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-   -   Designed my first crossover, tell me what you think, graphs inside (http://www.diyaudio.com/forums/multi-way/97591-designed-my-first-crossover-tell-me-what-you-think-graphs-inside.html)

pjpoes 6th March 2007 11:41 PM

Designed my first crossover, tell me what you think, graphs inside
 
2 Attachment(s)
ok so I designed my first crossover today, I'm trying to learn the various pieces of software I have. This ones is for a two way vented enclosure, about 18-19 liters. The woofer is a seas CB17RCY and the tweeter is a 27tbfc. I can't seem to export the schematic, so for now, I will just list the values. Oh yes its a series crossover, as long as I did everything right with the model anyway.

In the tweeter I have a second order crossover on the tweeter, sorta like a Bessel alignment. It has a 70uf capacitor and a .04mh inductor. Then it has a 1.6 ohm resistor before the tweeter in series, and a .04 series resistor after the tweeter. There is also a .15mh inductor in parallel and a 2ohm resistor in parallel. This helped get rid of the down sloping response of the tweeter, while still controlling a peak I had.

The woofer has a .75mh inductor and a 4.62uf capacitor. Then I have
a 13ohm resistor in parallel with the woofer.

So tell me what you think of the response curve. I know it still has some jaggies, but I think its well within what I have seen from others. I might try and get that tweeter cap value down and still keep the nice response. I will play with it.

pjpoes 7th March 2007 12:23 AM

2 Attachment(s)
ok since I posted that I have already made some changes, so the response is pretty much the same, I wont bother putting up another graph. However I have a really crude schematic I made in Word, which will ahve to do until I get a better way of making a schematic. I was able to change the values so get rid of the 70uf capacitor, and its not a series crossover. I thought I was modeling one, but I was wrong, so maybe next time.

Attached is the bad schematic. The new values are in the schematic.

owdi 7th March 2007 06:13 PM

Try using some of the FRD tools to model the baffle step, and combine that with the driver response. Then use the passive crossover designer to model your crossover, and see how it performs off axis. You will be surprised how much things change.

EDIT: R12 looks really low, have you modeled the impedance?

Dan

pjpoes 7th March 2007 07:06 PM

I did model the impedance, I will take another look. It may be too low, I basicly adjusted the value until the response looked good.

I will take your advice and try working with the baffle step compensation in the crossover, see how that works out. I didn't design this to build, it was for practice, so that I can learn the software, and get good at designing my own crossovers. All to often a driver comes out I want to try, but can't find a crossover that will work in the application I want.

For instance, I want to try making thing onwall speakers to use with my Flatpanel TV in the apartment I'm moving into. I want it to handle some power, have good dynamic range, and be designed around Theater use. I plan on copying the Totem design overall actually, but I think I will use 4 midbass drivers instead of 2. Thats a side issue though, I want to get better with this to start.

sreten 7th March 2007 07:07 PM

http://www.rjbaudio.com/Audiofiles/FRDtools.html

:)/sreten.

pjpoes 7th March 2007 07:28 PM

Ok I adjusted the values again and here is what I have now.

L2=.88
C2=1.58
R12=12.65

C9=7.91
L9=.31

r10=2.81
L11=5.86
C11=15.85
R15=11.94

Like this the imepance seems to be pretty flat around 5 or 6 ohms. It has a slight tilt from the woofer to tweeter, with peeks at two frequencies. The tweeter seems to be averaging around 8 and the woofer around 5, so I'm not sure if 6 is a good average. I can try adjusting the woofer to raise its impedance, but that seems to be where it's sticking, no matter what I do to the parts.

pjpoes 7th March 2007 08:16 PM

2 Attachment(s)
I should just stop posting, but I want to see what people think of it each time I make changes, to see if I'm getting a better design or going backwords. At the moment I have changed it once again and found a better design, I think, with a flatter response, and better impedance. I believe this to be about a 6ohm speaker, with a 4 ohm minimum, and a 18 ohm max, or so.

rabbitz 8th March 2007 12:09 PM

Have a look at the AR series xo's as they work extremely well.
http://www.acoustic-reality.com/ar-sxo2.htm

Have fun with your modelling but the fun doesn't really start until you start testing and listening.... can take months to fine tweak.

Enjoy.


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