So how does this combination "sound" to you

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Comments

  • JethroJethro Posts: 28
    edited December 2003
    Originally posted by MrDHEJ
    The information here on the Polk site in regards to box volume states: A smaller box will require more power, but produce tighter bass in the whole spectrum, where as a larger volume box will focus more on the lower freq. and be more boomy and louder at a sacrifice to the higher bass freq., but require less power.

    That statement is not totally correct (with regard to sealed boxes, anyway). A sub with tight bass typically has excellent transient response without a lot of overhang or ringing. This is usually attained by using a sealed box alignment at or aroung .707 Qtc. "Boominess" is usually defined as too much upperbass emphasis - a characteristic found in boxes with .9 Qtc or higher (smaller boxes).

    A smaller box will indeed require more power, but it will also have better power handling. When designing an enclosure for SQ purposes, you want a Qtc as close to .707 as possible, while keeping within the driver's excursion limits.

    If you took the MM124's Thiel/Small Parameters.....

    Electrical
    Overall Frequency Response 20Hz - 200Hz
    Nominal Impedance 4 ohms
    Power Handling (continuous) 500 w
    Power Handling (peak) 1000 w
    Efficiency 87 dB
    Voice Coil Diameter: Driver 2" (5.08cm)
    Magnet Weight 66.00 oz.



    Driver Mounting Depth
    Top Mount 6" (15.24cm)
    Bottom Mount 6-1/2" (16.51cm)
    Cut-out
    Driver Cut-out Diameter 11-1/8" (28.26cm)


    Theile/Small Parameters
    Recommended Enclosure Sealed or Band Pass
    Resonant Frequency 27.5 Hz
    Qms 13.06
    Qes 0.476
    Qts 0.46
    Vas 81.12 L / 2.865 cu ft
    Cms 221 Micro Meters
    Bl 14.45 Tesla Meters
    Sd 511 sq cm / 79.21 sq in
    Xmax (mechanical) 1.0
    Le 1.92 mH
    Mms 151 g
    Driver Weight 15.8 pounds
    Pe 500w

    .....and entered them into WinISD Pro, you would find that it could take 600w RMS in 2 cu ft sealed without exceding the 25mm Xmax (Qtc would be .717).

    1.25 cu ft would get you a Qtc of .83, which is on the upper limits of what is considered an SQ alignment.

    .88 cu ft would yield a Qtc of .93, which would have great power handling, but would be a little boomy for SQ purists, unless you had an EQ to tame the boost in response between 60 and 100hz.

    For more information on this, check out The Loudspeaker Design Cookbook by Vance Dickason. The newest edition even has a section on how a car's interior boosts (aka transfer function or cabin gain) the lowest octaves, and how that transfer function varies from vehicle to vehicle.
    Friends don't let friends listen to Bose.
  • JethroJethro Posts: 28
    edited December 2003
    Originally posted by sntnsupermen131
    Jethro, wouldnt by increasing the box size the SQ go down
    im wondering because if it has more air, the sub can not control itself as well b/c its "backbone" is not supportive enough?
    -Cody

    If you go too large, then yes, power handling will be decreased to a point that SQ will suffer due to over-excursion (typically with Qtc's lower than .577, depending on the driver). But, enclosure size is relative - some 12's work well in 6 cu ft+, other 12's work well in less than 1 cu ft.

    For a better explanation than I could ever give, follow this link:

    Sealed Box Tutorial
    Friends don't let friends listen to Bose.
  • MacLeodMacLeod Posts: 14,363
    Nostalgia bump! Hard to tell with the new forum and deleted posts/threads but I think this was one of the first threads I ever posted in here after buying my first set of Polk Audio speakers, MMC690 6x9's for my 2002 Dodge Ram at Circuit City in Temple, Texas in November 2003.

    For some reason I was thinking about this place today and the good times we had 15 years ago. There was about 9 or 10 of us regulars that knew just the basics but were constantly looking for new things to learn. I bet we each started a new thread here every day for every little new thing we learned LOL. This went on for like 5 years!

    Man I wish we could do some kind of reunion for all of us from 15 years back. Cody, Vinny, John, Neo and whoever else, first beer's on me!



    polkaudio sound quality competitor since 2005
    MECA SQ Rookie of the Year 06 ~ MECA State Champ 06,07,08,11 ~ MECA World Finals 2nd place 06,07,08,09
    08 Car Audio Nationals 1st ~ 07 N Georgia Nationals 1st ~ 06 Carl Casper Nationals 1st ~ USACi 05 Southeast AutumnFest 1st

    polkaudio SR6500 --- polkaudio MM1040 x2 -- Pioneer P99 -- Rockford Fosgate P1000X5D
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