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MultiWay Conventional loudspeakers with crossovers 

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25th October 2005, 03:53 AM  #1 
diyAudio Member

power distribution
does anyone know if there is a way to calculate a good speaker power distribution for a 2 way or 3 way system? I am trying to build a sound system and have no clue how much power to put into each frequency range. If someone knew how much speaker power to get for lows mids and highs, it would help me out a lot. I wish i had access to the funds to get all the same power speakers and then figure out what sounds right from there, but i can't afford that, i need help to get it right the first time.

25th October 2005, 04:07 AM  #2 
diyAudio Member
Join Date: Mar 2005
Location: Taiwan

The amount of power distributed depends on the number of octaves covered as calculated by the equation N=log(F2/F1)/Log2 where F1 is the lower frequency and F2 is the higher frequency. If you first calculate how many octaves the speaker will totally cover, then you can determine the % each driver sill cover. Note that this normally ends up with XO regions not favored by most purist designers.
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25th October 2005, 08:02 AM  #3 
diyAudio Member
Join Date: Dec 2001
Location: Melbourne, Australia

From "Loudspeaker Enclosure Design and Construction", published by Fane is the following table. There's an article by Rod Elliot on his www.sound.westhost.com website on biamping where he uses this table.
But, essentially, if you're going to cross at 350Hz and 5000Hz, then if your bass amp is 100w/ch, you should only require 70w/ch for your mids and 30w/ch for your tweeters.
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25th October 2005, 08:58 AM  #4 
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Join Date: Apr 2002
Location: Newcastle, Australia

Try this !!
http://users.tpg.com.au/users/gradds...iles/power.xls
for 2way, just enter the same xo freq for 2 values. obviously only a rough estimate !!! but try the values from the table above, they should be reasonably close !! 
1st November 2005, 08:06 AM  #5 
diyAudio Member

thank you all, i will get equal powers al the way around. i already had my crossovers calculated when i posted this. i am doing a 3 way sstem (for now.) my crossovers are going to be at 200 and 2030 hz, and i will cover frequencies from 20 to 20,000 which gives me exactly 3.33 octaves in each frequency range. i already have speakers selected to handle these ranges i jsut wanted to know how many to get, so thank you all for the help.

11th December 2005, 10:25 PM  #6 
diyAudio Member

i just thought of something... does efficiency change the ratios of wattage? like say i had a 9 octave sound system, and a 3 way crossover with 3 octaves in each section. if i had a 100 watt subwoofer with efficiency of 95, a 100 watt midrange driver with efficiency 95, and a 100 wat tweeter with efficiency 95, could i substitute that tweeter for a 50 watt speaker with an efficiency of 98?
PS if any of you have any helpful math tell me about it! thanks! 
11th December 2005, 11:27 PM  #7 
diyAudio Member

oh yea, also, if i substituted the 50 for the 100 going by efficiency, would i have to add any resistors in paralel and/ or series to the speaker or anything liek that? (i always use 8 ohm speakers in all of my constructions, by the way.) I know i wouldn't have to add resitors if the channel was just one type of speaker, but would i, if, say, my midrange was composed of 2 types of drivers of different efficiencies, with 2 way crossovers in the housings, have to compensate for one efficiency with resistance in the higher efficiency speaker?
PS i changed my crossovers to 320 and 2941, giving me a ratio of 10 : 8 : 7. If any of you had info on which ranges contain vocals and stuff i could furtehr change it and perhaps add more to my midrange and cut back on highs to get better sound reproduction. 
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