The Subwoofer DIY Page - Discussion Forum

[ The Subwoofer DIY Page - Discussion Forum ] [ FAQ ]

[Previous Message] [Next Message]

Date: December 21, 2002 at 20:37:59
From: Adrian Mack, [dialup-196-218.wasp.net.au]
Subject: Re: Questions about mathmatical boxes....

URL: NEW! 18 Sound Sub DIY Project and Peerless XLS 12


Well.... it depends. Using an alignment such as SBB4, QB3, SC4, C4 or whatever, it gurantees you a specific set of characteristics for your design (describes box size, tuning and response curve) - it is a good way though to get an idea of the response without actually modeling the enclosure. These alignments can be calculated using a set of design tables (which are available in the LDC for example).

These have flat responses (and use low Qts values):

SBB4 boxes offer good transient response, but have larger box, in return of lower Fb.

SC4 has approx the same size box/F3 as SBB4, but different Fb and lower transient response. Is an extension of the Chebyshev alignment (C4).

QB3 has lower F3 for smaller box size. Transient response is not as good as SBB4 or SC4 though.

The following have non-flat responses (and use higher Qts values).

C4 alignment can be used when there is a low value of ripple (~1db).

BB4 has a peak close to its rolloff, which can be quite large in some cases, which is undesirable. Its like having a high Qtc value of a sealed box (above 1.2 characteristics). This is why bass reflex boxes years and years ago were classified as "boom boxes"

SQB3 is similar to QB3, just uses a higher Qts value.

There are also the descrete alignments B4, BE4, and IB4. Descrete alignments are not usually used as they exist for only a single value of Qts. Box loses also affect the value of this alignment, making it harder to obtain. BE4 has the best transient response out of these three.

Those alignments do not need to be followed, as a good custom enclosure can be designed by yourself (of course) espcially with equaliztion. However they will give you an idea of how your driver will perform based on Qts without modeling it first (obviously a suitable Fs and Vas is needed). It would seem that lower Qts values give a flatter response in a non-equalized design.

Qts will restrict the type of alignments that can be used for a driver.


  • View the previous message in this thread
  • Go to the top of this thread
  • View entire thread
    		•

    Posted with TalkShop version 2.74

    [Previous Message] [Next Message]



    Follow Ups:

    [ The Subwoofer DIY Page - Discussion Forum ] [ FAQ ]