Dayton DVC 12" Help

Discussion in 'Home Theater Projects' started by MarkRoberts, Jan 20, 2005.

  1. MarkRoberts

    MarkRoberts Stunt Coordinator

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    I have a Dayton DVC 12" sub in a 85L enclosure and I am not satisfied with it. It seems to struggle with the sub 25hz stuff,it also bottoms out.The amp is a Rythmik A250 basic. I have thought of doing several different things.
    I thought about a PR design but I don't think this will do it plus the cost is enough to call it a risk. Since I might not like the sound of a PR'd sub.
    While looking into the PR it was suggested by Jack Gilvey to try the 142L adire shiva design. I happen to have a 4" Precision Port already. So I think I will go the sonotube route since the construction should be fairly speedy and cheap.There is one thing that has me concerned and that is after reading thread after thread of similar issues. I have seen it posted more than once that as the enclosure goes up in volume it will be easier(take less power) to bottom out the driver.
    So I was checking out adire's site and came across the DVC Subwoofers 101. Where it talks about using one coil to power the sub and shorting the other. It acts as a brake to help cotrol the sub.
    If I were to power one coil and short the other on my 12" DVC. My amp would put out [email protected] and this should aid in not bottoming out the driver. Is there a particular drawback(s) to what I am thinking? To sum up a 142L using a full length 4" Flared port powering one coil with the other shorted.
     
  2. ThomasW

    ThomasW Cinematographer

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    The 'fixes' you listed aren't going to solve the problem.

    Have you checked for air leaks?

    The fundamental issue seems to be that you're trying to play to loud with a single 12" driver. To solve the problem you need to buy a second driver, or sell yours and get a 15"
     
  3. stephanX

    stephanX Stunt Coordinator

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    it should be able to play sub25hz no prob. but that IS a tiny box. if you tune it right, you can go to a big enclosure(ported) and actually use LESS escursion. First plot the same sized sealed box then find out where the most excusion happens with your power, then port it to that(if that seems a reasonable place to port, it shoudl be around the FS of the driver). If you want better low end you can tune a bit lower, but the bottom line is that properly applied porting can increase output and reduce excursion at low frequencies.
     
  4. ThomasW

    ThomasW Cinematographer

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    He can run all the computer sims he wants but, until he provides some in room SPLs it's all speculation.
     
  5. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Thomas is correct. Check for leaks, the most overlooked "fix" in subwooferdom.
     
  6. Jack Gilvey

    Jack Gilvey Producer

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  7. Geoff L

    Geoff L Screenwriter

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    Those where the 3 things that came to mind first...

    1)~ SS-infra/filter:
    Yes/No if yes where and slope.

    2)~ Air leaks:
    Tiny ones when ported are not usually a big problem "tho NOT good", but larger ones can cause big problems.

    3)~ The Spl being attempted:
    Spl he's getting/running at the "listening position" & the (freq/freq range) he's having problems with the "driver bottoming"...

    Spl being attempted is (the most important thing to know at the listening position).
    If 1 and 2 are good, then most likely you need more driver swept volume as Thomas mentioned. Or possibly a DVC-12 cab re-design & tune that digs less deep and will produce more spl from 25 and up.

    ===>
    How big is the area your trying to fill..???
    ===>
     
  8. jeff lam

    jeff lam Screenwriter

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    my question exactly...

    Also what type of levels do you want to get?

    If it was built correctly and everything is according to plan and its just not enough, you will need either a more powerful sub (driver and amp) or multiple ones to get higher spl's in your particular room.
     
  9. MarkRoberts

    MarkRoberts Stunt Coordinator

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    I am at work right now but when I get home I will make a test cd and give you guys some measurements.
    The Rythmik amp comes with a 12hz filter but there is instructions on there site to change it. I installed a 54kohm resistor which should be close to 20hz filter according to their site. I will double check that too.
    The enclosure has the port length spec'd out in adire's plans FP-3 port with a center of 8 3/8"? Something like that. I have checked and rechecked for air leaks the only air seems to come from the port so I think I am good. I did screw up the enclosure in that I glued the first panel to the wrong side so my driver is right by the edge of the enclosure :b. I also lined the cabinet with some eggcrate type stuff.
    The room is rather small at 11.5 X 12 X 8.5'ceilings though there are two opening into adjacent rooms one being a 5'doorway and the other being a doorway(no doors). So technially the whole first floor is open. It is around 750 sq. ft.
    It isn't really spl I am after I notice there are frequencies missing. I watch movies allot and I have my main sub as a reference. Mirage BPS-400 400W dual 12" sealed.
    I was never expecting the DVC to beat it but I know it isn't as good as it can be [​IMG]
     
  10. MarkRoberts

    MarkRoberts Stunt Coordinator

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    I double checked Rythmik's site and the filter should be right around 20Hz.
    Will this filter be good enough for the 142L design?
    I take it you guys feel the 250W isn't too much for the driver.
    I plan on picking up the sonotube tomorrow morning. I gotta drive 1 hour away to get anything over 12" in dia. [​IMG]
    I thought of something that might or might not be causing some problems. My house is an older fixer upper (1st house) anyway the flooring under the carpet isn't plywood or other common subflooring. It is a series of boards that run across the joists at an angle. There is definately gaps between them 1/8" or so. Could I just be losing some output into my basement? I will have to go down there while I am running the test tones. The gf isn't down with the friday night test tone jamboree. So I will post my measurements hopefully tomorrow.
     
  11. stephanX

    stephanX Stunt Coordinator

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    "The gf isn't down with the friday night test tone jamboree"

    Well said![​IMG]
     
  12. MarkRoberts

    MarkRoberts Stunt Coordinator

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    Alright guys I got a chance to do some measuring. I downloaded some test tones and sweeps from here (Thanks ThomasW!)
    Okay with the 15HZ-80Hz sweep I found I was actually getting decent amounts of output down low I measured [email protected] uncorrected. However when the sweep got to 1:10 all the way through the 2min. mark I got nothing over 66db uncorrected. There would be the missing frequencies I spoke of. I tried several times to get the actual reaadings for each incrementing tone but I was trying to read the meter and the time code on my dvd player. Plus keep an eye on my 4 Year old.
    This was taken after setting the sub to 75db using the recievers test tones (00db)from the listening posistion at -10db. Which is my normal listening vol. I will take some comparison measurements with my Mirage for reference.
     
  13. MarkRoberts

    MarkRoberts Stunt Coordinator

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    I believe the frequencies I am "missing" are from 20Hz to 26Hz. They should be the tones from 1:00-2:00 on the sweep from the description given on the site I got it from. I was suprised at the output I was getting below 20Hz.
    After the 2min. mark the meter started to climb again. Should the 142.5L solve this or do you guys feel I have some sort of room problem. Sorry I don't have comparison measurements of my Mirage yet. I have made 3 bad cd's trying to use the individual test tones versus the sweeps. Not all of them are converting over from mp3 to wav's properly.
    I got the sonotube yesterday and started working on it already. I used this site to determine the size of the enclosure. Each end will have a 3/4" plug and a 3/4" cap. I already had a FP-4 kit here so I am using the full length according to adire's plans.
     

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