On wall speaker questions

BassBox 6 Pro software suggests a sealed box of internal volume 0.14 cu ft for a single Peerless driver (f3 = 94 Hz). An internal volume of 0.28 cu ft would therefore be required for two drivers.

Your enclosure, according to your new dimensions, has an external volume of 0.6 cubic feet, which would result in a smaller internal volume by the time you allow for the thickness of the enclosure walls etc.

A vented (ported) enclosure would have to be around 0.75 cu ft internally to house a pair of the drivers.

The quoted volumes are suggestions from Parts Express, but I can't vouch for their accuracy. I offer them as a guide only.

Peerless GBS-135F25AL02-04 5-1/4" Aluminum Cone Woofer 4 Ohm

I'm sure more suggestions will follow.
 
The black lines in the attached graph, courtesy of audioxpress, show the bass response of the Peerless woofer in a sealed enclosure of internal volume 0.24 cu ft with 50% BAF absorbent filling.

It looks like a sealed internal volume of around 0.5 cu ft for a pair of woofers is a good target to aim for.
 

Attachments

  • GBS-135F25AL02-04 Woofer.jpg
    GBS-135F25AL02-04 Woofer.jpg
    367.8 KB · Views: 84
~ 0.4 cu ft is slap bang in the middle of my two examples of ~ 0.3 and ~ 0.5 cu ft.

So that should not be a problem as sealed enclosures are forgiving of small changes in enclosure volume.

Do you propose to use a subwoofer to reproduce the deep bass?
 
Yes absolutely I have not decided on that yet. This is the space I have for it. I have a Denon 4308ci to power the mains. I would love to have a 15" sub, but the newer subs with the isobaric and passive radiator designs things have come a long way!! The space is 24x24x14" tall with the hearth.JPEG_20211015_154321_3921708181657580874.jpg