Subwoofer building results - MTX 9500 4in motor rebuilt as an 18"

[nate0]

I have a question for anyone able to or interested in answering. I have attempted twice to rebuild an MTX 9515 motor (4in coil) into an 18 using an 18" TI basket. Both times I have yielded good Fs of around 30, but the electrical Q and total Q I am unable to get down low enough for myself or where I would like them. I suspect one of several reasons. I chose to use a coil that is not the original MTX coil but the ID and OD are a match. The winding height is more by about 1/2in. Would the overall mass have any bearing on the electrical Q? My suspicion is the motor originally was not engineered for a larger cone/mass. Any thoughts on this? Maybe I can attempt a third top assembly and keep the Mass at or around 400g? Should I try to use an original or oem MTX 9500 4" coil?

thanks.

[dynamo]

If the coil fills the gap as well as the original, I would look electrically at:

1) longer coil is wasting energy outside the gap causing less energy focused in the gap?

2) is the new coil round wire vs flat, resulting in less winding in the gap?

[nate0]

If the coil fills the gap as well as the original, I would look electrically at:

1) longer coil is wasting energy outside the gap causing less energy focused in the gap?

2) is the new coil round wire vs flat, resulting in less winding in the gap?

Ok understood. Thanks.