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Old 4th January 2013, 08:35 AM   #1
ODougbo is offline ODougbo  United States
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Default Canned Crossover Design - What Next?

This started on the Full Range page; TB W5 8ohm driver. Guitar and Bass strings sound great but lacking high end, especially with coat of silicon.

Trying to lean a bit about xo's - very intriguing. I've always known enough to call Madisound, if I wanted something that worked properly.

Lots of on-line ox calculator sites, Second order Butterworth looks straightforward. I can see why some say to use same impedance drivers (tweeter on right is 8ohm, so is woofer).

I did have enough parts to listen to them; xo as shown.

Where do I go from here?


Some box construction plans here:
W5-1611 SAF - The Sequel
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Old 4th January 2013, 10:26 AM   #2
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Ok where to start. The first thing to learn is that text book xo will almost never be right. Measure the impedance of the drivers in the cabinet! Second it is the acoustic slope that matters not the electrical.

Check out the excellent sticky. Designing without measurements for a good grounding!

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Old 4th January 2013, 11:00 PM   #3
ODougbo is offline ODougbo  United States
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I might be able to get a buddy to help measure the impedance (tomorrow)

So far some songs are sounding very nice. However the woofer is not rolling off at 2200hz, still going to 3500hz or so. (I didn't think the woofer would roll off easily)

The tweeter roll off is close, however to loud.
L-Pad (now) R1= 1.0 ohm R2= 50ohm
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Old 4th January 2013, 11:50 PM   #4
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Based on the spec sheet http://www.parts-express.com/pdf/264-898s.pdf , it looks like the woofers have an impedance of around 10 ohms at 2200 and have risen to around 14 ohms by 20Khz.... did you do your calculations based on 8 ohms nominal impedance?

Some impedance compensation will probably help (if you don't have acoustic measurements and simulation capabilities).

Also it looks like the woofers FR starts rising at around 1Khz and is about 5db hotter at 10Khz. factor in baffle step as well and you could be around 9db higher (on the TB) from about 3Khz up than you are from 100 - 1000 Hz!

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Old 4th January 2013, 11:57 PM   #5
ODougbo is offline ODougbo  United States
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Sorry - should have posted this - this one is:

http://www.parts-express.com/pedocs/...ifications.pdf
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Old 5th January 2013, 12:14 AM   #6
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ok that doesn't have the same rising response, but the impedance is even higher than 10ohms at 2200 It's a bit hard to see on that graph exactly what it is though, since it seems to be a log scale on the impedance, and the lines don't match up with discreet impedance values. If you can get an actual impedance measurement that would be best.

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Old 5th January 2013, 08:48 PM   #7
ODougbo is offline ODougbo  United States
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Bought them to the "good room"; better but there is a RRRRRR sound in the midrange.

The chart is hard to read, I'm thinking the impedance is around 13ohm.

Went to a on-line Zobel site - for idea what I need.
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Old 6th January 2013, 09:50 AM   #8
ODougbo is offline ODougbo  United States
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Going to try Linkwitz-Riley xo (flat midrange response)

Butterworth has a rise in the midrange.
I'll to that!

This has been a good exercise
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Old 6th January 2013, 12:29 PM   #9
Dissi is offline Dissi  Switzerland
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Quote:
Originally Posted by ODougbo View Post
Where do I go from here?
The baffle step causes a rising frequency response in the midrange and demands a larger coil to compensate. According to a simulation 1.5 mH and 12 uF could work. The target function is a 3rd order Butterworth low-pass filter having -6 dB at 2.2 kHz:

SimulationODougboTB.jpg
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Old 6th January 2013, 01:55 PM   #10
ODougbo is offline ODougbo  United States
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Dissi thanks!

I was busy this morning and made up new 1.1 coils. HUGE improvement in middle - however still needs work.

Btw, the tweeter L-pad is just cracked open 1/16 of a turn and tweeters are just wailing away

The bass is crazy nice!!!! they have potential if the xo can be resolved and/or buy different tweeters. [they are old but working/clear]

* the volume is not turned up much on pre-amp either, just a bump i.e. plenty loud.
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Last edited by ODougbo; 6th January 2013 at 02:17 PM.
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