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Old 11-21-2003, 08:32 PM   #1
robray
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JL Audio balanced differential input question??

I have a my factory head unit hooked up to a JL Audio 500/5 and that is hooked up to my stock speakers. I will be upgrading the speakers very soon and adding a sub, but I wanted to hook up the amp first.

I have the gain of my amp turned down almost completely and the input sensitivity switch is on high (800mV to 8V RMS range). Basically the gain is very low. Anyway I notice that the sound is not very clear. If I have the volume at a fairly low level that would be clear with the stock system, I find that with the amp it seems a little distorted. Obviously if I crank it up it sounds like crap cause my stock speakers are junk, but at comparable volumes I would expect it to sound just as good or even better.

I emailed JL Audio and told them my situation and they said, "... we have found the same situation in all BMWs, when keeping the OEM head unit. There is some type of "colorization" that is found from the output of the BMW head units. We have several BMWs in the parking lot and we have tested them all. All had this "colorization". Once we replaced the head unit or used a High-Low converter, this "colorization" was no more."

I know there are people out there that are not using a High-Low converter with JL amps. So I am trying to figure out if there is something wrong with my system. I am going to check things out with a scope tonight.

Has anybody tried with and without a High-Low converter to see which sounds better?
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Old 11-21-2003, 09:30 PM   #2
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In Europe we have three different stereo options, Business (standard), Hi-Fi and Harman/Kardon and all stereo options are using the same headunits (cassette, MD, CD and Nav).

But the Hi-Fi and H/K options have an external amp with built-in active crossovers in the trunk. And the headunit is using balanced differential signals from the headunit to these amps.

If you don' t have the Hi-Fi or H/K amps you have speaker level signals from the headunit to the speakers!? So do the headunit need any sort of control signal to turn on the balanced differential signals?

Just a thought since I never heard of this problem when people have upgraded their H/K systems.

/RS2

Last edited by RS2; 11-21-2003 at 09:33 PM.
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Old 11-22-2003, 03:01 AM   #3
robray
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RS2, you are probably on to something. I have the base Canadian system, so I just have six speakers and no amp. Initially I thought my head unit didn't have the differential outputs, but when I measured the voltage on the speaker outputs I saw there 6VDC on the speaker positive and negative. Because of this I guessed these were balanced differential signals.

Well, tonight I have the scope on my speaker outputs and I am seeing a 6VDC offset on the speaker positive and a 6VDC offset on the speaker negative, but there is only signal on one of the signals. The other just sits at 6VDC.

I am playing a 1KHz sine wave in the CD player and the sine wave is about 8Vp-p around the 6VDC offset.

Here is some pics of the scope.



This one is with the volume cranked. Check out the clipping.



Is this what normal unbalanced signals are like? Do they normally have a big DC offset? I imagined it would be a 0V negative and a positve signal somewhere above there. I need a lesson in what unbalanced signals are supposed to look like. Time for Google...
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Old 11-22-2003, 08:28 PM   #4
RS2
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See these link for some more info about balanced signals.

/RS2


Balanced Line Drivers

Basic Car Audio Electronics
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Old 11-22-2003, 08:38 PM   #5
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Quote:
Well, tonight I have the scope on my speaker outputs and I am seeing a 6VDC offset on the speaker positive and a 6VDC offset on the speaker negative, but there is only signal on one of the signals. The other just sits at 6VDC.
Then it's floating ground and not balanced signals and you will probably need a VEN 4 or similar LOC.

But like I said previously, the same headunit do have balanced differential signals in a H/K system.

How have you connect the wires to the RCA contacts of the JL Audio amp? If you have balanced signals you can use the JL Audio connector below.

/RS2


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Old 11-29-2003, 10:21 PM   #6
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bump i am getting ready to install the 500/5 and would like more info on this
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Old 12-01-2003, 07:44 AM   #7
mickjagger
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I recently had the OEM HU connected to a JL 300/4 and MB Quart speakers. It sounded OK, but did have some coloration and lack of clarity.

Finally bit the bullet and got an Eclipse 8443 HU. BIG DIFFERENCE!!

Now I am troubleshooting other issues, like tweeter placement, deadening doors, etc....
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Old 12-01-2003, 03:26 PM   #8
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JustinB181,

What do you want to know?

I don't have much info that would help you out, because my head unit is the amplified version and I am waiting for an LOC from David Navone (N-774V). The JL amp seems to work fine with my "high level" outputs from the factory head unit, but it just doesn't sound that good.

I was talking to another guy with a similar setup, but using the HK factory head unit. He tried hooking up a Peripheral VEN4 and found it made no difference at all to the sound. He also found that the sound is not that great with the factory HU and a JL 500/5.

You'll find out soon enough if the sound is something you can live with. Personally I think it sounds pretty bad and I am hoping the LOC will fix things for me, but I am doubtful it will.

I'll let you know.
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Old 12-08-2003, 04:10 PM   #9
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Thanks for the information, I do plan on getting an indash DVD/TV very soon but until i did i was hoping it would sound good. My old car i hooked up my system to the factory head unit for a few months and it sounded very good almost as good as the aftermarket pioneer premeir deck i had. Let me know what you figure out.
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Old 12-08-2003, 11:26 PM   #10
Frank Rizzo
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Quote:
Originally posted by robray
JustinB181,


I was talking to another guy with a similar setup, but using the HK factory head unit. He tried hooking up a Peripheral VEN4 and found it made no difference at all to the sound. He also found that the sound is not that great with the factory HU and a JL 500/5.


Hey....... I know him.
You can live with it, but if you are a near-audiophile, then you can hear it. "colorization" is the perfect description.....it sounds just a little "off".

Meanwhile (Rob) ther is a guy on choadfly with a smilliar set up that has white noise coming from 3 speaks at low levels when the HU is off?
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Old 12-08-2003, 11:38 PM   #11
///NYCM3
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peripheral ven 4

Peripheral ven v is the unit most videly used to fix the noise form the stock headunit. The stock signals need to be grounded by the amp, but the ven v eliminates that.
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Old 01-10-2005, 05:17 PM   #12
farris
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Lightbulb DAvid Navaro LOC

I got the same N-774V LOC to hook up my 12 inch W7 to the harmon kardon navigation unit with DSP in my 04 M3. Please let me know how it works out for you. DO you think it will be much of a problem with low frequencies like bass going to a sub? I am getting it installed in 8 days. Best Luck and Please let me know what happens with your setup. May the god bring you clean vibrant sound
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Old 01-11-2005, 07:31 AM   #13
Technic
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Quote:
Originally Posted by robray
RS2, you are probably on to something. I have the base Canadian system, so I just have six speakers and no amp. Initially I thought my head unit didn't have the differential outputs, but when I measured the voltage on the speaker outputs I saw there 6VDC on the speaker positive and negative. Because of this I guessed these were balanced differential signals.

Well, tonight I have the scope on my speaker outputs and I am seeing a 6VDC offset on the speaker positive and a 6VDC offset on the speaker negative, but there is only signal on one of the signals. The other just sits at 6VDC.

I am playing a 1KHz sine wave in the CD player and the sine wave is about 8Vp-p around the 6VDC offset.

Here is some pics of the scope.



This one is with the volume cranked. Check out the clipping.



Is this what normal unbalanced signals are like? Do they normally have a big DC offset? I imagined it would be a 0V negative and a positve signal somewhere above there. I need a lesson in what unbalanced signals are supposed to look like. Time for Google...
... it seems to me that what you have is a floating ground system based on those charts and measurements... and the fact that you have a regular sound system without amp. That fact alone takes the differential signal issue out of question in this discussion. Regardless, you will need a line converter to get your signaling normalized before going to the amps.

I would get a SVEN4 and call it a day...
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Old 01-11-2005, 07:41 AM   #14
Technic
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Quote:
Originally Posted by JustinB181
bump i am getting ready to install the 500/5 and would like more info on this
These are the two best DIY for upgrading the HK system without changing the HU's, IMO:

http://bimmer.roadfly.org/bmw/forums...4308496&page=1

http://bimmer.roadfly.org/bmw/forums...786337-10.html
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