To continue with Harbinger project i would like to investigate the drivers and what could be expected from them. I already mentioned two of the 15 inchers and that i decided to use a version of 8512F.
The motor on this driver is very strong 220mm in diameter, noiseless vent and T-shaped central pole piece for symmetric field in gap as seen below.
The original had this set of parameters:
This results in the following equivalent electrical components:
Lces -> corresponds to Cms; Cmes -> corresponds to Mms; Res -> corresponds to Rms
First modification was changing the suspension system with a more softer one. The new spider has larger deeper and fewer corrugations. I made this modification so that the woofer can perform better at lower input power.
The replacement spider i used before for a 10 inch driver modification to fit in a 4″ voice coil.
At this point i needed to build a new box to put in the woofer and study it’s behavior. I built a 160 Liters vented box with 2 ports each of 72mm diameter and 140mm length.
After placing the driver in the box i ran impedance test and simulation of the model created with the spreadsheet from Electric Equivalent Model of Loudspeakers article. As you can see the model is very close to the measured result.
The box wasn’t well braced and needed some strengthening but the output in the bass region was satisfactory. Even at low levels the bass was low with a good amount of punch. My room helps a lot though on the low end. I have wooden floors and ceiling and lots of furniture.
In the next article we will look at what else can be improved on the drivers and the box.
Thank you for visiting,