Done! Cerwin-Vega HED-12 twin subwoofer design (pics)!

Discussion in 'Home Theater Projects' started by Javier_Huerta, Mar 3, 2004.

  1. Javier_Huerta

    Javier_Huerta Supporting Actor

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    I bought these drivers on November, 2002... did I just set a record for the longest time in building a subwoofer? :b

    - What I tried to do:
    * Build a decent enough subwoofer with parts available in México City. That means no Adire, no Parts Express, no... well, you get the idea.

    - The specs:
    * Driver: Cerwin-Vega! HED-12 DVC subwoofer drivers.
    * Wired in series, for an 8 ohm load.
    * http://www.cerwin-vega.com/products/...dio/index.html

    - The boxes:
    * Two 40 x 55 x 80 cms. boxes, heavily braced with 2 crossmembers, 1" MDF, countersunk screwed and glued, 118L total net volume (braces and PVC pipes included).
    * Tuned to (approximately) 19 Hz using 4" PVC pipes.
    * Twin audio inputs per box (one per voice coil).
    * Used 1/2 lb of polyfill per 1 cu. ft.
    * Semi-gloss black finish, silver legs.
    * Weight: around 100-110 lbs.

    - The amp:
    * Harman / Kardon integrated amplifier (100W RMS per channel into 8 ohms).
    * PE 300-794 amp running at 272W RMS into 4 ohms (the two drivers are running in parallel).

    - The simulation:
    * According to WinISD:
    * Transfer function magnitude: -6dB @ 20 Hz, slope starting at 60 Hz.
    * Group delay: 20mseconds @ 20 Hz
    * Cone excursion: 22mm. max at 100W per driver, 30 Hz.

    - The pics:
    * Box with stuffing, driver not installed, caulk in place. 15 cms. tall feet.
    [​IMG]
    * Box ready to accept driver installation:
    [​IMG]
    * Driver in place, all ready to go!:
    [​IMG]

    * Twin boxes in place, minimonitors, electronic equipment and TV:
    [​IMG]

    - The sound:
    I substituted a sealed C-V sub (which I made using the same drivers these subs have) for the twin vented subs (Hertz-1's? I like the name!). I absolutely loved the sealed sub - it had a very nice sonic signature to it. But it rattled at high volume (mainly because I used an old particleboard box for it).

    I intended these subs to go into a much larger room, but things changed... still, I thought it'd be an interesting thing to build.

    Well, I should have known better. For this particular application the sealed sub is a better option.... yep. It is.

    Why?

    Because the whole room rattles with the sound of these things!.

    Bear in mind the room is made of mortar, bricks and concrete... but the subs have so much lower energy they make every window, door and closet rattle. The TV itself rattles! (not a good thing, I assume). Whenever I try to "test" the subs, the whole room is overwhelmed by vibration.

    The subs themselves at lower volume sound incredible. They have a very dry signature to them. There's zero overhang (when compared to a Velodyne sub I own). I guess they need to be broken in - I could hear some rattles inside the box as every screw began to seat in in their positions. But the sonic character is quite nice - it goes down *deep* and the driver themselves never seemed to bottom out during testing. The sound is close to my Tempest sub - very close, in fact! In this particular room, I guess there's so much bass reinforcement these babies sound even lower and deeper than my AA Tempest (which is in a much larger room). The twin design helps a lot in never even making the drivers breathe hard - although when I tested the setup with just one subwoofer, I noticed there weren't so many rattles in my room. I guess the 30-20Hz added energy is really making everything move.

    Another thing. They don't mate well with the little ProMonitor 80 speakers. They have way too much bass and gain! I'm losing a lot of output by running the subs calibrated to the mains. My original plans called for much bigger DefTech BP-8 bipolar towers, but I had to scale back on everything.

    Bottom line - Manuel, buy the HED-12's. They are a *steal* at $60 USD! My whole project (twin boxes) cost around $470 (amp not included), and I can't think of *any* commercial sub for less than $1,500 USD that can even come close... as a matter of fact, I think DIY subs can't be touched by commercial offerings by now. [​IMG]

    [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] / [​IMG] [​IMG] [​IMG] [​IMG] [​IMG]


    Edit: added new pics.
     
  2. Manuel Delaflor

    Manuel Delaflor Supporting Actor

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    Well done. If you say they are not REALLY apart from a Tempest, then they should sound good enough. I wonder if this will allow more people to use (in certain circumstances), car drivers to fill up with bass their home theaters. [​IMG]
     
  3. Javier_Huerta

    Javier_Huerta Supporting Actor

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    Well, our circumstances are limited enough for us to use said drivers [​IMG] The Tempest surely can produce a bit more db's out of a single driver. And the group delay I got from my sub (20 ms) is quite a bit higher than my AA Tempest... and I bet the Tempest's parameters are a lot better measured than the C-Vs.

    But, to be honest, I shudder to think what kind of subwoofer I could have bought for that kind of money around here. Perhaps a 10" (or 8") sub with a "100W RMS" driver and heavy EQ (plus underdamped response). These things blow away *any* subwoofer I've heard in stores around here. Perhaps, even the $2K B&W Series 6 aluminum sub.

    For the money (and our situation), I find the C-V's more than decent enough for any application...


    BTW, if you plan on building a sub with them, be ready to modify them a bit. You'll need to enlarge the screw holes in the plastic bezel, and use a drill to enlarge the chassis holes in order to use the PE subwoofer mounting kit (an absolute necessity, if you ask me).
     
  4. Rory Buszka

    Rory Buszka Supporting Actor

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    Think about the overpowering levels like this: Calibrate the system with the subs matching the mains, and then when the movies call on them to really bring down the house, they will be able to. I heard the ProMonitor 80s at an Ovation store, and they didn't sound bad, and they seemed to have quite a bit of headroom (they didn't lose control of their BMs at higher volumes).
     
  5. Javier_Huerta

    Javier_Huerta Supporting Actor

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    Rory, thanks for your thoughts. I calibrated the sub 6 dB higher than the mains, and the crossover is running at 100 Hz. I'll definitely change its parameters tomorrow...

    The more I listen to them, the more I like them. There's no overhang, no undue port noise, no nothing... just lovely bass. [​IMG]
     
  6. Javier_Huerta

    Javier_Huerta Supporting Actor

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    So, now I have tested my subs thoroughly. I moved them so that they are now on each corner of my room. Doing so greatly lowered the noise I was getting (mostly because there's a door on one corner). I also calibrated them, and they are now just 2 - 3 dB louder than my main speakers.

    I now know why Adires and such are considered so superior to other brands.

    These subs came out pretty much as I expected. Frequency response to 20 Hz is down about 8 dB's, and that's pretty much the tuning frequency. The box has settled and it has zero rattles. There aren't any leaks.

    But...

    When playing sine waves, there's a strange "flapping" noise when driven by a pure 20 Hz signal @ 100% power some -8dB below reference. It simply... flaps.

    I can drive the sub louder, but the flapping increases in SPLs. I *guess* this is an harmonic, and that... well, you do get what you pay for. [​IMG]

    I wonder if this is audible at "sane" listening levels, though. I normally can only bear listening at around -15dB below reference, and at that point, the subs could take the beating without any kind of problems whatsoever.

    For their "listening" test, I used Blue Man Group's Audio DVD-A. I picked track 3 ("TV Song").

    Well... well... well...

    I can only say I could feel the couch vibrating as it had never done before. I could feel my chest thumping to the beat when the "big drum" came in. It was astoundingly solid and powerful. I could only get to -8dB below reference without chickening out.

    So the subs "flap" at 20 Hz (and so on)... but, to be honest, I'll never get even close to that kind of power. I can only wonder what you guys with Tumults are getting, SPL-wise!

    So... I'm a happy camper now. [​IMG]
     
  7. Wayne Ernst

    Wayne Ernst Cinematographer

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    Javier,

    You did a wonderful job of creating two very nice subwoofers - given the lack of supplies that you faced. You also made some great points on how the gear sold at the retail level can't even compare when it comes to price.

    The thing to keep in mind about retail items is that so many people need to get a "cut" of the price. The distributor, the retailer, etc. - all need to collect their percentage.

    I bet you now wish that you didn't wait so long to build this fine subs. Thanks again for sharing your contribution with the group. [​IMG]
     
  8. Daniel_AVR

    Daniel_AVR Extra

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    Javier,

    did you have the T&S parameters for this HED driver?

    I have a friend who have one, and would like to model it in WinISD but can't find parameters on Cerwin Vega web site

    thanks

    Daniel
     
  9. VinhT

    VinhT Second Unit

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    The flapping is probably port noise. Or, you driver is simply unloading below the tuning frequency.
     

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