[wooka]

Team,

I have a weak head unit. Android, chinese.
I am using the RCA to drive two speakers at the back and a sub-woofer.

Question:
Can I utilize the (hopelessly underpowered) HU's 4 speaker outputs to power two speakers on the doors? The idea is to mix the front and the rear for 2x power.
Car: Thar
Speakers: Undecided
Current config : 4 channel -> Sony 4 channel amp - 1-L oval, 2-R oval, 3+4 - sub
Expected config : HU put to use : Front + rear left line level -> one left speaker. Similar for the right speaker.

P.S. - Any hope for better FM reception? I have installed a new Mahindra digital antenna (XYLO OEM) - no dice.

I'm an engineer who'll make the mods once instructed! But low electrical IQ.

For the mods:
I have hunted and failed to find a thread that answers my question.
Kindly merge if suitable.

[viXit]

Lot of the times, the gurus on the "ask the gurus" thread suggested something sumilar.

Suggested setup,

4 RCA OUTS used as follows

1. ch1- Left front through sony amp
2. ch2- right front through sony amp
3. ch3 subwoofer through sony amp
4. ch4 subwoofer through sony amp

Your head unit should have a minimum of 4 high level outputs. Bridging them together for 2 more speakers is possible. Just find the positives and negatives and bridge them together. Both +ves together and both -ves together attached to the +ve and -ve of the speaker respectively. Do this for each side.

That's totally doable.

[graaja]

Originally Posted by wooka

Expected config : HU put to use : Front + rear left line level -> one left speaker. Similar for the right speaker.

Shorting the amplifier output directly is a bad idea. Even though the driven signals may be the same (Front left + rear left, or front right + rear right), any change in amplitude levels in the output of the amplifiers can load one of the channels and may blow the drivers. The right method would be to use an external amplifier.

[wooka]

Originally Posted by viXit

Lot of the times, the gurus on the "ask the gurus" thread suggested something sumilar.
--------------------------

Your head unit should have a minimum of 4 high level outputs. Bridging them together for 2 more speakers is possible. Just find the positives and negatives and bridge them together. Both +ves together and both -ves together attached to the +ve and -ve of the speaker respectively. Do this for each side.

That's totally doable.

But the immediate response after yours recommends avoiding it.
Cheaper units must use a single source of 'clock' - thereby why would there be a phase difference in the signals across two outputs? Sorry, as I said, electrical noob.

[Comrade]

Not that I completely understand why, but You should never split or mix high level signals. One output should be matched to one input with correct impedance, voltage, wattage etc. Instead Recommended way is to split low level (preout) output into multiple amps.

You can use your existing amp to power 4 speakers and use a new mono amp to power sub. You can use a rca y-cable (or sometimes 4 channel amp has inbuilt sub rca out) to split one of your 4 rca channels to mono amp.

[viXit]

Car audio installers have been bridging channels and splitting channels since time immemorial.

My car has 4 channels of amplification but I have 4 speakers and a sub.
I went to my installer fully prepared to have only front speakers and a sub, but the installer insisted to have rear fill also on the same front channels.

That was my old configuration before upgrading to my new amp, and I didn't want to do it, but the rear fill surrounding you feels really nice. SO I gave in to the temptation.
option 1
What I'm talking about is using 1 channel for 2 speakers. But your situation is where you want to use two channels for one speaker. A.K.A bridging. That's how your subwoofer is running. So I don't see anything wrong with that.
--------------------------------
option 2
Why don't you ditch the rear speakers, I don't think Thars have a lot of rear seat passengers. I assume you don't want to do this because of the better oval speakers in the back.
---------------------------------
option 3

The most expensive and the most right way to do it,

Buy a Y splitter, which makes one RCA output into two, so that you can run more RCAs to your amp, but with more RCA outs you will need more amplification channels, basically you have to buy another amplifier, maybe a monoblock, a distribution block, additional wiring etc. expenses can go upto 10K. But you lose fader controls. Only balance would work

[navin]

Originally Posted by wooka

I am using the RCA to drive two speakers at the back and a sub-woofer.
Question:
Can I utilize the (hopelessly underpowered) HU's 4 speaker outputs to power two speakers on the doors? The idea is to mix the front and the rear for 2x power.
Car: Thar
Speakers: Undecided
Current config : 4 channel -> Sony 4 channel amp - 1-L oval, 2-R oval, 3+4 - sub
Expected config : HU put to use : Front + rear left line level -> one left speaker. Similar for the right speaker.

You cannot use Line Level to drive a speaker directly. You need to use Speaker level only.

Ok this is what I understand you want to do.

HU Front Line Level -> 4 channel Sony Amp -> 2 channels bridged for the subwoofer, 2 channels driving Rear speakers.

HU Front + Rear Speaker Level -> bridge both to drive Front speakers.

You can do this with two caveats:

1. The internal amp of your HU should be able to handle the 4ohm load aka if you bridge the HU's amp each channel of the HU's amp will only see 2ohms. This can be a challenge as cheap HU amps are not designed for 2 ohm loads.
   
2. How are you going to send the 2 (left and right) Front line-level signals to all 4 channels of your HU's amp? This will require some exceptional surgery of your HU.

Think. The HU has an internal 4 channel PRE amp and an internal 4 channel POWER amp. Each channel of the PRE amp is connected directly to the corresponding channel of the POWER amp.

Now when you bridge an amp both channels of the amp must be getting the same signal except one channel is inverted.


In your HU the left front channel of the preamp is feeding the left front channel of the power amp AND the left rear channel of the preamp is feeding the left read channel of the power amp.

If you bridge the front and rear channels of the left POWER amp they will NOT be getting the same signal. Instead hey will be getting different signals from their corresponding preamps.

You will have to disconnect the Left Rear Preamp from the Left Rear Power amp and connect the Left Front Preamp to the Left Rear Power amp (phase inverted). This way the Left Rear Power amp and the Left Front Power amp will get the same signal from the Left Front Preamp.

Hope this helps.

[Kosfactor]

Why not add another amp to drive the subwoofer? they are inexpensive and makes everything that much more easier than all this headache of bridging etc.

[wooka]

Makes sense. I'll see if I can get another 2 channel for the front (will use line level inputs if required at that point) a Sony 502 or something similar (D class) as and when I feel i need it.

My current setup is 2x2 pioneer ovals. I don't like it. They're massive. I look like a band wala.

I wish to move to infinity reference 100W ovals, one on each side. I recently acquired them at a good price. However I feel they won't lend quality 'fill' to the cabin. Thus, the need for front 6.5s. I am unsure where to put them (spacer plus door or custom door lining and panel from bimbra) due to the associated vibration and lack of breathability.

Questions:
1. Where do I place the ovals (one on each side?)
2. What size box should I make for the ovals? Consider poor ply / mdf.. I have rationalized 9*12*7 inches.
3. Port the box?
4. 6.5s on the door with spacers? What height? Or the custom side door panels bimbra sells? It's a job to go to Gurgaon for these and swat flies for a couple of hours. And I wonder if they'll rattle too.
5. 6.5s on the roof? I'm getting ideas... Perhaps position them up top in the corners. Then they won't need amping cause they're so 'forward'. And I suppose I can manage without components. I can fab the boxes, pad with nitrile sheet, and PU foam glue them. How do you think PU foam holds up strength wise (an amped speaker box) ?
6. I've got the Sony 1004. Wires all over the place. How do I organize this contraption? Any suggestions? Since the car lets a little water in around the windshield, I can't place it under the seat. Or maybe I can... Do you reckon the tool box area will breathe enough for the amp?

Meanwhile, Navin has made me see the light of reason with skipping the chinese HU bridging. I get basic electronics so, I will go with his take on this.

[navin]

Originally Posted by wooka

a Sony 502 or something similar (D class) as and when I feel i need it.

My current setup is 2x2 pioneer ovals. I don't like it. They're massive. I look like a band wala..

The Sony 502 is a Class AB amp, not Class D.

2" x 2" Pioneer ovals? I am confused. Can you please clarify.

[Kosfactor]

If you already have 4 speakers with you, may as well fit them in the space available rather than buying new ones. Ideally a smaller speaker \ component system on the front door and ovals in the rear would be fine along with a subwoofer.

I have seen custom box mounted on the front doors with 6.5 speakers as well as another set of boxes with ovals in the rear + subwoofer but the seating set up was 2+2.

Do post some pictures once you get going. I have been driving without a stereo for many years simply to avoid the headache of finding a place for it and it not getting stolen (soft top).

[wooka]

Originally Posted by navin

The Sony 502 is a Class AB amp, not Class D.

2" x 2" Pioneer ovals? I am confused. Can you please clarify.

My mistake!
I have two long boxes at the back.
They house two ovals each.

They're currently wired in parallel (2 parallel connections per box) - El cheapo pioneer
- see attached.

50 W RMS and 5 years old (surrounds are not rubber)... Should I change them? Not too happy. I have one pair of infinity reference 6*9. I can either get another pair and keep them at the back, or swap the long boxes to single oval boxes.

I've got someone selling a used Sony woofer and an N502 cheap... So that's also on the table, and it frees up the amp to drive four speakers across the car with ease, and the sub-woofer separately.

Thanks everyone for your responses.
I'll keep people posted as this develops. Just know I'm now considering simplifying.. 2 ovals at the back, total, with 2 ovals/ 6.5s mounted to the top of the front of the cabin somewhere. If I keep the ovals just behind the front seats, I have some room to either side before I hit the wheel well.

[navin]

Originally Posted by Kosfactor

I have been driving without a stereo for many years simply to avoid the headache of finding a place for it and it not getting stolen (soft top).

When I had a soft top I had a head unit with a detachable faceplate. All I needed were was 2 speakers because they were right behind the driver and passenger.

Originally Posted by wooka

I'll keep people posted as this develops. Just know I'm now considering simplifying.. 2 ovals at the back, total, with 2 ovals/ 6.5s mounted to the top of the front of the cabin somewhere. If I keep the ovals just behind the front seats, I have some room to either side before I hit the wheel well.

I cannot help you with speaker locations as I am unfamiliar with the Thar.

2 Ovals in the rear, a pair of 6" coax in the front, a subwoofer hidden someplace in the rear and amplifiers to drive them all should work nicely.

[Kosfactor]

Originally Posted by navin

When I had a soft top I had a head unit with a detachable faceplate. All I needed were was 2 speakers because they were right behind the driver and passenger.

I`m going to take the plunge and put something in perhaps next month. Need something that would sit under the dash - Just a knob, a small box that works on bluetooth, 2 coaxial speakers and I will call it a day. I searched for some amps like that but was not sure if they will induce some noise \ whine in the system as they all were non name brands. So the occassional woosh from the turbo is all that I can enjoy.

Do you think an old cassette player with Aux would work just as well?

[navin]

Originally Posted by Kosfactor

Do you think an old cassette player with Aux would work just as well?

No one will steal a cassette player. They won't even know what it is. Give the kids a cassette and a pencil and watch them wonder how they are related.



Do you have any cassettes and a tape deck? Just record a mix on cassette and you are home. Or use a Cassette Aux in like shown below. Does your phone have a headphone jack?



Your other option is to get some media player that takes an SD card or better still enjoy the music of the turbo.