I tested out a sub and here is what I got.

Discussion in 'Home Theater Projects' started by Mike SJ, Nov 17, 2003.

  1. Mike SJ

    Mike SJ Supporting Actor

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    Ok, I know car subs arent worth didley in the home theater application but I wanted to see how my basement reacts to a sub in the first place before I decided on a sub driver/enclosure design. SO, I had the neighbors kid, take his sub out of his truck and we hooked it up to an oscillator in my basement, approximately where I want to place my own sub. We set a SPL meter about a meter away and took readings. From 20Hz to 120 Hz. We got a fairly even increase from 75 db's to 100 db's with some peaks and dips here and there. I'll post the factuall #'s tommorow.
    His box has 2 10" drivers in it, if that makes any difference, and he has a sealed box, but its terribly constructed [I wont tell him that].

    It sounded low but I thought that my b&w's went almost as low as his sub.

    My ? now is is this freq curve typical of subs? and how does it compare to ohers?
     
  2. Patrick Sun

    Patrick Sun Studio Mogul

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    Sealed subs will have a gradual roll-off (which is what you observed).
     
  3. Rob Formica

    Rob Formica Stunt Coordinator

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    You didn't mention how closely you measured (ie: 1/3 or 1/6 octave) but the dips and peaks would normally be you room modes (resonances) which are also typical.
     
  4. Mike SJ

    Mike SJ Supporting Actor

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    So ported is the way to go in HT applications? the PR $/performance ratio doesnt justify itself so I guess I want a ported sub. OK will 2 tumults in a ported, corner loaded enclosure "bring the walls down"? in my last thread about biggest and baddest, I stated that that is my goal. I thought it would look cool to have a sub on either side of the couch but I guess that would create phasing problems. So my last ? is, how big of a box?
     
  5. Mike SJ

    Mike SJ Supporting Actor

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    OKOK i downloaded Winisd and Im looking at 2 tumults in a ported box, help me get my #s rught.

    what diameter do you put in, for VC or cone?
    And is Xmax one way or both?

    I know im doing things wrong because I get a rolloff at 30 HZ in a vented enclosure.
     
  6. Rob Formica

    Rob Formica Stunt Coordinator

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    My preference? I'd go with about 10cuft (+ port volume) and a 20Hz tune... which would be similar to a EBS alignment. Remember that with this amount of excursion, you will need a large long vent to avoid turbulence... which will add to the volume of the box.

    Rob
     
  7. Mike SJ

    Mike SJ Supporting Actor

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    How come the tuning freq on winisd doesnt change when you change the port specs?
     
  8. Mike SJ

    Mike SJ Supporting Actor

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    OK with your suggestion rob, I got a port length of 14 feet!
    I have to be doing something wrong, someone help me?
     
  9. Patrick Sun

    Patrick Sun Studio Mogul

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    Why don't you use the Adire version of LspCAD to model the Tumults?
     
  10. Mike SJ

    Mike SJ Supporting Actor

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    they dont have the tumults spec'd in either only tempests
     
  11. ClaudeL

    ClaudeL Stunt Coordinator

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    This will be hard to port the Tumult unless you decide to build an enclosure which has a long depth and smaller length / width with a big flared port. So for a vented Tumult box, the best solution would be, in my opinion, to use a slot port or passive radiators instead of using a big flared or straight port if that was your idea...
     
  12. Patrick Sun

    Patrick Sun Studio Mogul

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    If I were you, I would pester Dan Wiggins at Adire to get the Tumult specs incorporated into their version of LspCAD.
     
  13. Greg Yeatts

    Greg Yeatts Second Unit

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    I have a Tumult in a 178 liter enclosure tuned to ~19.5 hertz. The port is 6" in diameter and 27.5" long. I am using huge flares. In room, the bass is flat to 14 hertz. There is no port noise. I use a 1,000 watt amp. I would try to download Unibox for box modeling if you have Excel.
     
  14. Mike SJ

    Mike SJ Supporting Actor

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    "I would pester Dan Wiggins at Adire to get the Tumult specs "

    well heck then he'd just keep my name on the back of the backorder list for years. Im curious to know the specs for this "new" monster sub driver he teased us all about that will be featured @ CES 2004. he claims 20Hz reference with no enclosure... hmmmmmmmm

    Greg, that box sounds really feasable. do you use a BFD?
    and how large is you room, dimmension wise?
     
  15. Mike SJ

    Mike SJ Supporting Actor

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    oops
     
  16. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    I havn't heard much about vented tumults. All I've seen is tumults with 2-3 15" or 18" passive radiators. Those things are beasts and applying a tube port with ideal specs may turn out ridiculous.

    Parts Express sells 15" passive radiators for $40ea. Those are the cheapest I've come across. Others I've seen are like $100 for the 18" PRs.

    A passive radiator does the same thing a port does. You just have to make sure you add weight (tune them) accordingly and use enough of them so the PRS don't bottom out. The benefit is you don't need to add a huge port.
     
  17. Rob Formica

    Rob Formica Stunt Coordinator

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  18. Mike SJ

    Mike SJ Supporting Actor

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    Well port size and enclosure size really doesnt matter to me, even if the port has to be outside the box, maybe something like the Hemholz resonator [sp]. right now, im imagining a large box behind my couch with 2 donfiring drivers, and im leaning twoard the tumult. I want to finish it like my bar and cap it to look like a couch table with a granite top. 90"+ x 36"+ x 21"+ is about the size Im thinking of.
     
  19. Greg Yeatts

    Greg Yeatts Second Unit

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    Mike

    My Tumult is in the corner of a room that is 9'X 23' X 14'.

    I have a massive peak at 45 hertz in my room. I use the BFD to flatten this peak.

    I think that porting a Tumult is very feasible if you do not intend to port below approximately 19.5 hertz in a moderate sized enclosure. Porting below 19.5 hertz produces crazy port lengths and a saddle (bump)in the frequency response around the tuning frequency. The lower you go the bigger the bump.

    Passive radiators can be used to effectively tune lower than 19 hertz. The porting modeling I did indicated that output was a little soft at the very bottom of the output range anechoically, but this would not be a problem in-room. My reservations about PR enclosures are only about the cost. I have built a PR enclosure in the past that was most impressive.
     

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