Would love to hear about your build ... please check in and let us know how it's going!

I am thinking of using a "squishy" mount for the driver. Since this is an open baffle speaker, I thought I could take advantage of the fact that there is no need to air-seal the driver to the baffle, and instead create a highly damped connection to eliminate vibration.

The current plan is to use a pair of 3/16" thick vibration mounts at the top and bottom of each mounting bolt, which will pass completely through the baffle and be lightly compressed by a nut on its back surface. The driver flange will be recessed into the baffle and mounted flush. I will oversize the recess by about 1/16" at its outer diameter, so the lateral surface of the driver flange will make no physical contact with the baffle. This will leave a 3/16" gap underneath the flange between each mounting bolt, and a roughly 1/16" gap around the entire outer perimeter of the driver.

My question is this: does anyone think there will be a disadvantage to allowing a free-air gap around this driver?

Yes the bass would suffer loss with a gap IMHO. The whole idea of a baffle of any kind open or otherwise is to separate the front and back wave of the driver. What level of separation or isolation is required is debatable. Bass waves are large enough to cancel even on a baffle the size of a large door. If you leave an unsealed gap around the driver flange what is the baffle doing to help the bass frequencies? Something? Yes. Lots less than if it were sealed. If you use a 1.5" thick or more baffle any vibration that might make it to the driver is inconsequential compared to the loss of bass energy that would not give the speaker a pleasing frequency response. If you left the gap in and filled it in with some strips of craft foam stuffed into the gap that might do the sealing you need for bass response and still keep the driver isolated from baffle vibrations. Steve and others might like to clarify this point but most of the time I have not seen serious builders of open baffle speakers fuss over not having the driver mounted to the baffle directly but have chosen to rely on baffle stiffness and mass to overcome vibration. Also a baffle that has sandwich layers of softer less dense material alternating with harder heavier dense material is a possibility. Hope this helps.

Congrats brother, you will never hear music the same again. Photos please

http://www.linkwitzlab.com/orion-rev1.htm

Here's one more that talks about motor mounting the driver. Sounds like a very soft foam will do the trick for the air gap.

I took a look at them but I think they're too large for this and the load is too small. I order the 1/4" sheet product and I'm going to use some metal punches to cut my own out of it. I'll experiment a bit and put up pictures if I get something that works.

4x8 baltic birch before cutting

Waste from the 4x8 sheet. There is just enough to replace one of the larger panels if I blow it somehow.

Were there any finished pictures of this project?

I have the speakers assembled but not glued or finished. I spent a few hours listening to them last night for the first time, and I can say that the effort of building the ZOBs was well worth the trouble. They have outrageous imaging and soundstage, and very good dynamics. A touch soft in the mid-bass region, but my Vandersteen subs fill in the low end nicely and seem like a nice match. The acousta-stuff may even out the low-end response a bit once I seal and stuff the cabinets.

Since I listen to a lot of rock, I was worried they wouldn't have the dynamics I love, but they do. They aren't the heaviest hitters, but I knew that going in - my highest priority is the openness of the baffle setup, and that is delivered quite well.

They are extremely sensitive to, or maybe I should say revealing of, the recording material. There is a very open and airy sound to them, probably typical of all open baffle speakers, and I agree that it is similar to an electrostatic speaker - I've had Martin Logans and Magnepans. They both had integration and soundstage issues I didn't like, nor could they deliver anything like the dynamics you easily get from the ZOBs - though the Martin Logans came close. Needless to say, with my better recordings, I had a few smiles on my face. Of course they probably have a bit of a shine on them because after all this work I simply couldn't bear for them to sound mediocre - so I want to avoid hyperbole. Obviously, there are better speakers to be had, but probably not for anything near the money I DIY'd these ZOBs for.

I used a single sheet of baltic birch plywood for the cabinets (per earlier posts), and quarter-sawn sapele for the baffles. The joinery is simple dowling - not perfect, but good enough. A plunge router and circle jig were extremely useful for cutting the port and driver holes, and for cutting the groove for the sliding panel. I've included a few pictures in the following posts. I will final sand and finish them in the next few weeks.

Construction pic - mounting the baffles.

The very first step in assembly...

Ha! No, that's Cookie, the build supervisor and main reason my speakers sat unbuilt for 2 years. Lol.