Paul350Z

iTrader: (1)

I took a few measurements of some sound levels in and out of the Z to see what loudness levels we are dealing with our on our audio systems. I would have guessed quite wrong - by about a factor of 100 times (20 dB)!



With the car off and standing around on my driveway I measured 56 dB. Mostly the rustling of the leaves and a very gentle breeze.

Inside the car with the windows shut the measurement was below the limits of my meter which was 50 dB.

Starting the car and letting it idle with the windows rolled up and the AC off I measured a whopping 80 dB at 1200 RPM. That's just huge. I knew the Z wasn't a big old padded Buick sedan but dang. I have over 60 sq.ft. worth of fatmat between me and the outside world to help too. Turning the AC on added another 2 dB worth of noise as the fan came on about half speed.

At wide open throttle I measured 86 dB.

Putting on my hearing protection I measured 122 dB from the stereo.

Outside the car at 3 feet from the right front tire I measured 70 dB - which is actually 10 dB more quite than inside the car at the same engine RPM! I double checked this measurement and found that only the rear of the car was as loud as the interior.

Looking at a spectrum analyzer (TrueRTA) I found that at 1200 RPM the biggest peaks in the engine's spectrum were at 138 Hz and at 36 Hz.

This is mainly an exercise in signal to noise ratio. If you're stuck between a CD player with -96 dB or one with -104 dB worth of signal to noise ratio understand that you're literally going to have to raise the volume of your amplifiers to bone crushing volume to hear the difference between the two.

PS: Dang it's humid out.



Work in progress.

plumpzz

iTrader: (10)

what does that mean, the Z is loud already so any difference doesnt matteR?

JimRHIT

iTrader: (6)

Essentially Paul is confirming my (and many other's) suggestion that spending that extra $1000 to $1000000 on the stereo upgrade is useless.

A standard components, small amp and a nice sub is all you need.

Focus on the installation and the tuning ... get the imaging and stage right ... don't worry about your equipment so much.

Cliffs: Expensive speakers in a car are a waste - spend your time/money on a good installation.

plumpzz

iTrader: (10)

Well, i couldve told you that

I just blast it, i dont listen for how 'good' it sounds. if it pumps the bass, doesnt distort, and its loud, im fine with it.

JimRHIT

iTrader: (6)

Tell that to the guys here that spend upwards of $5k on a stereo so that it sounds like a concert in thier cars .... Paul is proving to them that the difference in these is lost as soon as you start your engine.

Paul350Z

iTrader: (1)

Hey I only spent $3000 on mine.

Lots of people spend their money on their car as a hobby and hopefully listen to those $5000 systems with the car off to better enjoy them. It keeps me out of the bars at night (and rather broke).

The acoustics of the interior are just a mess of hard surfaces causing reflections, soft panels absorbing them, and seats that are too close to the rear speakers and too high above the door speakers.

I'm tempted to get a 1/3 band octave equalizer to see just how hard I'd have to equalize a set of speakers to get them to sound correct. There's a big difference between factory flat and the parametric equalizers when I'm done with a white noise adjustment ... and the music does sound better.

JimRHIT

iTrader: (6)

Hell ... my subwoofer amp is $4600 That said, I didn't pay for it so I am okay with that.

Sounding correct is all relative ... just depends on what you like ... I admire your hobby and your interest here, since you have taken a nice scientific approach to your system and tweaks ... its cool for me to see some other audio geeks out there I think you can get a noticeable improvement with some equalization ... but you are approaching the line of diminishing returns. I'd focus on imaging, time delay and and resonances you have at this point, as I'm sure your speakers sound pretty good

05-Z

iTrader: (4)

Go measure an LS430 interior at idle and post the results!

Great post.

highside107

iTrader: (1)

Daaaang what kind of amp is that? How much did you spend on it (if you don't mind me asking)?

Also, is there a noticeable difference with time delay vs. no time delay?

I spent about $3000-$4000 on my system.

JimRHIT

iTrader: (6)

JBL A3000Gti Specs

Price ... eh .. don't ask

JimRHIT

iTrader: (6)

Time delay can have a very nice effect on a system with less than optimal speaker placement.

$1000, 2000 even $5000 is okay to spend on the system ... I am just saying that the extra money spent on a (for example) Zapco amp vs. an older high quality PG or some other amp is (effectively) gone as soon as you turn your engine on in these cars.

Paul350Z

iTrader: (1)

My first car amplifier was a Zapco LC150 (LA150?) that I bought back in 1977. The thing was wicked expensive back then on my wages as a car stereo installer and even with my discount the thing was like $1200. We were one of their first dealers in the Chicago area and I think the LC150 might have been the first amp we sold. I had the thing in a box for twenty years and when I bought my Z I went looking for the thing ... can't find it. Some where between San Diego, San Francisco, Los Angeles, Seattle, and the West Coast of Australia I lost the thing.

highside107

iTrader: (1)

Wow What kind of subs do you have that could make full use of this amp?

I would assume the Z has less than optimal speaker replacement? lol So getting a H/U with time correction would be a good "investment" in the Z?

JimRHIT

iTrader: (6)

A trio of these guys



Almost any car has less than optimal placement of speakers .. cars are by no means any place to do any critical listening. You can however greatly improve your acoustics with proper placement and/or time delay.

ken350z

iTrader: (2)

I took sound readings while on the highway and got 82-83db averaged over 10 seconds. (60mph, AC off, windows up, no passenger, sensor held by my right ear facing forward)

Ken

JimRHIT

iTrader: (6)

I'd credit that mostly to the Nittos ... great driving tires .. just not too quiet. The Crawford and Borla shouldn't be adding to much to the mix at that speed.

bjr

Paul - I am not surprised by what you found at all. The car is noisy to say the least. Did you take if for a ride? Just using an SPL meter on C weighting you can get WOT peaks of road/engine noise at 110dB plus
https://my350z.com/forum/audio-and-video/149028-finally-done-thanks-for-everyone-s-help.html

Old post of mine when I still didn't know what I was doing working on tuning my little system. Several replies down I chime in with some SPL meter info. Shows about what you are measuring on idle, etc. Very interesting to see what frequency the engine noises are at.

This is my first decent system in a car. And what a bad choice to do it in. The interior space really lends itself to easy installs and if you get the tweeters installed right the sounds can be quite pleasing. But it is noisy. By comparison my wife and I had to go somewhere in her Scion xA this morning on some of the same roads I travel on every day. Her car is about as cheap to produce as you can imagine - I've noticed that they didn't finish the wheel wells at all, everything is thin and cost effective. Somehow the Z makes hers sound like a Lexus - except when she finally gets up to about 70mph and the engine drone at 3000rpm is a bit resonant. But still, it's wind/tire/road noise is not very noticeable. It was quite a drastic change as we drive my car 99% of the time and now I can't wait to finish my sound deadening. I did all the less than $300 budget crap systems in high school and college - and never did any driving above 40mph day to day either as a youngster to go to school or work. Anything better than stock was OK at the time and didn't have the money for nicer stuff. I did not realize at the time I went for a modest system in the Z just how incredibly destructive the car and road noise is. I figured I would just turn it up over the noise and it would still sound OK - nothing like sitting in the garage but should sound OK. It's easy at first to fool yourself into it being ok but living with it every day, 60 miles a day at 75mph is no treat. It is exactly why I have been educating myself in the soundproofing methods. I've got probably at least $400 into products and about 1/3 of it installed. Yes, it is the most expensive part of my system. The sub was only $300!
I guess other people can deal with it but I find the noise very annoying and tiring day to day. On it's own the noise is fine and does not bother me. I didn't expect the car to be quiet. But it is hard to really enjoy the work you put in the stereo on the highway.

bjr

I stumbled accross an article on one of those last year looking to see if Crown ever got into car audio. What a beast! What did you have to do to upgrade the electrical system/alternator? From what I remember about that amp and the Z's alternator reserve I doubt that you are stock. I'm off to see if you've posted your install somewhere. Is it in your Z??

LayinLo

And I thought that the RTA showed that my old Civic had poor acoustics......hehehe

Paul350Z

iTrader: (1)

You have a 1/24th band analyzer too? Cool.

When I make adjustments I turn mine down to 1/3 band where it's not so crazy looking trying to chase down ever single 5 Hz peak. Any car is going to have a thousand peaks caused by the resonance of various parts under acoustic energy. I did a second Z today and found peaks at 40 Hz and another at 140 Hz which have a wave length of about 30 feet and a bit less than 8 feet (SWAG) which are pretty much the length and width of the car vibrating with pink noise generator.

If I were to do the long math - temperature and barometric pressures up here at +950 above sea level I'd probably get closer to the actual size of the car. But the point is that every thing is reflecting, absorbing and vibrating energy back at a frequency covered by the pink noise signal to some degree.

In a home we set the listening position far enough away from the speakers to prevent early reflections. My subwoofer has 20,000 cubic feet to feed ... not 75.