The Tunable Speakers
I’ve been making speakers a long time like many of you. Early on in my adventures I noticed a problem. Everytime I walked into a different recording studio the same speakers sounded different and I ended up spending all kinds of time playing with the EQ to try to find a reference point between the "Live Room" and the "Control Room" and than there was the playback or "Mastering Room". Guys would take the recordings and play them in their cars, and some used headphones and some just decided to suffer through the control room monitors. You’ve all seen pictures of the recording console with several different pairs of speakers. Many times JBL, NS10’s and one or two others on stand by.
In the late 70’s I finally got tired of having to deal with this when I was doing the setups, and I started playing with the idea of making a speaker that I could use with some kind of consistency. For years I would build custom speaker stands and speakers and speaker clamps until I finally landed on something that worked for me. The first tunable speakers were crude torture looking things, but they worked and studios started using them for main mix down monitors the "studio 5". Time went on and I was asked to be the acoustician for UMI (United Musical Instruments). This opened up the door to work more closely with the actual making of horns, wood winds, cellos, guitar, violins, violas and the coolest of cool, building rooms for Steinways.
Around 1989 or so I started to make my speakers out of instrument woods instead of MDF and found tons more tone to play with. This put into action the next 15 plus years in design hunting for the right drivers and parts and pieces so that I could make the most simple to drive speaker that I could (and low mass). For tweeters I used ribbons, silk domes, horns and pretty much the full range of everything I could find. Every time I went more complicated I ended up needing crossover work done and my goal was to go crossoverless. I had found the sound of the cap I wanted to use but drivers were a bugger. Finally I threw out everything and started from scratch. On the cabinet side I was doing pretty well as I got the inside tuning bar down to a science. The Tuning bar works like this. Instead of building heavy cabinets the tuning bar applies the force from the inside and the tuning bolt and washer on the outside supplies the inward force. Because the cabinet has both inside and outside force going on you can adjust the cabinets tone. Where most cabinet designs push outward mine equalize the pressure. The wood of the speaker is low mass compressed board treated with instrument finish. Except for the front baffle board which is a guitar body board. The whole speaker is then veneered in cherry.
The drivers however were a pain. I didn’t like anything I heard. There use to be some nice stamped drivers made in Europe but lately nothing that was what I wanted. I decided on modifying the standard Vifa D27 or ScanSpeak but still I wasn’t happy. Then it dawned on me to make my own baskets. This changed everything. I saw Kosst said I used 3.5" paper tweeters (stamped) as if that was a bad thing lol. Well it would be a bad thing except my baskets are redwood. Again the "walk" Kosst. All my drivers are redwood voiced drivers. The tone is out of this world. Ask the folks who have them. They’re pretty darn snappy pappy:)
The tuning is just as cool as the speaker. Lets say I’m playing cymbals and they are a little loose sounding. Lets say the halos are a tad too wooly. All you do is barely tighten the Tuning Bolt and the cymbal will tighten right up. The new Revs are pretty special. And yes if someone wants the ribbon or silks we do custom sets. We’re doing a set of ribbons right now.
Michael Green
www.michaelgreenaudio.net