House Curve: Car vs. Home

Aspiring audiophile here. Just starting up the learning curve. I recently acquired REW and UMIK and have been baselining all my gear. I have two cars with optional audio systems -- one is Harman Kardon and the other is Bang & Olufsen. My HT system is a modest Yamaha/Klipsch 5.1 bookshelf system. i had previously fiddled with the equalizers and tuned them by ear to the best of my ability. I then measured each with REW RTA to establish a baseline and found the cars to have similar responses to pink noise, but the HT looks very different.

The cars consistently show a much heavier bass response than my HT system. When I crank up the bass on my home receiver to match the cars it becomes grossly overpowering. If I try to match my cars to the HT system, they sound weak and thin.

Why is this? Could it be that road and wind noise in a car tends to subdue the low frequencies and compensation is required? Do cars and home theater systems like different house curves?

Here are the RTA curves. The red one is the home theater system. They all sound good to my wooden ears. Comments are welcomed.

JStewart said:

Does your Volvo have the Harman system with Dirac Unison? I was in one recently and it was among the best I’ve heard!

My experience with the response shapes and how they sound in car vs home is the same. More bass for the car.
When I saw JL audio used a similar target response for car “tuning” , I accepted it as the norm.

With a little smoothing applied and adjusting the x axis range, this very close to your Volvo measurement.

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The Volvo has the B&O system. I don't have a lot of experience with other systems, but it sounds pretty good to me. The curve was from a preset equalizer curve labeled "Dynamic".

In fact, it made my HT system sound bad by comparison. That's what prompted me to acquire REW/UMIK. Now, after hours of EQing, I'm happy with it.

The BMW HK system seems just a little muddier to me, especially at low volumes, but I can't point to any issues with the frequency response plot.

DanDan said:

Philip Newell is a leading Acoustician. He designed the Manor Mobile Recording Truck. He referred to vehicles as 'a limp bag' This was referring to the boundaries, which flex easily at LF, not reflecting it. So Bass sails out through the shell of a vehicle, as opposed to being contained by Concrete and similar rigid massive boundaries. Cars are a bit like outdoors regarding Bass.

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That makes sense to me regarding the need for the speakers to PRODUCE more bass because much gets lost, but the measurements shown are what was RECEIVED by the microphone. In other words, what wasn't lost.