Lazy speaker...

[Ian Rogers]

I have a little niggle in my car...

The right front speaker appears quieter than the left, so much so it really gets on my nerves!!
If I give it a kick, ie.. turn the sound up rapidly, it is corrected, but only until I turn it off...

At first thought there was an issue with the amp in the radio, but during the last windy spell the car door was nearly ripped off, the check strap was broken, luckily that was the only damage.

When we replaced the check strap, we needed to remove the door speaker and tada... the speaker was back to normal.... I put it down to a bad connection...

Alas!! It's now worse than ever...

For those in the know "so to speak"... can speakers become lazy... Is there something I can do.

I will, in the next few days, swap the speakers left to right... But as they are pop riveted in, I'll have to do it at work.

 

[misterT]

I will, in the next few days, swap the speakers left to right... But as they are pop riveted in, I'll have to do it at work.

Maybe you can just swap the connections at the amplifier end and see if the left speaker becomes "lazy".

 

[MikeMl]

Piece of metallic crap between the speaker's voice coil and the magnet? Usually means you toss the speaker and replace it.

 

[Ian Rogers]

Piece of metallic crap between the speaker's voice coil and the magnet? Usually means you toss the speaker and replace it.

I thought so.... I had the chance of two brand new speakers last week, chance gone by now.... I'll order two up..

Cheers mike..

 

[Ian Rogers]

Maybe you can just swap the connections at the amplifier end and see if the left speaker becomes "lazy".

Didn't really want to do this as the rear connectors are tiny... Me with my sausage like fingers will struggle.

 

[MrAl]

Hi there Ian,

Another possibility is frame warp. If the frame warps or becomes bent due to stress it can cause the voice coil to touch the sides of the magnet very slightly which could cause a dampening effect. And yes even the slightest amount of dirt or dust would cause it to appear to be intermittent. Moisture could also cause problems.

Connect the speaker to a relay so you can bang it with +12v and then -12v just before you turn the radio on

In other words, good luck with replacing it.

 

[misterT]

Connect the speaker to a relay so you can bang it with +12v and then -12v just before you turn the radio on

I'm very suspicious about that method.. One wrong move and there is huge DC current through the coil.

 

[Ian Rogers]

Hi there Ian,


Connect the speaker to a relay so you can bang it with +12v and then -12v just before you turn the radio on

Its easier to do what I'm doing now.... I blast the speaker by excessive volume for a split second...

Interesting about the frame being warped.... I can check that out first...

 

[picbits]

Double check the contacts in the door to chassis plugs if it has them - often you can get a bit of moisture in which corrodes the contacts.

I've seen a few cars in the past where the terminals had gone green .......

 

[Ian Rogers]

Double check the contacts in the door to chassis plugs if it has them - often you can get a bit of moisture in which corrodes the contacts.

I've seen a few cars in the past where the terminals had gone green .......

This is why it probably worked for a spell after the repair..... When I pull it apart I might solder the wiring together...

 

[audioguru]

I have a home speaker that spent many years in the humid basement. The flexy wires to the woofer voice coil corroded away until they were intermittent then they became permanently open.

I think the bass sounds were reduced when the flexy wires were corroded but were still working a little.

Car speakers also endure severe humidity/corrosion.

 

[dr pepper]

Had the same in my punto, swapped the speakers in the front, no change, then hard wired the r/h speaker direct to the radio, problem solved.

As per my issue the r/h (in the uk) is most likely to fail as the cables flex every time the door opens/closes, yours being the left hand might be a dead or dying speaker, if you change it and it hasnt allready got one make a drip shield and cover the top half of the speaker to protect it from deluge.

 

[Ian Rogers]

Had the same in my punto, swapped the speakers in the front, no change, then hard wired the r/h speaker direct to the radio, problem solved.

As per my issue the r/h (in the uk) is most likely to fail as the cables flex every time the door opens/closes, yours being the left hand might be a dead or dying speaker, if you change it and it hasnt allready got one make a drip shield and cover the top half of the speaker to protect it from deluge.

I am in the UK.... Right near you!!!

Sounds more and more like the problem.... I think now as you do...

First I'll make sure the speaker is mounted flat and not flexing
Then I'll rewire through the car door conduit...
The speaker already has a plastic drip shield ( Quite a relatively new car ) so I think that will be okay.

All else fails..... Sell it and get a another one ( Cripes!!! a bit drastic )

 

[MrAl]

I'm very suspicious about that method.. One wrong move and there is huge DC current through the coil.

Hi misterT and Ian,

misterT:
I was half joking there, but you know these speakers today have a very high power rating and 8 ohm coil and can take 12v if they are rated high enough. We're only talking around 20 watts here so it should not harm the speaker. Ive seen many speakers today rated much higher than that too, even for the automobile.

Ian:
Oh yes a high resistance between the radio and speaker could easily cause that problem. I'd check the resistance in Ohms to see what it is and if it changes with vibration.

 

[dr pepper]

Car speakers are usually 4 ohms, so they can get good power out of them from 12v without resorting to an inverter power supply within the radio.

 

[misterT]

misterT:
I was half joking there, but you know these speakers today have a very high power rating and 8 ohm coil and can take 12v if they are rated high enough.

I know.. I know what you mean.. but isn't the rating (8 or 4 ohms) just for some average AC (audio) frequency? if you put DC through it, it is a whole different thing..

 

[audioguru]

Ordinary car radios use bridged output amplifiers that almost double the voltage swing compared to an ordinary amplifier. The car battery is about 13.8V and the amplifier output at clipping is about 21.6V peak-to-peak. Then the power into 4 ohms is 14.6W RMS and into 8 ohms is about 8W per channel.

A speaker should NEVER have DC in it.

 

[MrAl]

I know.. I know what you mean.. but isn't the rating (8 or 4 ohms) just for some average AC (audio) frequency? if you put DC through it, it is a whole different thing..

Hello misterT,

Well, as an exercise to see how this works you can calculate the total impedance of an inductor in series with an (say) 8 ohm resistor. See what size inductor it takes to get a significant increase over the 8 ohms resistive at 30Hz.
Simpler yet, measure the speaker with an Ohm meter. Any ohm meter puts dc through the speaker.

The reason we dont want DC in a speaker under normal conditions is so that during the normal audio we dont want the speaker cone physically biased either in or out or else we can not get the full travel required at high volume. If the speaker normally goes out 1/2 inch and in 1/2 inch from rest position, if we bias it to 1/4 inch out with some DC then that means we only have 1/4 inch left in the 'out' direction. Even though we now have more room to move 'in', it doesnt help because the normal movement is only 1/2 inch 'in' so that means the cone tries to move from 1/4 inch to 3/4 inch and then back to 0 and then inward to -1/4 inch instead of -1/2 inch.
Of course there would also be distortion now that there is very unsymmetrical movement.

You've never biased a speaker with DC to see what would happen? You can also use them as positioning devices for a small apparatus.

 

[audioguru]

A speaker is a spring that resonates at a fairly low frequency. The enclosure might be sealed then it raises the resonant frequency.
The impedance is increased at the resonant frequency to maybe 60 ohms. Above the resonant frequency the impedance drops to a minimum at about 400Hz where its impedance of the speaker is rated then the inductance of the speaker causes its impedance to rise at higher frequencies.

An 8 ohm speaker is 8 ohms at about 400Hz but measures 6 ohms to 7 ohms on a DC ohm-meter.

 

[misterT]

Hello misterT,

Well, as an exercise to see how this works you can calculate the total impedance of an inductor in series with an (say) 8 ohm resistor. See what size inductor it takes to get a significant increase over the 8 ohms resistive at 30Hz.
Simpler yet, measure the speaker with an Ohm meter. Any ohm meter puts dc through the speaker.

The reason we dont want DC in a speaker under normal conditions is so that during the normal audio we dont want the speaker cone physically biased either in or out or else we can not get the full travel required at high volume. If the speaker normally goes out 1/2 inch and in 1/2 inch from rest position, if we bias it to 1/4 inch out with some DC then that means we only have 1/4 inch left in the 'out' direction. Even though we now have more room to move 'in', it doesnt help because the normal movement is only 1/2 inch 'in' so that means the cone tries to move from 1/4 inch to 3/4 inch and then back to 0 and then inward to -1/4 inch instead of -1/2 inch.
Of course there would also be distortion now that there is very unsymmetrical movement.

You've never biased a speaker with DC to see what would happen? You can also use them as positioning devices for a small apparatus.

We played with speakers enough about 10 years ago. When I worked at an amateur tv-station.. **broken link removed**
Skip to half-way of the video to see the silly thing go.. Well.. it is pretty stupid thing to do anyway and we did not have a high-speed camera.