Help with amp

90XR7Cougar5spd

Registered User
I have 2 12" JL audio subs and a 500 watt bridgeable american legacy amp. When i bridge the amp when ever i turn the stereo up to loud or when it hits to hard, the amp kicks off when the motor is running, when the motor is off, i can turn the stereo up as loud as a i want to and let it hit hard as it can and it wont kick the amp off. When i seris the speakers together, it dont kick the amp on at all. What do i need. I was told i need 1 amp for each speaker, and that i just need to put a cap on it. what is the deal????
 
The amp is cutting off because you probably have the speakers in parallel. If the amp is not 1 ohm stable then you will need to run it in stereo. There is no gain to be had by bridging the amp in series, the power delievered to the speaker will be the same.

Jeff
 
J57ltr said:
The amp is cutting off because you probably have the speakers in parallel. If the amp is not 1 ohm stable then you will need to run it in stereo. There is no gain to be had by bridging the amp in series, the power delievered to the speaker will be the same.

Jeff

Dude You wanna speak english for me i have no clue what you just said. And also my amp is 2 channel 2 ohm stereo stable.
 
You want me to speak english?

You have the amp bridged correct? And the speakers are wired in parallel correct?

If this is the case then the problem you are having is a common one. Since your speakers are 4ohm (they are aren't they?), this presents a problem to the amp. The reason is when bridged the amp "sees" 1/2 of what it is presented. In this case 1 ohm per side (2-4 ohm speakers in parallel is 2 ohms). This is the reason it's cutting out.

Reconnect the speakers in stereo one per channel. Bridging the amp and then running the speakers in series to make an 8 ohm load will produce the same amount of power.

Jeff
 
the JL speakers are the dual voice coils or single because if they are single and u bridge your amp it will be a one ohm load plus the amp u have is junk sorry to be so rude but that amp is crap u need rockford but no amp is stable at one ohm load but i would check the battery if the amp isn't getting enough juice to it it will eventually do a power surge in your car and screw stuff up i hope u have a inline fuse on your power wire because thats there not to protect your amp but there to protect your car from your amp
 
Yes i know the amp is jumk but its working so so for the time being. the subs are JL W-3 dual voice. Those are good subs arent they. i was told they we top of the line. i dont know much about stereos, amps, subs and such but i do know how to wire them up to work.
 
Maybe I can help,

Here is a diagram from JL Audio, I own a car audio shop so I can help you fix this.

What is happening is you are loading down resistance wise farther than it is capable of, and lower line amps have non regulated power supplies so when you start your vehicle the amp see`s extra voltage and increases power and cuts out (best way right now that I can explain it)
 

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crabmustang302 said:
Maybe I can help,

Here is a diagram from JL Audio, I own a car audio shop so I can help you fix this.

What is happening is you are loading down resistance wise farther than it is capable of, and lower line amps have non regulated power supplies so when you start your vehicle the amp see`s extra voltage and increases power and cuts out (best way right now that I can explain it)

Alright preciate it im fixing to go out and try this out. How good are my subs, ive been told that they were top of the line.
 
That still shows a briged configuration. Basically since your speakers are 2 ohm wire each speaker per that diagram, except run each speaker on a channel.

Basically you will have both + and both - on each speaker connected to make a 2 ohm load. Then you have 2-2ohm loads, one for each channel. Always include all the information when asking for help. It saves a lot of time. I have installed since 87' and more experience than most people because I also have a background in electronic engeering. This is simple ohms law stuff but most people don't really understand it. But I am not up to date on every products specs. Ohmms law still hasn't changed.

The reason your amp cut out is that you are reaching the current limit within the amp when the car is running. You are able to produce more current flow (not voltage) with the engine running because the alternator is charging. With the engine off you were not able to supply the same amount of current.

Think of Voltage as the pressure in a water hose and current as the amount of water actually flowing. You can have pressure (voltage) without flow (amps) but you cannot have flow without pressure.

How did you have the amp connected again? Were all the coils connected together in parallel, then you had it bridged? Or were you just using one coil per speaker?

There are many amps that are stable to 1 ohm. I am looking at 2 right now that are stable to 1/2 ohm. One is a Soundstream Referance 500SX and the other is a Orion 225 HCCA. The Soundstream is rated:

75 X 2 @ 4 ohms
150 X 2 @ 2 ohms
250 X 2 @ 1 ohm (limited by fuse rating*)
250 X 2 @ 1/2 ohm (As above)

Must also go to 2-30 amp fuses, They will still blow if the amp is pushed hard. I actually told the factory about this problem some years ago.

It's easy to figure out how much power an amp is able to put out. Multiply the fuse rating by (12V to 14V) this gives you Watts. Then divide by amp effiency (usually 55%-65% for class AB amps and 80%-90% for class D)

Orion:

25 X 2 @ 4 ohms
50 X 2 @ 2 ohms
100 X 2 @ 1 ohm
200 X 2 @ 1/2 ohm



Jeff
 
Either way you cut it your partially wrong (j57ltr).

In the diagram I included before, If you take a good look at it, even if they are dual 2 ohm voice coils, by putting each sub in series that makes them 4 ohm`s each, then paralell them and bridge you get a steady 2 ohm load at amp.

2 DVC drivers with Voice Coils in Series / Parallel
Connecting the two voice coils of each driver in series (+ to -) and the drivers themselves in parallel (+ to +, etc.) will result in the following impedances:
Dual-6 Ohm Subwoofers: load at amp 6 Ohms
Dual-4 Ohm Subwoofer: load at amp 4 Ohms
Dual-2 Ohm Subwoofer: load at amp 2 Ohms

This is based on the diagram I posted previously.

This is right from the JL website, and I have been building car stereo`s for a long time.

You`ll love your JL Subwoofers they are great man, and they are great quality

As long as your amp is 2 ohm stable in mono if you have dual 2 ohm voice coil subs, it`ll be great

Feel free to PM me with any questions and answers you need :D

Thanks
Garett
 
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No body said what the VC's impedance is. I can not tell you what needs to happen unless you tell me what you have. I am not going to look it up There are too many configurations to worry about/

Crab you stated a briged mono configuration by the drawing. This would cause the problem he already has. A 2 ohm mono load is too low. As I stated previously each side of the amp "sees" half of what it is presented.

So if you have a 6 ohm mono load you will have 3 ohms per side of the amp.

If you have a 4 ohm mono load each side of the amp will see 2 ohms.

If you have a 2 ohm mono load then the amp sees 1 ohm per channel. Which is way too low.


He has already stated previously that his amp is 2 ohm stable.


It doesn't matter whether the amp is in stereo or mono. As long as the amp has a 4 ohm load mono or 2 ohms stereo the amount of power delievered to the speaker will be the SAME. Prove me wrong so I can correct you. ;)

When amp manufactures rate amps it's in per channel power at a rated load. You will notice that the mono config. is always double at double the rated load.

I don't know how long you have installed but time doesn't really matter. I have met way too many installers that don't understand how an amp works, don't understand ohms law and have only seen the inside of an amp so they could put plexiglass on it. I have worked on amplifers since I was in highschool and I did get a degree in electronic engeering. I don't install for a living anymore because there isn't any real money in it.


Jeff
 
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You need to look at the digram a little closer.

If you have a subwoofer with dual 2 ohm voice coils for example:

If you series the 2 coils you end up with 4 ohms
If you parallel the 2 coils you end up with 1 ohm

If you series the 2 subs individually then parallel them together you end up with 2 ohms seen at the amp.

I don`t know where you got your degree but if you know ohms law and have any old books kicking around you better start back at the beginning ;)

The diagram I included and the last post I left with the ohms listed is for that diagram which is 2 subwoofers each in series and then paralleled to create a 2ohm load (if the subs have 2ohm dual voice coils)

I`m not on here to bicker because theres no point.

And as for proving you wrong....I just did :D
 
Since we don't know what the impedance is then there is no way of saying exactly how to connect them. There is more than one way to skin a cat.

Everything I stated is correct.

Power delievered to each speaker is the same whether it is 2 ohms stereo or 4 ohms mono. And it's easier for an amp to control a stereo load with seperate speakers than it is controlling a mono load with speakers in series (coils on the same speaker excluded).

Jeff
 
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Here is a post I had in the Audio forum in the members section.


Ok let’s say we have a amp that puts out 25W RMS @ 4 ohms per channel, and 50W @ 2 ohms.
Watts are found by multiplying Voltage (V or E) times current (A). With that said we can
determine the amount of voltage applied to the load 4 ohms. We end up with 10 V @ 2.5 amps,
you could also have 2.5V @ 10 amps but you would have to have a .25 ohm load, that is not the
case here. The amplifier has a output voltage that cannot be exceeded, if the amp is driven
beyond this level you have what is called clipping. Ok so let’s start figuring power into various
loads.

2- 8 ohm speakers, 2 channels 10V / 8 ohms = 1.25 amps, 1.25 X 10 = 12.5 W (X 2 for total
output)
2- 4 ohm speakers, 2 channels 10V / 4 ohms = 2.5 amps, 2.5 X 10= 25W (X 2 for total output)

2- 2 ohm speakers, 2 channels 10V / 2 ohms = 5 amps, 5 X 10 = 50W (X 2 for total output)

When you bridge an amp you double the voltage across the load, so now you have 20V.

1- 8ohm speaker bridged 20V / 8ohm = 2.5 amps, 2.5 amps X 20V = 50W

1- 4ohm speaker bridged 20V / 4ohm = 5 amps, 5 amps X 20V = 100W

1- 2ohm speaker bridged 20V / 2ohm = 10 amps, 10 amps X 20V = 200W

The reason that each channel of the amp “sees” half of what it is presented is because each side is
doing half the work.

Hooking up 2- 4 ohm dual voice coil speakers you should just parallel (+ to + and - to -) both
coils to achieve a 2 ohm load. Then run one speaker to one channel and the other speaker to the
other channel. A lot of you probably think that the 2-2 ohm loads should be run in series (+ to -,
the remaining two leads go to the amp) to achieve a 4 ohm load then bridge the amp but doing
this each speaker still gets the exact same power, the only difference is that the amp has less
control of the speakers, with two series wired speakers (it’s splitting hairs though).

4- 4 ohm loads series / parallel 4 ohm Bridged. 4-4 ohm loads then parallel each pair for 2-2 ohm
loads, then connected in series = 4 ohm load. 20V / 4 ohms = 5 amps, 20V X 5amps = 100 watts
total.

4- 4 ohm loads parallel 2 ohms Stereo. Parallel each to get 2-2 ohm loads, 10V / 2 = 5amps, 10V
X 5 amps = 50 watts X 2 channels = 100 Watts total


2-8 ohm loads parallel Bridged. Parallel both speakers to get 1- 4ohm load, 20V / 4 = 5amps,
20V X 5 amps = 100 watts total


In all three configurations the same amount of power is supplied to the loads. Each speaker get’s
the same power, 50 Watts.
 
alright right yall, who cares whos right and whose wrong........ i hooked it up the way crabs diagram shows and its working great :cool: ......If i hear anymore bickering outta you two i will pull this car over! :eek: Anyway, thanks for the help. :D
 
No prob man,

Great to hear its working :D

I have wired a couple stereo`s in my day ;)

If you ever need any Car audio or Performance parts give me a message I give SC`ers a discount.

Or if you have any other car audio questions I am just a message away.

Thanks
Garett
 
I think the misunderstanding is J57ltr is missing the series part of the wiring on the sub between the 2 coils ON 1 SUB ALONE...... ie the black line that wires the 2 coils together.

Just thought I'd point that out................ I almost missed that myself.

Frit
 
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