Converting stereo single ended to balanced mono?

I’m not sure if there might be some grounding issues. The source has a three prong plug, the two equalizers each have a two prong plug, amplification has 3 prong plug(s). 

Considering that the input would already have one inverted signal, I was wondering if just using one XLR  with the the ground of two RCAs tied to one pin and just a positive leg running to one RCA and the negative running to a second RCA, and then inputting the two separate RCAs to what would otherwise be the channel inputs of the other wise stereo inputs of the eq, and then having another split cable with two RCAs connected to an XLR connection, now converting two single stereo single ended stereo eqs into two mono balanced eqs would work? Am I missing something?

I’ve just acquired a pair of mono XLR input and output JP Labs Golden Flutes Bass Alignment Filters.....for KEF 104’s. JP Labs though prompt and courteous couldn’t offer me any help with modifying these things for the Thiel 3.5’s. They also suggested that the case work might need to be sacrificed towards that endeavor, something that I am willing to consider.

Armed with a Thiel 3.5 eq reverse engineered schematic & interior photo, two (actually 3) OEM stereo RCA Thiel 3.5 bass equalizers, and now a pair of XLR mono Golden Flutes for different speakers, what might be the best way towards getting true balanced bass eq for my Thiel 3.5’s? What might the parts costs be? What might the labor costs be? And who might be willing to the work?

As always, thanks in advance!

@atmasphere , PM sent

Thanks!

^Thank you!

Just last week I was lamenting that there was so little response.

 The schematic is beyond my comprehension, but I suspect might be invaluable.

 In the past week the Audiogon community has really impressed me with their selfless research, posting and invitations for private discourse.

Thank you all so very much! It truly is appreciated!

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Thanks for all your responses. I seem to be just as confused as when I first started.

I have considered bi-amping the 3.5's. The 3.5's only come with one set of binding posts per speaker. The earlier 3.0's came with two sets of binding posts per speaker. Perhaps "Coherent Source Service"

https://www.coherentsourceservice.com/

 the company made up of ex-Thiel techs could modify the 3.5's with earlier dual setup 3.0 binding posts. They are currently working on cap replacement/upgrades for the Jim Thiel designs, Unfortunately I'm led to believe that the 3.5 cap replacements are not currently on the front burner of development. I do have a bit of concern about the time delay between the signal that would go through the eq vs. the signal that doesn't. I realized that the time might be insignificant, but time integrity is one of the hallmarks of Thiel designs (and a handful of others). Heck, the cross-overs on the CS 5's were designed to move drivers back as little as 3/8".

https://www.stereophile.com/floorloudspeakers/690thiel/index.html

Furthermore, though bi-amping would help keep the eq out of the upper registers, the degree to which might be less than one might first assume due to the shallow 1st order cross-over. Still, despite the extra expense the thought has much merit.

Thanks again for the responses. I still don't feel like I understand this well enough. In any event I don't have the technical skills to pull this of myself and think I would have to hire some one to complete the task, should I go forward.

 I welcome any other thoughts or considerations.

 As always, thanks in advance.