Servo'd subwoofer

[Minerva]

When you tap on a typical woofer cone it makes a fairly boomy sound like a drum would. This servo system is no different when the amp is off. When the amp turns on, there is a slight click and the cone moves like it's leveling then it's perfectly still. If tapped on it makes no noise perhaps the sound of a finger tapping on a marble tile! It takes on a completely different character.

Anyone ever see this before?

 

[Rubycon]

You're not supposed to hit the cone! It is not a drum. STOP DOING THAT! 😛

 

[TechBoyJK]

Originally posted by: Minerva
When you tap on a typical woofer cone it makes a fairly boomy sound like a drum would. This servo system is no different when the amp is off. When the amp turns on, there is a slight click and the cone moves like it's leveling then it's perfectly still. If tapped on it makes no noise perhaps the sound of a finger tapping on a marble tile! It takes on a completely different character.

Anyone ever see this before?

seen it, yes. whats even cooler is when you turn the sub up really loud, and bounce quarters off the moving cone....

 

[Analog]

The woofer is being powered by an amp (of course). The back EMF you're creating by moving the voice coil is seen by the feedback control system as an error signal, and it will then try to compensate for that.

 

[IamElectro]

If it is a Velodyne the motion is being picked up by a accelerometer and as yellowfiero mentioned <i>a feedback control system sees this as an error in the signal, and it will then try to compensate for that. </i>

Just in case you did not know the cone is moved by a DC motor using a cam mechinism and not a standard voice coil.

 

[Tiamat]

Originally posted by: TechBoyJK

Originally posted by: Minerva
When you tap on a typical woofer cone it makes a fairly boomy sound like a drum would. This servo system is no different when the amp is off. When the amp turns on, there is a slight click and the cone moves like it's leveling then it's perfectly still. If tapped on it makes no noise perhaps the sound of a finger tapping on a marble tile! It takes on a completely different character.

Anyone ever see this before?

seen it, yes. whats even cooler is when you turn the sub up really loud, and bounce quarters off the moving cone....

You dont need high SPL to accomplish a moving cone. Try playing a 10hz sine wave at low volume and your subwoofer will respond. If your sub can handle it, play 16hz sine wave at 85dB and it will be able to move your clothes. 😛

 

[Triumph]

Servo'ed subwoofers? No voice coil? I've never heard of these. Discuss.

 

[Minerva]

It's a Velodyne model ULD-18 series two. The date on it is 11-10-1991.

It's a neat design in the electrical domain and looks like it could be copied to larger designs. The feedback is provided by a small piezoelectric transducer providing basic accelerometer functions. There is also a compression and gain circuit loop. The amp seems to control ballistics and excursion too. That's pretty impressive to me anyway. 🙂

 

[TechBoyJK]

Originally posted by: Tiamat

Originally posted by: TechBoyJK

Originally posted by: Minerva
When you tap on a typical woofer cone it makes a fairly boomy sound like a drum would. This servo system is no different when the amp is off. When the amp turns on, there is a slight click and the cone moves like it's leveling then it's perfectly still. If tapped on it makes no noise perhaps the sound of a finger tapping on a marble tile! It takes on a completely different character.

Anyone ever see this before?

seen it, yes. whats even cooler is when you turn the sub up really loud, and bounce quarters off the moving cone....

You dont need high SPL to accomplish a moving cone. Try playing a 10hz sine wave at low volume and your subwoofer will respond. If your sub can handle it, play 16hz sine wave at 85dB and it will be able to move your clothes. 😛

i probably came off as an ignorant with my last statement, but i know this... try 50hz at 145db on 4 12's (good ones too)......

 

[spacejamz]

Originally posted by: C6FT7
You're not supposed to hit the cone! It is not a drum. STOP DOING THAT! 😛

the oil from your fingertips is not conducive to the health of the speaker cone...

 

[TechBoyJK]

Originally posted by: Minerva
It's a Velodyne model ULD-18 series two. The date on it is 11-10-1991.

It's a neat design in the electrical domain and looks like it could be copied to larger designs. The feedback is provided by a small piezoelectric transducer providing basic accelerometer functions. There is also a compression and gain circuit loop. The amp seems to control ballistics and excursion too. That's pretty impressive to me anyway. 🙂

haha you sound like a smarty!

 

[Apex]

Originally posted by: Triumph
Servo'ed subwoofers? No voice coil? I've never heard of these. Discuss.

No, different thing.

These servos are band-aid fixes that Velodyne uses to control distortion (by limited output). Other companies use things like low distortion motor technology (ie. Adire's XBL2).

Using servos instead of voice coils is a great way to go, but costly:

http://www.servodrive.com/contrabass.html

 

[Crucial]

Originally posted by: TechBoyJK

Originally posted by: Minerva
It's a Velodyne model ULD-18 series two. The date on it is 11-10-1991.

It's a neat design in the electrical domain and looks like it could be copied to larger designs. The feedback is provided by a small piezoelectric transducer providing basic accelerometer functions. There is also a compression and gain circuit loop. The amp seems to control ballistics and excursion too. That's pretty impressive to me anyway. 🙂

haha you sound like a smarty!

And she's a girl! OMGWTFBBQ!!!11!!1!1ONE