Parallel Output Jacks on an AMP

fenderdude

New member
Hey everyone one of my power amps reads the following in the manual:
The (output) jacks are wired together in parallel. The internal amplifier of the can deliver its full power output into as little as 2 ohms. The chart below can help determine the total impedance load when connected to various combinations of speakers in parallel. Never connect the mixer to any combination of speakers that have a total impedance of less than 2 ohms!
SPEAKER NUMBER OF TOTAL
IMPEDANCE SPEAKERS IMPEDANCE
4 ohms 2 2 ohms
8 ohms 2 4 ohms
8 ohms 4 2 ohms
16 ohms 2 8 ohms

etc. etc.
Since the output jacks are wired in parallel, does it mean that the speakers must be wired in parallel also for the above chart to be correct or can they be hooked in series and get the same effect? HELP!!! (what if the speakers are wired in "parallel" also? Does that make a difference?) I can't seem to get a straight answer on this...
THANKS!
Fenderdude :cool:
 
To calculate total impedance of more than one speaker or cabinet in parallel, assuming each speaker or cabinet is of the same impedance, divide the impedance of one of the cabinets (or speakers) by the total of cabinets (or speakers).

The mathematical formula for impedance in parallel is 1/R = 1/R1 + 1/R2 + 1/R3 + ... 1/Rn

If you plug your numbers into that, solving for R, and you have, for example, two speaker cabs that are 16 ohms each, you get:

1/R = 1/16 + 1/16
1/R = 2/16
1/R = 1/8
R = 8

Your total impedance for two 16 ohm cabs in parallel is 8 ohms. Since both cabs are 16 ohms, though, and there are two of them, its much easier to divide 16 by 2 and get 8 ohms.

On the other hand, two 4 ohm cabinets in parallel is going to be a 2 ohm load, which is low, so double check that your amp is capable of handling that load.

Don't worry about how the individual speakers are wired in the cabinet, as long as you know the total impedance of the cabinet.

If I've made a mistake please feel free to correct me.
 
fenderdude said:
...Since the output jacks are wired in parallel, does it mean that the speakers must be wired in parallel also for the above chart to be correct or can they be hooked in series and get the same effect?
Nah. Anything connected to the two output jacks become combined in parallel but amp just see total. That doesn't mean any of the loads at either jack couldn't come from a single speaker, or series/parallel combo in a cab or whatever combination.

:cool: :)
 
fenderdude said:
Hey everyone one of my power amps reads the following in the manual:
The (output) jacks are wired together in parallel. The internal amplifier of the can deliver its full power output into as little as 2 ohms. The chart below can help determine the total impedance load when connected to various combinations of speakers in parallel. Never connect the mixer to any combination of speakers that have a total impedance of less than 2 ohms!
SPEAKER NUMBER OF TOTAL
IMPEDANCE SPEAKERS IMPEDANCE
4 ohms 2 2 ohms
8 ohms 2 4 ohms
8 ohms 4 2 ohms
16 ohms 2 8 ohms

etc. etc.
Since the output jacks are wired in parallel, does it mean that the speakers must be wired in parallel also for the above chart to be correct or can they be hooked in series and get the same effect? HELP!!! (what if the speakers are wired in "parallel" also? Does that make a difference?) I can't seem to get a straight answer on this...
THANKS!
Fenderdude :cool:
Fenderdude,

First a lesson on speaker basics so our discussions can be better understood. (It may help others too.)

Speakers put a load on the amp. To understand this better, think of the amp as a vehicle with an engine and think of the speaker as a trailer full of cargo. The trailer (like dead weight) puts a load on the vehicle and forces it to work harder. The more speakers you connect to a single amp channel, the greater the workload becomes.

This load is measured in Ohms. (Well, it is really a calculated average because the workload is also based on the information being played.) The greater the load, the lower the number given so, 2 ohms represents a heavier load than say 16. If you connect two 8 ohm speakers together (in parallel) they appear to double the load to 4 ohms. This scenario is for a single amp channel only. Each channel is usually independent and can operate at different loads. Hooking one 8 ohm speaker to channel A and another to channel B results in an 8 ohm load for each channel.

This works for speakers wired in parallel. If you hookup speakers in a series configuration, they will have the opposite effect. Two 8 ohm speakers wired in series will result in a 16 ohm load.

When you force the amp to work harder, it also puts out more watts. (Well, until it reaches its limit, anyway.) For example: when an amp has an 8 ohm load attached to it, it may only put out 100 watts on average. But, when you increase the load to 4 ohms, it will now put out closer to 200 watts in response. Two 100 watt 8 ohm speakers can share the wattage and still absorb 200 watts as a team.

Wattage and ohm load are two separate measurements but both should be given equal consideration.

The chart you are viewing is simply trying to help you determine how hard you are making your amp work based on what speakers and how many you have hooked up. Their wording may have confused you. Many amps have the ability to pair two channels together (internally) and behave like one big channel. This is called bridging and it effectively doubles the output wattage. Perhaps they call this "parallel" output. I don't know. Regardless, the same rules apply as far as ohm load.

As a general rule, each amp channel should be double the wattage rating of the speakers you connect. (Yes, this is safe!) You should never force any amp to work at less than 2 ohms. It will probably break down. Most amps work up a sweat when working at less than 4 ohms. 8 ohms seems to be the "comfort zone" for most modern amps. Never go below 4 ohms if amp is bridged. Also consider, if you run an amp at heavier loads, make sure it has plenty of ventilation because it will likely get hotter.

I hope this helps. Good Luck,
RawDepth
 
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And let's not forget series/parallel... 4 speakers at 8 ohms: The two pairs are joined in series and then connected to the amp in parallel... The amp sees 8 ohms
 
Ok, thanks for all the info folks! So in other words, if I hook up two 8ohm speakers to my amp (one to each channel) and the outputs on the amp are wired in parallel, the amp will see 4 ohms? Is this correct?
 
fenderdude said:
Ok, thanks for all the info folks! So in other words, if I hook up two 8ohm speakers to my amp (one to each channel) and the outputs on the amp are wired in parallel, the amp will see 4 ohms? Is this correct?
Yes.

Even though everyone is using the word 'speaker', you could easily use the word 'cabinet'. It is not necessary to know the impedance of the individual speakers in a 4x12 cabinet, you just need to know the impedance of the cabinet.

BTW, the outputs are not different channels. There is two of them just for convienence, they both are the same output.
 
fenderdude said:
Ok, thanks for all the info folks! So in other words, if I hook up two 8ohm speakers to my amp (one to each channel) and the outputs on the amp are wired in parallel, the amp will see 4 ohms? Is this correct?
You are correct
 
Ok, cool. Now here's another, I have a Behringer 1500 amp. I use the "banana" connectors to power two FOH speakers. Are those wired in parallel as well? I know you can piggy back them, that would be "bridging" right? It gives a heck of a lot more power that way?
 
fenderdude said:
Ok, cool. Now here's another, I have a Behringer 1500 amp. I use the "banana" connectors to power two FOH speakers. Are those wired in parallel as well? I know you can piggy back them, that would be "bridging" right? It gives a heck of a lot more power that way?

If it's a stereo power amp, and there are two banana connectors, they won't be in parallel. There will be one for each channel.

Piggybacking two banana connectors is not bridging. If you piggyback banana plugs, the speakers connected to them will be in parallel.
 
fenderdude said:
Ok, cool. Now here's another, I have a Behringer 1500 amp. I use the "banana" connectors to power two FOH speakers. Are those wired in parallel as well? I know you can piggy back them, that would be "bridging" right? It gives a heck of a lot more power that way?
Did the power amp come with a manual?

It's a stereo power amp. It has two channels and two outputs. If you want to bridge it, you have to set the mode switches the right way and use the two red speaker connections. This also turns it into a mono amp and changes the speaker impedance handling. You need to read the manual so you don't blow this thing up.
 
boingoman said:
Piggybacking two banana connectors is not bridging. If you piggyback banana plugs, the speakers connected to them will be in parallel.
Stacking Banana plungs gives a perfect visual example of a parellel connection.
 
fenderdude said:
Hey everyone one of my power amps reads the following in the manual:
The (output) jacks are wired together in parallel. The internal amplifier of the can deliver its full power output into as little as 2 ohms. The chart below can help determine the total impedance load when connected to various combinations of speakers in parallel. Never connect the mixer to any combination of speakers that have a total impedance of less than 2 ohms!
SPEAKER NUMBER OF TOTAL
IMPEDANCE SPEAKERS IMPEDANCE
4 ohms 2 2 ohms
8 ohms 2 4 ohms
8 ohms 4 2 ohms
16 ohms 2 8 ohms

etc. etc.
Since the output jacks are wired in parallel, does it mean that the speakers must be wired in parallel also for the above chart to be correct or can they be hooked in series and get the same effect? HELP!!! (what if the speakers are wired in "parallel" also? Does that make a difference?) I can't seem to get a straight answer on this...
THANKS!
Fenderdude :cool:
You are making this harder than it needs to be. Something is confusing about your original post. What is the make and model of this amp? I want to read about it for myself.

There is such a thing as parallel input mode but I never heard of Parallel outputs. Unless, of course, there are two speaker jacks for each channel. Then they could be refered to as "paralleled". That would explain the whole thing. :rolleyes:

Fenderdude,

We need more input!
 
RawDepth said:
You are making this harder than it needs to be. Something is confusing about your original post. What is the make and model of this amp? I want to read about it for myself.

There is such a thing as parallel input mode but I never heard of Parallel outputs. Unless, of course, there are two speaker jacks for each channel. Then they could be refered to as "paralleled". That would explain the whole thing. :rolleyes:

Fenderdude,

We need more input!

Ok here goes, the amp I am referring to is a "all in one" type powered mixer. It is a Crate PCM 8DP+(8 channel). It has two internal amps (each one has two outputs for a total of four) I use one set for a pair of FOH speakers and one set for monitors. I also use that as the head and run various outputs to two other racked amps. A Crown and a Behringer. I use those to drive 4 FOH speakers. I am going to be adding some 2 subs to the mix since I have a crossover. Does that make it more clear? I was confused on the Crate vs the racked amps. Since I run two 8 ohm cabinets of each channel of the Crate, it is pusing 4 ohms correct? I want to use my 1500 Behringer to push the subs. I was thinking I could also run 2 sets (4) of FOH cabinets off the crown by piggy backing banana clips of each channel on the Crown. Does this make sense?
Thanks! :eek:
 
Adam P said:
So each channel of the Crown would be pushing two 8- ohm cabs?

Yes, that is what I am planning, currently, I just run one 8 ohm cab from each channel. But if I piggy back another set of 8 ohm, it will push 4 ohms on each channel right? So it would look like this. Channel A banana clip piggy backed to another out to two sets of 8ohm cabs. (4 cabs x two channels, two cabs per channel piggy backed)
 
Right. The two 8 ohm cabs in parallel will put a 4 ohm load on the channel of your amp. If it can handle that impedance (and you're not severely underpowering the speakers) you should be good.
 
Adam P said:
Right. The two 8 ohm cabs in parallel will put a 4 ohm load on the channel of your amp. If it can handle that impedance (and you're not severely underpowering the speakers) you should be good.

I don't understand why it would be "underpowering" the cabs. Wouldn't it be pushing more wattage at 4 ohms thereby providing more power to the cabs?
 
fenderdude said:
I don't understand why it would be "underpowering" the cabs. Wouldn't it be pushing more wattage at 4 ohms thereby providing more power to the cabs?
It looks like the Crate mixer has two amps that are each mono channel. Each channel has two speaker jacks to enable you to use 2 FOH speakers and 2 monitor speakers. You are correct that each amp sees a 4 ohm load. No Problems there, I believe you have been using it correctly.

About the power concerns for the Crown...perhaps this will help. It is a good rule to follow. I believe it is very important with subs, mid-bass, and maybe hard driven mid range speakers, and a bit less important with higher frequency speakers.

You will need to dig up the power rating specs for your Crown amp and for the speakers to determine if they are well matched.

Good luck,
RawDepth
 
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