W-baffle for IB 15

Posted In: Subwoofers 101


  • Participant
    shrub0 on #1286

    I’m planning on putting two AE IB 15s in a w-baffle. Similar to what is shown by Ollboll on the following forum:
    http://www.diyaudio.com/forums/multi-way/230017-what-ob-would-you-do-four-ae-ib15s-3.html

    My question is, since I planning on using this as part of a 2.1 computer system. What would be a budget way to power the AE’s plus 2 small satellite speakers?

    I’ve looked at 2.1 plate amplifiers on the parts express and madisound website but I don’t think the built in 12db/octave crossover would be sufficient to make the dipole peak inaudible.

    Any one have a thought on how much power this setup would take while keeping under 5% distortion from the subs?


    Participant
    taloyd on #11152

    Hello,

    I’d make the satellites sealed boxes that will naturally provide a high-pass filter by virtue of the air-spring. Then get any plate amplifier with high-level (amplified speaker level) inputs, and just run some additional wires from the amplifier going to the satellites to the subwoofers. Fiddle with the low-pass frequency dial on the subwoofer plate amplifier until it sounds nice. Something like Mark Audio drivers would be great with a low power (Tripath, etc.) amplifier.

    Any plate amplifier with less than 300 watts RMS probably won’t be able to drive the woofers anywhere near Xmax – so distortion would be low simply because it’s only utilizing a % of the capability of the subwoofers.

    Cheers,
    -Tal


    Participant
    stryke on #11151

    In an open baffle it actually takes very little power to move the woofers to their excursion limits. At 20hz it takes only 35W to reach Xmax. At 30Hz it takes 100W to reach the 12mm Xmax. I would look at between 100-250W per woofer for an open baffle application.

    MiniDSP has some good inexpensive options.

    http://www.minidsp.com/products/plate-amplifiers/pwr-ice125 125×2 or 450W bridged for $275

    http://www.minidsp.com/products/plate-amplifiers/pwr-ice125 250×2 or 630W bridged for $375

    This would give you dsp, crossover, and a good amount of power. If you built 2 modules eventually you could use the 250×2 amplifier with one channel to the sub module and the other channel to the satellite speaker.

    -John


    Participant
    shrub0 on #11153

    That sounds good but I thought the IB15 had a xmax of 18mm?

    How much power to drive two of these to xmax and what spl at 1m could I expect?


    Participant
    stryke on #11154

    Sorry I was modelling with the Dipole15 which is a far superior driver for this open baffle type application with the underhung motor and more linearity. Here are a few examples of speaker using the Dipole series drivers.

    http://www.lotusgroupusa.com/Granada.htm
    http://kyronaudio.com.au/#!gaia/gaia.html
    http://kyronaudio.com.au/#!kronos/kronos.html
    http://www.soulsonicspeakers.com/gallery.html

    That said, you could use the IB15HT in this application. It doesn’t have the underhung motor though. It is also significantly less efficient at only 86dB vs 90dB.

    The SPL at 1M depends on your baffle. As an example, an 18″ wide flat baffle will drop about 10dB from 100hz to 30hz. So if you start out with a driver that is 90dB 1W, at 30hz you are at only 80dB 1W. This also affects maximum levels. At 30hz on an infinite baffle, the IB15 can reach about 114dB with 600W input power. Factoring in the baffle loss you would reach around 104dB max. At 20hz it takes only about 175W to reach Xmax at 107dB. Factoring in the -14dB baffle loss that puts your max SPL at about 93dB at 20hz from the single driver.

    While these levels are slightly higher than with the Dipole15, The power requirements are magnitudes higher as well.

    The larger the baffle, the less baffle loss you end up getting and more efficiency and maximum SPL you can achieve. This is a model of an offset 18″ wide baffle that smooths the response.

    With a W-Baffle you will get less loss than this if the wings are large enough.


    Participant
    shrub0 on #11155

    I could see how the underhung motor is superior in the dipole but when you compare the Ib 15 and lo15 on drivervault the ib 15 has much lower distortion. What could explain this? What would you say is the lowest distortion ae driver in the lowest octaves?


    Participant
    stryke on #11156

    I am not seeing this situation at all. Take a look at the HD sweeps and see the F2 and F3 distortion from 100hz to about 600hz. The LO15 is significantly lower. The Tone 150hz-100dB you see a signifcant difference with the LO15 being .35% and the IB15 being 1.122%. When you get to the lowest frequencies under 100hz the distortion is much more a matter of the BL curve and displacement. If you want lower distortion you need larger drivers and more of them. Having 18mm Xmax, the IB15 will have an advantage over the LO15 down at those frequencies. The Dipole15 will be much closer to the IB15 in terms of distortion at those frequencies, while still having lower distortion above 100hz.

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