I really wanted to upload this one because it's made me think a LOT over the years, and things I learned here STILL have implications on things I want to do in future installs - including my current build.
This was a budget build, really a strong bang-for-the-buck achievement here.
This was a winter beater I had shipped up from Florida - only 2wd 5 speed Pathfinder I could find on the planet. I wanted to lower it to handle like a car - I gave it a pretty mild drop, but that was still something like a 4"/6" drop believe it or not.
(prior winterbeater was a slammed 5 speed, 4 cylinder Nissan Hardbody and I loved it)
Everyone was starting to go all-active in car audio, but that's not even a THING in the home audio world. So I reacted, wanted to explore AGAINST the trend - wanted to play with an all-PASSIVE install. So that was one part of the experiment.
It's not exactly "scientific method" to do two experimental things at one time... but what the hell.
Part two of the experiment - the bigger part - was doing a phase-aligned line-array.
"What the hell is that?"
For those who don't know, this is a line array:
It's those unbelievably huge and expensive vertical hanging arrays of speakers on the side of huge concert stages. And no - that sure as hell is neither "car audio" nor "budget".
Hold that thought.
The thing about line arrays is - the speakers are close-coupled enough that their energy combines - it allows sound at a concert to travel further, because it's stronger - so even the hippies dancing out back in the standing area get good sound too.
The other thing about line arrays is - you are not supposed to listen to them in the near-field (up close), because when you are close to them, the energy does not combine -
Look at that picture there, again - it was taken up close. You are MUCH closer to the bottom speakers on the array than the top speakers, and that means - depending on the wavelengths of the frequencies - some frequencies will combine just fine because they happen to line up, while others will cancel, because the pathlength differences just line up so that a positive pressure wave from the top reaches you as a negative pressure wave from the bottom reaches you - that's what pathlength distance differences do.
And it's exactly why car audio is difficult - you are seated in an offset position in the car. The sound from the left speaker is a different distance from you than the right speaker - that difference makes the sound arrive at different times, and will cause cancellation (Google what a "comb filter effect" is) periodically across the whole frequency spectrum.
On top of that, you have direct vs reflected sound... the direct sound has a direct path distance to your ears, but the sound also travels in all directions and bounces off your windshield, then reaches your ears. And bounces off your side glass, and reaches your ears. And bounces off your dashboard, and reaches your ears. Etc. So your primary sound has to fight the sound coming from these reflections, as well!
So my thought was this:
What if we could re-enforce the primary sound, making it stronger - like a line array does? Making the primary sound louder relative to the reflected sound would be one way to mitigate those cancellations.
And if the issue with line arrays in the near field is that the pathlength distances are different - what if we addressed that by making them all the same? Wouldn't that phase-align them?
And what better vehicle to do this pathlength-aligning finding in than a Pathfinder?
Seriously though, this was a good vehicle for that because the door panels were really simple, more like door cards. What I did was cut away the portion of the door panel I didn't want to use, and added a plain old flat piece of MDF (or plywood, I probably used plywood for the weather concern) there.
I then took a string and tied it to the middle of a stick, and suspended that exactly between my two headrests.
On the other end of the string, I took a pencil, and drew arcs using that string, on the MDF. Along any of those curves, if speakers were mounted - no matter how many - the arrival times to your ears would be the same.
So after sampling a bunch of inexpensive wideband speakers from Parts Express, I settled on these... I think they were $20-ish Tang Band 2.5" or 3" speakers with a phase plug. I mounted three of them per side, in a time-aligned arc.
I also used two 5.25" decently high-excursion (and cheap) midbass drivers per side:
And it actually worked - my imaging was fantastic.
It also had surprising stage width - well past the sides, wider than really ANY car I've heard before... and I've heard a lot.
I believe that's because the three speakers, in a phase-aligned array, sound like (Google "psychoacoustics and imaging") a single 3" speaker located a few feet further to the sides and forward of you than where those are actually mounted. It's a simulation of distance, that sounds like real distance. It was great, gave a real spacious feeling when listening.
The rest of the install was also kind of interesting...
The flagship Alpine V12 amp of the day isn't exactly "budget", but this was the ONLY amp in the install, and it was also years after that amp was released... so I didn't even pay for it. I was doing some engineering work at the time, and I either traded a prototype XBL^2 sub or a prototype big-ass amp to a CAF buddy for it (it was used, but in perfect shape), which I count as "free".
So I decided to do an amp rack in the headliner - also a budget build, you can see it's just MDF, and apparently I couldn't even be bothered to break out the router to even give the walls a round-over. Black textured finish and I was done with it. But whatever - it's on the roof and that's not something you see every day.
Again, this was a winter beater, so cosmetics were definitely only "good enough" here:
Around the amp rack is the passive crossover...
Six wideband drivers
(eventually I also added two tweeters, to the factory A-pillar location)
Four midbass drivers.
Two subwoofers.
One amp - two channels.
I ordered all the passive crossover components from either Madisound or Parts Express. Even splurging on the high-end caps and coils for the front-stage channels, I only spent a few hundred bucks for all those components, after doing a lot of listening and comparing charts and carefully picking Xover points.
It looks like a lot, but it's all just 12dB/octave slopes.
There was also a bit of trickery with the impedences... so to some degree I got lucky, because this stuff is almost impossible to align using specs (and I ended up needing L-pads, but only on the tweeters!)...
The subs were wired in parallel and the amp bridged, so they got significantly more power than the rest of the system - double, if I recall. I think the midbass were running at 4 ohms (8 ohms each, parallel), and I think the widebands were running at 6 ohms load on the amp at that frequency range. It worked out, it was pretty balanced - you can see I didn't need to do TOO much equalizing:
and that ugliness is because there used to be a spare tire mounting bracket here that used to eat up most of the hatch, so I ditched it... and again - not a show car. Good enough.
I loved that this Crossfire dual 20 band EQ had a plexi cover so stuff flying around in the hatch didn't blow away my EQ settings.
The subs were some surprise shining stars... I had a single 10 in here when I started, then a buddy of mine who owned Pro Tech (who I did NOT do engineering work for, but had some good stuff) got these eights in that I think the Credence engineer was raving about.. I think that's who made these... anyway, he was my roommate at the time, we built a box for them to try out in my Pathfinder since he had a Ranger at the time, and I told him I wasn't giving them back.
I forgot what I ended up trading him for them, but again, free-ish. And these really were superstar little eights - that box sounded like a great vented 12.
OK - anyone make it this far actually reading?
Probably the longest post in this whole Build Logs section, with the least pictures.
I hope someone gets something from it!