-29-2016, 04:14 PM   #20
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Quote:
Originally Posted by Billfitz View Post
You might want to have a gander at the homepage in my profile. Most of what you're seeing is related to the position of the mic in the car.
Actually the FFT analyzer we are using here delays the reference channel to compensate for propagation delay related to the position of the mic vs source. However when you have multiple sources that are not aligned (typical car stereo situation, pick ONE point for perfect alignment, move the mic even a few inches away and now you have misalignment), a phase difference between 120 and 240 degrees between two sources at a certain frequency spells trouble in the overlap area depending at the wavelength that the alignment delta falls into. Car stereo speaker system configuration is a whole basket full of compromise, give and take everywhere. Fun propeller head stuff!
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      11-29-2016, 05:09 PM   #21
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Quote:
Originally Posted by Arthurrs View Post
Actually the FFT analyzer we are using here delays the reference channel to compensate for propagation delay related to the position of the mic vs source. However when you have multiple sources that are not aligned (typical car stereo situation, pick ONE point for perfect alignment, move the mic even a few inches away and now you have misalignment), a phase difference between 120 and 240 degrees between two sources at a certain frequency spells trouble in the overlap area depending at the wavelength that the alignment delta falls into. Car stereo speaker system configuration is a whole basket full of compromise, give and take everywhere. Fun propeller head stuff!
Exactly what Arthur said. My measurements were simply used as a reference to get an idea of what was happening in order to create this thread for others to view. Between the multiple sources, arrival times, reflections, and everything else that is going on inside the car, I understand that because these measurements were taken in a certain spot, doesn't mean it's going to be the same a few inches over. Hell, most people aren't going to care or understand most of what was discussed and just want to know what EQ I settled with. That's why I kept it simple.

To be frank, I don't think my previous EQ was vary far from this at all. Maybe a click here and there. At the end of all of this I still referenced music I know, tune other systems with and used my ears.
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      11-29-2016, 07:26 PM   #22
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EDIT: Apologies to Artherss, who already brought up equal loudness contours...

Really commendable work. I wish everyone were as into empirical data as you folks are. Seriously, would certainly make my life easier. You said "comments welcome", so I'll throw in a couple. Hopefully they are welcome.

On the measurements:
We've spent years trying to figure out in-vehicle measurement. It is an understatement to say that it is really, really hard. So much harder than it seems like it should be, and exponentially harder than home or commercial/pro reproduction environments. I can tell you that the single mic measurements you've taken above aren't going to give you the accuracy that you're used to from your far field measurements in concert venues. Taken alone they won't even remotely give you usable data. Unlike the environments you're used to, a vehicle cabin is highly reflective and diffuse, but not reverberant. There's no such thing as a T60 (or even T30) measurement for a vehicle.

At a bare minimum you'll need to take multiple measurements and average them. You need to average only magnitude response, you can't simply sum the complex measurement (or the mic outputs). Without a controlled array, you'll need to take about 12 measurements within a couple inches of each other, all within the ear ellipsoid.

Take a look at this:

View post on imgur.com



Those are unfiltered measurements of a midrange driver in-vehicle. Same driver, same vehicle, same stimulus. Here's a closer look at just two of the measurements, to clear out the clutter:
View post on imgur.com


Note the left hand scale - the difference from one measurement to the other is greater than 10dB for a huge portion of the in-band range of this driver, and the peak-to-peak swing is nearly 20dB. Just for reference, 20dB is the difference between 1W and 100W! And 10dB is what we perceive as a doubling of loudness. So which measurement is right? They both are, and they're both wrong. But if you used any of those single mic measurements to evaluate a system or apply EQ you'd get really, really wrong results.


On the frequency boosting: What you are seeing is correct - they do boost lows and highs at lower volume levels. We've seen it on every BMW/MINI unit we've tested. It's their version of a loudness contour (the older among us may remember a "loudness" button on older home receivers and such). Take a look at this:

View post on imgur.com


That's the HU electrical output at low (blue), medium (green), and high (red) volumes. Loudness buttons/effects are based on the Fletcher-Munson curves. Our ears do not hear linearly - our sensitivity to low and to a lesser extent high frequencies decreases with decreasing SPL. The Fletcher-Munson curves look like this:

View post on imgur.com


Note the compression at the low and high ends. This is compounded in a vehicle by the masking of lower frequency sounds by road noise and vibration when driving. You can see from the first graph that the boost is significant - 12dB+ at around 60Hz. And if anyone is wondering, yes, this is with all tone controls flat.

Anyway, this is not meant as criticism, hopefully it isn't taken as such. Really great work on this.
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