I am currently in the process of activating a pair of old JBL 4622N cinema speakers for home stereo use but I'm facing some strange issues. I got these for almost nothing and I am not yet willing to let 'em go.
These are dual 15 inch woofers + big horn (JBL 2384) units. The original passive design is a classic 2-way with both woofers running in parallel and a crossover at approx. 700 Hz to the horn. This might work well for really large listening distances like you find in a typical theatre but I found very disadvantageous in a home environment, seeing huge vertical cancellations/lobing below 700 Hz.
Now my idea was to go fully active and 2.5-way, meaning the lower woofer will gradually fade out above the lower bass frequencies. The upper one will also do the mid part up to ~ 600 Hz.
So here is what I tried:
First with tons of parametric EQs I linearized all the drivers so they measured flat to at least and octave above / below the crossover. Then I crossed over both woofers at 600 Hz (LR24). The lower one goes through an additional 6 dB/oct first order low pass at 360 Hz and 6 dB attenuation . The upper woofer goes through a corresponding -6 dB shelving low pass so that their output adds to 0 dB. At the crossover frequency the lower woofer is now ~ 10 dB down.
In theory this should look something like this:
Now my problem is that I still see these massive on axis cancellations at ear height a few meters away from the speaker. There is a very wide 7 dB-dip between 100 Hz and 400 Hz. Only if I put some delay on the upper woofer/tweeter this goes away somewhat. Shouldn't there only be 90 degree phase shift between the woofers anyway? I don't see where these enormous phase issues stem from. How is this usually done in practice? I see tons of speakers with multiple bass drivers which should result in massive lobing if my observations are correct.
These are dual 15 inch woofers + big horn (JBL 2384) units. The original passive design is a classic 2-way with both woofers running in parallel and a crossover at approx. 700 Hz to the horn. This might work well for really large listening distances like you find in a typical theatre but I found very disadvantageous in a home environment, seeing huge vertical cancellations/lobing below 700 Hz.
Now my idea was to go fully active and 2.5-way, meaning the lower woofer will gradually fade out above the lower bass frequencies. The upper one will also do the mid part up to ~ 600 Hz.
So here is what I tried:
First with tons of parametric EQs I linearized all the drivers so they measured flat to at least and octave above / below the crossover. Then I crossed over both woofers at 600 Hz (LR24). The lower one goes through an additional 6 dB/oct first order low pass at 360 Hz and 6 dB attenuation . The upper woofer goes through a corresponding -6 dB shelving low pass so that their output adds to 0 dB. At the crossover frequency the lower woofer is now ~ 10 dB down.
In theory this should look something like this:
Now my problem is that I still see these massive on axis cancellations at ear height a few meters away from the speaker. There is a very wide 7 dB-dip between 100 Hz and 400 Hz. Only if I put some delay on the upper woofer/tweeter this goes away somewhat. Shouldn't there only be 90 degree phase shift between the woofers anyway? I don't see where these enormous phase issues stem from. How is this usually done in practice? I see tons of speakers with multiple bass drivers which should result in massive lobing if my observations are correct.