View Full Version : How Serious is Unequal Power Distribution Between Speakers In Series?

imyourmaster

10-10-2013, 06:38 PM

I've had a discussion with A JL Audio Tech guy today. I want to run 4 speakers off of one MHD750/1. That would require wiring each pair of speakers in series and then wiring both pairs parallel resulting in a 4ohm load. The tech advised against this. Allthough he said it has been done, this kind of set-up will result in an unbalanced distribution of power between the speakers which are wired in series. How serious is this issue? Generally, I believe most of us would like to know that each speaker is getting the same amount of power. Any thoughts on this?

With 4 of the same speakers and each pair wired in series, then the 2 pairs in parallel with each other, the distribution should be equal. Now, if it was 3 speakers wired series/parallel, then there would be a difference.

Not sure what happened to my post from last night, but here's the shortened version: Since all 4 speakers are 4 ohm (I assuming since you said you'll have 4 ohm total load), you add the two each in series, which gives you two 8 ohm loads in parallel. To find parallel resistance: 1/Rtotal=1/R1+1/R2 = 1/8+1/8, Rtotal = 4 Ohms.

You can use Ohm's law (V=IR) to figure out total current. I'll just use 12V to make it easier. 12=I*4 I = 3 ohms. This means total current is 3 ohms, so each parallel set gets 1.5 amps. To solve for the voltage drop of each speaker, use Ohms law again V1=1.5*4 = 6 Volts. Since all 4 speakers are the same resistance and getting the same 1.5 Amps through them, each one will have a 6 Volt drop across. Power is voltage multiplied by current, so each speaker will 1.5*6= 9 Watts. Each speaker will receive the same power. The difference between my scenario and real life is when your engine is running the 12V is really 14V and the amp is boosting that voltage even more to get your 200 W or whatever is going to your speakers. Per Ohm's Law though, they are receiving the same power.

Disclaimer: My last circuits class was 15 years ago. Maybe someone with more electrical smarts will come on and correct any errors I've made here.

Also, check out http://www.bcae1.com/ for any electrical theory and stereo install info.

imyourmaster

10-11-2013, 09:20 AM

Not sure what happened to my post from last night, but here's the shortened version: Since all 4 speakers are 4 ohm (I assuming since you said you'll have 4 ohm total load), you add the two each in series, which gives you two 8 ohm loads in parallel. To find parallel resistance: 1/Rtotal=1/R1+1/R2 = 1/8+1/8, Rtotal = 4 Ohms.

You can use Ohm's law (V=IR) to figure out total current. I'll just use 12V to make it easier. 12=I*4 I = 3 ohms. This means total current is 3 ohms, so each parallel set gets 1.5 amps. To solve for the voltage drop of each speaker, use Ohms law again V1=1.5*4 = 6 Volts. Since all 4 speakers are the same resistance and getting the same 1.5 Amps through them, each one will have a 6 Volt drop across. Power is voltage multiplied by current, so each speaker will 1.5*6= 9 Watts. Each speaker will receive the same power. The difference between my scenario and real life is when your engine is running the 12V is really 14V and the amp is boosting that voltage even more to get your 200 W or whatever is going to your speakers. Per Ohm's Law though, they are receiving the same power.

Disclaimer: My last circuits class was 15 years ago. Maybe someone with more electrical smarts will come on and correct any errors I've made here.

Also, check out http://www.bcae1.com/ for any electrical theory and stereo install info.

Funny you should say that...I also realized this morning that an entire string of posts are gone...

David Analog

10-11-2013, 09:31 AM

I've had a discussion with A JL Audio Tech guy today. I want to run 4 speakers off of one MHD750/1. That would require wiring each pair of speakers in series and then wiring both pairs parallel resulting in a 4ohm load. The tech advised against this. Allthough he said it has been done, this kind of set-up will result in an unbalanced distribution of power between the speakers which are wired in series. How serious is this issue? Generally, I believe most of us would like to know that each speaker is getting the same amount of power. Any thoughts on this?

With all four identical speakers, two left in series and two right in series, and those two series circuits in parallel, all four speakers will receive the identical power. The total/final mono load of the four 4-ohm speakers in this series/parallel configuration will be 4-ohms.

Do seriesed equal golf cart batteries deliver a difference in power based on the sequence? Of course not.

Maybe you could rotate your seriesed speakers every 20 hours so that they wear evenly. Just kidding.

I've had a discussion with A JL Audio Tech guy today. I want to run 4 speakers off of one MHD750/1. That would require wiring each pair of speakers in series and then wiring both pairs parallel resulting in a 4ohm load. The tech advised against this. Allthough he said it has been done, this kind of set-up will result in an unbalanced distribution of power between the speakers which are wired in series. How serious is this issue? Generally, I believe most of us would like to know that each speaker is getting the same amount of power. Any thoughts on this?

That wasn't Ward, was it? Doesn't sound like something he would say.

JohnE

10-11-2013, 10:45 AM

Funny you should say that...I also realized this morning that an entire string of posts are gone...

I'm pretty sure that several of my posts from last night are gone. But I've noticed that for about a year. I called some people out and they swear they didn't do it.

imyourmaster

10-11-2013, 01:27 PM

I'm pretty sure that several of my posts from last night are gone. But I've noticed that for about a year. I called some people out and they swear they didn't do it.

Hmmmmmm....the plot thickens...what's going on there behind the doors us regular folks are not allowed to enter?

imyourmaster

10-11-2013, 01:29 PM

That wasn't Ward, was it? Doesn't sound like something he would say.

No it wasn't...the name does not ring a bell. But whoever it was, he kept saying that it was not recommended. Should the guys at JL tighten up on their in-house training?

imyourmaster

10-11-2013, 01:31 PM

With all four identical speakers, two left in series and two right in series, and those two series circuits in parallel, all four speakers will receive the identical power. The total/final mono load of the four 4-ohm speakers in this series/parallel configuration will be 4-ohms.

Do seriesed equal golf cart batteries deliver a difference in power based on the sequence? Of course not.

Maybe you could rotate your seriesed speakers every 20 hours so that they wear evenly. Just kidding.

Lol! I'll suggest that as a solution to the tech at JL!