<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    Form 10-Q

         [X]  QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
              OF THE SECURITIES EXCHANGE ACT OF 1934
              for the quarterly period ended September 30, 1999
                                   OR
         [ ]  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)
              OF THE SECURITIES EXCHANGE ACT OF 1934

Commission File Number 0-3295
--------------------------------------------------------------------------------

KOSS CORPORATION
--------------------------------------------------------------------------------
(Exact Name of Registrant as Specified in its Charter)


A DELAWARE CORPORATION                           39-1168275
--------------------------------------------------------------------------------
(State or other jurisdiction of     (I.R.S. Employer Identification No.)
 incorporation or organization)


4129 North Port Washington Avenue, Milwaukee, Wisconsin   53212
--------------------------------------------------------------------------------
(Address of principal executive office)                 (Zip Code)


Registrant's telephone number, including area code:  (414) 964-5000
                                                     --------------

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.

                                  YES   X      NO
                                      ------    ------

At September 30, 1999,  there were 2,670,369 shares outstanding of the
Registrant's common stock, $0.01 par value per share.

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                        KOSS CORPORATION AND SUBSIDIARIES
                                    FORM 10-Q
                               September 30, 1999


                                      INDEX



                                                                           Page
PART I   FINANCIAL INFORMATION

         Item 1     Financial Statements

                    Condensed Consolidated Balance Sheets
                    September 30, 1999 (Unaudited) and June 30, 1999        3

                    Condensed Consolidated Statements
                    of Income (Unaudited)
                    Three months ended September 30, 1999 and 1998          4

                    Condensed Consolidated Statements of Cash
                    Flows (Unaudited)
                    Three months ended September 30, 1999 and 1998          5

                    Notes to Condensed Consolidated Financial
                    Statements (Unaudited) September 30, 1999               6-7

         Item 2     Management's Discussion and Analysis of
                    Financial Condition and Results of Operations           8-10


PART II  OTHER INFORMATION

         Item 4     Submission of Matters to a Vote of Security-Holders     11

         Item 6     Exhibits and Reports on Form 8-K                        11


                                     2 of 12


<PAGE>   3


                        KOSS CORPORATION AND SUBSIDIARIES

                      CONDENSED CONSOLIDATED BALANCE SHEETS


<TABLE>
<CAPTION>
                                                         September 30, 1999     June 30, 1999
                                                            (Unaudited)              (*)
                                                      -----------------------------------------
<S>                                                        <C>                  <C>
ASSETS
     Current Assets:
          Cash                                              $2,081,607           $1,171,504
          Accounts receivable                                8,031,863            7,407,539
          Inventories                                       12,163,224           12,955,118
          Income taxes receivable                              295,402              266,329
          Other current assets                                 937,913              867,846
-------------------------------------------------------------------------------------------
               Total current assets                         23,510,009           22,668,336

     Property and Equipment, net                             1,774,518            1,869,598
     Intangible and Other Assets                             1,179,114            1,183,762
-------------------------------------------------------------------------------------------
                                                           $26,463,641          $25,721,696
===========================================================================================


LIABILITIES AND STOCKHOLDERS' INVESTMENT
     Current Liabilities:
          Accounts payable                                 $   786,825          $   791,785
          Accrued liabilities                                1,158,991              891,392
-------------------------------------------------------------------------------------------
               Total current liabilities                     1,945,816            1,683,177

     Deferred Compensation and Other Liabilities             1,396,354            1,367,584
     Contingently Redeemable Equity Interest                 1,490,000            1,490,000
     Stockholders' Investment                               21,631,471           21,180,935
-------------------------------------------------------------------------------------------
                                                           $26,463,641          $25,721,696
===========================================================================================
</TABLE>

*        The balance sheet at June 30, 1999 has been prepared from the audited
financial statements at that date.

See accompanying notes.



                                    3 of 12

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                        KOSS CORPORATION AND SUBSIDIARIES

                   CONDENSED CONSOLIDATED STATEMENTS OF INCOME
                                   (Unaudited)



<TABLE>
<CAPTION>
Three Months Ended September 30                1999                 1998
----------------------------------------------------------------------------
<S>                                       <C>                   <C>

Net sales                                  $ 8,393,253           $ 9,031,043
Cost of goods sold                           4,913,277             5,058,104
----------------------------------------------------------------------------
Gross profit                                 3,479,976             3,972,939
Selling, general and
   administrative expense                    1,830,587             2,056,767
----------------------------------------------------------------------------
Income from operations                       1,649,389             1,916,172
Other income (expense)
   Royalty income                              274,632               253,314
   Interest income                              16,799                 3,938
   Interest expense                                 --               (50,950)
----------------------------------------------------------------------------
Income before income tax provision           1,940,820             2,122,474
Provision for income taxes                     757,203               831,013
============================================================================
   Net income                              $ 1,183,617           $ 1,291,461
============================================================================
Earnings per common share:
   Basic                                         $0.44                 $0.41
   Diluted                                       $0.43                 $0.40
============================================================================
Dividends per common share                        None                  None
============================================================================
</TABLE>


See accompanying notes.



                                     4 of 12

<PAGE>   5



                        KOSS CORPORATION AND SUBSIDIARIES

                 CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                   (Unaudited)


<TABLE>
<CAPTION>

Three Months Ended September 30                            1999              1998
---------------------------------------------------------------------------------------
<S>                                                   <C>                <C>

CASH FLOWS FROM OPERATING
ACTIVITIES:
     Net income                                        $ 1,183,617        $ 1,291,461
     Adjustments to reconcile net
       income to net cash provided by
       operating activities:
         Depreciation and amortization                     207,511            173,638
         Deferred compensation                              28,770             28,770
         Net changes in operating assets and
           liabilities                                     340,450             29,227
---------------------------------------------------------------------------------------
     Net cash provided by operating
         activities                                      1,760,348          1,523,096
---------------------------------------------------------------------------------------
CASH FLOWS FROM INVESTING
ACTIVITIES:
     Acquisition of equipment
         and leasehold improvements                       (117,163)          (139,826)
---------------------------------------------------------------------------------------
         Net cash used in
          investing activities                            (117,163)          (139,826)
---------------------------------------------------------------------------------------
CASH FLOWS FROM
FINANCING ACTIVITIES:
  Repayments under line of credit agreements                    --         (7,610,000)
  Borrowings under line of credit agreements                    --          6,231,000
  Purchase and retirement of common stock                 (806,563)                --
  Exercise of stock options                                 73,481                 --
---------------------------------------------------------------------------------------
    Net cash used in
      financing activities                                (733,082)        (1,379,000)
---------------------------------------------------------------------------------------
Net increase in cash                                       910,103              4,270
Cash at beginning of year                                1,171,504             14,778
=======================================================================================
Cash at end of period                                  $ 2,081,607          $  19,048
=======================================================================================
</TABLE>


See accompanying notes.


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                        KOSS CORPORATION AND SUBSIDIARIES
                               September 30, 1999
              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS


1.       CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

         The financial statements presented herein are based on interim amounts
         and are subject to audit. In the opinion of management, all adjustments
         (consisting only of normal recurring accruals) necessary to present
         fairly the financial position, results of operations and cash flows at
         September 30, 1999 and for all periods presented have been made. The
         income from operations for the quarter ended September 30, 1999 is not
         necessarily indicative of the operating results for the full year.

         Certain information and footnote disclosures normally included in
         financial statements prepared in accordance with generally accepted
         accounting principles have been condensed or omitted. It is suggested
         that these condensed consolidated financial statements be read in
         conjunction with the financial statements and notes thereto included in
         the Registrant's June 30, 1999, Annual Report on Form 10-K.

2.       EARNINGS PER COMMON AND COMMON EQUIVALENT SHARE

         Basic earnings per share are computed based on the weighted average
         number of common shares outstanding. The weighted average number of
         common shares outstanding for the quarters ending September 30, 1999
         and 1998 were 2,686,791 and 3,177,269, respectively. When dilutive,
         stock options are included as share equivalents using the treasury
         stock method. Common stock equivalents of 58,526 and 38,769 related to
         stock option grants were included in the computation of the average
         number of shares outstanding for diluted earnings per share for the
         quarters ended September 30, 1999 and 1998, respectively.




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<PAGE>   7



3.       INVENTORIES

         The classification of inventories is as follows:

<TABLE>
<CAPTION>
                                       September 30, 1999    June 30, 1999
               -------------------------------------------------------------
<S>                                          <C>                 <C>
               Raw materials and
                 work in process              $4,421,925          $4,642,396
               Finished goods                  8,802,568           9,334,805
               -------------------------------------------------------------
                                              13,224,493          13,977,201
               LIFO Reserve                   (1,061,269)         (1,022,083)
               -------------------------------------------------------------
                                             $12,163,224         $12,955,118
               =============================================================
</TABLE>

4.       STOCK PURCHASE AGREEMENT

         The Company has an agreement with its Chairman to repurchase stock from
         his estate in the event of his death. The repurchase price is 95% of
         the fair market value of the common stock on the date that notice to
         repurchase is provided to the Company. The total number of shares to be
         repurchased shall be sufficient to provide proceeds which are the
         lesser of $2,500,000 or the amount of estate taxes and administrative
         expenses incurred by his estate. The Company is obligated to pay in
         cash 25% of the total amount due and to execute a promissory note at
         the prime rate of interest for the balance. The Company maintains a
         $1,150,000 life insurance policy to fund a substantial portion of this
         obligation. At September 30, 1999 and June 30, 1999, $1,490,000 has
         been classified as a Contingently Redeemable Equity Interest reflecting
         the estimated obligation in the event of execution of the agreement.

5.       DEFERRED COMPENSATION

         In 1991, the Board of Directors agreed to continue John C. Koss'
         current base salary in the event he becomes disabled prior to age 70.
         After age 70, Mr. Koss shall receive his current base salary for the
         remainder of his life, whether or not he becomes disabled. The Company
         is currently recognizing an annual expense of $115,080 in connection
         with this agreement, which represents the present value of the
         anticipated future payments. At September 30, 1999 and June 30, 1999,
         respectively, the related liabilities in the amounts of $910,230 and
         $881,460 have been included in deferred compensation on the
         accompanying balance sheets.


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<PAGE>   8


                        KOSS CORPORATION AND SUBSIDIARIES
                         FORM 10-Q - September 30, 1999
                     MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                  FINANCIAL CONDITION AND RESULTS OF OPERATIONS

Financial Condition and Liquidity

Cash generated by operating activities during the three months ended September
30, 1999 amounted to $1,760,348. Working capital was $21,564,193 at September
30, 1999, an increase of $579,034 from the balance at June 30, 1999. The cash
necessary to fund the Company's operating activities fluctuates from time to
time; however, as a general rule, the Company expects to generate adequate
amounts of cash to meet future operating needs. The Company maintains sufficient
borrowing capacity to fund any shortfall.

Capital expenditures for new property and equipment (including production
tooling) were $117,163 for the quarter. Budgeted capital expenditures for fiscal
year 2000 are $832,100. The Company expects to generate sufficient operating
funds to fulfill these expenditures.

Stockholders' investment increased to $21,631,471 at September 30, 1999, from
$21,180,935 at June 30, 1999. The increase reflects the effect of net income,
the purchase and retirement of common stock, and the exercise of stock options
for the quarter.

The Company amended its existing credit facility in April 1999, extending the
maturity date of the unsecured line of credit to November 1, 2000. This credit
facility provides for borrowings up to a maximum of $10,000,000. The Company can
use this credit facility for working capital purposes or for the purchase of its
own stock pursuant to the Company's stock repurchase program. This credit
facility was increased from $8,000,000 to $10,000,000 as a result of combining
the Company's $8,000,000 working capital credit facility with the Company's
$2,000,000 stock repurchase credit facility. Borrowings under this credit
facility bear interest at the bank's prime rate, or LIBOR plus 1.75%. This
credit facility includes certain financial covenants that require the Company to
maintain a minimum tangible net worth and specified current, interest coverage,
and leverage ratios. There was no utilization of this credit facility at
September 30, 1999.

In April of 1995, the Board of Directors approved a stock repurchase program
authorizing the Company to purchase from time to time up to $2,000,000 of its
common stock for its own account. In January of 1996, the Board of Directors
approved an increase in the stock repurchase program from $2,000,000 to
$3,000,000. In July of 1997, the Board of Directors again approved an increase
in the stock repurchase program from $3,000,000 to $5,000,000. In January of
1998, the Board of Directors approved an increase of an additional $2,000,000,
increasing the total stock repurchase program from $5,000,000 to $7,000,000. In
August of 1998, the Board of Directors approved an increase of $3,000,000 in the
Company's stock repurchase program, increasing the total amount of stock
repurchases from $7,000,000 to $10,000,000. In April of 1999, the Board of
Directors again approved an increase in the stock repurchase program from
$10,000,000 to $15,000,000. In October of 1999, the Board of Directors further
increased the


                                     8 of 12
<PAGE>   9




stock repurchase program by $5,000,000 to a maximum of $20,000,000. The Company
intends to effectuate all stock purchases either on the open market or through
privately negotiated transactions, and intends to finance all stock purchases
through its own cash flow or by borrowing for such purchases. For the quarter
ended September 30, 1999, the Company purchased 68,250 shares of its common
stock at an average gross price of $13.62 per share (and an average net price of
$12.35 per share), and retired all such shares.

From the commencement of the Company's stock repurchase program through
September 30, 1999, the Company has purchased and retired a total of 1,448,248
shares for a total gross purchase price of $15,974,888 (representing an average
gross purchase price of $11.03 per share) and a total net purchase price of
$13,181,116 (representing an average net purchase price of $9.10 per share). The
difference between the total gross purchase price and the total net purchase
price is the result of the Company purchasing from certain employees shares of
the Company's stock acquired by such employees pursuant to the Company's stock
option program. In determining the total dollar amount available for purchases
under the stock repurchase program, the Company uses the total net purchase
price paid by the Company for all stock purchases, as authorized by the Board of
Directors.

The Company also has an Employee Stock Ownership and Trust ("ESOP") pursuant to
which shares of the Company's stock are purchased by the ESOP for allocation to
the accounts of ESOP participants. For the quarter ended September 30, 1999, the
ESOP did not purchase any shares of the Company's stock.

Results of Operations

Net sales for the quarter ended September 30, 1999 were $8,393,253 compared with
$9,031,043 for the same period in 1998, a decrease of $637,790.

Gross profit as a percent of net sales was 41% for the quarter ended September
30, 1999 compared with 44% in the prior year. This decrease is primarily due to
a change in product mix.

Selling, general and administrative expenses for the quarter ended September 30,
1999 were $1,830,587 or 22% of net sales, as against $2,056,767 or 23% of net
sales for the same period in 1998.

For the quarter ended September 30, 1999, income from operations was $1,649,389
versus $1,916,172 for the same period in 1998, a decrease of $266,783.

Interest expense amounted to $0 for the quarter as compared to $50,950 for the
same period in the prior year. This decrease is a result of no borrowing
activity for the quarter as compared to the same period last year.

The Company has a License Agreement with Jiangsu Electronics Industries Limited
("Jiangsu"), a subsidiary of Orient Power Holdings Limited, by way of an
assignment of a previously existing License Agreement with Trabelco N.V. Orient
Power is based in Hong Kong and has an extensive portfolio of audio and video
products. This License Agreement covers North America,


                                     9 of 12


<PAGE>   10


Central America, and South America. Pursuant to this License Agreement, Jiangsu
has agreed to make royalty payments through December 31, 2000, subject to
certain minimum royalty amounts due each year. The products covered by this
License Agreement include various consumer electronics products. This License
Agreement is subject to renewal for additional 3 year periods.

Effective July 1, 1998, the Company entered into a License Agreement and an
Addendum thereto with Logitech Electronics Inc. ("Logitech") of Ontario, Canada
whereby the Company licensed to Logitech the right to sell multimedia/computer
speakers under the Koss brand name. This License Agreement covers North America
and certain countries in South America and Europe. This License Agreement
extends for 5 years and includes a 5 year renewal option at the Company's
discretion. This License Agreement requires royalty payments by Logitech through
June 30, 2003, subject to certain minimum royalty amounts due each year.

Year 2000

The Company has implemented a comprehensive Year 2000 initiative to identify and
address issues associated with the Year 2000. A team of internal staff is
managing the initiative, along with the assistance of outside consultants.

The Company has completed the assessment phase of both its information
technology and non-information technology systems associated with the Year 2000.
The assessment indicated that several of the Company's systems would be
vulnerable to Year 2000 issues. The Company is in the process of remedying the
systems identified as vulnerable during the assessment phase.  The Company does
not, however, anticipate any material adverse effects with respect to its
ability to deliver product to customers.

The Company has been working with its significant suppliers and financial
institutions to ascertain their Year 2000 readiness and whether or not those
parties have appropriate plans to remedy Year 2000 issues with their systems
that may impact the Company's operations. The Company has communicated in
writing, a Year 2000 compliance letter and survey, to all of its customers with
annual sales greater than $10,000 as well as to the Company's significant
suppliers and vendors.

The Company's Year 2000 initiative is expected to be completed prior to December
31, 1999. The Company has not identified a need to develop an extensive
contingency plan for non-remedied Year 2000 issues. In the event of any adverse
conditions caused by unforeseen Year 2000 issues, the Company will devote the
necessary resources to resolve any significant Year 2000 issues in a timely
manner. Based on responses received to date, the Company is not anticipating any
significant problems with its customers, suppliers, or vendors as a result of
the Year 2000.

The Company's assessments to date indicate the cost of the Year 2000 initiative
is estimated to be $80,000.

The statements set forth above with respect to Year 2000 issues are
forward-looking statements and are based on the Company's best estimates.
Factors that may cause the actual results to differ include the availability and
retention of skilled professionals and the ability to identify and respond to
all Year 2000 issues.


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<PAGE>   11


PART II  OTHER INFORMATION

Item 4   Submission of Matters to Vote of Security-Holders

         (a) On October 21, 1999 an Annual Meeting of Stockholders was
             held.

         (b) Proxies for the election of directors were solicited
             pursuant to Regulation 14. There was no solicitation in
             opposition to management's nominees, and all such nominees
             were elected.

         (c) There were 2,682,669 shares of common stock eligible to
             vote at the Annual Meeting, of which 2,450,924 shares were
             present at the Annual Meeting in person or by proxy, which
             constituted a quorum. The following is a summary of the
             results of the voting:

<TABLE>
<CAPTION>

                                                Number of Votes      Broker
                                                ---------------     ---------
                                              For        Withheld   Non-Votes
                                              ---        --------   ---------
Nominees for 1-year terms ending in 2000:
<S>                                        <C>           <C>          <C>
John C. Koss                                2,420,167     30,757       0
Thomas L. Doerr                             2,420,491     30,433       0
Victor L. Hunter                            2,420,304     30,620       0
Michael J. Koss                             2,420,357     30,567       0
Lawrence S. Mattson                         2,420,289     30,635       0
Martin F. Stein                             2,421,657     29,267       0
John J. Stollenwerk                         2,421,486     29,438       0
</TABLE>


<TABLE>
<CAPTION>
                                               Number of Votes             Broker
                                               ---------------             ------
                                            For      Against    Abstain  Non-Votes
                                            ---      -------    -------  ---------
<S>                                      <C>         <C>        <C>         <C>
Appointment of
PricewaterhouseCoopers LLP
as independent auditors
for the year ended
June 30, 2000                             2,424,394    2,233     24,297      0
</TABLE>


Item 6   Exhibits and Reports on Form 8-K

         (a)  Exhibits Filed
              27 Financial Data Schedule

         (b)  Reports on Form 8-K
              There were no reports on Form 8-K filed by the Company during
              the period covered by this report.


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<PAGE>   12


                                   Signatures

                  Pursuant to the requirements of the Securities and Exchange
                  Act of 1934, the Registrant has duly caused this report to be
                  signed on its behalf by the undersigned thereunto authorized.


                                    KOSS CORPORATION



                  Dated:            /s/ Michael J. Koss
                        ------      -------------------
                                    Michael J. Koss
                                    Vice Chairman, President,
                                    Chief Executive Officer,
                                    Chief Financial Officer

                  Dated:            /s/ Sue Sachdeva
                        ------      ----------------
                                    Sue Sachdeva
                                    Vice President--Finance







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<PAGE>   13


                                   Signatures

                  Pursuant to the requirements of the Securities and Exchange
                  Act of 1934, the Registrant has duly caused this report to be
                  signed on its behalf by the undersigned thereunto authorized.


                                    KOSS CORPORATION



                  Dated:
                         ------     ------------------------
                                    Michael J. Koss
                                    Vice Chairman, President,
                                    Chief Executive Officer,
                                    Chief Financial Officer



                  Dated:
                         ------     ------------------------
                                    Sue Sachdeva
                                    Vice President--Finance



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