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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > 2011 base E90 audio signal



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      06-09-2010, 11:25 AM   #1
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2011 base E90 audio signal

So I got a 2011 E90 with base audio as a service loaner yesterday (my 2007 E91 has a broken motor mount!?!)

Here are the measurements of the head unit's output:

Front



Rear



Front door only (after the capacitor)



You guys see why I keep saying, don't just add speakers and an amp to 2010+ base audio?

That front roller-coaster signal curve should be a flat line!

There's no way to make good speakers sound good sending them signal like that.

If all you want is boom and sizzle, that's it, but vocals would be nice, don'tcha think?


This is why I keep saying, you need some sort of signal-de-processor, or you need HU recoding.
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      06-09-2010, 11:43 AM   #2
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and how to go about that? BTW: nice info!
But do not forget: the HU is tuned to this sound curve for a reason - to sound "good" in the end. It actually says something like "acoustics matched to the car" in the product descirption.
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      06-09-2010, 11:54 AM   #3
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Quote:
Originally Posted by BMW-NC View Post
and how to go about that? BTW: nice info!
But do not forget: the HU is tuned to this sound curve for a reason - to sound "good" in the end. It actually says something like "acoustics matched to the car" in the product descirption.
It means they can make it sound decent while using cheaper equipment kind of like what Bose does. Now when you have good equipment that can sound good on its own, the pre-processing kind of screws you up because you end up having to undo what they did.
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      06-09-2010, 12:28 PM   #4
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Quote:
Originally Posted by BMW-NC View Post
and how to go about that?
With an autologic or other ways...

Quote:
Originally Posted by BMW-NC View Post
But do not forget: the HU is tuned to this sound curve for a reason - to sound "good" in the end. It actually says something like "acoustics matched to the car" in the product descirption.

But that's not accurate. IT would be nice if it were accurate, but in practice, it's not. It doesn't sound good in the end. We have many 2010 and 2011 "base-audio" owners complaining about the sound.

It is not tuned to the vehicle acoustics as much as it is tuned to the crappy speakers in the car. Even if we agree that there are some components to this tune that are cabin-dependent, the fact that there are no tweeters in the car and crappy 6" woofers mean that this curve will sound HORRIBLE once any kind of tweeters, or better woofers with decent amplification, are added.

If you use a flat signal (like in a car coded to HiFi) and you add nice mids and tweets and woofers and amplification, the result is pretty darned good (much better than stock), even without any vehicle dependent tuning at all. This means that most of that tuning is NOT vehicle dependent, but speaker dependent.
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      06-09-2010, 01:49 PM   #5
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My time with 2010 328i loaner with the Stereo system tells me that somehow the OEM Alpine upgrade amp must be either reversing that curve or shaping it into something else if actually it is an upgrade. Because this Stereo system is really a poor sounding system to me, no matter the source.
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      06-09-2010, 02:18 PM   #6
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Quote:
Originally Posted by Technic View Post
My time with 2010 328i loaner with the Stereo system tells me that somehow the OEM Alpine upgrade amp must be either reversing that curve or shaping it into something else if actually it is an upgrade. Because this Stereo system is really a poor sounding system to me, no matter the source.
The 4" in the door are really bad looking, too. Much cheaper in appearance than the HiFi 4"...
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      08-08-2010, 12:19 AM   #7
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Quote:
Originally Posted by Technic View Post
My time with 2010 328i loaner with the Stereo system tells me that somehow the OEM Alpine upgrade amp must be either reversing that curve or shaping it into something else if actually it is an upgrade. Because this Stereo system is really a poor sounding system to me, no matter the source.
Apologies in advance for bumping this thread, but I missed it until tonight after scouring through posts and others with the 2010 stereo system could benefit from VP E's work.

I somewhat doubt the OEM Alpine upgrade amp reverses or corrects this curve. The kit only includes replacement door drivers and door-sill tweeters, leaving the 6" drivers under the seats in place, albeit with amplification.

rkm3 installed this kit in his 2010 earlier this year while adding Logic7 subs to his car at the same time-- he reported that it sounded "bloated" in midbass response and the tweeters were brighter than expected. The kit will work for someone who tends to listen to systems with the treble and bass controls jacked but it doesn't exhibit proper balance. I can't verify this without an RTA anyhow but figure that most are better off by recoding to HiFi output with some form of external EQ/DSP device and an amplifier.
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      08-08-2010, 01:12 AM   #8
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Quote:
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,,, but figure that most are better off by recoding to HiFi output with some form of external EQ/DSP device and an amplifier.
One or the other.

If you have a DSP device, recoding is not required - the signal can be normalized (either automatically or through manual adjustment). The DC amplifier can be set to completely flatte the OEM programming, if one has an RTA with line inputs...

If you recode to HiFi, DSP is only useful to optimize the acoustic response, but the recode turns off the HU processing and makes it flat and unprocessed.
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      08-08-2010, 01:58 AM   #9
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I guess I was getting ahead of the context by implying that recoding to HiFi + adding an EQ/DSP processor allows you to "tune" for flat response with the inclusion of aftermarket components, where third-party drivers have different response characteristics.

This is desirable in a situation where the midbass drivers are replaced with SWS-8s while using a _____ component system in the doors. The levels among these channels can be adjusted with gain controls on the amplifier(s) and internal crossovers can help them blend better but tuning the system with an EQ/DSP device would take it a step further.

You know these cars and components better than anyone here, so I defer to you. With upgraded third-party speakers and a recode to HiFi, is a customer missing out on anything significant by driving everything with an amplifier that only offers crossover and gain adjustments?
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      08-08-2010, 11:34 AM   #10
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Quote:
Originally Posted by Imperator View Post

You know these cars and components better than anyone here, so I defer to you. With upgraded third-party speakers and a recode to HiFi, is a customer missing out on anything significant by driving everything with an amplifier that only offers crossover and gain adjustments?
We all have our areas of expertise, but thanks for the kind words.

If you can recode the unit to HiFi, you have essentially made the output identical from an audio POV to an aftermarket HU.

So from that point of view, you don't need DSP.

There is another school of thought - that DSP compensated for cabin acoustics, and to some degree for driver limitations, so dramatically - and the cost is now so low - that any upgrade should try to take advantage of it.

Using DSP properly also obviates the need for recoding, and I am yet to be convinced that recoding is easily accessible to most vehicle owners. I doubt that US dealers will deliver it on request, and Audiologic seems to be quite a project to find and to make work. I am eager to learn more about the vendors offering recode services and their success at this.
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      08-08-2010, 11:44 AM   #11
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You're right, but I hope the remote coding services allow more enthusiasts to get this feature with greater ease. There are plenty of Autologic providers in my area, with most charging $95 for this service, but they don't know what they're doing. I could walk them through the process on my car if I knew what to look for.

I've read conflicting reports, but understand both Autologic and remote coding services should "protect" this change from being overwritten when updates are applied at the dealership.

Either way, I'm sure it's best for base-stereo owners to change to HiFi outputs before tuning aftermarket components. DSP or not, it's better to start with a verified flat input.
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      08-08-2010, 12:00 PM   #12
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Quote:
Originally Posted by Imperator View Post

Either way, I'm sure it's best for base-stereo owners to change to HiFi outputs before tuning aftermarket components. DSP or not, it's better to start with a verified flat input.
With DSP, it really depends how MUCH better it is, as a function of:

1) How good the results are if you don't recode

2) How hard it is to get the recoding performed (distance, degree of coacing of guy running the AL, etc)

3) How much it costs

If I had a customer who wanted the JBL Mobile Synthesis processing, with a center channel and rear effects and all, I would have a tough time saying that recoding was "needed". I would rather improve other things with the same funds.

If we had already handled all the aspects where budget increases could yield what I would expect to be better results - front component selection, underseat woofers selection, amplifier channel count, trunk sub selection if desired - then I would put recoding on the punch list.

On the other hand, recoding on a budget system? If someone would like a 4-channel amp, new fronts, and new underseat woofers, with the rear speakers on deck power - THAT would be powerful. We here would be able to offer a 4-channel system starting around $750 in parts, and a 6-channel system starting around $900. Exact packages differ based on vehicle and component selection.
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      08-08-2010, 01:58 PM   #13
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I just realized that recoding the iDrive output to HiFi changes the output from line-level to balanced differential. There's no point in doing this for an OEM upgrade path like the Alpine HiFi upgrade kit-- you will have removed the "happy-faced" EQ curve but you would also change the output type to something incompatible with amplifiers that can't utilize a balanced input. This is where something like the Zapco SLDIN.BTL-F comes in, as you can just tap the branch audio connector under the seat and send a SLDIN cable back to the amp.

I'm planning a business trip to Portland in another month or two. Unfortunately, I don't plan to bring my car along but I am interested in seeing what you've done with your own car or customers' E9x vehicles. Maybe I could find a nice brewpub or diner and pick your brain for a few minutes.
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      08-08-2010, 02:23 PM   #14
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Quote:
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I just realized that recoding the iDrive output to HiFi changes the output from line-level to balanced differential.
This is a very rough explanation for what comes out of the HU in either mode.

Electrically, the only change is the voltage output.

If we had a 12VDC battery and a 4-ohm speaker, and we were taking the -) terminal of the speaker to the (-) terminal of the battery, and switching the 12V(+) terminal on and off to the (+) terminal of the speaker, the speaker would be pushed forward from its point of rest, then return when the voltage went away, then be pushed forward again, etc.

That method gets you about 3 watts.

If you have a 12DVC battery, and a 4-ohm speaker, and you do the same thing to the (+) side of the speaker terminal, and you INVERT that and do it to the (-) terminal at the same time, you increase the maximum possible DIFFERENTIAL from the (+) to the (-) speaker terminal. You also get about 12 watts possible.

If you were to look at the output of the second scenario on an oscilloscope, it would be indistinguishable from a preamp balanced differential signal.

All that the HU is doing during recoding is changing the output voltage from the one used to push speakers to one more suitable for the input of the HiFi amplifier, and selecting the EQ curve in the preamp IC. There is no hardware change, and the simplest explanation is that the same HW is used in both scenarios. You can optimize such an output for speaker or for preamp use, but most designs would require some physical change - different output wires, or a jumper or switches, or something. For it to be a SW-only setting implies strongly that there is no change to the signal other than the voltage (or to be more pedantic, the electrical drive characteristics).

Feel free to drop a line if you're coming into town. The shop is 95% install, not very "showroom"-oriented at all, but always glad to see visitors. Welcome someone from the forum who could hear my car, too
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      08-08-2010, 02:32 PM   #15
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Thanks again! I'll shoot you a PM once my trip is set up.
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      08-13-2010, 10:55 PM   #16
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So is this where our Subject Matter Experts are positioned at the moment for 2011 E90 base audio systems, either:

1. DSP+Front speakers+underseat subs+rears speakers
or
2. Recode to HiFi+Front speakers+subs+rears (with this option still suspect)

How do you determine ranges of systems i.e. budget, mid-range, high-end system...quality of hardware alone or additional replacements of OEM hardware?
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      08-16-2010, 09:12 AM   #17
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VPE, have you measured the output at the driver's position? I wonder what the RTA would show for the base system in the default setting. A few months ago I did a quick measurement with a sound meter and a swept frequency signal, but a MLSSA measurement would be preferred.

Quote:
Originally Posted by VP Electricity View Post
So I got a 2011 E90 with base audio as a service loaner yesterday (my 2007 E91 has a broken motor mount!?!)

Here are the measurements of the head unit's output:

Front



Rear



Front door only (after the capacitor)



You guys see why I keep saying, don't just add speakers and an amp to 2010+ base audio?

That front roller-coaster signal curve should be a flat line!

There's no way to make good speakers sound good sending them signal like that.

If all you want is boom and sizzle, that's it, but vocals would be nice, don'tcha think?


This is why I keep saying, you need some sort of signal-de-processor, or you need HU recoding.
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      08-16-2010, 11:45 AM   #18
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I haven't measured any of these OEM systems acoustically.

For one reason, we know that they don't sound good, so quantifying the level of suck feels like wanking to me.

For another, in my experience, measuring with an RTA presumes a certain level of distortion-free sound.

If you have severely nonlinear distortions occurring in your speakers (nonlinear in this case meaning that they get worse with intensity, such as higher volumes, or dynamic peaks), if you have a severely distorting amplifier (lots of clipping happens with a 12W head-unit amp IC), if you have higher-order distortion components off of the top end of the 4" that happen in the range a tweeter SHOULD be covering, your RTA results really don't tell you as much as I would like. They look really deceptive. I've seen RTA results for OEM systems that didn't make apparent how bad the systems sounded.

A plot with distortion data would be preferred, but there hasn't been a simple way to generate meaningful data on distortion on in-car systems. I've downloaded a new SW app to try out, but I haven't had the time to figure out how to use it in this way.
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