U.S. patent number 3,867,996 [Application Number 05/418,092] was granted by the patent office on 1975-02-25 for speaker enclosure.
This patent grant is currently assigned to Modular Sound Systems, Inc.. Invention is credited to Nils Lou.
United States Patent |
3,867,996 |
Lou |
February 25, 1975 |
SPEAKER ENCLOSURE
Abstract
A high fidelity speaker enclosure especially adapted for low
frequencies comprising a highly damped housing completely
surrounding the speaker with a sealed compartment adjacent the back
of the speaker, a second sealed compartment adjacent the front of
the speaker, a series of peripherally spaced slots in the front
compartment, and a cotton batting filtering means placed across the
front of the speaker.
Inventors: |
Lou; Nils (Saint Paul, MN) |
Assignee: |
Modular Sound Systems, Inc.
(Burnsville, MN)
|
Family
ID: |
23656682 |
Appl.
No.: |
05/418,092 |
Filed: |
November 21, 1973 |
Current U.S.
Class: |
181/148; 181/145;
181/146; 181/155 |
Current CPC
Class: |
G10K
11/002 (20130101) |
Current International
Class: |
G10K
11/00 (20060101); H04R 1/28 (20060101); G10k
013/00 (); H04r 001/28 () |
Field of
Search: |
;181/31B,145-146,148,175,155 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Tomsky; Stephen J.
Attorney, Agent or Firm: Schulte; Neil B.
Claims
I claim:
1. A high fidelity speaker enclosure for the production of lower
frequencies comprising a speaker and a closed housing having first
and second compartments therein with support means between said two
compartments to hold the speaker between the said two compartments,
the first compartment adjoining the back side of the speaker and
being sealed and acoustically damped, and the second compartment
being in communication with the front of the speaker and having a
plurality of narrow slots therein to allow passage of predominently
low frequency acoustical energy from the speaker, and including a
dome shaped acoustical filtering pad positioned in front of the
speaker in said second compartment.
2. The enclosure of claim 1 in which said first compartment is
damped with a layer of cork on the outside and a layer of resilient
material on the inside.
3. The apparatus of claim 2 including cotton batting on the inside
of said resilient layer.
4. The enclosure of claim 1 in which said narrow slots are disposed
about the periphery of the second compartment in planes generally
orthogonal to the front of the speaker.
5. The enclosure of claim 1 in which said dome shaped acoustical
filtering pad comprises a cotton batting material.
6. The enclosure of claim 4 in which said dome shaped acoustical
filtering pad comprises a cotton batting material.
7. The enclosure of claim 6 in which said first compartment is
damped with a layer of cork on the outside and a layer of resilient
material on the inside.
8. The apparatus of claim 7 including cotton batting on the inside
of said resilient layer.
9. The apparatus of claim 1 in which said second compartment has a
volume of about one third the first compartment so that the
apparent volume of the compartments as seen by the speaker is
approximately equal.
10. The apparatus of claim 4 in which said second compartment has a
volume of about one third the first compartment so that the
apparent volume of the compartments as seen by the speaker is
approximately equal.
Description
BACKGROUND OF THE INVENTION
In the prior art, high fidelity speakers are typically manufactured
with electronic crossover networks in order to deliver only the
appropriate frequencies to the bass, midrange and high frequency
speakers. These crossover networks absorb energy and decrease the
effectiveness of the amplifier. My invention avoids this
disadvantage by eliminating the electronic crossover network and
instead accomplishing the desired frequency selection by acoustical
methods as described hereinafter.
SUMMARY OF THE INVENTION
Briefly, my invention contemplates a speaker housing designed to
favor low frequency response. The speaker is sealed into an
enclosure having front and back compartments in communication
respectively with the front and back of the speaker. The back
compartment is completely sealed and insulated with suitable sound
deadening materials. The front compartment is sealed as well except
for a series of spaced peripheral slots. The slots have the dual
function of filtering out the higher frequencies and, at the same
time, permitting a limited amount of air expansion so that the
apparent volume of the front compartment, as seen by the speaker,
is balanced equally with the phsycially larger back compartment.
The balanced air pressure on both sides of the speaker ensures a
linear response from the speaker so that the fidelity of the system
is improved considerably. It may therefore be seen that it is an
object of my invention to provide an improved speaker enclosure
design especially suitable for lower frequencies. Further objects
and advantages will become apparent upon consideration of the
following description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of the preferred embodiment of my
invention which, due to the symmetry of the invention, may comprise
either a side sectional view or a front sectional view.
FIG. 2 is a perspective view of my invention showing the slots
about the periphery of the front compartment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring the FIGS. 1 and 2 it may be seen that the speaker
enclosure is formed from a basic housing 10 which has support
members 11 extending inward therefrom. Housing 10 may comprise
plywood or the like. A layer of cork 12 is bonded or otherwise
fastened to the outside of the housing 10 so as to insure good
sound deadening. The speaker 13 is mounted to support members 11
about its peripheral edge in a manner well known to those skilled
in the art and completely sealed so as to form a back compartment
17. Compartment 17 is additionally lined with a resilient material
16 such as roofing cement or the like and a one inch thick cotton
batting layer 18 which serves to break up standing waves. An end
member 14 is fastened over the bottom of housing 10 and the cork
layer 12 so as to form a front compartment 21 in communication with
the front of speaker 13. Another one inch thick cotton batting
layer 19 is fastened to support members 11 so as to completely
enclose the front of speaker 13. Cotton batting layer 19 acts as a
low pass filter. In addition, layer 19 has been found to produce a
phase shift in the emitted sound which is particularly favorable to
listening quality. Cotton batting layer 19 is fastened to members
11 in such a way as to hold it in a dome shape as shown in FIG. 1.
The dome shape is structurally resistant to being moved by the low
frequency sound vibrations from speaker 13 and eliminates standing
waves in the front compartment.
Front compartment 21 is sealed except for a series of narrow
elongated slots 15 formed in the periphery thereof. Slots 15 are
shaped and sized so as to readily allow the escape of low frequency
sound but form a relatively effective filter for midrange and
higher frequency signals. In the preferred embodiment forty slots
are utilized each having dimensions of approximately one eighth
inch width and two and one quarter inch length. These dimensions
are preferred only and other sizes could, of course, be used.
The volume of compartment 21 is approximately one third of the
volume of compartment 17. However, as far as the speaker is
concerned, slots 15 permits air to pass in and out of compartment
21 in an amount just sufficient so that it appears to speaker 13
that the volume of compartments 17 and 21 are about equal. Thus,
the speaker is pressure loaded in a balanced fashion so that the
voice coil excursion is practically linear. The following table
demonstrates the relative volumes of compartments 17 and 21 used in
the preferred embodiment for different size speakers:
Speaker size Back compartment Front compartment volume volume
______________________________________ 8 inch 900 .+-. 200 cu.
inches 300 cu. inches 10 inch 1200 .+-. 250 cu. inches 400 cu.
inches 12 inch 1500 .+-. 300 cu. inches 500 cu. inches 15 inch 1900
.+-. 350 cu. inches 600 cu. inches
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