DiyMobileAudio.com Car Stereo Forum banner

1 - 14 of 14 Posts

Registered
Joined
3,400 Posts
Discussion Starter #1 (Edited)
Tally Ho, Champs!

So recently, ErinH's post about His New YouTube Channel inspired me to do some of my own Recording Experiments of Car Audio Systems with a pair of microphones inside a vehicle in order to try to capture at least some of the playback quality or the properties of particular car audio systems.

I had initially posted this information in Erin's thread, but felt that it detracted from his topic and goals too much, so I've moved it here. Hope you get something from it.

First off, I'll apologize for the long post ahead of time...but I need to include the necessary background info...and a bit of discussion.

DISCLAIMER: I'm not sure if I will pursue this much further. For my intents and purposes I don't really see a point to it now. But let me know if you'd like to hear different setups or mic/recording techniques?

I do think it is interesting as a reference of some sort as to what is possible, and also to potentially discuss the problems associated with trying to do this. It would be much simpler in a Home Audio environment, but there are still many caveats.

WARNING: 183MB MP3 320kbps CBR file Download...

Please LISTEN using GOOD HEADPHONES or IEMs for best results. However, these are not true Binaural recordings, so you can listen on any type of loudspeaker system, but the headphones will give you a much better representation of the soundstage & imaging. You'll want to make sure to listen on a decent system that has good imaging & soundstage reproduction, and preferably with very good low bass response.

[Download] bbfoto DIYMA: In-Car Test Recording using a 6" Spaced Pair of Microphones at the Driver's Headrest

I'm sorry that this is such a long clip! 馃槯 I wanted to include a wide variety of music as a reference, and just so there might be at least something everyone would be familiar with. Yeah, it ended up WAY too long. Skip through it at will!

The recording linked above was recorded in my buddy's "preliminary" car audio system that we just slapped together rather quickly. It's a fairly simple system, and far from ideal in MANY ways. We were in a rush just to "get it playing" with the equipment we had on hand before we ran out of time.

THE AUDIO SYSTEM:

THE CAR: It's a medium-sized SUV/hatchback. No separate trunk.

HEAD UNIT: Kenwood DDX9905s

FRONT 2-WAY COMPONENTS: Alpine Type-X SPX-17PRO 6.5" & Ring Radiator Tweeters using Passive Crossovers from a random PIONEER component set! Powered by the front channels of the HU's built-in amplifier! Passive XO's, so couldn't individually T/A midwoofers & Tweeters separately.

SPEAKER LOCATIONS: 6.5'' Midwoofers in OEM lower front door locations. Tweeters in slightly-modified OEM Sail Panels aimed ~15掳 Off-Axis to driver-side listening position.

DSP: Limited to the Head Unit X/Os, T/A, and Global 13 band Graphic EQ.

SUBWOOFERS: Four Polk Audio MM840 8" 4-ohm SVC subs, in a sealed enclosure with about 0.4cf sealed for each sub, laying horizontally across the rear cargo floor and facing forward into/under the back of the rear 2nd row seats.

SUBWOOFER AMP: Alpine PDX-F6. Each of the 4x150w channels powering One of the Subwoofers @ 4-ohms. Bypassed the amp's X/Os.

RECORDING EQUIPMENT:

FORMAT: The files were originally recorded in 16-bit/44.1kHz WAV and converted to 320kbps CBR MP3 to reduce file size. ;)

RECORDER: Zoom H6 using its XLR mic inputs & built-in mic preamps with 48v phantom power.

MICROPHONES: A pair of C.A.D. Equitek E100S super-cardioid LDC microphones. These microphones have very low self-noise, are relatively accurate, but do have a bit of upper treble presence.

I have some better equipment that is out on a rental at the moment and will try recording with it when I get it back, as it provides quite a bit better quality. It will be the Sound Devices MixPre10 II and Lewitt LCT-550 microphones.

THE "TUNE":

I only had time for one, very quick tune (if you could call it that. There was no time for microphones or measurements). And my friend wanted a tune geared towards daily driving, so it's quite bloated and thick in the midbass and bass, and the highs are boosted a bit as well.... both in order to overcome road & cabin noise for his daily drive. I covered the many other setup and tuning limitations with this install in my recorded intro.

Just like Erin's recording in his Civic with the Zoom H3-VR recorder, the actual system sounds way more precise and focused in real life compared to this recording, but you still get a good sense of the quality of the system. It is probably better if you listen on good-quality headphones if you want to compare the results to Erin's Binaural recordings. But I think that they are recorded with different goals in mind. ;)

You'll find that in the beginning (during the L/R channel verification tracks & 7 Snare Drum Beats tracks, etc), and throughout, the soundstage from the Center to the Far Right is diffuse and much less defined or focused.

You can hear how vastly different the tonality of the Pink Noise is between the left vs. right sides! This is partly due to the actual on-axis & off-axis in-car response, but also due to this microphone setup's polar response and how it is hearing the room/reflection comb filtering. I just had global EQ to work with, no independent L/R EQ to balance the L&R frequency response. :(

All of this exaggerates the problems of sitting (& recording) off-center in a small, highly-reflective enviroment. The LEFT microphone at the headrest picks up more of the direct sound from the left speakers, less of the room, and less of the right side (Inverse Square Law).

The RIGHT microphone, also positioned at the driver's headrest (LHD), also picks up quite a bit of the LEFT speakers, AND much more of the "room" reflections, which are the main cause for the right side being diffuse and without a distinct and focused far right image.

There is A LOT more "open & reflective space" on the right side of the car relative to the microphone positions, so the right mic "hears" a lot more reflections within the cabin (and destructive interference) than the Left microphone.

It was evening and was dark when I made this recording so I will set up the mics in another car and take some photos so you can see the relative positions and setup.

I might also try to record and post my home setup as well. This will eliminate nearly all of the problems of recording off-center in the highly-reflective car environment. Maybe I can do a more direct recording, and then one that captures the room interaction, as a reference to what the speakers actually produce vs. what the room contributes to what you hear. I'll try to keep that one short!

Anyway, let me know what you think (if you get through it)? !!!

P.S. Listen for the Easter Egg...you will hear "Sam" the dog barking outside of the car during one of the short solo Glockenspiel (chime/bell) tracks near the end of the clip. :)
 

Registered
Joined
185 Posts
Damn. Anyone who is into car audio better get a listen to this. HELL YEA!

Leather seats or Cloth? I prefer cloth seats for small cars and Leather for large cars acoustic wise unless it has the leather that has all those tiny micro holes so its less reflective, and more acoustically less reflective.

Windows down and windows up measurements are important to me. It's part of the reason why I like Multiple tweeters. I don't listen to my audio with the windows up often. It does change the Q of the cabin.

When I did my tests, I like to do them with the car on when doing tests if I have to audition a set since most people enjoy their systems the most while driving along. HVAC set to low fan speed. That's how I tune. How I use my system. Not some Garage queen. What's the POINT of having a top tier system and dialing it in if is not made to be used the way you normally use it.

It's these reasons why you can use 100 watts of power in a car and get away with just 50 watts at home. The sound level of the room or where you are listening.


Brave, and great job man. No kidding!
 

Registered
Joined
3,400 Posts
Discussion Starter #3 (Edited)
Damn. Anyone who is into car audio better get a listen to this. HELL YEA!

Leather seats or Cloth? I prefer cloth seats for small cars and Leather for large cars acoustic wise unless it has the leather that has all those tiny micro holes so its less reflective, and more acoustically less reflective.

Windows down and windows up measurements are important to me. It's part of the reason why I like Multiple tweeters. I don't listen to my audio with the windows up often. It does change the Q of the cabin.

When I did my tests, I like to do them with the car on when doing tests if I have to audition a set since most people enjoy their systems the most while driving along. HVAC set to low fan speed. That's how I tune. How I use my system. Not some Garage queen. What's the POINT of having a top tier system and dialing it in if is not made to be used the way you normally use it.

It's these reasons why you can use 100 watts of power in a car and get away with just 50 watts at home. The sound level of the room or where you are listening.

Brave, and great job man. No kidding!
Thanks Mickey.

There are cloth seat covers on the front seats, but otherwise the interior is leather or "pleather" most likely. ;)

Recording with windows down would be tough. The microphones would pick up way too much of the outside world and it would be very distracting to listen to and it'd muddy up the result quite a bit.

When listening "in person", our brain (with some help from our visual reference to our environment) can filter out, process, and focus on what we want or need to hear. Like picking out a single voice that's across the room in a somewhat crowded room with a lot of people talking to each other at the same time.

Even on a quiet evening, you can't imagine how much of the outside world is captured by the microphones. Even inside a closed garage. This is why recording studios exist. ;) Of course, it would depend a lot on where you are doing the recording, and the nearby environment.

Having the engine running and the HVAC fan on low would make it even more difficult to hear any nuances or articulation and focus in the system. And this is what I'd like you to be able to analyze and "pick apart".

I kind of chose to record this "flawed" or imperfect system to see if we could identify the specific issues that would need to be corrected in order to get closer to a "perfect" system.

I might record with the windows down, engine running, and HVAC fan on just so you can hear the difference. In some ways it might be interesting, as you'd most likely hear incredibly realistic sounds of jet planes traversing the sky, motorcycles, the occasional siren, street traffic, dogs barking, etc, as well as the obvious engine/exhaust and fan noise. Again, it depends on where the recording is made regarding the extraneous sounds that are picked up.

But I completely understand your M.O. in wanting to do your system tuning in your everyday, real-world, driving and listening scenario. :)

Ultimately, what I'm more interested in with my recording, is to see if people can actually pick out some of the issues in the soundstage and imaging resulting from this particular setup and its tuning limitations, beyond the obvious tonality & spectral imbalance and diffuse right side I already mentioned.

So, can we use this as a tool to get others' advice on tuning our system...what issues need to be addressed, and what changes need to be made? Or is this recording not "good enough" to reveal the problems?

Thanks again for taking the time to listen, and for your feedback. (y)
 

Registered
Joined
3,400 Posts
Discussion Starter #4
Forgot to upload a photo showing the basic microphone positions for this recording. The driver's side mic looks a little lower but it's just the pespective of the photo.
20200112_171406.jpg
 

Registered
Joined
3,400 Posts
Discussion Starter #8 (Edited)
Deleted. Further testing needed before conclusion.
.


Ha! No worries. I realize that it's a major chore just to listen to this, so I don't expect much feedback. At least you might get a few decent tracks out of it. ;)

Good headphones or IEM/earbuds will still work best to more closely replicate (but not anywhere near perfectly replicate) what you'd hear from the driver's seat.

Because of "the room" and recording technique that I used in this car, it will kind of sound like a bit of overall "room reverb" has been added to all of the tracks...as if you were listening to them "live" in a larger space.

You can try experimenting with this using the Original Tracks by downloading the free Audacity DAW software and use the "Effects" drop-down menu to apply a particular amount of Reverb, then go to "File-->Export-->Save As..." to save the file with the added reverb. Try adding more reverb to just the right side. ;)

You can also play with the L/R balance using the simple horizontal slider that's in the top left of the track window to see if that helps to more evenly balance or center the soundstage.

Because of the mic technique and limitations of the recording, it may seem to help in some areas, but will not be very effective overall IME.
 

Registered
Joined
185 Posts
Your recordings are like speed. All of a sudden, here I am fixing Magies again. Geez. It really is like a drug.
All I can say is, after doing an A/B with my headphones, I noticed TONS of problems with my Car audio system.

  • Noise in rear speaker.
  • Non matched tweeters voicing.
  • Left and right do in fact have different tone & response.
  • Vibration in areas of my car.
  • And SO ON.
I still have some Stereophile test CD's I bought, and I used to tune with that and do the A/B testing. But...
I have not done that for a LONG time. I got a way to go before I can do ANY S.Q meet ups or anything like that. Its almost depressing that I noticed all these things I did not notice before with just regular Music.


The most oddest thing I am still on the fence about is the WAV files & FLAC files seem to sound different. I am still on the fence to why. But until I can do a A/B on higher end gear? I'm going to have to wait before I can say I can hear a difference, or is it just the playback gear.


Kind of like when some people say head unit to the amp via an all digital signal till it hits the Amp DAC output sounds better then the analogue route----And you can tell? That's kind of what I am hearing I think. This may be the first time I have ever been able to really tell the difference between Formats such as WAV and 24 Bit Flac.

The stuff on Xyph.org says no. But why am I able to hear something different repeatedly? And be able to tell they sound different.
Not just Luck of the draw kind of stuff. But a real difference. Not better or bad or good. That I can't really tell. What I can tell is they are different in some way; on the same recording but Wav Vs. Flac playback from my chromebook over BLUETOOTH?

I am pretty sure I am doing something wrong. I guess I might have to purchase some Reference grade test gear after all. The only test I have the ability to do is do it digitally. While there are well outlined methods of making a Bit Perfect copy of audio from PCM on a CD to a Wav file where you can run a checksum Hash on the file and see if the file is identical----I don't know if you can do that with WAV and FLAC. I never tired it.


It really does make you appreciate what the Sound engineers of old were up to when they kept pushing that we need better Hi Fi.

Truth be told, I never experienced bad Audio till I was able to see that some of my Compact Disks were Mastered wrong.
By that I mean the Warped Tour CD. I still feel awful about getting angry at the guy by sending him an email. I mean I was wondering for weeks about replacing my gear, then then I realized it did it on ALL my playback gear. The CD was not dirty. The Playback gear was not skipping. It was just a SHIT Mastering/Transfer.

I had the same problem with SPOTIFY! And there is nowhere to Comment about the Audio tracks that I can hear a problem and provide feedback to verify with others on what you have supposedly found to verify the same error in the recording as peer review verified this. (Or the scientific method)


The real problem for me for a LONG time for me was hearing Distortion ot tweeter break up. That DAMN RECORDING WAS MADE THAT WAY!

What recording engineer does that kind of crap? It makes you realize just why I use to support Big Music labels until I realized they did that crap too!

They never made a CD player that would tell you the error rate on a CD or that there was some problem with the bits or reading of the data. That would have helped. But moreover? It made me appreciate being able to download Test files over the internet.

The only way I found out that the Warped Tour CD was crap was when I heard a MP3 copy of it I got from TPB. Even the Digital copy I bought had the same issue. WTF! In fact, TPB was my Go-To for reference quality audio files to test my playback gear I bought. Weird but true as other would comment on the quality of the tracks etc. Its one of the ONLY places where people still do this.


I would like to take this time and applaud you r efforts & say thank you BBfoto for making these reference grade recordings.
I just don't have the equipment or know how yet to verify how good these are. And as much as I hate to say it, I can't really trust my ears if it is or not. All I can trust is that they sound fantastic. Are recorded very well. And should be a tool to be used to check your own playback systems.

Meanwhile.. I seem to need to look for a reference grade playback setup. Or how the AES sets their reference. Or the ICSCA (or issca?) sets their baseline. With Digital files, I just took it for granted on playback all meeting the same standard.

I got some work to do.
Again, thanks to BBFOTO for this amazing work and set of tools.
 

Registered
Joined
3,400 Posts
Discussion Starter #10 (Edited)
Thank you for taking the time to listen and comment. :)

Some notes:

Just for clarification (and maybe I'm misunderstanding you), but the "Original Tracks" that I included are all commercial recordings not done by me. They are from the Artists & their respective Record Labels. Most of them were converted to digital files from the actual, original, purchased CDs. Most of them were converted to digital files using Exact Audio Copy software (EAC) or another reliable conversion software.

My long, 183mb MP3 "in-car" recording is just that...I played the "Original Tracks" on my friend's car stereo system and set up my microphones in the driver's seat headrest area to record and faximilate what you might hear (as good as the recording setup would allow) if you sat in this specific car and were listening to these tracks being played on his stereo system.

Regarding TPB, I would never trust ANY files that were downloaded from The Pirate Bay. You have no way of knowing their origin and source, or how they were converted, with what software, and on and on. Way too many variables to reliably trust. Unless they were original WAV or AIFF files converted directly from ORIGINAL CDs, and include a "bit perfect" Rip Log from the converter/ripping program (such as "EAC" Exact Audio Copy"), you are just guessing if they are accurate, high-quality copies, or not.

Regarding The Warped Tour recordings, I can't really comment. It could have been the FOH concert recording engineer that F'd up the levels on the original recordings at the time of the performances, or possibly the Mixing Engineer. But I don't know any Mixing or Mastering Engineer worth their salt who would allow the release of distorted material. They would soon be out of business.

Was that recording of the Warped Tour a "bootleg" recording and not an official record label release?

Regarding the quality difference between FLAC vs WAV. WAV files are not Compressed, but FLAC files are Compressed. Both files are "Lossless", meaning as far as digital bits are concerned, they should be identical when played back. And you should be able to convert a FLAC file back to WAV format, then burn it onto a blank CD disc, and it should match the original WAV file and/or original CD bit-for-bit. You can check this with the free Audacity software and many other DAW software.

HOWEVER, "FLAC" is an archive type file that is Compressed within a "container", similar to a "zip" or "rar" compressed file archive. The PLAYBACK DEVICE and its built-in software must actively "unpack" or decompress the file "on-the-fly" in real time as it is played back.

This requires additional CPU or processor power and speed from the playback device. So there is the potential for this "on-the-fly" decompression to "sound different" depending on the playback device and its "conversion" software algorithm.

Another caveat is that different streaming services such as Spotifiy, Tidal, Apple Music, Pandora, etc, all have different guidelines for mastering the files in order to submit and upload them to the music streaming service. So each service probably uses the same Source Files, but the Mastering may be slightly different. It's impossible to know for sure.

Thanks again for the enthusiasm and feedback!
 

Registered
Joined
185 Posts
Was that recording of the Warped Tour a "bootleg" recording and not an official record label release?

I still have the email. I was a REAL douchebag in my reply at first. From the Email he sent me:

On Fri, Apr 8, 2011 at 10:15 AM, Johnny B <[email protected]> wrote:
We do care about sound. That is was actually in the manufacturing process with a hair on the glass master that caused clipping of the audio. ALSO with the Warped Comp labels supply us with mastered tracks. We don鈥檛 do anything to change the quality. I am actually fairly certain that we spend more time on quality control than most other labels. Whether it be getting mastering samples from multiple engineers to find the correct one, to spending additional money having vinyl lacquers cut by hand, to spending a week with CD references and test pressings listening to the audio on multiple speaker set ups to make sure it sounds good. We are serious about audio quality and you happened to get the 1 in 1,000 copy of this that made it to retail before it could be pulled.

Respectfully,
Johnny Bouchard
Former USAF Pararescue



On 4/8/11 8:03 AM, "Imickey" <[email protected]> wrote:

In fact, its stated in the product review on Amazon.

260672




And man. Did I feel like a douchebag and still do or doing this. And this was like back in 2011. I'm glad i'm off the head meds they gave me WAY back in the day. That crap was killing me.


Also, thank you or clearing up my confusion. I thought all the tracks were played back via the microphones in the car.

I also sent a thank you again email to SideOneDummyRecords. I hope that the dude gets my email.
 
1 - 14 of 14 Posts
Top