Ohms question

Discussion in 'Amps [BG]' started by bigtexashonk, Jan 11, 2013.

1. bigtexashonkSupporting Member

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

2. ChefModeratorStaff MemberSupporting Member

May 23, 2004
Columbia MO
Disclosures:
Staff Reviewer; Bass Gear Magazine
Not.

2.67

4. Chazinroch

Feb 2, 2003
Ontario N.Y.
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.

5. bassmeknik

Nov 6, 2009
Fair Haven, MI
yep, 2.67 ohms (or 2 2/3 ohms if you prefer)

6. ThisBass

Aug 29, 2012
Germany
1 - 8 = -7
1 - 4 = -3

- 10 + 6 = -4

Correct or not?

7. ChefModeratorStaff MemberSupporting Member

May 23, 2004
Columbia MO
Disclosures:
Staff Reviewer; Bass Gear Magazine
In terms of ohms, that^^^^^^is totally wrong.

8. ThisBass

Aug 29, 2012
Germany
Appro 3 Ohm

Unlikely the "average" amount runs below 3 Ohm

9. two fingersYou tahkin 'uh me? Yeah, you. You tahkin 'uh me?Supporting Member

Feb 7, 2005
Eastern NC USA
10. B-stringGold Supporting Member

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

11. Kmonk

Oct 18, 2012
South Shore, Massachusetts
Disclosures:
Endorsing Artist: Fender, Spector, Ampeg, Curt Mangan Strings

12. ThisBass

Aug 29, 2012
Germany
but

SQRT(-1) = j [ohm]

13. B-stringGold Supporting Member

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

14. ThisBass

Aug 29, 2012
Germany
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.

15. ThisBass

Aug 29, 2012
Germany
That's right, but understanding Formulas is a very different animal

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

16. Chazinroch

Feb 2, 2003
Ontario N.Y.
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.

17. ThisBass

Aug 29, 2012
Germany
That's not wrong (theoretical) but does not reflect the behavior of a real terms 8 Ohm and 4 Ohm speaker.

18. ChefModeratorStaff MemberSupporting Member

May 23, 2004
Columbia MO
Disclosures:
Staff Reviewer; Bass Gear Magazine
No.
one 8ohm cab with one 4 ohm cab = 2.67 ohms, as has been said many times in this thread already.

19. B-stringGold Supporting Member

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.

20. ThisBass

Aug 29, 2012
Germany
That was meant to be a joke

21. B-stringGold Supporting Member

You forgot the