Go Back   Team-BHP > Under the Hood > In-Car Entertainment


Reply
 
Thread Tools Search this Thread
Old 20th October 2008, 07:31   #1
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,839
Thanked: 1,318 Times
Default Using a multimeter to diagnose speakers wired in the wrong phase?

As the thread title suggests, The following was suggested by a guy in an orkut forum when someone complained about "less bass effect" in his car after an install.
Quote:
It may be possible that the wiring is reversed, or may be the EQ is not yet set properly to meet the high bass.

Have you set the EQ as per Bass or have you set it normal/flat?

Try one thing,
if you have a multi-meter (the digital meter used to check voltage, ampere)
Check the resistance of the speakers when the wires are plugged out and also when the wires are plugged in. If the resistance when wires are plugged in is at least 4 times than that when plugged out, then the matter is of EQ. And if the resistance is less than its the matter of wiring.

Eg of readings:

Condition 1 wires attached, condition 2 wires removed.

e.g. 1

1) 40 Ohm

2) 150 Ohm or less

Then there is the issue of wiring.

e.g. 2

1) 40 Ohm

2) 165 Ohm or more

There is the issue of EQ.

For e.g. 1, get the wire terminal positioning check.
For e.g. 2 change the EQ in your HU.
I know about electronics and speakers, but i cant imagine how this works. I asked the guy for a clarification, and this is what he said
Quote:
the resistance matter is, if the terminals are set properly, there would be enough resistance.
And if we connect the wires, the resistance decreases. If the wires are connected in forward series i.e. correct way, resistance decreases a lot. But if they are in reverse series, the resistance decrreases but less than 75% of total i.e. between 25 to 70. This helps in determining the phase as forward or reverse. Thats just an electric resistance calculation method. And if you get equal resistance in all conditions, it is because the capacitors connected on both the sides, (HU and speakers) are not of requires farads and are non-polarized.
Still cant figure out what he's trying to say. Can anyone explain
greenhorn is offline   Reply With Quote
Old 20th October 2008, 09:20   #2
Senior - BHPian
 
clevermax's Avatar
 
Join Date: Jun 2006
Location: Tvm/Amsterdam
Posts: 1,601
Thanked: 404 Times
Default

May be it will work out fine or the whole exercise is a waste of time. Anyway that guy has not explained it in a scientific way. Looks more like a guy in the local electronic repair shop is talking. and AFAIK, neither a speaker's terminals nor the output of the amplifier has polarity specifications, since the output is an electrical waveform corresponding to the sound it should reproduce and it contains positive and negative peaks. Correct me if I am wrong.
clevermax is offline   Reply With Quote
Old 20th October 2008, 09:50   #3
BHPian
 
Join Date: Mar 2005
Location: goa
Posts: 981
Thanked: 43 Times
Default

There should be a polarity difference, but i am not aware of the resistance aspect.
filcord is offline   Reply With Quote
Old 20th October 2008, 10:14   #4
Senior - BHPian
 
Join Date: Jul 2004
Location: Madurai
Posts: 1,006
Thanked: 645 Times
Default

Of course there are polarity specifications in the speaker input as well as amplifier output.
jyobeb is offline   Reply With Quote
Old 20th October 2008, 10:27   #5
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,839
Thanked: 1,318 Times
Default

I dont think the resistance will change with direction or phase. Impedance, possibly, but resistance is what we're measuring with a multimeter. Again, capacitors having different resistance based on polarity, I'm not entirely sure, since the DMM is measuring DC resistance and a polarized electrolytic cap may have different resistances in different directions, but still that should be an issue since the woofer is placed in parallel with the cap and tweeter, so the 4 ohms of the woofer should dominate.

Its not that don't I understand electronics and needed an explaination. I know my way fairly well around them, its just that I cant make sense of what's written above.
I was planning to say he was an idiot without a clue , but i wanted to give him the benefit of the doubt, and wanted to see if there was some truth to his jugaad.

Last edited by greenhorn : 20th October 2008 at 10:30.
greenhorn is offline   Reply With Quote
Old 20th October 2008, 10:52   #6
Team-BHP Support
 
navin's Avatar
 
Join Date: Mar 2004
Location: mumbai
Posts: 22,509
Thanked: 3,885 Times
Default

Quote:
Originally Posted by greenhorn View Post
As the thread title suggests, The following was suggested by a guy in an... Still cant figure out what he's trying to say. Can anyone explain
I have no idea what he is saying. A speaker's nominal impedance is 4 ohms why is he refering to 40ohms or 150 ohms?
navin is offline   Reply With Quote
Old 20th October 2008, 10:59   #7
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,839
Thanked: 1,318 Times
Default

I guess my hunch was right. He's clueless. forget this then, will ask him to get a clue first
greenhorn is offline   Reply With Quote
Old 20th October 2008, 11:04   #8
Senior - BHPian
 
Join Date: Mar 2006
Location: Faridabad
Posts: 6,814
Thanked: 294 Times
Default

For phase check I have burned a cd with a track with no change and one with one channel out of phase. I play it and check for the output with both the track and take action on the same as required.
low_bass_makker is offline   Reply With Quote
Old 20th October 2008, 11:06   #9
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by greenhorn View Post
I was planning to say he was an idiot without a clue
I tend to go with this!
Even if there is merit to what he has in his mind, he is utterly unable to express it, which basically means zilch.
anupmathur is online now   Reply With Quote
Old 20th October 2008, 11:27   #10
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,839
Thanked: 1,318 Times
Default

What i usually do is shift balance to either 100% front or back, and then change balance from 100% left to 100% right. if there is a smooth increase till balance is 0, with a good centre image, then phase should be correct, On the other hand , if phase is wrong , then the music sounds like its coming from beyond the speakers , and as i change the balance, at one point, the image shifts abruptly from one extremity to the other, and the bass generally feels weak

usually its the bass feeling weak after a service which triggers the hunt for the correct phase in the first place

Last edited by greenhorn : 20th October 2008 at 11:29.
greenhorn is offline   Reply With Quote
Old 20th October 2008, 14:35   #11
Distinguished - BHPian
 
phamilyman's Avatar
 
Join Date: Jul 2007
Location: Gurgaon
Posts: 5,601
Thanked: 3,452 Times
Default

LBm ji, if its not a trade secret can you share even a minor snippet on the filesharing site.
phamilyman is offline   Reply With Quote
Old 20th October 2008, 15:00   #12
Team-BHP Support
 
navin's Avatar
 
Join Date: Mar 2004
Location: mumbai
Posts: 22,509
Thanked: 3,885 Times
Default

Quote:
Originally Posted by low_bass_makker View Post
For phase check I have burned a cd with a track with no change and one with one channel out of phase
Geez, LBM you are really particular. I just listen to old Beatles recordings, stuff I know so well that my ears pick up all the cues. With music one is familiar with ears can pick up a whole host of cues (incl balance, phase, tone, etc..). Music is a sum of parts and I find it easier to decode a sum of parts that each part seperately.
navin is offline   Reply With Quote
Old 20th October 2008, 16:15   #13
Senior - BHPian
 
DerAlte's Avatar
 
Join Date: Mar 2007
Location: Bangalore
Posts: 8,076
Thanked: 2,876 Times
Default

Oy greenie, does this person have any thing to do with your mishap? Like you trying to figure out while driving what he has written?

Has the good old "battery test" fallen out of favour?
DerAlte is offline   Reply With Quote
Old 20th October 2008, 16:17   #14
BHPian
 
valhallen.282's Avatar
 
Join Date: Aug 2008
Location: Bangalore
Posts: 317
Thanked: 131 Times
Default

I go with what LBM says i either do that or best colour code the wires. saves a lot of time and money. if you ask how thats simple i just put coloured tape to each end. so no matter how many mistakes the guy makes after service its always easy to correct.
valhallen.282 is offline   Reply With Quote
Old 20th October 2008, 17:15   #15
BHPian
 
Join Date: Jun 2007
Location: Pune
Posts: 268
Thanked: 10 Times
Default

Quote:
Originally Posted by navin View Post
I have no idea what he is saying. A speaker's nominal impedance is 4 ohms why is he refering to 40ohms or 150 ohms?
Quote:
Originally Posted by anupmathur View Post
I tend to go with this!
Even if there is merit to what he has in his mind, he is utterly unable to express it, which basically means zilch.
Additionally he might be having a faulty multimeter or defective piece of wire.
omishra is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wired.com Article on Part Failure, Testing & Reliability zosoin Technical Stuff 6 25th October 2012 16:30
Help me diagnose the problem in Palio 1.2 ELX extreme_torque Technical Stuff 45 18th December 2009 12:01
Fabia stalling issue: Dealer unable to diagnose. EDIT: Skoda agrees to replace car mayank123 Indian Car Dealerships 24 16th September 2009 13:41
Difficult to diagnose noise from Santro dj_2006 Technical Stuff 2 2nd July 2007 23:28


All times are GMT +5.5. The time now is 06:03.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks