Hi.
This is the first time I install sound system. The only problem that I have is that there seems to be an engine noise (really loud ones). I’ve install clarion 935vd for the head unit, I put the head unit in the underneath the back seat. From the head unit I take two sets of RCA cables. One to the first two way phoenixgold crossover (MX2), then go to 2 chan amp BRAX X1000, where it’s connected to 10” W7. The other RCA goes from the head unit to the second two way phoenixgold crossover (MX2) (I’ve got two of the same phoenixgold crossover).
From the second crossover I took 2 sets of RCA, both of the go to 4 chan Xtant amp (4180c), I’ve used it before in my previous car and it worked fine. From the Xtant, it goes to 2 6.5” scanspeak speaker in the front, another 2 go to 5” scanspeak tweeter in the front. I have no amp for the back speaker, only from the head unit. My car is 323i 2000 BMW. For the amp ground I take from the factory ground in the right behind of back seat (8 GA). For the crossover and head unit ground I took from left factory ground behind back seat. For the power I take directly from the battery in the trunk (8GA). I run the RCA separately from other wire, RCA on the left of the car and other wire in the right of the car.
I went to a few audio stores, one of them did a check on it and told me that the noise is coming from the Xtant amp. So I bought a used 4 chan Butler tube amp (TD 475). Then I installed it, but the engine noise is still there. I went back to the store and they only change the butler amp with the same cable to four channel Alpine amp. and the engine noise was 80% gone. Then the guy tried to bypass my crossover and the engine noise is 100% gone.
So do you guys have any suggestion to what I’m supposed to do to eliminate the engine noise? Thank’s for your help.

[ November 26, 2003, 09:04 PM: Message edited by: PLOW ]

I would first switch to 4gu power/ground wire.
Then, it seems the noise problem is in the crossover so try finding a new ground for it as right now it is tied in with the HU.

i already used 4GA then i split it to 8GA to the amp, and i already try to bypass the crossover but the engine noise still there.
thanks.
any other suggestion?

You said the shop bypassed the crossover and the noise was 100% gone correct?

The system design sounds good, but you quite clearly have a ground loop problem. There are few options for solving it.

You can rewire the system such that every component only uses a single ground point. I would suggest that the 'factory ground' is a quite bad choice as all the cars electronics are also using that point. I am a strong advocate on running a ground from the battery, and distributing the system from an isolated block in the back of the car (or wherever is convenient). You want a star-ground configuration.

What you might be able to get away with though as a patch for your noise problem is to short the shields on your RCA's coming into, and leaving the crossover. There is a chance this will help, not a guarantee.

If you want a real true step-by-step noise troubleshooting process, there is one on my website written by a good friend of mine when he worked at Audio Control.

I had a noise checklist on my website, but for some reason I can't find it. I'll hunt that down and post it in the morning.

It's only 100% gone if the crossover is bypassed AND the amp is changed to Alpine.
If the crossover is bypassed and I'm still using the butler amp, the engine noise is still present but only about 80%

Can you tell me in detail how to do the star-ground configuration. Also I don't quite understand what you mean by "to short the shields on your RCA's coming into, and leaving the crossover". Btw I'm using Rockford RF Matrix RCA.
Thank's

Take a piece of wire, strip off the insulation and connect the outer metal jacket of the input RCA cables to the outer jacket of the output RCA's. I sometimes use a hunk of solder and just wrap it around each to test this theory. Then if it works, I get really creative, go inside the unit and do my shorting on the circuit board.

Star grounding means, you connect every ground (deck, amps, EQ's, etc) to one point. If you want to ground at the back of the car, then run a ground to the chassis, then to a terminal block. Connect all your grounds to this block. Voila!

The noise troubleshooting checklist on my website is on the Tech > Setup section, which is what was missing.. AHA! Um, let me fix that right now, now that I have found it... sheesh!