simple speaker question

[sakis]

simple as that

i am planing to construct a pair of speakers nothing fancy 2way speakers 8'' visaton and a tonsil tweeter front of the enclosure will be flat

the question is about the xover
in the enclosures that are front flat and tweeter is above the woofer over the same axis what is the best way to go ???


possible choises can be
1-6db/Octave - Phase Shift: 90°
2-12db/Octave - ( dont know how much pahse shift is there )
3-18db/Octave - Phase Shift: 270° (-90°)
4-24db/Octave - Phase Shift: 360° (0°, No Phase Shift)....


any ideas ???

[Chris Daly]

As the speaker is just two way, use a 6db per octave xover ,
Use an inductor in series with the bass driver and a zobel network to help stability. and for the tweeter a variable hiwatt resistor to match the required output ( you can then use fixed values once it is measured and it sounds right ) and a use a series capacitor for the tweeter

Although lacking a Zobel network, the schematic here is a well trusted design the AR4x courtesy of The Classic Speaker pages :

AR-4x Schematic | The Classic Speaker Pages

Hope this helps / Chris

[sakis]

thanks for a quick response

this actually dosnt look very promising and also doesnt answer my question about phase shifts

then again i was looking for something more sharp and more sophisticated
previously in a similar set up i used a second order for the woofer and a third order for the tweeter and results where very nice ...

still this is what me ears say and some guidance from a theroetical approach

[Arty]

2nd order filter.
You flip the polarity of the tweeter, therefore cancel the 180 degree phase shift.
(not absolute correct technicaly, but its in a nutshell only)
this is how you can do it.
for 8" woofer 1st order filter requires a verry high overlap between usable driver response.
so it is out of question.
4th order would work allso, but the tolerance for components would be far too demanding to worth it compared to a 2nd order.
if you want to do something exotic you might try a 2nd order series crossover.

[sakis]

ok then ... theoretically is it ok to have 12db/2nd order /180 phase shift with the polarity inverted in an enclosure that is flat front ?

[Jay]

Originally Posted by sakis

the question is about the xover
in the enclosures that are front flat and tweeter is above the woofer over the same axis what is the best way to go ???


possible choises can be
1-6db/Octave - Phase Shift: 90°
2-12db/Octave - ( dont know how much pahse shift is there )
3-18db/Octave - Phase Shift: 270° (-90°)
4-24db/Octave - Phase Shift: 360° (0°, No Phase Shift)....


any ideas ???

For sophisticated speaker, "theoretical" formula do not work. Acoustical slope is different with electrical slope. Phase is also not simple. Even measurements do not enough.

The best way will be to try prototyping many filters and choose the best one based on listening. Golden ears are the most important tool.

Only by measuring the drivers, possible filters along with the order can be prepared. First order parallel filter 99.99% will not work. First order series filter should be tried if the drivers smooth enough.

Second order parallel filter should be investigated most carefully as for a 2-way, when it is possible (phase-wise), will often produce a very good sounding (sonically enjoyable) speaker.

Higher order filters really need good ears as it is easy to build something that measured good but sound nothing special.

[Arty]

Originally Posted by sakis

ok then ... theoretically is it ok to have 12db/2nd order /180 phase shift with the polarity inverted in an enclosure that is flat front ?

it is a simple and effective solution, yes.
still hard to make, as any xover.
probably 2nd order is best trade off outta there.

[Francec]

Or go the active route. It will make making sensitivities easier and with 24dB slopes, you won't have to worry about the drivers' roll-offs if the crossover frequency allows sufficient overlap.
PLUS, it will sound better.

Frank