Speaker Phase/Polarity question
Thread Starter
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
Speaker Phase/Polarity question
This is for my Daily Driver...
I added a 600 Watt 4 channel amp. I noticed that the rear speakers (6x9) thump backwards during drum beats. I can actually feel with my fingers the speaker pulling back on a drum beat. Although The Polarity is correct according to the outputs of the amp and the inputs on the speaker, something is wrong. The phasing is fine. I have heard that it does not matter if polarity is reversed as long as the other speaker is the same hence in phase.
However...I think when listening to bass drums and hard hits a polarity reversal will hurt the sound compression. On hard hits speakers are compressing the air in the trunk and not in the cabin. Drum beats are not the same as Bass frequencies. A drum beat has a fast attack and slow decay. Bass is a sine wave.
Is it possible the speaker or amp is labeled incorrectly? Should I figure out the correct polarity of the speaker with a battery? I used to do this in the old days when I could not read the + and - on the speaker. Just tap the speaker leads to a battery and if the polarity is + to + on the battery it should make the cone pop out a little.
Opinions please..
I added a 600 Watt 4 channel amp. I noticed that the rear speakers (6x9) thump backwards during drum beats. I can actually feel with my fingers the speaker pulling back on a drum beat. Although The Polarity is correct according to the outputs of the amp and the inputs on the speaker, something is wrong. The phasing is fine. I have heard that it does not matter if polarity is reversed as long as the other speaker is the same hence in phase.
However...I think when listening to bass drums and hard hits a polarity reversal will hurt the sound compression. On hard hits speakers are compressing the air in the trunk and not in the cabin. Drum beats are not the same as Bass frequencies. A drum beat has a fast attack and slow decay. Bass is a sine wave.
Is it possible the speaker or amp is labeled incorrectly? Should I figure out the correct polarity of the speaker with a battery? I used to do this in the old days when I could not read the + and - on the speaker. Just tap the speaker leads to a battery and if the polarity is + to + on the battery it should make the cone pop out a little.
Opinions please..
Melting Slicks
Joined: Sep 2000
Posts: 2,756
Likes: 5
From: Satellite Beach, FL, USA
Re: Speaker Phase/Polarity question (chuckster)
A speaker cone will move out and in trying to follow a audio note. It would be very difficult to tell if one speaker was pushing it's cone out while another was pulling it's cone in with a single hand on one speaker at a time. You would have to feed a very low frequency signal to each and put a hand on each cone to tell if they are out of phase. Your ear can also tell if speakers are out of phase for very low frequencies.
You can use a D cell fed into a speaker cone to confirm polarity.
[Modified by 99HT, 3:48 PM 1/7/2002]
You can use a D cell fed into a speaker cone to confirm polarity.
[Modified by 99HT, 3:48 PM 1/7/2002]
Thread Starter
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
Re: Speaker Phase/Polarity question (99HT)
Thanks 99! I was hoping you'd reply.
In general I agree with you. But only with constant frequencies. I.e BASS. Bass is a nice sine wave. But a Drum beat depends upon the compression of air in front of it.
Look at it this way.
Let's say you have a 10" sub in a SEALED box. And then only play a Bass Drum beat through it.
With the proper polarity the speaker will pound outwardly only being held back by the foam surround.
If it pounds inwardly then the voice coil slams against the magnet and the cone is trying to compress the air inside the box.
If you played a flat 60hz bass note I don't think there is a mechanical or audible difference. But I really think thumps are different.
Maybe you can not HEAR a difference. But I am more concerned about FEELING a difference.
[Modified by chuckster, 3:23 PM 1/7/2002]
In general I agree with you. But only with constant frequencies. I.e BASS. Bass is a nice sine wave. But a Drum beat depends upon the compression of air in front of it.
Look at it this way.
Let's say you have a 10" sub in a SEALED box. And then only play a Bass Drum beat through it.
With the proper polarity the speaker will pound outwardly only being held back by the foam surround.
If it pounds inwardly then the voice coil slams against the magnet and the cone is trying to compress the air inside the box.
If you played a flat 60hz bass note I don't think there is a mechanical or audible difference. But I really think thumps are different.
Maybe you can not HEAR a difference. But I am more concerned about FEELING a difference.
[Modified by chuckster, 3:23 PM 1/7/2002]
Melting Slicks
Joined: Sep 2000
Posts: 2,756
Likes: 5
From: Satellite Beach, FL, USA
Re: Speaker Phase/Polarity question (chuckster)
A speaker is designed to try and move symetrically in and out. The audio fed to it should average out as being symetrical. If your speaker box is ported, then you would get an air pressure increase for both directions of cone movement. You would have to look at the audio signal with an oscilloscope to see how symetrical the audio really is. Every sound is made up of many summed sine waves. Only a pure tone of 0% distortion would consist of a single sine wave.
For a C5 Bose HU, the power amp is a balanced or bridged design. The speaker is not grounded. It is connected to two power amps, one fed out of phase from the other. The audio fed to both polarities of the speaker floats on a 6-7 volt DC level. You should see the audio swing around 6 volts. For an aftermarket power amp, the amp has a DC to DC converter that feeds the power amp with say + and - 40 volts. The speaker is normally grounded and you would see the audio swing + and - referenced to ground.
For a C5 Bose HU, the power amp is a balanced or bridged design. The speaker is not grounded. It is connected to two power amps, one fed out of phase from the other. The audio fed to both polarities of the speaker floats on a 6-7 volt DC level. You should see the audio swing around 6 volts. For an aftermarket power amp, the amp has a DC to DC converter that feeds the power amp with say + and - 40 volts. The speaker is normally grounded and you would see the audio swing + and - referenced to ground.
