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jmelton86 
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Joined: February 07, 2007
Location: South Carolina, United States
Posted: February 26, 2007 at 6:43 PM / IP Logged  

I am wanting to make a simple first order (6db) 2-way crossover. I would like to make the x-over freq. at about 2500Hz so speaker selection will be easy. I am not going to use a piece of board. I am going to crimp gold-plated blade connectors directly to the + input leads of the capacitors and inductors and likewise for the outputs. I want a 2Ohm draw on the amp using 4Ohm drivers. I want about a 200wrms handling capacity, 100wrms for each high and low pass. My Q's are;

1. Would I select inductors and capacitors for 4Ohms (drivers) or 2Ohms (draw on amp)?

2. I guess I will be using Dayton's metallized polypropylene capacitors -decent prices-, what gauge of which kind of inductor should I use?

I have Part-Express's x-over value chart for 2 and 4Ohm. Any help is appreciated.

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haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: February 26, 2007 at 8:35 PM / IP Logged  
First off, impedance (2 or 4 ohms) isn't a "draw". It's a load. And if you can't get 2 ohm drivers, then you can't place a 2 ohm load on the amp, UNLESS you have a 4-channel amp, and are bridging it to 2 channels and running one 4 ohm set to each bridged pair. Even in this case, it is still a 4 ohm load, but the individual amplifier channels just "see" 2 ohms.
If you have 4 ohm drivers, then you will select crossover components for 4 ohms at 2500Hz.
At only 100 watts, then you could use any gauge inductor, but larger will be better, to an extent. I'd locate some middle-of-the-road priced 16 gauge inductors.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
stevdart 
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Location: Pennsylvania, United States
Posted: February 26, 2007 at 8:46 PM / IP Logged  

I recommend that you use some type of a board for stability.  And solder.  I would arrange the crossover components in a way that fits the space I have to put them in, drill holes through the mounting board and zip tie the components securely into position.  Then, use small lengths of primary 16 ga. wire to connect components, using solder for the connections.

If you have two coils in a crossover network, arrange them so that they are at 90 degrees.  The mounting board will stabilize their positions in regard to each other's.

Here is a depiction of 3 coils, each 90 degrees from the other two:

x over? -- posted image.

18 or 20 ga. air coils will be superior to what you would get in most commercial component crossovers.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
jmelton86 
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Posted: February 26, 2007 at 9:00 PM / IP Logged  

I thought that since the 4Ohm tweeter and 4Ohm woofer are wired in parallel, through the x-over, it would load the amp at 2Ohms... That's what I was unsure about. So for a 2Ohm system, I should use 2Ohm drivers? I want to use a 2Ch amp at 2Ohms stereo as to get out the most power.

I have read that by using a board and by using wires and solder to connect components, sound quality is compromised. Thats why I was going to crimp the components directly to each other. But since I'm not doing and all-out high powered install this shouln't be worried about, right?

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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: February 26, 2007 at 11:59 PM / IP Logged  

jmelton86 wrote:
I thought that since the 4Ohm tweeter and 4Ohm woofer are wired in parallel, through the x-over, it would load the amp at 2Ohms... That's what I was unsure about. So for a 2Ohm system, I should use 2Ohm drivers? I want to use a 2Ch amp at 2Ohms stereo as to get out the most power.

No, if a crossover is doing its job correctly the net average impedance load on the amplifier is the same as one speaker.  No, you should not use 2-ohm speakers (which you could not find anyway.)  Use 4-ohm speakers.

jmelton86 wrote:
I have read that by using a board and by using wires and solder to connect components, sound quality is compromised. Thats why I was going to crimp the components directly to each other. But since I'm not doing and all-out high powered install this shouln't be worried about, right?

Whoever told you that (or whatever you read) is wrong.  You should never just crimp connections in car audio if you can solder.  And it is never a good idea to have components like crossover parts just hanging from wires or bouncing around.  Use a board and solder your components together, no matter how "high powered" the system might be.

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jmelton86 
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Posted: March 01, 2007 at 7:43 PM / IP Logged  

Isn't solder inferior to two scuffed metal surfaces being securely held in place? I know solder is not an acceptable conductor, so why is it so highly regarded? Solder, to me, is more of a corrosion preventative. It simply covers the high-corrosion areas such as thin wires that are crimped or twisted together. Even silver solder isn't of audiophile quality to me - it usually only contains 4% silver content anyway!

DYohn, I agree to not have the crossover components bouncing around in the box. It is actually better to have the crossovers far from the speakers, closer to the amps I guess.

Stevdart, I agree that most-all commecially produced crossovers are crap.. Most of the time speakers suffer from inadequate crossover components and design. This is one of the most crucial parts of designing a SQ system.

Anyways let's get back to the topic. Alright say I was designing a 3way 1st-order(6db) x-over with points at about 32Hz and 3200Hz(Strong midrange!). The Q is; I would use the same values of caps and ind. for the midrange as I did for the high and low-range, correct? Also, which would I place first the cap or inductor? I figure the ind. b/c it can handle about 75wrms more, which would place less heat on the cap

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stevdart 
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Posted: March 01, 2007 at 9:23 PM / IP Logged  

Here is one good way to start learning about passive crossover design:  http://sound.westhost.com/lr-passive.htm

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
jmelton86 
Gold - Posts: 1,228
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Joined: February 07, 2007
Location: South Carolina, United States
Posted: March 01, 2007 at 10:28 PM / IP Logged  

I wrote:  Isn't solder inferior to two scuffed metal surfaces being securely held in place?

Stevdart wrote: No, not quite.  It IS what holds the surfaces in place.

Um, okay... So soldering is inferior to scuffing-up two metal surfaces then securing them together.

I wrote: I know solder is not an acceptable conductor

Stevdart wrote: Solder is the connector of choice... Crimp, then solder. Or in the case of wiring crossover components...twist, then solder.

Um, okay... So soldering is inferior to scuffing-up two metal surfaces then securing them together. -Solder is not a connector.  I said: It simply covers the high-corrosion areas such as thin wires that are crimped or twisted together.

 

I said: Stevdart, I agree that most-all commecially produced crossovers are crap.. Most of the time speakers suffer from inadequate crossover components and design. This is one of the most crucial parts of designing a SQ system.

Sorry, I got a little copy-and-paste happy! Thanx for the link, will read more into it as time will allow...

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stevdart 
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Posted: March 01, 2007 at 10:35 PM / IP Logged  
I deleted that but a little too late, it looks like.  I decided not to get into an argument with an idealist over such a basic principle.  You will understand, given enough study and experience, the importance of soldering in electronics.
Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: March 01, 2007 at 11:29 PM / IP Logged  
Soldering is superior to crimping in terms of quality of the electrical connection.  Period.  It has nothing to do with the audio signal quality.  It does not simply cover the connection for corrosion resistance, it can indeed form the connection unto itself and do so electrically perfectly.  To think otherwise is to be wrong.  How are PCBs assembled?
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