Wire length with passive crossovers?

cherrybomb · 05-10-2007, 07:32 PM

Hi All,

Okay, I realize this isn't a dedicated Car Audio board, but this is one of the forums I'm most active on, and figured I'd ask here first.

My question is, are there any "best practices" related to a passive crossover's proximity to the speakers it's driving?

I'm asking because, I'm seriously considering running the passive crossover very close to my amplifier, and a "long" run of speaker wire to the actual speakers in the door.

It's my understanding that usually you run the single "long" speaker wire from the amplifier, to the passive crossover, then "short" lengths between the passive crossover and the drivers.

Just wondering if there is a preference, or if there is any negative effect by putting the crossover closer to the amp, rather than the drivers.

Thoughts?

Thanks!

greatwhite · 05-10-2007, 07:41 PM

I've seen it both ways.
But that was for presention purposes (ie: crossovers inthe trunk for show off effect).
Everyone I know who has the crossovers in the trunk swear there's no difference. But, they just may not know what they're "hearing".
My passives are on short runs, but I have thought of putting them in the trunk next to my amps because I've worried about water in the doors and space issues everywhere else (well, show off the MBQuart names too!).
Sorry if that's not too much elp, maybe durwood can chime in here?

Cheers

cherrybomb · 05-10-2007, 08:07 PM

Hey Great,

Thanks for the quick response.

It's good to know at least that people have done it without any drastic issues.

Logically, I can't see any reason why it would be an issue, unless the small extra amount of capacitance/resistance across the long run changes the crossover frequency somehow, but I don't know enough about passive crossovers to know if that's even a consideration.

Maybe durwood or someone else will enlighten us both.

Like I said, I'm leaning toward mounting them close to the amp for the same reasons you mentioned 1) more space to mount them there 2) show of the fact that I bought MBQuarts, ;-)

lbridges · 05-10-2007, 08:57 PM

It's a virtual certainty that durwood et al have tons more practical experience than I, but from a technical standpoint (I'm a physicist) there is no practical difference between mounting locations of the crossovers. Contrary to many manufacturer claims there are only three things affecting cables and wires in a stereo installation (assuming noise is not induced) and those are resistance, inductance, and capacitance (RLC). As long as the difference in mounting location does not materially affect any of those values, there will be no difference.

durwood · 05-11-2007, 06:19 AM

No difference. It's really a matter of what's easier. I've installed them both ways.

Things to consider:
-Do you have the space in your doors to mount them where water damage won't be an issue?
-If you mount them in the trunk, you will need to run two pairs of wires down the vehicle in your door or wherever you plan on mounting the speakers.
-Just note that passives can pick up induced noise from power wires. The inductors are a coil of wire that can act as an antenna. It's rare, but I have seen it happen. There was at least one member here that had that problem a while back.

If you bought the Q series MB quarts, those things will most likely have to go in the trunk because the passives are HUGE. I did it years ago see attached pic.

greatwhite · 05-11-2007, 06:38 AM

Yup, I've got the Q series too (hey, easy, I've only got so much money to throw around!), and yup, the passives are pretty big.

I have them sitting in my door pockets right now for "prototyping" purposes (wires are EVERYWHERE!). I've been agonizing about placement in the door due to the aforementioned water and space issues. I was going to place them up under the dash to keep the wire runs short. Maybe I'll just put them in back on my amp rack now......Lord knows, there's lots of space back there not that the puter is in an 18 gauge sheet metal case bolted to the side of the trunk (no-one's stealing that sucker without a torch or impact gun!)....

I feel a little better about this possibility now that "Durwood has spoken" and given it a more-or-less thumbs up!

And Durwood, that's a pretty nice/clean install for an early attempt! What's that "water-like" finish by the sub? It looks like brickets under a barbecue grate!

Different and kinda cool.
Tailgate party material?

Cheers

BJ

Dennis5587 · 05-11-2007, 07:50 AM

hey Durwood... is that a BBQ grill in that pic, in front of the sub?

durwood · 05-11-2007, 09:29 AM

[OT]

Yes it was my old install in my Civic hatch-before the carputer back about 4 years ago.

It wasn't a real functioning BBQ. It started off a statement I made at work about how I like amps that you can cook a steak on, because then at least you know they are doing something. The old kicker ZR series amps are definitely cookers if you have never used one. They would get extremely hot and trust me, I am sure you could probably cook something on them. SO anyays we created the car-BQ using the Q components which I went to my first SQ show with. I painted each ceramic charcoal brique to make it look real. There were red and orange LEDs hidden throughout the charcoal that made it look even more real. Everything was glued into place and never moved even though my SPL was measured at 143Db with a single 12 sealed - not that I cared since I was competing in SQ, but it got freaking loud for the combo.

The "grill" was actually wire shelving closet stuff which we sprayed with glue, sprinked sawdust all over for that authentic used grill look, and then finished it off with your basic black enamel spray paint.

I had a cover that opened finishing it off. Also of special note was the dual HU's, Eclipse CD8443 for all the tuning, and another Eclispe that played my MP3 CDs and fed into the aux-in on the 8443.

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[/OT]

cherrybomb · 05-11-2007, 11:32 AM

Cool!

Thanks for the info durwood.

Looks like I'll be mounting them near the amp. I really don't have space in the doors, unless I modified the door panel, which I'm not really interested in doing now.

All of the wire I bought is Monster Cable 14/4, which is four individual 14ga wires in a single shield, so I was already planning on running enough wires up there, might as well make use of them for seperate drivers. :-)

I got MBQuart PCE 213's, and by that picture, my x-over is even bigger :-/

Thanks again. I hope to have some pictures up of my progress soon. This project is kicked into high gear, and I'm really starting to make some progress. It's exciting! :-D

greatwhite · 05-11-2007, 11:36 AM

Quote: Originally Posted by durwood

[OT].........It wasn't a real functioning BBQ. It started off a statement I made at work about how I like amps that you can cook a steak on, because then at least you know they are doing something. The old kicker ZR series amps are definitely cookers if you have never used one. They would get extremely hot and trust me, I am sure you could probably cook something on them. SO anyays we created the car-BQ using the Q components which I went to my first SQ show with. I painted each ceramic charcoal brique to make it look real. There were red and orange LEDs hidden throughout the charcoal that made it look even more real. Everything was glued into place and never moved even though my SPL was measured at 143Db with a single 12 sealed - not that I cared since I was competing in SQ, but it got freaking loud for the combo.

The "grill" was actually wire shelving closet stuff which we sprayed with glue, sprinked sawdust all over for that authentic used grill look, and then finished it off with your basic black enamel spray paint.............

LOL! Cool idea.

Bonus point for showmanship and a sense of humour!

Cheers

BJ