Motor Limited or Suspension Limited?

[ciaonzo 5,000+ posts]

Which do you prefer?

Click to read more...

 

[sundownz Pro Seller]

Motor limited... if the suspension is stopping the movement people tend to break the driver. I've even seen it done on lower motor force drivers like my E8s.

 

[T3mpest 10+ year member]

Motor limited... if the suspension is stopping the movement people tend to break the driver. I've even seen it done on lower motor force drivers like my E8s.

x2. I'd rather know that the driver simply can't move the suspension far enough to hurt it than to know i'm stretching the actual softparts.

 

[ciaonzo 5,000+ posts]

I'm on the fence with this one. I own both and like the attributes of each but you're right; from an abuse standpoint it's probably best to have a motor-limited design.

 

[Koon 10+ year member]

I'm on the fence with this one. I own both and like the attributes of each but you're right; from an abuse standpoint it's probably best to have a motor-limited design.

agreed

 

[audioholic 5,000+ posts]

If set up properly, it wont matter one bit which design your speakers are.

 

[ciaonzo 5,000+ posts]

If set up properly, it wont matter one bit which design your speakers are.

I concur. Do you have a preference?

 

[John_E_Janowitz 10+ year member]

In the ideal situation you want everything to limit approximately at the same time. No point in having a motor that has much more travel but can't be used due to suspension limits. No need for the motor to limit well before the suspension runs out either. Another important aspect is that the suspension and/or motor must limit before the physical clearances inside the driver. Many woofers still have the ability to bottom the coil on the back plate when driven to full extremes. This will typically damage the coil quite quickly.

I do a few things in the design. First, the suspension must limit before the physical clearances. The AV woofers as an example have 32mm physical clearance before the coil can hit the back plate. The suspension physically limits to about 30mm so unless you tear a spider, rip off the surround, or bend up the cone you can never physically bottom the coil.

The same drivers have around 18mm overhang with a thick top plate. This gives about 23mm Xmax where the BL has dropped to 70% of the rest value. At the 30mm suspension limits, Bl is under 50% of the rest value and suspension stiffness is from 4-10x the rest stiffness for the last few mm. As the BL drops and suspension increases in stiffness this is creating much more of a soft limit to the travel than just slamming into a dead stop. With this kind of a coil to gap ratio I like to have about 25% more physical travel on the suspension above and beyond the rated Xmax. In other motors you don't need nearly as much. For example, in an underhung driver the BL drops off extremely quickly requiring less physical clearance past xmax.

John

 

[ciaonzo 5,000+ posts]

I was hoping you might chime in, thank you John. I looking forward to owning a few of your drivers.

I brought this up because I'm noticing that many of the drivers I own are indeed suspension-limited and it got me thinking that if I were to go off on an SPL tangent, these would not be the best candidates from a reliability perspective. Eventually something will give, probably a spider or lead since these types won't allow for the coil to touch the back plate, and I won't be happy about it. Since most guys here seem to have a hand in the SPL sector I wanted to see if this was something that was factored in.