# To rear fill or not to rear fill?



## Dan750iL (Jan 16, 2016)

That is my question.

Vehicle: 2004 Dodge Dakota extended cab

Three way active in the front with a sub in a truck box or two way active up front and coaxial rear fill with a sub in a truck box in the back?

Pioneer head unit (can't remember the model. Not at home right now)

TwK 88 DSP

Amp options
MB Quart MA1-440.4 x2 or
JL Audio XD600/6v2 and RF Prime R750-1D for the sub

CDT Audio drivers up front (HD6, ES02, TW26 for 3 way, HD6 and TW26 for 2 way)
Alpine SPR-50 C in the back if using fill

8" Polk Audio MM840 sub in a prefab custom box


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## High Resolution Audio (Sep 12, 2014)

Rear fill was intended for passengers in the back seat. Are you planning on carrying passengers? and do you care if they have music to listen to?


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## Dan750iL (Jan 16, 2016)

Nope and nope. That was easy.

Thanks.


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## gijoe (Mar 25, 2008)

Rear fill ( unless heavily processed) will hurt the stereo image plain and simple.


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## seafish (Aug 1, 2012)

Rear fill that is properly band passed, attenuated and delayed can in fact add ambience that does not at all detract from the front stage and that some peple very much enjoy. When done correctly, it can even widen the front stage.


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## SQLnovice (Jul 22, 2014)

I disconnected my rear fill and haven't missed it yet for the past 2 years. It boils down to personal preference. I would say experiment without it and see.


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## I800C0LLECT (Jan 26, 2009)

Loved the space it added. Also helped set my stage deep. I could steer the stage to just in front of my car. Very weird to experience

Sent from my Pixel XL using Tapatalk


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## High Resolution Audio (Sep 12, 2014)

I800C0LLECT said:


> Loved the space it added. Also helped set my stage deep. I could steer the stage to just in front of my car. Very weird to experience
> 
> Sent from my Pixel XL using Tapatalk


Do you compete? And /or are you going to Jasons GTG in North Carolina?


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## gijoe (Mar 25, 2008)

When having the rear fill debate it's very important to discuss the stereo illusion. The stereo illusion is something that (surprisingly) many people don't even understand. Part of that problem is because so much music is recorded so poorly that it's basically mono anyway, the other part is that most people listen to music passively, not actively. They put it on, but don't pay attention to anything more than the chorus, or the beat. 

Stereo is designed to create a sense of space, much like 2 eyes are required for depth perception, 2 ears, and 2 channels of audio can create an illusion of space. This is where staging and imaging come into the mix. Put on a good pair of headphones, find some well recorded music, stop what you're doing, and listen. 

The rear fill debate comes down to, how important are those stereo illusions to you? If they are important, rear speakers (unless heavily processed) will have a negative impact on that illusion. If staging and imaging are not important (in a car with all of the outside noise, and the fact that your attention should be on driving, not the music anyway, it's reasonable for even the most passionate audiophile to not care about proper stereo in a car) then rear speakers can add output and a more immersive experience.

Having a car stereo with or without rear fill is a matter of preference. If the stereo illusion is important in the car, then no rear fill or heavily processed rear fill is the way to go.


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## High Resolution Audio (Sep 12, 2014)

gijoe said:


> When having the rear fill debate it's very important to discuss the stereo illusion. The stereo illusion is something that (surprisingly) many people don't even understand. Part of that problem is because so much music is recorded so poorly that it's basically mono anyway, the other part is that most people listen to music passively, not actively. They put it on, but don't pay attention to anything more than the chorus, or the beat.
> 
> Stereo is designed to create a sense of space, much like 2 eyes are required for depth perception, 2 ears, and 2 channels of audio can create an illusion of space. This is where staging and imaging come into the mix. Put on a good pair of headphones, find some well recorded music, stop what you're doing, and listen.
> 
> ...


Excellent points. I for one, at this point in time, do not subscribe to the rear fill philosophy, because for me stereo imaging is what I'm interested in. However, some people have mentioned that if rear fill is done a certain way, ( with delay and low volume and whatever else ) it can add to the imaging in a positive way. 

I would like to hear for myself.


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## gijoe (Mar 25, 2008)

High Resolution Audio said:


> Excellent points. I for one, at this point in time, do not subscribe to the rear fill philosophy, because for me stereo imaging is what I'm interested in. However, some people have mentioned that if rear fill is done a certain way, ( with delay and low volume and whatever else ) it can add to the imaging in a positive way.
> 
> I would like to hear for myself.


I also run front stage only, in my garage it sounds brilliant, but while I'm driving I'm paying attention to traffic, checking my mirrors continuously, making sure I'm in the correct lane, etc. In my day to day driving, I rarely have the luxury of actively listening to music in the car. I can passively listen, even roll down the windows and sing, but it is very, very rare that I can divert my attention so far away from the task of driving that the stereo imagery is significantly noticeable. I would even go so far as to say that if anyone is paying that close attention to the music in their car while driving, that they are likely the ******* in the left lane holding up traffic 

If the process of driving your car isn't getting the vast majority of your attention, you shouldn't be driving.


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## SkizeR (Apr 19, 2011)

To everyone saying no to rear fill, I highly suggest looking for a car with a proper rear fill set up and getting a listen. Some of the best competition cars use it. It does in no way detract from the stereo image, and even helps push the boundaries of the sound stage even further if done right. 

To the op, you won't be able to do a proper rear fill set up with the twk processor

Sent from my SM-G920V using Tapatalk


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## Dan750iL (Jan 16, 2016)

SkizeR said:


> ...To the op, you won't be able to do a proper rear fill set up with the twk processor
> 
> Sent from my SM-G920V using Tapatalk


No worries. I was leaning in the other direction anyway but am liking the conversation about it. Lurning moar stuffs!!!

Edit: Pretty sure I saw a thread that talks about setting rear fill up recently. Took note of that one for when I set my car up. I have a DSP Pro for the car.


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## cadeet (Apr 15, 2016)

I have rears & will use them. Curious what is the typical band-pass area & how much attenuation is needed to add some fill, without distorting the image? This will be in a double cab Tundra for reference.


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## gijoe (Mar 25, 2008)

cadeet said:


> I have rears & will use them. Curious what is the typical band-pass area & how much attenuation is needed to add some fill, without distorting the image? This will be in a double cab Tundra for reference.



Really, anything above about 120hz will be localizable behind you. You'll want significant attenuation. Since you won't have L-R processing, time delay, and level matching to do it "correctly" you'll just have to see what level gives you the sound you like the best.


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## I800C0LLECT (Jan 26, 2009)

High Resolution Audio said:


> Do you compete? And /or are you going to Jasons GTG in North Carolina?


I definitely don't compete. Just been trying to figure out how to reproduce what I like whenever I want it 

I feel like I've gotten good at that but I don't have rear fill anymore. I'm front stage only and I don't think I could ever get that significantly deep stage without proper fill.

Proper fill doesn't take away from stereo at all. A competing rear stereo stage does.

Sent from my Pixel XL using Tapatalk


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## JVD240 (Sep 7, 2009)

High Resolution Audio said:


> Excellent points. I for one, at this point in time, do not subscribe to the rear fill philosophy, because for me stereo imaging is what I'm interested in. However, some people have mentioned that if rear fill is done a certain way, ( with delay and low volume and whatever else ) it can add to the imaging in a positive way.
> 
> I would like to hear for myself.


Attenuated/delayed/bandpassed L-R rear fill is intended to add a sense of space. It's to simulate a larger room than the physical (small) boundaries of a car.

I think it's important to make that distinction before dismissing it.

If you do not have the hardware to use this method, then yes, you will hurt the stereo image.


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## SkizeR (Apr 19, 2011)

did my post and the OP's reply get deleted?


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## Dan750iL (Jan 16, 2016)

I was just about to ask the same thing.

The board has been acting up a little today.


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## SkizeR (Apr 19, 2011)

well, i guess i'll do my best to remember what i said and repost it.

to anyone saying not to bother with rear fill, i highly suggest trying to find someone with a PROPER rear fill setup and taking a listen. little do many know, that some of the top scoring cars also use rear fill. it absolutely does not interfere with stereo imaging and also helps enlarge the soundstage if done right. that said, the twk isnt capable of doing proper rear fill


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## Dan750iL (Jan 16, 2016)

Following suit...

I've pretty much decided to do just the front in the truck at this point anyway.

I saw a thread recently on how to set rear fill up on a DSP. I will be going that route when I set my car up. I'm using a DSP Pro on it.


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## I800C0LLECT (Jan 26, 2009)

SkizeR said:


> well, i guess i'll do my best to remember what i said and repost it.
> 
> to anyone saying not to bother with rear fill, i highly suggest trying to find someone with a PROPER rear fill setup and taking a listen. little do many know, that some of the top scoring cars also use rear fill. it absolutely does not interfere with stereo imaging and also helps enlarge the soundstage if done right. that said, the twk isnt capable of doing proper rear fill


*LIKE*

Sent from my Pixel XL using Tapatalk


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## ErinH (Feb 14, 2007)

SkizeR said:


> it absolutely does not interfere with stereo imaging ... if done right.
> 
> that said, the twk isnt capable of doing proper rear fill


*channeling my inner Oscar here*

Actually, both of these statements are incorrect. 

Differential rear fill will interfere with the imaging depending on the track. How it's set up plays a large role in this so in some cases the negative impact can be tolerable, but they're still present. For example, if you have music with hard panned information that can often be played dead in the center behind you which hurts the soundstage. 

L + (L - R) + R + (R - L) = L + L - R + R + R - L = 2L - R + 2R - L = L + R

L+R is summed mono. 

The "if done right" part makes things tricky. So, let's say you attenuate the signal enough to where the above doesn't really bother you. Now you've attenuated it so much that when it would provide the benefits we know of, they won't actually be audible. 

I've experienced this with a lot of my music since I like a lot of music that has hard panned information. It's just one of those things you have to understand and decide if the benefit (potential enhanced soundstage size) outweighs the negatives (soundstage size can collapse). 




The twk88 can do differential rear fill. A friend of mine told me how to set it up. I did and can verify it works. 




Edit: FWIW, I'm not seeing any posts in this thread having been moderated so it must be something with the site today.


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## SkizeR (Apr 19, 2011)

ErinH said:


> *channeling my inner Oscar here*
> 
> Actually, both of these statements are incorrect.
> 
> ...


how exactly do you do it on the twk?


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## I800C0LLECT (Jan 26, 2009)

Glad you spit that out. I felt like some recordings were extreme mono when I could have sworn they weren't


Edit: it was still great for a lot of music. Just don't care about it right now 

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## ErinH (Feb 14, 2007)

SkizeR said:


> how exactly do you do it on the twk?




I'll have to ask a Kevin again or check my setup file. I can't remember off the top of my head TBH.


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## masnow (Jul 7, 2017)

Why L-R instead of R-L?

Why is it that only the noncommon signals are wanted?
Why not only the shared frequencies?
Why not full range?

If we're trying to duplicate the ambient reverb (or whatever) of an actuyal venue, why not the full range signal?

Couldn't I just place my rear speakers on axis with each other and let that remove the common signals through cancellation?

Can resistors be used to achieve the wanted delay?

what about full range but with reversed polarity to cancel out the waves which reach the rear to create an anechoic(sp?) effetc?

What about speaker placement?
Factory in the rear deck facing up
2 speakers placed centraly on the rear deck facing up, angled forward, rearward? angled to the rear?
OR on the Cpillars forward upward or rearward?

Why the limited ban width at all... 

Anyway, that will give me a bit better understanding. 

I've been reading all the post i could find for days now... I think I might be more confused now than when I started.

Thanks for any help.


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## drop1 (Jul 26, 2015)

When using rear fill you want it to sound like reflected sound. Nothing else. 
The huge delay is to make it sound like there is a large room behind you.
The L-R or vise versa is to remove any mono or center content. Using this content will pull your ears to the rear.
In the end what you are trying to achieve is the simulation of hearing reflections on a much larger room than a vehicle and all the little things we do to process the rear fill are to eliminate the rears from sounding solid, but instead washed out and being reflected to you from a distance. 
Have you ever been to a concert?
If you have you'll here the direct sound of the band coming from in front of you but you'll also hear the room the band is performing in. 
It comes in lower in volume. It's basically an echo but continuous and much faster. 
It's this sound we try to achieve with rear fill. Not to sound like the band had speakers at the back of the room which is what non processed rear fill does.

Also why band limited and not full range. Reflected sound looses high end and low end content pretty quickly. High end content especially gets duller faster over distance. The more high end content you remove the further away the back wall of the fake room we are trying to create will appear.


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## SkizeR (Apr 19, 2011)

Copy and pasted from another thread.. PS, you dont need to ask the same question in multiple threads 



masnow said:


> Why L-R instead of R-L?



same thing





masnow said:


> Why is it that only the noncommon signals are wanted?
> Why not only the shared frequencies?


to create a sense of space




masnow said:


> Why not full range?
> If we're trying to duplicate the ambient reverb (or whatever) of an actuyal venue, why not the full range signal?



higher frequencies are easier to locate. lower frequencies arent needed as far as i know







masnow said:


> Couldn't I just place my rear speakers on axis with each other and let that remove the common signals through cancellation?



thats not how sound/speakers work




masnow said:


> Can resistors be used to achieve the wanted delay?



umm.. thats also not how that works





masnow said:


> what about full range but with reversed polarity to cancel out the waves which reach the rear to create an anechoic(sp?) effetc?



That will also cause destructive cancellation with the front speakers. rear speakers with heavy delay will also cause cancellation with the front speakers, but not like this. they will just cause some comb filtering. 




masnow said:


> What about speaker placement?
> Factory in the rear deck facing up
> 2 speakers placed centraly on the rear deck facing up, angled forward, rearward? angled to the rear?
> OR on the Cpillars forward upward or rearward?



same as any speaker in a car.. ideally as deep and wide as possible





masnow said:


> Why the limited ban width at all...


you asked that above



masnow said:


> Anyway, that will give me a bit better understanding.
> 
> I've been reading all the post i could find for days now... I think I might be more confused now than when I started.
> 
> Thanks for any help.


hope that helps. someone correct me if im wrong


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## DC/Hertz (Nov 27, 2011)

So funny how just a few months ago rear speakers was the devil. 
Maybe I didn't have something right or just wasn't listening enough but I couldn't hear a difference with the MS-8 running rears with logic 7. But they where only low in the rear doors not far from my head.


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## elijahscott (Jun 23, 2017)

I800C0LLECT said:


> Loved the space it added. Also helped set my stage deep. I could steer the stage to just in front of my car. Very weird to experience
> 
> Sent from my Pixel XL using Tapatalk


Ive been doing this too I have my rear fill mid range component(no tweeter) set from 70hz to 2000hz. I time aligned them to 18ms or so both sides and it sounds like its coming from the middle to front of the car. I like how it adds some depth also. Its pretty cool how you can steer it from the doors to the center and up the left or right side or keep it in the back center like its coming from the rear deck. 
I also have them set to mono seemed to work best and they aren't super loud.

Whats a good cutoff point to set them? Ive been playing with 3500 and under.
Do you have rear tweeters? I disconnected mine.

Also, I have an Audi A4 sedan. No rear fill feels like something is missing. Even though its subtle its better in bigger cars I think. Id never do it in a coupe.


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## elijahscott (Jun 23, 2017)

drop1 said:


> When using rear fill you want it to sound like reflected sound. Nothing else.
> The huge delay is to make it sound like there is a large room behind you.
> The L-R or vise versa is to remove any mono or center content. Using this content will pull your ears to the rear.
> In the end what you are trying to achieve is the simulation of hearing reflections on a much larger room than a vehicle and all the little things we do to process the rear fill are to eliminate the rears from sounding solid, but instead washed out and being reflected to you from a distance.
> ...


Are you saying don't run the rear mids in mono?
What bandpass range would you set ?


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## SkizeR (Apr 19, 2011)

elijahscott said:


> Are you saying don't run the rear mids in mono?
> What bandpass range would you set ?


No, you want l-r, the opposite of mono. And frequency range you gotta play with. You don't need extra midbass though

Sent from my VS988 using Tapatalk


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## elijahscott (Jun 23, 2017)

SkizeR said:


> No, you want l-r, the opposite of mono. And frequency range you gotta play with. You don't need extra midbass though
> 
> Sent from my VS988 using Tapatalk


I can change it on the fly and I seem to always go back to momo. Why have it in stereo for rear? Seems like a lot of people agree with the mono point. 
You think 125hz and up would be good? 12db or 24db slope?


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## SkizeR (Apr 19, 2011)

elijahscott said:


> I can change it on the fly and I seem to always go back to momo. Why have it in stereo for rear? Seems like a lot of people agree with the mono point.
> You think 125hz and up would be good? 12db or 24db slope?


Not stereo.. Left MINUS right. No mono information at all. What processor do you have

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## naiku (May 28, 2008)

elijahscott said:


> Also, I have an Audi A4 sedan. No rear fill feels like something is missing. Even though its subtle its better in bigger cars I think. Id never do it in a coupe.


What year A4? I have a 2006 A4 Avant, working on getting rear fill set up correctly at the moment. I have mine from 300Hz up to 3000Hz at the moment. 

It's definitely tricky getting them right, at first I did not even notice they were on at all, muting them made no difference to the sound. I increased the gain at the DSP and now I can hear them, but they do not pull anything rearwards. I may dial them back down a little though, but going to leave it for a while to see how I like it.


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## elijahscott (Jun 23, 2017)

SkizeR said:


> Not stereo.. Left MINUS right. No mono information at all. What processor do you have
> 
> Sent from my VS988 using Tapatalk


audiocontrol Dm-810
I have the rear speaker level left and right going into the rear input on it.


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## elijahscott (Jun 23, 2017)

naiku said:


> What year A4? I have a 2006 A4 Avant, working on getting rear fill set up correctly at the moment. I have mine from 300Hz up to 3000Hz at the moment.
> 
> It's definitely tricky getting them right, at first I did not even notice they were on at all, muting them made no difference to the sound. I increased the gain at the DSP and now I can hear them, but they do not pull anything rearwards. I may dial them back down a little though, but going to leave it for a while to see how I like it.


its an 2010 a4. Also made a ski passthrough for it once I noticed how much better the sub sounds with the side drivers rear seat folded down. 
Similar with mine I don't notice them much. I have them a tad lower than the normal volume but time aligned it sounds like its coming from the center stage. 
Using a center speaker and I swapped my components to coax(component convertibles) the sound stage sounds much much better than in the pillars.


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## SkizeR (Apr 19, 2011)

Yeah the audiocontrol processor can't do left minus right. Hell, it doesn't even do left/right eq 

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## elijahscott (Jun 23, 2017)

SkizeR said:


> Yeah the audiocontrol processor can't do left minus right. Hell, it doesn't even do left/right eq
> 
> Sent from my VS988 using Tapatalk


yup not yet at least. Ill be testing some of that beta software for them in a few weeks they said they should have it available. Still having some issues right now


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## elijahscott (Jun 23, 2017)

SkizeR said:


> Yeah the audiocontrol processor can't do left minus right. Hell, it doesn't even do left/right eq
> 
> Sent from my VS988 using Tapatalk


can I not wire the rear mids together at the amp to create L-R?


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## tonynca (Dec 4, 2009)

ErinH said:


> The twk88 can do differential rear fill. A friend of mine told me how to set it up. I did and can verify it works.
> 
> 
> 
> ...


Do you mind posting this info? I'm trying to help my friend with his VXI amps to do rear fills properly. Not sure how to do the routing.


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## Phobos223 (Aug 20, 2019)

tonynca said:


> Do you mind posting this info? I'm trying to help my friend with his VXI amps to do rear fills properly. Not sure how to do the routing.


Did you ever figure this out on the VXi? I am curious as well


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## AudiS6GoFast (Sep 11, 2019)

Phobos223 said:


> Did you ever figure this out on the VXi? I am curious as well


I played with this for the first time today. Here is what I came up with in my VXI amps:

For the left rear:
Go to setup. Tie your input L&R together on the mixer and route that to left rear. Open the mixer path EQ for that left rear. Set +polarity -6dB on the left input, and -polarity -12dB on the right input. Go to Tuner. Set your crossover to bandpass 80Hz to 4kHz. Then go to delay/polarity and set total delay to -20ms. Under output I also trimmed -6dB.

For the right rear:
Go to setup. Tie your input L&R together on the mixer and route that to right rear. Open the mixer path EQ for that right rear. Set -polarity -6dB on the left input, and +polarity -12dB on the right input. Go to Tuner. Set your crossover to bandpass 80Hz to 4kHz. Then go to delay/polarity and set total delay to -20ms. Under output I also trimmed -6dB.

Mine is a little more complicated as I'm running active tweeter and mid in the rear, but that is basically just doubling the above steps and setting different crossover points.


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## tonynca (Dec 4, 2009)

Phobos223 said:


> Did you ever figure this out on the VXi? I am curious as well


This is what I could remember. Test it out yourself and adjust level, crossover points and delay to your liking. Every car is diff. 



















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## Phobos223 (Aug 20, 2019)

Thanks Audi/Tony! Carlos from JL just got back to me as well and told me basically the exact same thing. Will give this a shot! Thanks again for the help as always!


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## AudiS6GoFast (Sep 11, 2019)

tonynca said:


> This is what I could remember. Test it out yourself and adjust level, crossover points and delay to your liking. Every car is diff.
> 
> 
> 
> ...


Hm. When I did the routing like yours under mixer path EQ4 with L input pos polarity / -6db and right input neg polarity / -6db I got no sound. I had to make a difference between the inputs (ie set the right input to -12dB). 

I also have my polarities the opposite of you under the idea of trying to make the L rear be L-R. Rear left I have as +L input and -R input.


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## AudiS6GoFast (Sep 11, 2019)

AudiS6GoFast said:


> Hm. When I did the routing like yours under mixer path EQ4 with L input pos polarity / -6db and right input neg polarity / -6db I got no sound. I had to make a difference between the inputs (ie set the right input to -12dB).
> 
> I also have my polarities the opposite of you under the idea of trying to make the L rear be L-R. Rear left I have as +L input and -R input.


Oh my goodness. I am glad you posted this photo cause now I realized why I had no sound: I was listening to mono pink noise at the time so both channels had identical information ;-) I will change the settings!


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## tonynca (Dec 4, 2009)

Lol easy mistake. 


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## Phobos223 (Aug 20, 2019)

Hey all, so I set up the +L -R in my truck and it sounds pretty cool but it is not very noticeable, even with level cranked up. Is it safe to assume it is because my rears are low in the rear doors (2108 GMC Sierra quad cab)? My front stage is pretty f-in loud so that also could be it 

How do you even go about EQ-ing a setup like this? Just curious... or does it even matter? Thanks!


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## gijoe (Mar 25, 2008)

Phobos223 said:


> Hey all, so I set up the +L -R in my truck and it sounds pretty cool but it is not very noticeable, even with level cranked up. Is it safe to assume it is because my rears are low in the rear doors (2108 GMC Sierra quad cab)? My front stage is pretty f-in loud so that also could be it
> 
> How do you even go about EQ-ing a setup like this? Just curious... or does it even matter? Thanks!


It's not supposed to be noticeable, if done right.


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## Phobos223 (Aug 20, 2019)

gijoe said:


> It's not supposed to be noticeable, if done right.


Ok sweet. Guess I did it right then hehe Thanks


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## NoDestiny (Jul 28, 2019)

I'm planning on trying out some rear fill on my fresh install I'm working on for my 2000 Honda Insight. The hybrid battery has been removed and I'm doing a completely new trunk. Tiny hatchback... thinking about aiming the two rear speakers rearwards. I'd assume this is more preferred than, say, upfiring or forward firing? Or maybe put them in the rearmost of the trunk, forward firing?


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## oabeieo (Feb 22, 2015)

And it’s just my opinion that L-R methods don’t sound good 
It reminds me of the hirem effect in a matrix surround from the 60s 


It sounds dumb and boring in my humbleness 


Seems to me we need to see a rear processor that has some reverb , decay , detune , twotap echo , all user defined . 


TLDR I’m not a proponent of L-R rear fail


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## Phobos223 (Aug 20, 2019)

oabeieo said:


> And it’s just my opinion that L-R methods don’t sound good
> It reminds me of the hirem effect in a matrix surround from the 60s
> 
> 
> ...


Glad to hear all opinions! I am programming different rear fill options as presets and trying them all to see which I like best. Is there a configuration that you prefer that can be accomplished with a normal DSP? (I have a JL VXi) Thanks


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## oabeieo (Feb 22, 2015)

Phobos223 said:


> Glad to hear all opinions! I am programming different rear fill options as presets and trying them all to see which I like best. Is there a configuration that you prefer that can be accomplished with a normal DSP? (I have a JL VXi) Thanks



For rear fill I like to use delay and make the rears reinforce the fronts 
Just normal tape measure distance should do it the rears should “disappear “ and help create the center and staging 

I also put a shelving filter or a 1st order low pass starting around 150-200hz 
To get some of the mids so it’s immersive but it’s not talking so much. 


As far as L-R , it works, I just think it sounds fake and not realistic, so without the proper fill tools I just use them as normal speakers and cut the highs really


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## gijoe (Mar 25, 2008)

I'm with oabeieo, I don't like rear fill, even when done "correctly". It's personal preference, but even if it's done L-R, bandpassed, delayed, attenuated, etc. it is still artificial. I listen to a lot of music with headphones and some decent stereo speakers at home, so my standard is stereo, hearing any rear fill sounds really off to me (and it is off).

I can appreciate why people like differential rear fill, but it's not for me.


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## Phobos223 (Aug 20, 2019)

Thanks for the input guys. As this is my first mobile audio project (besides the random sub I crammed into the extended cab of a 1994 GMC sonoma back in the day!) it has been fun just trying to figure out exactly what I actually like. 

I have been plugging ideas that I get from you pros into my DSP as presets and then basically just playing 'preset roulette' by randomly selecting a preset without looking to see which setting its on to just let my ears try things out to different music, then recording my thoughts. Since I spend a lot of time on the road for work I get plenty of time to "test". Tonight I'll plug in something like Oabeieo mentioned and see where I am when I get home. Thanks again


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## jtrosky (Jul 19, 2019)

I've been trying "fronts only" since I installed a new amp and DSP and after over a month of playing with MANY different target curves and EQ, I've finally given up on "fronts only". I just do NOT like the way it sounds. To me, it sounds "thin" and just "bland" when compared to having the rear speakers playing as well. I have the rears at a lower level and band-passed. Still experimenting with different combinations, but right now, I have the rears band-passed at 75hz/7000hz, and EQ'd in a way that the frequency response goes "down hill" as the frequency increases - and I like the "fullness" it gives the sound. You don't actually hear the back speakers - meaning you don't even realize they are on - until you turn them off.  With this type of setup, the vocals still come from the windshield, but you just get a much "fuller" sound. I just can't get used to "fronts only". 

In my case, "fronts only" are 6x9's in the bottom of the doors and 3.5" coaxials in the dash, facing directly up into the windshield.

In the end, it all boils down to what *you* like and prefer.  Obviously, my setup isn't "correct" in terms of a "SQ" install, but it makes me happy this way, which is what is important.


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## oabeieo (Feb 22, 2015)

jtrosky said:


> I've been trying "fronts only" since I installed a new amp and DSP and after over a month of playing with MANY different target curves and EQ, I've finally given up on "fronts only". I just do NOT like the way it sounds. To me, it sounds "thin" and just "bland" when compared to having the rear speakers playing as well. I have the rears at a lower level and band-passed. Still experimenting with different combinations, but right now, I have the rears band-passed at 75hz/7000hz, and EQ'd in a way that the frequency response goes "down hill" as the frequency increases - and I like the "fullness" it gives the sound. You don't actually hear the back speakers - meaning you don't even realize they are on - until you turn them off.  With this type of setup, the vocals still come from the windshield, but you just get a much "fuller" sound. I just can't get used to "fronts only".
> 
> In my case, "fronts only" are 6x9's in the bottom of the doors and 3.5" coaxials in the dash, facing directly up into the windshield.
> 
> In the end, it all boils down to what *you* like and prefer.  Obviously, my setup isn't "correct" in terms of a "SQ" install, but it makes me happy this way, which is what is important.



Sounds like it’s done right. But it’s easy. Basic TA gets you there.

That’s great tho, yeah I like that same type of sound from rears also 
I don’t care for anything much past 800hz coming from behind me 
But I’ve heard systems with full range rears that’s are great


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## jtrosky (Jul 19, 2019)

oabeieo said:


> Sounds like it’s done right. But it’s easy. Basic TA gets you there.
> 
> 
> 
> ...


Yeah, what I meant by the vocals coming from the windshield is that even with the rear speakers playing 75hz/7000hz (at reduced levels), it still doesn't pull the vocals back away from the front stage - vocals still come from the front. I'm still experimenting with the 7000hz part. Originally I had it as 75hz/800hz, but just recently put it up to 7000hz (but with EQ that lowers the level more in the higher frequencies). Need to spend some "on the road" time with it and see if I want to keep it up that high or not. I've found that things tend to sound different while actually driving the car as opposed to just sitting in the car listening - so I like to listen while driving some before settling on a tune.

But I *definitely* enjoy the way things sound more when some sound is coming from the rear speakers. All speakers are TA'd by measuring tape only.


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## TedDBayer (3 mo ago)

I think it also depends on the car, I have a Toyota Solara convertible, 2 door, I sit closer to the rear speakers and with 4 speakers the stereo image is just wider, the stereo is there but instead of coming from a single point the sound comes from a wider sound field surrounding me and the sub fills in the bass, 6" doors, 6x9 rear ,so bass come from rear side and back.


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## UNBROKEN (Sep 25, 2009)

TedDBayer said:


> I think it also depends on the car, I have a Toyota Solara convertible, 2 door, I sit closer to the rear speakers and with 4 speakers the stereo image is just wider, the stereo is there but instead of coming from a single point the sound comes from a wider sound field surrounding me and the sub fills in the bass, 6" doors, 6x9 rear ,so bass come from rear side and back.


When it’s right…everything comes from the front. Bass included.


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## TedDBayer (3 mo ago)

UNBROKEN said:


> When it’s right…everything comes from the front. Bass included.


So mount the subs on the dash ??


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## MythosDreamLab (Nov 28, 2020)

I fully respect the rights of a person to choose, and if you don't like rear fill, don't want rear fill, wanna save some money on rear fill, or simply you don't want anyone sitting in the rear to have direct sound, it's all good with me, I assure you.

But, I am in the process of adding rear fill back to my current ride as I missed it.

_In the mid-70's I was VERY MUCH into music. so in my first car (a 2-door model - "name withheld") I bought the first commercially priced AM/FM Cassette deck that had RCA's out and a separate Amp (the brand was Westport). Back then most all the speakers available with Co-axials or 6x9's or nothing too hi-fidelity. So I decided to build my own home-style speaker set-up. I used an 8" Radio Shack Woofer, a 3-1/2" Phillips Midrange and a matching Phillips Tweeter, all connected using a off-the-shelf Radio Shack 3-way Crossover.

The only place to mount all of this was on both sides of the rear passenger area. I'm telling you this thing CRANKED..! It played it so loud that I did not care or recognize where that sound was coming from, cause it was all-around me. I think I told the story here, when I was parked in a friends driveway, in the middle of the day with the doors and rear deck lid open and his neighbor across the street called the cops, cause it was so loud...!_


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## oabeieo (Feb 22, 2015)

TedDBayer said:


> So mount the subs on the dash ??


That’s not what he meant


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## Jscoyne2 (Oct 29, 2014)

After building a front sub enclosure. I'll never go back to just a rear sub. Screw all the hoohaa about not being able to locate sound behind you. You absolutely can. Even with perfect t/a. 

Forthought: its been a longgggg time since i read about rear fill. So i could be wrong here but from what i remember. The entire idea of rear fill is to add ambience. What does that actually mean though? Ambience is pretty subjective in what it means on this forum. 

If you google it. You get , "background noise added to a musical recording to give the impression that it was recorded live."

How does your brain automatically know if a recording is live or not? It's by hearing the room that it was recorded in. Hearing the reverb of a room mostly. 

If you listen to a non live recording. You are only hearing the direct sound. Usually it's the singer, and instrument players all recorded separately and then spliced In together with correct timing. Everything is perfect. Or as perfect as they wanted it to be...or could afford atleast. 

If a recording is live or purposely recorded in a room with desired acoustics. You are(the mic) hearing both direct sound and reflections. 

Your brain has millions of years of evolution to know even the slightest thing off about a sound. So imagine yourself sitting in your car. You play a song that was recorded in a live environment. You can hear the crowd. You can hear the environment it was recorded in. Prob outside or in a room.

Our monkey brain expects to hear the reflections of the environment that the mic was located in. But it doesn't. And it doesn't really bother you. Brain just goes, "weird huh. Whatever. Anyway. Guess ill pull locational ques from interaural time/intensity difference. " So monkey brain just hears the sound coming from where the speakers are relatively. The front of you. The pseudo stage on our dash.

However, its my belief that when you have properly delayed/bandpassed rear fill. What your actually adding back is the reverb/reflections/echo that you'd hear in a larger room. Because said rooms reflections are undefined in their decay and reverb, your brain just quantifies what it's hearing as background noise FROM the front initial sound source. The direct sound. When the "background" noise is delayed really far out. Your brain says...that must mean the room is really large because the time difference between the direct sound and reflections was so vast. 

Tldr; rearfill is adding echo and your brain sees it as proof that your in a large room. So you gain ambience.


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## oabeieo (Feb 22, 2015)

Jscoyne2 said:


> After building a front sub enclosure. I'll never go back to just a rear sub. Screw all the hoohaa about not being able to locate sound behind you. You absolutely can. Even with perfect t/a.
> 
> Forthought: its been a longgggg time since i read about rear fill. So i could be wrong here but from what i remember. The entire idea of rear fill is to add ambience. What does that actually mean though? Ambience is pretty subjective in what it means on this forum.
> 
> ...



I agree , no matter what anyone says , you can locate the sub from behind , you can make a pretty convincing 1st impression tho… I can make my sub sound like it’s coming from the front , but as the cost of a phase correction gone bad.

It requires hassing in the LF where there’s lots of phase…. So it’s not detrimental to an extreme , but it’s not über precise impulse 

And rear fill iMO is for envolopment reasons and some “ambiance” processing just so it won’t localize , not because ot needs more ambiance.

The front should give all the spaceial ques , if it’s has poor envolopment (dash mids especially) rears can mitigate that…. But it’s mitigation, that’s only a “fix” for something that should be there


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## MythosDreamLab (Nov 28, 2020)

I've been to plenty on concerts that had speakers behind


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## TedDBayer (3 mo ago)

oabeieo said:


> That’s not what he meant


I'll have to live with what I have, maybe not true stereo, more like surround


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## oabeieo (Feb 22, 2015)

TedDBayer said:


> I'll have to live with what I have, maybe not true stereo, more like surround


Like what @UNBROKEN was sayin , if it’s all right everything can come from the front , including the sub 


So , there’s of course arguments to be made , but if you have dsp , it’s just a matter of spending the time and really dial it in so it gives you that effect…

Bass can sound like it’s in the front… not as good as a front sub and some cars better then others , but you should be able to get the illusion with dsp with almost any car …..


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