IB15 AU vs. IB15 HT

Posted In: Subwoofers 101

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    picassotheimpaler on #1100

    I havent been able to find any information about the two for a comparison. The AU is designed specifically for car audio use and what im probably going to use in my setup, and the HT for home theater applications. But I havent been able to find anything about what the spec differences between the two are, and i was wondering about what effects running the HT is a car would have or vice versa. Has anyone on here heard any more than i have?

    stryke on #10589

    The woofers have very different parameters as the applications are far different. The IB15-HT is used in a very large infinite baffle. It is designed to have an F3 point around 16Hz in this application where there is no cabin gain factored in. They have a higher Q and require a very large area for the infinite baffle chamber. They make very efficient use of Xmax in an application with adequate room in that rear chamber.

    The IB15-AU are designed to go in a vehicle and work with cabin gain. They are lower Q, have lower mass, are much more efficient, and as a result require much smaller volumes.

    The SBP15 is the upgrade to the IB15-AU. It has a larger motor and thicker top plate. This thicker top plate gives a more broad BL curve for more force and much lower distortion.

    Both the IB15-4AU and SBP15-4 have been used in SQ champion vehicles.

    IB15AU-4 :
    Fs: 20.4Hz
    Qms: 4.5
    Vas: 387L
    Cms: .4mm/N
    Mms: 152g
    Rms: 4.35
    Xmax: 18.5mm
    Sd: 825sqcm
    Vd: 3.05L
    Qes: .45
    Re: 2.7ohm
    Z: 4ohm
    BL: 10.8Tm
    Le: .163mH
    Pe: 300W
    Qts: .41
    1W SPL: 90.6dB

    Fs: 21.3Hz
    Qms: 5.35
    Vas: 338L
    Cms: .35mm/N
    Mms: 152g
    Xmax: 18mm
    Sd: 825sqcm
    Qes: .45
    Re: 2.7ohm
    Le: .3mH
    Z: 4ohm
    Bl: 11.1Tm
    Qts: .41
    1W SPL: 90.65dB

    Fs: 16Hz
    Qms: 6.8
    Vas: 439L
    Cms: .45mm/N
    Mms: 220g
    Rms: 3.239
    Xmax: 18.5mm
    Xmech: 25mm
    Sd: 830sqcm
    Vd: 3.07L (p-p)
    Qes: .78
    Re: 5.5ohm
    Le: .33mH
    Pe: 500W
    Qts: .7
    1WSPL: 86dB
    2.83V: 87.3dB

    picassotheimpaler on #10590

    Thanks! That’s exactly what i was looking for. Since the SBP is an upgrade to the IB, would it have better output at higher frequencies and maintain a flatter response overall? This is going to be my first IB set up, and Ive heard that IB tends to fall off above around 70hz. I don’t have room for anything larger than a single 6.5″ in my doors, so i was hoping to be able to run the subs as high as possible without sacrificing clarity or the extreme low frequencies. Also, since the SBP is an upgrade, how much does it upgrade the price from one to the other? And on a different but related note, would the Apollo motor upgrade allow them to play higher frequencies as well as increasing the SQ? Thanks for info man!

    simon5 on #10591

    Apollo upgrade doesn’t improve the frequency response, it’s there to increase powerhandling, reduce power compression and yes improve SQ but only at high SPLs.

    Yes the SBP15 has better high end than IB15.

    Typical IBs can fall off above 70 Hz, but the IB15 has a quite better high frequency response than that.

    stryke on #10592

    A car IB install has 2 issues that affect the upper end. First, the high end does not have much cabin gain. Here you can see a somewhat typical car transfer function measured in my 2001 S4.

    You can see that at 30hz there is about 20dB more gain than there is in the 60-100hz range. It is important to pick a woofer that starts to roll off around the same time as the increase in cabin gain. The IB15AU and SBP15 are designed to do that. Also you want to have a woofer that has high efficiency so it is louder in the upper range without requiring a ton of power. Both drivers are over 90.6dB 1W. This is extremely efficient in the car realm as most drivers reach the 85-88dB range at best. This efficiency gives more of the high end output.

    Secondly are the issues with driver rolloff due to inductance. Many car drivers have massive coils and start to roll off by 70hz. I have measured some with an inductive peak around 45hz that begin to roll off by 55Hz even. That further decreases the output that is already lacking due to the cabin gain. This is not an issue with either the IB15AU or SBP15. Both woofers extend cleanly to well over 500hz. You can see the IB15 response here:


    Further decrease in output comes due to the path length difference between the woofers in the trunk and mids in the doors. They are often out of phase at the crossover point causing a large null in this range. If you are crossing around 80hz, that area can be nearly gone. If you are really going for a good SQ setup, it is worth investing the money in something like the MiniDSP units for around $120. That way you can time align all drivers properly and then EQ the response flat as well.


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