Calculating Speaker Cab Wattage.. I still don't get it

aT19er

Member
Messages
344
I've googled it and I'm still not quite sure I understand it.

I'm good with series and parallel in terms of calculating the Ohms, but I still need a little bit of clarification on how to figure out the watts.

For example,
- What would the total watts of four 100w speakers be in: series, parallel, and series/parallel?
- If the lowest wattage speaker is 60 watts, do you multiply that by the number of speakers?
 
Messages
344
Yeah, your safest bet is to multiply the lowest wattage speaker by the amount of speakers in cab. Might not be "technically" correct but it's the safest thing to do for the speaker sake.
 

Onioner

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2,862
The only difference between series and parallel is that when in series, you do indeed take the lowest wattage speaker and multiply it by the number of speakers, whereas in parallel it's more like the sum total. 'Course, that's just a guideline. Put one 15W speaker with three 60W speakers, wire 'em in parallel, and plug into a 100W head and you might have problems... But, generally speaking, so long as it's nothing extreme, parallel wiring lets you use the sum total as wattage, instead of the lowest wattage.

And, don't worry, speaker wattage is never as simple as it seems. The rules of thumb are just guidelines. Since most folks don't really want to push a speaker real hard, it just becomes about having enough handling power. It only becomes trickier if you do want to push those speakers. Doesn't help that different companies' wattage ratings mean different things, and different amps wattage ratings can vary a lot too... But, use the series/parallel guidelines, and the 'double the amp wattage rounded down' rules and you'll at least be relatively free of blown speakers.
 

Tone_Terrific

Silver Supporting Member
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33,023
For example,
- What would the total watts of four 100w speakers be in: series, parallel, and series/parallel?
- If the lowest wattage speaker is 60 watts, do you multiply that by the number of speakers?
For all intents and purposes outlined, for those configurations, the power dissipated across each load, assuming equal impedances, will be similar, so, yes.
 

hipfan

Member
Messages
2,301
Yes, indeed. Series or parallel doesn't matter assuming speaker impedances are the same. For instance, a 2x12 cab with one 30 watt speaker and one 50 watt speaker *always* should be considered a 60 watt cab, regardless of whether it's wired in series or parallel. It's not like the amp or the speakers "decide" to send more power to the stouter speaker, although that certainly would be cool. :)
 

IM4Tone

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Messages
3,770
Yes, indeed. Series or parallel doesn't matter assuming speaker impedances are the same. For instance, a 2x12 cab with one 30 watt speaker and one 50 watt speaker *always* should be considered a 60 watt cab, regardless of whether it's wired in series or parallel. It's not like the amp or the speakers "decide" to send more power to the stouter speaker, although that certainly would be cool. :)
^^^TRUE! What's more important to me, assuming the speaker(s) will handle the amp's output wattage is the speaker sensitivity given in db. It states the spl with an input of 1 watt measured at 1 meter. The better ones are around 100 db. Now that's loud for only one watt input!
 

GCDEF

Silver Supporting Member
Messages
27,899
^^^TRUE! What's more important to me, assuming the speaker(s) will handle the amp's output wattage is the speaker sensitivity given in db. It states the spl with an input of 1 watt measured at 1 meter. The better ones are around 100 db. Now that's loud for only one watt input!
Efficiency isn't really related to quality. All that means is they're loud, not that they sound good. Some people seek out less efficient speakers to tame amps that are otherwise too loud.
 

aT19er

Member
Messages
344
What amp? What type of music?
Mesa SOB. Right now my cab's loaded with some silver speakers with a square back to them where you can see the magnet inside. From what I can tell they're an Eminence speaker with an alnico magnet. There's a certain tone to the high end that just won't go away, I think it may be that Icepick I hear about on here.

Anyway, for music type I'd say that late 70's/early 80's hard rock sound is what I'm going for. Debating between some Greenbacks or a ET65/Veteran 30 combo.
 

IM4Tone

Member
Messages
3,770
Efficiency isn't really related to quality. All that means is they're loud, not that they sound good. May not be absolute, but you will find that most often, the higher end speakers within a given brand have higher sensitivity. Just browse the various common websites such as Celestion. Some people seek out less efficient speakers to tame amps that are otherwise too loud. Yes, some do...I don't.
:D :D :D
 

GCDEF

Silver Supporting Member
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27,899
I'll say again, efficiency and quality aren't related. I could throw out the Greenback as an example.

Just because you prefer higher efficiency speakers, doesn't mean they're better than lower efficiency, just that they're louder (unless of course your definition of good is loud.) There are good, bad an halfway decent speakers with all kinds of different efficiencies.
 

IM4Tone

Member
Messages
3,770
I'll say again, efficiency and quality aren't related. I could throw out the Greenback as an example.

Just because you prefer higher efficiency speakers, doesn't mean they're better than lower efficiency, just that they're louder (unless of course your definition of good is loud.) There are good, bad an halfway decent speakers with all kinds of different efficiencies.
And we will respectfully disagree.
Some common Celestion speakers of various quality:
1) Rocket 50.....95db; $55
2) Seventy/80...98db; $79
3) Vintage 30....100db; $145
As I said before it isn't absolute, and other factors do play a part such as magnet type, but if you look at my initial post I said "....What's more important to me....... is the speaker sensitivity". And it remains so. And if there is correlation between cost and quality within a brand, I see a trend (even if imperfect).
 

rvhalejr

Member
Messages
3
I've been messing with cabs, running them up until they distort and then backing off.

Since what I do is different I thought I'd post, may find some others who have taken this journey into the realm between the theorist and experimentalist.

I take streaming audio (128kbps) from itunes/radio/religion/K-LOVE (not sharing signal ground between stereo channels) either analog direct or USB to analog.

Signal goes into ten band stereo equalizer and then into a 100w RMS stereo amplifier (with a tuner I do not use). The reason I mentioned the exact stream used is that there are two songs that have a mix of one or two notes that make my woofers make a sound like they are dying, which is fine (hey two hours of program material and less than six seconds of distortion for which I have upgraded parts on the way).

There are Five Components in each channel (Woof, Mid-Woof, Midrange, Mid-Tweet and Tweet [or big ass horn]). I get maximum spl, fidelity and dynamic range by doing this (with lots and lots of testing different network configs).

I defer to series instead of parallel to avoid the less than 4 ohm load. By definition a series circuit is a voltage divider based on impedance (frequency response of the band-pass filter in sum with the components inductance).

I've constructed a band pass filter specific to component, hand wound coils (it actually works) and sized caps for the each frequency band.

I use touch and my ear to judge the speaker load and its never level between any two (except for sibling left and rights). So I've found that the 10ohm 10watt Ceramic resistor to be my best friend, I can fine tune it better but 10ohms is my favorite because by replacing the resistor with another speaker I get sound for my electron (holes) instead of the heat generation.

Once Levels and Frequencies are matched to the components the fun really begins. With a Ten band eq and five physical band pass filters it all plays nice and the resulting EQ curve is the familiar S curve (as it should be).

Although it appears the the low end cross over is now about 125hz or 250hz instead of the old school 500hz.

I've not mentioned one thing about watts/cab because before it all gets tuned up and leveled calculations (except generally accepted relationships with band pass filter design and/or leveling resistors) are pretty useless.

When all the cabs are complete (Woofs have to be ported, Mids and Horns Sealed) the power amp seems to offer maximum clean output between 1/2 and 2/3 of full volume. There does seem to be a decision point above 1/2 as to use the loudness button or not. I am because I like the Punch and the cab network is being built to handle the load. I can turn it up to 1/4 without my ears aching.

About fourty-five years ago I built some speaker cabs for my first car (a station wagon hand down) with spectacular results. Through my life I have been no stranger to pro-audio and just wanted to see if that original concept I used as a kid would stand up to todays engineering (Maybe it was just my youthful Imagination).

To my surprise (as a one-time senior engineer in another life) it is once again producing spectacular results. I apologize for my laziness as I have not yet done spl and sectrum analysis because I'm having to much fun listening to my "New" but very very old stereo.

I've got another 100w amp to throw in the mix (well -- driven by a digital recording and mixing console for a small venue sound re-enforcement system or DJ or whatever you want to call it -- high end karaoke with TWO DAWS?)

Hey, its all good !!!
 

Stu Blue

Member
Messages
3,166
The only difference between series and parallel is that when in series, you do indeed take the lowest wattage speaker and multiply it by the number of speakers, whereas in parallel it's more like the sum total. 'Course, that's just a guideline. Put one 15W speaker with three 60W speakers, wire 'em in parallel, and plug into a 100W head and you might have problems... But, generally speaking, so long as it's nothing extreme, parallel wiring lets you use the sum total as wattage, instead of the lowest wattage.

And, don't worry, speaker wattage is never as simple as it seems. The rules of thumb are just guidelines. Since most folks don't really want to push a speaker real hard, it just becomes about having enough handling power. It only becomes trickier if you do want to push those speakers. Doesn't help that different companies' wattage ratings mean different things, and different amps wattage ratings can vary a lot too... But, use the series/parallel guidelines, and the 'double the amp wattage rounded down' rules and you'll at least be relatively free of blown speakers.
:mob
I'm sorry Mr Onioner but you don't know your onions... there is no difference in the power handling between series and parallel... you have to go by the lowest wattage speaker in the cab (x the number of speakers) in either case... I've never seen anyone claim this "total wattage" notion anywhere on the net... please don't repeat this nonsense in case someone believes you and blows all their gear up...
 

Onioner

Member
Messages
2,862
Stu Blue said:
:mob
I'm sorry Mr Onioner but you don't know your onions... there is no difference in the power handling between series and parallel... you have to go by the lowest wattage speaker in the cab (x the number of speakers) in either case... I've never seen anyone claim this "total wattage" notion anywhere on the net... please don't repeat this nonsense in case someone believes you and blows all their gear up...
I'm repeating what I've been told by professionals, including speaker manufacturers. I'm gonna go ahead and trust the professionals who i respect. Believe what you like.
 

Onioner

Member
Messages
2,862
Also, you definitely don't have to go by the lowest power handling. Countless real life applications have proven that.
 

Trebor Renkluaf

I was hit by a parked car, what's your excuse?
Gold Supporting Member
Messages
13,662
:mob
I'm sorry Mr Onioner but you don't know your onions... there is no difference in the power handling between series and parallel... you have to go by the lowest wattage speaker in the cab (x the number of speakers) in either case... I've never seen anyone claim this "total wattage" notion anywhere on the net... please don't repeat this nonsense in case someone believes you and blows all their gear up...
You are correct, assuming the speakers are the same impedance. In series, the speakers will have the same current flowing through them and the power dissipated will be determined by the impedance of the speaker(s). In parallel the speakers will have the same voltage applied to them and the power dissipated will once again will be determined by the speakers impedance.
 




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