UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1) CTS Corporation -------------------------------------------------------------------------------- (Name of Issuer) Common Stock -------------------------------------------------------------------------------- (Title of Class of Securities) 126501105 -------------------------------------------------------------------------------- (CUSIP Number) December 31, 2005 -------------------------------------------------------------------------------- (Date of Event which Required Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [X] Rule 13d-1(b) |_| Rule 13d-1(c) |_| Rule 13d-1(d) The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). SCHEDULE 13G 1 NAME OF REPORTING PERSON SS. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Columbia Wanger Asset Management, L.P. 04-3519872 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_| (b) [_] Not Applicable 3 SEC USE ONLY 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware 5 SOLE VOTING POWER 2,102,000 NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH 6 SHARED VOTING POWER 0 7 SOLE DISPOSITIVE POWER 2,102,000 8 SHARED DISPOSITIVE POWER 0 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,102,000 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES |_| Not Applicable 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.8% 12 TYPE OF REPORTING PERSON IA 1 NAME OF REPORTING PERSON SS. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON WAM Acquisition GP, Inc. 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) |_| (b) [_] Not Applicable 3 SEC USE ONLY 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware 5 SOLE VOTING POWER 0 NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH 6 SHARED VOTING POWER 2,102,000 7 SOLE DISPOSITIVE POWER 0 8 SHARED DISPOSITIVE POWER 2,102,000 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,102,000 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES |_| Not Applicable 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.8% 12 TYPE OF REPORTING PERSON CO Item 1. (a). Name of Issuer: CTS Corporation (b). Address of Issuer's Principal Executive Offices: 905 West Boulevard North Elkhart, Indiana 46514 Item 2. (a). Name of Person Filing: Columbia Wanger Asset Management L.P. ("WAM") WAM Acquisition GP, Inc., the general partner of WAM ("WAM GP") (b). Address of Principal Business Office or, if none, Residence: WAM and WAM GP are both located at: 227 West Monroe Street, Suite 3000 Chicago, Illinois 60606 (c). Citizenship or Place of Organization: WAM is a Delaware limited partnerhsip, WAM GP is a Delaware corporation. (d). Title of Class of Securities: Common Stock (e). CUSIP Number: 126501105 Item 3. If this statement is filed pursuant to sections 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a: (a)[ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o); (b)[ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c); (c)[ ] Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c.); (d)[ ] Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8); (e)[X] An investment adviser in accordance with section 240.13d-1(b)(1)(ii)(E) (WAM is an Investment Adviser registered under section 203 of the Investment Advisers Act of 1940; WAM GP is the General Partner of the Investment Adviser.); (f)[ ] An employee benefit plan or endowment fund in accordance with section 240.13d-1(b)(1)(ii) (F); (g)[ ] A parent holding company or control person in accordance with section 240.13d-1(b)(1)(ii)(G); (h)[ ] A savings associations as defined in section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813); (i)[ ] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3); (j)[ ] Group, in accordance with section 240.13d-1(b)(1) (ii)(J). If this statement if filed pursuant to Rule 13d-1(c), check this box. [X] Item 4. Ownership (at December 31, 2005). (a). Amount beneficially owned within the meaning of rule 13d-3:: (i) WAM: 2,102,000 (ii) WAM GP: 2,102,000 (b). Percent of class: (i) WAM: 5.8% (ii) WAM GP: 5.8% (c). Number of shares as to which the person has: (1) Sole power to vote or to direct the vote: (i) WAM: 2,102,000 (ii) WAM GP: 0 (2) Shared power to vote or to direct the vote: (i) WAM: 0 (ii) WAM GP: 2,102,000 (3) Sole power to dispose or to direct the disposition of: (i) WAM: 2,102,000 (ii) WAM GP: 0 (4) Shared power to dispose or to direct the disposition of: (i) WAM: 0 (ii) WAM GP: 2,102,000 Item 5. Ownership of Five Percent or Less of a Class: [ ] Not Applicable Item 6. Ownership of More Than Five Percent on Behalf of Another Person: The shares reported herein include the shares held by Columbia Acorn Trust (CAT), a Massachusetts business trust that is advised by WAM, a Delaware limited partnership. CAT holds 5.2% shares of the Issuer's shares. Item 7. Identification and Classification of Subsidiaries which Acquired the Security Being Reported on by the Parent Holding Company: Not Applicable Item 8. Identification and Classification of Members of the Group: Not Applicable Item 9. Notice of Dissolution of Group: Not Applicable Item 10. Certification: (a) The following certification shall be included if the statement is filed pursuant to 240.13d-1(b): By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. Disclaimer In accordance with Rule 13d-4 of the Securities Exchange Act of 1934, each of the persons filing this statement expressly disclaim the beneficial ownership of the securities covered by this statement and the filing of this report shall not be construed as an admission by such persons that they are the beneficial owners of such securities. SIGNATURES After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Date: February 14, 2006 The undersigned corporation, on the date above written, agrees and consents to the joint filing on its behalf of this Schedule 13G in conneciton with its beneficial ownership of the security reported herein. WAM Acquisition GP, Inc. for itself and as general partner of COLUMBIA WANGER ASSET MANAGEMENT, L.P. By: /s/ Bruce H. Lauer ------------------------------------- Bruce H. Lauer Senior Vice President and Secretary Exhibit Index Exhibit 1 Joint Filing Agreement dated as of February 14, 2006 by and among Columbia Wanger Asset Management, L.P.; WAM Acquisition GP, Inc.; and Columbia Acorn Trust. EXHIBIT 1 JOINT FILING AGREEMENT The undersigned hereby agree to the joint filing of the Schedule 13G to which this Agreement is attached. Dated: February 14, 2006 WAM Acquisition GP, Inc. for itself and as general partner of COLUMBIA WANGER ASSET MANAGEMENT, L.P. By: /s/ Bruce H. Lauer ----------------------------------- Senior Vice President and Secretary COLUMBIA ACORN TRUST By: /s/ Bruce H. Lauer ----------------------------------- Senior Vice President and Secretary