what effect does a 4 driver have on an 8 ohm crossover?

[tinitus]

......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

 

[AllenB]

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.

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.

 

[tinitus]

ouch, a 100hz 'peak woofer', that would not be very nice

 

[AllenB]

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.

 

[60ndown]

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

 

[AllenB]

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?

 

[60ndown]

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........

 

[AllenB]

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.

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.

 

[tinitus]

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

 

[60ndown]

il be posting pictures soon

 

[60ndown]

well based on the knowledge i have acquired in this thread i decided to try connecting 2 pairs of 8 ohm speakers (now 16 ohm per side, or is it 4 ohms? +ve and -ve on each speaker pair joined)) to my already confused x-over and amp.

if my thinking is correct that would give me the steeper and lower cut off on the sub with a higher/shallower cut on the speakers?

(at 16 0hms, and shallower and lower at 4 ohms) ?

so instead of getting everything from 150hz and up, the speakers now get everything from about 300 hz and with a bit more volume??

or 75hz with less volume if its 4 ohms per side?

and i have a nice gap from 'about' 100-300hz (or 100-75) with an overlap??

lol, im not sure?,

i am listening to it now, seems *smoother* then with just 1 pair of speakers?,

i can hear something different, im not certain what i am/am not hearing tho

im am having fun .....

is it *illegal* to wire speakers in series?

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