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Discussion in 'Amps and Cabs [BG]' started by Vince Klortho, Dec 18, 2013.

  1. ... or anywhere else for that matter. Sometimes I just don't understand what possesses people to do the things they do. That's the case with my good friend Doug. Doug knows more about sound and mixing than anyone I know or have met. He used to have a sound company but he sold all his stuff because he became frustrated that people were unwillingly to pay for quality and, basically, expected him to work for free. As musicians, I am sure we all feel his pain. Anyway, one of his earliest PAs was one he designed and built himself. He ended up parting it out and buying a bigger, name-brand one because promoters have an aversion to custom-built speakers. The subs he designed were awesome. He still has one of them - it's mate is in an installed system. This cabinet has two 18-inch JBLs woofers in it and it was designed to have an F3 of 30Hz which has been verified with RTA equipment. Each cabinet is about like a full-sized refigerator so they were not fun to haul around. It is truly spectacular to hear four of those cabinets thundering away and it is a rare thing to hear frequencies that low reproduced so loud and clean.

    Anyway, here is the weird part. I went over to visit Doug the other day and he did something I never, ever would have even considered doing. Apparently, he became bored for a while and with this guy that can be a dangerous thing. He told me that he had popped the jack panel off of his sole remaining subwoofer cabinet and rewired the speakers to be in series. Since they are each 8Ω that means the cabinet was a 16Ω load. What I hadn't noticed was he had taken an old AC cord and put a Speak-On connector on one end of it. He looked over and told me, "brace yourself and listen to this, ..."

    With that, he plugged the AC cord straight into the wall. That's right, a cabinet with two 18-inch JBLs was plugged straight into the wall and fed 60Hz at 120V. I have only ever been around something like that once (I won't bother you with that story) and it was an unbelievable thing. The sound from the cabinet was so damned loud I could feel it all over - it was overwhelming.

    If you do a bit of math with Ohm's law you will find that this meant 7.5A and 900W were being drawn by the cabinet which was no strain for those woofers. He told me he had verified this before he did anything to make sure it was safe. For the speakers, that is. For the building - not so much. As kids, we used to amuse ourselves with capacitor "bombs" and stuff like that but, damn, plugging a speaker into the wall? Who thinks of things like that?

    Remember folks, don't try this at home! Serious damage is entirely likely and bodily injury is possible.
  2. negativefx

    negativefx complete hack

    Feb 18, 2013
    Fort Collins
    So you're telling me I need to build an amp that puts out 900W@7.5A?
  3. M0ses


    Sep 11, 2009
    Los Angeles
    Holy balls I expected that to end so badly.
    That's super awesome though.
  4. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    I had thought about it, but with just over 240v from the wall, I'd have to risk both my Barefaced cabs at once. Risk mostly being my ears dying.
  5. wcriley


    Apr 5, 2010
    Western PA
    I gotta' try this!!!!!!!!
  6. Gaolee

    Gaolee It's all about the polyester

    Well, a little time and imagination is a dangerous thing. When I was in college, a friend was in a biology class that used rats with brain implants. After the class, the rats got "sacrificed." I wanted to rescue one and keep it as a pet, electrode and all. But, as a bonus, I figured you could run the wire the other way and plug the rat's brain into an amplifier and find out what kind of noises that would make.

    Unfortunately, the rat never maded it out of the lab, so I never found out what rat thoughts sound like.
  7. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
  8. Interceptor

    Interceptor Supporting Member

    Mar 29, 2005
    Madison, WI
    If I remember the story right, Gene Czerwinski (founder of Cerwin Vega) used to do that same stunt to demonstrate the stoutness of his woofers when he'd go out on sales calls.
  9. BassCliff


    May 17, 2012
    So. Cal.

    Something like this? ;)


    Thank you for your indulgence,

  10. Be sure to tell me when, Bill.

    I'll let you know how loud it is up here.

  11. skychief


    Apr 27, 2011
    South Bay
    let us know how how it goes. And keep a fire extinguisher handy, ;)
  12. I foresee new entries to the 'Darwin awards'.

  13. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    I recall some videos on youtube of people doing this. Look for wall voltage speaker or 120V speaker. Lots of smoke.
  14. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    the youtubes are all folks destroying speakers for laughs;

    if wiring to 16Ω really does limit wall juice to 900w and the cab "supports" 60Hz, then that's a different thing, and probably a real experience to hear.
  15. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    Okay yeah, that is even cooler than capacitor bombs.

    If I recall correctly, that 900 watts sine-wave is comparable to 1800 watts RMS, from a thermal standpoint.

    More don'ts: Don't put the cab in a corner, and don't re-tune it to 60 Hz. You don't need another 6 to maybe 12 dB output at 60 Hz.

    Earplugs are probably not much more than decoration at that frequency and SPL, as the sound is going right through your bones to your inner ear regardless of what you stuff in your ear canal. One last don't:

    Don't forget your Depends.
  16. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    i was just thinking about that after i posted!

    it's not a 900w "RMS" average of pounding rock music, it's a continuous 900w sine wave!

    that's a whole different deal, and probably risky to even super-powerful sub drivers.
  17. That's exactly right! My inner ear was getting shook so hard that I felt dizzy and nauseous for several minutes afterward. [​IMG]
  18. 4-stringB


    Jun 10, 2010
    OP; Is this the ever elusive Brown Note? :cool:
  19. Foz


    Jul 26, 2008
    Jax FL USA
    Aren't you guys looking at that backwards?

    Doesn't the drama come from the fact it is RMS volts and that means the swing is much higher than 120v and because a wall socket has both sufficient inrush and continuous output capacity at 7.5 amps of current that an extension cord amp yields super stiff power rails able to support both instantaneous and continuous power flow for the full voltage swing?

    Doesn't the wall voltage being 120v AC RMS* mean the peak is about 170v and full peak to peak swing is about 340v with no lag, no sag and a 100% duty cycle. :hyper:


    Want to get crazy mic the kik drum and use that signal as a switch signal [sidechain input] on a normally closed switch [gate] to your 120v amp = click / BOOM!

    *root of the mean square = 120v AC made equivalent to 120v DC = to match the power throughput of a DC source averaged over time the AC sinewave has to have higher peak volts [+/- 141%] = double that in peak to peak swing.


  20. Dave Curran

    Dave Curran Lilduke

    Jul 27, 2013
    Didn't Tesla almost bring a building down this way. lol