Figure 2. Mechanical drawing of one isolation mount, compressed to the proper pre-load using the provided tubular spacer. Click on drawing to view PDF.
Figure 3. Schematic illustrating the preferred use of four isolation mounts with a subwoofer enclosure.
Jon Raymond Whitledge, Polymer Scientist and Mechanical Engineer, is the originator and pioneer of loudspeaker enclosure isolation in automobiles.
Jon is excited to introduce a new and revolutionary PATENT PENDING product to the automotive industry - isolation mounts suitable for subwoofer enclosures and electronics consoles. A product like this was never available to installers until now!
Not only do the isolation mounts absorb vibration, they are also "fail-safe", meaning that they are mechanically inseparable in the event of a collision.
Until now, most if not all subwoofers, were rigidly attached to the structure of the vehicle. Consequently, all of the vibrations from the subwoofer were transmitted to the chassis, leading to localization cues, reduced clarity, and degraded articulation. If the subwoofer was mounted in the rear of the vehicle, the lower frequencies were projected from the rear, and therefore adversely affected the goal of up front imaging.
Even if the subwoofer is mounted in the front of the vehicle, the benefit of vibration isolation is also realized, because the deleterious sympathetic vibrations induced into the structure of the vehicle are not interfering with the desired output of the subwoofer. The result is greater clarity and articulation.
Electronics consoles can also benefit from isolation. In this case, the goal is the opposite - it is desired to prevent chassis vibrations from affecting electrical components, principally for two reasons. First, reduced vibrations should lead to enhanced longevity. Second, any possible effects of microphony are reduced substantially.
For these reasons, those seeking the ultimate sound quality performance can benefit from isolation. The mounts can be retrofitted to existing installations or be an integral part of the design for new installations. A multitude of applications and possibilities exist for the creative installer.
The isolation mounts are scientifically engineered with the most advanced viscoelastic elements and all hardware employs 6061-T6 aluminum or galvanized steel for rigidity and strength. The mount is anchored to the chassis of the automobile using an M6 or 1/4-inch threaded rod. The threaded rod is retained by suitable hardware such as a rivet nut or nut and washer. The L-bracket, which is isolated from the chassis by the viscoelastic elements, attaches to the isolated object (subwoofer enclosure, electronics console) with four M6 or 1/4-inch mounting screws, retained by suitable hardware such as t-nuts or nuts and washers. Please refer to the photos and dimensioned drawings.
Each isolation mount is intended to support 10 to 20 pounds of weight. Therefore, the use of four isolation mounts will support 40 to 80 pounds. It is preferable to load each mount with as close to 20 pounds as possible because improved performance is realized. Please refer to the predicted performance graphs below.
Each mount is designed for principally uniaxial loads in the z-direction (refer to subwoofer example utilizing four mounts), although the isolation mount will also resist substantially reduced lateral loads (approximately half) in both the x- and y-directions.
The retail price for a set of four isolation mounts is $480 plus taxes and shipping. The box in which the items are shipped, by FedEx, is 7 (seven) inches in length, width, and height, and weighs 9 (nine) pounds. Shipping costs and transit time can be estimated by using FedEx's rate calculator.
Figure 4. Predicted uniaxial (z-direction) isolation performance of one isolation device subjected to a 20-pound static load superimposed with a small sinusoidal oscillatory load whose frequency ranges from 10 to 300 Hz (Hertz). In this example, the resonant frequency of the system is about 12 Hz and its isolation performance begins at about 18 Hz and improves with increasing frequencies. Note that at 30 Hz more than 60% of the vibrational energy is absorbed, and by 80 Hz about 95% is absorbed! Also note there is a "Region of detriment", shown in red, where vibration amplification, rather than absorption, occurs - an unavoidable physical consequence. The goal, of course, is to restrict the region of detriment to the lowest possible frequencies where they become inconsequential.
Please refer to the photo gallery below:
Figure 5. Predicted uniaxial (z-direction) isolation performance of one isolation device subjected to a 10-pound static load superimposed with a small sinusoidal oscillatory load whose frequency ranges from 10 to 300 Hz (Hertz). In this example, the resonant frequency of the system is about 19 Hz and its isolation performance begins at about 28 Hz and improves with increasing frequencies. Note that at 30 Hz only about 10% of the vibrational energy is absorbed, about 50% at 40 Hz, and by 80 Hz almost 90% is absorbed!
Figure 1. Mechanical drawing of one isolation mount, uncompressed. Click on drawing to view PDF.
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Isolation Devices, set of four
(excluding taxes and FedEx shipping)
The Magic Bus by Jon Raymond Whitledge