#1
So, Im not very savvy when it comes to equipment so i am sorta confused about these ohms. I am planning on getting a Markbass stack that has a Little Mark III head. It says that you can get 300 watts with 8 ohms but 500 watts with 4 ohms. I mean 300 is fine for what i'll be playing but it's really a large difference for something i don't even understand
guitar solo - "meh, every song got one"
bass solo - "OMGZ0R U IS PRO MENZ"
#2
The thing that helped me understand ohms is to think of them as fractions. Pretty much 1/8 + 1/8= 1/4. So what that means is if you have two 8 ohm cabs they will equal 4 ohms in total. So if you have one 8 ohm cab the head will give it 300 watts. If you were to add another 8 ohm cab it will give the full 500 watts. It is important that you don't go over the amount your head give though. So dont have 2 ohms worth of cabs with only a 4 ohm head.

Edit: If that was confusing I understand and just let me know
So that with good courage we say, “The Lord is my helper. I will not fear. What can man do to me?”

-Hebrews 13:6
Last edited by TrabenBassist22 at Aug 17, 2010,
#3
Quote by TrabenBassist22
The thing that helped me understand ohms is to think of them as fractions. Pretty much 1/8 + 1/8= 1/4. So what that means is if you have two 8 ohm cabs they will equal 4 ohms in total. So if you have one 8 ohm cab the head will give it 300 watts. If you were to add another 8 ohm cab it will give the full 500 watts. It is important that you don't go over the amount your head give though. So dont have 2 ohms worth of cabs with only a 4 ohm head.

Edit: If that was confusing I understand and just let me know


Oh, i get it now. But what do you mean don't go over the amount of your head? Like what would happen if i had 2 ohms worth of cab. Also, since the head is able to play at 500 watts is there the possibility of destroying the cab if you crank it up and it's only 8 ohms?

Thanks alot though, i never could figure it out

Edit: Also, the cab says that it's 8 ohms but has a power handling of 400 watts. So now im confused lol Here's a link if you can look at it and help me understand Here
guitar solo - "meh, every song got one"
bass solo - "OMGZ0R U IS PRO MENZ"
Last edited by Rain_In_Blood at Aug 17, 2010,
#4
Ok what I mean by don't go over is what you said, dont use 2 ohms of cabs with a 4 ohm head. The head will be attempting to use more power then it has and it may blow. And no if you crank the amp at 8 ohms you shouldn't have a problem. The amp will only use 500 watts if it has 4 ohms of cabs.

If the cab has a power handling of 400 watts that's good for you because that means you can run the amp full power at 8 ohms and you don't have to worry about blowing out the cab. Since the cab can take 400 watts it can handle more then you head will put out, which is good.
So that with good courage we say, “The Lord is my helper. I will not fear. What can man do to me?”

-Hebrews 13:6
#5
Quote by TrabenBassist22
Ok what I mean by don't go over is what you said, dont use 2 ohms of cabs with a 4 ohm head. The head will be attempting to use more power then it has and it may blow. And no if you crank the amp at 8 ohms you shouldn't have a problem. The amp will only use 500 watts if it has 4 ohms of cabs.

If the cab has a power handling of 400 watts that's good for you because that means you can run the amp full power at 8 ohms and you don't have to worry about blowing out the cab. Since the cab can take 400 watts it can handle more then you head will put out, which is good.


ok, sweet. So like if im using just a 8 ohms/ 300 watt cab it could have the possibility to blow if i crank up all the way but with the 400 cab im okie dokie. Well now im super excited. Thanks dude
guitar solo - "meh, every song got one"
bass solo - "OMGZ0R U IS PRO MENZ"
#6
Yup, you got it. Hope you enjoy the new amp, Markbass stuff is supposed to be really nice. If you have anymore questions just let me know.
So that with good courage we say, “The Lord is my helper. I will not fear. What can man do to me?”

-Hebrews 13:6
#7
Quote by TrabenBassist22
Yup, you got it. Hope you enjoy the new amp, Markbass stuff is supposed to be really nice. If you have anymore questions just let me know.


Thanks, i am hoping to get it soon. They sound really good from what i have heard so far
guitar solo - "meh, every song got one"
bass solo - "OMGZ0R U IS PRO MENZ"
#8
Take your highschool physics class. You will do a unit on circuits. That class taught me everything I needed to know about how to match cabs and heads (and they said you dont learn anything useful in highschool). I will explain the basic terms to you and try to show you how they come together to help you match cabs and heads

Basically, ohms are a measurement of resistance. Resistors slow down the current. Say you have a current traveling at 9v (volts are a measurement of speed in the current). A resistor with a resistance of 5v will reduce the current to 4v (resistance is measured in ohms, not volts, but I used voltage as a representation here to more simply show the direct effect resistance has on current) Watts are a measurement of power so to speak. The more watts are going to the cab, the more power you have.

In this case, its okay to think of the relationship between volts and watts as direct. The faster the current moves, the more power (watts) is passing through the cab per unit of time. When you have a cab with a high resistance (8 ohms) the current is not moving as fast as the amp can make it, and therefore you get less power (watts). Thats why a cabinet rated a 600w at 2 ohms will only get 250w at 8 ohms. So basically, the more voltage, the more power. However, a current moving too fast will literally fry parts of the amp, because they are receiving too much power too fast. This is why its important to never go below the minimum resistance a head is rated for

Now you may be thinking, "If I have two 8 ohm cabs, shouldnt that give me 16 ohms?" And you would be right, IF cabinets were wired in series. But they are not. They are wired in parallel. The difference is too much to explain in one internet post (which is why you should take the class), but essentially parallel circuits are more efficient and more even in distribution of power, which is why we use them. The way they handle resistance is more complex however, and you need to use a special equation when figuring out total resistance.

1/R+1/R...=1/R total

For each resistor (cab), you divide that resistance by one. Then add all those numbers together. Divide 1 by that number, and you are left with the total resistance of all your combined cabinets. That is why two 8 ohm cabs give you 4 ohms of total resistance. Once you have this number, just set your head to that number and your golden. Or, if your like me and have a self rating head, just make sure that the number is not lower than the minimum resistance your head will run at. Most run down to 4 ohms, none that Ive ever seen go below 2.