Has anyone spent the time tuning their audio system with graphic and parametric EQ's. Has anyone used equipment to measure the frequency spikes and dips caused naturally by the interior of the Z? For those of you who tuned (and/or took measurements) their stereo in the Z, what type of adjustments did you make? Also, what time alignment settings did you use, if any?

I know that it all depends on what type of speakers you have, where you place them, and etc. but I would like to estimate a starting point in tuning my Z so that I dont have to start from scratch. When I tuned my old camry, I noticed a big dip in the 400-600 hz range. The time alignment settings shouldn't vary that much, assuming that we are all installing the speakers in the stock location.

Thanks in advance for whatever help you can provide.

 

There's a two-three month old thread I did here about this called "accoustical analysis" or something.



I used a calibrated lab mic, a CD with pink noise and clean 20, 25, 30, 35, and 40 Hz 0 dB level test tones, some serious hearing protection, and a labtop with TrueRTA running on it. I've also done one other member's system using the same equipment. I've found that both cars had large +10 dB resonances at 80 Hz and then again at 190 Hz. Doing the math that's a lenght of about 170 inchs and another about 6 feet. These peaks are pretty broad and I think they represent the lenght and width resonance/harmonic. There might be another around 250-280 Hz for the height but since the hood, cabin, and trunk are all at different heights where the lenght and width seems pretty constant the height harmonic might be spead out enough to not be as offensive. I had the microphone stuck in between the seat and the head rest so it was vibrating with the car. A better method would be to suspend it from a boom from outside the car sticking in through a window ... next time!



I also did a noise analysis to see how loud the Z is at idle and a wide open throttle. I found that the interior was as loud at ten feet behind the car. It was actually quieter OUTSIDE the car along side the front quarter panel than in the driver's seat. Tell me Nissan's engineer's didn't notice that. IIRC the levels at the driver's seat were 80 and 86 dB while along side they were just 70 dB and I have put about 75 sq.ft. worth of FatMat into my car.



I used the Avia home theater calibration disk to adjust my video screens and then used the subwoofer tones to tweak the audio for levels. Since my Pioneer AVIC has parametric equalizers I was able to directly address the major bumps in the bass, midrange, and treble but without a 30 band graphic equalizer I couldn't get them all. I'll looking at an AudioBahn 40 band AEX500Q or an AudioControl DQT and DDC once I get my other project completed.

 

Very informative post. Thank you. I just bought a 7 band equalizer to address some of these problems in my Z.
I'm not certain what it all means though. If you have harmonic resonances at a couple points, does that mean you have to lower the stereo output at those frequencies to counter the natural tendency of them to be louder than everything else? Did you find any frequency ranges that "disappear" when you are driving? (covered up by road noise), Should you boost them to compensate?

 

From the resonance numbers the body itself is vibrating enough to cause the microphone to shake at that audible frequency. Nearly any size room is going to have resonance and yes, you can compensate with a bit of equalization. In a listening room, studio, or theater we try to reduce the resonances with construction techniques like non-parallel walls, accoustic treatments, and even traps tune to the troublesome frequency. None of that works in a car.

With the sound at the driver's seat floating at 80 dB I don't like to have the music up much louder than that because being an old fart ... I actually have things to say to my lovely wife and we hold conversations while driving around! To pretend that listening to music in a car is anything more than just hearing it is silly to me. I have a rather nice home theater system with real speakers, amplifiers, processors with a background volume of nearly zero where goosebumps are easy to raise.

Sort of like jogging around with and iPod is just hearing music I think the same in the car. I do want to have a good experence but know that no matter how hard I try ... when I actually turn the motor on ... the listening experence goes to $h!t. I feel that there is a point of diminishing returns where you can double or triple the amount of money spent on a sound system (car or at home) which yields very little gain in return.

My very first lesson in audio was to buy things that sound good to you ... not someone else, not what was popular, not what was better looking, more cheap or expensive, or what was in the latest magazine spread. We listen to music with our ears and its these that we need to please. Too many people buy stuff to impress as if a more expensive stereo makes them a better person.

Buy good stuff and enjoy it but do it for the right reason.

Technically you use a graphic equalizer or parametric equalizer to tune the room and then use tone controls season to taste. Each producer of music has a different flavor that he's attempting. A flat room lets you hear it the way he wanted. The tweaking of that room with a second EQ tweaks the sound the way you like it. Old recordings sound completely different than new ones not only due to the technology but due to the new taste of record producers. Whether you want more cow bell or less is a personal taste and that ought to reflect your purchase of speakers to be sure as well as that second layer of adjustment to the sound.

Personally I like more cow bell.

The progressive rock from the 1970s to mid-1980s that I listen to enjoys a speaker with some forward presence. The music doesn't tend to have much content below 40 Hz. The classic rock from the late 1960s to early 1980s enjoys a bit more punch on the low end but still rarely ventures below 40 Hz.

 

If it weren't for a conversation I held with a friend the other day about a tee shirt in an online store, I would have no idea what the "cow bell" thing was about. Something to do with "Don't Fear the Reaper" (BOC). Just talkin' 'bout my generation!

I was just commenting to my lovely wife last night about how you can have a listening experience in the house and not in the car. We have Linn floorstanders with acoustic tile on the wall behind them, Linn Genki CD player, a 30 watt boutique amp, etc. 2 Channel, 'cause that's how I roll
Whether it's Beethoven or Miles Davis, it sounds real.
In the car, you're lucky to hear the music, let alone listen to it. Both of my cars have kick panel speaker encloseres, which helps a lot, but I guess it's futile to try to make a listening room out of a sports car. I can't race my house, so I shouldn't expect to use my car for a living room.
Regardless, I'm trading in my 2x10" subs for a single 8". It just might be enough. Listening to '70's and '80's music is the reason I bought the EQ and ditched the huge subs. Hopefully it will all work out and the bass player will once again have a place in my system.

 

I think the reason that I would spend a decent amount of money on my car stereo is because I am in the car for about 50 minutes of the day. The only source of entertainment (aside from driving my Z) is the stereo. I like music and I like it loud and clean, however when I am at home, I'd rather watch TV. I did not spend a whole lot on my home theater because I would only use it to watch an average of one movie a week (2 hours). I also can play whatever music I want, at whatever levels I want without disturbing anyone. But I do turn the stereo down when I have company in the car.

 

Going back to the sound analysis that you ran a while back, it seems as if you had your subwoofer up quite a bit. It seems like our the frequencies below 1khz is lacking a little bit. This probably would be due to the placement of the speakers in the door. I would expect a better response with the door pods. Do you think there would be a way to interpolate the data to make a smoother curve? there are a lot of mini-spikes that seems like it could be smoothed out a bit.
You totally lost me about the length, width, height of the harmonic resonance etc. Do you think that you can summarize that in lamence terms?

 

The length/width thing was about the size of the object determining what frequency it resonates at. (Like a xylophone- the bigger the piece of wood or metal, the deeper the frequency it vibrates at) Same thing with enclosed spaces, like drums. Being a collection of solid objects and enclosed spaces, the Z vibrates at certain frequencies. Any note played at those frequencies is going to be energized (harmonic resonance). You can set your tone controls to zero, and some notes will still be louder for these reasons. That's what an equalizer is for.

 

I think the problem is fundamental: You bought a Nissan, not a Lexus.

I highly doubt the engineers payed much attention to sound levels inside the car.

Paul - I would love for you to measure the levels I experience with the Pro-1 exhaust. You think your listening experience goes to ****?! Try headers with the pro-1 and stock sound system. Good information tho!

-Acree

 

The pictures are pre-equalization or during the process.

The software allows for a 1/24th band REALLY fine setting which is impossible to tweak. I will normally down scale to 1/3rd band EQ display just to make things easier to adjust. I like the 1/24th to look for noise sources and resonances.

The sub-woofer amplifier's gain was too high in this picture. After adjustment and in use the system sounds rather good. I've since added a remote control to the bass amp which allows me to add a bit to those songs with a weak bottom end. If you listen to the system with a bunch of bass you get use to that and turning it back to normal loudness levels makes the sound sound empty. Wait a day and listen to the proper adjusted levels and its likely to sound more normal.

The Pioneer AVIC N2 head end I have has a three band parametric equalizer which means I get one pass at the low, mids, and highs with the ability to adjust the gain and the "Q" (the curve's width). So you take aim at the worst and tweak the parametic until you get it. Ideally I'd use a graphic 1/3 octave equalizer to adjust for the cabin and save the parametric for adjusting to taste (like a tone control).

I'm busy pimping out another Nissan but I've been shopping for an equalizer to add into the Z's system. Something with some more control like the AudioBahn 40 band or the AudioControl 30 band EQ.

I know that my home system will out rock any car stereo I can wedge into the Z ... and I spend about 30 minutes driving the Z every Friday to work and on Sunday to church (when it's not raining).

But still ... boyz and their toyz.

I don't smoke, don't drink, don't gamble, don't have kids, and don't (have to) chase women any more ... so what to do with money?

 

Paul350z, do you have the door pods on your door panels? or your speaker in the stock location? I had mine in the stock location, then made my door pods. I can tell you that it is a world of differance in sound having them in a door pod. The Sound is clear and clean. No road noise coming from the back of the speakers, and no sound escaping into the door. You might want to look into it