Setup Nothing fancy I have:
JVC HU
JBL speakers front and back
800W amp bridged and connected to MTX Thunderform that holds 2 8's

When I have the volume turned up... loud, from time to time it kind of sounds like the speakers are losing power. Sounds kind of lower and distorted for a second then return to normal. Its very subtle but noticeable.

Just thinking I might have a Power supply problem.

Any ideas?

 

I am assuming you are talking about the subs losing volume and distorted. I would check the following:
1. Verify your amp is capable of running at 2 ohms, if you have the speakers wired for parallel. If in Series, verify the amp can operate bridged at 8 ohms. (This is critical) If the amp is not rated for 2 ohms bridged, you could be over driving the amp as your power out put near doubles, depending on the amp/design, when you half the ohms.

2. Verify you have a GOOD ground, and a good +12V (run two wires from the battery one (+) and one ground just to test/verify it is not the problem.

3. If you are pushing your amp for Max output, it is possible it is clipping, try lowering your sub send, if your radio/head unit have that adjustment. Some amps will have an adjustment at the input, if it does try turning back just a little. This is not the gain control, gain is the amount of amplification to the signal, similar to the volume control on a radio.

4. Again if you are running near or at max output it could be a thermal shutdown/heating protection circuit. Depending on the design, it could shutdown momentarily or for up to a minute. To check/test try making sure there is plenty of air around the amp. Try using a house fan pointed directly at the amp while in operation, after it has been "acting up".

Good luck and post back with any results.

Lee

 

thats your battery has given its life. get a replaced one for your car. it doesnt seem any other problem

 

An amplifier gain is not a volume control . And he is running that 2 channel amp at 1 ohm , that is probably the problem , It's a wonder it hasn't shut down or fryed yet .

 

wow.

 

hahaha thats what I said when I read that. Literally lol'd.

 

huh????

 

Where and or how do you get 1 ohm? I highly doubt that the MTX speakers are 2 ohm each or that the speakers are dual voice coils (4 ohms/coil)...I am doubting this seriously.

Yes, the Gain control is not a volume control you are correct. The Gain control varies the amount of "Gain" (amplification) of the signal output vs signal input of the amplifier. Where as volume will adjust the signal level being sent to the amplifier. I didn't see a need to be so technical but was trying to keep it simple for the the none technical person. I do not know the technical level of B_Dub.

Also, I doubt it is the age of the battery but it could be possible that he needs a Cap if he is pushing the amp hard and utilizing most of the 800Watts.

 

Not hard to figure out , whenever you bridge a 2 channel amp , you drop the impedance to 2 ohm . He is bridging a 2 channel amp(=2 ohm) and driving (2) 4 OHM subs wired in parallel(=2 ohm) 2 into 2 = 1 Total load on amplifier = 1 ohm . Hope this helps

 

Ok, not going to argue about this but that is not how it works. I have 10+ years experience working with Live Sound/Pro Audio equipment and a degree in electronics and computer technologies.

The Impedance rating (ohms) on an amp states the impedance the amp is designed and capable to safely operate at and what Watts the amp is capable of producing/delivering to the amp "Load". the Load is the Impedance of the speaker(s) connected to the amp. And amp without speaker connected to it does not have a load present. So the idea that an amp "bridged" has an 2 Ohm load already on it is false. Some amps have a switch on them that places the amp in the "bridged" mode. Other amps are placed into "bridged" mode by simply connecting the speaker(s) to the indicated terminals, usually the (+) Positive terminal from one channel and the (-) negative channel from the other channel (assuming we are talking about a 2 channel amp).

As I stated...if no load, a.k.a. speaker(s) are connected to the amp, it has no load. Just because an amp is placed into "bridged" mode does not mean that the amp itself has an impedance rating of 2 ohms. The load on the amp is determined by the speaker(s), the impedance rating of the speaker, and the configuration of the speakers. Has nothing to do with the amp being bridged or not. If you connect 2 - 8 Ohm speakers in parallel, to one channel of an amp the load will be 4 Ohms. There is no difference because the amp is in 2 channel mode vs being bridged.

From what you are saying and the logic you are applying that means a 2 channel amp in 2 channel mode that has one 4 Ohm speaker connected to it is actually running at 2 Ohms? This is not correct. The single 4 Ohm speaker is the load and the amp will see a 4 Ohm load.


Formula for calculating amp load/impedance.
Parallel formula:


Series Formula:


R = Speaker Ohm rating
Notice in the formula there is no Value for what mode the amp is in.


Another interesting thing is that you can not us a multimeter (Ohm) meter to accurately measure the impedance of a speaker. You will successfully measure the resistance of the coils (the wire wound in the coil) but that is not the impedance value. When a speaker is in operation due to EMFs (Electro Magnetic Fields) a phenomenon known as Induction occurs and it increases the load, to the amp. Which makes the amp see a higher load then the actual Ohms reading from a meter.


Not sure where you are getting your getting your info 1bad86vmax but you might want to research this topic a little more.


Hope that clears things up. If you doubt what I am saying try using google.
Best of luck

 

you gon start a fight wit dat one

too late

 

Youre really wrong. It makes me sad seeing things like this.

Cliff notes of the guy above me - the final load seen by the amplifier is 100% determined by the wiring configuration. His amp sees whatever it is presented with. And load stability is the same at all volume levels, although this is compounded by the increase in amperage draw at lower loads and the result could indeed be a reduced output voltage.

 

dem some fightin wordz

As bad as his English was, he actually has provided a better answer than anyone else in this thread.
Low voltage explains quite a good deal of the loss of output.

 

No I am right , I just phrased it wrong . When you bridge 4 ohm amp , the impedence presented to it will be cut in half . Two 4 Ohm drivers wired in Parallel is a 2 Ohm load on the Amplifier . Now cut that in half because your hooking them to a brideged 2 channel amp , and that my friend is a 1 ohm load on the Amplifier . I don't care how many years you've been doing pro sound , I've been doing 12 volt audio for 30 years , and this is correct . I think you need to do your research on 12 volt audio .

 

The impedence presented to each channel is cut in half. The load the overall amplifier sees is still the same. That is why most 2 or 4 channel amps are only 4 ohm stable when bridged, because each channel is seing a 2 ohm load and is only stable down to 2 ohms.

Even in your example, you are wrong. Each channel sees 1 ohm, not the amplifier itself. The amp still sees the 2 ohm load presented by the drivers.

I'm not talking about credentials, Im not sure why you are...

But you cannot "wire" an amplifier to a certain ohm load. It only reacts to the ohm load presented to it, and if it is stable at that load then it will provide a given amount of power.