ESR in speaker filter refurbishing...on the cheap way

A buddy want to swap his 40 years old speaker seems weaker whatever he îs standing in his room
Budget is a concern and some capacitance values in serie are highs.
Being in CE, I imagine some Mundorf lytics plain serie should cop, but I will measure the capacitance of the caps
Does capacitance move for lytic serie caps after 40 years...higher, lower ?
There is also no bypass, I have eventually some old styrens from philips I can give him...but is it good to mix a slow esr cap with a very low one of a tiny capacitance ? Seems an old way to bypass with 0.1 uF but is it still usefull todaý?
Cheap MKP in the 2 numbers range may fit on the pcb...but often I found it brighty if I remember from my limited speaker experience ?
I thought MKt that ESR lies between lytic and mkp are cheaper, but is that not also colored as the russian K73-16 are ?
What could I do to stay cheap? Bypass ? Cheap mkp or expensive Mundorf , generic mkt? ...
need to be axial for the pcb.
Sorry too much polemic please, just what was your experience to stay cheap and good enough either please?
Thank you, I'm not aware indeed about how to proceed... my tools are limited a dvm and a capacitance measurement device only.
I tried to dig a little on the Gravsen and Humble Homemade caps and speqkers site as well...most caps are mkp and they conclude the same... however Jantzen superior or copper from any brand are outside his wallet thickness....
Has anyone tried the german F&T bipolar speaker caps please ? Seems they have cheap lytic and maybr cheap mkp as well!
Personally, I would stick to the main brands and read the spec sheets. If there's no spec sheet or it's seriously lacking in detail, be very suspicious. If you look to the other thread you will see that some of the more esoteric stuff actually measures extremely poorly.
Btw. If you don't have an e.s.r. meter, it can be tested with a signal generator (sound card will do) and oscilloscope (again, if you are able to calibrate your sound card inputs and outputs this could also work).

Select a few useful frequencies and repeat the tests at each of them.

You can use peak or r.m.s. voltage, it doesn't matter (comes out in the wash).

First, determine the output impedance of the signal generator by measuring the voltage at no load, and again with a known impedance as a load (ie. A fixed resistor, say 100R).

Then, use the capacitor as a load and in this way, you can find the impedance of the capacitor.

Calculate the expected impedance for an ideal capacitor, and what's left over is the e.s.r. - at a high enough frequency for a given value of capacitor, the effects of capacitance can generally be ignored.
Btw. If you don't have an e.s.r. meter, it can be tested with a signal generator (sound card will do) and oscilloscope (again, if you are able to calibrate your sound card inputs and outputs this could also work).
Select a few useful frequencies and repeat the tests at each of them.
If you don't have a signal generator, a kiddie keyboard from the charity resale shop will do. Or a casio, mine was $10 because the display was trashed. Enter the correct 3 digits, the right sound comes out per the label. Pick a hammond organ or reed organ sound, those are nearly sine waves. Key frequencies are on wikipedia under piano frequencies. 27 to 4186 hz available on 88 keys, less on 61 or 49. An earphone jack should have at least 200 ohm output impedance. Speaker jack should be 8 ohms impedance.
I'm using a cheap bipolar 75 uf cap from parts-express in an allen organ S100 amp, seems to work okay. Don't know how long it will last. When replaced paper caps in a PAS2 preamp with polyester, didn't like the result. Too bright. Haven't monkeyed with crossover caps yet, ESR is important at high currents. Figure wattage of his amp: I=sqrt(Z/R) where Z is impedance wattage was quoted at. Motor phasing and sodium vapor lamp 440 vac caps are sometimes polyprophylene, have low ESR, and don't have the "audio grade" premium. Polyprophylene is John Curl's favorite dialectric. I used some 440 VAC 100 uf film caps from genelec in my H182 organ for B+ so I never have to replace those **** things again.
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Have to said I don't like the sound of the cheap mkps... too much on the bright side ; KP were better to me !

Here my concern is not too much about ESR measurement (but I will do for myself one day) as the speaker was full Lytics; but the good Lytics with "low" loss factor (say 6%) are almost as expensive than polyster (MkT)... but here, the monney is important, that's why I eventually asked about old MKC (cheap if you dig) and how they balance on a tweeter.
For the mid I'm going t buy cheap Nichicon bipolar for speakers for midrange. Mundorf is way to expensive in the capacitance I need for he mid... Should I or not bypass it ?? I really don't know ?! As for ESR, is it important in the midrange ??? I will be more concern (while I really don't know) about the ESL of the mid serie caps !
Btw, If not so expensive I would had test those yellow radial polyster film & PET dielectric from Cornel Dublier for the mid... very very low self inductance (2 nH) and DF low enough

As for the L pads caps between plus and minus, I surmise these are the ones to suffer the most, Is it good to consider cheap film cap here as well ?
I wanted buy some Erse, but FWIT then I read the HumbleHomeMadeHifi caps site... they may have a terrible behavior !
So no film tech and back to lyticks. Or the in between ESR from MKT film ?

According to you, is ESL is something to consider in a cap when having a mid driver in serie with it ?

For me the lyticks do the job but if I can improve a little for the same monney, why not ?!