Always nice to put on new strings. Not sure I understand what these are, though. Why are they labeled Alembic, they obviously are not Alembic brand strings? 

Nice top on your Series bass. 

Gabriel winds them to order — in this case, I gave him the measurements on my medium scale Series I, and he wound the set to fit. He prints his own packaging, so the client's name and any information about the bass gets added then.

That is good to know and the personalized custom packaging a nice touch. The only company I have been able to order custom length strings for specific instruments from is Pyramid. No charge either and they did a great job. My 78 Series five has a medium scale neck and fan headstock. I could never find stock strings that fit properly, particularly the B, the post is very close to the nut and invariably the windings broke on the B string. The custom Pyramid strings fit perfectly and sound great. I had them make a set of flats for my G. Gould five-string, too. It has a 35" scale and the wrap on some string brands sits on the bridge saddles and over some of the nut slots. The custom length Pyramid Gold strings sound amazing on that particular bass and help a lot with the zingy sounding top end of the EMG pickups in it. 

How do the David McCarthy stings sound?

They sound fantastic — big and warm with just the right amount of top end. The other sets I've used (including his guitar strings) last forever.

Edited to add: they're round core, so you have to crimp them if you trim excess length.

I spent a bunch of time playing over the weekend, and couldn't get over how good these new strings sounded to me. Then I started to wonder how much of it was their tone, and how much was psychological (they're specially made to my spec/they're not cheap/therefore they must be great), so I decided to A/B them with other strings I had on hand.

I grabbed a group of fresh round wound D strings that I had on hand (GHS Pressure Wound, Stringjoy, DR Sunbeams, Rotosound, and D'Addario Half Round), and rotated them through without changing the other strings on the bass, so I'd have an actual comparison in real time. The improvement in tone wasn't in my head.

It was an interesting experiment, but now I want to restring all my basses.

Part II: Short Scale.

He managed to make a set with a perfectly balanced low E.

Curious what the gauges are for the short-scale set, and if your source has made any flatwound strings? 

I think the set was 50-108. Unfortunately, he doesn't do flatwound (a friend of ours has hounded him about it).