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The SQ Car Audio Thread V2

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Welcome to Version 2 of the SQ Car Audio thread!


The last thread got buried and full of information. It's a bit daunting to sort through, so I've created a new one to make it a whole lot easier and to consolidate some of this information. Given the sheer number of questions I get regarding this, I figured I'd create a thread to answer them off the bat.

My mission here is to make competition-level sound quality feasible and affordable so you don't spend the thousands of dollars going through parts only to come back to this point. Read this thread, and you can build on my experience.


Getting Started
To start, you'll want a good idea of basic audio principles so you know what I'm talking about throughout this thread. For that purpose, I've created four basic Audio 101 "lectures" on my website, which you can find in the link below. Start from the bottom. If you have questions, post them here. Don't even bother thinking about SQ car audio until you've read these articles.

Audio 101 - The Xtreme Revolution


Expectations
I'm sure some of you came here thinking "The sound system in my Cruze sucks, what can I do to make it better? I want some great sound!" I hear that a lot, and I have an inbox full of these types of questions. Before we proceed, there are things I expect of you. If you cannot meet these expectations, you shouldn't be here.


  1. Cost. As a starting point, you should expect to spend $1000 if you want a good set of front speakers with MDF baffles, a proper install with door and trunk treatment, good wiring, and a good SQ subwoofer in a custom box. If don't have at least $1000 or don't want to spend that much, come back when you have accepted the cost of this endeavor. This applies to total installs, not to just a single subwoofer. Some of you will probably say, "but I can do it for so much cheaper than that!" Really? With a passive crossover front component set, a single 8" subwoofer, custom box, two amplifiers, sound deadening, and an AA-GM44 harness, you're right around $930, and we haven't begun to talk about wiring. If you can build the box yourself, you can save some money. Otherwise, I build subwoofer boxes and MDF speaker baffles at what most consider to be a very good price.
  2. Time. If you want a system installed within a week because you just got your tax return, your bonus, or birthday money and can't contain yourself, don't waste my time. It will take you time to choose the parts that are right for you. It will take you time to learn why they were chosen, and why you shouldn't have bought the ones on the shelf at Best Buy. Since you will most likely be installing this yourself (let's be realistic, most shops do shoddy work by my standards), you will need time for that as well. We have some members on this board who can perform high quality installs should you really not want to pull your own trim panels.
  3. Effort. You need to learn at least the basics of audio. If you don't want to put any effort in, don't expect me to help you. I know this doesn't apply to most of you out there, but I'm saying it as a fair warning to anyone who thinks they can have their hand held throughout the entire process. I'm making tools available to you so that you can learn, have true appreciation for what's going on, and put together an excellent system.
  4. Patience. This ties in the last two points, but it deserves its own point. If you order a box and baffles from me, expect to wait a while as I've never yet had a day where I didn't have a box in progress. If it takes me 2 months to get everything done, chalk that up as part of the cost of getting a competition-ready custom made subwoofer box built for cheap. If you find yourself not understanding how something works or how to do something on your car, don't get frustrated. Ask questions, and wait for an answer. Keep in mind that we all have lives outside this forum.



In my next post, we'll move straight to system recommendations.
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Looking at different amplifier options, what affect will it have on the front stage if we used a lower wattage rating amp, say 20-30 watts rms for the tweets, and a higher rated amp on the silverflutes? Would this need to be adjusted for in the DSP Tune?
I understand the tweets don't need a lot of power. What is the RMS rating on the silver flutes? All I can find listed is 80 watts but that doesn't specify RMS or MAX.
 

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Discussion Starter · #462 ·
No effect at all. I used a 25W per channel coustic power logic amp (made in 1992) for a while on my tweeters and they were fine. No adjustment needed.

RMS on the silver flutes is probably around 50W.

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I'm starting to think that the Factory headunit doesn't give out enough Volt to even consider adding an Aftermarket amp or Speakers, I've gone that route and my Sound quality at moderate to high volumes has dropped significantly. All I'm hearing is High pitched sounds from tweeter and somewhat low quality thin sounding Mids from the woofers.

The technician said its mostly my Factory Headunit, which is underpowered for such setup. Adding an amp , speakers and sub has done very little to change the SQ.

I've also created a new thread and would like someone to help me here: http://www.cruzetalk.com/forum/36-g...ity-dropped-aftermarket-amp-speakers-sub.html
 

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SCruze
I began to think the same thing about the stock head unit. I installed everything and triple checked all my wiring. Sounded like crap. Messed with the amp gains and swapping cables. Nothing improved the sound. Turning the volume up just sounded horrible. I mean really bad. What I came to find out was that I made a huge error. I thought I installed the tune file into the DSP when in actuality I didn't. I got the message from the software stating the file loaded successfully. When I got this message I assumed it was installed on the minidsp. I read through the manual a little more carefully and found my error. Consequently I damaged a Tweeter in the process. Once sorted out it sounds pretty good. Plenty of power and clarity. This may have been your issue as well???? I find the DSP stuff to be very confusing.

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I'm up to 104 hours of install time, got my DSP issues sorted out, Sub installed, gains all adjusted, interior mostly back together and I finally got to really listen to it. Well, all I can say is, Amazing. Yes, it's that good. Thank you very much MR. Xtreme. All that is left is to finish up all the sound deadening and mount the amp shelf under the rear deck. I'm stoked. I can safely drive it now that most of it is back together. Probably another 50 hours or so should do it. This has been a huge job and the end result is well worth it. :th_dblthumb2:

Rich.
 

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What a great thread even tho its quite old now but stills seems relevant to Gen 1 cars. I actually have a 2018 Holden Astra Sedan down in Melbourne Australia but its a rebadged Chevy Cruze.....its the 6 speaker setup...non-amplified so have the dash, front, and rear doors.

Is there anything setup like this for Gen 2 cars or are they close enough to each other that this will work fine for a Gen 2 car?

Shipping things to Australia is another matter but one problem at a time :)

Thanks!
 

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what all do you have and how much?
I have the dayton/seas setup with everything needed to make them work.
I have a for sale thread here:
 

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Looking for some insight and understanding of the shelf filter. Hopefully Andrea will chime in. I've had my viffa /silverflute system installed for just over a year now. One thing that's really bugging me as of late is the overpowering of most vocals and guitars at louder volumes. At louder volumes they can be very fatiguing and sometimes they just downright hurt. When I say louder volumes I'm talking levels just under half volume, such as #21 & 22. This is mostly noticeable on CD's and not so much radio stations. I do notice that all radio stations sound pretty boomy ( bass heavy) compared to CD's. I've verified the tone controls are all set to flat. Even tried reducing the mid range on the head unit and found it doesn't help. Noticed the radio and cd sources have independent tone controls and made sure all were set to flat. I sometimes wonder if the factory head unit is altering frequencies as the volume is increased. In trying to keep this from being too long winded on my part I'll keep this specifically to the shelf filter. I started re reading the SQ version 2 thread and noticed the mention of the shelf filter as a must to tone down the offensiveness of the said frequencies. I copied and pasted the info below. So looking at the tune file there is a low shelf filter applied to both tweeters. The right is set at 4500hz with a gain of -2db and a Q of 2. The left tweeter is set to 3500hz with a gain of -3.2db and a Q of 2 also.
Trying to understand all this processing stuff generates many questions.
Any help with this would be greatly appreciated.

Here is the copied and pasted info from back in 2014:
"Blue Angel said:
Is this what's responsible for the horrible screeching of the stock system? I wasn't sure if it might be a breakup mode of the door woofers, but this would make sense. Some songs that have prominent notes in just the right places are pretty much unlistenable at high volume.
Yep.

In speaker design, we call it baffle diffraction. With software, I can simulate the frequency response of a linear driver on a rectangular plane based on the driver's location on that plane. Any frequency with a wavelength larger than the dimension of that baffle will begin to drop in output. In open space, the end result will be a -6db drop in output in the lower frequencies. The only way to maintain a completely flat frequency response with a perfect driver is to create an infinite baffle. Any frequencies with a wavelength larger than the baffle begin to wrap around the speaker and do not get reflected toward you, but toward other parts of the room. Conversely, when a driver is mounted inside a horn, all frequencies larger than the width of the horn walls are amplified.

That being said, the situation changes a bit once you start horn loading drivers. Consider what frequencies reflect off of surfaces surrounding their pillar mounts based on the wavelength of those frequencies.

3000hz for example has a wavelength of 4.5". Since the wavelength originates from the center of the driver, 1/2 of that becomes 2.25", which is awfully close to the distance from the center of the tweeter and the dash. The windshield is even closer, where we find a 4000hz wavelength of 3.4". You will find the most offensive frequencies in this car to be 2500-4000hz, all of which can be traced back with a ruler to horn loaded corners surrounding the tweeters. Since those frequencies are amplified due to environmental anomalies, they need to be tuned down by an order of 3-5db.

If you remember listening to my car, there was nearly a complete lack of listening fatigue at loud volumes with any music. Nothing causes ear-piercing discomfort because all of these anomalies are accounted for in my tune and the tunes published in the first page.

Back on topic, do these notes happen to be certain electric guitars, harmonicas, and female voices? If so, that's precisely the range we're referring to. It certainly is of no help that the tweeter has a very basic 1st order crossover slope at 6db/octave. An additional inductor would do a world of good, but would also drastically increase the cost of the system from a production perspective. Copper isn't cheap. "
 

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I sometimes wonder if the factory head unit is altering frequencies as the volume is increased.
I'd expect it to. Do a search on "Fletcher–Munson curve".

Something you might try is turning down your amp so you have to turn up the head unit. That will make the head unit use a different curve - hopefully something more appropriate for the volume you've got.
 

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Is there an actual way to test the head unit for a frequency curve to see what it's doing at various volume levels? I have heard of bass roll off in factory head units for protection of the speakers at high volumes but have no idea if its a myth or not. I'm using an LC2i for my line out converter and have it set for no bass rolloff. Assuming my cruze does not have bass roll off. If it does it must be very subtle. Would be nice to actually know what's going on with these things. I did reduce the gain on my amp and noticed no change. All that did was require a higher volume number. This is where I feel a small change in the tune file settings might be what is actually needed for my actual Cruze. I may just have to hook up my lap top and start playing around.
 

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I'm sure you can find a MP3 file of "white noise" all frequencies at the same level. However, you'd need something to view the results.
 

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How about a pink noise generator from a home stereo system?
I do have a couple test tone cd's with pink and white noise tracks. Haven't got around to purchasing a measurement mic yet, but it is on my bucket list. Learning how to use it along with the software is another thing. I did play around with the gains on the tweeter channels some more and am getting better results, but it does require a higher volume number. Still some vocals and guitars can be fatiguing. How would pink noise reveal if there is a frequency curve and if the head unit is altering frequencies with a volume increase? I get that the tune file was probably created at a certain volume level that it sounds best at but what is that volume level? Andrei is probably the only one that can answer that one. I would like to believe that the head unit provides a flat curve throughout the entire volume range but I doubt it does and just don't understand how to test for it.
 

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How would pink noise reveal if there is a frequency curve and if the head unit is altering frequencies with a volume increase?
As I recall, pink noise is white noise with some filtering applied. With white noise, I believe you have constant amplitude over the frequency range of interest, usually 20-20,000 Hz for high fidelity audio.

You would connect a spectrum analyzer to the speaker output with all tone controls (ie, graphic eq) set flat. The spectrum analyzer will run an FFT on the white noise, and the output would, ideally, be something like what's in the pic. (Technically, the FFT output will be discrete frequencies, rather than continuous, as shown, but I'm not gonna re-draw it now. )

Line Diagram Rectangle


I'm not sure how the change to pink will affect it.

The limitation you will have with the signal source on a CD is that you cannot control the input level - it's fixed on the CD.

A more typical test would be to supply a signal to the radio, using the aux-in for example. In my limited audio experience, we used a Rohde-Schwarz audio analyzer called a UPV.

For measuring gain over frequency, it will supply the stimulus signal, and sweep it over the frequency range of interest. For each frequency step, it will measure the output power lever and calculate and plot the gain. Gain A = Pout/Pin (= Vout^2/Vin^2) . For that, you will need a test load, such as a 100+ watt 4 ohm resistor. (2 or more if testing multiple channels.)

To see what it's doing with increasing output level, I envision running multiple sweeps at progressively higher volume settings. You will get multiple curves, and stack them on top of each other.

I hacked a quick and dirty look at what you might see for first (black) and later/last (red) measurements, if it is indeed adaptively attenuating the lower frequencies.

Line Furniture Slope Diagram Parallel


There are other things the system can be doing to control the output power, such as compression. And, given the cheap signal processing silicon available today, maybe they've developed some more exotic adaptive filtering that requires other testing methods.

I'm not current on what's available for the desktop, but I'd wager you can get a PC add-in setup with signal generator, ADC, and software for way less than the $20k for the Rohde-Schwarz.

It should allow control of the input amplitude and frequency, measure the output voltage, calculate the power, and generate some plots and data tables (.csv's) - all the stuff needed here.

BTW, forgive the pics - they were hacked in Paint, which is a far cry from MatLab :)

[Edit]Thinking about this some more, if you have a pink noise source, and some way to do spectrum analysis on the output, you could run multiple sweeps of that, at progressively higher volume settings. You won't necessarily know the exact gain values, but you should still be able to see how the spectrum changes with increasing volume settings. That would still be useful info, I would think.

Doug

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Thanks for your input Doug. Unfortunately I have no idea about most of what you just said. FFT? Fast Fourier Transfer? What the heck is that? As far as the CD as the signal source I disagree with you. If your source signal is from the CD, that's what we want to measure as we turn up the volume. I would not bother using the usb port or auxiliary jack as those are crap sources. Auxillary jack is highly attenuated as I found out when trying to use it for other source material. USB I never tested. I just assume it's crap as is everything else with computers. I thought using a microphone to capture the sound would be the way to go as that is how it was measured for tuning. Is it possible to connect the output (speaker terminals) of the amplifier to an RTA to get measurements? Although that may be too much power for the laptop and REW to handle so would require specialized equipment. Or possibly connect and take measurements prior to the amplifier input? I have know idea. This is way over my head. I'd just like to figure it out.
 
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