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Who truly understands Ohm ?

Posted:
Thu Apr 17, 2008 3:59 pm
by gbheil
Ohm OMG Ohm 4 8 16 WTF. I should not have to be an electrician to hook up my system. Does anyone have a rule of thumb they use.
How about a favorite resourse of information on hooking up PA's speakers and such. Its enough to drive me acoustic


Posted:
Thu Apr 17, 2008 7:13 pm
by Starfish Scott
AGAGAAHHHHHHHHH not acoustic.. aaggggghhhhhh
"The ohm is the electric resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force."
P=V squared divided by R.
P= Power, V=Voltage and R = resistance in ohms.
Other than mathematically, I am lost as well.
I'd really love to know if I could convert my 2 kustom cabs with (5) 12" speakers at 16 ohms to mains for my powered mixing board rated at 250 watts per channel at 8 ohms and not blow them. Ideally I'd love to use 2 stage monitors (2-12" and a horn per monitor) and the 2 cabs for vocals only.
As of now the only thing I think I would get is a burning smell. lol

Posted:
Thu Apr 17, 2008 7:44 pm
by gbheil
Captain Scott: Dude I think i found your answer. Check out this site it gives Ohm calculations for series and parallel wireing.
MarkTAW.com (sorry did not cut n paste but its on the google.)

Posted:
Fri Apr 18, 2008 1:51 am
by Starfish Scott
I am ashamed to say I read it and I still don't know the answer to my question. LOL
Where's the fing roadies/techs when you need one, dammit!

Posted:
Fri Apr 18, 2008 3:00 am
by RhythmMan
I know electronics.
If you take two 8-Ohm Speakers, and connect their positive teminals together, and then connect their negative teminals together, this = 4 ohms.
This is called parallel.
.
If you have two 8 ohm speakers, and put the positive signal feed to speaker one's positive, and attach speaker one's negative to speaker two's positive, and then put the negative signal feed to speaker two's negative - this = 16 ohms.
This is called series.

Posted:
Fri Apr 18, 2008 12:51 pm
by Paleopete
Captain:
Check my comments in the volume pedal thread, I forgot about this thread and made some comments there. I'm not retyping all that stuff...
Condensed version...
If your speakers have two jacks wired parallel, it should work. Wire both together, plug a cable into the second jack of either speaker and check it with a multimeter. Should be in the 7-10 ohm range, that will work. If it shows around 32 ohms, you're wired series, forget it.

Posted:
Fri Apr 18, 2008 1:48 pm
by gbheil

Multimeter! Damn why did I not think of that. Duh


Posted:
Fri Apr 18, 2008 4:30 pm
by Starfish Scott
I have to laugh, I remember when I first got those 2 cabs... Of course, the bottom speaker on both columns were shot/burnt/blown. So I had to get (2) 16 ohm speakers or rewire in series to be able to utilize the junk I had lying around.
Of course I went out and located 16 ohm speakers (thank you craigslist) and I even remembered that I was able to wire it the way it came originally in parallel. (my brain hurt at first, but after 2 aspirin and 15 minutes and reading Pete's other post, I was able to remember that if all the speakers in the cab are the same ohm/impedance and not half-assed, it's parallel wiring or at least those Kustom cabs were wired in parallel.)
I wonder what it's like to play with new PA equipment? LOL I doubt I'll ever know for sure.

Posted:
Fri Apr 18, 2008 6:17 pm
by gbheil
Got me a new multimeter for $12.00 ! Havent used one since I worked for Mobil Oil in the 1980's.
Re: Who truly understands Ohm ?

Posted:
Wed Jun 11, 2008 4:57 am
by mesatone01
sanshouheil wrote:Ohm OMG Ohm 4 8 16 WTF. I should not have to be an electrician to hook up my system. Does anyone have a rule of thumb they use.
How about a favorite resourse of information on hooking up PA's speakers and such. Its enough to drive me acoustic 
As long as ypur speaker load is higher than the amp load you are ok. no damage .. Not ideal or as effecient as a matched load but ok. Just don't go below the amps ohm rating then you got trouble

Posted:
Wed Jun 11, 2008 11:41 pm
by mistermikev
series = 8 + 8 = 16ohm
parallel = 8 * 8 / 8 + 8 = 4ohm
I believe this is how it's calculated. this represents two 8ohm speakers in series (pos to pos, neg to neg) and then parallel (neg of 1st spkr to pos of second)
the below site has a no-brainer simplification for parallel:
'if all the speakers have the same impedance then take the impedance of one divided by the number of speakers'
http://www.bcae1.com/spkrmlti.htm

Posted:
Thu Jun 12, 2008 3:06 am
by RhythmMan
mistermikev wrote: . . . this represents two 8ohm speakers in series (pos to pos, neg to neg) and then parallel (neg of 1st spkr to pos of second)
.
WRONG.
.
You have it backwards.
.
Series = neg. of 1st spkr to pos. of second
.
Parallel = pos. to pos., neg. to neg.

Posted:
Thu Jun 12, 2008 2:50 pm
by mistermikev
ooops, my bad... samich is right. I do have it backwards (just the wire connection part - the calculation part is spot on). Thanks for catching my bad buddy.
cheers.
mv

Posted:
Sat Jun 14, 2008 3:50 am
by RhythmMan

Posted:
Sat Jun 14, 2008 11:47 am
by HowlinJ
Does any one truly understand Quantum Gravity?
Housabout...wimin.....
drummers?
Bass players?
Bagpipers?......
H.J.