Want to add Rear Fill...but no more RCA outs...

[Why So Cereal? 5,000+ posts]

So, here is what my setup is looking like thus far...

Vehicle: 2010 Scion tC

Headunit: Pioneer P880PRS

Front Stage Mids: Peerless Exclusive HDS Nomex (Powered by Aura RPM2300)

Front Stage Tweeters: Diamond D6A (Powered by Memphis 16-ST100)

I would like to add rears, but since I'm running active fronts with sub, I am all out of RCA outs for a rear amp. So, I came up with an idea. My Aura amp pushing my front stage has RCA outs on it. I was thinking I could use those to get a signal to a separate amp for my rear speakers with a Mini DSP (Home | miniDSP ) between the 2 amps to handle my crossover points, slopes, and Delay.

Firstly, will this idea work, or am I missing something?

Also, given this idea will work, I plan to delay the signal using the miniDSP. I wont have a full range signal going into the rears since my HU is handling the crossover duties. But, I was wondering if it matters how low I allow the rear mids to play (within their limits of course)? Also, should they be in normal stereo, or mono?

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[zako 10+ year member]

I have a setup that's similar to yours. It seems like there are two ways around your rear fill problem. One is mini DSP. Another, get a JBL MS-8 or other processors that implements a proper rear fill.

One frequently recommended method of implementing rear fill is to send to it the difference L-R signal that's also time delayed about 20ms and attenuated. I believe I have seen a Logic7 paper that mentions that this is the "conventional" way of implementing the rear fill (Logic7 does more, it steers the out of phase signals to the rear, depending how out of phase the signal is). The miniDSP has a plug in that does exactly this. I would take your subwoofer RCA cable, and plug it into miniDSP (make sure on the stereo, it's a full range signal). On one set of miniDSP outs, you can have a low passed signal for the subwoofer amplifier. On the other set of outs, you can have time delayed, attenuated, L-R difference signal. The only problem with this approach is that your "subwoofer volume" control on the stereo now becomes "subwoofer+rear fill" volume control.

By the way, the explanation for the L-R difference signal that I have heard is that left channel will play ONLY things that are not present in the right channel and vice versa. Since human voices and other instruments are recorded in mono in order to center their imaging, those elements for the most part will not be played by the rear fill, leaving the rear fill for the most part playing "ambiance" information, and without interfering with the front stage. The time delay is to simulate the amount of time the front stage sound waves take to travel to the rear wall, and then reflect back at you.

My personal preference is to get a JBL MS-8 processor when I have the money for it as their implementation is a bit more sophisticated, and it can do other things as well. In the past my rear fill was simply time delayed and attenuated. I think it was decent, but I lost it after going active.

 

[Louisiana_CRX 5,000+ posts]

Y adapt off your mid outputs into an RCA fader....your rear fill wont need any highs...just mids...go from RCA fader to a small rear fill amp...something like my Harmon Kardon baby amp would be good...I also have some old school Proton SQ amps that would be perfect

 

[oldschool4me 10+ year member]

processors work fantastic for this. you could get by using a line out converter or use an amp that has high level inputs as an alternative from what dave said.

 

[mlstrass 5,000+ posts]

just remember that if you have a bandpass xover set up for the mids then that's all that amp will pass to the amp for the rear fill. Might be fine for what you plan to do...

 

[Why So Cereal? 5,000+ posts]

I have a setup that's similar to yours. It seems like there are two ways around your rear fill problem. One is mini DSP. Another, get a JBL MS-8 or other processors that implements a proper rear fill.
One frequently recommended method of implementing rear fill is to send to it the difference L-R signal that's also time delayed about 20ms and attenuated. I believe I have seen a Logic7 paper that mentions that this is the "conventional" way of implementing the rear fill (Logic7 does more, it steers the out of phase signals to the rear, depending how out of phase the signal is). The miniDSP has a plug in that does exactly this. I would take your subwoofer RCA cable, and plug it into miniDSP (make sure on the stereo, it's a full range signal). On one set of miniDSP outs, you can have a low passed signal for the subwoofer amplifier. On the other set of outs, you can have time delayed, attenuated, L-R difference signal. The only problem with this approach is that your "subwoofer volume" control on the stereo now becomes "subwoofer+rear fill" volume control.

By the way, the explanation for the L-R difference signal that I have heard is that left channel will play ONLY things that are not present in the right channel and vice versa. Since human voices and other instruments are recorded in mono in order to center their imaging, those elements for the most part will not be played by the rear fill, leaving the rear fill for the most part playing "ambiance" information, and without interfering with the front stage. The time delay is to simulate the amount of time the front stage sound waves take to travel to the rear wall, and then reflect back at you.

My personal preference is to get a JBL MS-8 processor when I have the money for it as their implementation is a bit more sophisticated, and it can do other things as well. In the past my rear fill was simply time delayed and attenuated. I think it was decent, but I lost it after going active.

That idea with the full range to the DSP and out to the sub and rears sounds like exactly what I may do.

Y adapt off your mid outputs into an RCA fader....your rear fill wont need any highs...just mids...go from RCA fader to a small rear fill amp...something like my Harmon Kardon baby amp would be good...I also have some old school Proton SQ amps that would be perfect

It wasn't so much finding a way to power them, I just needed a signal and to be able to process it. I do need to trade my 2 channel Memphis for a small 4 channel though so I don't have so many amps back there.

just remember that if you have a bandpass xover set up for the mids then that's all that amp will pass to the amp for the rear fill. Might be fine for what you plan to do...

Exactly, that was my main concern initially. Zako's idea with the DSP seems to be perfect to fix that provided I can get a full range signal to the DSP.

 

[maylar 10+ year member]

Is just running the rears off the HU speaker outputs not acceptable?

 

[Why So Cereal? 5,000+ posts]

Is just running the rears off the HU speaker outputs not acceptable?

Well the actual rear RCAs on the HU will be used for my mids, the fronts for my tweets.

 

[keep_hope_alive Premium Member]

i've tried doing this off the midrange output (already bandpassed and filtered for the front mids) and while it works, you get little benefit. a miniDSP is the correct solution if an 8 channel processor is not in your plans.

i will likely get a miniDSP as well (or build my own rear-fill processor)

 

[Why So Cereal? 5,000+ posts]

So it seems I was halfway there in my idea....

Gonna need the REV B version and the DC isolator from what I've read, possibly a line driver for my subs.

What frequencies do u guys think the rears should be limited to?

 

[Dirtrider4eva 10+ year member]

run HU power to rear fill to speakers with high sensitivity? im running 200 rms to my fronts per side, and then hu power to aura ns6 4 ohm, but they have a high sensitivity and keep up great.

 

[Why So Cereal? 5,000+ posts]

run HU power to rear fill to speakers with high sensitivity? im running 200 rms to my fronts per side, and then hu power to aura ns6 4 ohm, but they have a high sensitivity and keep up great.

Can't fully process it like that. Also not really after extra volume, looking to have a delayed rear signal that allows me to recreate backwall reflections and increase the "room size".

 

[oldschool4me 10+ year member]

i bet louisiana_crx has a processor for ya....i bought mine from him some time ago. gave me a great deal.

 

[Why So Cereal? 5,000+ posts]

i bet louisiana_crx has a processor for ya....i bought mine from him some time ago. gave me a great deal.

I don't know of any other processors able to do what I want outside of the minidsp and expensive JBL MS8 and bit one, etc

 

[oldschool4me 10+ year member]

there are some older ones that will. im using a jbl gtx47 from the 90s. bought it from him bnib.