audio crossovers..help me - United Bimmer Community

**Numark318i** · 10-04-2005, 12:17 AM

yea i need some help with audio crossovers for my car stereo. anyone know anythign about these things. I got a 4 channel amp with 6 speakers so i think i need it. ...help!!!

**Dudesky** · 10-04-2005, 02:20 AM

Need more info to help. Having more speakers than channels doesn't necessarily mean you need a x-over. What type of speakers are they? Are they components or full range (coaxial / triaxial)? Or are you trying to add an amp to a stock BMW system?

(Edit): Okay, I just saw your other post ("Help with install..??"), and now I understand what you're doing. But can you give me the model numbers of the Nak amp and MB Quart speakers, and/or some pics if possible? Low and high crossover inputs doesn't sound right to me, but if I can see a photo or pull the tech info off the web, I can probably help you out with this.

**Numark318i** · 10-09-2005, 02:29 AM

ok ill get those top you tomarow...im lazy at the moment.
thnx for the help ahead of time though.

**Numark318i** · 10-11-2005, 09:53 PM

ok so the nac amp is a Pa-504. Heres pics of everything.
need anything more.
the head unit might not be taht one..that ones a nak cd-500...but i cant find a wire harness for it..):

so can u help?

**Dudesky** · 10-11-2005, 11:37 PM

IF:
Channels 1 & 2 are front left and front right
Channels 3 & 4 are rear left and rear right

THEN:
Channel 1+ goes to left crossover High Input +
Channel 1- goes to left crossover Low Input -

Channel 2+ goes to right crossover High Input +
Channel 2- goes to right crossover Low Input -

Wire the woofers and tweeters to the crossovers as normal.

Channels 3 & 4 connect as normal to the rear coaxial speakers.

The reason you have low and high inputs on the crossovers is in case you want to bi-amplify the speakers. But you only have 4 amp channels and 6 speakers, so that's not possible anyway.

Hope this helps

**komodo** · 10-11-2005, 11:38 PM

Hey, anyone interested in turning this into a knowledge base article about wiring car audio?

**Dudesky** · 10-11-2005, 11:47 PM

Aaaack!

Too confusing . . too many different wiring schemes between all the manufacturers as well as the car makers. For example, the E36 has at least 3 different wiring setups that I know of, and the way MB Quart sets up their crossovers is not necessarily the same as other brands. You really have to take everything on a case by case basis. Plus, I didn't mention this to Numark, but there are at least 3 different ways to set up his system, I just gave him the most common configuration.

**Numark318i** · 10-12-2005, 12:29 AM

thnx dude
which one will give me the best sound? or does it make a difference?

**Dudesky** · 10-12-2005, 07:34 AM

The PA-504 is so versatile that you can configure it in quite a few ways. If this were my system, I would add a subwoofer. Then wire it like I wrote above, except you power the rear coaxials with the radio instead of the amp. Ideally, you want just some rear fill so the front sound stage is not lost. Thus, less power to the coaxials would be good. Then you bridge channels 3 & 4 on the amp to power the sub, and activate the low pass filter. That would give you 50w per channel up front, about 25w per channel in the rear, and 175w mono for the sub. End result: a nicely balanced 325w total

**Numark318i** · 10-18-2005, 01:10 AM

ok well i started wiring for the system. how about power to the amp? explain?
also how far can the speaker be from the crossovers?

**Dudesky** · 10-18-2005, 06:00 AM

Power to an amp requires 3 wires: +12v, ground, and remote. If you previously had a stock factory amp in there, DO NOT use the power wires from that harness, run new cable instead. The old wires will be too thin. The only wire you can reuse is the remote turn on wire. The +12v line should be connected directly to the positive post of the battery. Make sure you add an inline fuse on the +12v line as close to the battery as possible to avoid short circuiting (use the same fuse rating as the one on the amp). The ground wire should be as short as possible, and terminated somewhere on the car's metal chassis near the amp. In your case, both +12v and ground wires should be a minimum 10 gauge wire, preferrably 8 gauge. Connect the remote wire to the blue wire coming out of your head unit. This one can be 16 or 18 gauge. The easiest way to get all this stuff is to buy an amplifier wiring kit for about 10-15 bucks. This will have everything you need to do the job.

The crossovers can be mounted anywhere. Some people have them close to the speakers, some choose to mount them alongside the amp, doesn't make a difference. I mounted mine next to the old stock amp to make use of the existing speaker wiring. What does matter is the distance between the woofer and the tweeter. Ideally it should be no more than 15" or so, but up to 2ft is still okay. The further apart they are located, the worse your sound will be. I assume you're installing them in the stock locations; that should be fine.

Some notes on wiring up . .

-Try not to run power and signal wires alongside each other. The power wires can induce electrical noise into the signal wires. And don't skimp on the RCA cables- use high quality shielded and grounded wires to avoid ground loops and electrical interference. You'll regret using the cheap stuff because you'll end up having to run new cable all over again.

-BMW chassis are known to have wildly varying resistance values from one location to another, more so than is typical of other cars. A real BMW service manual will indicate the designated grounding points on the vehicle chassis (I don't think Bentley has this info). Most places should be okay for an amp, but bearing this in mind, if your amp isn't working properly, try relocating the ground wire in different places, and make sure you have good clean metal to metal contact.

**Numark318i** · 10-25-2005, 07:55 PM

ok i got another q.
i think what i want to do is power the rear speakers with all four channels of the amp. can i do this? I want to run channel 1 and 3 to teh left and right tweeters(respectively) and 2 and 4 to the left and right rear woofers. Ill leave the front two speakers on the radio. this way i get a good distribution of power. now the rear of the head unit has a rear and front output with a left and right rca. now i got a spliter, that makes one RCA cable into two, so that i can make the two rca's into four.
is this possible?
i tried but the amp says protection and shuts down..no wires are crossed.

**Dudesky** · 10-25-2005, 09:16 PM

Ugh . . need more info, coz now I'm confused. Which are you using for fronts? The coaxials or the component speakers? And is there a feature to disable the crossovers on the amp?

Either way, you need to run 1&2 to the tweeters and 3&4 to the woofers, not 1&3 and 2&4. By doing it the way you described, you're creating an imbalance between the matched pairs on the amp. This could be why the protection circuitry was activated, or it could be because you're using the crossovers form both the amp and the speakers at the same time.

As far as the RCA splitters, that's okay to do, you'll just get a lower input signal level going to each amp channel.

**Numark318i** · 10-25-2005, 10:15 PM

ok i figured it all out
sounds amazing. I took out the crossovers, put tweeters on channel 1,2 woofers on 3,4 and holy shit this sounds good. a little strong in the back, but i can adjust some shit to fix that. i grounded on the strut tower.

**Dudesky** · 10-25-2005, 10:23 PM

Sweet!

**Numark318i** · 12-14-2005, 06:22 PM

update again..i rewired it all so that i had the cross overs...10times better. goes louder then i can hear...and its still clear as day.