amp stuff

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how can you set up an amp to 2ohms instead of 4? its a 4 channel amp, and imrunning 4 speakers, what the hell are ohms!??????

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*looks across the emergency room to Doctor Cody* "You can have this one... I'm done with trauma patients for the day".

Jstas

Originally posted by beans
how can you set up an amp to 2ohms instead of 4? its a 4 channel amp, and imrunning 4 speakers, what the hell are ohms!??????

You don't "switch an amp to 2 ohms". An ohm is how the resistance of a circuit is measured. Ohms measure impedance which is what the resistance of a circuit is called. The only way to change the impedance of the circuit is to change the physical properties of the circuit.

The way you do that is by changing parts with different impedance levels. You can do this by adding resistors and/or capacitors or getting wire with a high impedance rating (risking fires and electrical shorts that way though). However, changing wires is difficult for the average joe to do because, most people don't have the first clue about electrical impedance let alone the impedance of a wire. Adding resistors and capacitors to the circuit is also not for your average joe because again, knowledge of elcectrical circuits is needed.

However, you already have 4 large resistors in your circuit already. Speakers themselves are resistors. That is why they have an impedance load and a frequency range associated with them. If they were not resistors then we wouldn't have a range. They would be something more along the lines of a diode and limited only by voltage and wattage. But, they aren't so we have resistors.

The typical full-range speaker is usually rated at 4 ohms. These are, in many cases, coaxial speakers. This means that there are 2 drivers in a single speaker. Usually a woofer and a tweeter. If you had a woofer, mid-range and tweeter, they would be triaxials. Each speaker has an impedance load. When combining speakers on the same circuit like the front left channel of your amplifier, to determine the actual impedance, you must add the impedance of the speakers together. However, it is backwards math. Adding the impedance of two 4 ohm speakers yeilds an impedance of 2 ohms. There is actually less resistance which yeilds an exponentially higher power level but seriously taxes the amplifier's power supply. That is why certain amps are listed as NOT 2 Ohm stable, because the power supplies will not only clip but they can melt down due to heat and short out. Electrical shorts always have a tremendous capacity to ignite fires.

Now, with all of thet in mind, your full range coaxial is rated at 4 ohms on a sticker on the magnet most likely. This does not mean that both the tweeter and the woofer are rated at 4 ohms a piece and you actually have a 2 ohm speaker. What has occurred is the manufacturer has matched an 8 ohm tweeter with an 8 ohm woofer and created a nominal impedance of 4 ohms for that total coaxial speaker package. So, it is resonably safe to assume, given common circumstances, that you have four 4 ohm speakers connected to your amplifier and your amplifier is running on a 4 ohm load.

To change that impedance load and see more power, you will need to wire an extra speaker to each channel of the amplifier. You can wire them in parallel by wiring the positive leads of each speaker together and the negative leads of each speaker together and then wiring one side to the amp leads. Or you can wire them in a series by wiring the positive amp lead to speaker 1's positive lead and wiring speaker 1's negative lead to speaker 2's positive lead and the speaker 2's negative lead to the negative lead of the amp. However, either way you wire them, the amp will still treat them as being wired in parallel without some fancy wiring to do it in series properly.

So, if you grab yourself some tweeters and wire them onto each of your 4 speakers, you will see your 2 ohm load but, make sure your amplifier can handle it and make sure that your 2 ohm power rating doesn't exceed that of the full-range speakers because it will destroy full-range speakers. They are not easily over-powered.


Just some extra info. A speaker's impedance level is determined by a few things but completely related to the voice coil. Impedance is determined by the kind of wire used to wind the voice coil, the kind of material used to make the core of the voice coil, the length of the wire used to make the voice coil and the number of coils in the voice coil. The reason the number of coils is a factor is because EM fields can change impedance and since a speaker operates on EM principles, they are kinda governed by the properties and behaviors associated with EM and EM fields. You can change your impedance levl by modifying the voice coil but, to do that, you need to take the speaker apart and I can only count about 5 competition level subwoofers that will allow you to disaasemble the speaker cone/basket assembly to get to the voice coil. However, if you modify your voice coil, not only do you modify impedance but you can also modify the frequency response range. So overall, it's a bad idea because in most cases you will have to break the speaker or you will destroy its properties and make it sound terrible so don't do it.

whitey240sx

he definietely knows what hes talking about haha

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*tom brokaw reporting*

"Another life saved by the crack staff at Polk Audio General Hospital..."

north51

jstas,

When you bridge an amp, aren't you wiring it in series instead of parallel? It this what decreases the resistance and doubles the power?

Jason

Systems

show off...
pretty much what hes trying to say if you didnt understand is this
ohms cant be changed by flipping a switch
the more speakers you have(in general)the lower the ohms...the more power
resistance....think of it this way...resistance is bad
more ohms....less resistance
less resistance...less power it takes to operate it...so at its RMS...itll really slam
for that amp
just hook it up positive to positive...negative to negative
that should give u a 4 ohm load...depending on your speakers....but most likely a 4 ohm load
bridging...in bridging...you dont connect speakers to speakers
and i would go into more detail but im REALLY tired and i had to wait for someone to get online
so if any of that is wrong...my bad...
but it should be right
-Cody

Systems

see...i told you i was tired...i thought you said wire it into 4 ohms
im sorry
im going to bed now...lol
-Cody

Jstas

Originally posted by north51
jstas,

When you bridge an amp, aren't you wiring it in series instead of parallel? It this what decreases the resistance and doubles the power?

Jason

Bridging an amp is not necessarily running in series. It has nothing to do with how the speaker is wired. Bridging the amp just allows you to use power from both channels at the same time. But if you will notice, most amps that are bridgeable must be switched by a switch to the bridged mode. This institutes a cross-over system that is designed to allow the seperate channels from the power supply to run in series. To run the speakers in true series wiring, you will need an external switch much like the bridged switch inside the amp.

I'm kinda loaded right now so, explaining the difference between series and parallel isn't working too good for me. But basically, you need a seperate switch for the speakers to be properly wired in series. I do not know of any car amplifier that will allow you to truely run in a series because of how the internal switching on the amp is wired.

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tell u what... why dont we just take all the amps that do more power at 2 ohms than at 4 and just "make" them run at 2 ohms.

all we need are a bucket fulla transistors and probably some better coils with which to build better / bigger power supplies... then we can throw cooling fans in them to make sure they dont overheat in their cases...

that way, at 4 ohms, they'll do their 2 ohm rated power, but by the time we're done we'll have actually built a completely different amp with double the power rating, half the cooling capacitor, and half the lifespan... but thats ok... cuz we'll just use it to run some JL's... at least it'll outlive the speakers.

*and to think -- i'm the sober one in this room... booo yah!*

TrappedUnder Ice

gee...all that and never really answered the question.
Most 4 channel amps can only be run 2ohms using all 4 channels. IF you want to do this..then each channel needs to have a 2ohm load..instead of 4ohms on each channel.

Some companies make 2ohms speaker/sets..some dont. If you want a 2ohm load..you either get some 2ohm speakers or mix speakers to get a 2ohm load.... putting 2 4ohm load speakers in parallel will result in a 2ohm load

1 thing I did not like..was the comparison of just adding resistors and caps to change the impedence load. Big draw back of this- your speakers ohm load actualy fluctuates..as where a resitor- is designed to maintain its ohmage load... not a good idea at all to use resistors to change your ohm load-

anyway...have a nice day:rolleyes:

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Thomas I think Jstas was only using that as an example -- a metaphor of sorts...

common sense tells you that if you use a 4 ohm resistor in parallel witha 4 ohm speaker to get a 2 ohm load then you're going to actually get the samepower through that speaker... assuming power doubles into 2 ohms for the sake of arguement... and u got 50 watts at 4 ohms... u'll get 100 at 2... but now u've got that resistor of equal resistance sucking up half hte current, so in actuallity u are still getting 50 watts.

The resistor comment seemed more to compare a voice coil to a resistor for the sake of easy explaination.

Jstas

Originally posted by TrappedUnder Ice
gee...all that and never really answered the question.
Most 4 channel amps can only be run 2ohms using all 4 channels. IF you want to do this..then each channel needs to have a 2ohm load..instead of 4ohms on each channel.

Um, I covered that. I wrote about it in the paragraph before the last one. Since he didn't mention a specific brand name, I gave a general rule of thumb. It's pretty much common sense to check out the limitations of the equipment you are buying in any aspect or even market for that matter. If your butt weighed 300 popunds, would you go and buy a chair that could only hold 200 pounds? I wouldn't think so. Same goes for the amps and speakers. If you have 2 Ohm speakers, would you buy an amp that can only run 4 Ohms? I would hope not. Eventhough you can increase impedance of a circuit using capacitors and transformers but I didn't want to get into a topic that complex for beans' first time out.

Originally posted by TrappedUnder Ice
Some companies make 2ohms speaker/sets..some dont. If you want a 2ohm load..you either get some 2ohm speakers or mix speakers to get a 2ohm load.... putting 2 4ohm load speakers in parallel will result in a 2ohm load

I know I covered that. Very few companies make 2 Ohm speaker sets and the ones that I have seen are pretty expensive because of the power handling abilities that are needed to run in a 2 Ohm environment.

Originally posted by TrappedUnder Ice
1 thing I did not like..was the comparison of just adding resistors and caps to change the impedence load. Big draw back of this- your speakers ohm load actualy fluctuates..as where a resitor- is designed to maintain its ohmage load... not a good idea at all to use resistors to change your ohm load-

Resistance and impedance vary due to changes in such basic things as simpel as heat. Even a resistor can fluctuate. However, I was not using the resistor example as an answer. I was only trying to give examples of things that can be done to "change the properties of a circuit". A single resistor will change impedance but it will also restrict power and such. To truely change impedance you would need a network of resistors and capacitors and maybe even a transformer to change impedance, adapt to the fluctuations of the impedance load and still maintain the original power levels. Check out any wiring blueprint for an audio circuit. The speakers are always represented as resistors because that is what they are and that is why I used the resistor example.

Originally posted by TrappedUnder Ice
anyway...have a nice day:rolleyes:

I didn't cover that and I can only wonder why you always have so much sand in your shorts about things that aren't really important. I answered his question as best I could and tried to educate him as best I could. There is alot more there to write down but I truncated it and made it as simple as possible to understand. If that means giving incomplete info or not completely accurate info to get the point across then I will do that. When he understands I will go and fix whatever harm was done by giving not quite right info. Its a learning process and you can't expect someone to sit down and understand everything right off the bat. That's why many poeple go through 15-17 years of schooling before they can make a decent living at such complex things like audio. Not everyone has the same frame of reference. Just because he can't speak on your level doesn't make him stupid. He is just ignorant on the subject and it is the responsiblity of those who know to answer his question in the best way. Not only the best way for you and the task of getting the info across but also the best way to help him understand the subject matter. If you just spout off a bunch of technical terms in the industry lingo and jargon then you have done him a disservice because your help really hasn't really helped him at all.

Sorry for being so long winded.

TrappedUnder Ice

KISS= keep it simple stupid...just food for thought

Jstas

Originally posted by TrappedUnder Ice
KISS= keep it simple stupid...just food for thought

That...was not cool. I didn't call you names and like I have already explained, I did not see a simple answer and gave him the best one that I could. I'd rather be long-winded, inconveinience you and have him come back and ask more questions than to give him a short reply that would just sour his experience and leave him not wanting to come back.

You still haven't told me what the bug up your **** is either. Why are you so miserable?

whitey240sx

its all fun and games guys

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Thomas probably just had somebody make him install some JL or something