Are notch filter calculators accurate?

[AllenB]

In this next one I took the 3.6/0.47 filter and compared output impedances. Red is Voltage source. Yellow is 3.5 ohms, and I also adjusted that response back up so that it is only appearing to show differences. The impedance of the speaker with and without the filter is also shown.

I didn't show the (likely) variation in the bass as I don't have the in box impedance.

 

[triode_al]

I was just curious how the 0.22 went against the 0.47mH. Shown here compared to no filter, both using 12 ohms. It looks as though they might be useful against the baffle step?

This is interesting!
I assume red = 0,47mH, yellow=0,22mH, blue=none

This shows it brings the 1 kHz area down into the same perspective as the area above;
initially Damde worked with .33mH.
while I expect the notch filter [LCR 21mH+8ohm+50muF) reduces the low frequencies.
Then everything would go in same pespective.

With a lowish (2 ohm) or high (15 ohm) output impedance, everything is different again for a filter+speaker.

 

[AllenB]

To the original I added 0.33mH in black, which seems to cut between them.

 

[AllenB]

However easing back to 3.6 ohms in the filter, the 0.33mH lets in a little more at 1kHz than the 0.47mH.

 

[AllenB]

while I expect the notch filter [LCR 21mH+8ohm+50muF) reduces the low frequencies.

Is this a series filter in parallel with the amp?

 

[triode_al]

Yes, parallel to speaker and between the + and - bars.
So a shortcut so to say.
In the dia of post #18 the most bottom dotted line that weavers between 4 and 6 ohms is the result with the heavy impedance correction in place from 150uF+8.2 ohm. Now that is a sort of shortcut. ..

I think I should measure my setup. 😕 I did it before with another speaker so I hope I will be able to do it again . .

 

[AllenB]

This shows the effect of the lower notch filter with 2 ohms source impedance and with 15 ohms. (I'm using the default response curve for the horn enclosure.)

 

[triode_al]

What really surprises me is that the box has such a great sound.

But I used to have an FE103Sigma in a TQWT box, that was great too, had no filter (was beginning 'eighties and at that time the baffle correction was not invented here yet, at least not in my scrapyard) 😱​

And that the high's sort of emerge like as if it is a coaxial speaker.

This means that the FE108, which has that three-point bonding of the cap, really is an innovation over the old one.​