Modification of Electronic Crossovers
15th May 2003
Alpine used to produce a 5-way e-x-over, model 3673, which consists of 2 high-pass, 2 band-pass and 1 low pass, all 12dB/oct.
I bought it around 1995 and only used it temporarily for a few weeks and left it. It was kept properly with box, plastic bags and manuals until today :)
The idea and objective is to modify it so that it will become 24dB/oct on the high-pass and band-pass, but sacrificing the 5-way into 3-way only. This is better as everyone could use stepper slope to achieve a cleaner sound separation and no true sound quality system use 5-way anyway.
At this point of technological age, 3-way is mandatory, 4-way is arguable (to be explained much later), and more than 4-way are simple a waste of all resources (i.e. design, effort, engineering, time, installation, etc)
Anyway, what I did was route the output from the 1st set of high-pass filter's output back into the 2nd set of high-pass filter manually. HARD-WIRE required and some points on the circuit board chain needs to be severed.
A total of 4 short wires required to perform the jump in signal and 4 points on the circuit board needs to be severed.
After the modification was complete, a series of serious measurement was taken to make sure the objective was meet.
and the results are: -
So pretty accurate I should say. To be honest I was surprise myself to it's easinest of modification and non-anomalies of signal routing error (my error I mean) or short circuit or whatever. Must have been lucky this time :)
Another note, the frequency indicator on the case is not very user friendly. What effective as 1kHz is so close to 1.3kHz on the case. See below.
As for the low pass is it left un-touched. By today's standards all amplifiers come with some sort of filter. I'm sure everyone can try to match the low pass frequency with this e-x-over and achieve another 24dB/oct and make the system a complete full 24dB/oct filtering.
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