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Author Topic: My first Sub Design.  (Read 10919 times)

Antone Atmarama Bajor

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Re: My first Sub Design.
« Reply #20 on: December 05, 2005, 05:16:06 am »

     Ok Mark,
My intention for building this cab is personal application as a bass rig.

    My original criteria was to have as much output in the 30Hz and bellow range as possible in a conventional direct radiating cabinet roughly around 10cu'.

    I play a 5 string bass.  Fundamental of Low B is 30Hz I drop tune 1 whole step to Low a 27.5Hz.  Almost no commercially available Bass Guitar cab has much significant output bellow 40Hz let alone bellow 50Hz even worse once power bandwidth is taken into consideration.

    After much cabinet and driver modeling I came up with a 12cu' cab that utilizes 4 12" Lab 12 Drivers (TS params specified by Tom Danley for the LAB subwoofer project so I feel it is somewhat appropriate that I post about it here).

    What I came up with was a pair of 6cu' cabs using two 12" drivers each (think of them as one cab its just easier to move that way).  I am able ot achieve 124dB at 30Hz 1 meter with very low harmonic distortion.  More than enough headroom to play at reasonable stage volumes at those levels.  I also have the added bonus of significant usable low distortion extension down to and below 20Hz.

    I don't think that they are the best option for Large PA sub.  I think We would all do a lot better with one or more of Tom Danleys Towers if extension down to 20Hz is desired.  Although if that level of undistorted extension to 20Hz was required my BS-212 would do better than 90% of anything considered a PA sub.  But It would take a lot of them and a lot of amplifiers to get proportional SPL.

    I do think that they would lend themselves well to studio, and home theater applications.  I think I actually exceed the Genelec 4X12 sub as far as distortion, extension and SPL.

    I have never experienced anything else like them.  Playing my 5 string bass guitar in front of the thing makes me feel like I've lost my land legs.  Playing a 20Hz sinewave through them makes me feel ill, and modulates my voice.

    I am not trying to sell the thing to anybody, and I plan on making the cad drawings available to anyone that is interested I just haven't cleaned them up and labeled them enough to be very useful to anyone.

Sweeps:

http://srforums.prosoundweb.com/index.php/m/82403/8490/?SQ=a b1ac9f6e1e07f049ef86293c162ec0c

    This as I said is a project of personal interest and my first speaker cabinet.  There is nothing extraordinary about it.  It was born out of my discontent with BS subwoofer/speaker specs and wanting to have something with superior performance and much less cost.

    Rory,
      Can they be used in pro audio.  Sure why not, are they practical, that really depends on the situation now doesn't it.  I think this design is borderline in where it is applicable and doesn't need to be pigeonholed.

Antone-
   
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Antone Atmarama Bajor

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Re: My first Sub Design.
« Reply #21 on: December 05, 2005, 05:29:10 am »

     Another thought,
    Isn't it normally better to have bigger rigs in smaller venues.  An smaller rigs in large venues since keeping stage levels down to keep the FOH clean is important.

 Where in a smaller club/bar like venue the PA is normally used for vocals only.

Antone-
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MARK PAVLETICH

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Re: My first Sub Design.
« Reply #22 on: December 05, 2005, 06:27:59 am »

Have you ever done a scope reading of the actual output of the low B string on your bass guitar? If so, can you answer the following questions
How much fundamantal was present on the lowest note produced by the low B string ?
IMHO the only instrument that I have encountered that produce significant fundamentals at those very low frequencies are based on electronic oscillators. How much 30 hertz fundamantal do you think a 34 inch scale 125 thou thick bass guitar string is producing ? You might be hearing something but I very much doubt it is much 30 hz fundamental.
Far be it from me to question the artistic validity of making people sick with very low frequency sound, but the science of doing it needs to be addressed.
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Antone Atmarama Bajor

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Re: My first Sub Design.
« Reply #23 on: December 05, 2005, 03:30:14 pm »

     No I've done better I've done a spectral analysis.

    I know all about electromagnetic pickup placement and roll off issues.

http://www.till.com/articles/PickupResponseDemo/index.html

    The roll off has a bit to do with practicality of placement and also not hitting a null for any of the fretted note fundamentals.

    Right now All I have is a clunky Graphic EQ to compensate for roll off.  But I am probably going to use a simple high passed integrator summed with a highpass filter to give me a 6dB per ocatave boost to counteract the 6dB per octave roll off.

    The Zero dB point is determined by Instrument scale (mine is 35") and pickup distance from bridge and tunning of the string.  So the integrator has to be optimized for the particular instrument.  I also have the option to run my pickups in stereo so I can have one EQ per pickup since both have different 0dB points.

    There sure are a lot of people that are agitated about the prospect of me even trying to attempt to reproduce the fundamental of my bass.

    I agree that normally only synthesisers and oscillators can easily reproduce significant LF sinewaves.  So what.  Have you ever banged on an orchestral Bass Drum?  It doesn't generate a pure sinewave but it has a very low fundamental pitch.  Does any non electronic instrument produce a pure sinewave.  Ever play with a quartz urn (the ones used to grow silicon ingots in) those things can shake the walls of a house.

    Ok Mark what is your personal experience with Sub Bass.  I consider myself a novice.  I feel lucky enough to know what a 20Hz sinewave at 116-118dB is like.  I also own 8 BT7's so I know what a sinewave at 30Hz in excess of 136dB is like.  Its not a very big club have you ever been experienced.

    I would venture to say that nay sayers have not.  Or they have weak stomachs.

Antone-      

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MARK PAVLETICH

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Re: My first Sub Design.
« Reply #24 on: December 06, 2005, 04:23:29 pm »

Where did I say sine wave in my post ? The lowest PITCHED low frequency sound that I have ever experienced from a non electronic instrument was from a very large pipe organ. If you want real low frequency non electronic sonic information, I would suggest 155mm artillery, I have only felt the outgoing side of it. I imagine it is even more impressive at the incoming end !!!!
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Antone Atmarama Bajor

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Re: My first Sub Design.
« Reply #25 on: December 06, 2005, 05:33:31 pm »

Dont make me play a solo on my Electric Shirt Colar!
Laughing

I'm afraid of the report from a 155mm cannon.

Antone-
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