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Thread: How to rear fill

  1. Back To Top    #11
    Noob Jdunk54nl's Avatar
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    Re: How to rear fill

    Quote Originally Posted by naiku View Post
    In my experience, using those door speakers near the B pillar, located low in the door, is not that good for rear fill. They're too close to the front, in order to have them not interfere with the front stage they're (again, this was in my car) dialed back so much it's not worth it. Moving them back to the sides of the trunk, between C and D pillars made them much more effective.

    In my new vehicle I'm hoping to figure out a way to mount rear speakers in the D pillar, otherwise I'll just skip running rear fill.
    Yup, not ideal placement, but so far it does add to the sound and isn't really taking anything away. My center is still centered and my right/left are still right/left. The right left are being pulled back a little, so I need to adjust something, but I need to play with time and volume some more.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  2. Back To Top    #12

    Re: How to rear fill

    i've had rear-fill installed in my car, ready to use for over a year now. however, it's been off most of this time. why? it's tough to get right and ruins staging cues when it's wrong.

    copied some of my garbage comments over from diyma from a thread about rear-fill:

    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 shit) 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


    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.

    with the rest of your system together, try some bookshelf or surround speakers in the vehicle and play with aiming, time alignment, delay, etc

  3. Back To Top    #13

    Re: How to rear fill

    and a little more related to my experience tuning rear fill:

    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.

  4. Back To Top    #14

    Re: How to rear fill

    I finally tried true differential rear fill for the first time with my Helix DSP.3 - wasn't my cup of tea (added so little that I didn't find it very beneficial). Although, I was using the highest delay allowed by the DSP.3 (about 20ms) since everything I read said 20ms+. Maybe I should try lower delay amounts.

    Ended up going back to attenuated, delayed and bandpassed "rear speakers" instead. :-)

    I have the rears (in rear deck on Dodge Challenger) playing 75hz-4000hz, approx 8-10dB lower than the fronts with about a 10ms delay. I like the extra "fullness" it gives without noticeably pulling the front stage back at all. I tried fronts only for a while and just prefer the rear speakers being on.

    Will probably experiment more with differential rear fill at some point, but was not fond of the initial results.

  5. Back To Top    #15
    Noob Jdunk54nl's Avatar
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    Re: How to rear fill

    Quote Originally Posted by jtrosky View Post
    I finally tried true differential rear fill for the first time with my Helix DSP.3 - wasn't my cup of tea (added so little that I didn't find it very beneficial). Although, I was using the highest delay allowed by the DSP.3 (about 20ms) since everything I read said 20ms+. Maybe I should try lower delay amounts.

    Ended up going back to attenuated, delayed and bandpassed "rear speakers" instead. :-)

    I have the rears (in rear deck on Dodge Challenger) playing 75hz-4000hz, approx 8-10dB lower than the fronts with about a 10ms delay. I like the extra "fullness" it gives without noticeably pulling the front stage back at all. I tried fronts only for a while and just prefer the rear speakers being on.

    Will probably experiment more with differential rear fill at some point, but was not fond of the initial results.
    Your "regular" rear settings is about what I have for my rear fill except I have mine L-R. Try leaving everything the same and just do L-R (To get R-L just reverse the right side speaker wires at the amp).
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

  6. Back To Top    #16

    Re: How to rear fill

    Jtrosky are you saying that "true rear differential rear fill" is processing that the Helix does ? Not just (L-R) (R-L) as mentioned above by Jdun54nl ?
    The fact that you like rear speakers playing but not "true rear fill" is interesting.
    I'm confused about what specifically you tried that you didn't like.
    Are you rear speakers playing in stereo or mono now ?
    I actually think 20+ms delay is probably too much, did you try "true rear fill" with less delay like the 10ms you are using now ?

  7. Back To Top    #17

    Re: How to rear fill

    Quote Originally Posted by preston View Post
    Jtrosky are you saying that "true rear differential rear fill" is processing that the Helix does ? Not just (L-R) (R-L) as mentioned above by Jdun54nl ?
    The fact that you like rear speakers playing but not "true rear fill" is interesting.
    I'm confused about what specifically you tried that you didn't like.
    Are you rear speakers playing in stereo or mono now ?
    I actually think 20+ms delay is probably too much, did you try "true rear fill" with less delay like the 10ms you are using now ?
    Yes, the Helix allows you to set up true differential rear fill. Here is a post by Nick over on DIYMA that explains the procedure (it's actually really quick and easy to setup). You don't need to change any physical wiring or anything.

    https://www.diymobileaudio.com/threa...ix-dsp.307730/

    I know I tried it with ~20ms of delay for a few drives and just found that I didn't like it as much as the setup I normally use (stereo, attenuated, bandpassed "rear speakers"). I get a much "fuller" sound (with same levels) this was vs. real differential rear fill.

    I do think I very briefly tried ~10ms delay as well, but didn't keep it that was very long as I always read that 20ms+ of delay was normally needed for "proper" rear fill. So I left it at that. Either way, it just didn't add enough to the overall sound for me compared to what I do now. Maybe I need to increase the levels a little too though.

    EDIT: OR... Maybe what I'm doing on the Helix really isn't *true* differential rear fill? I honestly don't know for sure... I do know that I got absolutely no sound from the rear speakers while playing my tuning pink noise though (which I think confirms that it was setup correctly)! :-)

    EDIT2: Here is another cool site talking about different types of rear fill - found it interesting and informative: https://glasswolf.net/papers/rearfill.html
    Last edited by jtrosky; 03-06-2020 at 02:57 PM.

  8. Back To Top    #18

    Re: How to rear fill

    If you’ve got your rear outputs on another set of inputs, you could add input delay to add another 5-10ms on the helix

  9. Back To Top    #19

    Re: How to rear fill

    Hi. Apologies for necromancy, but this looks like the right place to post.

    I've been reading over how to do some kind of differential rear fill and am uncertain about wiring. The message above says, "reverse L- and R+". Okay, here's a picture of that: https://i.imgur.com/IrjujcZ.png

    Is that intended? Send positive signals from both LR to L, and negatives only to R? If "reverse means swap with one another," that's the diagram.

    I didn't even know speakers could work at all in a config like this, haha.

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