DIY sub

[WmAx]

In the model it was reccomended to use low insert. In the driver manual for volume of 3 cubic feet it is reccomended to use the mid insert. Which way should I Go?

The mid-Q insert in a ported alignment of 3-4 cubic feet will offer maximum overall benefits for the 12VQ subwoofer.

-Chris

 

[haraldo]

Still planning to make my sub. I am looking at a rythmik 12" servo subwoofer kit as an alternative to the Dayton driver and amp. Is there an advantage to a servo sub?

I have heard some claims that the servo in theory should improve the sub's but in reality in some cases just makes them slower and not able to "follow" very fast speakers.

I can't say that it's true, the previous statement is just forwarding opinions from Richard Hardesty, author of Audioperfectionist.
I have not set out to find the difference myself, however, there may always be differences between the theory and what's best in practice....

From a physics point of wiew I believe it would be better to prevent an errorfrom happening, rather than correcting afterwards. The servo is actually trying to correct errors that's already happened, which means it will always lag behind......

This is very hard, but to really find out I guess you should just go out there and listen.........

regards

Harald N

 

[BassThatHz]

When ever you have extra circuitry in the path it slows the signal a bit, that's why a High-Gain feedback is needed. If the driver is of a good design, kept within normal op range and given enough input power the need for a servo is not so much. It makes sense in a sealed design because the air acts like a spring with a (linear?) pressure increase. A servo might not work so well in a ported design because the driver is acted upon by some of the built up pressures in the port area, which is dependant on the frequency, tune and playback volume... like a spring that changes tension intermittently I guess.

 

[TLS Guy]

When ever you have extra circuitry in the path it slows the signal a bit, that's why a High-Gain feedback is needed. If the driver is of a good design, kept within normal op range and given enough input power the need for a servo is not so much. It makes sense in a sealed design because the air acts like a spring with a (linear?) pressure increase. A servo might not work so well in a ported design because the driver is acted upon by some of the built up pressures in the port area, which is dependant on the frequency, tune and playback volume... like a spring that changes tension intermittently I guess.

A servo does not slow anything down. What a serve is, among other things, is a form of equalization. It is a form though that adds EQ with negative feedback so in theory just the right EQ is added at all times. Now to all intense and purposes you can only add EQ to a sealed enclosure, because in a ported enclosure the driver decouples below F3 in a hurry. A servo is dumb, and the driver will bottom in a hurry. In other words at system resonance, when most of the sound is coming from the port, the cone practically stops still as the pressure is so high. Then decoupling takes place which is why it as a good idea to have a filter below F3.

Servo systems are all about getting a quart from a pint pot. The servo driven speaker will be handling higher power, have greater thermal compression and bottom the driver at a lower spl, than the same driver in an optimal sealed box without servo. However the F3 point of the servo system will likely be lower.

 

[haraldo]

A servo does not slow anything down. What a serve is, among other things, is a form of equalization. It is a form though that adds EQ with negative feedback so in theory just the right EQ is added at all times. Now to all intense and purposes you can only add EQ to a sealed enclosure, because in a ported enclosure the driver decouples below F3 in a hurry. A servo is dumb, and the driver will bottom in a hurry. In other words at system resonance, when most of the sound is coming from the port, the cone practically stops still as the pressure is so high. Then decoupling takes place which is why it as a good idea to have a filter below F3.

Servo systems are all about getting a quart from a pint pot. The servo driven speaker will be handling higher power, have greater thermal compression and bottom the driver at a lower spl, than the same driver in an optimal sealed box without servo. However the F3 point of the servo system will likely be lower.

Perhaps you could compare this to negative feedback in an amplifier. If it's done properly and with great care it works beautifully. If you have to apply too much of it, because of poor design, then it doesn't work at all.... But then again you have a flawed design in the first place if you need too much correction.

-H