1st order to 4th order conversion

[Professor smith]

In a 2 way speaker with a 1st order crossover how easily can I convert it to 4th order? what considerations are there?

[speaker dave]

Add 3 orders?

Every order adds 90 degrees ultimate phase roatation, but only half of that will be seen at the crossover point. Adding 3 orders will advance your tweeter response 135 degrees and retard the woofer response 135 degrees. Hard to say if they will add well after that. Also note that as crossovers go higher order the design gets more complex and the ability to get sections to add smoothly is harder. Are we doing proper design here with network simulation and good measurments to guide the process, or just guessing a network?

You can't guess a 4th order network and expect to get lucky.

David S.

[Charles Darwin]

Don't forget the 1st order shift which is already there in the originals so the total shift with a 4th order network would be 360deg between tweet and woof.

[speaker dave]

3 x 45 = 135 for each section. So 270 degree total additional change which is the same as a 90 degree relative spread, assuming the units were well in phase to begin with.

David

[jerome69]

Originally Posted by Professor smith

In a 2 way speaker with a 1st order crossover how easily can I convert it to 4th order? what considerations are there?

Too long to explain, too many cases.
It's better to give more information : drivers reference, drivers diameter.
The problem is to know the final acoustic slope 1st/2nd or 4th/6th.

This is an exemple of conversion of a njord kit like
It was done with measurements and I try to get the best of the drivers.

[Professor smith]

why cant you just use the same crossover point and make the crossover slope a fourth order? do you have to change the mounting point of the drive units?

[jerome69]

Originally Posted by Professor smith

why cant you just use the same crossover point and make the crossover slope a fourth order?

Why not ?
It's better to stay in a linear range...
Low order crossover : high point of crossover to protect the tweeter, because of its resonance
Higher order, lower the point of crossover to be in a better pistonic range for the woofer

Originally Posted by Professor smith

do you have to change the mounting point of the drive units?

Not necessarily

[Charles Darwin]

Originally Posted by speaker dave

3 x 45 = 135 for each section. So 270 degree total additional change which is the same as a 90 degree relative spread, assuming the units were well in phase to begin with.

David

Somewhat unlikely since most manufacturers (I assume ready-built speakers here) use 1st order so they don't have to bother with phase alignment.
The usual argument goes that 1st order phase shift is too small to be audible.

[Professor smith]

what does cone breakup sound like?

[speaker dave]

The 1st order electrical filter may have relatively small phase shift but that isn't the whole picture. The total acoustical phase shift is always the issue, and it is the combination of electrical phase shift and phase shift from interunit time delay. Drivers with first order filters aren't guaranteed to add up unless the driver depth is just right. This is why the ideal crossover slope is more a function of the particular drivers you have chosen than any notions of best phase response.

David