The difference is that Harley’s book is a comprehensive guide and Paul’s is just his personal preference.
So, for example, the very first thing he says in the section on basic set-up is “Speakers need to be away from the wall”. That’s fine, as long as you don’t have, for example, Tannoy or Audio Note, that are designed to go flat against the wall.
An objective guide would first say “check your speaker manufacturer’s guide for recommended speaker placement”.
When Paul starts describing actual distances, he starts by saying place the speakers at least 4 ft from the far wall and 11 ft apart. In my new room, smaller than the current one, the speakers would be touching the walls.
Of course this highlights the point that there is no good distance for all speakers. With one of the best and most popular speakers like Harbeth P3ESR, 6 ft apart would be more than enough. I’ve re-scanned the chapter on how to choose speakers and - unless I missed it - the most basic piece of advice is missing: choose speakers that are the right size for your room.
In that chapter there is one of many classic Paulism’s, where he says: “While you may decide on a stand-mount speaker for some mysterious aesthetic reason, like my wife Terri did, I cannot imagine why”. Well Paul, the answer is engineering. All Harbeth and similar BBC-based soft-wall speakers are stand-mounts, designed to sit on open frames, so that they dissipate energy and manage resonances, which are fundamentals of speaker design. The other main benefit is to be able to get the tweeter at ear level, which can be difficult or impossible with floor-standing speakers. If PS Audio ever make a speaker as good as the stand-mount Harbeth M40.2 I’ll buy a copy of the book and eat it.
Whilst I’m having a minor gripe, there’s an interesting comment at 32% that says “By the time this Guide is published, my company PS Audio will bear making a line of great speakers - which makes your choice simple. Buy ours!”. Paul then apologises for the shameless plug, but that does beg the question about if the book is early or the speakers late. What I do not agree with is the next paragraph “My advice is rather straightforward: choose the company, its people, and its mission - not just the speaker.” (There is a comment after that disparaging old companies, which doesn’t sit comfortably with Harbeth - see above). I must admit that I fundamentally disagree, because he’s saying believe the marketing. As far as I’m concerned the only thing to believe is your ears. The last two speakers I bought are from companies I know nothing about when I first heard them. You know a speaker is good when you hear it, not because the company has a mission statement.
One final point. In the set-up one of the first listening tests is a a nice even bass response. You need the disc. You also probably need extremely good hearing and many years of experience to do this. My dealer did this when he set up my sub and I just watched in amazement. I had no idea what he was hearing. I could never do this accurately by ear and, as Paul says, you will likely drive yourself nuts doing it. These days, all you need is a $100 UMIK microphone and a laptop with REW downloaded (for free). This is the single best investment I ever made after my record cleaning machine. I would say it’s an invaluable tool. And if you have noise cancelling headphones you can do it without risk of insanity. At no point can I see Paul recommending using a microphone and frequency generator, which would seem to be set-up 101.