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Discussion Starter · #1 ·
I have a 2017 WK2 Limited with the stock audio system. (6x9 front door speakers. No subwoofer). It doesn't sound bad but I noticed there's was a good amount of low bass (30-40 Hz), but overall something did not sound right. So I ran a sine wave frequency generator app and there is a pretty significant dip around 55Hz. Sounds like approximately -8 db at 55Hz.
Has anyone else noticed this?
Most cars have a natural cabin gain around 50-60Hz so maybe the engineers built this frequency dip into the head unit to flatten out the frequency response. But it did not work in my car. It just kills the bass punch and the built in EQ won't help because it controls a wide bandwidth centered around 80 Hz.
 

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You must have good ears!

When you say "a natural cabin gain around 50-60 HZ" are you referring to the cabin's resonant frequency?
Could be they incorporated a 55Hz. notch filter to prevent cabin resonant vibrations which would be beneficial if a factory sub was installed in your Jeep.
But it could be they designed one generic radio to support both sub and non sub audio systems.
With a sub installed i doubt you would of noticed that "something did not sound right".

On Page 531 of my '18 Owner's Manual there's a Loudness option.
Check to see if your Jeep has that option.
Simply put a Loudness control will increase lower and upper frequency gain as opposed to a Volume control which equalizes gain across the entire audio frequency spectrum.

From my Owner's Manual:

Loudness — If Equipped
Ye s
N o
NOTE:
This feature improves sound quality at lower volumes when enabled.
 

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I assume when you say “app” it means you are using the mic on your phone for measuring. If so your measurements are going to be somewhat inaccurate. Using a decent quality mic like a Umik-1 and REW (RoomEQ Wizard) will yield much more accurate results.
 

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Discussion Starter · #4 ·
no subwoofer in my WK2

no microphone. Just play the sine waves through the aux port and listen.

same app played on my headphones plays linear (smooth) with zero dips. in the WK2 huge dip at 55 Hz
 

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no subwoofer in my WK2

no microphone. Just play the sine waves through the aux port and listen.

same app played on my headphones plays linear (smooth) with zero dips. in the WK2 huge dip at 55 Hz
What are you using the generate the sine waves?
 

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Function Generator PRO
app on iPhone 10
Ok I see what you’re using now. Looked at my PEQ setting in my DSP and I do see a slight dip that I had to adjust for around 60hz but it wasn’t quite -8db. Closer to -2 but my Jeep isn’t a good example since I’m using an aftermarket system. Maybe others will chime in with measurements from their vehicle. There is also a standard free version of that app but not sure of it’s limitations when compared to the pro version.
 

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Its sort of suspicious that all these -db readings are around 60 Hz the nominal electric utility grid frequency.
The best way to do this kind of a frequency sweep is with a real legit function generator preferably battery operated and far far away from any electrical utility lines.

As i said earlier, the head unit might compensate for any 60Hz interference by dropping the gain in that tight frequency band or the 60Hz power lines are interfering with the apps or test equipment.
IMO its too coincidental that the gain is dropping around 60 Hz only.
 
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Its sort of suspicious that all these -db readings are around 60 Hz the nominal electric utility grid frequency.
The best way to do this kind of a frequency sweep is with a real legit function generator preferably battery operated and far far away from any electrical utility lines.

As i said earlier, the head unit might compensate for any 60Hz interference by dropping the gain in that tight frequency band or the 60Hz power lines are interfering with the apps or test equipment.
IMO its too coincidental that the gain is dropping around 60 Hz only.
My dip is because I’m using 8” Midbass drivers that I’m Xing low in custom fiberglass kicks. It wasn’t there with the factory system. I wanted to do a comparison so I took several measurements (moving the mic in ten different locations) before installing my aftermarket system. Just about any system has peaks and nulls that need filters applied. To each their own but i only run sweeps with my own test tones and measure with my minidsp mic and REW. I’m not alone..a simple visit to one of the SQ car audio forums will confirm this is the best way to measure a system.

Older post but basics are the same:

 

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Discussion Starter · #10 ·
What after
Ok I see what you’re using now. Looked at my PEQ setting in my DSP and I do see a slight dip that I had to adjust for around 60hz but it wasn’t quite -8db. Closer to -2 but my Jeep isn’t a good example since I’m using an aftermarket system. Maybe others will chime in with measurements from their vehicle. There is also a standard free version of that app but not sure of it’s limitations when compared to the pro version.
What aftermarket system are you running? Did you replace the Uconnect head unit? What DSP are you running?

I really want to take the dip into the aftermarket systems, but as you know, it's more of a deep sea dive.
 

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OK did some digging on crossover frequencies as i've never played around with crossovers.
My stock audio system with a factory sub sounds fine to me but then again my hearing isn't what it used to be.

Found this article which indicates:
Car main speakers: 50-60 Hz, the most critical element in main speaker crossovers is to block low-end bass (frequencies 80 Hz and below)
Don't know how, why or if this applies but its interesting the article does mention the words '50-60 Hz' when it comes to the main speakers.

 
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Discussion Starter · #12 ·
OK did some digging on crossover frequencies as i've never played around with crossovers.
My stock audio system with a factory sub sounds fine to me but then again my hearing isn't what it used to be.

Found this article which indicates:


Don't know how, why or if this applies but its interesting the article does mention the words '50-60 Hz' when it comes to the main speakers.

The subwoofer takes over the lower frequencies (30-80Hz) which let's the door speakers play the midbass (60-300Hz) cleaner without the low bass interfering. The stock WK2 audio system (without a subwoofer) uses oval 6x9 inch front door speakers to compensate for the lower bass frequencies lacking without the subwoofer. On the Premium Harman and Kardon WK2 audio system, the front door speakers are round 6.5 inch drivers. And the subwoofer covers the lower bass register.
 

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What after


What aftermarket system are you running? Did you replace the Uconnect head unit? What DSP are you running?

I really want to take the dip into the aftermarket systems, but as you know, it's more of a deep sea dive.
I did not replace the head unit. I didn’t want to lose integrated features. Instead used PAC integration to a Mini CDSP DL. Dirac does most of the tuning work for you so very little PEQ needed. Still have to set crossovers and TA.
 

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I tried my HK system in 2014 summit and there is a low volume that's lowest at 54 hz. By my ear I'd say it's roughly half the volume of 44 or 64.
 

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doesn't the PAC have built-in DSP?
No it’s only an integration device. Takes the bus signal Pre amp and converts to 6 low level inputs for your dsp or amp. Also offers optical out with addition purchase. I connected via toslink for clean and simple signal path.
 

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doesn't the PAC have built-in DSP?

(EDIT) I see it's a 3 band parametric EQ. Still better than factory but not a comprehensive DSP.

How do you like that PAC unit?
I like it. Really the only way to get a clean signal to work with. Several devices out there to flatten the signal but no matter the internal components, if you are not tapping in prior to the factory amp you will still be dealing with some sort of residual affect from the the factory processing.
 

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Check out the mini DL. It is much more than a dsp. It’s a room correction utility. Great for dealing with peaks and nulls along with resonances and cabin gain.
 

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Discussion Starter · #19 ·
Or they could just finally make a factory head unit that doesn't suck. It's 2021 for Christ sake.
 

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Or they could just finally make a factory head unit that doesn't suck. It's 2021 for Christ sake.
It would take a pretty impressive stock system to prohibit me from wanting to upgrade. My wish would be stop integrating so many controls and features into the HU and give an option to have no stereo from the factory..giving the consumer the option to install whatever level of system they subjectively desire.
 
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