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Old 5th June 2011, 04:48 AM   #21
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by AllenB View Post
......and text book component values as I would expect in this unit.
well, we assume a 150hz xo point, because it says so
its obviously a calculated xo
and we know for a fact that it would have delayed function in real life
low crossing inductors always needs to be bigger than calculated
sometimes quite a lot
and with such low xo point, even more

as said earlier, the 150hz xo point would be more likely to happen now, with 4ohm instead 8ohm

I would be very surpriced if it would be much lower than that
Allen, the very low xo point you show in the third graph is unlikely to be that low with such small inductors
thats why I question it
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Old 5th June 2011, 05:24 AM   #22
AllenB is offline AllenB  Australia
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There is something in what you are saying. I decided that I didn't feel the impedance I used for the sub was a good example so I changed to another woofer and this time I have displayed the impedance.

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Originally Posted by tinitus View Post
needs to be bigger than calculated sometimes
This being one of those sometimes cases as the impedance is falling at these low frequencies, not rising as it usually does near a crossover point.

The ideal plot is in green. 8 ohm is orange, 4 ohm is blue (same impedance plot used but filter Q halved), and the impedance is in grey.
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Old 5th June 2011, 06:12 AM   #23
tinitus is offline tinitus  Europe
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ouch, a 100hz 'peak woofer', that would not be very nice
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Old 5th June 2011, 06:58 AM   #24
AllenB is offline AllenB  Australia
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I agree. I found what looks like a 4 ohm driver with a lower resonance hoping this will be more helpful. I managed the second plot by more than halving the inductance and tripling the capacitance. The third has an inductor 2.6 times smaller and capacitance quadruple the original, as well as a resonance peak filter.
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Old 5th June 2011, 02:34 PM   #25
60ndown is offline 60ndown  United States
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sure wish i knew what parts to solder (and where to solder them) into my cheapo x over to make it perform like graph 3

currently it sounds pretty good, if there is a big peak at 100hz im not hearing it, i can hear some mids coming from the sub when i get close to it, from more then 6 feet away it sounds reasonably good,

but i wasn't expecting too much for my $8.

typically im a fan of a sub that plays nothing above 60 hz

Last edited by 60ndown; 5th June 2011 at 02:37 PM.
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Old 5th June 2011, 02:56 PM   #26
AllenB is offline AllenB  Australia
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Room modes are playing a big part at these frequencies and peaks like that may or may not turn out to be significant on their own by comparison. Room placement makes changes easily this big. Have you ventured into the world of multiple sub placements to balance the bass?
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Old 5th June 2011, 03:12 PM   #27
60ndown is offline 60ndown  United States
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Quote:
Originally Posted by AllenB View Post
Room modes are playing a big part at these frequencies and peaks like that may or may not turn out to be significant on their own by comparison. Room placement makes changes easily this big. Have you ventured into the world of multiple sub placements to balance the bass?
interesting,

no 'multiple sub' arrangements for me yet........
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Old 5th June 2011, 03:36 PM   #28
AllenB is offline AllenB  Australia
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If you happen to have two for stereo anyway, try putting one in a corner and one halfway along one of the walls, then try swapping + and - for each of the subs one at a time.

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Originally Posted by 60ndown View Post
sure wish i knew what parts to solder (and where to solder them) into my cheapo x over to make it perform like graph 3
Since you asked...but these values may not quite work for your woofer.
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Old 5th June 2011, 03:57 PM   #29
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by AllenB View Post
Room modes are playing a big part at these frequencies
definately yes
you may have severe 'suckout' at very narrow frequency
or even excessive room gain right next beside it

take everything with 'some' precaution
whether its something being said, claimed, or simulated
or even real time measurements showing perfection may not sound like that at all to your ears, or in your room

sound is tricky, music even more

that said, no one wouldn't normally try to do a passively crossed sub
at least not anyone around here
but if so, a bandpass design ought to have better chances
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Old 5th June 2011, 04:51 PM   #30
60ndown is offline 60ndown  United States
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il be posting pictures soon
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