a question for the filter specialists: which filter also lowers the lower frequencies as soon as the resonance comes in?
I really need to know which models have this property because I never want to hold my hands on a filter like this ever again.
can it be that it is the ladder filter and the curtis filter?
where the ladder filter is the famous moog filter, since i don’t have a moog i can’t imagine it having this annoying property
I would like to answer your question the other way around … maybe this is more practical.
There are lowpass filters, which don’t kill the low frequencies and their designers/manufactures explicitly point out that those filters will have a low frequency compensation at higher resonance settings.
thanks, but i think it’s better if i know the models because i don’t think there are many. I think it’s the curtis filter.
Yes, the Moog ladder filter does kill the bass when resonance is pushed.
oh, so does the filter 
would have liked to try the mother 32 at some point, but this characteristic of the filter is not for me.
Informative and very clear Reddit post about the reasons here: Reddit - Dive into anything
all the ssm2044 filters (sp-1200/korg monopoly, polysix/ppg wave 2.3, etc) i’ve used do this. following with interest
Problem is that many tried to copy the Moog filters, which kills the low frequencies.
doesn’t the A4 also have a ladder filter (the upper one)? I mean that was not the case here.
interesting, then it might even seem like a natural thing. but then still prefer the filter that compensate directly. because that can be really annoying.
yes, but the A4 can compensate by setting the second filter to highpass and boost the hell out of the low end 
having two filters at the start is always nicest anyway…
As @SoundRider touches on above, might be easiest rounding up the filters that do compensate.
If making a start, and do correct me anyone if wrong, but think the Polivoks style filter is known for this.
On the positive side, resonance can act as a tone control when filters have this property.
The Prophet rev 4’s two filters do behave in this manner and an optional compensation setting for this has been added in the latest beta firmware.
Other things to check out are how quickly resonance affects the lower frequencies and how filters which are unable to self-oscillate would behave in this regard.
if i understood this correctly, then it seems to be a natural process of an analogue filter that it rolls off the bass as soon as the resonance is driven in. and it is therefore not possible to say unequivocally which filters have it and which do not. so it might be better to check in advance whether the synthesizer has built-in filters that compensate for this.
I noticed this especially with the rev2 and it was really annoying in some places. sometimes it was the case that the sound was better integrated into the mix, but it was still more annoying than constructive.
I don’t think so … it’s the Moog Ladder lowpass filter and its “copies”. Many analoge circuits have a Q-compensation …
Just as an overview … discussion about various filter types:
i have to add that many people were annoyed about this phenomenon with the korg minilogue and korg then compensated with the xd.
That’s why no one ever was able to get a decent bass sound out of a Moog synthesiser… 
The vast majority of analogue synths will lose a bit of low end once resonance is pushed hard on a low pass filter, especially those with Moog style ladder filters.
There’s loads of digital synths that use bass compensation (I think the hydrasynth does and the modal argon/cobalt etc.) and I’m sure a few analogue ones too.
I can vouch for the Polivoks filter, it definitely does it less than a lot of other filters.
So this is a design consideration in all types of filters. There is no single construction or filter architecture that you can say 100% does not attenuate the passband. Designers do this for a reason, and it is to balance the volume of the resonance against the volume of the input. Without any pass band attenuation it can be hard to balance the sweet resonant sound against the input volume going to the filter, which tends to eat away at that sweet singing resonant sound that Moog and Roland filters are known for. But it is a common feature to have compensation for that, so you should just research any filter you are wanting to buy and listen to sound demos, it should be pretty obvious if you get a sweep of the resonance knob. One design I can say for sure that does not attenuate the passband at all is the Diode Ladder Filter from Moritz Klein and Erica Synths. I think it is more common on diode ladder filters, but I can’t say for sure.