Why, then, is it that so many cars use the technique so successfully? Well, it all depends with what you call successful.
In Low Stage Part 01 - Two Speakers, I tackle some of the myths about fixing perceived stage height. In this second part I will further comment on the challenges resulting from the system's lobing patterns.
Sound judges today, seem to have forgotten that live music is large. Instead, they award higher scores to systems projecting caricature-like images. The more violins seem minuscule in size, the sharper the image these judges think it to be.
The bottom line is that when asked about how to earn critical listening skills, I tell people to just listen to real music. It is that good when compared to the garbage we are now exposed to.
On the other hand, a system using properly time corrected speakers will do both, large instrument size and solid image height. It is interesting to note that the time correction I am referring to is independent of speaker positioning. In other words, I am not against speakers on the "A" pillars. I am against using them as a way to patch fundamental problems without properly addressing such issues directly. Most system designers path their height issues and completely miss the fact that inadequate time response has killed any hope at realistic image dimensions. Soon a self fulfilling prophesy is created where judges begin to reward poor performance with higher scores because of herd behavior.
At a recent Consumer Electronics Show, I spent time with my friends Chris and Melissa Owen at their high end room. Orca had lent them speakers sporting their latest design. To be clear, the speakers looked fantastically finished. Moreover, these deployed really good drivers from Orca's arsenal. But as soon as Chris fired up the system for me, I told him that the crossover had problems that were creating comb-filtering. It seems as if the designer, like many others within the industry, used 12dB/oct parallel crossovers between drivers mounted on a surface that stood perpendicular to the floor. Anyone who pays attention to this stuff would know that this was trouble waiting to happen. But for the many who think that amplitude linearity is all that matters, the speakers were fine, just as their LEAP modeling software had predicted. So, as we move onto the car, consider that the problems I will address are also ubiquitous in home speakers. Again, it's a bit of a herd problem.
I recently showed a dear friend what happens when a tweeter on the "A" pillars is matched with midrange speakers in the kick panels. I used modeling software that is freely distributed. Oh, how I wish I had these tools when I started in the industry. Back then I had to interpret all the multidimensional variables while trying to make sense of what I was listening. I used no equipment when designing passive crossovers; just my trusted ears.
|Polar response for tweeters in "A" pillars and mids in kick panels|
|Polar response for tweeter and mid in kick panels|
And if in need of further clarification, the second set up would also project images at eye level. The main difference is that images from the latter setup would be much larger, just as God intended.
|Polar Response at 10KHz between |
tweeters in the "A" pillars and kick panels
And while we are on the subject, what do you think happens wen people use both drivers in the kick panels and then add a second set of tweeters on the "A" pillars to "lift" the sound. Often, well intended attempts use a higher frequency high pass filter for the tweeters mounted above the dash. Well, chaos is what happens. Look at the illustration to the left. It represents what happens at 10KHz with a 6dB/Oct highpass slope for a tweeter mounted on the "A" pillar and matched to a tweeter in the kick panel. It begs the question of how in the hell would one expect reliable performance; forget about good sound, just getting the same sound all the time would be a bonus.
Can anyone hear the difference? Yes. Can anyone know what's wrong with the music? No, In simple terms, the change is visceral. We just know it's wrong. These types of problems tend to fatigue us quickly.
Are the issues discussed correctable? Yes, but only when the constraints are understood. Unfortunately, many industry designers miss the science side of sound and attempt to solve everything as if it was all an art. While music is certainly an art, we should not waste valuable creative time on things better left to our tools. I hope you found this post as helpful.