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In Reply to: RE: Crossover upgrade for Tympani IVa posted by SteveJewels on January 18, 2021 at 13:11:46
Here is the stock T-IVa XO schematic:
As you can see from the FR:
... it could do with a bit of tweaking, for a smoother FR. :-))
I would suggest a better SQ will be achieved by:
1. combining the internal & external XO sections into 1 external box, allowing you to remove the ribbon HP filter from the 'embrace' of the 75uF cap in the external XO.
2. minor adjustment of the roll-off points, to achieve a smoother overall FR.
This leads to the following XO schematic:
Having this FR:
Choose the best components you can afford for the passive filters - eg.:
* 12g ribbon inductors
* good film caps - eg. Jupiter.
Unfortunately, though, doing this doesn't allow you to get rid of the level difference between the bass panels and the mids & ribbons.
The only way you can do this is by replacing the external passive XO with an active XO and using one amp on your bass panels and another on your mids & ribbons.
This would give you the following FR:
I'm building new crossovers for the Tympani IVa's. The images you posted above are too small to be completely legible. Could you post the crossover schematics in larger format?
Send me your email address and I can send you some better pics than the format I am allowed to use on the Asylum.
Andy, is it not the electrical response of the crossover you show us? I think you have forgotten the series resistor for the 2 Ohm ribbon tweeter. If you run without it, there will be an increased level of the tweeter and it may also be hard for some power amplifiers to drive that load.
Please note, that if you separate the two coils, it will change the transfer characteristic somewhat.
The acoustic response is more linear, see below. I think the peak around 1 kHz need to be tweaked.
Sure, Roger, it's the electrical response of the crossover I showed (the output from lspCAD).
There was no 1 ohm series resistor on the ribbons, in the T-IVa mid/ribbon panels that I bought for my 'Frankenpans'.
In my 3-way active Maggies, I used a ribbon amp that could cope with 2 ohms. (Now I have swapped them for 3 ohm ribbons, this amp has an easier time of it! :-)) )
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