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DSP curves for the OEM deck

2931 Views 11 Replies 6 Participants Last post by  lo bux racer
If you ever wondered what the DSP curves look like check this out. I connected an RTA (Real Time Analyzer) directly to the outputs of the OEM deck. The volume is set at 60 and all tone controls are flat. There is a disk with "Pink Noise" (sounds like static) playing. The far left of the display is labeled 25Hz and the far right is 20KHz. Each dot represnts 1/3 octave. There is a line through the center of the screen (horizontal) that represents 0 dB. Dots above this line are boosted and dots below are cut.
This is the electrical output of the deck and not the acoustic response of the system. Ideally, you would want the deck to be electrically flat (like an aftermarket deck would be).
It would be great to be able to keep the OEM deck with it's balanced outputs, high voltage swing, aux input, SAT ready, MP3 ready, great integration with the dash and get rid of the EQ curves.



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Was it in tC mode? I tend to believe the curves are different for all 3 cars.
Yes, this was in "TC" mode because this is a TC forum. You're right, they are different for the XA and XB. I can share those curves as well if you like.
For those who wanted to know for whatever reason:

XB Neutral:

XB Hear:

XB Feel:

XA Neutral:

XA Hear:

XA Feel:
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Those of us want to know the different curves because almost nobody uses the tC sounds like ass.
OK, so the curves have been characterized. Wouldn't it make a lot of sense to do the same thing with the speakers to see what the actual output is?

Unless I'm completely mistaken, equalization is intended to compensate for over and under-represented signal at various points in the system so the final output is either flat (all frequencies reproduced as near to matching the original signal as possible) or "sonically pleasing."

I know in the various analog systems I used to tune, equalization is critical to understanding the original waveform and accurately reproducing it. While it's true the seismic systems I worked on peaked at 10Hz, electronic (or digital) EQ is the same regardless of frequency spectrum.
Originally posted by lo bux racer@Feb 15 2005, 07:24 PM
OK, so the curves have been characterized.  Wouldn't it make a lot of sense to do the same thing with the speakers to see what the actual output is?
Not as far as I am concerned.

The reason flat RTA acoustic responses don't sound good in the car has nothing to do with the notion that a flat response is undesirable and everything to do with the fact that an RTA measurement inside a car is an idiotic measurement that DOESN'T MEASURE FREQUENCY RESPONSE... it actually measures a "sound power" response which includes all of the reflected energy. Furthermore, the measurement is typically done at one point in space and will vary dramatically when the microphone is moved an inch or two.

With Scion it's easy to fix this problem by simply replacing the deck, on many vehicles, this is not an option. More and more OEM systems integrate other systems into the decks making it almost impossible to replace. GM is leading the charge on this and the Germans are doing a fine job locking out the aftermarket with their MOST system. The EQ curves are built into many systems (Scion among the worst). If you cannot access these curves and can't remove the radio, adding aftermarket equipment could actually make the sound worse. It's become more cost-effective for OEMs to intgrate DSP to make $1 speakers sound good. It doesn't seem to be present in Scion, but it's very common to have the bass attenuate as the volume is increased (to save the speakers). Imagine paying money for an aftermarket system that has subwoofers that get quieter as you increase volume!
Again in the Scion, the deck is easily replaced....for now.
The bottom line is the OEMs are doing their best to lock out the aftermarket and want to be the only source for audio and electronics (the consumer will have no choice). I feel sorry for the guy who buys the Mazda 6 and finds out that he has to replace the climate controls as well as the deck when it goes!
The company I work for is working on a solution to the growing problem, the writing is on the wall. The data I have shared was part of my research. The unique opportunity afforded by my car was I actually get curves for three different cars. The future of the 12V Industry is integration.

P.S. I don't see the point of switching car modes, they all sound like ass!
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hey jltd..
so basically the head unit is the problem from what I am understanding you're saying. So if let's say I put in an alpine headunit, the stock speakers will "come to life" so to speak? Or the stock speakers will show their inherent short comings?
AFA moving the microphone and getting totally different readings, I can do the same thing with my head. One of the reasons I really don't want to spend a lot of money on car audio is because the soundstage varies dramatically with small movements. I set everything to sound great when I sit in the driver's seat. To the passenger it sounds like ass. Then my wife moves the seat, I get back in, and I have rediscover my sweet spot.

IME, it's a lot easier to do in a room with control over the absorbing and reflecting elements. I don't want to try to achieve the same quality I have at home in my car, hence, I won't spend a lot of money on car audio.

I hope the 12v industry is preparing for the 48v electrics in just a couple of years. Check it out at SAE's website.
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