E90Post
 


VIBE Motorsports
 
BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > 2 ohm vs 4 ohm



Reply
 
Thread Tools Search this Thread
      06-05-2006, 09:43 AM   #1
longhorn35
Longhorn Fanatic
 
longhorn35's Avatar
 
Drives: 2009 328i Sedan
Join Date: May 2006
Location: McKinney, Texas

Posts: 50
iTrader: (0)

2 ohm vs 4 ohm

Do the HIFI and Logic Seven have 4 Ohm subs under the seats? I am reading the spces and it looks like they are 2 ohm?

Forgive my lack of understanding of Ohm-age but what will happen if I put 4 Ohm speakers on a 2 Ohm connection?
longhorn35 is offline   United_States
0
Reply With Quote
      06-05-2006, 11:23 AM   #2
AskNiko
Private
 
AskNiko's Avatar
 
Drives: E90 325i + 4Runner
Join Date: Mar 2005
Location: Honolulu

Posts: 86
iTrader: (0)

Garage List
06 325i  [0.00]
Quote:
Originally Posted by longhorn35
Do the HIFI and Logic Seven have 4 Ohm subs under the seats? I am reading the spces and it looks like they are 2 ohm?

Forgive my lack of understanding of Ohm-age but what will happen if I put 4 Ohm speakers on a 2 Ohm connection?
R = resistance in ohms
V = 12 volts
I = current in amps


Ohms Law:
R = V/I
I = V/R

For 2 ohms
I = 12/2 = 6 amps

For 4 ohms
I = 12/4 = 3 amps

Therefore, if you use 4 ohms, you will not get the max-current (amps) a.k.a umph !

I think this is right, it has been 12 years since I graduated from engineering school.
__________________


|U.S. Spec. 325i | 6 Spd. Manual | Titanium Silver | Black Leatherette | Aluminum Trim | Sports Package | Xenons | Sat. Prep. |
AskNiko is offline   United_States
0
Reply With Quote
      06-05-2006, 11:29 AM   #3
longhorn35
Longhorn Fanatic
 
longhorn35's Avatar
 
Drives: 2009 328i Sedan
Join Date: May 2006
Location: McKinney, Texas

Posts: 50
iTrader: (0)

Quote:
Originally Posted by AskNiko
R = resistance in ohms
V = 12 volts
I = current in amps


Ohms Law:
R = V/I
I = V/R

For 2 ohms
I = 12/2 = 6 amps

For 4 ohms
I = 12/4 = 3 amps

Therefore, if you use 4 ohms, you will not get the max-current (amps) a.k.a umph !

I think this is right, it has been 12 years since I graduated from engineering school.
So to get max current, will I need to get additional wattage from another amp source?
longhorn35 is offline   United_States
0
Reply With Quote
      06-05-2006, 11:46 AM   #4
Ghunger
Major
 
Ghunger's Avatar
 
Drives: 330i
Join Date: Sep 2005
Location: Seattle, WA

Posts: 1,025
iTrader: (0)

The connection doesn't determine the resistance the speaker does. If you connect a 4 ohm speaker to an amp that's rated at lets say 400 amps @ 2ohms you'll get 200 amps running the speaker given that the voltage is the same. This is why high end amps that can operate reliabily at lower resistances are so desireable. You can wire speakers in parallel, lower the resistance, and effectively get a great deal more amperage to run your speakers. The problem comes when you connect say a 2 ohm load to an amp that only rated to be stable at 4 ohms in which case you could damage the amp. I hope I got all that right and I hope it helps. As far as what resistance the speakers are and how they're wired? I think there was a thread earlier where E90Fleet posted the speaker specs. Try a search. I have no idea on how they're wired though.
__________________

330i Monaco Blue, Terra /w aluminum trim, SP, PP, CA, PDC, Nav, Folding Seats, Sat Prep
European Delivery Blog
Picture Gallery
Ghunger is offline   United_States
0
Reply With Quote
      06-05-2006, 11:48 AM   #5
AskNiko
Private
 
AskNiko's Avatar
 
Drives: E90 325i + 4Runner
Join Date: Mar 2005
Location: Honolulu

Posts: 86
iTrader: (0)

Garage List
06 325i  [0.00]
Quote:
Originally Posted by longhorn35
So to get max current, will I need to get additional wattage from another amp source?
To optimize, use 2 ohm speakers.

Sounds like the this is already at speaker level so it is not good to amplify at that stage because you will also amplify the noise.

If you want to amplify, get it from signal level, then amplify. Results should be cleaner.

To keep it simple, just use 2 ohm speakers as the specs say.
__________________


|U.S. Spec. 325i | 6 Spd. Manual | Titanium Silver | Black Leatherette | Aluminum Trim | Sports Package | Xenons | Sat. Prep. |
AskNiko is offline   United_States
0
Reply With Quote
      06-05-2006, 11:50 AM   #6
longhorn35
Longhorn Fanatic
 
longhorn35's Avatar
 
Drives: 2009 328i Sedan
Join Date: May 2006
Location: McKinney, Texas

Posts: 50
iTrader: (0)

Quote:
Originally Posted by AskNiko
To optimize, use 2 ohm speakers.

Sounds like the this is already at speaker level so it is not good to amplify at that stage because you will also amplify the noise.

If you want to amplify, get it from signal level, then amplify. Results should be cleaner.

To keep it simple, just use 2 ohm speakers as the specs say.

Where can you find 8" subs that are 2 Ohm?
longhorn35 is offline   United_States
0
Reply With Quote
      06-05-2006, 02:09 PM   #7
AskNiko
Private
 
AskNiko's Avatar
 
Drives: E90 325i + 4Runner
Join Date: Mar 2005
Location: Honolulu

Posts: 86
iTrader: (0)

Garage List
06 325i  [0.00]
Quote:
Originally Posted by longhorn35
Where can you find 8" subs that are 2 Ohm?

This post might answer your questions...

http://www.e90post.com/forums/showthread.php?t=19036
__________________


|U.S. Spec. 325i | 6 Spd. Manual | Titanium Silver | Black Leatherette | Aluminum Trim | Sports Package | Xenons | Sat. Prep. |
AskNiko is offline   United_States
0
Reply With Quote
      06-05-2006, 08:53 PM   #8
ScotyH
Bimmer me up
 
Drives: 08 M3, 2010 GTR
Join Date: Sep 2005
Location: Edmonton,AB

Posts: 341
iTrader: (0)

The factory HiFi subs are 2 ohm. I just finshed a system that utilizes them. They actually can produce some substatial soun.
ScotyH is offline  
0
Reply With Quote
Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 06:31 AM.




e90post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST