String Tension D'Addario EXP74 vs EXP74CM

[Harpua19]

Finally got a legit setup done on my 10 year old Michael Kelly Legacy FS. It is now playing how I always wished it would.

The tech did a great job, but he put EXP74s on; I've been using EXP74CMs the past couple months and like the balance. I asked him how out of whack things would get if I went back to the EXP74CMs and he said to keep using the EXP74s. He said the truss rod was pretty much maxed out. However, I don't think he really paid attention when I explained that gauge difference between the two sets seemed pretty minimal.

Any thoughts? Is my tech on point with this? Should I just try going back to the CMs next string change and see what happens? I really do prefer the balance, but if it's going to make a mess of things, it's not worth it.

[Drew Egerton]

The more knowledgeable folks here on setups can give you a better answer, but in my experience with both of these sets, the setup worked fine for both. I had been using regular 74s or the EXPs a long time, then went to using the A and E from the 75s and the latest I had on it was the new CMs. I didn't notice anything as far as buzzing or intonation issues that would need addressing after a switch.

[Tobin]

These are the string tensions from the D'Addario website:

EXP74 tensions:

G - 25.10
D - 23.30
A - 19.20
E - 23.20


EXP74CM tensions:

G - 23.71
D - 22.19
A - 21.91
E - 25.41

Curiously enough, they use the same gauge G and D strings, but the tensions are listed differently. I have no explanation for this. I don't believe they use different cores or windings. The EXP74CM set was supposedly a hybrid between the EXP74 and EXP75 series (using the G and D strings from the -74 set and the A and E strings from the -75 set, like Chris Thile did). That's even they way they describe it on their website. But different tensions?

Anyway, if we are to take their numbers at face value, you have a total string tension of 181.6 lbs with the EXP74 set, and 186.44 lbs with the EXP74CM set. That's a difference of 4.84 lbs, or a 2.67% higher overall string force.

When he said your truss rod was maxed out, I guess he meant it had no more adjustment. So any additional string tension would cause the neck to bow just a little more that he couldn't adjust back out. As for how much difference it will actually make, there's only one way to find out. Try 'em and see. It's not going to hurt anything.

[keithb]

I believe the CM set are "NY steel" while the others aren't, which may account for the tension difference.