"Usul" the IB sub


  • Participant
    stryke on #287

    mtbdudex on the Cult of the Infinitely Baffled forum had put together a good line array subwoofer using 4 of the IB15’s in his home theater. His thread on the Cult forum is extremely detailed showing all the planning and build stages extremely well. Many in depth pictures of the process.

    This is what it looks like in the room from one of the pictures he has up:

    Follow the following link to the Cult forum to read the full thread and see pictures of the build process:

    http://ibsubwoofers.proboards51.com/index.cgi?board=projects&action=display&thread=957

    John


    Member
    mtbdudex on #3491

    Hey guys, I did not mean to double post, I posted in this forum after John posted my build, sorry for that I totally missed this thread, I just consolidated my remarks into this post and will delete my other post.

    I have a build thread at The IB Cult forum, however I want to post here my finished product.
    (well, I have to make the rectangular speaker cover still)

    I’ve named this IB subwoofer “Usul”, because I had to cut thru rock (concrete foundation wall) to make this project a reality:

    Carpeting and wall acoustic treatments are a few weeks away.
    Yet I am so please with the sound quality, clean, powerful bass presense.

    Anyone considering to build a IB sub I highly recommend the AE IB15’s, great value for the $$’s.
    My total investment is around $1.3k, speakers, amp, EQ, mounting boards, hardware, speaker grille cloth, etc.
    I am driving them with the Behringer EP2500 Europower Power Amp, EQ Behringer FBQ2496 Feedback Destroyer (not dialed in yet)


    Member
    mtbdudex on #3492

    Here are some YouTube videos I made of the 4 x 15″ AE IB15’s in action.
    (still a few week before carpeting/other, excuse the messy look)

    Kinda dorky play-by-play ;), I was watching/listening to the DD 5.1 demo DVD I got from CES 2006 and the LFE’s in there are quite neat, good selection of clips and it was “free”.

    Close view showing some cone movement action:
    http://www.youtube.com/watch?v=xFpJL3oH1Z8

    This wider view is from the back of my HT
    http://www.youtube.com/watch?v=RtO9P8SP_JY

    Here is from the utility room/backchamber
    http://www.youtube.com/watch?v=oE-V7s_Rex0


    Member
    mtbdudex on #3495

    John/Others;

    I finally got REW up and running just so I could baseline my IB sub.
    I decided to take some detailed baseline measurements of my IB line array, just to get more practice with REW and learn more about speakers/subwoofers.

    Baseline specs:
    IB sub line array (4) AE IB15’s, EP2500, no EQ, spl 75db calibrated @ 36″ from cone.

    Can you give me some general comments/critique/etc.?
    Is this how you’d expect your drivers to plot/graph in a line array like mine?

    Can I summarize:
    Close to “flat” within +- 3db 15hz – 80hz @ 1″?
    Room modes are showing themself around 29hz/41hz/47hz etc and will have to be dealt with via further bass traps and/or EQ pushing the peaks down but leaving the lows alone. (I’ll learn as I try filters)

    Thx for time/advice/education opportunity.

    Line array measured 1″ from dust cap for each driver centered:

    Line array measured 12″ from dust cap for each driver centered:

    Overlay of 1″ and 12″:

    Overlay of 1″ and 12″ with “expanded” to see differences:


    Member
    mtbdudex on #3493

    My bad being new to REW, here are the graphs with 1/3 octave smoothing on.
    1″ and 12″ nearfield measurements:

    Here is at my 2nd row seats for ref, no EQ at all (yet), seat is 16″6″ from front wall (IB sub location):


    Member
    simon5 on #3494

    The frequency response at the place you will be sitting is the most important to me, and it looks quite fine !

    You can achieve quite a good frequency response at your sitting place… great !

    Is that reference curve smoothed ?


    Member
    mtbdudex on #3496

    @simon5 wrote:

    The frequency response at the place you will be sitting is the most important to me, and it looks quite fine !

    You can achieve quite a good frequency response at your sitting place… great !

    Is that reference curve smoothed ?

    Yes, I applied 1/3 octave smoothing to all the charts.
    I calibrated the above charts just at 36″ from the line array, so you see some drop-off in db’s at the 2nd row itself.

    Below I calibrated REW at 75db at the “sweet seat spot”, shows waterfall chart taken at 2nd row seat 3, I’m running -9.5bd filter @ 30hz and 2nd filter-3.5db @ 50hz.

    Here is that frequency plot:

    Here is waterfall plot, you can see the purple (w/o filters) has come down nicely on the green:

    As I stated in my Cult thread:
    Fired up KFP again, went to the end big fight scene.
    Me and my 3 kids were seated at 2nd row seat position 3, RS meter in my hand, on max hold, slow, c weighted.

    I was getting 117db at some parts, then I got 122 db when Panda flinged Tiger up into the sky and he hit the ground, but, the kicker was the wushi finger hold “Skadoosh” pressure was peaked at 124db !!! :-* :'(

    OMG that was so totally awesome.

    Ok, so I “cheated” and while tuning/audyessey set-up/etc I had the EP2500 gain at 12 o’clock, and for final db max test I turned it to 3 o’clock, 5 o’clock if full gain so I was just under that. Back to 12 o’clock for now, no need to tax my EP2500.

    I know there are many Blu-rays with great LFE, but the “wushi finger hold” LFE at the very end of KFP seems the best test, and my kids love watching it:

    “You are blufing Panda, Master Shifu did not teach you the wushi finger hold?”

    “I am the Kung Fu Panda, and figured it out all by myself!”

    My point to anyone reading this considering AE IB15’s for your DIY subwoofer project, the do deliver the goods as promised!


    Member
    mtbdudex on #3501

    Just for fun I opened up REW and re-plotted the 3rd seat chart, this time extending it to as low as REW goes, 2hz.


    Member
    simon5 on #3502

    Very nice hehe ! I have doubts that you could achieve high SPL at 2 Hz on the other hand… 😀

    What mic are you using ? It seems quite flat down to very low digits… 8)


    Member
    mtbdudex on #3503

    @simon5 wrote:

    Very nice hehe ! I have doubts that you could achieve high SPL at 2 Hz on the other hand… 😀

    What mic are you using ? It seems quite flat down to very low digits… 8)

    I’ve got the Behringer ECM8000 mic with a mic cal file loaded for it, and instead of using my Dell D620 laptop internal sound card (which calibrated terrible) I’m using a M-Audio MobilePre USB Portable Audio Interface which calibrated nicely. I use this “free” Behringer ECM-8000 cal file via HTS forum http://www.hometheatershack.com/forums/downloads-area/19-downloads-page.html

    I thought to myself, am I really-really hearing/feeling sound at such low freq??

    Alright, took some picts and made some YouTube videos to prove to people this IB sub does work as low as it can go and does not tear apart.

    These AE IB15’s are awesome speakers!!!!
    Thx guys for superb product.

    Test DVD, note the tones are encoded at -20db to “protect the innocent” from destroying their system.

    YouTube Videos:
    “Usul” the IB Subwoofer Feb-12-2009 at 10hz tone.
    This video show my 4 speaker line array Infinitely Baffled Subwoofer speakers up close, you can see 10hz subwoofer cone movement action .
    I’m getting 80db, and this signal was attenuated -20db on the recording, so plenty of low freq headroom. Capable of 100db!!
    http://www.youtube.com/watch?v=jhNbKhvD7zs

    “Usul” the IB Subwoofer Feb-12-2009 at 6hz tone.
    This video show my 4 speaker line array Infinitely Baffled Subwoofer speakers up close, you can see 6hz subwoofer cone movement action .
    I’m getting 77db, and this signal was attenuated -20db on the recording, still some ultra low freq headroom.
    http://www.youtube.com/watch?v=1tnWkcMM61k

    “Usul” the IB Subwoofer Feb-12-2009 at 3hz tone.
    This video show my 4 speaker line array Infinitely Baffled Subwoofer speakers up close, you can see 3hz subwoofer cone movement action.
    Yes, that’s not a typo, 3hz.
    http://www.youtube.com/watch?v=pNnWojdBwTc

    “Usul” the IB Subwoofer Feb-12-2009 at 10hz tone HT screen/other
    This video show my 4 speaker line array Infinitely Baffled Subwoofer vibrating my 130″ DIY Ht screen – hard to see via handheld camera in video mode but it did vibrate, so definitely the 10hz pressure wave is there, real.
    There are all sorts of resonances/other in my basement @ 10hz, for instance my walkout french doors pulse in/out @ 10hz.
    http://www.youtube.com/watch?v=O2nuF8qI9Ms


    Member
    mtbdudex on #3504

    Simon5/John/AE staff;
    BTW, 2 Q’s:

    1) If you had to specify the “low freq roll off point” for my IB sub what is it?
    If I said 5hz is that correct?
    2) How “flat” is my IB sub to?
    Again, is 5hz correct?

    Thx guys.


    Member
    simon5 on #3497

    Well your IB sub doesn’t seem to have a real rolloff cutoff point… With high loudness it wouldn’t be flat at 2 Hz because you would see overexcursion, but with moderate volume its rolloff is 2 Hz…

    For the flatness, it depends where you measure. From your latest set of measurements, it’s kinda flat +/- 3 dB from 2 Hz to 35 Hz hehe !
    I think if you add a little bit of EQ, you will manage to flatten this even more…

    What are the three curves ? I would not try to EQ the bumps and dips below 5 Hz it’s worthless, but maybe try fixing between 30 Hz up to your desired high frequency cutoff point. Don’t put too much EQ, since some frequency problems might be caused by room modes.


    Member
    mtbdudex on #3498

    @simon5 wrote:

    Well your IB sub doesn’t seem to have a real rolloff cutoff point… With high loudness it wouldn’t be flat at 2 Hz because you would see overexcursion, but with moderate volume its rolloff is 2 Hz…

    For the flatness, it depends where you measure. From your latest set of measurements, it’s kinda flat +/- 3 dB from 2 Hz to 35 Hz hehe !
    I think if you add a little bit of EQ, you will manage to flatten this even more…

    What are the three curves ? I would not try to EQ the bumps and dips below 5 Hz it’s worthless, but maybe try fixing between 30 Hz up to your desired high frequency cutoff point. Don’t put too much EQ, since some frequency problems might be caused by room modes.

    These are 2nd row 3rd seat (sweat spot).
    I do have measurements of all 7 seat positions stored.

    I finally ended up with 2 filters, one applied at a time.
    Purple is 0 filters.
    Dark green with just 1 filter @ 30hz, -9.5db, I ignored REW 2nd filter suggestion at this time (56hz).
    When I measure again the peak shifted slightly lower, so I applied 2nd filter at 50hz, -3.5db.
    Light green if final curve. This way people can see the progression. Of course mic was on stand not moved at all.

    I’m using 80hz as cutoff, therefore I might look into slight negative filter at that “hump”, might also tweak the 30hz filter somewhat, but for the 2nd row as an aggregate that would push me down below “flat” for other seat positions, I’d have to re-open that measurement file.

    I’m not a bragger, but is this worthwhile bragging rights??
    Flat down to 5hz?

    Since this is your biz, I swear when I did the 6hz test tone I could hear that, definitely my ears could feel the pressure pulsations.
    Like when you drive in a car with sunroof open and the windows only cracked slightly, feel the low freq pulsations.
    So, at 6hz do I also get some 2nd/3rd/4th order harmonics (12hz, 18hz, 24hz) and if so I might have been hearing those?
    My ears could feel the pulse in sync with the EP2500 amp LED lights.
    Kinda geeky/nerdy cool.


    Member
    simon5 on #3499

    Light green ? That looks like baby blue to me ! 😀 Baby blue curve is great, I would just filter a bit to counter the rolloff between 50 Hz and 80 Hz. The rest is perfectly fine.

    Yeah 5 Hz would be fair to brag about, since you have a sharp dip after that.

    You can hear 6 Hz no problems, it just need to be extra loud, and yes there’s lots of harmonics. Probably the 2nd harmonics and 3rd harmonics are higher than the fundamental. I guess you could check that by yourself with REW.

    Those low frequencies are more felt than heard, but you can hear them if they are loud enough. It’s really fun, it adds some tactile feel to every movie. It’s a very good thing to me.

    Keep up the good work !


    Member
    mtbdudex on #3500

    @simon5 wrote:

    Light green ? That looks like baby blue to me ! 😀 Baby blue curve is great, I would just filter a bit to counter the rolloff between 50 Hz and 80 Hz. The rest is perfectly fine.

    Yeah 5 Hz would be fair to brag about, since you have a sharp dip after that.

    You can hear 6 Hz no problems, it just need to be extra loud, and yes there’s lots of harmonics. Probably the 2nd harmonics and 3rd harmonics are higher than the fundamental. I guess you could check that by yourself with REW.

    Those low frequencies are more felt than heard, but you can hear them if they are loud enough. It’s really fun, it adds some tactile feel to every movie. It’s a very good thing to me.

    Keep up the good work !

    You are right, I got my colors mixed up! The baby blue curve is the 2 filtered curve.

    Agreed, my 3rd filter will “attack” that 50-80hz zone, homework for the weekend.

    Sweet, I’m adding “flat to 5hz” to my “Usul the IB sub” sig line in all my various forums.
    You guys gotta be getting good/deserved PR also from that.

    Like I’ve said, no buttkickers needed in my HT, hear and feel the real deal.

    After I dial in the 3rd filter I’ll post that sharing.

    Looks like anything below 5hz is filtered on my EP2500 anyways, so that is as low as this IB will go….not that I’m complaining.
    (Of course I have the low pass filters set to off, because I want those Low freq to pass thru)

    thx.

    Edit 2-20-09
    I changed my sig to “flat to 10hz” after reading about claims of the in-accuracy of the 8000 measurement mic below 10hz, no need for controversy, 10hz is still respectable and worthy for a little bragging.

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