TalkBass Forums (http://www.talkbass.com/forum/)
-   Amps [BG] (http://www.talkbass.com/forum/f15/)
-   -   Ohms question (http://www.talkbass.com/forum/f15/ohms-question-947723/)

 bigtexashonk 01-11-2013 07:52 AM

Ohms question

1 - 8 ohm cab run with 1 - 4 ohm cab + a 6 ohm load. Correct or not?

 Chef 01-11-2013 07:55 AM

Not.

2.67

 Chazinroch 01-11-2013 08:15 AM

That's right 2.67 ohms. The lower the ohm number the less resistance. Less resistance draws more power. That why amps rated at 4 ohms start to over heat and/or burn up when paired with a 2 ohm speaker load.

 bassmeknik 01-11-2013 08:18 AM

yep, 2.67 ohms (or 2 2/3 ohms if you prefer)

 ThisBass 01-11-2013 01:45 PM

Quote:
 Originally Posted by bigtexashonk (Post 13702831) 1 - 8 ohm cab run with 1 - 4 ohm cab + a 6 ohm load. Correct or not?
1 - 8 = -7
1 - 4 = -3

- 10 + 6 = -4

Correct or not?

 Chef 01-11-2013 01:47 PM

In terms of ohms, that^^^^^^is totally wrong.

 ThisBass 01-11-2013 01:48 PM

Quote:
 Originally Posted by Chazinroch (Post 13702916) That's right 2.67 ohms. The lower the ohm number the less resistance. Less resistance draws more power. That why amps rated at 4 ohms start to over heat and/or burn up when paired with a 2 ohm speaker load.
Appro 3 Ohm

Unlikely the "average" amount runs below 3 Ohm

 two fingers 01-11-2013 01:48 PM

2.67 Ohms. Reciprocal formula. More here.

http://www.tpub.com/neets/book1/chapter3/1-26.htm

 B-string 01-11-2013 01:52 PM

No Parallel: RT = (R1R2)/(R1 + R2)
4X8 / 4+8= 2.6666.......... Rounded to 2.67

 Kmonk 01-11-2013 01:54 PM

 ThisBass 01-11-2013 02:01 PM

Quote:
 Originally Posted by Chef (Post 13704649) In terms of ohms, that^^^^^^is totally wrong.
but

SQRT(-1) = j [ohm]

 B-string 01-11-2013 02:04 PM

If you would like to rewrite the books be my guest, won't make it correct. Formula and links have been offered.

 ThisBass 01-11-2013 02:08 PM

Quote:
 Originally Posted by two fingers (Post 13704657) 2.67 Ohms. Reciprocal formula. More here. http://www.tpub.com/neets/book1/chapter3/1-26.htm
I'm not at school but thinking about the real physics of speakers.

You can't predict the impedance unless you measure the impedance with a proper frequency band measuring voltage and current.

Most of the time the impedance calculates a bit above the nominal.
Depending on EQ settings the impedance varies upwards to higher values (most of the time).

But, ..so what.

 ThisBass 01-11-2013 02:12 PM

Quote:
 Originally Posted by B-string (Post 13704745) If you would like to rewrite the books be my guest, won't make it correct. Formula and links have been offered.
That's right, but understanding Formulas is a very different animal

edit:
Sorry I was wrong, I tried to tell:

 Chazinroch 01-11-2013 02:20 PM

The OP stated this:

1 - 8 ohm cab run with 1 - 4 ohm cab + a 6 ohm load. Correct or not?

But I think they meant this:

1 - 8 ohm cab run with 1 - 4 ohm cab = a 6 ohm load. Correct or not?

2.67 is correct.

 ThisBass 01-11-2013 02:21 PM

Quote:
 Originally Posted by B-string (Post 13704679) No Parallel: RT = (R1R2)/(R1 + R2) 4X8 / 4+8= 2.6666.......... Rounded to 2.67
That's not wrong (theoretical) but does not reflect the behavior of a real terms 8 Ohm and 4 Ohm speaker.

 Chef 01-11-2013 02:22 PM

No.
one 8ohm cab with one 4 ohm cab = 2.67 ohms, as has been said many times in this thread already.

Quote:
 Originally Posted by Chazinroch (Post 13704853) The OP stated this: 1 - 8 ohm cab run with 1 - 4 ohm cab + a 6 ohm load. Correct or not? But I think they meant this: 1 - 8 ohm cab run with 1 - 4 ohm cab = a 6 ohm load. Correct or not? 2.67 is correct.

 B-string 01-11-2013 02:24 PM

Speaker are rated for nominal impedance, the point in the pass-band they present the maximum load on the "amp". This is the figure of concern and a simple resistance formula can apply. In reality speakers have inductive and capacitive reactance (to a much smaller degree) as well.

IF you limit the "speakers" to a frequency much higher than lowest part of the impedance curve then you will need to calculate that new impedance. From there you can use the same resistance formula to obtain the new load presented.

 ThisBass 01-11-2013 02:34 PM

Quote:
 Originally Posted by ThisBass (Post 13704633) 1 - 8 = -7 1 - 4 = -3 - 10 + 6 = -4 Correct or not?
That was meant to be a joke

 B-string 01-11-2013 02:36 PM

You forgot the :)

All times are GMT -6. The time now is 06:51 PM.