"such that" & "such as to", "so...that" &"so...as to", "such...that" &"such ...as to"

Question

If the subjects of the main clause and the subordinate clause are the same, we could simplify "such that" to "such as to", for example

1a Her voice was such that it made everyone stare. →
1b Her voice was such as to make everyone stare.

But we can't simplify

2a His anger was such that he lost control of himself. ↛
2b *His anger was such as to lose control of himself.

Am I right?

I also think this rule also applies to "so...that" and "so...as to", and "such...that" and "such...as to".

For example:

3a Her voice was so loud that it made everyone stare. →
3b Her voice was so loud as to make everyone stare.

4a He was such a fool that he believed him. →
4b He was such a fool as to believe him.

Am I right?

Answer 1

I don't have corpus research or an August Grammarian to back this up, but the examples you cite do appear to be correct to me. In particular, 3b and 4b are totally unremarkable.

1b is a little iffy--not grammatically wrong, just kind of awkward. Honestly, at a stylistic level, I would advise you to avoid either of the constructions in examples 1a and 1b, as they're needlessly wordy and confusing. I would much prefer:

Her voice made everyone stare

if you don't have an adjective or other detail you are highlighting that reveals what it was about her voice caused people to react like that.

Examples 3 & 4 don't have this issue, because "so [x] as to [y]" automatically highlights some particular detail and presents it as most significant.