Amp/ohm tutorial

 

New member
Username: Tbonez

Post Number: 2
Registered: Oct-05
Does anyone have a good on-line tutorial for understanding ohms and bridging..

I am confused on how ohms regarding

mono D amplifier to dual voice coils ohms?
mono D amplifier to single voice coil ohms?
etc
 

Gold Member
Username: Basshead86

Ocala, FL USA

Post Number: 2078
Registered: Aug-05
www.bcae1.com

www.the12volt.com
 

Bronze Member
Username: Need4bass

Post Number: 13
Registered: Oct-05
Ohm is a unit of resistance and/or impedance

A speaker can be either SVC or DVC.

Each voice coil will have a given resistance. (2 ohm, 3ohm or 4 ohm). A SVC speaker will have only 1 while a DVC speaker will have 2.

You have two basic wiring configurations for 2 or more voice coils (keep in mind that a single DVC speaker has 2 voice coils:

1. series--> The positve(+) lead of the 1st VC is connected to the negative(-)lead of 2nd VC. The remaining (+) & (-) leads would then go to the appropriate terminals on your amp.

2. Parallel--> The positive(+) lead of the 1st VC is connected to the positive(+) lead of the 2nd VC. The negative(-) lead of the 1st VC is connected to the negative(-) lead of the 2nd VC. Then a conection from either VC's (-) & (+) VC should be made to the corresponding terminals on the amp.

Resistors (VCs) in series ADD. (i.e. 2 4ohm VCs in series will yield an 8ohm total load. 2 2ohms =4 ohms, 2 3ohms=6ohms, etc.)

Resistors(VCs in parallel DIVIDE by the number of resistors (VCs). (i.e. 2 4ohm VCs in parallel will yield a 2ohm total load. 2 2ohms = 1ohm, 2 3ohms = 1.5ohm, etc.)

You may also use a combination of the two above methods: series/parallel (which I will save for later).

Just remember to match the final "load" to the RMS rating of your amp. If an amp is "4ohm stable", be sure the load that you connect to the terminals is not LESS THAN 4 ohms.

An amp may be rated at 4ohms in stereo (i.e. 2 channels) and 2ohms mono(i.e. 1 channel). In the case of a Class D amp, nearly all only have a single channel of output. They may have terminal connections for 2 speakers but, it is still a single channel. So, if you have a single channel Class D amp that is 1ohm stable, connect as many speaker to it as you like (within reason) just make sure that the total load is not LOWER than 1 ohm.

A DMM (Digital Multi Meter) is a great tool to use. You can wire up your subs and then use the DMM to measure the final "load" of the speakers before connecting it to your amp.
 

Silver Member
Username: Tdisanto

Post Number: 249
Registered: Sep-05
"Resistors(VCs in parallel DIVIDE by the number of resistors (VCs). (i.e. 2 4ohm VCs in parallel will yield a 2ohm total load. 2 2ohms = 1ohm, 2 3ohms = 1.5ohm, etc.)"

This isnt necessarily true.

For two Resistors in parallelthe formula (R1*R2)/(R1+R2) can be applied.

Two 4 ohm Coils in parallel yields (4*4)/(4+4)= 16/8 = 2 ohms.

But if you have one 2ohm and one 4 ohms sub (SVC) lets say, than simply DIVIDING by 2 will not work.

it would be (2*4)/(2+4)= 8/6 = 4/3 or 1.33

Not many people do that but you could i suppose.

Also, and the most important part is wiring more than two SVC subs in parallel. Again you just cant divide by 2.

For more than one resistor the formuala:
1/Req = (1/R1)+ (1/R2)+1/(R3)+...

So if you have three 4 ohm subs in parallel than the load produced to the amplifier would be:

1/Req = 1/4 + 1/4 + 1/4 = 3/4
Req = 1/(3/4) = 4/3 or 1.33 ohms

Similarly, three 2 ohm subs yields:

1/Req= 1/2 + 1/2 + 1/2 = 3/2
Req = 1/(3/2) = 2/3 or 0.66 ohms.

Hope that helps :-)
 

Bronze Member
Username: Need4bass

Post Number: 15
Registered: Oct-05
Good point, I didn't take into account that someone might actually "mix" woofers.
 

Platinum Member
Username: Glasswolf

Wisteria, Lane USA

Post Number: 10666
Registered: Dec-03
www.bcae1.com has sections on everything you asked, with great detail.
if that site misses any questions you had, feel free to point them out and I can try to answer them.
 

Silver Member
Username: Fandim

Reno, Nevada United State...

Post Number: 278
Registered: Jun-05
Need4bass, using three SVC 4 ohm subs isnt 'mixing' woofers. :-) And you'd end up having like a 2 ohm (two of them in parallel) with a 4 ohm (the third one adding it into the paralell mix)

;)
 

New member
Username: Tbonez

Post Number: 4
Registered: Oct-05
Great advice...thanks!
 

Bronze Member
Username: Need4bass

Post Number: 19
Registered: Oct-05
I didn't say using 3 SVC 4 ohm subs would be mixing woofers, but 2 4 ohm subs and 1 2 ohm sub WOULD be "mixing" woofers so-to-speak.
 

Anonymous
 
I have two DVC4ohm subs.. I can wire each sub to 2 ohms.. then wire those two subs together to 4ohms. THEN wire a third, SVC4ohm subwoofer to the mix for a total of 2ohms. Will each sub get equal power?
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