I figured some of you might be interested in seeing what the actual RTA curve of the stock SR+ audio system is. All measurements were done with a calibrated microphone, audio tool app (loaded up with the calibration file), immersive sound OFF, the mic at roughly where the driver's head would be, fader in the center, and a high quality pink noise played via USB. First and foremost, a dead flat RTA is not what you are after or looking for when it comes to listening to music. Humans don't hear all frequencies equally an almost nobody would like the sound of a flat frequency response.
I'll use the Harman International target curve for reference as it's been around for quite some time and many swear by it.
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And here is the SR+ with all bands of the EQ set to 0 (flat).
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As you can see this actually pretty decent in most places. It needs a sub to fill in up to about 60zh, then there is slight decrease from 60-125 (this is actually a good thing), it's relatively flat out to about 2k (also good), and then a slight drop in output out to about 16K where it then falls off. Setting the EQ to +4, +2, 0, -1, -2.5 resulted in the best curve for me. The reduce treble is the best compromise to tame that peak around 13K.
Ok, and now for my pet peeve. For the life of me I don't know why people immediately set their EQ's to a smiley face for virtually everything they own. Jump in most people's cars and chances are both bass and treble are pegged at their highest values. So here is the SR+ with a smiley face EQ setting (+8, +4, 0, +4, +8): The rise from 1k up is the equivalent to nails on a chalkboard. The only person I can imagine this sounding good to is someone who has been playing live shows for decades with zero hearing protection. For anyone else this will produce ear fatigue pretty quickly.
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So, how to this relate to the Hansshow audio upgrade. Well, after performing these measurements I don't have any real desire to add any sound from any of the additional unconnected speakers (only 4 for me as mine is a '21). The speaker high up on the A pillar is too close to either the driver or passenger's head and will pull the the soundstage back and bias it towards either listener. The lower A pillar location is actually pretty good but it's not as if the system needs any additional upper mid-range or treble. I'm sure someone will say how great the full premium system sounds with all the speakers playing, but there's a lot more going on than what any of these audio upgrade jumper cables are doing. A sub, on the other hand, is definitely in order.