The Loudspeaker-1, built by Paul

Copyright 2021 © Troels Gravesen

Hi Troels
First, thankyou so much for making this project available for DIY, it is great to be able to attempt a project of this scale knowing the design is so well thought through.

I made the semi-active TL-1 with only some slight changes to the original design. The look of the JBL 4345 with its 3 bass ports was something I liked, so the cabinet is a little deeper to accommodate the extra length needed for 3 instead of 2 ports and keep a tuning of about 24hz. Some extra volume also. The front panel is a 47mm thick  piece of 29mm birch ply + 18mm marine ply laminated together, with the outside panels all 29mm birch.

I was amazed how much wood these speakers required (!) and the project made me improve my router skills a lot. Sadly one vacuum cleaner enlisted to help with the router chips and dust suffered a painful death. 
Collecting the parts together was surprisingly easy, with the excellent kitset from Jantzen, speakers from Lean UK and L-pad attenuator from the USA all arriving to New Zealand with no issues.

The grills are covered in Mellotone guitar amp fabric and have felt on the insides, with small kids the speaker drivers will hopefully survive longer!  At some stage I may paint the front panels in a “JBL blue”and possibly they will look better with the grills attached but will live with them as is for little bit first.

After some months of construction it was pretty exciting to finally connect these behemoths up and play some music, and my expectations were high..

I have been playing them for a week now and cant imagine being any happier with the sound. I just want to play music all the time. As others have said, even at low levels the sound is still coherent, dynamic and engaging, and things only improve as the volume control inevitably goes higher. From top to bottom of the frequency range everything is clear, natural and relaxed and just a pleasure to listen to.
Now it is time to do some measurements and adjust the tweeter levels with the L-pad attenuators and do some bass management with the Hypex Filter Design program on the plate amps.  Room treatment and speaker placement are likely able to be improved, but will need to be domestically approved first.
Thanks again for this great design, I am planning on enjoying these for years to come