Q&A: Eric Stevens

Car audio has a rich history filled with industry and hobbyists alike.  People who have pushed the envelope with their installs, technology, products, and intelligence.  Their contributions will always be regarded in some fashion; whether it be sharing knowledge via a forum, sharing experiences in install tricks, creating new products to help us get closer to our goals of a great car audio system, or continuing to push the competition aspect of the hobby.  With the vast amount of knowledge available I asked some of my friends who many consider “heavy hitters” in the community a few fun questions to see how their different origins and histories influence their perspective on the hobby today.

 

1) What is your name/age/education/occupation?
Eric Stevens, 53, Founder of Image Dynamics and speaker engineer starting a new brand “Stevens Audio”.


Note:  This article discusses Eric’s new company Stevens Audio:

 

2) What are your top 5 favorite songs of all time?
Can’t narrow it to just 5. I love a lot of different music.

 

3) What is your favorite thing about car audio? What keeps you in the hobby?
 Getting lost in the music and sharing it with others. I love music and audio is what keeps me in it as well as its become way more than a hobby.

 

4) What was your first stereo system? What was your first real attempt at a sound quality system?
First real system was helping put a Concord tape deck and amp with Pyle 6940 in my friend’s 79 Camaro. First real attempt at a competition SQ system was in a 86 Toyota xtracab PU using Dynaudio 17W75 with Dynaudio D28 tweeters and Crunch 10″ subwoofers in an ported Isobaric configuration using Coustic amps and Audio Control processors.

 

5) What are your favorite car audio memories? Any funny/cool stories that really make you smile when you look back?
Favorite memory was at 1996 IASCA Finals where with Image Dynamics competitors we had huge success. Many funny things happened over the years from sneaking beer with David Rivera (Fishman) into a Soundquake event, to celebrating at Spring Break with a large group and consuming copious quantities of food and tequila.

 

6) Things have changed a great deal in 15 years, … even 5 years. What do you think is around the corner for the sound quality car audio scene?
I would like to see the IASCA and other competitions grow again.

 

CA&E - July 1993 - "Installations - Company Car"

CA&E – July 1993 – “Installations – Company Car”

 

The picture above is from Car Audio & Electronics’ July 1993 article “Installations – Company Car” featuring Eric’s famed 1993 Mercury Sable build with commentary from the man himself.  You can find the article here.



Q&A: Steve Cook

Car audio has a rich history filled with industry and hobbyists alike.  People who have pushed the envelope with their installs, technology, products, and intelligence.  Their contributions will always be regarded in some fashion; whether it be sharing knowledge via a forum, sharing experiences in install tricks, creating new products to help us get closer to our goals of a great car audio system, or continuing to push the competition aspect of the hobby.  With the vast amount of knowledge available I asked some of my friends who many consider “heavy hitters” in the community a few fun questions to see how their different origins and histories influence their perspective on the hobby today.

 

1) What is your name/age/education/occupation?
Steve Cook , 40s , owner and custom installer at AudioX Inc Custom Car Audio in Florence, AL.

 

2) What are your top 5 favorite songs of all time?
“Little by little” by Robert Plant… and … wow this is hard.  I cannot possibly tell you my five favorite songs.  There’s way too many.  But I can give you five favorite artist instead:  Pink Floyd , Dire Straits/ Mark Knopfler, Keb mo, Beck, Van Halen.

 

3) What is your favorite thing about car audio? What keeps you in the hobby?
Favorite thing about car audio besides creating cool installations is just listening to music in the vehicle, creating an atmosphere, and a realistic soundstage.  That’s what keeps me going.  Searching for that perfect car audio bliss.

 

4) What was your first stereo system? What was your first real attempt at a sound quality system?
My first system was in my 79 Camaro.  I had an alpine tape deck hooked up to some flea market 6×9’s in the back deck and I sat in my car in the driveway and listened to it for hours.  I was 16 and thought it was the coolest thing ever. 

 

But how I got started in car audio is another story.  My friend in art school, his dad worked at StereoRama in St. Petersburg, Florida.  He had a Firebird with a 500 W Alpine system in it and my friend said we were going to go for a ride down the beach in his dad’s car.  So we jumped in and went for cruise down the beach.  He started playing Frank Zappa at volumes I never heard and clearness I’ve never heard before with 4 10 inch woofers in the back and Alpine mids and highs and amplifiers.  It was the most amazing thing I’ve ever heard.  A concert in the car.  Unbelievable to this day.  That is what started it all for me! I wanted that!

 

Then the SPL bug hit me and after seeing some of the world’s loudest vehicles compete with the crowds standing around them in awe, I wanted to be the world’s loudest.  After 4 years of competing in 2004 I won the Extreme Cup for the world’s loudest vehicle and then continued on breaking records until 2008 until I realized that this was very difficult and an extremely physical thing to do. Toting around a 22,000 pound van full of concrete, steel, batteries and equipment was getting very dangerous and not worth the hassle!  So I started up my SQ addiction. Then the goal to have the best sounding vehicle in the world was my only drive!  And to this day I still sit in my garage and listen to my stereo and tweak on it to gain that little bit extra sense of realism and perfection that I can only try to get out of it.

 

5) What are your favorite car audio memories? Any funny/cool stories that really make you smile when you look back?
(see above)

 

6) Things have changed a great deal in 15 years, … even 5 years. What do you think is around the corner for the sound quality car audio scene?
The biggest things that’s changed in car audio in the last 10 years is the power of the amplifiers has increased and the physical size has decreased, as well as digital processors are now available so you can fine-tune a vehicle like you could never do before.  You can almost use stock locations in the car and a DSP to get the same effect today as a rebuilt dash or some crazy install back in the day.  It’s amazing what you can do now with the technology and products we have compared to years ago.

Steve Cook hoisting the MECA Culbertson Cup won in 2009 (he has since won a couple more).

Back of Steve’s Avalanche circa 2010. It has since undergone a few versions.

 audiox

Subwoofers and Time Alignment in the Car

While working on some measurements for time delay settings in my car audio system, I remembered something I had talked to a buddy about, which was finding the crossover point between your midbass and sub, flipping one driver (set of drivers) out of phase, play a sine tone between those points and delay until you get as far attenuated as possible. Then flip back in phase and you’re done. The reason is pretty simple: I’ve never had good luck measuring the arrival time of a subwoofer or midbass that is band-passed to play low frequencies. If I increase the crossover to make them play higher – in order to get a clean impulse measurement – I still can’t get it “just right” and wind up having to dial it in by ear. So, I figure if I can do this and it works, all the better. It keeps the measurement more “real” because I’m measuring a frequency that the drivers are playing when the system is really running, rather than setting pseudo crossovers for the purpose of measurement that has yet to provide me meaningful results.

I put it to the test tonight.

Below is a plot. Without telling you what my midbass setting was already, it doesn’t really give you a specific number to go by. However, the point is to show that T/A has a maximal affect at the crossover point and there is a point where adding more hurts you. I hope you’re able to discern this from below.
I used a 65hz tone and delayed or reduced delay until the SPL was at it’s lowest. This was the point where it was most out of phase. Then all I had to do was flip the polarity back on the subs and I was the most in phase.

(click the image below to view larger)

So, as you can see, 2.00ms delay is the point at which the out-of-phase signal is most attenuated (most out of phase). Since the subs were flipped out of phase, I just flipped them back and I was done.

Here is the final result comparing the original in-phase measurement (my starting point at the beginning of all of this) vs the final result with 2.00ms delay added to the sub channels.

 

There’s about 1dB difference. Not a whole lot numbers-wise, but it actually works pretty well. Flipping between presets, where one is the original and the other is the new setting, the sound of the subwoofer is more solidly anchored up front. However, the tactile impact is also more apparent. This is a personal issue, so don’t let it become yours. 😉

I also went through the same procedure on the midbass/midrange transition and found similar results; there is a breaking point where the phase starts to turn the more you delay.

In case you’re wondering…

Why did I flip the phase (0/180) at first instead of just adding delay? No specific reason, really. Initially this was supposed to be done by ear. You can easily hear when something’s wrong. In this case, “wrong” is “not there”; aka: cancellation. It’s harder for me to hear when something is just right with the sub. The wavelength is super long and I’ve honestly just not had the best go at finding when the phase is just perfect in that transition. Drives me nuts. That’s why I started the process this way; the idea was to go until there was little-to-no sound when playing that specific tone. I just used a mic instead. 😉

 

 

Addendum: 07/25/12:

Essentially, what you’re trying to do is align phase of the subwoofer/mids at the crossover via delay (time alignment).

When talking about delay, consider the wavelength as well. That’s why you may notice that even minute changes in delay (ie: 0.02ms; one click resolution on most current DSPs) will affect what you hear.  As shown above, it doesn’t take a large amount of delay between drivers to impart in-phase/out-of-phase response at the listening position.  It seems many believe very large amounts of delay are needed for drivers/passbands of longer wavelength.  The above shows this is not the case.

In every iteration of my system in the past couple years, three 0.02ms adjustments is a way I come circle in the phase on my tweeters. One 0.02ms adjustment may be out of phase, the next is a bit more out of phase and the final (3rd) is *snap*… back in phase. I’ve talked to others who have experienced this. It’s interesting to note that ILD is often purported as what drives our hearing of higher frequencies (2khz+) and many will say that time alignment is not necessary here because our ears are sensitive to differences in frequencies only below approximately 1khz. However, time alignment will net you the ability to incrementally align phase in higher frequency(s) and result in a more coherent soundstage.