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Old 14th October 2010, 12:41 PM   #11
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I'm still curious about the influence of coils rdc vs crossover's slope and woofer behaviour!
Download Passive Crossover Designer (free) and play. But if you are lazy here are some results: at 200Hz moving from 0,17 to 0,5 Ohm the SPL will be lowered by 0,4 dB, at 100Hz and 1KHz the difference is only of 0,1 dB. I frankly doubt that you can hear 0,4 dB in a blind test.

For a woofer like the scan-speak I would opt for an air core inductor. Large value inductors with large diameter wire are expensive, but a 2,7mH 2,0mm (0,33 ohm dcr) air core inductor costs about 50 Euro, that is a fraction of the cost of the woofer. You can try a lower cost ferrite core and decide if you hear the difference (you can find a 0,1-0,3 ohm ferrite core inductor in the 5-15 euro range).

Ralf
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Old 14th October 2010, 05:26 PM   #12
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Originally Posted by jwmbro View Post
If the DC-resistance is too low, that's easy to fix. Just ad a series resistor to bring it up to the desired resistance. Simple addition of resistances when in series.
Yep - better advice than mine - i was hung up on modifying an existing coil.
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Old 14th October 2010, 09:46 PM   #13
tamule is offline tamule  United States
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You wrote that in your speaker you use an (huge) AIR coil. This coils are really expensive and really thick wired... why have you choosen this way and not a cored coil?
Are ferrite core/transformer coils not enought for your purposes? Do you think that the difference (distortion, core saturation) is worth the extra expense?

yes -they were expensive and worth it. I wanted air-core after reading about hysteresis losses and the ability of coil to change it's magnetic field with the signal. As long the desired DCR was met-I was willing to pay.
I wonder if any hi-end manufacturer uses 5- 8 lb inductors with their woofers?
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Old 14th October 2010, 09:54 PM   #14
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Thanks!
I'll try with an inexpensive ferrite core (low rdc) and then, once found the right amount of bsc and the impedance i want, i'll spend more money and go for air inductors. I think mundorf air coils, 2,5 or 3 mm.
Flat foil inductor are way expensive, don't know if it's wort the results... round wire should do a nice work anyway.
Choosing the right balance for crossover components is ever a pain for me. I'm tempted by high-end stuff, but I don't want to waste my money if the results are totally marginal or if I could spend it more effectively for more important parts of the speaker. (wiring, binding posts, "exotic" damping sheets, etc etc.)

Last edited by francorovereto; 14th October 2010 at 09:58 PM.
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Old 14th October 2010, 10:13 PM   #15
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ps: what about the question n. 1? How should I consider the baffle widht/height adding a consistent roundover to the edges?

In this case, should I consider to mantain the original (given) widht on A,B or C?
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Old 14th October 2010, 10:14 PM   #16
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Ps: You all are very nice answering patiently to my doubts.
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Old 15th October 2010, 07:07 AM   #17
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The width/height is C.

Ralf
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Old 16th October 2010, 09:45 PM   #18
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The answer is: C! Thanks. But let me be "avvocato del diavolo" for a minute.
Giralfino you say that the significant dimension is taken when the edge's curve reach 90 degrees, perpendicular to baffle. In this forum I have read in some debates that first diffraction effects begins to appear before reaching c, but the transiction to full radiation is way smoother.
Ok. But:
Given a bsc designed for a sharp edge (with "C" dimensions), the resulting diffraction behaviour of a rounded edge should be a little different I guess. Maybe a resulting smooth dip/peak in the response?
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Old 17th October 2010, 08:45 PM   #19
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Anyone here?
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Old 6th November 2010, 12:57 PM   #20
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