https://ln271828.net/budget_3-way.htm
Wharfedale woofer
HiVi T20
PE 299-4212 mid with a plastic chrome dustcap
https://www.parts-express.com/03-0510-Speaker-299-4212?quantity=1
"
FIGURE 6
Now, we come to the solution of the aforementioned response peaks and dips. Note that two of these curves have no such peaks and dips and that has nothing to do with the gating process which removes room reflections by some 95% above 300hz.
The RED is midrange by itself without filters. The green is that of the midrange and tweeter only, with crossover filters, hence the drop below 600hz. The woofer was disconnected. The black curve is the whole system with crossover #5. the slight shift around 5khz is attributed to high frequency output from the woofer despite its second order 300hz low pass filter and possibly overall system impedance. Keep in mind that the three sections of the crossover do affect each other, however subtly.
OK, so where went the peaks and dips? Refer back to photo 7. The dustcap has been coated with RTV, an uncured rubber resembling toothpaste with an odor of vinegar. This cured some of the nasty high frequency stringency. Notice the narrow rubber strips of speaker gasket stuck to the cone circumference and the annulus.
These were added for the following reasons. The one attached to the cone was intended to dampen the cone. It was spiraled from the apex to the circumference with one revolution. It helped a little but the dip at 1300hz (fig 3) was still present, along with its THD component. It is known that frequency wavelengths and medium dimensions will interact. So, a similarity was investigated. It just so happens that the wavelength of 1300hz is 10.47" and the circumference of the cone at the annulus is 10.4". What is happening is that the annulus is resonating at 1300hz and the transverse wave along the cone is being reflected back into the cone, causing the dip in response. Dampening this resonance in the annulus cured the problem "
Wharfedale woofer
HiVi T20
PE 299-4212 mid with a plastic chrome dustcap
https://www.parts-express.com/03-0510-Speaker-299-4212?quantity=1
"
FIGURE 6
Now, we come to the solution of the aforementioned response peaks and dips. Note that two of these curves have no such peaks and dips and that has nothing to do with the gating process which removes room reflections by some 95% above 300hz.
The RED is midrange by itself without filters. The green is that of the midrange and tweeter only, with crossover filters, hence the drop below 600hz. The woofer was disconnected. The black curve is the whole system with crossover #5. the slight shift around 5khz is attributed to high frequency output from the woofer despite its second order 300hz low pass filter and possibly overall system impedance. Keep in mind that the three sections of the crossover do affect each other, however subtly.
OK, so where went the peaks and dips? Refer back to photo 7. The dustcap has been coated with RTV, an uncured rubber resembling toothpaste with an odor of vinegar. This cured some of the nasty high frequency stringency. Notice the narrow rubber strips of speaker gasket stuck to the cone circumference and the annulus.
These were added for the following reasons. The one attached to the cone was intended to dampen the cone. It was spiraled from the apex to the circumference with one revolution. It helped a little but the dip at 1300hz (fig 3) was still present, along with its THD component. It is known that frequency wavelengths and medium dimensions will interact. So, a similarity was investigated. It just so happens that the wavelength of 1300hz is 10.47" and the circumference of the cone at the annulus is 10.4". What is happening is that the annulus is resonating at 1300hz and the transverse wave along the cone is being reflected back into the cone, causing the dip in response. Dampening this resonance in the annulus cured the problem "
