Amendment: SEC Form SCHEDULE 13D/A filed by Sphere Entertainment Co.

The disclosure in Item 2(b) is hereby amended by removing the information related to the CFD 2009 Trust and adding the New Group Members at the end thereof as follows: The business address of Patrick F. Dolan is c/o Dolan Family Office, attention: President, 340 Crossways Park Drive, Woodbury, New York 11797. Charles F. Dolan 2009 Family Trust FBO Patrick F. Dolan is a trust established under the laws of the State of New York for the benefit of Patrick F. Dolan and has an address of c/o Dolan Family Office, attention: President, 340 Crossways Park Drive, Woodbury, New York 11797. Marianne E. Dolan Weber 2012 Descendants Trust is a trust established under the laws of the State of New York for the benefit of the descendants of Marianne Dolan Weber and has an address of c/o MLC Ventures LLC, Attention: Richard Baccari, PO Box 1014, Yorktown Heights, New York 10598. Kathleen M. Dolan 2012 Descendants Trust is a trust established under the laws of the State of Vermont for the benefit of the descendants of Kathleen M. Dolan and has an address of c/o MLC Ventures LLC, Attention: Richard Baccari, PO Box 1014, Yorktown Heights, New York 10598.

The disclosure in Item 2(c) is hereby amended by adding the following at the end thereof: Patrick F. Dolan is a director of AMC Networks Inc. ("AMC"). AMC's principal business address is 11 Penn Plaza, New York, New York 10001.

The disclosure in Item 2(d) is hereby amended by adding the following at the end thereof: No New Group Member has, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

The disclosure in Item 2(e) is hereby amended by adding the following at the end thereof: No New Group Member has, during the last five years, been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

The disclosure in Item 2(f) is hereby amended by adding the following at the end thereof: Patrick F. Dolan is a citizen of the United States. The New Group Members that are trusts are organized in the jurisdiction set forth in Item 2(b).

The disclosure in Item 3 is hereby amended by adding the following at the end thereof: On September 8, 2025, the CFD 2009 Trust transferred an aggregate of 341,684 shares of Class B Common Stock to certain Group Members, as indicated in the table below, in partial repayment of promissory notes. The transferred shares constituted all of the shares of Common Stock held by the CFD 2009 Trust. For purposes of repayment of the promissory notes, the transferred shares were valued at $52.2025 per share, the mean of the high and low trading price for the Class A Common Stock on September 8, 2025. Number of Shares of Class B Common Stock Transferred Transferee to Transferee James L. Dolan 56,947 Charles F. Dolan 2009 Family Trust FBO Thomas C. Dolan 56,948 Charles F. Dolan 2009 Family Trust FBO Patrick F. Dolan 56,947 Charles F. Dolan 2009 Family Trust FBO Deborah A. Dolan-Sweeney 10,250 Charles F. Dolan Children Trust FBO Deborah Dolan-Sweeney 46,697 Marianne E. Dolan Weber 2012 Descendants Trust 56,948 Kathleen M. Dolan 2012 Descendants Trust 56,947

The disclosure in Item 4 is hereby amended by adding the following at the end thereof: The information contained in Item 3 of this Amendment No. 6 is incorporated by reference.

The disclosure in Item 5(a) and (b) is hereby amended and supplemented as follows: (a) and (b) As of September 8, 2025, the Group Members may be deemed to beneficially own an aggregate of 8,787,042 shares of Class A Common Stock as a result of their beneficial ownership of (i) 1,920,288 shares of Class A Common Stock (inclusive of exercisable options, restricted stock units vesting within 60 days of the date hereof and shares held by the Dolan Family Foundation, for which certain Group Members serve as director), and (ii) 6,866,754 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock. This aggregate amount represents approximately 24.6% of the total shares of Common Stock deemed to be currently outstanding. Group Members in the aggregate may be deemed to have the current shared power to vote or direct the vote of and to dispose of or direct the disposition of 6,866,754 shares of Class A Common Stock issuable upon conversion of an equal number of shares of Class B Common Stock (representing all outstanding Class B Common Stock) because of the terms of the Class B Stockholders' Agreement (as previously defined in the Schedule 13D). Reporting Persons and individuals who are not Group Members but are trustees of trusts that are Group Members may be deemed to beneficially own an additional 58,744 shares of Class A Common Stock. Each of the Reporting Persons disclaims beneficial ownership of the securities held by the other Reporting Persons, and this report shall not be deemed to be an admission that each such person is the beneficial owner of such securities. The percentages used herein with respect to the ownership of Class A Common Stock are calculated based on 28,503,635 outstanding shares of Class A Common Stock as of September 3, 2025, which is based on (i) 29,132,663 outstanding shares of Class A Common Stock as of July 31, 2025, as reported by the Issuer in its Quarterly Report on Form 10-Q that was filed with the SEC on August 11, 2025, adjusted to reflect (ii) the Issuer's repurchase of 629,028 shares of Class A Common Stock, as reported by the Issuer in a press release dated September 3, 2025. See the responses to Items 7 through 13 of each cover page to this Amendment No. 6, which are incorporated by reference. See Exhibit A for supplemental information regarding the beneficial ownership of Class A Common Stock by the Group Members and the other individuals who are not Group Members but are trustees of trusts that are Group Members. See Exhibit B for additional information regarding the Reporting Persons that are trusts.

See Item 5(a) above, Exhibit A and Exhibit B.

Other than as disclosed herein, there were no transactions in the Class A Common Stock effected during the past sixty days by the persons named in response to Item 5(a).

As further described in Item 3, as of September 8, 2025, the CFD 2009 Trust ceased to be a beneficial owner of Common Stock and a Group Member.

The disclosure in the section of Item 6 entitled "THE CLASS B STOCKHOLDERS AGREEMENT" is hereby amended by adding the following sentence after the last paragraph of such subsection: As of September 8, 2025, the CFD 2009 Trust ceased to be a party to the Class B Stockholders' Agreement and the New Group Members became parties to such agreement. The disclosure in the section of Item 6 entitled "REGISTRATION RIGHTS AGREEMENTS" is hereby amended by adding the following sentence after the last paragraph of such subsection: As of September 8, 2025, the Charles F. Dolan 2009 Family Trust FBO Patrick F. Dolan, the Charles F. Dolan Children Trust FBO Deborah Dolan-Sweeney, the Marianne E. Dolan Weber 2012 Descendants Trust and the Kathleen M. Dolan 2012 Descendants Trust each became a party to the Dolan Affiliates Agreement with respect to the shares of Class B Common Stock received from the CFD 2009 Trust, provided that the shares of Class B Common Stock received by the Charles F. Dolan Children Trust FBO Deborah Dolan-Sweeney are subject to the additional restrictions contained in the Dolan Children Trusts Agreement.

The disclosure in Item 7 is hereby amended by replacing all exhibits in the series of exhibits related to Exhibit A and Exhibit B and adding Exhibit C.2 and Exhibit D in appropriate order as follows: Exhibit A: Supplemental Beneficial Ownership Information Exhibit B: Amended and Restated Trust and Beneficiary List Exhibit C.2: Power of Attorney for each of Patrick F. Dolan, the Charles F. Dolan 2009 Family Trust FBO Patrick F. Dolan, the Marianne E. Dolan Weber 2012 Descendants Trust and the Kathleen M. Dolan 2012 Descendants Trust Exhibit D: Joint Filing Agreement, dated September 10, 2025.