revvenue

I recently had the opportunity to hear an install done by someone who obviously didn't know anything about Frequencies/EQ/etc. (I know little myself but geeze) he had some high end audio stuff in his car but sounded like garbage because of the tune... Not even sure how that kind of stuff was getting through his crossovers on his components... it got me wondering if I could get even BETTER sound out of my system... and how many other DIY newbies out there have a problem with this.

I wanted to start a discussion about proper tuning for your aftermarket speakers. My apologies if this has been gone over in the past here, I've looked through the threads and can't seem to find much on it. I know this is a problem a lot of people have with setting up their new system to get the best sounding full range possible (dollar's worth!)

Anyway... Other than "going by ear", or simply reading the documents that came with your equipment, could you list:

Equipment installed in your ride (amp power/monitors)
Freq/Hz you have each component tuned:

1. Fronts woofer/mid/tweeter
2. rears [coaxial or components if you happen to have them]
3. your sub with the size/wattage if sealed/ported)

If I'm out of line here so be it, but I think it would help out a lot of people new in to car audio (like myself) get better sound out of their equipment!

Paul350Z

iTrader: (1)

I have been working in acoustics for about 30 years. Back when I began it took $20,000 worth of calibrated test equipment to set up a studio ... not now, it takes a laptop, a CD player, a calibrated microphone and $100 worth of software (or less).



I set my Z up about five years ago using such a system and the results are very enjoyable. I really spend the time in my home theater to get things done right and just took my gear out to the car to see what it was like. Ideally I would use a graphic equalizer to tune the cabin for best response and then use the tone controls on the head end to tweak for personal taste.

The tests are pretty simple. A microphone with a calibration is connected to a laptop. The calibration compensates for any flavoring the lab mic might add to the the measurement. The computer program creates a hissing noise (pink noise) that has equal energy in every octave. If the system under test has perfect response the display shows a perfectly flat output. In practice that's impossible to get.



I've taken my home theater speakers outside to avoid room influences and measured them in "free air" and they're pretty good. Drop those same speakers into a room, even a huge one like my theater, and they start to react with the walls, ceiling, and even the furniture and people. At work I tweak the high-end up a bit to compensate for the people in my 156 seat auditorium. Equalizers can be used to counter the effects of the room but in a building you can also move the speakers around or even add treatments to the room (live end-dead end) and traps.

Not so in a vehicle.

Inside the cabin of a car you are highly restricted. The speakers pretty much go where they go. You can add (and I recommend you do) sound treatment to dampen the panels which will start to resonate (buzz) with the correct sound energy.



I ran a test disk with pink noise to test the entire system out from the DVD/CD response. through my amplifiers, to the crossovers, and speakers.



I mounted the microphone at ear level in the driver's seat and put my laptop where I could read the measurements.



When I started tuning my car I noticed there were three bad peaks and one dip in my system. The three peaks turned out to be the acoustical harmonic equal to the length, width, and height of the cabin. I don't remember the exact frequencies but they were like 180 Hz (width), 250 Hz (height), and 80 Hz (length). These are all very audible frequencies and the peaks were substantial 6-9 dB gains. The dip I had was the subwoofer to front speakers where the response of the woofer was dropping faster than I wanted. I moved the base response of the front speakers down a bit to fill in that hole.

Climbing inside I spent about 30 minutes adjusting the amplifier's and headend subwoofer crossover and tweaking the parametric equalizer of the headend to control those three peaks as much as possible. The results are no where as pleasing as using a 1/3 band EQ nor what I would expect out of my home system but they're better than most, not as good as some.

When I was done I swept the cabin with base notes starting at 20 Hz and ending up at 70 Hz looking for buzzing and rattling. Nothing sounds more like carp to me than some idiot's license plate rattling with the bass notes! I also measured the sound level of the engine running and found that the engine is quieter along side the car than inside! The only place where the exhaust note is louder is directly behind the vehicle. Nissan does this on purpose, it is a sports car. FYI the sound level of the motor at idle was about 80 dB meaning all the efforts to make your car's sound system sound so very wonderful compete with this level of noise. At home a level of 20 dB is acceptable - 1,000,000 times less noise.



Years later when VW came out with the "talking bug" with the German accent doing interviews I thought of this photo I took while measuring the engine noise.

So many people buy very high-end sound systems and stop short of doing anything more than tweak it by (highly untrained) ear. The same goes for home television displays, if you spend $3700 for a nice 63" television spend another $40 on a calibration DVD please. Doing an acoustical analysis of a vehicle is a bit more expensive but just as rewarding.

I pulled the Bose system out of the Z so fast that I never got the chance to measure it. When I bought the Xterra it came with a Rockford-Fosgate and I enjoyed it's sound much more than the Bose so I measured it - pretty good actually. Here's the output of the stock subwoofer showing 110 dB at 40 Hz.



Here's it falling apart trying to hit a lower note of 20 Hz.



I bought the front speakers from side-by-side testing at some local stores and went backwards from that point.

revvenue

Paul, that looks like a lot of high quality information for me to digest at once. Let me read back over it this evening and I want to ask you a few questions if you've the time. We have the same front components, too!