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Use your subwoofer to get better midbass

37K views 84 replies 39 participants last post by  oabeieo 
#1 · (Edited)
In this video I discuss why I recommend using your subwoofer to improve midbass response. Get your pitchforks ready!... I’m suggesting to run your sub higher than 30hz! :D

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!

 
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#2 ·
I've always been a big fan of this approach. When I first arrived at this site I tried going active and crossing my mids low. I noticed that it impacted my mid-range and the happy spot seemed to be steep slopes around 80hz to 90hz.

In the end, I found that a passenger rear trunk sub gave me the best performance overall. I couldn't ever make enough sense of my logic to post though. I really appreciate all the work you put in to the site.

Matter of fact, this thought process almost led me to try and replace my mids with stereo subs in my rear deck for a 3-way setup

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#3 ·
I really appreciate all the work you put in to the site.
Thanks. I'm working on getting my test setup going again. I am also going to be testing loudspeakers and doing reviews on them as well in the same format. But I plan to keep trying to do these "educational" type videos as often as I can to help people who struggled with the same stuff I did for years.
 
#4 ·
These videos are great. It took me a long time to fully comprehend some of the concepts and I'm still learning a lot. I think that's one of the reasons diyma gets a bad wrap. A lot of this information is hard to communicate.

These threads should by sticky'd! Let's keep donating to Erin too guys [emoji16]

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#6 ·
So what happens when you move the front midbass crossover point higher? e.g: going from 60Hz high pass up to something like 100Hz high pass? Would using a second order slope improve things if the filtered band is now 180* out of phase? A shallower slope starting from a higher crossover point should still leave a significant amount of energy going to the midbass at 80Hz, but still have enough effect on cone control at low frequencies.

I've been fighting this for a while in my C6 Corvette. Sub placement had a big impact on bass presence due to cancellation from the cabin geometry. I found the best answer was to move the sub(s) from the rear corner(s) of the hatch forward to right behind the driver/passenger shoulders, but I still have a relatively soft midbass response considering the power and speaker selection. Door speaker locations are not up for change, so finding other ways to minimize losses like this sounds good.
 
#7 ·
Thanks for posting this video. Since I put my subwoofer up front it has given me the ability to do, with much success, exactly what you are talking about. My car has the exact left side dip you reference. It is at 75hz and is about 6db.
Moving the sub crossover from 50hz to 80hz@12db and shifting the mid bass HP from 80hz to 110hz@12db has totaly center the bass in the car. It hits hard and center, no pulling left. Also raised the LP on the mid basses which has also improved the impact and clarity of the system.
 
#8 ·
Erin, Any input on which way the sub faces? When I place facing the back obviously I get more impact. But when faced towards front the bass seems better and easier to blend but the impact goes way way down.
 
#10 ·
To further illustrate this point about phase and doors...

275917


that is a phase measurement in smaart with 1/12 smoothing, if you see the green line and how it wraps around at 80hz you can’t possibly cross that to a sub at 80hz and get phase coherence due to the massive room mode influence at the listening position

then to show a different mounting, this is my hybrid u69v2 in the floor nestled just under the front edge of my seat IB

275918


that is what you want phase to look like, even with the small blip at 160 and 220 on opposing sides you can see that the phase (And timing also) is largely identical so I get 6db of summation and perfect phase coherence for the most part 👍🏼 It also includes the almost perfect transition to my mids from the midbass where the phase matches perfectly to over 1k where there is a slight wrinkle and then on up...
 
#11 ·
Hi, i've tried to use Smaart V8 to check phase alignment but im not able to get the measurements like yours. Mine only shows straight lines on the transfer function window. Im using behringer ecm8000 mic and um2 and connected to my helix dsp pro mk2 via rca inputs.
 
#14 · (Edited)
I took your advice. I had my door speakers crossed at 60Hz/24db and sub crossed at 90Hz/24db because I wanted more midbass, but was never happy with it. Sounded sloppy. Changed them both to 80Hz/24db and the whole thing came alive! Thanks!!
 
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#15 ·
now move the sub low pass down to 60Hz. That should clean things up even further and will also allow the accoustical crossover to stay close to 80Hz when you turn the volume up.
 
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#22 ·
Just wanted to say thanks for putting this on here. I was wondering where the midbass went in my car. Crossed it back at 80htz and sloped it at 24db. It's back and I love it.

I now have a bit of a transition problem where I can tell where the sub is kicking in more instead of it all blending. The punch is stronger now than when I used a 12db slope. Wondering if this is a trade off.
 
#23 ·
Nice video and thanks for taking the time to make it. I was always taught to crossover the sub as high as it could be crossed and then work on the mid bass crossover next. Every car and install can be so different based on so many factors that there is no one size fits all and experimenting always seemed to yield the best results for me. It's always best to let the sub do what it does best, and even at that experimenting with box configurations, placement and phasing takes time to get it just right. Sometimes I will build two or more boxes before I arrive at one that seems to work the best.

I find that letting the sub play loud within it's intended design lets me cross the mid bass speakers higher and allows them to play cleaner and louder and makes the system much more dynamic and enjoyable. I have started builds that have taken over a year to sound decent to me and even at that, I have had some that I have never been happy with. It is the rabbit hole that is high end car audio.
 
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#24 ·
Great topic - thanks for the post and video @ErinH ! I missed this thread last year as I wasn't actively working on a system.

I've been on the struggle bus getting solid mid-bass up front on the 2 Accord Coupes I've owned in the last 7 years. Before the first one in 2014 I owned a GX470 with the Mark Levinson system that had 3-way in the doors with 6x9 woofers with good impact - I never really got the bass I was looking for out of Morel 6.5s after moving to the Accord. Traded that Coupe for an Infiniti G37x that used 10s in the doors for the Bose system - again an impressive output from the front doors.

For my current Accord Coupe, using the same Morels, I started experimenting (great part of DIY) with crossover frequencies - part of this was reading online the markings from the amplifier manufacturer are often not visually correct for the built in crossover frequencies - where I thought I had previously been crossing over around 80 Hz was closer to 55 Hz.

I'm planning on downloading REW soon to use and look for the null you mention in the 50-80Hz range and adjust accordingly. After running 6x9s and 10s in the doors I was convinced I would never have the same output from 6.5s - after moving the crossover frequency (both to 80) and watching this video I have some more work to do!

-Eric
 
#25 ·
Would you ever have a situation whereby you cross your midbass say at 60hz if not lower and cross your sub higher?

If you have a set of 8’s as midbass you don’t want to really cross your midbass higher as there would be no point to a 8” midbass driver


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#27 ·
I always overlap my subs and my midbasses, and something I've found helpful is to mess with the delays of ONE driver.

For instance, when my two subs and my two midbasses are running with no delay, I have a whopper of a peak at 60Hz, something like ten dB. Obviously, this is a room mode, the four drivers are hitting a room mode.

The "normal" way of fixing this would be to use EQ, which I tried. And it wasn't satisfactory; when you're using a "cut" of ten decibels, it's just going to sound weird, that's a lot of EQ.

So here's what I did instead:

1) 60Hz is 567 centimeters long.
2) Sound travels 34 centimeters in one millisecond
3) 567 divided by 34 is 16.67

So I delayed ONE subwoofer by 4.34 milliseconds.

What this does, is it puts one of the four drivers ninety degrees out of phase with the other three. If it was a "full" 180 degrees out of phase, you would get a perfect null. By delaying it by just 90 degrees, the one of four drivers is about fifty percent out-of-phase, but not 100% out of phase.

The net effect?

The peak at 60Hz disappeared. In other words, a delay of just 90 degrees on one of four drivers was enough constructive interference to completely nullify a peak in the overall response.

I imagine you could do something similar to fill in a null. IE, if you have four drivers playing at 60Hz and you have a dip, you could make one of them 90 degrees out of phase to 'fill in' the dip.

I wouldn't do this 'delay' trick with midbasses, because they cover a wider spectrum. My subs are lowpassed at around 80hz, so the delay that I introduced doesn't have much of an impact at high frequencies. But if I had delayed my midbassed by 4.34 milliseconds, instead of my subs, then there's a possibility that the delay would introduce peaks and dips ABOVE 80hz. For instance, a delay of 90 degrees at 60Hz is a delay of 180 degrees at 120Hz, and that would introduce a null.

I know this post is kinda confusing, and as always, I recommend trial and error and a lot of measurements. My main point is that overlapping your midbasses and your subwoofer can give you some tools that are not available otherwise. For instance, if you only have two drivers playing at 60Hz (your subwoofers) then this trick I describe is not as effective.

One way to visualize the tricks that I am describing, is to learn how cardioid subwoofer arrays work:


 
#29 ·
Hi, I'm new here, but I have a decent understanding of acoustics.

I plan to run sealed subs under my front seats of my SUV because I have 10" of vertical clearance.

The idea is to slot load them with two 8" subs under either seat for a total of 4 subs.

I can build the box so that I can alter the slot to any position.

Since stumbling across this post, I wonder if I should design the boxes so that the frequency lying between the box peak and F3 point hits squarely at the midbass null. Effectively this would function as a midbass array targeting the near side null frequency.

Thoughts?
 
#31 ·
Hello from Canada, .first off a shout out to Erin for sharing the video and to those who have shared their views. Last night I was reading this thread and found it very intriguing as I have various frequency challenges with my Midbass installed in the factory location in the lower door of my gen 4 Ram truck. My issues are slightly different as my Right side driver is the typical 70 - 90Hz dip not my drivers side left. Then the Left I have a dip at 140 - 200hz and my Right side has a peak at the same frequency so in both cases they are opposite but when played together are flat. The issue as discussed in this tread is the peeks and dips are drawing the low notes to one side or the other. My doors are very well dampened with Kilmat and Noico Closed Cell PE Foam. I was crediting the lul's to so many reflections like the center console as I have tried swapping out my Morel Hybrid MW6 with a Hertz 6x9 but get similar issues measured on REW with my Audiofrog UNI-1 Mic. Note I am running a 3 way active front.
The first graph is hertz 6x9 with green as left and purple as right. The second REW measurements are the Morel MW6 with Blue as the left and green as the right.
My Midbass are running active from 70hz to 500hz powered by 210 watts of my Mosconi Zero 4.
Below are my measurements with flat EQ Crossed at 70hz 24db LR to 500Hz 12db LR as suggested by More powered by 210w of my Mosconi Zero 4.

Eye Rectangle Human body Slope Plot
Rectangle Slope Plot Font Line


As you can see from the graphs above I also have a left side peak from 200 - 400hz and a roll off of the same frequency for the right channel. To help with the 200+ frequency I have purchased new front speakers to replace my Morel's. I am expecting my Audio Frogg GB10, GB25 and GS690 to arrive this week. The main reason for my change is my Morel CDM600 mids have a FS of 480hz so I have to cross them at 500hz in my 3 way active setup where as the GB25 Mids have a FS of 170hz so I can cross these at 250 - 300 so I can move my stage up higher to the mids which are located in pods with my tweeters in my A Trim location.
White Automotive lighting Hood Light Automotive tire


With all the expertise on this thread did I make the right decision on the AF GB25 to allow a lower cut off for my mids in the A Pillar and what about bringing my Xover to 80hz between my Midbass and subs or will that not make a huge difference?
I am running 2 - 12" Morel Primo's and Hertz MLK 165.3 as rear fill at 12DB LR 300 - 4000hz.
Any advice is always appreciated.
 
#32 ·
I have had some success with this methodology.

I was running subs at 60hz, midbass at 80-400hz, and widebands from 400+ all on 24db LR filters.

I moved the sub up to 80 -still at 24db- and the midbass to 100-600 12db and the widebands 600+ 12db. After a bit of TA to blend the sub back in it is sounding great.

I decided to try it since I just got a new enclosure and two 8" VD8's.
 
#33 ·
Thank you for making this thread. I originally crossed my sub and mid bass at 60 and 80 with LR24. No matter how I EQ, I still couldn’t get the punch I was looking for. Yesterday I tried to switch the crossover point to 75 and 100. Immediately, I got so much punch that I even feel being suffocated. I’m going to RTA and fine tune the EQ to minimize the punch. I initially lowered the 85hz -3 with a Q of 4, I’m already getting much better result.
 
#34 ·
Been a fan of running like this for some time.
Midbass in the doors are crossed at 120hz and the sub plays up to 90hz. GREAT midbass and the bass is all upfront.
 
#36 ·
What happens if you don’t use a high pass on your midbass and use a low pass on your sub?

Assuming your midbass can handle no high pass would you not get better integration?

Reason I asked is that I have the Focal 8WMs and they handle anything I have given them so far and no rattles whatsoever they go very low pretty easily so what happens if I let them play as low as possible and add a sub to play upto 50hz?


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#47 ·
What happens if you don’t use a high pass on your midbass and use a low pass on your sub?

Assuming your midbass can handle no high pass would you not get better integration?

Reason I asked is that I have the Focal 8WMs and they handle anything I have given them so far and no rattles whatsoever they go very low pretty easily so what happens if I let them play as low as possible and add a sub to play upto 50hz?


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How are they mounted? In door? I just did some experimenting by building a test kick panel box for my gb60s, and the boundary loading alone gave roughly a 15db boost over the door location at 100hz starting at 175hz.
If that's the case, than it probably wouldn't be an issue if you gave them some sort of xo above resonance
 
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