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-   -   Rear Fill: do you use it? (http://www.diymobileaudio.com/forum/system-design-help-me-choose-equipment-my-car/9806-rear-fill-do-you-use.html)

z_accoustics 03-07-2007 12:45 AM

Rear Fill: do you use it?
 
Is rear fill the dogs bollocks or completely unnescessary?

Thinking of selling my 4ch amp for a 2channel because i'm upgrading my front stage (bye bye rears?).

bobditts 03-07-2007 12:54 AM

Re: Rear Fill: do you use it?
 
keep the 4channel and bridge it to the fronts or run full active

Luke352 03-07-2007 12:57 AM

Re: Rear Fill: do you use it?
 
Whats rear fill, LOL so thats a no for me.

bobditts 03-07-2007 01:35 AM

Re: Rear Fill: do you use it?
 
if I had the money, i would love to try and tackle the issue. I dont have the control or processing power to get the desired results with rear fill. im really interested to see (if it ever happens) the tear down of Mr. Biggs vehicle and see how his rear fill setup was accomplished.

andthelam 03-07-2007 01:36 AM

Re: Rear Fill: do you use it?
 
If you feel the need to entertain rear passengers its a consideration but even so Id turn it down until it was barely audible if cruising solo. For the most part rear fill will just pull your soundstage backwards and I like to hear music and even "see" it coming from out in front of me.

bobditts 03-07-2007 01:39 AM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by andthelam (Post 101308)
If you feel the need to entertain rear passengers its a consideration but even so Id turn it down until it was barely audible if cruising solo. For the most part rear fill will just pull your soundstage backwards and I like to hear music and even "see" it coming from out in front of me.


this is commonly the case. there is a way to actually boost your soundstage with rear fill when its properly dialed in. This is that certain something I was referring to in my last post that I would love to try and accomplish If I had the money.

ahboy 03-07-2007 01:50 AM

Re: Rear Fill: do you use it?
 
nope i dun use rearfills. If u r going to invest on rearfills, why not used all those money to top up for ur front speakers.

Whiterabbit 03-07-2007 04:41 AM

Re: Rear Fill: do you use it?
 
do subwoofers count as rear-fill? :)

demon2091tb 03-07-2007 06:46 AM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by Whiterabbit (Post 101326)
do subwoofers count as rear-fill? :)

Wouldn't even using a low xover point low slope filter some ambient sounds through allowing an almost lowend vocal ambience or reflective sound (more spacious voice). Theoretically if you can keep it non localizable and blended well with midbasses.

Ron G. 03-07-2007 07:36 AM

Re: Rear Fill: do you use it?
 
Yes, I use it. I've tried it with and without. I much prefer it with. The use of rear fill will always be personal preference as nobody can tell anyone else what sounds good to them.

89grand 03-07-2007 09:04 AM

Re: Rear Fill: do you use it?
 
If you have a system with a good front stage and decent dynamics, you'll never miss rear speakers at all. In fact the other day I was playing my system for someone that doesn't know much about audio and he asked if there where speakers in the rear, I said no, and he almost couldn't believe all the sound was just 5 speakers, 4 up front and one sub.

If your system sounds decent, you're not missing anything without rear speakers. My "rear fill" is what ever natural reverberations that take place in the car.

werewolf 03-07-2007 09:49 AM

Re: Rear Fill: do you use it?
 
"rear fill" encompasses many possibilities :

- simple, attenuated L and R
- delayed (beyond Precedence, or Haas, Effect), attenuated, bandlimited L and R
- delayed, attenuated, bandlimited difference signal, L-R

there's a world of difference between these options. Some will confuse the front stage, others will enhance the front stage.

Mr Marv 03-07-2007 10:04 AM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by werewolf (Post 101449)
"rear fill" encompasses many possibilities :

- simple, attenuated L and R
- delayed (beyond Precedence, or Haas, Effect), attenuated, bandlimited L and R
- delayed, attenuated, bandlimited difference signal, L-R

there's a world of difference between these options. Some will confuse the front stage, others will enhance the front stage.

From what I understand one option will raise your stage and as soon as I feel better I'm gonna expereriment with it myself :D.

8675309 03-07-2007 10:27 AM

Re: Rear Fill: do you use it?
 
I have used rear fill in a large vehicle just to help fill in some of the gap. I usually cross from 3500 down and use some form of attenuation on it. My preference is not to use it at all if I dont have too.

I have a friend that is nuckin futs about rear fill. He thinks you get surround sound with a stereo signal running all speakers. I got him a set of nice comps for his truck and cheap coax for the rear. He put the comps in the rear and the coax's in the front!?:rolleyes: He thinks it is the shit. I asked him if he listens to his home or computer speakers turned away from them. His response was I like my sound that way. I want it comming from the back.

What a tard:D

werewolf 03-07-2007 10:34 AM

Re: Rear Fill: do you use it?
 
Your friend isn't the only one who thinks you can get surround from a 2-channel signal ;)

Dolby Pro Logic II, DTS neo:6, Harman Logic7 come to mind ...

Sure, they have more sophisticated steering algorithms ... but have you heard a well-tuned system using a delayed, bandlimited L-R difference signal sent to the rears?

mvw2 03-07-2007 11:11 AM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by bobditts (Post 101299)
keep the 4channel and bridge it to the fronts or run full active

Ditto.

z_accoustics 03-07-2007 11:18 AM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by werewolf (Post 101475)
but have you heard a well-tuned system using a delayed, bandlimited L-R difference signal sent to the rears?

That's a negative over here... so time delay the rears somewhere behind the front stage, cross them over some place and L-R difference? I have a guess but not so sure about what that entails.

JAG 03-07-2007 02:19 PM

Re: Rear Fill: do you use it?
 
As Scooby Doo would say ..... " Absorutely Rot " !!!!

In a concert hall .... ambient sound will reflect off the rear wall ...
In a car ..... ambient sound will reflect off the rear glass ...

Both of these scenarios create natural ambience .... No rear fill is needed.

DonutHands 03-07-2007 02:26 PM

Re: Rear Fill: do you use it?
 
i have the extra amp and i may just hook it up to the stock rear speakers to satisfy passangers.

cvjoint 03-07-2007 02:31 PM

Re: Rear Fill: do you use it?
 
I use rear fill only when passangers are in the back.

I don't see any use for it. Every possible scenario entails more drawbacks than anything. A good solid front stage can only be ruined by a rear stage. Yes you may lift the stage but the depth and staging in general will be ruined.

I was thinking if I ever get my dreamcar I will replace the rear speakers with small subs to help midbass-subbass transition. Only real use if passanger satisfaction is of no concern IMO.

werewolf 03-07-2007 02:58 PM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by AVI (Post 101598)
As Scooby Doo would say ..... " Absorutely Rot " !!!!

In a concert hall .... ambient sound will reflect off the rear wall ...
In a car ..... ambient sound will reflect off the rear glass ...

Both of these scenarios create natural ambience .... No rear fill is needed.

Big difference between a concert hall and car: size of the acoustic space!

And it's NOT just a relative difference ... there's a real, tangible threshold involved, as defined by the Haas Effect. In a car, there's a real good chance that the natural reflections will not exceed the precedence effect (about 20msec, if memory serves) ... meaning that natural reflections will only tend to smear and confuse the front stage. In a concert hall, there's a real good chance that the natural reflections will exceed the precedence threshold.

So if you delay the rear fill by ~20msec or slightly more, you can create an apparent acoustic space that is much larger ... without confusing or ruining the front stage. This is a good thing :) Yes, we face the orchestra in a concert hall ... a classic argument against dumb rear fill ... but we also sense that the concert hall is bigger than about 25 cubic feet ... a very good argument in favor of smart rear fill :)

How to best accomplish it, is perhaps a discussion for another thread. You need a processor with time alignment, and the ability to bandlimit the rears. The difference signal can be formed either actively before the amp (trivial with balanced signals, not even hard with transformers and single-ended signals), or speaker-level after the amp (the classic Hafler matrix was the old, dumb example ... with no time delay, and even only crude attenuation and bandlimiting). But here's an interesting link for further reading:

http://www.mlssa.com/surround/surround3.htm

Of course, you may want to consider the options mentioned above ... Dolby Pro Logic II (invented by Fosgate with an automotive acoustic space in mind), DTS Neo:6, and the new Harman Logic7 processor for the car (which, by the way, is starting to get some very encouraging reviews). All of these options create a multi-channel signal from a 2-channel source, and make very intelligent use of speakers behind your head :)

I guess my main point is this : all "rear-fill" is not created equal :) It's important to distinguish what type, before we summarily embrace or dismiss the entire category.

JAG 03-07-2007 03:14 PM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by werewolf (Post 101625)
Big difference between a concert hall and car: size of the acoustic space!

And it's NOT just a relative difference ... there's a real, tangible threshold involved, as defined by the Haas Effect. In a car, there's a real good chance that the natural reflections will not exceed the precedence effect (about 20msec, if memory serves) ... meaning that natural reflections will only tend to smear and confuse the front stage. In a concert hall, there's a real good chance that the natural reflections will exceed the precedence threshold.

So if you delay the rear fill by ~20msec or slightly more, you can create an apparent acoustic space that is much larger ... without confusing or ruining the front stage. This is a good thing :) Yes, we face the orchestra in a concert hall ... a classic argument against dumb rear fill ... but we also sense that the concert hall is bigger than about 25 cubic feet ... a very good argument in favor of smart rear fill :)

How to best accomplish it, is perhaps a discussion for another thread. You need a processor with time alignment, and the ability to bandlimit the rears. The difference signal can be formed either actively before the amp (trivial with balanced signals, not even hard with transformers and single-ended signals), or speaker-level after the amp (the classic Hafler matrix was the old, dumb example ... with no time delay, and even only crude attenuation and bandlimiting). But here's an interesting link for further reading:

http://www.mlssa.com/surround/surround3.htm

Of course, you may want to consider the options mentioned above ... Dolby Pro Logic II (invented by Fosgate with an automotive acoustic space in mind), DTS Neo:6, and the new Harman Logic7 processor for the car (which, by the way, is starting to get some very encouraging reviews). All of these options create a multi-channel signal from a 2-channel source, and make very intelligent use of speakers behind your head :)

I guess my main point is this : all "rear-fill" is not created equal :) It's important to distinguish what type, before we summarily embrace or dismiss the entire category.

Very good info .... However the majority will mess up the front-stage , before ever getting the perfect rear stage set-up .... Then again , this is the DIY tweakers forum :D

8675309 03-07-2007 03:15 PM

Re: Rear Fill: do you use it?
 
Quote:

Originally Posted by werewolf (Post 101475)
Your friend isn't the only one who thinks you can get surround from a 2-channel signal ;)

Dolby Pro Logic II, DTS neo:6, Harman Logic7 come to mind ...

Sure, they have more sophisticated steering algorithms ... but have you heard a well-tuned system using a delayed, bandlimited L-R difference signal sent to the rears?


Harman 7 home reciever Got one in the house

Sure, they have more sophisticated steering algorithms. Exactly!

They are not running strait stereo?.:D

werewolf 03-07-2007 03:22 PM

Re: Rear Fill: do you use it?
 
Ahh but the important question is : how different is the Harman rear signal generation from : a delayed, bandlimited, L-R difference signal? (which does not require Logic7 to construct)

werewolf 03-07-2007 03:27 PM

Re: Rear Fill: do you use it?
 
And also : If a Logic7 processor was available for your car (hint), would you reconsider the use of rear speakers?


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