Attention all you sterio peeps out there! Wiring question here...

[DSMRevolution]

I am sure that this will be somewhat close to in car wiring, but this question has to do with home sterio wiring....

My friend has this 3-disc CD player in his room. He has like 2 subwoofers hooked up to it. It is a 4-ohm sterio. I am kind of wondering if he could do any damage wiring it like that. It is only made for two speakers. On one of the lines(channels), on the + he spliced and put a + for subwoofer #1. Then, on the - line, he spliced it again and put a - for subwoofer #1. He did that on the other channel too. Now he has a total of 4 speakers (including the subs) on those two channels. Wouldn't that be somewhat like bridging and put 8ohms on the cdplayer and possibly burn it up? Or would it ruin the subwoofers first

I don't want him to burn up anything. I thought about doing this on a cheap CD player in my room too, but I dont think I want to mess anything up either. If you know, please post!! Thanks everybody

 

[4g63tc]

ok try to be more specific, the ohm load is determinedon how the speaker is wired. if it is wired in a series the ohm load would be ( the ohm load of one sub+the second sub+ the third) if the subs are wired in parallel (the ohm load would be the same sub one+sub two+sub three divided by the number of subs ie: 8 Ohm+ 8 Ohm+ 8Ohm =24 Ohm Divided by 3 = 8 Ohm) so please be a little more specific and i can help you.

 

[DSMRevolution]

Ok, ill try!

There are two channels on the CD player. Each channel says to use a 4ohm speaker only.

On the first channel, he has two speakers wired to it. +'s together and -'s together. Each speaker is 4 ohms.

On the second channel, he has the same as above.

So I am assuming that that means he has it wired in parreal? or in series maybe?? sorry, I cant remember which is which..

Anything else I should post?? It is a 100watt system total if that matters.

 

[4g63tc]

ok it is wired in parallel + to +, and - to - if they are both 8 ohm speakers then he is running @ 8 ohms therefore he isn't overpowering his system he is underpowering it due to more resistance.

example 100 watts total power divided in to 2 channels 50 watts per channel@ 4 ohms. if you double the ohm loads per channel you effectively cut the power output to half. or 25 watts per channel @ 8 ohms. mind you this is all theory being that this is based on peak wattage, actually true wattage or RMS wattage is 70% of peak wattage.

are you confused yet?

i think i am.

 

[mitsuspeed]

Originally posted by 4g63tc
ok it is wired in parallel + to +, and - to - if they are both 8 ohm speakers then he is running @ 8 ohms therefore he isn't overpowering his system he is underpowering it due to more resistance.

example 100 watts total power divided in to 2 channels 50 watts per channel@ 4 ohms. if you double the ohm loads per channel you effectively cut the power output to half. or 25 watts per channel @ 8 ohms. mind you this is all theory being that this is based on peak wattage, actually true wattage or RMS wattage is 70% of peak wattage.


i think i am.

exactly

 

[DSMRevolution]

Sweet thanks! So what would happen if I wired the subwoofer between the speakers. ex. + on channel one and - on channel two?? That would be the same as bridging it I think. Would that harm anything?

Thanks again and you answered my other question perfect!!

 

[4g63tc]

yes that would be bridging the two channels, however you would need to find out if the amplifier is bridgeable, if not, it could be harmful to the system.

i would try to find a sub with an equal ohm load to the speakers you are already using and wire it in parallel you would recieve the same amount of power for both.

better yet use two smaller subs, and wire them to both cannels in parallel for stereo sound.

 

[NOSLO2PT0]

How about we do a little research first before we post? I sure wouldn't want to give out bad advice and then have someone blow their amp up due to my bad advice.

4G63tc - The info you gave him on parallel wiring is incorrect. Wiring 3 8Ohm subs in parallel does NOT give you an 8 ohm load. It is in fact creating a 2.67ohm load. That in itself could fry an amp if it's not built for it.

The formula you use: (R1 + R2 + R3)/N, where R1, R2, and R3 = impedance of each speaker, and N = # of speakers, is incorrect. The true formula for figuring out multiple (more than 2) speaker load is: Rt = 1/(1/R1 + 1/R2 + 1/R3 + 1/R4....) . Using that formula and 8ohm subs as YOUR example, we see that 1/(1/8 + 1/8 + 1/8) = 2.67. If we are using just TWO speakers and wiring in parallel, the formula changes a bit to: Rt = (R1 x R2) / (R1 + R2). The formula for all speaker wiring configurations can be found here

Also, you can't wire 2 subs in parallel and get "stereo" sound. Stereo implies a true left and right separate signal. Kinda hard to do that if you have BOTH subs hooked up to ONE channel of an amp.

Let's all take the time to do our homework and pass on USEFUL knowledge, not something that can potentially cause harm to fellow DSM'ers equipment, whatever it may be.

TIA,
Mike

 

[4g63tc]

ok, so you're right on both accounts.

the formula is correct. I haven't looked a book on ohms law since my first year of school 5 yrs. ago. I should have paid more attention.

Second, i really went out of my way to give a fellow dsm'er erroneous information,for this i apologise. Next time if i'm wrong call me on it, and prove me wrong, but don't think for an instant that i did it to wreck his equipment on purpose.

 

[NOSLO2PT0]

Never said you did it on purpose. Just wanted to make everyone THINK before they give advice. "How accurate is the advice I'm giving?" That's all.

Lots of guys on here do nothing but benchrace, then they try to tell someone what works best on their car, without ever having done the work themselves. So, they are either going on heresay or just speculation, which isn't good, in either case.

 

[4g63tc]

fine then ..nuff said!