Changing Woofer Impedance.....

[Mike33]

If i go from an 8 ohm woofer to a 4 ohm woofer in an 8 ohm cabinet will it workout ok?
Curious because i have an extra set of drivers that i would have to modify the cabinet in order to place them in.
Thanks.

[Mr. Widget]

It will work fine as long as it is the same woofer model or has the same TS parameters and you are using an active crossover or will change the passive one.


Simple isn't it?

A more specific question would lead to a more specific answer, but in general if you asking can any 12" woofer be dropped into an L100 for example the answer is typically no.


Widget

[Mike33]

Ok thanks, what will the effect be without an active crossover?

[Mr. Widget]

There are two issues here. A woofer's performance is based on the tuning of the cabinet... that's why I said you need similar TS specs or an identical woofer with a different impedance.

Of course to some extent you can change the tuning of a ported system... however a sealed 2 cu ft box can never be bigger without serious surgery.

The second issue is that a speaker's impedance will determine how it interacts with a passive crossover filter. At the simplest example a 4 ohm woofer will cross over at half the frequency of an 8 ohm woofer if there is no modification to the network... for anything but the simplest networks this isn't exactly true, but it is close enough.


Widget

[duaneage]

It would be easier if we knew what your were going to and from.

Some drivers may be rated at 4 ohms but in reality they have an impedance curve and are not flat like a resistor.

Woofers hae large voice coils which act like the inductors in a crossover. The woofer has it's minimum impedance around 100-150 Hz. The impedance rises steadily until it reaches 15-20 ohms at 20Khz. A 4 ohm driver MIGHT have an impedance of 6 or even 8 ohms at your midrange crossover frequency. Typically the impedance rating is the minimum value since amplifiers musst be protected against low resistances.