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View Full Version : determining crossover components and power

AsianInvasian69
06-06-2005, 10:40 PM
Alright i have been into car audio for quite a few years now and id like to think of myself as more than a competant man...anyways when it comes to home audio im kind of a n00b so here it goes

i am trying to set up a good audio system for my room and i was looking to mimic some of the projects done at parts express. I already have a ported tempest off a 380watt plate amp. but my speakers are less than comparable to that. I have been looking to do something similar to these http://www.partsexpress.com/projectshowcase/dr-k-mtm/index.html

Bare with me i have some electronics bargound but i am in no way an expert.
some of the things i had trouble figuring out is how they determine capacitor size (voltage rating discharge speed and capacitance)
inductor size (inductance voltage and whatever other specifications)
resistor size (power rating and other characteristics)
these are just for starters, hopefully some of you electronics guys can help clear things up for me.

also on a much more basic note, how do you determine what power is needed to drive these. I know they are all wired together as an individual channel but i have a hardtime figuring out the necessary power. for instance they use 2 mid drivers with a rms power handling of 60watts each and the tweeter has an rms of 100. does that mean i need around 220 watts to drive them all??? cuz most standard receivers dont do more than about 100/ channel. also if both of the mids are 8ohm drivers and the tweet is a 4ohm does that mean most likely it is wired so the mids are driven in parallel to form a 4 ohm load then wired in series with the tweeter for an 8 ohm load?Still a little confused on impedances in a setup with a crossover

thanks for anyhelp you can give me and any formulas or tutorials would be nice. i know i have some somewhere but i cant seem to find them
95Honda
06-07-2005, 06:23 AM
It is easiest to just start with the text book crossover values. You can find javascript calculators online, just do a yahoo search. This will get you in the ballpark with the values, you will need to tweak once you get everything set up. The figures you will get from a calculator take for granted a resistive load, which speakers are not, they are a reactive load. Sometimes it will sound like ass at first, you will need to try different slopes and frequencies. As a rule of thumb, don't cross over the tweeters any less than 2 times thier FS, and try not to cross woofers over any higher than when thier response gets ragged. As far as power, ratings are just how much power the driver will take thermally before the voicecoils fail, it is not indicitive of how much power you will require. Rule of thumb is, have as much power as you can and don't turn it up high enough that you run into distortion. Drivers are surprisingly robust as long as it is a clean signal you are sending. The RMS power of music is quite low, averaging anly a few watts even when it is loud. Most drivers out there will be driven just fine in a home environment with a 100 watts or so. As for your resistor power rating, you could calculate the voltage drop and dissapation across the resistor, or just use 10 watt resistors if your power will be below 100 watts and use 20 watt resistors if you are going to be driving a lot more than a 100 watt amp. 10 watt resistors are fine in all but the most extreme applications. Also, stay away from inductive resistors, they are not good for audio.
TalNLnky
06-07-2005, 09:53 AM
read this...
http://www.bcae1.com/passxovr.htm

and if you want to read more on that site.... just go to http://www.bcae1.com/


great site... can always find something useful on it.
AsianInvasian69
06-07-2005, 10:29 PM
thanks alot guys for the help ill try to keep you guys posted since this is my summer project
hopefully ill be done by september
I like planning things out alot before i do any buying
ill draw some stuff up and hopefully you guys can help me out

btw im glad that theres a new forum cuz sound illusions was starting to be overtaken by stupid qs
95Honda
06-08-2005, 05:52 AM
btw im glad that theres a new forum cuz sound illusions was starting to be overtaken by stupid qs

Your welcome, and thanks!

Help us put the word out about Force!
MikeS
06-08-2005, 03:26 PM
I'd still like to know how I could get a old Klipsch Cornwall to survive a 270, 300 volt DC blast when I blundered and shorted the B+ of the output transformer to a speaker lead.
Maybe the tweeters survived because of the 600 volt caps I had swapped in there......the other caps are only 100 volts however.

Christ, it was a cannon shot....I guess I'm lucky I still have a speaker.
BigSmooth
06-16-2005, 03:45 PM
Here is a crossover I am building for some guy.
It's for a 3-way set of Focal towers, T120, 5W & 10W.

12db 250hz/3000hz, 15 guage coils and poly caps.
Yes there are a few 50mfd electrolytics (bypassed of course) in the zobel network. He didn't want to shell out another $80.00...
BigSmooth
06-18-2005, 09:44 PM
Completed crossovers L & R channel.
Each one must weigh 15 pounds.
AsianInvasian69
06-22-2005, 04:02 AM
very impressive
i am gonna do my crossovers when i get my home audio set up
can you tell me the specs of this crossover. 12db/octave i presume. what are the caps rated at and what are the inductors rated at and what is the crossover frequencies, etc...
BigSmooth
06-27-2005, 01:04 PM
yes. 12db APC crossover.
Slopes are 250hz and 3000 hz.

15 guage coils and Dayton 250V poly caps.

Ratings aren't too important. You will blow these focal drivers before you have a crossover component fail.
audiobass10
07-07-2005, 03:51 PM
You mentioned the projects on partsexpress..Just bought 15 of these little budget extended range drivers:

http://www.partsexpress.com/projectshowcase/nsb/nsb2.htm

and one of these..

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=275-035

I've been into car audio for a while, but too am new to bringing it in the home. I haven't decided what I want to do with these drivers yet, but i'm thinking line arrays possiby. I need to pick up a couple plate amps from PE as well..gunna be fun.
AsianInvasian69
07-08-2005, 02:34 PM
sounds good
when i first started car audio
i always wondered why people ever had systems in home...i thought they were a waste

then i saw peoples system like 95 hondas.....i saw his setup on another forum...i think had 2 15s......ya
MikeS
07-08-2005, 09:26 PM
sounds good
when i first started car audio
i always wondered why people ever had systems in home...i thought they were a waste

then i saw peoples system like 95 hondas.....i saw his setup on another forum...i think had 2 15s......ya


I got into car audio because the car was my home most of the time.
doc
07-08-2005, 11:17 PM
Ya, for those of us stuck in apartments, the car is the only place to get loud :/

I wish I could do a home system... so many more cubes to work with :)