parallel vs series ohm question.

[bryanonbass]

first off, i have used the search function and I thought I understood the whole impedance thing fairly well.

However in the manual of my new amp (yamaha bbt500h) there is a photo that confused me.
Basically it says if I run my speakers in series I add up the ohm ratings. So a 4 ohm and 8 ohm cab = 12 ohm load.
I have attached the image for you to view.

So that being said if I have the cable coming out of the amp to 1 8 ohm cabinet and 1 cable from that cabinet into a 4 ohm cab is that running at 12 ohms?

is there a difference between that scenario and one where I have 1 speaker cable running from the amp to the 8 oohm cab and another speaker cable running from the amp to the 4 ohm cab?

what is the difference between the 2 photos?

 

[Johnny BoomBoom]

Strange diagram........technically true...but it depends how the cabients are wired themselves.

Normally for daisy chaining (going from the amp to one cab then another cab), the cabs will be wired in parallel.....at least the Trace Elliot ones and the Ashdown ones I've used are!

So ,you'd need the parallel equation....so your imepdance would be 1/8+1/4 = 2.67 ohms (I cheated and did the maths in my head....).

Also worth thinking about, the 4 ohm cab will get 2/3 of the power, the 8 ohm cab will get 1/3 of the power - so you might wanna check their power handling figures!

Did this help?

If they are wired for series operation...then yeah, a 4 ohm cab and an 8 ohm cab will give a 12 ohm load...but I've never heard of that for bass!

 

[Bryan316]

NO. Absolutely not. (EDIT: bryanonbass, not Johnnyboomboom! Took me too long to type this crap up!)

Speaker cabinets are designed with parallel jacks. Whether they're 1/4" or speakon or banana clips matters not. You're sending a speaker cable from the amp to the first cabinet, going in and out, then from the first to the second cabinet, in and out.

What you have, is different than a series circuit. In a series circuit, you're pushing juice through the speakers in a line. You're adding up the impedance of the speakers together. In true series wiring, you'd have a 12-ohm load.

But your gear is wired parallel. Instead of pushing juice through one huge pile of impedance, you're dividing the current flow between the speakers. Imagine a garden hose. Imagine a speaker as stepping on the hose. In a series garden hose, you're stepping on the hose in many places. Each step squeezes the hose, restricting water flow through the hose. It's the same with electricity. Each speaker restricts the flow of electricity through the amp. The less resistance and restriction, the easier the amp can work.

Now, imagine instead of stepping on the hose a buncha times in one hose, we install a manifold block, and run a buncha hoses. Then, we step on each hose only once. It's gonna be far easier for water to flow to its destination this way.

So, when trying to calculate impedance in hooking up cabinets (or individual speakers) in parallel, you DIVIDE the impedance of the speaker loads. So first, flip your impedances upside down, as fractions.

1/8 plus 1/4 = 1/8 plus 2/8 = 3/8

Then, flip it back.

3/8 flipped = 8/3 = 2.67ohms.

That's your answer. 2.67 ohms.

Then, you look at your amp. What is your amp rated at? X wattage at 4 ohms? X Wattage at 2 ohms? Cuz if your amp can't operate as low as 2 ohms, you're in trouble. But... why?

When you run an amp, it generates heat internally. That's why amps have heatsinks and fans. The higher the resistance in the line, the less current the amp passes and less heat is built up. The lower the resistance is in the line, the more current the amp passes and more heat is built up. Some amps can only run as low as 4 ohms, cuz it gets too hot any lower than that. If it gets too hot, POOF!


That image from the manual doesn't say how low your amp can go. So you better find out.

 

[slyslam]

first off, i have used the search function and I thought I understood the whole impedance thing fairly well.

However in the manual of my new amp (yamaha bbt500h) there is a photo that confused me.
Basically it says if I run my speakers in series I add up the ohm ratings. So a 4 ohm and 8 ohm cab = 12 ohm load.
I have attached the image for you to view.

So that being said if I have the cable coming out of the amp to 1 8 ohm cabinet and 1 cable from that cabinet into a 4 ohm cab is that running at 12 ohms?

is there a difference between that scenario and one where I have 1 speaker cable running from the amp to the 8 oohm cab and another speaker cable running from the amp to the 4 ohm cab?

what is the difference between the 2 photos?
View attachment 63104

Unless specified most if not all cabinets have parallel connexions. Same apply for speaker output of your bass amplifier.
In your case 8 ohms parallel with 4 ohms=2,6ohms
(8 x 4) / (8 + 4)=2.6.
When you have same impedance you just divide the impedance by the number of cabinets:
8ohms / 2 cabs= 4 ohms total etc....

Usually, the series connections are made inside a multiple speaker configuration box(4x10"-8x10") to get a total impedance of either 8 or 4 ohms.
(8x10")- if all speakers are 8 ohms. you conect two banks of 4parallel speakers(8 ohms/4=2ohms) in series(2ohms+2ohms) giving a total of 4 ohms.etc...

If your amplifier is rated for 2 ohms you're ok otherwise you must have two 8 ohms cabinets for a 4 ohms total impedance.

 

[Liko]

It depends on how your cabinets daisy-chain. Most cabs with a daisy-chain jack will tell you on the back plate whether the chain will be in series or parallel. If the cab does not have this info, check the manual. If the manual doesn't say anything, most cabs (like 80%) daisy-chain in parallel. If you have a multimeter, take off the back control/jack plate and locate the contact for the tips of the input and daisy chain jacks. Touch one probe to one tip and the other probe to the other tip. If you read a resistance somewhere around the impedance of the cab (the DC resistance will be somewhat less than the actual impedance in use, but still significant), the daisy chain will be in series. If you read no resistance or fractions of an ohm, the chain will be parallel.

There are a lot of variables when you're talking about multiple outputs from the amp. Many amps that have multiple speaker outputs do one of two things; either they simply act as a daisy chain, putting the cabs in parallel, or the head is bi-ampable. "Bi-amped" means that the power amp has two seperate amplification stages. When one speaker is plugged in, those two halves are "bridged"; they both output to the one jack, giving you the full power of the amp through the cabs plugged into that jack. If two jacks are plugged in, the two halves are separated; one half powers the speakers on one output, the other half powers the cabs on the other output.

Bi-amp behavior is specific to an amp manufacturer. Sometimes bi-amping gives you the ability to take both halves down to the minimum impedance (meaning you can double the number of cabs or halve the impedance of the cabs versus being bridged); other times each half has a higher impedance than what is allowable when bridged. Some simply split the amp into two equal stages, others split into unequal halves and send lower frequencies to the larger amp while higher frequencies go to the other. Some, like GK, specifically design the upper stage not for a speaker cab, but for the tweeters in that cab (ostensibly giving you the ability to distort the cones' signal while keeping the tweeter signal clean)

 

[lug]

To run cabs in series, you'll need to build special cables. You run one side of your output to one side of the first speaker box, a single line from the other side of that speaker box to the next, and the next, etc. and the final single wire back to the other side of the output of your amp. I've never seen this done in real life and have never seen cables you could buy set up this way.

 

[bryanonbass]

thanks for the posts guys.
Like I said, I thought I had this pretty much understood. But that photo in the manual just threw me for a loop.

 

[funkydoug]

can I come in on this for some clarification of a similar but slightly different issue guys?
I run a head which does 45o watts @ 2ohms, 300 watts @ 4 ohms and 175 watts @ 8 ohms. You gussed it, its a peavey.

If I use a 8 Ohm 2x10 delivering 300 watts it gets 175 watts
Ig I use both outputs from the head into 2 seperate 2x10 cabinets each doing 300 watts @ 8ohms they each get 150 watts, giving me a real output of 300 watts.

here's the question...

If I have a night when I feel I need the full output from the amp can I run a thrid (!) 2x10 which can also handle 300watts @ 8ohms on a daisy chain from one of the other cabs (looks like its series but from the above discussion it saounds like it wont be) to get the full 450 watts from my 6 10 inch speakers?

I know I could alternatively get a 4x10 and one 2x10 but I really hate carrying the things about!

 

[asad137]

If I have a night when I feel I need the full output from the amp can I run a thrid (!) 2x10 which can also handle 300watts @ 8ohms on a daisy chain from one of the other cabs (looks like its series but from the above discussion it saounds like it wont be) to get the full 450 watts from my 6 10 inch speakers?

You can run another 8 ohm cab, no problem, but you won't be getting 450 watts -- the impedance of 3 8-ohm cabs in parallel is 2.67 ohms, so you'll be getting a little less than 450W. Not enough less for it to make a big difference, though. If they're all the same and in parallel, all cabs will get equal amounts of power.

Asad

 

[B_flat05]

So Bryan, what will give me more power, or volume I should say, parallel or series?