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Old 7th July 2008, 18:21   #1
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Default Subwoofer without Amplifier works..

Hi Gurujis,

I had experimented with the following setup.

HU - Pio 7950
Fr Speakers - GTO 937 [JBL]
Rear bridged and connected to a Pio 12" sub i picked from Nitrous

In Hu settings, I have turned the rear speakers to S/W, but the sub works in both situations. I understand that that is only for controlling the frequencies. Aux1, Aux2 turned off, dimmer, scroll, etc all turned off to conserve power


The whole setup is powered by a 15A eliminator and works pretty fine. The Sub actually works and produces enough "Thump".

Now, when I pump up the volume, there is clipping of the track as the current seems not enough for powering the Speakers and SUb.

Am i right in my assumption?

Also, If I manage to get a 100A eliminator or some capacitor banking inbetween the power and the HU setup, Do you think the volume can be pumped up as well ?

What is your opinion? Anybody done anything like this?

Thanks for your inputs.

Cheers
Vikram
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Old 7th July 2008, 18:43   #2
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you will be frying up your HU's IC's very soon matey better get a 2channel amp if possible.It will be cheaper than repairing your HU or getting a new one

EDIT:are you using the setup in your home

Last edited by ramie2400 : 7th July 2008 at 18:45.
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Old 7th July 2008, 18:52   #3
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Quote:
Originally Posted by ramie2400 View Post
you will be frying up your HU's IC's very soon matey better get a 2channel amp if possible.It will be cheaper than repairing your HU or getting a new one

EDIT:are you using the setup in your home
I dont understand how i could fry my HU IC? What is the max current rating of the IC. If I could tweak the settings, can enjoy the HU with Sub.

Yes I am using the setup at home.
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Old 7th July 2008, 18:52   #4
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If you have a 15 amp eliminator then add a motorcycle 12 volt battery. You will be fine after that.
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Old 7th July 2008, 18:52   #5
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its a LOOOOONG story, but bottom line , DONT. Will post why not from the electronics POV. suffice to say ,if you try to bridge bridged amps , you will end up shorting stuff . its because the HU has built in protection, else it would have blown up long ago...
if you want to drive a sub with the HU, get a DVC sub

If you really want to understand why not ,
HEAD UNIT SPEAKER OUTPUT-BRIDGED?
an explaination of the amp configuration in a car HU.If you can fully understand it , we can talk more :P

I got an amp made locally to drive my sub
http://www.techenclave.com/show-off/...tml#post766915

Last edited by greenhorn : 7th July 2008 at 19:10.
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Old 7th July 2008, 18:56   #6
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Quote:
Originally Posted by low_bass_makker View Post
If you have a 15 amp eliminator then add a motorcycle 12 volt battery. You will be fine after that.
Guruji, How do i add the motorcycle battery. Series or parallel with the HU and Why -

Quote:
Originally Posted by greenhorn View Post
the amp in the HU is already bridged. DO NOT bridge it again. you WILL end up shorting it. if you want to drive a sub off an HU, get a DVC sub and run each coil off each channel
Sir, this is completly OHT. What I did was join the -ve, -ve and +ve, +ve of the Rear speakers off the HU and joined it to the -ve and +ve respectively of the Sub. I have not shorted anything AFAIK.
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Old 7th July 2008, 19:08   #7
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Quote:
Originally Posted by headers View Post
Sir, this is completly OHT. What I did was join the -ve, -ve and +ve, +ve of the Rear speakers off the HU and joined it to the -ve and +ve respectively of the Sub. I have not shorted anything AFAIK.
AFAIK, your head unit will be fried pretty soon
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Old 7th July 2008, 19:09   #8
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Quote:
Originally Posted by headers View Post
Guruji, How do i add the motorcycle battery. Series or parallel with the HU and Why -
No Guru Ji here but you will be connecting it in parallel, directly to the power terminals of the HU.

If you have a Battery charger in place of the eliminator then your battery life will be more because the eliminator will keep on charging the battery but the charger will keep switching off-on according to the use.
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Old 7th July 2008, 19:14   #9
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Quote:
Originally Posted by headers View Post
Sir, this is completly OHT. What I did was join the -ve, -ve and +ve, +ve of the Rear speakers off the HU and joined it to the -ve and +ve respectively of the Sub. I have not shorted anything AFAIK.
Quote:
Originally Posted by Sam Kapasi View Post
AFAIK, your head unit will be fried pretty soon

Totally agree. You will fry. And it will SMOKE ON HU.

To wire a sub try connecting it with only one channel of the rear speakers.
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Old 7th July 2008, 19:33   #10
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let me try to explain. in a 2 channel amp, the outputs are shown as +, - , +, -

say at a particular instant , the output is 1V. if you measure the voltages , they will be +1 V, 0V, 0V, -1V. when you set the amp to bridged mode, the two 0V terminals are shorted together , and the speaker is connected to the +1 V and -1V terminals , so you get 2V total.

amplifier which have one output at 0V are referred to as Single ended output amps. one terminal has constant ( 0 ) voltage , while the other varies. this is what a single channel of a 2 or 4 channel amp looks like . because you have two terminals which are at the same voltage, they can be shorted together.

in a car HU, the outputs are already bridged to get the maximum output from the 12V supply voltage limitation (amps dont have this limitation, since they have SMPS circuits which boost the voltage ) , are at +1 and -1.

if you short the +'s together, and connect the speakers to the -'s nothing much will happen, If you connect the + and - together, you'll short those two halves of the bridged amp(which will end up damaging them, since they are at +1 and -1V ) , while the other 2 halves will drive your speaker. Still your output will be between the +1 and -1V terminals , so you'll get only 2V , which is the same as using one channel of the HU.

Hope I didnt confuse you

Try connecting the sub to just one channel. It SHOULD still sound the same , but without the clipping

Last edited by greenhorn : 7th July 2008 at 19:42.
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Old 7th July 2008, 19:40   #11
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Dude the Standard HU ICs are never designed to handle such loads , so its just a matter of time and luck before the HU Ics are fried !

The max current rating of your ICs can never be more than a quarter of the rating on your HU Fuse. Thats a very very ball park figure , for details refer your manual !

On second though my logic might be wrong too i think that the gurus advice swould be a better bet !

Last edited by hellstar : 7th July 2008 at 19:44. Reason: second thoughts...
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Old 7th July 2008, 19:57   #12
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Quote:
Originally Posted by greenhorn View Post
Hope I didnt confuse you
Oh. Sure, you did confuse me.

Is a glossary of the terms available anywhere? I will be grateful if somebody posts a glossary of terms somewhere. In particular, terms like corssovers, difference between 1, and 2 channel amps, ported subs (or was it "portable" as in "removeable" subs - have seen the term "ported" used too much w.r.t. sub). I should confess that I had to guess that "subs" meant sub woofers, and not submarines.

When I just joined this forum, I did not know about co-axials and components (not even that such things existed).


Quote:
amplifier which have one output at 0V are referred to as Single ended output amps. one terminal has constant ( 0 ) voltage , while the other varies. this is what a single channel of a 2 or 4 channel amp looks like . because you have two terminals which are at the same voltage, they can be shorted together.
Does this mean that there could be 2 channel amps with three terminals - one each for left / right outputs and one 0 V?

I guess that a list of possible products AND features to look out while shopping for car audio components too is in order.

Not too long back, I used to wonder why people were using amps in addition to the HU output. And after seeing some posts, I see features like "X ready" and "Y ready" especially w.r.t. to HUs.

Last edited by BaCkSeAtDrIVeR : 7th July 2008 at 20:05.
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Old 7th July 2008, 20:10   #13
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Quote:
Originally Posted by low_bass_makker View Post
No Guru Ji here but you will be connecting it in parallel, directly to the power terminals of the HU.

If you have a Battery charger in place of the eliminator then your battery life will be more because the eliminator will keep on charging the battery but the charger will keep switching off-on according to the use.
Yes I have a battery charger too! Parallel connection will give more current. AFAIK

Quote:
Originally Posted by Sam Kapasi View Post
AFAIK, your head unit will be fried pretty soon
Why Sir?

Quote:
Originally Posted by low_bass_makker View Post
Totally agree. You will fry. And it will SMOKE ON HU.

To wire a sub try connecting it with only one channel of the rear speakers.
Ok..will connect only 1 rear speaker and try results!
Quote:
Originally Posted by greenhorn View Post
let me try to explain. in a 2 channel amp, the outputs are shown as +, - , +, -

say at a particular instant , the output is 1V. if you measure the voltages , they will be +1 V, 0V, 0V, -1V. when you set the amp to bridged mode, the two 0V terminals are shorted together , and the speaker is connected to the +1 V and -1V terminals , so you get 2V total.

amplifier which have one output at 0V are referred to as Single ended output amps. one terminal has constant ( 0 ) voltage , while the other varies. this is what a single channel of a 2 or 4 channel amp looks like . because you have two terminals which are at the same voltage, they can be shorted together.

in a car HU, the outputs are already bridged to get the maximum output from the 12V supply voltage limitation (amps dont have this limitation, since they have SMPS circuits which boost the voltage ) , are at +1 and -1.

if you short the +'s together, and connect the speakers to the -'s nothing much will happen, If you connect the + and - together, you'll short those two halves of the bridged amp(which will end up damaging them, since they are at +1 and -1V ) , while the other 2 halves will drive your speaker. Still your output will be between the +1 and -1V terminals , so you'll get only 2V , which is the same as using one channel of the HU.

Hope I didnt confuse you

Try connecting the sub to just one channel. It SHOULD still sound the same , but without the clipping

Ok Sir, will do..thanks for the details..i will have to understand it better!
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Old 7th July 2008, 20:21   #14
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OK I have disconnected one rear terminal from the Sub. Now only one rear channel is driving the sub.

The sound seems slightly improved..or maybe I'm getting old! Yeah able to goto Higher volume levels

Anything wrong, will i still fry the HU?
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Old 7th July 2008, 20:30   #15
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IIRC, you could Low pass the output of the rears in the 7950. that should improve the bass further
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