Document:

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                                                                    Exhibit 10.4

                    FIRST AMENDMENT TO STOCKHOLDERS AGREEMENT

         This First Amendment (this "Amendment") is entered into as of October
13, 1999, by and among Digital Theater Systems, Inc., a Delaware corporation
(the "Company"), Forth Investments, LLC, Universal City Studios, Inc., and the
other stockholders of the Company listed on Annex I hereto, in order to amend
that certain Stockholders Agreement (the "Stockholders Agreement") dated as of
October 24, 1997, among the Company and the stockholders of the Company listed
on Schedule A thereto. Capitalized terms used in this Amendment and not defined
shall have the meanings given such terms in the Stockholders Agreement.

         WHEREAS, pursuant to Section 12(a) of the Stockholders Agreement,
except as otherwise provided therein, any amendment to the Stockholders
Agreement must be approved in writing by (i) the Company; (ii) the Stockholders
holding at least a majority in voting power of the Stockholders Shares subject
to the Stockholders Agreement; (iii) Spielberg (so long as Spielberg continues
to hold 50% or more of the Stockholders Shares held by Spielberg that are
subject to the Stockholders Agreement); (iv) Universal (so long as Universal
continues to hold 50% or more of the Stockholders Shares held by Universal that
are subject to the Stockholders Agreement); and (v) the holders of a majority in
voting power of the shares set forth on Annex I to the Shareholders Agreement
(collectively, the "Approving Parties"); and

         WHEREAS, the Approving Parties desire to amend the Shareholders
Agreement as set forth below.

         NOW THEREFORE, the undersigned, in consideration of the premises,
covenants and agreements contained herein, do hereby agree as follows:

1.       Clause (i) of the definition of "Excluded Securities" contained in the
Stockholders Agreement is hereby amended to read in its entirety as follows:

         "any options issued or issuable pursuant to a Stock Option Plan and any
         shares of Common Stock issuable upon exercise of any options granted
         pursuant to a Stock Option Plan; provided, that any shares of Common
         Stock which are so issued or issuable shall not exceed 2,510,466 shares
         of Common Stock in the aggregate,"

2.       Except as amended hereby, the Stockholders Agreement shall remain in
full force and effect.

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         IN WITNESS WHEREOF, the undersigned have caused this Amendment to be
duly executed as of the date and year first above written.

                                           Mr. Terry Beard

                                           By: ________________________________
                                               Mr. Terry Beard
                                               Management Shareholder &
                                               Chairman of the Board

                                           Digital Theater Systems, Inc.

                                           By: /s/ Dan Slusser
                                               ---------------------------------
                                               Dan Slusser
                                               Vice Chairman & CEO

                                           Forth Investments, LLC

                                           By: /s/ Michael Rutman

                                           Name: Michael Rutman

                                           Title: CFO

                                           Universal City Studios, Inc.

                                           By: /s/ William A. Sutman

                                           Name: William A. Sutman

                                           Title: SVP & CFO

                                           Westin Presidio Capital II

                                           By: /s/ James B. McElwee
                                               ---------------------------------
                                           Name: James B. Elwee

                                           Title: General Partner

                                  Page 2 of 2<PAGE>

                                                                    EXHIBIT 10.5

                   SECOND AMENDMENT TO STOCKHOLDERS AGREEMENT

         Second Amendment (this "Amendment"), dated as of April 4th, 2000, to
that certain Stockholders Agreement (the "Stockholders Agreement"), dated as of
October 24, 1997, among Digital Theater Systems, Inc., a Delaware corporation
(the "Company"), and the stockholders of the Company listed on Schedule A
thereto (the "Stockholders"), amended by First Amendment thereto dated as of
October 13, 1999. Capitalized terms used in this Agreement and not otherwise
defined shall have the meanings given such terms in the Stockholders Agreement.

         1.       Section 2(a)(ii)(A) of the Stockholders Agreement is hereby
                  amended to read in its entirety as follows:

                  "(A) two (2) representatives, designated by Terry Beard and
                  Patrick Beard, acting by a majority of interest as to the
                  shares owned by them."

         2.       Section 11(a) of the Stockholders Agreement is hereby amended
                  to read in its entirety as follows:

                  "(a) All of the provisions of this Agreement shall terminate
                  and, except as otherwise expressly provided herein, shall be
                  of no further force or effect and shall not be binding upon
                  any party hereto, upon the first to occur of (i) a Termination
                  Date and (ii) approval of such termination by each of (A) the
                  Company, (B) the holders of a majority in voting power of the
                  Series A Preferred Stock subject to this Agreement, (C)
                  Spielberg, (D) Universal, and (E) a majority in interest as to
                  the shares owned by Terry Beard and Patrick Beard."

         3.       Section 12(a) of the Stockholders Agreement is hereby amended
                  to read in its entirety as follows:

                  "(a) Amendment; Waiver and Release. Except as otherwise
                  provided herein, no modification, amendment or waiver of any
                  provision of this Agreement shall be effective unless such
                  modification, amendment or waiver is approved in writing by
                  (i) the Company, (ii) Stockholders holding at least a majority
                  in voting power of the Stockholder Shares subject to this
                  Agreement, (iii) Spielberg (so long as Spielberg continues to
                  hold 50% or more of the Stockholder Shares held by Spielberg
                  that are subject to this Agreement), (iv) Universal (so long
                  as Universal continues to hold 50% or more of the Stockholder
                  Shares held by Universal that are subject to this Agreement),
                  and (v) a majority in interest as to the shares owned by Terry
                  Beard and Patrick Beard. The failure of any party to enforce
                  any of the provisions of this Agreement shall in no way be
                  construed as a waiver of such provisions and shall not affect
                  the right of such party thereafter to enforce each and every
                  provision of this Agreement in accordance with its terms."

         4.       This Second Amendment may be executed in separate
                  counterparts, each of which shall be an original and all of
                  which taken together shall constitute one and the same
                  agreement.

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         5.       Except as provided for above, the terms of the Stockholders
                  Agreement, as amended by First Amendment thereto dated as of
                  October 13, 1999, shall remain in full force and effect.

         IN WITNESS WHEREOF, the parties hereto have executed this Second
Amendment, to Stockholders Agreement on the day and year first above written.

                                           DIGITAL THEATER SYSTEMS, INC.

                                           By: /s/ D.E. Slusser
                                               ---------------------------------

                                               Name: D.E. Slusser

                                               Title: CEO

                                               /s/ Terry Beard
                                               ---------------------------------
                                           Terry Beard, individually

                               [Other signatures]

                                       2

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In witness whereof, the parties have executed this Second Amendment to
Stockholders Agreement on the day and year first above written.

                                           EOS PARTNERS SBIC, L.P.

                                           By: Eos SBIC General, L.P.,
                                               its General Partner

                                           By: Eos SBIC, Inc.
                                               its General Partner

                                           By: /s/ Steven M. Friedman
                                               ---------------------------------

                                                Name: __________________________

                                                Title: _________________________

                                                Eos Partners SBIC, L.P.
                                                by Eos SBIC General, L.P., its
                                                  General Partner
                                                by Eos SBIC, Inc., its Managing
                                                  General Partner
                                                by Steven M. Friedman, President

                                       3

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         In witness whereof, the parties have executed this Second Amendment to
Stockholders Agreement on the day and year first above written.

                                           WESTON PRESIDIO CAPITAL II

                                           By: /s/ James B. McElwee
                                               ---------------------------------

                                               Name: James B. McElwee

                                               Title: General Partner

                                       4

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         In witness whereof, the parties have executed this Second Amendment to
Stockholders Agreement on the day and year first above written.

                                           UNIVERSITY CITY STUDIOS, INC.

                                           By: /s/ William A. Sutman
                                               ---------------------------------

                                               Name: /s/ William A. Sutman

                                               Title: SVP & CFO

                                       5

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         In witness whereof, the parties have executed this Second Amendment to
Stockholders Agreement on the day and year first above written.

                                           FORTH INVESTMENTS, INC.

                                           By: /s/ Michael Rutman
                                               ---------------------------------

                                               Name: Michael Rutman

                                               Title: CFO

                                       6

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                                           At Communications KK

                                           By: _________________________________

                                               Name: ___________________________

                                               Title: __________________________

                                           _____________________________________
                                           William Neighbors

                                           _____________________________________
                                           Buzz Knudson

                                                /s/ Jon Kirchner
                                           -------------------------------------
                                           Jon Kirchner

                                           _____________________________________
                                           Julie Koppel

                                           _____________________________________
                                           Mr. John C. Dyatt

                                           _____________________________________
                                           Mrs. John C. Dyatt

                                                /s/ Dan Slusser
                                           ------------------------------------
                                           Dan Slusser

                                           _____________________________________
                                           Richard Koppel

                                           _____________________________________
                                           Salah Hassanein

                                                /s/ Terry Beard
                                           -------------------------------------
                                           Terry Beard

                                       7

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