Measuring the LT base system. - Chevy Bolt EV Forum
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post #1 of 7 (permalink) Old 07-19-2018, 05:07 PM Thread Starter
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Measuring the LT base system.

Before I even got my Bolt, I read reviews on here about how bad the stock system was. Since I compete in audio competitions, I wasn't overly concerned with it since I always replace everything anyway. But I was actually pleasantly surprised when I did some critical listening. I wasn't sure what people were complaining about, so I decided to take some measurements to confirm what I was hearing.

The first attachment is the "JBL Curve". Or Harman curve. It's a very popular "house curve" that people use as a reference when tuning their systems. They will use level, phase and EQ to get their frequency response to match that curve (or as close as they can).

The second pic is the stock, base LT system as measured by me today. It's a spatial average using 1/3 octave smoothing. The green line is the JBL curve overlaid as a reference. The red line is the measured, in-car response.

So... objectively, you can see that this frequency response is actually pretty dang good. Even for an aftermarket system, let alone a base model stock system. This is what we call "tonality" and it is the meat and potatoes of how a system sounds. Almost as importantly... the thing images better than any stock system I've ever heard. Imagine you're at a live show and sitting near the front of the stage and off to the left. The singer is in the middle of the actual stage so that's where you hear her. That's the same place you should hear her in the car- in the middle of the windshield.

Obviously there is a nasty rolloff of low end frequencies @ 50hz. Judging by how steep the rolloff is, I can only assume this is built in to the stock processing to protect the door woofers from damage. That's a problem, but easily solved.

tl;dr... the stock system is actually really good.
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post #2 of 7 (permalink) Old 07-19-2018, 05:20 PM
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Originally Posted by TaylorFade View Post
Before I even got my Bolt, I read reviews on here about how bad the stock system was.

tl;dr... the stock system is actually really good.
Can you define which stock system you mean?

Base LT Stock or Bose Upgraded (most often in Premier) Stock? I think you mean the non-Bose system.


I would be interested in a comparison of the two.

Hey Chevy! I want a few more:
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1) electric convertible (2+2 configuration)
2) an electric AWD (ala reimagined Honda Element)
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post #3 of 7 (permalink) Old 07-19-2018, 05:25 PM
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Since I compete in audio competitions, I wasn't overly concerned with it since I always replace everything anyway.
From your excellent audio measurements, what I would like to know is what exactly are your audio modifications plans for your LT?

BTW, you didn't mention what you used as a reference source for your testing (Lossy or lossless audio?), but I think the LT audio system sucks. It's not as clean and sharp, both at the high ranges (that my old ears can detect now), and certainly in the low frequencies. FWIW, the Volvo S90 Bowers & Wilkins (B&W) high performance audio system was the best I have experienced.

How can I make my LT sound just like that...on the cheap?
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post #4 of 7 (permalink) Old 07-19-2018, 05:50 PM
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I'm practically deaf at bass frequencies due to where I have worked for 25 years and genetics. I'm pleased with the bass in the stock LT system. If I can feel it, it must be pretty good.
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post #5 of 7 (permalink) Old 07-19-2018, 05:53 PM Thread Starter
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Quote:
Originally Posted by zebraitis View Post
Can you define which stock system you mean?

Base LT Stock or Bose Upgraded (most often in Premier) Stock? I think you mean the non-Bose system.


I would be interested in a comparison of the two.
I have the base LT system. Non-Bose.

I would also be interested to compare the two. Maybe if one hits a dealership lot around here, I will drag my laptop out there.

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Originally Posted by shotel View Post
From your excellent audio measurements, what I would like to know is what exactly are your audio modifications plans for your LT?

BTW, you didn't mention what you used as a reference source for your testing (Lossy or lossless audio?), but I think the LT audio system sucks. It's not as clean and sharp, both at the high ranges (that my old ears can detect now), and certainly in the low frequencies. FWIW, the Volvo S90 Bowers & Wilkins (B&W) high performance audio system was the best I have experienced.

How can I make my LT sound just like that...on the cheap?
My immediate plans are to just add a small sub and see how I fare in my current competition class. Long term... I will replace everything, add amps and DSP and utilize the triangle windows for a dedicated midrange driver.

I used a lossless, correlated pink noise file. Basically the standard for this type of measurement.

It's interesting that you say your ears can pick up high frequencies now as it's generally a given that HF hearing loss is a function of age. It *usually* gets progressively worse with age. But yes.. the low end is definitely lacking. I will admit that there isn't as much "detail" as I'd like, but the tonality and "realism" is good.

Man... that's not fair to compare our little base systems to the Volvo B&W! Lol. Or even the older ones with Dynaudio. Side note: My dedicated competition car is a Volvo s40.

Do you have the Bose or non-Bose? Because from what I gather, the Bose would be a much better platform since it uses a larger driver in the dash than the LT. The more octaves you can get coming from the dash, the better. So a 3" driver on the dash would wreck shop in the sound quality department. The majority of the world championship winning vehicles use a 3-4" midrange driver on the dash.

"On the cheap" is a relative term, but I reckon I could get the Bolt as good or better than the Volvo B&W for a couple grand. Maybe less.
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post #6 of 7 (permalink) Old 05-13-2019, 11:42 PM
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Quick question about the sweep - did you find the frequency profile to change much depending on volume? A lot of factory HUs roll off only at higher volumes, but as far as I can tell, the roll off seems to be at all volume levels. I added a 10" sealed sub (SWT-10S2) in a large enclosure (37 L), and not much is being produced below 45 Hz no matter the volume. I am going to set up AccuBass to reconstruct the lost low freq, but I can't determine the point at which to drop it in. Is the bass rolled off all across the board that you can tell?
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post #7 of 7 (permalink) Old 05-14-2019, 12:06 AM
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I am not nearly technically savvy, as you clearly know what you're talking about and compete in audio events. And I agree, the stock system is tuned. However, to my ears, it sounds like total crap. Much worse than my old Ford focus. Even when I'd crank it up, it sounded horrible. It sounded flat, lacking bass, and definitely lacking higher notes. Yes, an audio measurement can be accurate, but my ears beg the differ. I'm not being negative, but I don't really care what measurements will tell me, when my personal listening preference is not happy at all. I started with replacing my 4 door speakers, and this barely made a difference. Then I added a powered sub and it sounded great! The sub did I mean. The system as a whole was lacking. Did not satisfy me at all. I then added a powered amp/DSP unit and I'm in audio bliss. The problem I think with just the basic stock unit is the major lack of any EQ. With the DSP I can fine tune every gain, frequency, etc...I can say now that my system is perfect. But of course, probably not even worthy at all for competitions. But my ears are satisfied.

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