I would highly advise not building that bookshelf. The main issue here is that Devon's "design", if you can even call it that, uses the stock JBL crossover which is meant for in ceiling (infinite baffle) placement. That stock crossover circuit lacks the necessary compensation for placing the driver on a smaller baffle. You can easily sim the results of this in vcad. The result is considerably less flat speaker than JBL's measurements, which clearly state they were taken in ceiling. You're not going to have a very enjoyable experience with a response like this.
This isn't speaker design, this is just gross incompetence. The fact that he is asking $6000 for this just makes it a scam. You could DIY it but what's the point, you'd still need to redesign the crossover at which point you're better off going with a different driver altogether.
It actually gets worse though. OJAS sells a horn kit for this speaker that removes the CD from coax loading and places it into a JBL horn, and it STILL uses the stock crossover.... If you're paying attention you'll be aware that removing the CD from the woofer has suddently introduced a big hole in the middle of the woofer, totally changing the porting of the cabinet for god knows what.
I very much doubt Devon has much of an idea of what he's doing and I would personally advise on avoiding his "designs".
Devon's designs and collaborations are for the multi-way forum, anyway you can't say his product isn't being promoted by the Influencers:
BTW, I second the Joseph Crow Audio recommendation. Troy actually has a couple Full Range single driver designs too
BTW, I second the Joseph Crow Audio recommendation. Troy actually has a couple Full Range single driver designs too