Cadillac Audio, Video and Security Systems Discussion, DSP info in Item Specific Cadillac Discussion; Does enabling the "driver" location setting using dsp on a 96 Bose boost the front speaker sound AND leave the ...
- 11-25-13 01:53 PM #1Cadillac Owners Connoisseur
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Does enabling the "driver" location setting using dsp on a 96 Bose boost the front speaker sound AND leave the rear level unchanged? I think I sense a slight drop in bass from the rear but I think I might be imagining it.
- 11-26-13 12:01 AM #2
Re: Dsp info
It is far more complicated than that.
The sound waves travel in air with around 700mph. Think like a wave on the surface of the ocean but 200 times faster (that is mach 1 btw). The light speed is about 671000 faster than the speed of sound. You can approximate that from the amp to the speaker (inside the wire) the signal go as fast as light speed (as electrical signal) while once is transformed in sound (mechanical waves) the speed is so much smaller.
In the wires the speed of the signal is fast enough that having wires of different lengths (even many hundreds of miles different) the difference is totally insignificant plus in a car we are talking about few feet length difference,
But once the signal become sound and it has to travel trough air is so much slower. We can calculate the sound sped in ft/s to ~ 1250 let’s say is 1000 ft/sec, thus in 1 ms the sound travels 1 feet. This means the sound from the rear right speaker (the furthest from the driver’s seat) will arrive ~4 ms later than the one from the front left speaker. The other 2 speakers are somewhere in between.
Believe it or not the human ears (actually the brain) is capable to distinguish this difference. So the sound will sound a bit off (mixed).
By delaying (we are talking ms here) the sound from the closest speakers in such way that the from all speakers arrive in the same time to the driver’s seat you get to feel like the music is in your head (basically puts you in the sweat spot) between the speakers.
The DSP (Digital Sound Processing) level while in the DRIVER’s SEAT mode it adjust this amount of delay (the lower the level the lesser the delay thus the lesser the effect. As the name implies this is done digitally inside the Amplifier. The amplifier is not just an amplifier, is actually a sound processor with an amplifier at the end.
- 11-26-13 10:57 AM #3
Well, front speakers are midrange/tweeters and rear are mid/bass. Seems to me GM never intended all 4 riders in car to have same impression of music. U would think the rear seat passengers would hear more of the sound coming from the rear speakers since their heads are about 1 foot away? Driver head is 4ft from door speaker. So, "driver" mode uses delay mostly, not frequency tweaking? Cuz I know "talk" setting is certainly frequency tweaked.
- 11-26-13 11:19 PM #4
Re: Dsp info
You didn't get it, is not about the volume level is the delay.
I am not sure if the volume is adjusted as is not so important, human ear is not sensitive enough to make a difference on super small level differences between two identical sounds, but is really sensitive to the delay, this is why we have 2 ears to distinguish the direction of the sound.
Think of the primitive human running away from predators and chasing it's own prey.
It was very important to know if there is a sound what direction is coming from so you look that way and make visual contact (or run in the opposite direction), but is not so important to tell if the sound source is 3 feet further or closer (especially when is close enough to be visible).
All these are not mentioned in the user's manual however it is mentioned in the user manual that DSP Driver's seat setting is optimized for the best hearing experience in the driver's seat area, it does mention also that the passengers may not have the same sound experience.
Now back to the DSP (and BOSE sound system in general).
It was custom designed considering the placement of the speaker, the cabin interior, the cabin materials…. Basically it was designed specifically for your car, unlike an aftermarket sound system that is just designed to work ok in cars. Some cars have more reflective surfaces (as index or area) than others so the same sound system will NOT sound the same in different cars (even if the speakers are placed in the same relative position).
Let me state this so is out of the way…a vehicle is nowhere near the ideal place for an audio system so have this in mind when you read.
So BOSE sound system specially designed for your car ONLY, that’s clear now!
Sound speed and attenuation varies with temperature, air composition, frequency and some other less important factors.
Let’s say the air composition (and density) varies with the altitude (the higher the altitude the less dense the air and the slower it travels). Sound tends to travel faster and longer (lower attenuation) in dense materials. The vehicle does have a sensor for pressure (used for adjusting the engine air/fuel mixture), this information is available on the data bus all the time.
The temperature of the air does have an important effect in the sound speed. The vehicle also has a cabin temperature sensor (plus and outside temperature sensor). This information is also available on the data bus.
With that said I am not sure if the RIM does considers the above-mentioned parameters in the equation that calculates the sound delay (but would be sweet as all the information is there).
Now ideally the speakers should be placed (left/right) symmetrically in respect to the auditor. But that means you will have speakers in the middle of the car dangling from the roof or something, So there were constrains when choosing the placement of the speakers (the car is designed for occupants not for sound system). So because of these constrains the sound quality is affected (slightly). The DSP is designed to compensate for some of these drawbacks using software. It will never be as perfect as real thing, but you have to appreciate the level of engineering and consideration put into this car compared with others,
Some people will just judge the sound system based on which one is louder or more bass(ier). The cars are not meant to be driven with the sound cranked way more than the regular level of a speech, it is not safe, healthy or comfortable. Ideal sound is as close to natural sound as possible (level and frequency distribution), with the least amount of distortion. That’s what BOSE give you.
- 11-28-13 02:21 PM #5
Volume or delay when it's in "talk" mode? Explain talk mode please
- 11-28-13 03:33 PM #6
Re: Dsp info
"Talk" mode takes all the low bass (there is NO "sub" bass in a car) out of the sound signal and may add a touch of treble to cut through road noise - traditionally, radio stations hype up the lower midbass to add "weight" to announcer's voices - that's why many radio stations sound OK on music, tubby on spoken voice. As N*Caddy posted, the Bose systems are voiced to sound like acoustic music played in a natural space - many aftermarket car "sound" systems are hyped up bass reproducers, going under the mistaken impression that more bass = real music. Lots of "thump" with a screechy midrange. That frequency alignment altered the slang term "Ghetto Blaster" and applied it to car stereo.
It's tough to build a world class sound system into a closed car: You are literally inside the speaker enclosure(s).
FWIW, "Talk" mode is discussed in the owner's manual in the chapter which includes "Sound Systems".
- 11-28-13 10:03 PM #7
Re: DSP info
As Sub mentioned "Talk" filters the low frequencies out and it does slightly reduces the volume.
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