Induction Compensation 2-way Filter

[Lars Clausen]

The benefit of a serial filter for 2 way speakers is, that the phase is in sync thoughout the crossover region. In real life use, it means that the loudspeaker plays horizontally at all tones, not like a normal filter sometimes the sound is better at the floor, other tones sound better at the ceiling of your living room.

One drawback is the serial filter's self resonance point. Normally it causes a peak in the area 1200 Hz - 3500 Hz. Attempting to solve this problem, i have come up with this idea:

A rather simple filter, that works in a speacial way. It uses the bass unit as a serial resistor to feed the tweeter's terminals only limited in frequency by the rather small inductor.
Now the bass unit is a coil, so it has induction, and thus would on it's own not give a straght frequency in the treble region.
This is compensated with the RC filter of 1 uF and 8 Ohms, so the result is a near-perfect resistor. The values may vary slightly depending on the inductance of the voice coil of the bass unit.

The ICX filter is rather simple to build, and you don't need very expensive parts to get a good result. It sounds great actually.
There are NO frequency peaks. However the filter has shallow slopes, so the quality of the drivers is of some importance.

Enjoy! Lars Clausen

[sreten]

I'm sure its works OK but to be pedantic it is not a 2 way crossover.

The bass unit does not have a 1st order electrical rolloff.

So it cannot have the resonance of a 2 way series crossover.

Some way of adjusting tweeter level should be included.

And it does not allow for baffle step compensation,
which IMO severely limits its general practicality.

Here's a similar design, 2.5 way to give BSC, more at :

http://www.lcaudio.dk/com/dele.htm

One of the advantages of series 1st order crossovers is
that its self compensating for bass unit inductance see :

http://sound.westhost.com/parallel-series.htm#1.2

sreten.

[Lars Clausen]

Thanks sreten.

I know that one, since i designed it a few years ago ;o)

Lars

[Lionel]

Hi Lars,
I'm really interested in your 2.5 way xover because I have nearly the same problem than the customer on LC audio site for a MTM configuration.
Do you know sites or DIY reports in which this type of crossover has been used.
It's look like a little bit "magic" to me and I haven't enough knowledge to understand it correctly.
But I think that it would a crime to not experience a such universal and simple solution.
Thank you for your comments.