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Use your subwoofer to get better midbass

edited April 2020 in Car Audio

I'm pretty heavy in to the car audio 'scene'; competing and going to various events.  As most of you can imagine, in car audio usually the subwoofer is in the trunk area.  Because of this, many tend to cross their door-mounted or kickpanel mounted midbass lower (usually 60hz or so) in order to keep the subwoofer from playing too high and get the bass "up front".  I made a video recently discussing this and why, though it may seem logical, it actually results in worse performance in regards to the 'bass up front' illusion and how/why you can use your subwoofer to improve midbass performance.

This isn’t truly a shocking revelation.  Plenty of people already do what I suggest.  It just goes against intuition and against some beliefs in the car audio community that a subwoofer should not play too high in frequency because it can cause the bass to be localized behind you.

The reason why is due to one MAJOR issue in car audio: the “Nearside Null”. This is the large dip in response of the driver’s side midbass speaker that occurs typically in the 70-90hz region.  This doesn't occur in every car; there are certainly exceptions to the more extreme car installs.

It is an acoustical null caused by the relationship of the listener’s location relative to the midbass location and generally caused by the width of the vehicle. If you play a track with bass guitar it’s very prevalent; you get a localization to the nearside midbass speaker when the midbass speaker is crossed lower than the frequency where the null occurs.

Generally speaking, the lower your crossover point between midbass and subwoofer, the more noticeable this occurrence is. Unfortunately, this isn’t something you can simply “EQ out”, either. Throwing +6dB at this null may only result in 1dB of actual gain; that means you’re wasting a LOT of power and risking damage to your speaker for no acoustical gain. Some of you may even think to yourselves “seems like you’re not getting much by crossing the midbass low. Maybe there’s not as much benefit as I thought in doing that”. That’s a logical assumption and a lot of times that’s actually true. Crossing the midbass too low can actually result in more “bass behind you”! And you can also take some of the strain off your midbass by crossing them at or above the null. Ironically, we in car audio tend to cross midbass low to get the “up front” bass we so much desire. BUT, IN FACT, the majority of the time you have bass that pulls to the rear is BECAUSE of the midbass nulls. I know that sounds counteractive. But it’s the truth. Standing waves are problematic and this is one symptom of them; whether in home or car audio.

Contrary to popular belief, raising the subwoofer crossover in to the region that this null occurs can actually HELP the sound to stay focused and achieve “up front” bass. If you can move your subwoofer to a location where it is null-free through a frequency above the Nearside Null then you can likely improve midbass without negatively impacting the “up front bass” effect that so many are after. And you can also take some of the strain off your midbass by crossing them at or above the null frequency. Not all have the luxury of space to move the subwoofer around much but experimentation is key here; you may be surprised at the difference subwoofer placement in the trunk can make.

And one important conclusion here is that placing the rear mounted subwoofer on the opposite side of the listening position often results in better response!



  • Great video👍
  • You also cannot fault the logic that says 150Hz is easily localizable, and that 70-90Hz is really the highest you should xover a subwoofer in a car. I never would go above 100Hz as the drivers would 'beam'. They are just not normally made to do this. Below 60 to a subwoofer in any case makes it seem as though the subwoofer doesn't have much of a job. There is less content from 30-60 than 60-90, and the 'slam' region is above 70Hz.

    When I had the last system in my old Tempo, I ran the dry-deck 12dB xover at 80Hz, the amp 12dB xover at 90Hz, and the Deck EQ at 60Hz was dropped -3 to -6dB for the midbasses to control the xmax better. Sounded great!

  • edited April 2020
    Midbass is the trickiest thing in car audio.  Without a doubt.  I've been at this quite a while and - to toot my own horn, yes - I've consistently got feedback stating "best midbass I've ever heard" from amateur competitors to literal music producers.  It takes me a while to dial it in and even then it's not perfect.  My consistent gripe with others' midbass response is this nearside null and it's always evident when someone crosses their midbass below this frequency in their car because it localizes.  However, it's a balancing act with not localizing the sub for the same reasons... but that's the nature of having a car stereo.  And that's why I made this video; to help point this out so people know what to listen for, what to avoid, and how to strike a balance with what their installs limitations are and what they are willing to accept.

    I've never had much luck crossing above 80hz in any cars I've tuned on the subwoofer but that crossover frequency has also resulted in LR2 as well as LR8 slopes in various installs so there's not a one-size-fits-all solution for the reasons you can see in my video.  And in this regard, home audio is tremendously easy compared to car audio.  I know home guys don't like hearing that but I've done it all... having a car with 10" IB woofers in the kicks panels and 15" IB subs in the back to having pro-audio subwoofers arrayed in my HT.  Every 'traditional' combo in both car and home audio.  And there's no question in my mind that car audio is immensely harder to master (and why so many just don't bother after they get it "good enough").  
  • Great video👍

    Thank you, sir!  
  • Good thinking, I've done car audio for a while, too, and have noticed just what your talking about. Figured it was something to do with a cancellation of some sort but never tried to do anything about it. Thanks for the heads up on the correction of that issue.
  • Thanks for the feedback.  There's a lot of things in car audio that are very specific to the install and vehicle.  But there's also a lot of things that are pretty universal and this "nearside null" is definitely one of those; and the bane of many car audio enthusiasts.  I have a few other ideas for videos of this nature and since the feedback on this one was (mostly) positive I'll make it a point to try to get those up some day... once I can get some speakers tested and data published.
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