# Rear Fill, my Observation



## 04quadcab (Dec 31, 2017)

I know there is a lot of debate about rear fill and I understand the argument that it messes with the front stage.

https://www.diymobileaudio.com/foru...iscussion/326098-rear-fill-not-rear-fill.html

My setup is nowhere near the SQ setup that many of you have (I am working on fixing that ), it is just some entry-level coaxials in all four doors and some entry level subs. But, in my experience the rear fill has not diminished the front stage. I have been actively playing with it in an attempt to figure out what I was missing. My deck has a feature that will delay/speed up the rears to widen/narrow the front sound stage. It has an effect, but not a big effect. I have tried running with the fade set to the front or the middle. No big difference.

But then, something odd happened. I loaded up the family to take the kids to grandma's house. My wife jumped in the front seat and pulled the seat forward to make room in the back for my son's legs (he is 13 and about 6'2"), and BAM everything sounded like CRAP! The right rear door speaker was BLARING and it sounded like NOTHING was coming out of the right front speaker. I immediately started adjusting the fade and balance thinking that the passenger door front speaker had stopped playing. It took me way to long to figure out what was going on.

The front passenger seat had been blocking the sound from the right rear door speaker. When my wife slid the seat forward it blocked the front door speaker and exposed the rear speaker. 

I am usually in my truck alone, or with the kids. The entire family does not spend that much time in the truck together, and it was only recently that my wife had to move the seat forward to accommodate a rear seat passenger. This is why I never understood why rear fill was so bad. Now that I have heard it I cannot unhear it. I plan to keep running the rear speakers since I often have a rear seat passenger. But, I get it now. Rear fill can really mess things up!


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## seafish (Aug 1, 2012)

There is only one correct way to tune for and begin to experiment with Rear Fill and that is to use channels that are bandpassed between approximately 300-3000Hz, are delayed beyond 20ms of the front channels and are also volume attenuated. By doing all of the above, you CAN in fact achieve an "ambiance" effect that often will complement a properly tuned front stage.
IOW when done right with proper implementation and tuning, it can sound GREAT!!!

That being said, it is ALOT of work to do it right and, as you just found out, can seriously mess with the front stage when NOT done right!!


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## naiku (May 28, 2008)

seafish said:


> There is only one correct way to tune for and begin to experiment with Rear Fill and that is to use channels that are bandpassed between approximately 300-3000Hz, are delayed beyond 20ms of the front channels and are also volume attenuated. By doing all of the above, you CAN in fact achieve an "ambiance" effect that often will complement a properly tuned front stage.


Exactly this, and if done right what you will hear from the rear speakers sounds really odd. It's difficult to describe, but you would just be hearing little parts of the music, not everything and not something you would want to listen to without the front speakers playing.

I have mine delayed 25ms and playing from I think 450Hz up to 3500Hz and am very happy with it. Certain songs it's not noticeable at all, others it adds a nice effect, and if I switch it off I lose a ton of ambience.


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## dcfis (Sep 9, 2016)

naiku said:


> Exactly this, and if done right what you will hear from the rear speakers sounds really odd. It's difficult to describe, but you would just be hearing little parts of the music, not everything and not something you would want to listen to without the front speakers playing.
> 
> I have mine delayed 25ms and playing from I think 450Hz up to 3500Hz and am very happy with it. Certain songs it's not noticeable at all, others it adds a nice effect, and if I switch it off I lose a ton of ambience.


What are you processing with


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## SkizeR (Apr 19, 2011)

listen to a car with it done right. better yet, try to have someone who knows how to make it right turn it on and off, and even adjust settings with you listening. I have done this for a few people. Everyone has picked rear fill. If its messing up your front stage your not doing it right, or your not doing it well.


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## naiku (May 28, 2008)

dcfis said:


> What are you processing with


Mini DSP C-DSP 8x12


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## 04quadcab (Dec 31, 2017)

seafish said:


> There is only one correct way to tune for and begin to experiment with Rear Fill and that is to use channels that are bandpassed between approximately 300-3000Hz, are delayed beyond 20ms of the front channels and are also volume attenuated. By doing all of the above, you CAN in fact achieve an "ambiance" effect that often will complement a properly tuned front stage.
> IOW when done right with proper implementation and tuning, it can sound GREAT!!!
> 
> That being said, it is ALOT of work to do it right and, as you just found out, can seriously mess with the front stage when NOT done right!!


My deck has an independent level control for front and rear built into the crossover menu. For a good 6 months or so I ran the crossover in the rear down 6 or 9 DB from the front. I recently added a 4 channel amp and have left the levels the same in the front and the rear. I usually run the rear high pass filter around 125 hertz. With the fronts at 80 hertz. So basically I've been steadily working my way toward your recommendation. I think I might experiment more with the time delay settings on the deck. I'm mostly happy with my sound so I've not really explored everything that my head unit can do.

Sent from my Pixel XL using Tapatalk


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## Grinder (Dec 18, 2016)

Thanks, guys. I think I finally understand what constitutes rear fill, and what it is for.


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## Gump_Runner (Aug 2, 2014)

SkizeR said:


> listen to a car with it done right. better yet, try to have someone who knows how to make it right turn it on and off, and even adjust settings with you listening. I have done this for a few people. Everyone has picked rear fill. If its messing up your front stage your not doing it right, or your not doing it well.


Well Said.


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## 04quadcab (Dec 31, 2017)

seafish said:


> There is only one correct way to tune for and begin to experiment with Rear Fill and that is to use channels that are bandpassed between approximately 300-3000Hz, are delayed beyond 20ms of the front channels and are also volume attenuated. By doing all of the above, you CAN in fact achieve an "ambiance" effect that often will complement a properly tuned front stage.
> IOW when done right with proper implementation and tuning, it can sound GREAT!!!
> 
> That being said, it is ALOT of work to do it right and, as you just found out, can seriously mess with the front stage when NOT done right!!


I am assuming that you use a stereo signal for this?


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## seafish (Aug 1, 2012)

04quadcab said:


> I am assuming that you use a stereo signal for this?


Mono will work better then Stereo but what you REALLY need is a (L-R) signal so that all the common center info is left out.

Then you bandpass it, attenuate it and delay it to create an effect that is BARELY there.


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## seafish (Aug 1, 2012)

Here is some more reading on it--

https://www.diymobileaudio.com/foru...71218-rear-fill-l-r-stereo-mono-question.html


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## ckirocz28 (Nov 29, 2017)

One thing I discovered when trying rear fill, when mixing L-R, use the same eq for both channels or it will sound really messed up. I've never seen that mentioned anywhere.


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## JimmyDee (Mar 8, 2014)

I've been experimenting with rear fill for years (even when it was unpopular to admit it)... and I've learned a lot.
Most of my early systems sounded dreadful, and I could never get it to sound good.

As mentioned in a few posts above, it's a mix of many things. 
In my current install, using Audiofrog GB40 and GB10 components, I've found this combination sounds best:
* Time delay of 26mS
* Bandpass at 300Hz to 7,000Hz (lots of experimenting with a 2-way) 
* Rear midrange is set at -6dB
* Rear tweeter is set at -9dB

I know the argument about how rear fill can skew the listening stage, and I won't argue that.
However, I feel like I've (almost) mastered rear fill... and when done right, it definitely adds to the whole listening experience.
My sound stage is absolutely right in front of me, and the rear does just what it's supposed to do... slightly fill the rear.


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## JimmyDee (Mar 8, 2014)

My best advice on rear fill, is this; _Don't do it, unless you can afford to do it._
What I mean by this, is; don't pull money away from your front stage budget, to add rear fill.

Rear fill is expensive (relative to what you get back from it).
Not only do you need to add more speakers, but you need to factor more amplifier channels and more DSP channels.
It really adds-up.


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## nadams5755 (Jun 8, 2012)

ckirocz28 said:


> One thing I discovered when trying rear fill, when mixing L-R, use the same eq for both channels or it will sound really messed up. I've never seen that mentioned anywhere.


I start out with a stereo signal and a bandpass crossover. Then eq the sound flat’ish like i would front sound, from the listening position. Then center the rear fill with relative levels and time alignment. Then l-r/r-l mix the signal, add delay and reduce levels. 

Too much delay, it sounds echoed. Not enough delay, it pulls back. Too much level pulls back or echoed. Too low, no effect.

If rearfill enabled causes my stage to dance, I check levels per rear channel.


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## bbfoto (Aug 28, 2005)

^Nick, that's probably the best explanation that I've read of how to go about it and the differences each adjustment will make. :thumbsup: 

It's really difficult to convey proper "differential rear fill" without actually trying it and listening to the effects yourself. Of course, the settings will all be different for each vehicle, and dependent upon where the rear fill speaker(s) are placed. It also will make a difference if they are directly on-axis or off-axis.

Generally IME, Off-Axis will achieve a bit better sense of Width and not as much depth, and the opposite when more On-Axis. But On-Axis with a relatively clear path to the listening position has worked best to achieve a good combination of both width & depth + ambience in my setups.

It's important to note that it doesn't work with all tracks or music, and you can also experience some weird effects on some songs...it depends on how they were mixed to achieve their main L/R stereo effect.


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## karmajack (May 9, 2017)

My question is...
What DSP's have the capabilities to even attempt this? 
The few that I've seen don't allow anywhere near 20ms of delay. Let alone making a L -R signal. Granted I'm not familiar with many DSP's at all, and those few are the budget tier. I've read the Helix can. But what others?


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## seafish (Aug 1, 2012)

karmajack said:


> My question is...
> What DSP's have the capabilities to even attempt this?
> The few that I've seen don't allow anywhere near 20ms of delay. Let alone making a L -R signal. Granted I'm not familiar with many DSP's at all, and those few are the budget tier. I've read the Helix can. But what others?



Helix software can do L-R in varying percentage as can the Mini DSP and the just released and also inexpensive Dayton DSP. IIRC, the newest Helix software has BOTH input and output delay which can be used. 

It's true that most DSP don't have more then 20ms of delay, but that seems to work for many people. The newest APL (fir based) DSP has up to 45ms delay but is going to cost a pretty penny. 

Alpine H800 has rear fill with Dolby Pro Logic 2
Rockford RFQ5000 has rear fill Dolby Pro Logic 2
JBL MS8 has rear fill with Logic 7


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## karmajack (May 9, 2017)

seafish said:


> Helix software can do L-R in varying percentage as can the Mini DSP and the just released *and also inexpensive Dayton DSP.* IIRC, the newest Helix software has BOTH input and output delay which can be used.
> 
> It's true that most DSP don't have more then 20ms of delay, but that seems to work for many people. The newest APL (fir based) DSP has up to 45ms delay but is going to cost a pretty penny.
> 
> ...


If you know how to do L -R on a Dayton 408, please inform me. I have one going in sometime soon, and I want to toy with this sometime.


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## 04quadcab (Dec 31, 2017)

seafish said:


> ... and also inexpensive Dayton DSP. IIRC


I hope so, I just picked one up.

My plan is to run a three way front stage, the mids and tweets are under the Christmas tree. I have some SB17's for midbass. 

My challenge is to figure out how to process the rear fill and the subs. I need 10 channels to do what I want. My deck has time delay and a good crossover/EQ. I will either use the deck for the subs so I can use the DSP to work out the rear fill or vise-versa.


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## nadams5755 (Jun 8, 2012)

karmajack said:


> My question is...
> What DSP's have the capabilities to even attempt this?
> The few that I've seen don't allow anywhere near 20ms of delay. Let alone making a L -R signal. Granted I'm not familiar with many DSP's at all, and those few are the budget tier. I've read the Helix can. But what others?


minidsp 2x4/2x4hd with the center/rearfill gets you up to 27ms https://www.minidsp.com/products/plugins/rear-center-channel-detail
https://www.minidsp.com/images/documents/Product Brief-Rear-Center channel plug-in.pdf

chain off your main dsp for just delay, or chain off your head unit's rear channel outputs (latter leaves rear levels at your fingertips w/ fader control)


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## Holmz (Jul 12, 2017)

jimmydee said:


> I've been experimenting with rear fill for years (even when it was unpopular to admit it)... and I've learned a lot.
> Most of my early systems sounded dreadful, and I could never get it to sound good.
> 
> As mentioned in a few posts above, it's a mix of many things.
> ...


Thanks for ^those number^.


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## nadams5755 (Jun 8, 2012)

i've got AP AR3-Ps for rear fill.

AR3-P on the right, compared to AR3-A on the left. AR3-P has more high-end extension than the AR3-A, which i felt was more vaulable









i tried 300-3000/6db. tried at 7k as well, also tried high-pass only. not much of a difference in my book. i might try it again this year as i get the front more dialed in.

my rearfill are in the c-pillars facing the opposite rear passenger-assist (oh ****) handles. i don't need any additional width so depth is what i was after. it also keeps the speaker pods subtle and non-obstructing.

in my car: if the right rearfill is too hot, right of center pulls UP and right. if the left rearfill is too hot, the left side pulls towards the listener creating the 'horseshoe' effect.

net effect in my car? better sense of room and stage. sense of stage/room was more impacted by my tweeters and high frequency extension. getting the front-stage tune correct meant getting stage depth/layering for free.

if you can get the trumpet on sara k's "if i could sing your blues" correct, you're onto something.  you can find it on various chesky discs. 
https://www.youtube.com/watch?v=_OItKgDwctg


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## jrock645 (Apr 15, 2015)

I can fade my rear speakers up and down with clickable sub know, and it unquestionably sounds better with rears at full volume. Just better richness and balance.

Running hertz Mille 3 way front and coax rear with 5 channel vxi’s. Had a shop tune it, so not entirely sure how they set it up.


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## bbfoto (Aug 28, 2005)

nadams5755 said:


> ...
> 
> If you can get the trumpet on sara k's "if i could sing your blues" correct, you're onto something.  you can find it on various chesky discs.
> https://www.youtube.com/watch?v=_OItKgDwctg


Agreed! This is one of the absolute best tracks to demonstrate this.  It's great when you can quickly toggle the rear fill on/off or fade it in and out.

*bbfoto DIYMA SQ TRACKS [TEMP]*

I've been meaning to put together a complete list of other tracks that demonstrate this really well, and that have excellent staging and extreme depth in general. Someday I'll get to it.


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## Ziggyrama (Jan 17, 2016)

Now I am curious to try it. My rear find is pretty well dialed in but I'd like to test it out. If you have any other test tracks, please post them up.


bbfoto said:


> Agreed! This is one of the absolute best tracks to demonstrate this.  It's great when you can quickly toggle the rear fill on/off or fade it in and out.
> 
> *bbfoto DIYMA SQ TRACKS [TEMP]*
> 
> I've been meaning to put together a complete list of other tracks that demonstrate this really well, and that have excellent staging and extreme depth in general. Someday I'll get to it.


Sent from my Pixel using Tapatalk


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## CDT FAN (Jul 25, 2012)

With the MS-8, 99% of the time, I am not aware that the rear speakers are playing, but I know they are making a difference in the ambiance. Only if I turn my head sideways and intentionally listen for them will I hear them. However, the first time I really distinctly heard them was with The Mamas and the Papas , California Dreaming. The backup singers were clearly coming from the rear speakers. I was like, WOW, that's a nice effect.


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## JCsAudio (Jun 16, 2014)

I know this doesn't really apply to the SQ camp generally on here but I own a Toyota Sienna minivan for the chids (kids) and have rear fill coaxial s run off the HU power and attenuated so it doesn't distract from the front stage. They are way back there at the third row and it helps the kids actually hear the music playing or with movies when those are playing. I think running rear fill in this fashion is worth it because you can always fade/turn it off for when its just you in the vehicle. I do not run rear fill in my SUV though because its too small to make a difference. They were really inexpensive Kicker coaxial speakers and I had to sit back there once during a drive in movie and was kind of impressed at how decent they actually sound. It also helps for rear passengers because with the subwoofer in the rear closer to them, all they would hear otherwise is bass.


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## nadams5755 (Jun 8, 2012)

some other tracks i use for depth/sense of space:

sunny sumter's nick of time (meca bonus tracks): should have a good 3 layers of depth. (some systems only have two layers) vocals center, upright bass left of center and behind, piano in the back/left.

rebecca pidgeon's auld lang syn / bring it on home: should have a good sense of large stage and large room. (some only have sense of stage, only sense of room, or none)

wycliffe gordon's won't you come home bill bailey: should sound like a large stage and large room. trumpet should be nearly all the way left. trombone should be further left and behind the trumpet. drums should be in the back and right of center. tuba left of center in the back. woodwinds right and front. banjo right of center and front. brass rip about 3:30 should rip should reverberate right and about half way back across the stage.


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## ckirocz28 (Nov 29, 2017)

nadams5755 said:


> i've got AP AR3-Ps for rear fill.
> 
> AR3-P on the right, compared to AR3-A on the left. AR3-P has more high-end extension than the AR3-A, which i felt was more vaulable
> 
> ...


So where is the trumpet supposed to be? It appears to be over my right headlight.


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## nadams5755 (Jun 8, 2012)

ckirocz28 said:


> So where is the trumpet supposed to be? It appears to be over my right headlight.


the previous/intro track description is 'ten feet from the microphone'. i usually place it right of center in the back.


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## ckirocz28 (Nov 29, 2017)

nadams5755 said:


> some other tracks i use for depth/sense of space:
> 
> sunny sumter's nick of time (meca bonus tracks): should have a good 3 layers of depth. (some systems only have two layers) vocals center, upright bass left of center and behind, piano in the back/left.
> 
> ...





nadams5755 said:


> the previous/intro track description is 'ten feet from the microphone'. i usually place it right of center in the back.


These descriptions would appear to be the perfect arguments FOR rear-fill. Also, thanks.


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## nadams5755 (Jun 8, 2012)

For me, most of these stage cues come from a well tuned front stage and good high frequency extension. 

Get the tonality correct and you get the staging/depth stuff for free.


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## gijoe (Mar 25, 2008)

nadams5755 said:


> For me, most of these stage cues come from a well tuned front stage and good high frequency extension.
> 
> Get the tonality correct and you get the staging/depth stuff for free.


This is pretty much my opinion too. 

If you tune the front stage well, which involves a good amount of measuring and *requires* L/R EQ, then the sense of space and ambience will be there. 

I think people use rear fill as a band aid too often to fix what could have been accomplished with the front stage and a good tune in the first place. 

If you have the front tuned well, and add proper rear fill, the results can be great, but for me it's still synthetic and I'd much rather save the money on speakers and amp channels and spend my time on optimizing the front.


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## bravesbaseball17 (Sep 15, 2018)

Damn...why did I have to read this thread?! I was doing just fine yesterday, when I thought I could simply hook the (brand new) rear speakers back into my system like factory spec and go about my merry way...lol


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## rob3980 (Jun 11, 2010)

I just heard a car that competes when the guy turned his rear speakers on it seemed like the sound stage widened . It was pretty crazy. I wish I would have gotten pics of the rears they were in the trunk. You can kind of see where they were located in the trunk pic in the bottom right corner of the pic This thing sounded amazing.


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## rockinridgeline (Feb 2, 2009)

I think rear fill is a matter of preference and whether you are trying to compete to a standard or listen for fun. 

In my 911, the mids are in the doors and the tweets in the A pillars. I am using the factory Bose speakers in the rear side panels for rear fill with the Helix DSP doing a L-R with a lot of delay as described here by others. If I were to compete with the car, I would likely turn off the rear fill because with the front seat all the way back, the listener is very close to the driver side rear fill. If the recording has left information panned hard to that side, the soundstage will pull down and to the left. Same thing on the right but not as much. 

However, for everyday driving it is very enjoyable. The sense of envelopment and presence is very fun to listen to. On pop music that has been engineered with hard left and right vocal splits (no idea what the actual recording term is, but I am trying to describe the effect when the vocals don't come from the center but are slightly different signals to the left and right speakers) there is an interesting almost headphone like effect. On simpler recordings with instruments to the far left and right there are imaging cues well outside the boundaries of the A pillars. I find the sense of envelopment fun and entertaining. In fact, it helps me to listen and enjoy the music rather than constantly analyzing the sound, which I am prone to do.


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## troy.lawrence.58 (Jan 9, 2019)

I'm new here guys so here is the info on my build. I will be a bit long winded until I talk about my rear fill experience because I want you all to know everything about my system. About a month ago I had a shop install a Linkswell T style radio in the dash of my 2017 F250. I immediately noticed a huge difference in sound quality over my stock Sony radio. 

Two weeks ago I returned to the same shop in which they installed Focal KX2 6.5 components in the front powered by a Helix P Six Dsp Mk2. I also had the cover both of the front doors with Soundskin as well as the using the soundskin speaker cover. In addition, under my rear seat they installed 2 10 inch Focal Flax P25 subwoofers(inside of a Foxbox) powered by a JL Audio HD 600/1 amplifier. Initially I had a JL Audio JX1000/1D but was told that would have been waaaaay too much power so I decided to return the JX1000/1D and utilize the HD 600/1. 

Ok initially I wasn't impressed with the sound quality of the Focal Speakers so I was told give them a week or two so they could break in. In addition, I went along with their tune and never really tweaked anything. 

REAR FILL EXPERIENCE:

Ok.........after the last install, I was told that until my speakers(Focal EC 165 coaxial) for the rear doors arrive, they would turn off my rear factory Sony speakers from the Helix DSP because the factory speakers will mess up my sound stage. So up until this past weekend I wasn't impressed with the midbass coming from the front speaker as they sounded too flat. So, I decided to use my laptop to access the Helix DSP and play around with the eq settings. After reading numerous different post and forums, I took my time and began adjusting some settings one speaker at a time and they began to WAKE UP! Then I decided to turn on my rear Sony stock speakers from the Helix and I was shocked as to how good they made my system sound. After spending several minutes adjusting their EQ settings and I was floored as to how well they sounded! 

Afterwards, I spent time turning off and on the rear speakers to make a decision for myself as to the rear speakers messing up the sound stage. WOW, THEY SOUND SOOOOO DARN GOOD WITH THE REAR SPEAKERS! It was a very noticeable difference in sound quality. I had several people listen as I turned on and off my rear speakers and everyone quickly agreed that the rears made a huge difference. Keep in mind these are the stock rear speakers because my Focal's for the rear will not arrive until today. But Holy Moly...........I'm glad I turned those rear speakers on and tuned them as well as the front speakers! I can only imagined what the system will sound like once I install the Focals in the rear. 

I can't thank this website/forum enough for some of the good information that I have acquired over the past 2 weeks! 

BTW, I don't have any echoing as reported by some and I didn't have to toggle with the Time Alignment settings for the rear speakers. Not sure if the installation shop previously set all of that up before turning off the speakers from the DSP. And yes my fader works as it should. I must say that the shop did an awesome job with everything.

Sent from my SM-N950U using Tapatalk

Sent from my SM-N950U using Tapatalk


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## JCsAudio (Jun 16, 2014)

Troy,

I agree and if it sounds good to you than you should keep it. I currently run my stock Ford 6*8 woofers with a DSP and amplifier on them active with some tang bang tweeters and they also sound surprisingly good. You may find that the focal speakers are less efficient and might be slightly more clear but have less volume and midbass if they are not amped.


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## preston (Dec 10, 2007)

This is a repost from another thread on rear fill. I thought it might be good to put it here on a more official rear fill thread.
---------------
I recently finished a big install in my crew cab Sierra. Always planned to do rear fill but didn't follow through because I felt like I'd have to go out and buy a Helix Pro to get 10 channels instead of teh 8 on my Helix basic.
The stock head unit is feeding the helix via a NavTV interface box, but I had left the rear door speakers connected to the deck. If I took the fader off of full front, it would bring them into play. Although there was a lot of problems with the sound, I still found that I kept turning them on and off, abck and forth because I have always liked the ambience of rear fill.


Had to take some stuff apart to install a Director so I ended up putting a little class D amp in the console where the factory "subwoofer" used to go, and then I pulled the doors apart and did the full soundproofing and built baffles and replaced the truly crappy OEM (Bose) speakers with some Legatia L4's I had laying around. It actually turned into quite a project.

I had been summing two channels to the sub, so i changed that over to a mono feed and I had one mono feed left for rear fill. I know its not the proper L-R, and R-L processing but like I said I've always enjoyed rear fill of any sort. I put the maximum delay I could on it - in my system the longest delay is about 5ms, and the most I could put in the rear fill is 15mS, so the overall delay is only about 10ms. I went ahead and set up the mic and level set them and even EQ'ed them, and run them from 350Hz and up.

So - mono, not differential. Low in doors, fairly close to the front seat and completely off axis. Less than ideal compared to the theory.

And - I absolutely love it. Adds so much "space" to the sound with no loss of cohesion. Stage isn't necessarily wider or deeper, its "thicker". Ha ha stupid audiophile words but that' how it sounds to me. Instruments are richer and take up more individual space. It really made my favored jazz combos feel more "there" and orchestra stage is vastly improved. I spent about 3 hours just raising the rear volume up and down and muting the rears on and off and 100% enjoyed it more with rear fill even if I'm not following all the Hasselhoff principles (ha don't remember the actual name). And needless to say it is a huge improvement over whatever the oem speakers were doing, and another upside the rear passengers are getting a much nicer sound as well.


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## Hillbilly SQ (Jan 26, 2007)

Would y'all say that the shape of the cabin has a big effect on whether or not rearfill is a good idea? For example my previous vehicle was a Grand Cherokee with stock speakers high up in the d-pillars playing nearly on axis. I ran rears in it for more than half the time I had a system in it. Since I had to have the drivers seat raised all the way up and moved forward quite a bit (short, stocky, and mostly German, lol) the rears being nearly on axis helped push the front stage forward to get it out of my face while driving. I started off using an old mini 2x4 with the center/rear plug-in tapped into my mini 6x8 and then ended up with the mini 8x12 later on. 

Traded in the Jeep after 2 years of ownership to get back into a real truck that I wouldn't feel bad about using as a...TRUCK and tow rig! Got back into a single cab (didn't need or want another quadcab) and debated using rearfill. The cab is a mile wide and stock rears are off axis. If I did rears I'd want to fire them forward or up to help push the stage forward. I'm not sure if I would ever be able to get things dialed in with the drivers side rear being just a few inches from head. I might try it at some point since I have the capabilities and could mount the speakers in pods on top of the subwoofer enclosure. While I'd like to try I also know that it would end up being a rabbit hole. I would like to get the stage moved further forward on the hood but I'm only about 90% there on the tune. The last 10% is the hard part. 

If you've read this far and didn't just skim my long winded post you've probably figured out rearfill isn't completely written off on things to try but it's at the very bottom of the list. Just don't think a single cab would react well to it.


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## kanadian-kaos (Sep 12, 2010)

The best "rear fill" I experienced was an old Cherokee with the speakers in the rear hatch as far away as possible with DSP processing. I think rear speakers suit large cabins better.... like large SUV's or minivans (but not in the rear passenger doors) so that the rear passengers hear them but the driver barely does. I wouldn't do it in a single cab.

I have to do rear fill now because of kids. They did not enjoy my little hatchback with only an active front stage and subs in the back... they said it was too much bass and they could not hear the music... little critics.


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## JCsAudio (Jun 16, 2014)

I tried rear fill in my single cab F150 and quickly realized it wasn’t for me but the rear fill in my Sienna works well. I guess I agree with Hillbilly.


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## nadams5755 (Jun 8, 2012)

Ram quad cab factory roof mounted down firing rears work well. I’ve also seen people put rearfill in the back pillars next to the rear glass in extended and quad cab trucks. I’ve not seen it done in single cabs. That said, with the rest of your system together, try some bookshelf or surround speakers in the truck and play with aiming, time alignment, delay, etc. given it’s a truck, you probably don’t need any more width, just depth. So try firing forward or cross-corner first.


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