<PAGE>   1
                                                                  EXHIBIT 10.20

                              ROCKFORD CORPORATION


              CONVERTIBLE SUBORDINATED DEBENTURE PURCHASE AGREEMENT

                                   May 1, 1995

To the Purchasers of
Rockford Corporation
Convertible Subordinated Debentures
Identified on Exhibit A Below

Ladies and Gentlemen:

         The undersigned Rockford Corporation, an Arizona corporation (the
"Company"), agrees with you as follows:

1.       PURCHASE AND SALE OF DEBENTURES.

         1.1      Authorization by the Company. The Company has authorized the
                  issue and sale to you of its 8.5% Convertible Subordinated
                  Debentures (the "Debentures"), with the terms and rights set
                  forth in the form of the Debenture attached to this Agreement
                  as Exhibit B. The Debentures will be in the total principal
                  amount, and will be divided among you, as shown on Exhibit A.

         1.2      Agreement of Purchase and Sale. Subject to the terms and
                  conditions of this Agreement, and on the basis of the
                  representations and warranties set forth herein, the Company
                  will sell to you and you will purchase from the Company, on
                  the Closing Date, the principal amount of the Debentures set
                  forth on Exhibit A at a price equal to the principal amount.
                  The Debentures will be divided among you as set forth on
                  Exhibit A.

         1.3      Closing of Purchase and Sale. The purchase and sale of the
                  Debentures (the "Closing") will take place at the office of
                  Lewis and Roca, 40 North Central Avenue, Phoenix, Arizona, on
                  May 1, 1995 (or on another date if you and the Company agree
                  in writing) (the "Closing Date"). On the Closing Date, the
                  Company will deliver to you Debentures against payment of the
                  purchase price by your certified or cashiers checks payable to
                  the order of the Company or wire transfer of immediately
                  available federal funds. The Debentures purchased by you will
                  be evidenced by appropriate certificates issued to each of
                  you, in definitive form as set forth in Exhibit B, divided
                  among you as set forth in Exhibit B, and registered in your
                  names or the names of your nominee or nominees.

2.       REPRESENTATIONS AND WARRANTIES BY THE COMPANY. The Company represents
         and warrants to you as follows:
<PAGE>   2
         2.1      Organization. The Company is a corporation duly organized,
                  validly existing and in good standing under the laws of
                  Arizona. The Company has all requisite corporate power and
                  authority to own, lease, and operate its properties and to
                  carry on its business as now conducted and as proposed to be
                  conducted. On the Closing Date the Company will be duly
                  qualified or authorized to do business and in good standing in
                  each jurisdiction where the character of the property owned or
                  leased or the nature of the business transacted makes such
                  qualification or authorization necessary. The Company has no
                  subsidiaries or any direct or indirect interest (by way of
                  stock ownership or otherwise) in any firm or business except
                  as disclosed in Schedule 2.1. The Company has furnished you
                  with certified copies of its Certificate of Incorporation and
                  By-Laws, as amended to the date hereof.

         2.2      Capitalization. The Company's authorized and outstanding
                  capital stock, and the outstanding securities convertible into
                  the Company's capital stock, is as set forth in Schedule 2.2.
                  All of the issued and outstanding shares of the Company's
                  Common Stock are duly authorized, validly issued, fully paid
                  and nonassessable. The Company has reserved the number of
                  shares of its Common Stock shown on Exhibit A for issuance
                  upon conversion of the Debentures. All outstanding shares of
                  the Common Stock of the Company were issued in compliance with
                  all applicable Federal and state securities or "blue sky"
                  laws. There are in existence or contemplated no options,
                  warrants, agreements or similar rights granted by the Company
                  for the issue or sale by it of any securities, other than the
                  transactions contemplated by this Agreement and the
                  transactions disclosed in Schedule 2.2.

         2.3      Financial Position. The Company's Balance Sheets as at
                  September 30, 1993 and 1994, and Statements of Income and
                  Retained Earnings and of changes in Financial Position for its
                  two fiscal years then ended, as audited by Ernst & Young LLP
                  and in the form set forth in Schedule 2.3, are true and
                  correct in all material respects as at such dates and for the
                  periods then ended.

         2.4      Duly Issued. The shares of the Common Stock issuable upon
                  conversion of the Debentures, upon such conversion, will be
                  validly issued, fully paid and nonassessable.

         2.5      Authorization. The Company has duly authorized, executed and
                  delivered this Agreement. This Agreement constitutes the valid
                  and binding agreement of the Company, enforceable in
                  accordance with its terms except as enforcement may be limited
                  by bankruptcy, insolvency, moratorium and equitable principles
                  applicable to creditors generally. The Company has full power
                  and lawful authority to issue and sell the Debentures on the
                  terms and conditions set forth in this Agreement and to issue
                  the Common Stock issuable upon conversion of the Debentures.

         2.6      Compliance with Laws. The Company is in compliance with all
                  laws, regulations and orders applicable to its business and
                  properties, and has all necessary permits and licenses.


                                      -2-
<PAGE>   3
         2.7      Governmental Consents. Neither the execution and delivery of
                  this Agreement, nor the performance of the terms or
                  consummation of the transactions contemplated by the Company
                  under this Agreement, require any consent, approval,
                  authorization, or other order of any court, regulatory body,
                  administrative agency, or other governmental body, or any
                  filings pursuant to the Securities Act of 1933, as amended
                  (the "Securities Act"), or the securities laws of any state
                  other than those obtained prior to and effective as of the
                  Closing Date. Neither the Company nor any agent acting on its
                  behalf has offered, or will offer, to sell (or has solicited
                  or will solicit any offer to buy) the Debentures or any shares
                  of the Common Stock of the Company issuable upon the
                  conversion of the Debentures so as to require the registration
                  of any of such securities under the Securities Act other than
                  as contemplated by Article 4 of this Agreement. Based in part
                  on your representations which are set forth in Article 3 of
                  this Agreement, the offer, sale, and issuance of the
                  Debentures pursuant to this Agreement and the shares of the
                  Common Stock of the Company to be issued upon conversion of
                  the Debentures are exempt from the registration requirements
                  of the Securities Act.

3.       REPRESENTATIONS AND WARRANTIES OF PURCHASERS. You represent and warrant
         to the Company and to the other purchasers of the Debentures:

         3.1      Investment Representation. You are acquiring the Debentures,
                  together with the shares of the Common Stock issuable upon the
                  conversion of the Debentures, for your own account and not
                  with a view to or for sale in connection with any
                  distribution. You have no present intention of distributing
                  the Debentures or the shares of the Common Stock issuable upon
                  the conversion of the Debentures.

         3.2      Stock Not Registered. You acknowledge that;

                  (a)      neither the Debentures nor the shares of the Common
                           Stock issuable upon conversion of the Debentures have
                           been registered under the Securities Act or
                           applicable state securities laws on the ground that
                           the issuance to you is exempt from registration under
                           the Securities Act;

                  (b)      the Company's reliance on such exemption is
                           predicated on your representations;

                  (c)      the Debentures and shares of Common Stock must be
                           held indefinitely unless the offer and sale are
                           registered under the Securities Act, and applicable
                           state securities laws, or an exemption from
                           registration is available. In particular, you
                           acknowledge that the Debentures, and any Common Stock
                           issued on conversion, may not be sold pursuant to
                           Rule 144 promulgated under the Securities Act unless
                           all of the conditions of such rule are met. Among the
                           conditions for use of Rule 144 is the availability to
                           the public of current information about the Company.
                           Such information is not now available and the Company
                           has no present plans to make such information
                           available;


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<PAGE>   4
                  (d)      in the absence of an effective registration statement
                           covering the Debentures, or any Common Stock issued
                           on conversion thereof, you will sell, transfer, or
                           otherwise dispose of the Debentures, or any Common
                           Stock issued on conversion, only in a manner
                           consistent with your representations and then only in
                           accordance with the provisions of Section 4.1 of this
                           Agreement;

                  (e)      any certificate representing the Debentures, and the
                           shares of the Common Stock issuable upon conversion
                           of the Debentures, will bear the legend set forth in
                           Section 4.2 and that the Company may issue
                           appropriate "stop transfer" instructions to its
                           transfer agent, if any, with respect to such shares
                           or make appropriate notations to such effect in its
                           own stock transfer records; and

                  (f)      any certificate representing the Debentures, and the
                           shares of the Common Stock issuable upon conversion
                           of the Debentures, may bear any legends required by
                           applicable state securities laws.

3.3               Investment Experience. You (a) have such knowledge and
                  experience in financial and business matters that you are
                  capable of evaluating the merits and risks of the purchase of
                  the Debentures, (b) have a net worth significantly in excess
                  of the amount of your investment in the Debentures and are
                  able to bear the economic risk of the purchase of the
                  Debentures, and (c) have had access to information with
                  respect to the Company necessary to permit you to make an
                  informed investment decision.

3.4               Organization. On the date of this Agreement, and on the
                  Closing Date, (a) if you are a corporation, you are duly
                  organized and validly existing under the laws of your state of
                  incorporation, you are and will be in good standing under such
                  laws and you have the requisite corporate power and authority
                  to enter into this Agreement, (b) if you are a general or
                  limited partnership, you are and will be a general or limited
                  partnership duly organized and validly existing under the laws
                  of your state of formation, and you are and will be in good
                  standing under such laws, and you have and will have all
                  requisite partnership power and authority to enter into this
                  Agreement, (c) you have duly authorized, executed and
                  delivered this Agreement to the Company, and (4) upon
                  execution and delivery by the Company, this Agreement
                  constitutes your valid and binding agreement, enforceable in
                  accordance with its terms. Enforceability of any agreement may
                  be limited by bankruptcy, insolvency, moratorium and equitable
                  principles applicable to creditors generally.

4.       SECURITIES ACT AND RELATED MATTERS.

         4.1      Transfer Restrictions. You will not offer for sale, sell or
                  transfer all or any part of the Debentures, or the shares of
                  the Common Stock or other securities into which the Debentures
                  are convertible, unless (1) the sale is registered under the
                  Securities Act, and all other qualifications and proceedings
                  required under other


                                      -4-
<PAGE>   5
                  state or federal laws or regulations have been obtained or
                  taken, or (2) an exemption from registration or qualification
                  under the Securities Act and any applicable state securities
                  or "blue sky" laws is available and the Company has received
                  an opinion of counsel reasonably satisfactory to the Company
                  that registration is not required.

         4.2      Legend on Certificate. Each certificate representing the
                  Debentures, or any shares of the Common Stock or other
                  securities issued upon conversion of the Debentures, will bear
                  a legend in substantially the following form (unless the
                  Company has received in the opinion of counsel reasonably
                  satisfactory to the Company that a legend is not necessary):

                           "THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE
                           NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
                           AS AMENDED, OR THE SECURITIES LAW OF ANY STATE. THE
                           SECURITIES MAY NOT BE SOLD, TRANSFERRED, PLEDGED OR
                           HYPOTHECATED IN THE ABSENCE OF EFFECTIVE REGISTRATION
                           STATEMENTS OR AN OPINION OF COUNSEL ACCEPTABLE TO
                           THIS COMPANY THAT REGISTRATION IS NOT REQUIRED."

                  Each certificate will also bear any legends required by
                  applicable state securities laws. In this Agreement
                  "Restricted Security" means the Debentures and shares of the
                  Common Stock or other securities issued upon conversion of the
                  Debentures and represented by certificates bearing the legend
                  set forth in this Section 4.2 and "Restricted Stock" means
                  shares of Common Stock issued upon conversion of the
                  Debentures and represented by certificates bearing the legend
                  set forth in this Section 4.2.

         4.3      Registration Proposed by Company.

                  (a)      Notice of Registration. If the Company proposes to
                           register any of its securities under the Securities
                           Act it will give written notice to every holder of a
                           Restricted Security except that the Company need not
                           give notice of (1) a registration solely to implement
                           an employee benefit plan, (2) a transaction to which
                           Rule 145 under the Securities Act is applicable, or
                           (3) a registration using any form that does not
                           permit secondary sales of securities.

                  (b)      Participation by Holders. If any holder of a
                           Restricted Security delivers to the Company, within
                           30 days of the Company's notice to the holders, a
                           notice stating the number of shares of Restricted
                           Stock to be registered and the intended method of
                           disposition, the Company will use its best efforts to
                           register under the Securities Act the shares of
                           Restricted Stock requested to be registered (1) in
                           connection with the registrations of securities to be
                           sold for the Company's account, (2) at its own
                           expense to


                                      -5-
<PAGE>   6
                           the extent provided in Section 4.5, and (3) to the
                           extent required to permit disposition in accordance
                           with the intended method.

                 (c)       Limitations on Company's Obligation. If the Company's
                           proposed registration relates to an underwritten
                           public offering by the Company, the Company is not
                           required to register shares of Restricted Stock
                           unless the requesting holders agree to include them
                           in the underwriting. If the sole or managing
                           underwriter of the offering determines that the
                           aggregate number of shares of Restricted Stock
                           included in the registration should be limited due to
                           market conditions or the necessity of including
                           shares to be sold for the account of the Company,
                           then each holder who has requested that shares of
                           Restricted Stock be included may sell only a prorata
                           portion of shares of Restricted Stock.

         4.4      Registration Requested by Purchasers.

                  (a)       Request for Registration. The holder or holders of
                            50% of the Restricted Securities may request that
                            the Company register Restricted Stock at any time
                            (1) before the Company gives written notice of its
                            intention to register its securities under Section
                            4.3 (but only if the registration becomes effective
                            within six months after the Company gives the
                            notice) and (2) after the later of (i) May ___, 1997
                            or (ii) 12 months after the effective date of any
                            prior registration statement covering shares of the
                            Company's stock. In determining whether 50% of the
                            holders of Restricted Securities have made a
                            request, Restricted Stock and other securities
                            issued upon conversion of the Debentures will be
                            counted on the basis of the amount of Debentures
                            from which they were converted.

                   (b)      Content of Request. The request must state the
                            number of shares of Restricted Stock to be
                            registered and the intended method of disposition.
                            The Company is not obligated to file a registration
                            statement if the expected price to the public of the
                            offering of Restricted Stock is less than
                            $15,000,000.

                   (c)      Required Registration. Upon receipt of a request
                            that satisfies the requirements stated above, the
                            Company will upon one occasion (1) promptly give
                            written notice of the proposed registration to every
                            other holder of Restricted Securities and (2) as
                            expeditiously as possible (and in any event within
                            90 days) use its best efforts, at its own expense to
                            the extent provided in Section 4.5, to effect
                            registration under the Securities Act of

                           (i)      the sale of the Restricted Stock which is
                                    the subject of the written request referred
                                    to above, and


                                      -6-
<PAGE>   7
                           (ii)     all other Restricted Stock whose holders
                                    make written request for registration to the
                                    Company within 30 days after the Company
                                    gives them notice of the proposed
                                    registration

                  all to the extent required to permit the disposition by the
                  holders of the securities so registered. In connection with
                  any registration, the Company will execute any required
                  undertakings to file post-effective amendments.

                  (d)      Limitations on Company's Obligation. The Company is
                           not obligated under this Section 4.4 after (1) one
                           registration, filed pursuant to any holder's request
                           under this Section 4.4 (other than a delayed
                           registration as described below), has become
                           effective or (2) you and your permitted transferees
                           hold less than 10% of the Restricted Securities
                           initially issued and sold pursuant to this Agreement.

                  (e)      Delay of Registration. If, within ten days after the
                           Company receives a request for registration under
                           subsection (a), the Company furnishes a certificate
                           stating that the Company intends to file within 60
                           days a registration statement for an underwritten
                           public offering of securities for the Company's
                           account, then the Company is not obligated to file a
                           registration under this Section 4.4 for six months
                           from the date of the Company's certificate. The
                           Company must make all reasonable efforts to cause the
                           registration statement for the underwritten public
                           offering to become effective as soon as reasonably
                           practicable. The Company may invoke this subsection,
                           and delay a registration requested under Section 4.4,
                           only one time.

         4.5      Costs and Expenses. The Company will pay all its costs and
                  expenses in connection with a registration of securities under
                  Sections 4.3 or 4.4, including Federal and state registration
                  and filing fees, printing expenses (including a reasonable
                  number of preliminary and final prospectuses, post-effective
                  amendments, and supplements requested by the holders of
                  Restricted Stock), and the fees and disbursements of counsel,
                  independent accountants, and other experts of the Company. The
                  Company will not pay underwriter's discounts and commissions
                  or the fees and disbursements of counsel, independent
                  accountants, or other experts of the holders of Restricted
                  Stock. The Company will use its best efforts to keep effective
                  any registration for the period reasonably necessary to effect
                  disposition in accordance with the intended methods described
                  in the requests for registration. If the Company is requested
                  or required to maintain the registration effective for more
                  than six months the holders of securities who have requested
                  that effectiveness be maintained, in order to continue with
                  the distribution, will pay (in such proportions as they may
                  agree upon) all out-of-pocket expenses of the Company incurred
                  in maintaining effectiveness after the initial six-month
                  period.

         4.6      Information. The holders of Restricted Stock covered by a
                  registration statement under Sections 4.3 or 4.4 will furnish
                  to the Company (in writing) any


                                      -7-
<PAGE>   8
                  information regarding them, Restricted Securities held by
                  them, and the intended method of disposition of the Restricted
                  Stock as the Company reasonably requests or as is required in
                  connection with the registrations under Sections 4.3 or 4.4.

         4.7      Blue Sky Registrations. In any registration under this Section
                  4, the Company will use its best efforts to register or
                  qualify the Restricted Stock for sale under the securities
                  laws of those states in which registration or qualification is
                  required, except that the Company is not required (a) to
                  execute a general consent to service or (b) to qualify to do
                  business in any state.

         4.8      Lockup Agreement. In connection with any registration of the
                  Company's securities, upon request of the underwriters
                  managing the offering, each holder of Restricted Securities
                  will execute an agreement not to sell, make a short sale of,
                  loan, grant an option for the purchase of, or otherwise
                  dispose of any Restricted Stock (other than shares included in
                  the registration or shares sold with the underwriters' prior
                  written consent) for up to 90 days after the effective date of
                  the registration.

         4.9      Transferability. If the requirements of Section 4.1 have been
                  satisfied for the sale or transfer of a Restricted Security,
                  the transferee will be entitled to the rights and benefits of,
                  and will be subject to the requirements of, Sections 4.1
                  through 4.8.

5.       COMPANY'S AFFIRMATIVE COVENANTS. The Company will comply with the
         following requirements unless holders of more than 50% of the
         outstanding Restricted Securities agree otherwise in writing. These
         requirements will terminate upon the earlier of (1) the closing date of
         an underwritten public offering of the Company's common stock pursuant
         to an effective registration statement under the Securities Act or (2)
         the date when less than 25% of the Restricted Securities are held by
         the original holders of the Debentures or their permitted transferees.
         These requirements may be amended by a written agreement between the
         Company and holders of more than 50% of the outstanding Restricted
         Securities. The financial covenants below are substantially the same as
         the covenants established in the revolving credit facility entered into
         between the Company and Norwest Business Credit, Inc. ("NBCI") as of
         May 1994; you agree that, upon any revision or refinancing of the
         Company's principal credit facility it is your intention to consent to
         the amendment of the financial covenants in this Agreement so that they
         are consistent with the terms of the new or revised credit facility.

         5.1      Reporting Requirements. The Company will deliver to you each
                  of the following:

                  (a)      Annual Financial Statements. No later than 90 days
                           after the end of each Company fiscal year, audited
                           financial statements including

                           (1)      the Company's balance sheet as at the end of
                                    the fiscal year, and

                           (2)      the related statements of income, retained
                                    earnings, and cash flows of the Company for
                                    the fiscal year.


                                      -8-
<PAGE>   9
                           The financial statements will be in reasonable detail
                           and prepared in accordance with generally accepted
                           accounting principles consistently applied. The
                           financial statements will be accompanied by the
                           unqualified opinion of independent public accountants
                           selected by the Company and a certificate of the
                           Company's chief financial officer stating (i) that
                           the financial statements were prepared in accordance
                           with generally accepted accounting principles
                           consistently applied, (ii) whether such officer has
                           knowledge of the occurrence of any default under this
                           Agreement and, if so, a statement in reasonable
                           detail of the nature of the default, and (iii)
                           computations showing whether the Company is in
                           compliance with the financial covenants set forth in
                           this Agreement;

                  (b)      Shareholder Information. Promptly upon their
                           distribution, copies of all financial statements,
                           reports and proxy statements the Company sends to its
                           stockholders;

                  (c)      SEC Filings. Promptly after their filing, copies of
                           all regular and periodic financial reports the
                           Company files with the Securities and Exchange
                           Commission or any national securities exchange;

                  (d)      Notice of Violations. Promptly upon knowledge
                           thereof, notice of the Company's violation of any
                           law, rule or regulation which could materially and
                           adversely affect the Company's business or financial
                           condition; and

                  (e)      Other Information. From time to time, with reasonable
                           promptness, all other materials, reports, records, or
                           information relating to Company's financial
                           condition, operations, or affairs as you may
                           reasonably request.

         5.2      Books and Records. The Company will keep accurate books,
                  records, and accounts of the Company's business and financial
                  condition.

         5.3      Compliance with Laws; Environmental Indemnity. The Company
                  will

                  (a)      comply with the requirements of applicable laws and
                           regulations whose violation would materially and
                           adversely affect the Company's business or financial
                           condition, and

                  (b)      comply with all applicable Environmental Laws and
                           obtain any permits, licenses, or approvals required
                           by any such Environmental Laws. The Company will
                           indemnify, defend, and hold you harmless from and
                           against any claims, loss, or damage resulting from
                           any past, present, or future existence, use,
                           handling, storage, transportation, or disposal of any
                           hazardous waste, hazardous substance, or toxic
                           substance by the Company or on property owned,
                           leased, or controlled by the Company. This
                           indemnification agreement will survive the
                           termination of this Agreement and payment of the
                           indebtedness hereunder.


                                      -9-
<PAGE>   10
         5.4      Payment of Taxes and Other Claims. The Company will pay or
                  discharge, when due,

                  (a)      all taxes, assessments, and governmental charges
                           levied or imposed upon it, upon its income or
                           profits, or upon any properties belonging to it. Such
                           amounts will be paid before the date when penalties
                           attach thereto,

                  (b)      all federal, state, and local taxes required to be
                           withheld by it, and

                  (c)      all lawful claims for labor, materials and supplies
                           which, if unpaid, might by law become a lien or
                           charge upon any properties of the Company.

                  The Company is not required to pay any tax, assessment,
                  charge, or claim whose amount, applicability or validity is
                  being contested in good faith by appropriate proceedings.

         5.5      Maintenance of Properties. The Company will maintain the
                  properties used in its business in good condition, repair, and
                  working order (normal wear and tear excepted). The Company
                  will replace or repair worn, defective, or broken parts, but
                  nothing in this section prevents the Company from
                  discontinuing the operation and maintenance of any of its
                  properties if such discontinuance is in its judgment
                  desirable.

         5.6      Insurance. The Company will obtain and at all times maintain
                  insurance with insurers believed by the Company to be
                  responsible and reputable, in such amounts and against such
                  risks as is usually carried by companies engaged in similar
                  business and owning similar properties in the same general
                  areas in which the Company operates.

         5.7      Preservation of Corporate Existence. The Company will preserve
                  and maintain its corporate existence and all rights,
                  privileges, and franchises necessary or desirable in the
                  conduct of its business. The Company will conduct its business
                  in an orderly, efficient, and regular manner.

         5.8      Book Net Worth. The Company will maintain on the last day of
                  each quarter occurring in each of the periods set forth below,
                  a Book Net Worth (as that term is defined in the Company's
                  credit agreement with NBCI dated May 3, 1994) greater than or
                  equal to the amount set forth opposite such period:

<TABLE>
<CAPTION>
                           PERIOD                                      BOOK NET WORTH
                           ------                                      --------------
<S>                                                                    <C>
                  Through June 29, 1995                                ($2,650,000)
                  June 30, 1995 through September 29, 1995             ($1,000,000)
                  September 30, 1995 through December 30, 1995         ($  800,000)
                  December 31, 1995 through March 30, 1996             ($  900,000)
                  March 31, 1996 through June 29, 1996                 ($  400,000)
                  June 30, 1996 through September 29, 1996             $1,000,000
</TABLE>


                                      -10-
<PAGE>   11
<TABLE>
<S>                                                                    <C>
                  September 30, 1996 and thereafter                    $1,600,000
</TABLE>

         5.9      Earnings Before Interest and Taxes. The Company will maintain
                  on each date set forth below operating income (determined in
                  accordance with generally accepted accounting principles but
                  before any deduction for interest expenses and income taxes
                  and calculated for the twelve months ending on such date)
                  greater than or equal to the amount set forth opposite such
                  date:

<TABLE>
<CAPTION>
                          DATE                                            EBIT
<S>                                                                    <C>
                  June 30, 1995                                        $3,600,000
                  September 30, 1995                                   $3,800,000
                  December 31, 1995                                    $3,800,000
                  March 31, 1996                                       $4,000,000
                  June 30, 1996                                        $4,300,000
                  September 30, 1996 and each fiscal quarter           $4,300,000
                           end thereafter
</TABLE>

         5.10     Interest Coverage. The Company will maintain on each date set
                  forth below, the ratio of (i) the sum of its pre-tax net
                  income, to (ii) interest expense (in each case determined in
                  accordance with generally accepted accounting principles, and
                  calculated for the twelve months ending on such date) greater
                  than or equal to the ratio set forth opposite such date:

<TABLE>
<CAPTION>
                          DATE                                           RATIO
                          ----                                           -----
<S>                                                                    <C>
                  June 30, 1995                                        2.00 to 1
                  September 30, 1995                                   2.00 to 1
                  December 31, 1995                                    2.00 to 1
                  March 31, 1996                                       2.00 to 1
                  June 30, 1996                                        2.00 to 1
                  September 30, 1996 and each fiscal quarter           2.00 to 1
                           end thereafter
</TABLE>

         5.11     Minimum Debt Service Coverage. The Company will maintain on
                  each date set forth below, the ratio of (i) the sum of its
                  after-tax net income, depreciation, and amortization expense
                  and interest expense, to (ii) the sum of its interest, capital
                  expenditures, and current maturities of long term debt
                  (excluding as long term debt, the indebtedness of the Company
                  to NBCI incurred pursuant to the credit agreement between
                  Company and NBCI, or any replacement of such indebtedness) (in
                  each case determined in accordance with generally accepted
                  accounting principles, and calculated for the twelve months
                  ending on such date) greater than or equal to the ratio set
                  forth opposite such date:


                                      -11-
<PAGE>   12
<TABLE>
<CAPTION>
                          DATE                                          RATIO
                          ----                                          -----
<S>                                                                   <C>
                  June 30, 1995                                       1.50 to 1
                  September 30, 1995                                  1.50 to 1
                  December 31, 1995                                   1.50 to 1
                  March 31, 1996                                      1.50 to 1
                  June 30, 1996                                       1.50 to 1
                  September 30, 1996 and each fiscal quarter          1.50 to 1
                           end thereafter
</TABLE>

6.       COMPANY'S NEGATIVE COVENANTS. The Company will comply with the
         following requirements unless holders of more than 50% of the
         outstanding Restricted Securities agree otherwise in writing. These
         requirements will terminate upon the earlier of (1) the closing date of
         an underwritten public offering of the Company's common stock pursuant
         to an effective registration statement under the Securities Act or (2)
         the date when less than 25% of the Restricted Securities are held by
         the original holders of the Debentures or their permitted transferees.
         These requirements may be amended by a written agreement between the
         Company and holders of more than 50% of the outstanding Restricted
         Securities.

         6.1      Dividends and Stock Repurchases. The Company will not declare
                  or pay any dividends (other than dividends payable solely in
                  stock of the Company) on any class of its stock or make any
                  payment on account of the purchase, redemption or other
                  retirement of any shares of such stock or make any
                  distribution in respect thereof, either directly or
                  indirectly. If the Company becomes an S Corporation (with your
                  consent and after first providing such supporting
                  documentation as you may request) the Company may pay
                  dividends equal to the amount of state and federal income tax
                  which would be due for each shareholder with respect to income
                  allocated to each shareholder as a result of the Company's
                  status as an S Corporation at the highest marginal income tax
                  rate for federal and state income tax purposes (after taking
                  into account any deduction for state income taxes in
                  calculating the federal income tax liability and for the state
                  or states in which each shareholder is liable for income
                  taxes).

         6.2      Sale or Transfer of Assets; Suspension of Business Operations.
                  The Company will not sell, lease, assign, transfer, or
                  otherwise dispose of (a) the stock of any domestic Subsidiary
                  or (b) all or a substantial part of its assets to any other
                  person (other than the sale of Inventory in the ordinary
                  course of business) and will not liquidate, dissolve or
                  suspend business operations. The Company will not transfer any
                  material property without receipt of full and adequate
                  consideration. This Agreement does not restrict any sale or
                  other disposition of Company subsidiaries organized in
                  connection with the Company's operations outside the United
                  States.

         6.3      Accounting. The Company will not adopt any material change in
                  accounting principles other than as required by generally
                  accepted accounting principles. The Company will not adopt,
                  permit or consent to any change in its fiscal year.

7.       CONDITIONS OF OBLIGATION TO ISSUE AND SELL. The obligation of the
         Company to issue and sell the Debentures to you at the Closing is
         subject to the condition that the


                                      -12-
<PAGE>   13
         representations and warranties stated in Article 3 of this Agreement
         must be correct when made and as of the time of the Closing.

8.       CONDITIONS OF OBLIGATION TO PURCHASE. Your obligation to purchase and
         pay for the Debentures at the Closing is subject to the following
         conditions:

         8.1      Representations and Warranties Correct. The representations
                  and warranties contained in Article 2 of this Agreement must
                  be correct when made and as of the time of the Closing.

         8.2      Performance. The Company must have performed and complied with
                  all agreements and conditions contained in this Agreement and
                  required to be performed or complied with by it prior to or at
                  the Closing.

         8.3      Closing Certificate. The Company must have delivered to you a
                  certificate, dated the Closing Date, certifying that the
                  conditions specified in Sections 8.1 and 8.2 have been
                  fulfilled.

         8.4      Directors and Officers. The persons named in Schedule 8.4 must
                  have been duly elected to the respective positions of
                  directors and officers of the Company as set forth in Schedule
                  8.4.

         8.5      Opinion of Counsel. The Company must have delivered to you the
                  opinion of Lewis and Roca in substantially the form set forth
                  in Schedule 8.5.

9.       MISCELLANEOUS.

         9.1      Expenses. The parties will each pay their own expenses
                  incurred in connection with the purchase and sale of the
                  Debentures.

         9.2      Survival of Representations and Warranties. All covenants,
                  agreements, representations and warranties made in writing in
                  this Agreement will survive the execution and delivery of this
                  Agreement and the issuance, sale, and delivery of the
                  Debentures.

         9.3      Binding Effect. All covenants, agreements, representations,
                  and warranties in this Agreement bind, and inure to the
                  benefit of, the respective heirs, legal representatives,
                  successors, and assigns of the parties. The rights of any
                  transferee of a Restricted Security, however, are subject to
                  compliance with Section 4.1.

         9.4      Notices. All notices and other communications under this
                  Agreement must be in writing. They will be deemed given and
                  received when delivered or five days after deposit in the
                  United States mail, first class postage prepaid, addressed to
                  Company at:

                           648 South River Drive
                           Tempe, Arizona 85281


                                      -13-
<PAGE>   14
                           Attention:       President

                           with a copy to:

                           Lewis and Roca
                           40 North Central Avenue, Suite 1500
                           Phoenix, Arizona 85004
                           Attention:       Kevin Olson, Esq.

                  and addressed to you at the address stated in Exhibit A. Any
                  party may change the person, officer, or address to which
                  notices and communications are to be sent to it by giving
                  notice.

         9.5      Amendments and Waivers. Neither this Agreement nor any of its
                  terms may be changed, waived, discharged, or terminated except
                  in a writing signed by the Company and by holders of more than
                  50% of the outstanding Restricted Securities.

         9.6      Controlling Law. This Agreement is being executed and
                  delivered, and the Debentures are being delivered, in Arizona
                  and will be governed by the laws of Arizona.

         9.7      Counterparts. This Agreement may be executed in several
                  counterparts and each counterpart, when executed and delivered
                  and whether or not each counterpart is executed by all the
                  parties, will constitute an original instrument. All the
                  separate counterparts will together constitute this Agreement
                  and are parts of the same instrument.

         If you are in agreement with the foregoing, please sign the form of
acceptance appearing as part of the Subscription Agreement for purchase of the
Debentures and return the same to the Company. This Agreement will become a
binding agreement between you and the undersigned upon the Company's acceptance
of your executed Subscription Agreement for the Debentures.

                                            Yours very truly,


                                      -14-
<PAGE>   15
                                            ROCKFORD CORPORATION



                                            By: /s/
                                                --------------------------------
                                                            President


                                            Attest /s/
                                                   -----------------------------
                                                        Assistant Secretary