Bingo, that's what I was suggesting too, look at the impedance plot of your driver (bare) and in the enclosure. Any new peaks in the impedance compared to the bare driver plot are added by the box.
Damping can get you closer to your desired FR plot. I personally use fiberglass insulation and real wool felt (for lining the walls) but the impedance plot was telling me what to use. Twaron's angel hair is something special in that regard. It behaves a bit different from fiberglass and is excellent for midrange(*). Not cheap though.
As I was trying to find a recipe for the entire bandwidth fiberglass was hard to beat. It was the only one that worked very good in the entire spectrum. Even better with the wool felt, which I also used as a guard behind the driver to keep the fiberglass away from the driver's vent.
Here's an impedance test from my test enclosure with a couple of different combinations:
And another one showing driver alone on baffle, driver in empty box and driver in box damped with fiberglass and wool felt:
(*) You can use less of it for the same amount of damping fiberglass brings...
What kind of driver were you using? Fb close to 200 seems very high for a true woofer. Did you also note the change in box Q at your different measurements?
In a closed box, both Fb and Q can be reduced with the use of a good stuffing material. FG seems to give the best results. However, there is a limit to the effect with any stuffing material. I have not seen any formal studies that included Teijin Twaron. I used to use that fiber to make nonwovers on a special paper machine.
FG dia. around 5 uM not packed too tightly is my rule of thumb. That equates to about 450g/28L or, 1 lb / cu. ft.
True, not a woofer, even if it's doing woofer duty for me with 25 pieces a side it's still a fullrange.
Yes, different damping materials had a slightly different effect. For a woofer fiberglass seems a good choice, as that does push the impedance peak down in frequency.
I've seen some measurements on Twaron's angel hair and combinations with fiberglass. I'd guess that Twaron's material could do very well for midranges with less needed for the same effects as fiberglass. This was a test enclosure to get a working recipe for my line arrays: thread here...
It worked very well with the total array of 25 driver's impedance mimicking a single driver:
(with a bit lower total Fb.)
Yes, different damping materials had a slightly different effect. For a woofer fiberglass seems a good choice, as that does push the impedance peak down in frequency.
I've seen some measurements on Twaron's angel hair and combinations with fiberglass. I'd guess that Twaron's material could do very well for midranges with less needed for the same effects as fiberglass. This was a test enclosure to get a working recipe for my line arrays: thread here...
It worked very well with the total array of 25 driver's impedance mimicking a single driver:
(with a bit lower total Fb.)
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