[cdgatti]

I was able to get some very good results with this tuning method so thought I would share it with the members. All aspects may not be applicable to you but some may.

My system:

hifi oem head unit
Helix DSP w/ urc 2a remote and apple airport express via optical
JL HD600/4 feeding morel mids/tweets (hybrid ovations and mt23 tweets) in the doors and kicker ssmb8 underseats. 150w/c
JL XD400/4 feeding rear BSW mid/tweets and an xtant 4" coaxial center speaker, 75 w/c rear, 200w bridged to center

Front door mids are high passed at 140Hz at 24db slope, center and rears are all high passed at 195Hz and 12db slope with LR filter
underseats are low passsed at 250Hz and high passed at 30Hz both at 12db slopes with butterworth filters.

I chose these crossovers because I want to keep distorting bass out of the small door speakers but at 140Hz they will pick up the first harmonic of 70Hz from the underseats and the kickers play well up to and higher than 300 Hz. I set all the EQ's up before starting on the time and phase alignment because eq changes affect phase. Using a calibrated mic and an RTA on the ipad I calibrated for a classic waterfall curve, the typical reference curve.

For the time alignment, sitting in the passenger seat I muted all speakers except the right mid/tweeter and the center. I pushed out the right mid/tweeter about 7" this centered the vocals for the passenger between the right mid and the center. I then sat in the driver seat and muted all speakers except the right and left mid/tweeters. I pushed out the left mid/tweeter ~17" to get the vocals right in front of me. I then turned my attention to the underseats, I played each underseat with the corresponding side mid with a 200 Hz sine wave. I had a RS SPL meter mounted in the drivers seat and adjusted the phase of each underseat to maximize spl while playing with the corresponding side mid. This ended up 0 degrees for the passenger and 67.5 degrees of phase for the drivers side underseat. SPL level is effected drastically as you vary the phase of the underseats from 0 to 360 degrees and a clear maximum is easily measured. I pushed the rears out as far as the Helix would allow, I think it is like 200"! I was trying to get the rears to make the car interior sound larger without being able to actually hear the rear speakers and I think this achieves this effect nicely. I configured the Helix DSP i/o matrix to have the underseats be 'subs' instead of woofers. Reason being this allowed the incremental phase adjustment I just described.


The results are fantastic, a solid center stage with very hard tight bass all up front. This method really makes the underseats' location impossible to detect. I am very pleased with the results and I have been around the block with this system quite a few times. Obviously the driver seat is great, but the passenger side isn't too bad, I think I found a nice compromise 2 seat tune.