Corvette C8 1LT 10 Speaker Bose System

This is a series of threads continued from here dealing with factory car audio and per @ChaChaRealSmooth's request: https://www.superbestaudiofriends.o...ai-veloster-n-car-stereo-misadventures.12756/

It's hard to get a grasp of the 10 speaker Bose system in the 1LT of the C8. (There is a premium system with 14 speakers, but I don't know how it sounds.) In some respects, the sound is good, that is fairly "clean", at least in the mids and highs. However, the bass quality sucks balls: one note bass, zero pitch differentiation, barely any articulation. The bass can get a little bit hefty and somewhat loud, but the quality just sucks at all volumes. Remember, it's Bose. The way I would put it is this: the audioin the Wrangler and 4Runner sounds not good, but it's decent; the audio in the C8 Bose 10-speaker system is that is sounds clean (outside of the bass), but it's not decent. It's like Bose is superficially good sounding from the outside, but sounds like shit internally. The Wranger and 4Runner are honest. The 10-speaker Bose in the C8 lies.

Anyway, here's the frequency response of the.

Corvette C8 1LT (Bose 10 Speaker System)
Frequency Response
Microphone straight forward where my head would be in the driver's seat


I've been saying for some time that frequency response can tell us a lot, and also not tell us very much. This is a good example. My main compliant is the lack of energy, soft runny poo transient attacks, no edge. I thought the midrange dip would be deeper or perhaps there would be uneven spots in the upper mids and lower treble. Nope. The upper mids and treble treble are in fact quite flat. I am blaming class D amplification for this. Class D can sound OK, but I think Bose just sucks at it. FWIW, the Hyundai Veloster's (Infinity) audio system, which probably also uses class A amplification, is miles ahead of the C8s. The Infinity drivers are also much better than Bose's POS paper crap.

There is maybe a peak or two (the lower peak would be audible to me) in the air region, however, there wasn't anything that went sssssss. Again, the presentation follows along the lines of overly smoothed out insipidness. I actually up the treble setting in the three-band EQ. I am curious I can get better results replacing those 2.5" Bose Twidders with some 2.5" Audiofrog speakers.

The system has an resonancy sound in the mids - like resonance inside door and dash cavities. Maybe I will Dynamat the doors, under the dash, or stuff the inside of the dash.

The shitty bass is tough to deal with. Unfortunately I cannot do anything about it with the three band EQ without also removing the lower bass. I would have preferred less mid/high bass and a bumped up low bass like the Veloster here. I felt the Veloster was a bit too aggressive in the highs, but this was easily remedied with a cap, TP, and some EQ controls:

Veloster N
Frequency Response
Mid +2, High -3, in-line cap and TP on dash tweeter

 

Complementary Bose marketing garbage:

 

After making some adjustments, I took a second measurement with the bass reduced by two notches and the highs down by one notch, and the improvement is noticeable. While this response might not be favored by most, who typically prefer a V-shaped sound, it aligns better with my preferences—a more neutral sound with a boost in bass below 100Hz. I find the technical aspects to be slightly improved now; there's less of that one-note mushy bass and more precision with less soft attacks, among other things. I suspect that the reason for this improvement is that the small door speakers were being overdriven previously. I'll explain more in the next post.

Corvette C8 1LT (Bose 10 Speaker System)
Frequency Response
Microphone straight forward where my head would be in the driver's seat
Bass -2 Treble -1


I would've preferred more bass in the 40-50Hz range, akin to what you experience in the Hyundai (which, surprisingly, lacks a subwoofer but boasts excellent quality door speakers). Overall, the 10-speaker Bose system still leaves something to be desired for me. One could argue that the primary emphasis of the C8 1LT lies not in its audio system, but rather in the captivating sound of its motor and exhaust at wide-open throttle (or startup - guaranteed to wake up the entire neighborhood).

 

I am curious myself what this Bose "Twiddler" speaker means and how it functions.

Here is the wiring diagram for the C8 1LT (10 speakers Bose Premium). I wanted to establish that the front side door and front side dash run off the same output. This is indicated by J243 and J237. The next step would be a nearfield response measure (1" away) from the front dash Twiddler and front side door speaker. The reason is to find out if there is any active EQ being used which would be likely if the outputs were separate.



@JK47: Here is your answer. The output from the Twiddler is below. A Twiddler is basically a piece of shit cheap ass paper driver being used as a tweeter. Bose can't call it a tweeter because someone could sue them for misrepresentation. However if they use a made-up term like Twiddler, then they can get away with it.

Corvette C8 1LT (Bose 10 Speaker System)
Nearfield FR Front Dash Twiddler


Now here is the response of the door side speaker (~5" diameter I believe) which is wired parallel to the Twiddler from the amp output.

Corvette C8 1LT (Bose 10 Speaker System)
Nearfield FR Front Side Door Speaker


The question begs: Assuming there is a simple capacitor in line with the Twiddler (common arrangement in car tweeters), we would not be able to get a near 30db/octave slope with such. A possible explanation would be DSP giving both the front side door and dash Twiddler a sharp boost past 5kHz. It's likely the FR of the front side door speaker would have massively fallen off after 5kHz.

(The notch at 17-18kHz is because I'm using compressed format pink noise)

It would be interesting to get to the wiring harness (or pop the trim panels) to take measurements from the amp and of the speaker drivers. To be continued.