# Midbass speakers in rear doors



## NOFATTYS (Jan 5, 2009)

I am in the middle of purchasing a 3 way setup and had this question. In my car (a 08 Pontiac G8GT) the stock setup is tweets in the upper dash corners under the windshield with about 2 inches of space, the 6.5in front speakers are on the midline of the door, pushed closer to the dash and slightly angled, and then there are coaxial 6.5's in the rear doors, along with two 8 in subs in the rear deck. 

Would it horrible to run the tweets and mids in the factory locations, and run the midbass speakers in the rear doors? Does this defeat the purpose of the 3 way setup? 

I am just tossing around ideas...so dont flame me too much. 

BTW my components are the Digital Designs W components with the W6.5 midbass speakers.


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## Fish Chris (Dec 14, 2008)

Hey NOFATTYS {I agree with your screen name too, btw  

I've been beating my head against the wall, over the same thing. If you have a little time, and haven't already, read through my thread, "Squeezing mid-bass in my doors"....

Hey, somebody posted this link by at least one guy (who sounds like a car audio guru.... but who knows ?) and he thinks mid-bass in the rear doors can sound great..... and then goes on to give some crazy scientific explanation for why he thinks this is....
Here, if you want to read it yourself; Rear midbass vs front midbass... - Page 7 - CARSOUND.COM Forum

In any case, what I've decided is, I'm going to build a couple temporary mid-bass enclosures with long enough speaker wires, so that I can position them all over the darn cab, to see what sounds best. I'm also going to make them pretty large, and then I can add material inside the box to effectively shrink my cubes, to try that too. Also, I plan to play with different amounts of stuffing material.....
So by the time I locate my mid-bass speakers permanently, I'll know exactly what to expect.

Just some food for thought,
Good luck on your mid-bass setup.

Peace,
Fish


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## AudioBob (May 21, 2007)

I responded to your other post on the CleanSweep. I think that you would be very happy with the tweets and mids in the stock locations up front based on where they are located. A 6.5" mid located up higher in the door will give you excellent mid-range and good mid bass punch with a well deadened door using Dynamat or Second Skin.

I would most-likely not even use the 6.5 in the rear doors. My Acura RL has speakers in the rear doors and I eventually unhooked them because they really screwed up the soundstage and imaging. It also had 6x9 openings in the back and I put a set of 6x9 woofers there to ad a little punch to the midbass/bass. 

Now the 8's in the rear deck are a different story. I have had very good luck with GM cars using the stock 6x9 or 8 inch woofers and using them for midbass/bass. Put a little power to them (75watts rms) and cross them over properly and they will add a nice punch to your low-end. Play them from about 80hz to 500hz and adjust the volume. A lot of people would want to replace the rear speakers in the deck and that is fine if you want beefier speakers back there. If you tune it just right they are not noticable until you turn them off and you realize that you are missing just a little mid to low end ut it does not pull the soundstage to the rear.


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## NOFATTYS (Jan 5, 2009)

The paper 8" woofers in the rear deck have about 50w going to them now...the G8 has a seperate amp for the subs, and turning the gain up a bit more than half way, the speakers are totally distorted at medium volume. If I turn the gain down to 50%, the bass is non existent...its quite frustrating. Since I plan on using the holes from the rear deck to vent into the cabin, I think I am going to create an enclosure for the 2 6.5" midbasses in the cubbyhole between the rear seats...its extremely large, so probably one speaker on top of the other.


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## AudioBob (May 21, 2007)

If it is a factory amp it may not be a clean 50 watts and it may be max at 10% distortion. Factory sound systems usually rate themselves like this. I'm talking about 75 clean watts rms from an aftermarket amp at .05% distortion.

Factory amps suck in my opinion.


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## PaulD (Nov 16, 2006)

many of the speakerworks cars (including RC's grand national) had midbass in the rear sieds where the back doors would be on a 4 door. Everyone seemed to love it.


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## cheesehead (Mar 20, 2007)

There is a lot of information from the past on this subject. Here is a link to get you started.

http://www.diymobileaudio.com/forum...ard-domes-rear-mounted-midbass-rear-fill.html

Here's something else for you to ponder!

This was written by Mr. Werewolf:
"A few principles of sound localization, if i may :

- In the midbass region ... say, up to maybe ~500Hz, certainly up to ~200Hz ... the dimensions of the outer ear are to small to impact the acoustic transfer function to our eardrums. So the classic "sphere with holes in the side" is a pretty accurate model of the head for midbass frequencies.

- midbass frequencies are absolutely localizable, but the ear/brain uses inter-aural time differences rather than inter-aural intensity differences to localize a midbass source. Head-shadowing, outer-ear transfer function, etc. simply will not apply for such long wavelengths.

From these basic principles we can conclude that, for midbass frequencies, there is a "circle of confusion" for source localization. The circle is in a plane perpendicular to a line drawn through the ears, this line intersecting the center of the circle. A midbass source at any point on this circle will generate the same inter-aural time difference as any other point on this circle, for our spherical-with-holes head. The geometry of this conclusion is indisputable.

How does this apply to midbass localization in a car? Well, the real situation has two sources (drivers) and two receivers (ears) of course, but it's instructive to consider a single driver and two ears. Apllying the "circle of confusion" conclusion, there's no fundamental reason why a midbass driver located "behind" you cannot localize to the front, when playing with higher frequency drivers whose locations really are front/back (and up/down) sensitive. But i think there are a few underlying principles required to really make the illusion work :

1. You still want the "circle of confusion" to be as far left (and right) as possible, to maintain stage width. This suggests that rear quarter panels are acceptable places for midbass drivers, but the rear deck is not ... because a rear deck driver will be pretty much directly behind your head, generating little or no inter-aural time difference ... and will localize much the same as a midbass driver mounted directly in front of your head ... collapsing stage width.

2. The midbass driver really needs to be generating only midbass frequencies, or the illusion is easily ruined. Driver distortion, motor noise, shallow slope crossovers, rattling/vibrating panels ... can all cuase unwanted localization. I would STRONGLY suggest playing pink noise or sinewave sweeps through the midbass driver ALONE (with the appropriate xover, of course), looking/listening for signs of frequencies that aren't supposed to be there. Solve the problems ... the success of the technique cannot be judged until this step is completed.

3. Time alignment ... both parallel and delta ... can certainly help."


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## AudioBob (May 21, 2007)

I sat in and listened to Richard Clarks Grand National many years ago on a few occasions and agree that it sounded excellent. If I recall it had 10" drivers in the rear quarter panels and 15" subs in the trunk. I also recall it having 6.5" mids in the doors and horns under the dash. My car at the time wasn't too far off from sounding as good as his but it was accomplished a little differently. I won more than my share of IASCA events with both my Thunderbird and Mustang LX back in the late 80's and early 90's.

I think that much of it is in the tuning. I have 6.5" mids in the rear doors of my SUV but they are down very low and playing upper bass and mid bass only at a reduced volume to the fronts. In a car door the mids are typically much higher so you need to do be very careful when tuning them.


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## NOFATTYS (Jan 5, 2009)

I read that article and the subsequent threads posted...I think I might just try it...see how it sounds...if its crap...im not really altering anything at this point, just installing in the factory locations so nothing will be lost. The G8 is actually setup pretty good for a custom install...since the stock 6.5" up front are mounts on the doors midline, that leaves the whole bottom of the door open for a custom enclosure to be built...it has a 3.5 in deep map pocket that expands another 1.5 for a water bottle in the bottom middle of the door. I would just have to measure it out, as the midbass speakers require a ported enclosure for max SQ and effenciency.


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## 02xblazer (Jan 10, 2009)

i asked the samething on another forum and was told it wasnt a good idea to put the midbass drivers in the back


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## sqshoestring (Jun 19, 2007)

cheesehead said:


> "
> 1. You still want the "circle of confusion" to be *as far left (and right) as possible, to maintain stage width.* This suggests that rear quarter panels are acceptable places for midbass drivers, but the rear deck is not ... because a rear deck driver will be pretty much directly behind your head, generating little or no inter-aural time difference ... and will localize much the same as a midbass driver mounted directly in front of your head ... collapsing stage width.
> "


This is my point with rears. For the driver of car (left side) if you have a front and a rear on the left side, and fade the rear so the front is slightly front yet, it will pull the stage from front to side and thus widen the stage to left/right not the front only 'front-barely-left/right'. Of course you want any left drivers to be as far left as you can, thus the door mountings for the most part. Getting it to work nice can be a pain, you don't want a peak in the rear that draws you to it on those notes, etc. It seems to add midbass simply from more drivers. I don't know about other people but things behind me are not near as easy to localize unless I am turning my head trying to figure it out, so long as I have a lead from the front (good highs and nothing obvious from the rear) it does not seem to be an issue for me. Stage is wider and midbass stronger. It also sounds better when I turn my head because the sound is not coming only from the front that would be easier to localize to one side when head is turned.

Second point is if you can put the drivers low and close to the driver, say front lower corner of the rear door, it seems to come from under you not from the rear. With a good front stage it is not noticeable. If you run them more full range this also keeps the highs muted so they don't catch you attention from the rears.


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