Keith,
Thanks for the information. I think the woofer system you have is what would be called a "sealed isobaric".
It has been twentysomething years since I worked on an isobaric system. Basically, the inner woofer dances in sync with the outer woofer in an attempt to keep the pressure constant in that chamber between the two. "Isobaric" means "constant pressure". I did some measurements of an isobaric system years ago and my findings contradicted the conventional wisdom of how to model an isobaric system, but I won't bore you with the details.
Okay, in my opinion the inner woofer of an isobaric system should be rolled or else it mucks up the midrange. I do not know what order the rolloff should be, but either first order or fourth order make the most intuitive sense to me. In my homebrews, I used a first order rolloff on the inner woofer because that was much simpler to do.
There's a good chance that the discontinuity you hear is due to the inner woofer blaring away into the back of the main woofer. In my opinion, it would be a good idea to roll off the inner woofer above 80 Hz or so, and we'll try a first order network because that's probably the safest bet.
If you can by any chance come up with the model number of the woofer, that would be very valuable. Even just a physical description of the woofer would help.
If not, then we can "wing it" and use a 16 millihenry iron core inductor in series with the woofer (like a Madisound Sledgehammer), stabilizing the impedance with a SWAG zobel consisting of a 30 microfarad cap and a high-power 10 ohm resistor.
If you can come up with any identifying information on the woofer, or even just a physical description (cone material, phase plug, surround description, magnet description, frame description) I can hopefully make a more educated guess on the component values for the inner woofer's crossover.
Duke
Thanks for the information. I think the woofer system you have is what would be called a "sealed isobaric".
It has been twentysomething years since I worked on an isobaric system. Basically, the inner woofer dances in sync with the outer woofer in an attempt to keep the pressure constant in that chamber between the two. "Isobaric" means "constant pressure". I did some measurements of an isobaric system years ago and my findings contradicted the conventional wisdom of how to model an isobaric system, but I won't bore you with the details.
Okay, in my opinion the inner woofer of an isobaric system should be rolled or else it mucks up the midrange. I do not know what order the rolloff should be, but either first order or fourth order make the most intuitive sense to me. In my homebrews, I used a first order rolloff on the inner woofer because that was much simpler to do.
There's a good chance that the discontinuity you hear is due to the inner woofer blaring away into the back of the main woofer. In my opinion, it would be a good idea to roll off the inner woofer above 80 Hz or so, and we'll try a first order network because that's probably the safest bet.
If you can by any chance come up with the model number of the woofer, that would be very valuable. Even just a physical description of the woofer would help.
If not, then we can "wing it" and use a 16 millihenry iron core inductor in series with the woofer (like a Madisound Sledgehammer), stabilizing the impedance with a SWAG zobel consisting of a 30 microfarad cap and a high-power 10 ohm resistor.
If you can come up with any identifying information on the woofer, or even just a physical description (cone material, phase plug, surround description, magnet description, frame description) I can hopefully make a more educated guess on the component values for the inner woofer's crossover.
Duke