Bgavin - calculating excursion across freq

Discussion in 'Amps and Cabs [BG]' started by Magman, Feb 21, 2003.

  1. Bgavin -
    Is there any freeware software or algorythms for manual calculation you can recommend for determining driver excursion over frequency for a paticular inptu power?
    WinISD does not do this.

    This calculation seems to be of fundamental important when designing a sub-woofer system.

    I saw the plot of the magnum 18LF on your website and it apparently can have an 800watt 30hz signal put through it and remain within xmax (if I read the graph correctly). That seems quite incredible, and totally 'bowel shaking' if you run a synth through it.

    So, I'd like to compare excusion data between Magnum 15LF and Kappa Pro LF. If the avatar B15 box is tuned lower then it should be high performance right down to 30 hz (at least with the magnum, if its anything like the 18) - with group delay pushes out of the way.

    Its fun just testing configurations on winISD, and realizing how totally lacking deep fundamentals
    many bass cabs and home hi-fi generally are.
    Even with the trend for 5 string/detuned bass guitars, it the clanky sound of detuned/low string harmonics which appeals to listeners (myself included) rather than the actual presence of the fundamental - which should be there but isn;t conveyed well on low end hi-fi.

    All this work for 10hz down from 40.... whats that, 5 notes? :)

    Having said that, my bass guitar doesn;t put out too much 30hz when detuned by filtering out a lowB note on the computer with a low pass. Nonetheless, it is there, and a better bass would generate more I presume.
  2. ESP-LTD


    Sep 9, 2001
    There are lots of commercial cabs that don't do much at 40hz either.
  3. It is a peculiar state of affairs when church organs and acoustic double bass instruments, acoustic kick drums etc have probably 'better' more balanced fundamental tones than a typical low/mid end electric bass rig.

  4. Robert Bullock has an accurate DOS based program that will do the job.

    Link to DOSBOX

    This is a DOS program that will run fine with Win9x, but is a bit squirrely under Win2k and XP. It runs in a DOS box, but will lock the machine unless you follows specific steps. Do everything in a non-maximized window, *except* for plotting. Just before you enter the Power in watts for a plot, do an ALT-ENTER to expand the window to full screen. DOSBOX will not work unless it is a full screen app under W2k/XP.

    After you enter data in DOSBOX, be sure to exit frequently and then start it up again. This saves the data entry. DOSBOX will crash (lock) frequently, and all your data entry will be lost. It is not very friendly, especially for those who are not native DOS users (read: old farts like me). But... the program DOES work very well and will show you driver excursion at the specified input power.

    Brian Steele offers an excellent Excel spread sheet that will show excursion, plus thermal/displacement limitations.

    Link to Brian Steele Pages

    There is a LOT more work being done to get from 41 Hz to 31 Hz. If you are not going below 41 Hz, your options are much better. The trick is knowing how low you need to go, then going no further. The lower you go, the less efficient the driver, and/or the larger the cabinet.

    The Magnum 18LF is an acceptable compromise, and is the choice for my 1st cabinet offering. It is not a subwoofer, nor does it perform like one. On the other hand, it is pretty loud for a single driver and is of very high quality. I passed over the 15LF because of the too-high Qts which gives a mid-bass hump, then rapid rolloff. This might be a lot closer to some folks liking... I have not auditioned the 15LF, so can't say for sure.

    I dunno why Avatar has the Kappa Pro 15LF in such a large cabinet. The B115 cab is 6.45 cubic feet external volume, but this driver requires 2.9 to 3.7 cubic feet, depending upon alignment.