Winter-beater 1995 Pathfinder experiment (and a long dissertation on line arrays)

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)
Attachment 11148

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:
Attachment 11149
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!
:snap:

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? :nuts:

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:
Attachment 11151

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. :lol:
Again, this was a winter beater, so cosmetics were definitely only "good enough" here:
Attachment 11152

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.
Attachment 11153
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:
Attachment 11154
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. :lol:
Attachment 11155
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!
:anyone:

So how much was this budget beater. I think it's more than the budget I have for my economical good stuff...lol I love the "it's just a beater"...with $2K of stereo in it..lol

Firstly, I dig this. It's been a long while since I've seen a thread intriguing enough to emerge from my hibernation for.

I'm pleasantly surprised to see more folks branching out and experimenting beyond the cookie-cutter brand-name flexing pillar pods and doorcard woofers. That said, I also have some concerns about your setup. It might be helpful to share with us more data on your install - T/S parameters, crossover points, frequency response and polar plots, if possible. That may help answer some questions before they need asking.

Regardless, I always appreciate an attempt at the unorthodox - especially when it is so often received with skepticism or outright rejection - and I am interested to see where this takes you.

Well, I had a decent but midgrade single-DIN Pioneer head unit that I always just kept from beater to beater. So I don't know how you price that... probably had it in 4 winter beaters, so call it 1/4 of a head unit cost?

That Alpine V12 amp was probably $500 new, but I got it used, and I traded existing stuff that I had for it - so free-ish. Half of original market price (not MSRP) is a good estimate for used prices, so call it $250 if you want.

I probably spent $200 or $250 on crossover components, because I did go full-range, so I couldn't get away from some really big coils that weren't cheap and I didn't go cheap on capacitor quality either. I could have knocked $100 off this, but why?

I think the four midbasses were under $100 total... they were probably even under $20 each but I don't remember. Parts Express usually cuts you a price break when you buy more than 4 of anything.
The six wideband drivers, again I bought a bunch of singles to listen to initially, but I think those were all also under $20 each. So probably another $100 there.
$200 for the whole front stage.

Crossfire was a midgrade brand - that dual 20 band EQ wasn't too expensive. I think I got it for $150.

What am I forgetting? Those eights - they were actual real production Pro Tech subs - there was nothing flashy about them. I'm sure MSRP on those was under$100 each, which meant cost would have been under $50 each, and that would have been the most my buddy would have charged me for them if I hadn't literally just kept them and then traded him something later for them So free, but if you want to call it $100 total then that's fair for budget purposes.
And I used to buy up these Audiopipe 1/0 gauge wiring kits that were seriously all of like $40. Huge bargain.

So what's that add up to?
HU- $0? $200? Let's go with $50 because I reused it 4 times.
Amp- $250
Xover - $250
Door speakers - $200
EQ - $150
Subs - $100

So the "if I had to replicate it" budget would be about an even $1000.

But my actual expense was
HU - $0, already had it
Amp - $0, (but $250 worth of trade)
Xover - $250
Door speakers - $200
EQ - $150
Subs - $0

Either way, that's pretty bargain, especially being one of the best sounding systems I've ever had, "real" cars included. And that includes a Focal Utopia component set that I have, that one component set alone cost me more than the whole "if I had to replicate the whole thing" budget here. I think that counts as cheap!

Yes, you maximized what you had. I see several people here buy from Parts Express, and at looking at their stuff since I'm not familiar, even if I wanted to I wouldn't know what to buy, how do you decide. I mean you bought $25ish speakers how would you know if they're any good at all. By the price I would think they sounded less than appealing.

Quote:

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Originally Posted by decibelle

Firstly, I dig this. It's been a long while since I've seen a thread intriguing enough to emerge from my hibernation for.

I'm pleasantly surprised to see more folks branching out and experimenting beyond the cookie-cutter brand-name flexing pillar pods and doorcard woofers. That said, I also have some concerns about your setup. It might be helpful to share with us more data on your install - T/S parameters, crossover points, frequency response and polar plots, if possible. That may help answer some questions before they need asking.

Regardless, I always appreciate an attempt at the unorthodox - especially when it is so often received with skepticism or outright rejection - and I am interested to see where this takes you.

---

Bear in mind this was at least 10 years ago, because I was still married back then. :lol:

I'm not sure what you are looking for T/S specs for... that might help to know?

I do wish I knew the drivers specifically myself - I'm looking for widebands for my current vehicle, and I'd use these again, but I can't find them anywhere.

What I can tell you based on memory and some evidence here were some of the Xover decisions, if that's what you are wondering-
The whole Xover was 12dB/octave.
Subs - 90hz and down
Midbass - 90hz to what I believe was 500hz based on this and this... notice the trouble spot on the EQ that's a clear sign of a crossover point:
Attachment 11158
Attachment 11159
Widebands - 500hz and all the way up....

...except they rolled off naturally at about 10khz or 12khz, so I ended up adding tweeters that I just rolled off at 6dB/octave, and I don't recall if I had that "point" at 10khz or 12khz... (I put "point" in quotes because that's such a shallow slope), and those filled in the upper octaves nicely.

The EQ image above I believe was BEFORE I added the tweeters, because I had that top band of the EQ pushed pretty high, at least relative to how far down I pushed down the whole wideband range. :wink: