Speed Compensated Volume in GM vehicles - diyAudio
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Old 10th October 2007, 04:31 PM   #1
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Default Speed Compensated Volume in GM vehicles

I've done my best to search the site and the internet in general, but I can't find anybody saying anything about the SCV in GM vehicles and whether or not there are any head units that can take advantage of it as an after market unit. I have come to really love the feature, and riding around with friends who have after market units, I am always annoyed by how often they have change the volume of the radio. Are there any head units with native support of the SCV, any that will use it with a converter, or is there even DIY route I could take?
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Old 10th October 2007, 05:23 PM   #2
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I have a late model GM product with the feature and also love it. I am not aware of any other unit offering this feature. I wonder if it is electronically tied to the throttle position sensor, or the speedo sensor? You will need a wiring diagram for the system and perhaps buy a used one off ebay to back engineer.
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Old 10th October 2007, 07:35 PM   #3
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I did find a little bit of info. On a Camaro forum, they have a wiring diagram of the hookups on the GM Delco radio that many of 90's GM vehicles came with. I'm not sure of the Camaros had the exact same radio as a 98 Monte Carlo like I have, but if they are the same the post here http://www.ls1tech.com/forums/showpo...41&postcount=3 shows that there is a line one could tap into for a signal, but whether it is digital, analog, or whatever else. I haven't found yet.
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Old 10th October 2007, 08:08 PM   #4
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My old JVC L-Kamelion head unit has an option on it that increases the volume at a with speed. I have to assume it counts the spikes in the unfiltered turn on voltage, but I really am not sure how it does it.

It does work pretty cool though. they still may have this option on the newer JVC decks.
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Old 10th October 2007, 08:14 PM   #5
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OK wire number 16 supplies the speed signal. The rest of the circuit is internal to the radio. My unit is a Monsoon type. The next move is to find a schematic for the radio. Should be a IC driven off the 16 wire that controls the volume with speed.
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Old 10th October 2007, 09:47 PM   #6
Flyin11 is offline Flyin11  United States
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Never did like that option Rediculous IMO Just like today coming home on the highway...I was rolling right along at 70mph then came up on a slow down or traffic jam. I'm listening to my music at the level I want to...The radio would have turned the volume down on it's own. Why the heck would I want it to turn down on it's own when I slow down behind the other cars? I'm rollin and jammin...I want to keep on jammin...Thanks goodness I have a regular radio and stuff...
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Old 11th October 2007, 12:17 AM   #7
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Quote:
Originally posted by Flyin11
Never did like that option Rediculous IMO Just like today coming home on the highway...I was rolling right along at 70mph then came up on a slow down or traffic jam. I'm listening to my music at the level I want to...The radio would have turned the volume down on it's own. Why the heck would I want it to turn down on it's own when I slow down behind the other cars? I'm rollin and jammin...I want to keep on jammin...Thanks goodness I have a regular radio and stuff...
The SCV feature seems to be a love it or hate it feature. People like me love the feature and it is another reason that I'm hesitant to add a new radio (though the benefits of RCA outs and crossovers in a new head unit would still over weigh the downsides). Then there are people like you that can't even see why it was included as a feature. Different strokes for different folks I suppose.

P.S. Surprisingly, I am a teenager who actually doesn't feel the need to always be blasting my stereo. I like having it at a comfortable volume above the road noise, hence why I like the SCV feature. And in Flyin11's case, if I do feel like jamming no matter the speed, I can always just spin a dial and turn the SCV off.
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Old 11th October 2007, 01:12 AM   #8
ppia600 is offline ppia600  United States
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Yeah, I've seen a few JVC's that have that feature. I think maybe some eclipse's have it too. Can't remember if it was the higher end navigation units though..
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Old 11th October 2007, 03:46 AM   #9
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I had a Nissan with that feature many years ago. I believe there was a small microphone in the radio itself that listened for LF noise, and adjusted the radio volume as needed. No connection to vehicle speed. Seemed to work fine, though I don't think I used it much. OTOH, there was also a sealed microphone at the base of the windshield with a 1" or so flat disk area. When the wipers were set to intermittent, the mic integrated the number of raindrop hits, and adjusted the speed of the wipers accordingly. That worked really well, and I've missed it ever since. I don't miss the deadpan female voice that would say things like "door is a jar".
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Old 11th October 2007, 03:41 PM   #10
Flyin11 is offline Flyin11  United States
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Quote:
Originally posted by LightwaveDude

And in Flyin11's case, if I do feel like jamming no matter the speed, I can always just spin a dial and turn the SCV off.
Oh...I didn't know it comes with that feature. It just goes off if you touch the volume? Atleast you can adjust it like that then. I was thinking that you could never turn it off...That it was part of the car system and always on. Pretty cool feature to be able to turn it off then...
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