DiyMobileAudio.com Car Stereo Forum banner

1 - 20 of 69 Posts

·
Registered
Joined
·
17,677 Posts
Discussion Starter #1
this subject has peaked some interest lately and i have been getting questions from others on how to do it, and i have been asking others about implementing it correctly. Lets discuss all of that here i guess. First things first, this is how to set up L-R/R-L rear fill on the helix processors. credit of course to ErinH, as i learned about this in his build log. I just made this so i dont have to direct everyone to a specific post in there.

1) lets assume im using a pair of full range coaxials in the rear just to make it simple. in the input matrix, set your channels to rear left full, and rear right fill. drag and drop the appropriate inputs to the matrix like so..







2) next step is to drag and drop the opposite sides rear signal onto the channels, so your essentially running mono rear rill







3) ok, heres where the l-r/r-l part comes in. lets use the rear left channel output for the example.. since were using the rear left output channel, double click on the rear right input signal thats on its input path. that will pull up this menu. in this menu, click invert polarity. hit ok. do the same thing for the rear right channel, but invert the left input signal. this gives you your l-r/r-l







This is what it should look like when done.








you can also adjust the amount of center cancellation by adjusting the percentages. just double click again and adjust..






This is just how to set up the L-R/R-L rear fill. this isnt the end of properly implementing it. that part, i am still researching. If you would like to share any info on that part, please do.
 

·
Registered
Joined
·
17,677 Posts
Discussion Starter #3
Erin also told me there is a good amount of info on rear fill in our former member werewolf's old posts. i still need to dig them up
 

·
Registered
Joined
·
950 Posts
OK...here is one of them from diyma--

Werewolf, ErinH and Gary Summers are all posting in it at some point, so it is a worthwhile, though long read!!

http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/22523-hey-werewolf-confusion-about-l-r.html
post # 4 ....

"we covered this. your balenced signal already contains the inverse signal. A balenced transmission consists of an L+ and an L- signal. likewise R+ and R-.

On the recieving end, the device subtracts the two, giving you L+ - L- = 2L. Any noise that was induced into the cable will be done equally to both legs and is also subtracted: N+ - N+ = 0.

cool!

So to achieve the L-R signal, simply take whatever device recieves the Balenced transmission and converts it to standard. Rather than the standard method of wiring, Wire L+ to the L+ input, but Wire R+ where L- would go. When the signals are internall subtracted, you end up with L+ - R+ = L-R

cake"



:confused::eek::confused:
 

·
Registered
Joined
·
1,111 Posts
Nick, from what I understand about the "new" software updates, the delay has been increased to as much as double. It could be as much as 25 to 30 ms.

This was implemented for those who are wanting to use rear fill.
 

·
Registered
Joined
·
580 Posts
Good info. thanks. I was almost there with you until you flipped the polls on each L,R/R,L. I'll have to try that.

Question.... of course I add delay but I don't touch the EQ for the rears and leave them flat. I've always seen it as just fill and only EQ the fronts. How much time do you spend EQ'ing the rears?
 

·
Registered
Joined
·
17,677 Posts
Discussion Starter #12
Good info. thanks. I was almost there with you until you flipped the polls on each L,R/R,L. I'll have to try that.

Question.... of course I add delay but I don't touch the EQ for the rears and leave them flat. I've always seen it as just fill and only EQ the fronts. How much time do you spend EQ'ing the rears?
I see no reason to not eq them

Sent from my SM-G920V using Tapatalk
 

·
Premium Member
Joined
·
1,148 Posts
Good info. thanks. I was almost there with you until you flipped the polls on each L,R/R,L. I'll have to try that.

Question.... of course I add delay but I don't touch the EQ for the rears and leave them flat. I've always seen it as just fill and only EQ the fronts. How much time do you spend EQ'ing the rears?
Are you band passing the rears? They should really only be playing from ~300-400hz up to ~4,000-7,000. Yes you can eq them. You don't have to spend a ton of time getting them perfect but just eq them to match the curve you are using for your fronts.

If you have the ability, you should level match and eq the rears just like you would the fronts.
 

·
Registered
Joined
·
580 Posts
Are you band passing the rears? They should really only be playing from ~300-400hz up to ~4,000-7,000. Yes you can eq them. You don't have to spend a ton of time getting them perfect but just eq them to match the curve you are using for your fronts.

If you have the ability, you should level match and eq the rears just like you would the fronts.
I do have them band passed. 150hz to 5000hz. They are just cheap $100 sony's I picked up at bestbuy I think +15 years ago. I reused them on this car as rear fill because that actually sound quite nice for cheap coax's. I picked up some nicer coax's but returned them because these Sony's sounded better at 1/3 the price. One of those diamonds in the rough.
 

·
Premium Member
Joined
·
1,148 Posts
Yeah, personally I don't think you have to spend a bunch of money on rears. You should really only be able to even notice that they are on when you are turning your head. I had a pair of Alpine SPR coaxials already so I just utilized those.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
350 Posts
Subbed, thanks!
 

·
Registered
Joined
·
3,361 Posts
At one point or another I've used the following speakers for this type of rear fill in different installs just because that's what I had on-hand and all have worked really well:

Pioneer TS-A878 Coaxial (surprisingly amazing for $40!)
Fountek FR-88
Eton 3-400/A8/25 MG
SB Satori MW13P-4
Pioneer TS-C520PRS

I suppose that these would be perfect for this as well, but are probably overkill:

Audiofrog GS-42 and the Illusion Audio Carbon C4CX/C3CX.

You'll need to play around with the mix percentage, level, and delay depending on your install and speaker locations.

Just curious...I've never heard it, but is Mark Eldridge using this technique in the NASCAR?

And Greg, it's great to hear that the new software for the Helix DSPs will allow longer delay times. :) w00t
 

·
Registered
Joined
·
515 Posts
Used this on my son's install this afternoon. Ended up with 19-21 ms delay and fairly significant attentuation (don't remember off the top of my head, but I think 7-9 db.

When listening to music you don't hear the rear speakers, even when turning your head. But if you turn them off, you notice a change in presence. My son plays saxaphone in jazz band and concert band. I didn't tell him what I did with the rear speakers. I just asked him if he could hear the difference between having the rears on and off without telling him I was cycling the rears on and off. All he said was "it sounds bigger".

I would say that there are some imaging cues that change slightly on information that is panned fair left or far right. Since the rear door coaxials are low, those far left and far right panned sounds probably drop just a bit relative to the rest of the soundstage. In my opinion, it is worth it for the extra presence that you sense. Would I use this for a SQ competition? Probably not. But for pleasurable listening? Absolutely!
 
1 - 20 of 69 Posts
Top