Speakers Wired in Series Versus in Parallel

Hi all,

Can anyone tell me the pros and cons of wiring car speakers in series versus in parallel?

Someone gave me this info, quoted below...

"... Connect the speakers one way, and the speakers won't be very loud. Connect them the other way and the speakers will be louder but you risk burning out your head unit."


...but I don't know which as which characteristic, or if these symptoms are guaranteed, or just possibilities.

Thanks for any input.

numi


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numi

You can search for series & parallel (resistor) formulae & explanations.

2 speakers in series doubles overall resistance (hence generally 1/4 the power (output) but amplifiers may be different - eg, 1/2 the power output).

2 speakers in parallel halves overall resistance.

If an amp is rated for 4 Ohm or higher (or 1 Ohm & higher) you don't want 2 Ohm (or 0.5 Ohm)... you'll blow the amp at high power outputs.

Thanks oldspark,

It sounds like I'd want to go with in series to be safe.

But can you slightly clarify this sentence?...

"If an amp is rated for 4 Ohm or higher (or 1 Ohm & higher) you don't want 2 Ohm (or 0.5 Ohm)... you'll blow the amp at high power outputs."

Do you mean that if you have a 1 Ohm amp, you don't want 2 Ohm speakers?... meaning you don't want speakers that are a higher Ohm rating than the stereo unit/amp, or do you mean the other way around?

Thanks,

numi



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numi

No, the other way...
Your speaker resistance should never be less than what the amp rated for. That's another way of saying don't try to supply more power (current) into the speaker(s) than the amp is capable of.


Having higher resistance speakers is ok (despite what I once thought...). That means the amp's output will be less than what it can handle.


If you have a speaker which is matched to the amp (eg 1 Ohm sub on a "1 Ohm stable" amp, or 4 Ohm etc for typical non-sub amps) do not connect 2 or more of them in series unless you want LESS electrical output power. The volume control is a better way of of dropping output power (LOL?).
The highest output you can get from an x-Ohm amp using x-Ohm speakers is to use ONE speaker. You reduce output by series connecting the speakers. Or you can blow the amp by paralleling such speakers.

You would only series or parallel matched Ohmage speakers if speaker power handling is less than the amp.
EG - for a 100W amp and 50W speaker you would use FOUR speakers in series/parallel (ie, 2 series connected speakers in parallel with the other 2 series speakers). You then have the same Ohmage "speaker" load capable of 4x 50W = 200W power handling.

You could have only 2 of the above example speakers in series (none in parallel) but that means less amp output (typically ~half). (That does not apply to (newer??) impedance-independent amps.)

Thanks OS,

The info with my new stereo says "Speaker impedance 4-8 Ohms", and my new door speakers say "4 Ohms".

So does that means that it would be okay to run the door speakers from the dash speaker in parallel, so I wouldn't lose volume, since my new door speakers fall within the stated impedance range of my new stereo?

numi

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numi

You can have ONE 4 Ohm speaker on your stereo 4Ohm output; NOT 2 in parallel.

OS,

Sorry, but I'm having a bit of a hard time understanding you wording.

Do you mean just the right OR the left speaker could be run in parallel, and not both?

Again, the info with my stereo says, "Speaker impedance 4-8 Ohms".

Thanks,

numi



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numi

Your stereo info means "one 4 Ohm speaker per output".
An output is LEFT. Another is RIGHT. ETC.
(Forget 8 Ohms, you have 4 Ohm speakers.)   

Hence one 4 Ohm speaker on the left output/channel, and another 4 Ohm speaker on the right output/channel. (And similarly for rear left & right if applicable.)

Okay, so then, apparently, I'd be okay to run one speaker in parallel on each side, so as not to lose volume, I guess.

Thanks again!

numi

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numi

NO!!!
Parallel means connecting one speaker in parallel with another.
You can only have one 4 Ohm speaker on each stereo output.
If you want to add any new 4 Ohm speakers you have, then disconnect the existing speaker(s).

If you connect another 4 Ohm speaker in parallel with an existing 4 Ohm speaker, you'll have 2 Ohms on a (minimum) 4 Ohm output. That'll destroy your amp as per your OP and all I have subsequently written.
(Unless perhaps you make sure the volume control is never high enough to blow the stereo, but ytf would you want to have 2 speakers in parallel anyway?)

Wait, so actually, I guess that would be only one speaker from each channel, and if I'd connect another speaker off of either speaker in parallel, there would be a potential problem... then I might blow the stereo head unit.

So I'd want to wire any extra speakers from any of my 4 original speakers from this 4 speaker stereo in series, but I'd lose a little volume, right?

Thanks,

numi

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numi

Yes, you'd lose half the power (usually; approximately).

But go back to basics, WHY do you want to add extra speakers?

But wait, now I'm a little confused... if the stereo says "Speaker impedance 4-8 Ohms", that means simply having two 4 Ohm speakers would be the limit, and if I had any more draw on the stereo with any more speakers, like the back speakers, then that in itself, without any speakers run in parallel or in series, then it might cause a problem for this stereo head unit?

So, am I screwed with just 4 speakers.

Okay, I had a stock car stereo that crapped out, and it had six speakers... two in the dash, two in the doors, and two in the back.

Now I've hooked up a new stereo unit, but it only plays to the dash speakers and the back speakers, but I haven't turned it up very loud in my tests.

But I'd like to get the door speakers working, and I was going to sacrifice the little dash speakers by running the wires from the dash speakers to the new door speakers that I've now managed to install in the doors in spite of some other installation problems.

So even with that configuration, with just 4 speakers, based on what you are saying, I'm going to have a problem... if I turn up the volume with just my door speakers at 4 Ohms each and my back speakers, Ohms unknown, am I going to blow my new stereo?

And then what I was potentially planning to do was to keep the dash speakers hooked up, maybe get some new ones, and then run the door speakers in series or in parallel from the dash speakers.

Please tell me this isn't right!

numi

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numi

I've said what I've said. Maybe you can reread it?   

You can wire 2 4 Ohm speakers in series for each output...
And that will reduce the maximum power output of your stereo.

And it may make the sound worse since you can't just add speakers willy-nilly. Only occasional luck else design result in good or improved sound.   


If it's a typical/traditional amp, forget the "4 to 8 Ohms" spec. It effectively means "a minimum of 4 Ohms".
Less than 4 Ohms will blow the output (eg, at high volumes or peaks).
And the higher the Ohmage, the lower the power output will be (ie, max output, or undistorted output, or output at a certain volume control setting).

Okay, so I'd only be wiring 2 speakers from the right front channel in series, and 2 speakers from the left channel in series, and then the single pair of back speakers would be the only ones on the rear left and right channel, and then I'd be okay, I guess.

That's great. Sorry for the re-asking, but all the data was mixing me up... in this case, I suppose I needed it put as simply as possible.

Thanks, OS.

numi

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numi

Yes, you won't have as much output power and you might have worse sound, but it's safe.

Hi OS,

Here's what someone posted on this topic on another forum...

"the formula to calculate the impedance of 2 speakers in parallel is:

1 / ((1/R1) + (1/R2))

So in your case where you have a 4 ohm speaker in the dash and a 4 ohm speaker in the door, the formula becomes

1 / ((1/4 + 1/4))

Which becomes

1 / (2/4)

Which becomes

1 / (1/2)

Which becomes

2

So, if you wire those 2 speakers in parallel, the head unit will see a 2 ohm load across it’s terminals which is outside of it’s 4 - 8 ohm specification.

This means that if the head unit tries to feed power into that configuration it will trigger a protection circuit or burn out. "

This sort of made better sense of it for me.

numi

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numi

Yes, my first reply...

oldspark wrote:

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You can search for series & parallel (resistor) formulae & explanations.

2 speakers in series doubles overall resistance (hence generally 1/4 the power (output) but amplifiers may be different - eg, 1/2 the power output).

2 speakers in parallel halves overall resistance.

If an amp is rated for 4 Ohm or higher (or 1 Ohm & higher) you don't want 2 Ohm (or 0.5 Ohm)... you'll blow the amp at high power outputs.

---

I assumed you'd look up series & parallel if you wanted the tech stuff and hence find Wiki or similar.
But for equal resistances, the formula reduce to 2R & R/2 for series & parallel respectively (or nR & R/n where n is the number of resistors involved).
You then use P = k/R meaning Power delivered or used is inversely proportional to Resistance to understand the effect of a series or parallel connection (in your case).
[FYI: k is V*V or 1/(I*I) where V is the voltage across the resistance and I is the current thru it. That's from combining Ohm's Law V=IR and P=VI.]

OS,

This car stereo project was really meant, in a way, to be a pleasant diversion from the rest of what's going on in life, and just getting the wiring conversion with a conversion harness to work for the head unit became an insanely stupid task, but then getting that done brought me to this speaker conundrum, where my door speakers were left out of the equation.

Then the problem became getting the wires from the dash speakers to instead drive the door speakers, and the only alternative is apparently creating a bypass wire/wires that will have to run from each dash speaker grill outside the dash in to a newly drilled hole in the front area of each door, which leaves wires open to get caught on me or any passenger in the front seat, as seen in my fictitious bypass wires mock-up image seen below, because getting to the either side of the rubber tube grommet that holds all the power window and power lock wires in between the doors and the door frames to run the dash speaker wires through to the door speakers, which in theory would be from inside the dash above the kick panels, and inside the front edge of the door, are impossible to see, and unreachable from the door speaker hole for anyone with a forearm shorter than about 3 feet.

Then there was the bad automotive design that would have required me to take off the door panels (and break the brittle snap-in pieces holding it on while potentially making the door panels unable to ever be right again) in order just to get to each door speaker, which I was, as of yesterday, able to avoid by cutting the plastic door panel with a sawzall around each door speaker because the stock holes for the door speakers weren't big enough to actually get to the speaker screws or to remove the the speaker itself... now that's solved, as also seen in the images below.

Then the other day I was reading an old thread on the subject of the door speakers and someone mentioned running speakers in series, and I started thinking how I might actually be able run all six of my speakers, and replace the dash speakers and the rear speakers, in addition to the new door speakers I'd already purchased, and maybe I'd really have something to listen to in this old Mazda minivan.

That's what opened up this can of worms about "in series versus in parallel".

So instead of a pleasant diversion, as originally intended, this entire project, and all this talk about Ohms and math formulas has made me feel more like chanting "Oooohhhhmmmm".

Thanks again,

numi



















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numi

I don't suppose it was some car audio forum? I've made various comments on here about what I think of them tho there are some brilliant contributors.
Luckily we've had a few posts from audio forum guys which has only added support to my views.

No doubt the thread you read mentioned the (approximate) halving of the output power wrt to max output and volume control setting else explained the need to replace with speakers of half the existing speaker ohmage.
They should also have mentioned the complications of adding speakers - usual crossovers are used else proper design wrt location etc (phase delays to ears etc).   


Replacing existing speakers is common practice, but not adding speakers to existing wiring & speakers. (After all, the best sound is usually from single speakers per channel tho that may mean tweeters & midrange, and a separate sub etc.)


PS - my original question WHY do you want to add extra speakers? was intended from a project or DIY POV but a sound POV - ie, better sound? louder sound? etc. I thought the answer would can the project since all outcomes result in a negative outcome (tho audio power versus acoustic power at the ear has merits).

Hi OS,

No, the other forum where I've been on this topic is a forum that is dedicated to my car's make and model... talk about people who love their cars, right?

I was actually getting info from two guys on that forum... one guy on a thread who was more technical (the guy who posted that formula) and then another guy who's past post about wiring his speakers in series I had read who answered me on private message a few times.

Here are a couple quotes from messages to me from the guy who's post I read that was about when he ran a set of car speakers in series with a set that was directly wired to his head unit...

QUOTE:

"I don't have that car any more, but never had an issue. I think the series way supposedly makes them less loud if I'm not mistaken, but you are sitting up front next to them and the rears are way in back anyway. Any mild mismatch is easily adjusted with the fader on the receiver. We ran them with head unit power, using a small amp for a subwoofer only. Never had issues with volume."

Our set up used an aftermarket head unit. It is a long time ago but I am certain we bypassed any factory amp and used only the head unit power.

It didn't matter that the resistance increased, because we had 4 speakers up front now instead of just 2. The volume was fine."

UNQUOTE

What I figure I'll do is to first wire it the way I first planned, just bypassing the dash speakers and wiring directly to the door speakers, and see how that sounds once the new door speakers are actually mounted in the doors, then I'll get a new pair of dash speakers and wire those and the door speakers in series and try to compare how those sound with the potential loss of volume balanced out with the fader.

So, all these forum posts will be my homage to ohmage, and I'll say "Oooohhhhmmmm" after hearing so much about ohms.    :^)

Thanks,

numi

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numi

Well, there's no supposedly about the series addition making them less loud, but that is subject to qualification.
For a given volume control setting - and for the amp's max output power - the electrical power for both speakers (ie, combined) will be less than for the single speaker as previously discussed.
However loudness is related to position and distance...

Fader adjustment is often required to keep the balance after volume changes (whether from lower power or added speakers or volume control adjustments).

Acceptable depends on the user and the system. My "cheap" HUs couldn't handle loud without being distorted so I would not have added more speaker. My usual Alpines are fine as is but doubling speaker resistance could reduce its max volume unacceptably, but I'm into thrash & hardcore and sometimes (therefore?) at its higher volumes. For "low volume" users - whether externally amped or not - there is usually enough reserve to compensate for higher speaker resistance.


And I forgot to say before, yes - I like your ohm pun!