Hi Doug,
My experimentation with the 4’s started in 1998 when I sent in the cans for a re-foam. At that time I noticed that the ’tufflex’ inside the cabinet was disintegrating.
I contacted JS at OHM and he said to go ahead and experiment with different batting material; my wife makes quilts now and then so I used that batting at first. That material was less dense than the tufflex so I used about 1/2" (two layers).
The original ’cradle’ that held the tufflex was ’U’ shaped made up of two nylon straps held in place inside the cabinet by 2" wide duct tape.
JS had told me that the straps should be placed 1/3 of the way down the cabinet and that the batting should be well tucked into the corners.
My first experiment was to lay the straps flat 1/3 of the way down as opposed to a ’U’ shape still using 1/2" of batting. I was shocked by the difference; more bass and treble but slightly recessed mids. mid/bass on voices was not neutral with chesty male voices and veiled female voices.
Out of curiosity I decided to use 1" of batting on the flat straps. More but sloppier bass, attenuated treble, sounded like a cheap box speaker and the mid/bass was a disaster.
My speakers are in the basement on carpet with thick dense under-padding layed over a cement floor. Since the vent is at the bottom I know this affects the overall SQ. With that in mind I placed the speakers on 1/4" acrylic plexi-glass (16"X16"). Well that certainly brings out the bass but I found the overall sound to be too live with too much reverb and accompanying listener fatique.
Back to the drawing boards. A few years ago my wife bought some batting for Christmas decorations i.e. snow on mantles look. This batting was thinner but denser than the quilt batting. So I decided to play with that.
I quickly realized that this new batting enabled me to dial in nuances that the other batting couldn’t. This stuff is just over 1/8" thick. I experimented with varying layers from one sheet to six. I also experimented on the flat vs: ’U’ shaped cradle..
What I’ve ended up with is a ’U’ shaped cradle with two sheets of this new batting. The treble and mid/bass are dialed in like never before. Female voices have an air that rivals electrostats and Leonard Cohen’s baritone is marvelous. The bass is not as prominent but very well defined and tight. That said, on recordings that feature bass like Nirvana’s ’Unplugged in New York’ it sounds very well balanced.
Got the cans back a month ago (2nd re-foam). John does a good job of making sure that they’re in sync prior to shipping... and they are.
Over the years I probably have spent around 200 hours trying to dial in the 4's to my preferences.... don't know of anyone else that has done that. OHM's newer models don't offer that flexibility as that cans are not attached to the cabinets with 4 wing nuts. However the newer models (since around 2003+) have the vent venting to a wooden base which most likely affords more predictable SQ.
Can't make a comparison between my 4's and newer models as I've never heard any other OHM speaker other than an F back in 1976 which absolutely blew me away.
