Gruen Acoustic Guitars: About My Guitars
Paul Gruen - Luthier
I have played guitar since I was a child, and woodworking in the Gruen family spans four generations. I also have a scientific background and have studied guitar acoustics.
As a serious jazz and bluegrass guitarist, I became obsessed with the sounds of various handmade and factory guitars, whether flattops, archtops, or Selmer/Maccaferri types. The more I became interested in having a guitar built, the more I wanted to build one -- so I could create the sound I wanted!
I began building guitars by studying with Massachusetts luthiers Alan Carruth and Thomas Knatt, with whom I also studied plate tuning and modal analysis. Although I have built conventional steel-string guitars, my passion is a new type of guitar of my own design which I believe has more presence and projection than a flattop and more versatility than an archtop or a Selmer-type guitar. My "E.Q." guitars feature five soundholes: four ovals where f-holes traditionally appear on archtops, plus a small round center soundhole.
Construction variables affecting tone
I can dramatically affect the tone of a custom guitar by varying the following parameters:
- the stiffness of the top and back,
- the location and size of the oval and round soundholes,
- the scale length,
- the bridge mass and shape, and
- the (player-adjustable) height of the tailpiece
For example, if a customer truly wants a Gypsy Jazz guitar -- with a sound closest to the Selmer/Maccaferri guitars -- I will build a very stiff top and back, a very light bridge (scooped out from below), and I'll crank the tailpiece down so that the string angle over the bridge will be significantly greater than for other types of guitars.
The Concept of the "E.Q." Series of Guitars
My "E.Q." guitars, which are handmade and individually-voiced, combine construction principles of fine flattop, archtop, and "Selmer/Maccaferri" guitars. The tone of each customer's guitar is a function of the customer's preferences, with the capability to produce a sound which can include the bite and projection of archtops, the greater warmth and sustain of flattops, and the percussiveness of the Selmer-Macs. Their appearance is modern and sculptural yet reminiscent of the violin family.
The E.Q. guitars are loud and lively, with plenty of rich overtones. The response is quick and the guitars project well, in part because (1) the air volume is contained by shallow rims with large top and back plates, (2) they feature soundholes near the rims, and (3) they employ a tailpiece-and-floating- bridge configuration.
These guitars have so far appealed to a range of players -- jazz, gypsy jazz, bluegrass, blues, pop, fingerstyle and other styles, and to both professional and non-professional players. Some of these people are looking for something different, perhaps to be recognized for their own sound.
The E.Q. Models
The E.Q. guitars are available in 18", 17", and 16" lower bout widths -- these are referred to as the E.Q.18, E.Q.17, and E.Q.16 models. Though the E.Q.18 is a large guitar, it has been designed so that the player's right arm rests lower down than on the typical 18" archtop, providing much greater comfort. and in various woods, to accommodate each customer's desires.
Headstocks can be wide like those on archtops, offset (see pictures), or standard like those on flattops.
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Player-Controlled Balance ("E.Q.")
The E.Q. series of guitars allows for "player-controlled balance" (hence the model designation, "E.Q."). That is, the player can alter the balance of bass, midrange and treble by inserting one or two hardwood stoppers in any of four oval soundholes -- 11 possibilities in all! For example, when no stoppers are used, the guitar has the most "bite" and cutting sound, with the brightest bass. With one stopper closing one soundhole, the tone is "fattened" somewhat, in a manner that depends on which of the four soundholes is closed. The use of two stoppers further deepens the response, the overall "EQ" depending on which two of the four soundholes are chosen.
Thus, the acoustic, unamplified sound of these guitars can be altered at will by the player (even in the middle of a performance) for jazz, fingerstyle, bluegrass, blues, and other styles. Boost the treble and your lead solo will cut through the mix; choose a darker tonality for a solo ballad or to accompany a singer.
Height-Adjustable Bridge
I have always been dissatisfied with the typical archtop bridge, which uses metal thumbscrews to adjust the action. With such a bridge the entire sound for the guitar must pass through the "sound filter" of two brass screws!
Borrowing from the late Jimmy D'Aquisto, most of my guitars come with height-adjustable three-piece ebony bridges -- no metal screws. The middle piece of the bridge is wedge-shaped and can be moved to adjust the action. There is solid contact across the bridge, with only bridge wood as the sound medium.
For certain setups, such as with Gypsy jazz strings and a certain desired sound, I use a single-piece (non-height-adjustable) bridge in order to reduce the mass sufficiently. For such bridges, ebony or other hardwood "shims" can easily be placed under the bridge during, say, winter, when building heat systems typically reduce the relative humidity of the air (although cedar and redwood in particular are very stable despite changes in relative humidity).
Height-Adjustable Tailpiece
Most of my guitars feature my height-adjustable tailpiece, which allows me as well as the player to fine-tune the tone, volume, and sustain of each guitar to the particular strings and technique of the player.
As anyone who has ever played banjo (myself included) knows, adjusting the height of the tailpiece -- thereby varying the pressure of the strings on the bridge -- has a dramatic effect on volume, tone, and sustain. I designed a tailpiece that allows me to accomplish this on my guitars with the turn of an allen wrench, while the strings are at pitch.
My tailpieces are finished off with a cap of ebony, or with whatever wood the customer would like!
Optional Amplification
If amplification is desired, my preference is to outfit the guitar with the K&K "Trinity" system, which is a combination internal mike and under-bridgeplate piezos. This system allows for separate E.Q.'ing and then blending of the two means of amplification, for a very natural sound without typical piezo "quack." Moreover, it has absolutely no effect on the unamplified sound of the guitar. Magnetic pickups are another possibility, as are the numerous available electronic systems
New: the "Cello" E.Q. Guitar
The tone of any guitar is shaped in part by its "body modes" and "air modes" of vibration. The air modes are the various frequencies to which the air inside the guitar responds most sensitively. I have always enjoyed the tone of a cello being plucked. Since the elongated shape of the cello (compared to the guitar) affects some of its air modes, I wondered whether a proportionately-longer guitar would produce a somewhat cello-like tone.
Designing a long guitar that would be easy to hold and play was a lesson in ergonomics! The resulting shape is actually more comfortable to hold and play than that of a traditional guitar! It balances well on one or two knees, and the right arm is cradled so it can relax.
The "Cello-E.Q." guitar is a full-fledged "regular" guitar in terms of string tuning, string scale, and relative tone -- it's not a "baritone" guitar. It can be used anywhere a regular guitar can. The tone is very resonant and decidedly different, and it calls for much exploration on the part of the player. It is truly an instrument for the guitarist looking for something different and special!