LFM811 Project is a joint effort involving the design, manufacturing, testing and audio engineering skills of the following parties. PAUL F BERGETZ, of Alienconcepts, Des Plaines Illinois, BRUCE E BRECKENFELD , Sound Advice, Lake Geneva Wisconsin, and DAVID R PLAHM from Design Express, Orland Park Illinois.

The LFM811 is designed to be a retrofit for many standard basket designs as pictured below.

The "Rear Mounted Surround" eliminates this by attaching the "Surround" to the back side of the cone and rotating the "Roll Shape" 90 degrees radially inward .The surround is made of Ciba-Geigy RP6401 REN:C:O-THANE Polyurethane Elastomer. The driver can than be mounted using "Toe Clamps" (see illustration) in areas on the front of the speaker or rear mounting hardware from the inside of the cabinet. This design will fit in any cabinet that is currently using an industry standard 8" ,10" ,12" or 16" diameter driver.

We estimate that this design will increase efficiency, extend the usable bottom end another octave and decrease distortion in the 25hz -39hz range. This has been documented in the following article.

IMPEDANCE / RESONANCE:
The following two graphs represent the results of the driver resonance tests in "Free Air" and in an "Enclosure". These tests are the best we have ever seen on a system of this type and again reinforce the fact that the "Rear Mounted Surround" is a well balanced suspension system in keeping with the original design intent .

The top graph is "Free Air" resonance and the bottom graph is in an "Enclosure".

FREQUENCY RESPONSE:

These graphs represent frequency response with and without a crossover in the same enclosure. It is clearly evident that the 811 driver produces an average of 2db more output in the tested range with the same input level. The peaks at 1000hz, 2300hz, 3300hz and 6600hz (which are typical on low frequency drivers) are totally gone with the 811 driver which will make cross over design much easier. The bottom graph also shows a marked improvement in extending useful frequency response beyond 1000hz to 1700hz. This provides for easy construction of 2 way systems or reduced load on the mid-range driver in 3 way systems.

HARMONIC DISTORTION:
HDS measurements were taken with a TEF 20 analyzer using Sound Lab SLX software. These tests were taken from 25hz to 100hz (by 1/3rd octaves) with a range beginning at 95db and ending at 105db . (2nd, 3rd ,5th and 7th order are reflected in the test graphs shown at left.) All measurements were made using a BK Omni directional 4007 microphone positioned 1 meter on driver center and referenced to the same level. Both drivers were using the same suspension systems with 70oz ceramic magnet motors.

CONCERNS FROM PRIOR ART:
We call your attention to patent 2,490,466 12/06/1949 Loudspeaker Diaphragm Support Comprising Plural Compliant Members Harry F Olson Radio Corporation of America. On page 2 column 3 paragraph one Mr. Olson makes the following claim:

" THIS MAKES POSSIBLE THE USE OF A LARGER DIAPHRAGM WITH A GIVEN SIZE OF HOUSING FRAME AND DESIRED AMOUNT OF COMPLIANCE IN THE FLEXIBLE SUPPORT."

Figure 2 of this patent shows what appears to be an inward suspension ,however the drawing is not sectioned to show this.

SUMMARY:

The information enclosed in this report clearly shows a marked improvement in the areas of driver output , lower distortion and extended usable range. The key element to our patent claim is as noted:
What makes this design unique is the positioning of the flexible suspension component (1) which is disposed reward of the diaphragm (2) and is turned inward toward the center (3) of the assembly so that it does not extend beyond the diameter of said diaphragm's piston area. This allows the use of a diaphragm of the same diameter as the mounting flange (4) of the loudspeaker, resulting in an increase in acoustical output , reduced distortion and an extended usable range when the 811 driver is used for a replacement for conventional driver in an existing loudspeaker enclosure or enclosure design. (refer to diagram below)