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Discussion Starter · #1 ·
I have an alpine PXE-H660 which I believe has analog RCA outputs for 7 channels, 2 are for right and left rear channel output.

This is connected to a pair of JL XD400/4 amps which have balanced RCA inputs.

Is there any reason I can't build a cable that uses the L+ and R+ (center connectors) from the H660 and use them as left minus right balanced inputs for rear fill on one of the JL amps?

Right + goes to center pin on right channel amp input.
Left + goes to outside on right channel amp input.

Left + goes to center pin on left channel amp input.
Right + goes to outside on left channel amp input.

This way I should get L-R on the left channel and R-L on the Right channels to cancel out the shared signal between L&R for ambient rear fill only.

Does this make sense or am I about to blow something up?
 

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Quote:
Originally Posted by hilander999
I think we just hijacked someone else's thread...

How you accomplish this is greatly dependant on your system configuration.
Post what gear you are using in the thread I started for my rca cable and I will try to point you in the right direction.

There are some great threads here on ambient rear fill or L-R Rear Fill with a lot of great information from werewolf and others (I forget who) which is where I found most of the information I needed, but its burried in hundreds of contradicting pages, so it's not that easy to find the relevent posts.

THANK YOU! my setup is as follows:

Pioneer HU AVH-4200DVD

Frt Rear, and SUB RCAs to AC Matrix inline driver

frnt RCAs split runnig front mid basses via bridged JL 300/4 (150W RMS per driver) and front mids and tweeter via second JL 300/4 (75W RMS per set)

rear RCAs to rear channels on second JL 300/4 (75W RMS per components in rear doors)

sub RCAs to JL 750HD

thats pretty much it, i guess its a psuedo active setup

CC
 

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Discussion Starter · #5 ·
THANK YOU! my setup is as follows:

Pioneer HU AVH-4200DVD

Frt Rear, and SUB RCAs to AC Matrix inline driver

frnt RCAs split runnig front mid basses via bridged JL 300/4 (150W RMS per driver) and front mids and tweeter via second JL 300/4 (75W RMS per set)

rear RCAs to rear channels on second JL 300/4 (75W RMS per components in rear doors)

sub RCAs to JL 750HD

thats pretty much it, i guess its a psuedo active setup

CC
Which JL amp series is this? (exact model please)To use the RCA method your amp must have balanced rca inputs.

How much time alignment does your HU have for the rear channel?

I don't know how well this is going to work with rear speakers mounted in the doors, but you can certainly give it a shot and post your results. Mine are mounted in the rear deck, aimed at the glass so the sound waves get combined and canceled at that point, before spreading around the cabin.
 

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Discussion Starter · #7 ·
i have two JL Slash 300/4 V2 and one JL 750HD.
unfortunately my HU has no T/A :(

i have been looking around into getting a DSP

CC
Ambient rear fill needs delay around the 20MS mark depending on how large your car is and where the speakers are located.

I have a large car and the speakers are as far back as they will go, so the 10MS delay in my PXE-H660 is just about perfect for my needs.

I feel that with a car that small your going to need a bit more then I did and your speaker locations are muck closer to your listening position does not help.

OK, that amp does have ballanced rca inputs so you can easily built the same cable I did to get the ambient rear fill working, but I don't know how good it will sound with no delay.

You may want to look into the MINIDSP and Center/Rear channel plugin.
MiniDSP 2x4 RevB | miniDSP
http://www.minidsp.com/images/documents/Product Brief-Rear-Center channel plug-in.pdf

I am also very pleased with the staging I was able to get with the Alpine PXE-H660 which sells for around $240 and which uses a mic to calibrate the system for you.

You can build the cable for about $5 at radio shack and see how it sounds.
You can get a minidsp+plugin to handle the rear channels ($135 + shipping)
Or you can add full autotune/ta/pe to your existing system with the H660 ($240)

This custom rca cable was my last resort before purchasing a minidsp for myself, and I was lucky enough to find a method that worked perfectly in my car.

You have to decide where to go from here.
 

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Discussion Starter · #11 ·
Doesn't look like PPI has the manuals up for those yet.
I could not find it either and without the manual, it's all guesswork.

There are a few different tricks to make this work depending on system design, but all methods really do need some time delay to get the right results.
My IMPALA is pretty large so the 10MS delay that my PXE-H660 allowed was fine, smaller cars with rear channel speakers in the rear doors will need up to 27MS of delay to get the proper effect.

IMPORTANT!
I sorted through hundreds of posts to get this information, and while I am fairly certain these wiring tricks will work, there is no way for me to test them all and make sure that they will not harm your equipment.

USE AT YOUR OWN RISK!
I advise to everyone to do their homework and make sure they know what they are doing before trying any of this. I will not be held responsible for anyone's equipment that gets smoked by doing anything I have suggested.

Yes, disclaimers are very important. :)
Method one: AMP with balanced differential RCA INPUTS
Build the custom RCA cable outlined in the first post.

We are only using the left and right positive feeds for this method.
(SOURCE)Right + goes to center pin on right channel RCA connector to amp.
(SOURCE)Left + goes to outer shield on right channel RCA connector to amp.

(SOURCE)Left + goes to center pin on left channel RCA connector to amp.
(SOURCE)Right + goes to outer shield on left channel RCA connector to amp.

Wire speakers normally.
Set source time alignment between 10MS and 27MS
Smaller cars will require a longer delay than larger cars.
Both left and right T/A must be the same value.
Method 2: AMP with a switch to bridge channels
Leave the switch in the NON-Bridged position
Use standard RCA cables for source.
Wire speakers to amp as normal.
Now take both negative speaker wires at the amp and connect them together with a wire nut. You only have the two positive speaker wires connected to the amp.

For best effect, take the right speaker wires and reverse the polarity.
You can do this at the amp or speaker side, which ever is easier.

Set source time alignment between 10MS and 27MS
Smaller cars will require a longer delay than larger cars.
Both left and right T/A must be the same value.
Method 3: Bridgeable amp with NO SWITCH to bridge channels.
Amps without a switch to bridge channels automatically swap the polarity on one channel to produce a mono signal.

For this to work you must build an RCA cable the swaps the polarity on the right channel amp input only. Left side of RCA is wired normally.

(SOURCE)Right - goes to center pin on right channel RCA connector to amp.
(SOURCE)Right + goes to outer shield on right channel RCA connector to amp.

(SOURCE)Left + goes to center pin on left channel RCA connector to amp.
(SOURCE)Left - goes to outer shield on left channel RCA connector to amp.

Wire both positive speaker wire to your amp as a bridged channel and connect the 2 negative speaker leads together with a wire nut.

Set source time alignment between 10MS and 27MS
Smaller cars will require a longer delay than larger cars.
Both left and right T/A must be the same value.
Method 4: Direct from rear channel of HU, NO AMP PRESENT.
This method only works for head units that do not bridge channels.

Simply remove the negative speaker wires from both rear speakers and run a jumper wire between the 2 negative speaker terminals connecting them together. Be certain to tape up the unused negative HU speaker wires so nothing shorts to ground.

This is for "No-Frills" head units, not expensive components that you are afraid to blow up. Doing this will change the speaker impedance and could overload your HU's internal amp. However all of these tricks remove most bass tones and that is where the majority of the power is used in a normal stereo rear channel.

Do not try this on a thousand dollar head unit unless you have a fantastic warranty.
If you find any mistakes in the above post, please let me know so I can correct it.
This information all came from this forum and is not my work alone, it's just nice to have it all together for people who may like to try it.

Method 1 worked out perfect for my system. Choose your wiring trick by system design and please post your results.
 

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I honestly would of, but my head unit does not have time delay.
I'm just curious, I've always thought that for a speaker to work, both positive and negative terminals had to be connected. What is the theory behind connecting only the positive wires to the amp? I imagine it has something to do with the negatives being connected together
 

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Discussion Starter · #14 ·
I honestly would of, but my head unit does not have time delay.
I'm just curious, I've always thought that for a speaker to work, both positive and negative terminals had to be connected. What is the theory behind connecting only the positive wires to the amp? I imagine it has something to do with the negatives being connected together
Both the positive and negative terminals of each speaker are connected, just not in the normal way. Audio signals are A/C so there is signal at both positive and negative terminals. Thats as simple as I can explain it.
 

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hilander,

I'd be very interested in getting some ambient rear-fill tips/techniques from you. i actually saw a post of yours about ambient rear fill in a thread a little while ago and so i searched ambient rear fill which led me to another post that you also posted in which led me here...:D. Whenever you get a chance to reply I'll post up my stuff. there's a slightly vague description of what i have in a thread i made recently as well.. but i'll give u a lot more detail of course. thanks

also after reading through your different methods that you posted above. i definitely think method 2 would work best for me.
 

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Discussion Starter · #17 ·
hilander,

I'd be very interested in getting some ambient rear-fill tips/techniques from you. i actually saw a post of yours about ambient rear fill in a thread a little while ago and so i searched ambient rear fill which led me to another post that you also posted in which led me here...:D. Whenever you get a chance to reply I'll post up my stuff. there's a slightly vague description of what i have in a thread i made recently as well.. but i'll give u a lot more detail of course. thanks

also after reading through your different methods that you posted above. i definitely think method 2 would work best for me.
If you have a specific question, ask it. :)
 

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If you have a specific question, ask it. :)
Actually after doing some tuning today and following your steps for rear fill I have achieved a sound I am very happy with and I have to say my system is sounding better than ever:) only thing Im not sure about is crossover settings for the rear fill. Set it by ear and it sounds good to me but I'm sure it can be better. I have rear set at 120/-24db I believe and fronts xover is 70/-24db

Just to clarify *ambient rear fill achieved*
 

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Discussion Starter · #19 ·
Actually after doing some tuning today and following your steps for rear fill I have achieved a sound I am very happy with and I have to say my system is sounding better than ever:) only thing Im not sure about is crossover settings for the rear fill. Set it by ear and it sounds good to me but I'm sure it can be better. I have rear set at 120/-24db I believe and fronts xover is 70/-24db

Just to clarify *ambient rear fill achieved*
Very cool.

If you can bandpass the rear stage, try 90hz to 2k.
I'm running some cadence midbass that roll off around 2k and they sound amazing in this particular setup.

I find that most low bass, but not all, is common to both channels and gets cancelled out. However, certain instruments from one side that are miked out of phase sound amazing. This is most common in orchrestra recordings and will make you smile every time you hear it.
 

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I have some questions for you. I have the kenwood excelon 997 HU with boston spz60 speakers. Now since these speakers come with passive crossovers that are set up in my car, do I just set the DSP on th HU to Bypass? Or do I set it to Through and just set the crossovers on the HU to Through and turn off crossovers on the amp? Right now I have it set to bypass and amp crossovers off. Sounds great. Am I missing out on ambient rear fill by having dsp set to bypass since I can't do Distance Time Alignment with it on bypass? Also I'm tryin to to get my sub adjusted correctly. I have the boston SPG 15" in the boston box here's a link SPG555PS | Subwoofers | Boston Acoustics US)
And my amp is the Kicker IX 1000.1
 
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