Need Crossover!
Aug 16, 2003 at 1:50 PM Thread Starter Post #1 of 18
Czilla9000

Czilla9000

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Hello, I need a crossover @ 400 Hz for some speakers I am building. Anyone know of a good one?
I assume I just solder some wire from the binding posts to the crossover and too the drivers to connect it?


In terms of enclosures.....the driver sizes I am using are, I am guessing, pretty uncommon. Looks like I will have to put together my own cabinet. What supplies do I need to do it?

Last question - for now
biggrin.gif
- how do I measure freq. response?


Thanks a bunch.
 
Aug 16, 2003 at 6:32 PM Post #2 of 18
The crossover, I found out, can be anywhere from 200Hz to 500Hz.

The drivers I am using are the Jordan JX53
extented range driver for 30KHz to about 400 Hz and the Jordan JX150 for 400Hz down to 25Hz.

The Jordan JX53 comes in a rectangular chassis, making my enclousure work hard.
 
Aug 16, 2003 at 7:52 PM Post #3 of 18
Contact Paul at Parts express, on the technical forum section, he is a nice guy and can give you a hand with the crossover, one already made or some ideas to go DIY....
 
Aug 16, 2003 at 8:43 PM Post #4 of 18
That's good advice. I'd also recommend buying one of the pre-built cabinets at PartsExpress. They're very good looking -- all you need to do is cut holes in the front panel (and cut a port if you want one) plus add damping material.

You should also really consider using the crossover designs that Jordan provides on their website. They're very simple and (naturally) designed for the Jordan drivers.
 
Aug 17, 2003 at 5:03 AM Post #5 of 18
Thanks guys.


One problem......I still do not know how to read electrical diagrams.


Here is the diagram for one of their crossovers.


JX53crossover.gif
 
Aug 17, 2003 at 5:57 AM Post #6 of 18
They're not using completely standard schematic symbols anyway. The things marked "mF" are capacitors, the thing marked "mH" is an inductor, and the things marked "R" are resistors. However, it's hard to tell what "R" means. My guess is that "15 R" means 15 ohms and their drawing package just didn't support the omega symbol. I don't know what "4 R 7" means. Perhaps 4.7 ohms. You might have to email them about that.
 
Aug 17, 2003 at 6:11 AM Post #7 of 18
The "R" notation is mainly a European thing. You also used to see it in North American drawings, but it went out in the 50's. R is used as a suffix and a substitute for the decimal in values under 1000 ohms. So, 15R is 15 ohms, 4R7 is 4.7 ohms. In that scheme, you'd also see things like 2K7 where the more recent practice would be to say 2.7K.

I see they've also used "mF". You might think that this is milliFarads, but way back in the day, this actually meant microFarads, before Greek mu's were easy to print, and before people started using 'u' as an approximation for a mu.

Someone should extend them an invitation to join the 21st century.
smily_headphones1.gif
 
Aug 17, 2003 at 7:37 AM Post #8 of 18
So I need a cap with 4.7 MICROFarads- not milliFarads?





Which Parts Express enclosure size do I need, and what tools do I need to cut holes?



Thanks again.
 
Aug 17, 2003 at 8:00 AM Post #9 of 18
Interesting, Tangent! I learn something new every day.

Czilla9000, yes, you want microfarads (uF) for both capacitors.

I'd follow the cabinet size recommendations given on Jordan's web site. Remember, shape largely doesn't matter, only volume. It looks like many of the designs on the Jordan site are sealed, not ported, which is convenient. Makes life easier.

There are many ways to cut large circles. If you have a router it's pretty easy, but you may need to buy a template to keep the router from veering off-course. If you're going for the bargain-basement approach, you can use a regular drill with a rasp bit then a lot of elbow grease with a round file.
 
Aug 17, 2003 at 9:03 AM Post #10 of 18
Quote:

So I need a cap with 4.7 MICROFarads- not milliFarads?


I'd ask someone who knows to be sure, but it's a reasonable guess. I can't imagine using a 4700uF cap in a signal path.
 
Aug 17, 2003 at 2:00 PM Post #11 of 18
4.7 uF is correct. Use polyester or polypropylene film caps. The 50 uF (47uF) could be a film cap (better quality, but expensive & huge!) or a bipolar electrolytic cap meant for crossovers (not as good quality-wise, but cheaper and a lot smaller). Tangent is right about the "m" meaning microfarads in older schematics. Capacitor values in loudspeaker crossovers very rarely stray outside the 1-100 uF range.

Substituting the decimal point with "R" or "K" (for ohms/kiloohms respectively) was/is done to prevent errors when reading the parts values (i.e. the comma/decimal point is very easy to miss). Similarly, you'll see capacitor values written as 4n7 og 4u7 in some schematics (and some of my posts...
tongue.gif
).


/U.
 
Aug 17, 2003 at 2:05 PM Post #12 of 18
Quote:

Originally posted by Wodgy
There are many ways to cut large circles. If you have a router it's pretty easy, but you may need to buy a template to keep the router from veering off-course. If you're going for the bargain-basement approach, you can use a regular drill with a rasp bit then a lot of elbow grease with a round file.


The router is the most elegant solution, but requires some practice. I'd buy (borrow/rent/whatever) a jigsaw (preferably with variable speed). That doesn't have to cost you an arm and a leg, and could be used for other things as well.

/U.
 
Aug 17, 2003 at 2:16 PM Post #13 of 18
The best solution IMO if you do not have the practice is to contact any of the "DIY" speaker parts sellers and sometimes manufacturers like Zalytron, Partsexpress, Madisound, Speakercity, and as the Partexpress fronts are detachable, you can send them to be cut in their places, I did that once with Men-is-cus (meniscus audio group, phone: (616) 535-7676) for a subwoofer baffle I was making as I have no clue of how to use a router, and they did an excellent job, and free, I just had to paid for shipping, about 15.00 and the job was done neat and clean
 
Aug 18, 2003 at 8:10 AM Post #14 of 18
What WATT level do I need for the resistors.....10 watt? What voltage level for the caps?
 
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