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Old 19th April 2004, 03:22 AM   #1
Zymrgy is offline Zymrgy  United States
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Default yet another crossover question

I am still very green here...I feel that I am learning more & more with every thread that I read. I am finally goign to make my first "real" project, a centerchannel based on this design http://home.hetnet.nl/~geenius/USB.html

I am planning on adding a second 6.5" driver & using it as a 2.5 way speaker. ( w/coax/port ) my plan is...that if it turns out as good as I hope, is to make 2 more for all 3 front speakers.

I like the simplicity of the crossover that Tony Gee came up with, yet I am having trouble deciding what the crossover points actually are? I know that decideing the point is something very critical with speaker design, and I want to fully understand what I am getting into.

From what I gather, adding a ".5" speaker to this would not complicate things much. I am thinking of just a simple 1st order, say at about 250hz.

just looking for comments/suggestions.

Thanks all!!!
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Old 19th April 2004, 06:15 AM   #2
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Default Coax

Hi Zymrgy,
I think the whole point of the coax design is to provide a single coherent point source of propagation. Adding another woofer somewhat defeats this purpose, though less so in a .5 compliment, you would still have some interaction from the two woofers.

The other matter is adding the .5 components to the crossover.
Tony is using a series crossover that will not allow the .5 addition in series, but as a separate parallel leg. Plus I believe he mentioned including baffle step in the original, which would have to be reworked if the second woofer is added. Another deviation from the original intent, which was to keep it simple.

I just don't know if it is worth doing if the present design sounds good and does what it was intended to do - sound like a single driver.

Tim
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Old 19th April 2004, 10:52 AM   #3
sreten is offline sreten  United Kingdom
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The design already includes baffle step compensation
so adding another 0.5 unit will not work well at all.

Complete redesign of the crossover is required,
the tweeter level needing to be set ~ 6dB higher,
and the BSC removed form the driver.

It should make a fine centre channel speaker.

The porting arrangement is more show than go IMO
and could easily be simplified to a single rear port.
As is the edge detail on the baffle, easily ignored.


sreten.
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Old 24th April 2004, 05:49 PM   #4
Zymrgy is offline Zymrgy  United States
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ok...after doing much more research I am getting more lost....ahhh...the joys of learning. The books I have on crossovers (namely the Loudspeaker Design Cookbook ) pretty much deal with parallel crossovers....and with my limited electrical knowlege...looking at a series schematic blows my knowlege away.

That being said....I am still interesting in doing a 2.5 way system. 3 parallel filters are pretty straight forward....till I start asking about impedence. for now...lets assume that I am leaving the tweeter out of the equasion. lets say that I want to have the "main" driver cutting off at 3000 Hz, and the ".5" driver dropping off at 300 Hz. both are 8 ohm speakers & both with 6db slopes on the crossovers.

the coil on the main driver would be .42mH
the one on the .5 driver would be 4.25 mH

now again...with my limited electrical knowlege..I am thinking that the load the amp will see will be 4ohm or slighlty less. I am comfortable with this load....yet I do not want to drop any lower. The big question is.....what happens when I add the 6ohm tweeter into the mix? (yet another parallel circut)

having fun with this...Thanks again!
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Old 3rd May 2004, 03:48 AM   #5
Zymrgy is offline Zymrgy  United States
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still lost on this one...

anyone got links to some examples of a 2.5 way crossover?

Thanks.
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Old 3rd May 2004, 11:23 AM   #6
delwon is offline delwon  United States
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Zymrgy,
Try this for starters. Put that .42mH coil in series with your main woofer. Now put that 4.2mH coil between the positive terminal of the main woofer and the positive terminal of the .5 woofer. Wire the negative terminals in parallel, that is negative to negative. Even though the woofers are in parallel, your load is 8 ohms due to the transfer function of the xovers. When you add a 6 ohm tweeter to the mix, I believe you overall load becomes 6 ohms.
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Old 3rd May 2004, 04:19 PM   #7
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Quote:
Originally posted by Zymrgy

now again...with my limited electrical knowlege..I am thinking that the load the amp will see will be 4ohm or slighlty less. I am comfortable with this load....yet I do not want to drop any lower. The big question is.....what happens when I add the 6ohm tweeter into the mix? (yet another parallel circut)
You are essentially correct. There will be a 4 ohm load until the .5 woofer starts rolling off due to the 4.2mh. The impedance will then slowly rise until it reaches 8 ohms. It will stay that way until 3000Hz where the impedance will start to change to 6 ohms. All this give or take and based on resistive loads.
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Old 4th May 2004, 03:46 AM   #8
Zymrgy is offline Zymrgy  United States
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ok...I am thinking I am getting close to my "final" design for the crossover.

let me know what ya all think. (Sorry for my crude schematic skills)

Click the image to open in full size.


Thanks for all the input
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Old 8th May 2004, 03:29 PM   #9
Zymrgy is offline Zymrgy  United States
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ok...I thought of a slightly different way of wiring the low pass section....but I think I a getting the exact same result.

Opinions???
Attached Images
File Type: jpg crossover2.jpg (26.4 KB, 144 views)
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Old 11th May 2004, 12:08 PM   #10
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Default Slightly offtopic...

I'm looking for the high res drawings for this speaker. I mailed Tony Gee but didn't get a reply?
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