1. Sign-up to become a member, and most of the ads you see will disappear. It only takes 30 seconds to sign up, so join the discussion today!
    Dismiss Notice

Anyone plug their ports for music?

Discussion in 'Home Theater Projects' started by PaulDF, Aug 9, 2003.

  1. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Trophy Points:
    0
    Does anyone often plug or unplug the ports on their subs, depending whether they are listening to music or HT?

    I have gotten into the habit of doing this, to avoid the high group delay with my large vented Tempest. Modelling in WinISD I see that the GD is much lower, but the max power also drops a lot below 30hz. Respectively, the cone excursion goes VERY high below 30hz.

    Am I risking damage when I plug my ports? Or is 150+ liters just too large for a sealed enclosure?
     
  2. David Giesbrecht

    David Giesbrecht Second Unit

    Joined:
    May 28, 2001
    Messages:
    306
    Likes Received:
    0
    Trophy Points:
    0
     
  3. George W

    George W Stunt Coordinator

    Joined:
    May 25, 2001
    Messages:
    91
    Likes Received:
    0
    Trophy Points:
    0
    Hey Paul,

    I plug my ported 85L shiva often for music and I've never run into any problems with it. Does seem to tighten the sound up nicely.

    George
     
  4. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Trophy Points:
    0
    Well, I am debating whether to build a smaller enclosure or change my tuning. (to suit my amp more safely). I was leaning toward shortening my ports to change the tune from 16 hz to 20. This way, I would not lose any SPL or extension, and keep the excursion down, and up the power handling.

    But, the group delay increases by a substantial amount, so for music this is not good. At least as far as I can tell. So, if plugging the ports is a safe way of lowering my GD, then this alteration might just work.

    Until I get tired of plugging and unplugging. And realizing AFTER I watch a boombastic DVD that I forgot to pull the plugs. And, that what I thought was a flat response through my BFD was really who knows what because the plugs were still in! (Actually, I wonder what would really happen in this case? perhaps nothing other than loss of lower extension. I have yet to plot the curve of my sub sealed...)

    My wife can sense money going up in a cloud of musical smoke, the minute I start playing test tones! [​IMG]
     
  5. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    1
    Trophy Points:
    0
     
  6. Chris Popovich

    Chris Popovich Stunt Coordinator

    Joined:
    Oct 18, 1999
    Messages:
    64
    Likes Received:
    0
    Trophy Points:
    0
    Good point there Jack - how much of a difference do you really hear?

    When I've plugged the port on my designs, I didn't hear that much of a difference. Of course, most people won't say that because we're "supposed" to be able to hear 1ms of difference in something like group delay or +1dB at 16Hz... and it isn't like that.

    On the other hand, if it makes you rest easier, then by all means go for it. Any vented/PR design I've made has alwasy been tuned below 20Hz, and especially for music, there justisn't that much info down there, especially high level info. You aren't going to *hear* much GD at 20Hz no matter how bad it is -I'd be more concerned with 30hz on up.

    Sealed designs are simple and great, but I'd put my Tumult/PR box up against any of 'em.

    Cheers,
    Chris
     
  7. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Trophy Points:
    0
    Jack, you are right. I didn't actually mention the difference in sound that I heard while in use. And afterall, this is my main concern... how it sounds!

    When I plug my ports, I do notice the bass a little bit tighter, and also less boomy. Of course most of this could be psycological because I've read "this is the way it is...", but it could also be legit.

    I've been trying to understand group delay for a while, but it seems the best way to learn about it is to play with it a lot.

    So what about my original idea to shorten my ports to bring the tune to 20hz? All else is better on paper, but GD goes up. Should I make this mod, or redesign from square one?
     
  8. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    1
    Trophy Points:
    0
     
  9. Brian Knauss

    Brian Knauss Stunt Coordinator

    Joined:
    Jan 12, 2003
    Messages:
    61
    Likes Received:
    0
    Trophy Points:
    0
    My thoughts:
    The sound might be tighter, but the enclosure is far from optimal for a sealed box.

    You have less chance of hurting a sub in a sealed box than a ported box. With a ported, the vent allows for higher excursion at the lower end and this might cause a problem if the sub goes into over-excursion.
     
  10. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    1
    Trophy Points:
    0
     
  11. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Trophy Points:
    0
    Jack - thanks, its good to hear you are quite pleased with the EBS alignment! I also now understand that the changes I/we are seeing here with GD and FR are pretty minimal, and perhaps really not that noticable.

    The Tempest I built is 360l, tuned to 16 hz. The amp is the AVA 250 with a filter at 18hz. The baffle might come off, with some work. I'd rather not try it though. The ports are caulked into place (PVC), so they might come out. I think I have a plumber friend who has an internal PVC pipe cutter, it should reach 10 or so inches inside.
     
  12. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    1
    Trophy Points:
    0
    Looking at that in WinISD pro, I'd leave it just the way it is, nice looking curve.
     
  13. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Trophy Points:
    0
    Well thankyou. But isn't 250 or 270 watts a little much for it? A 200 watt amp would have been a little "safer" in my opinion.
     
  14. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    1
    Trophy Points:
    0
    That's about a 1dB difference, I wouldn't worry too much.
     
  15. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Trophy Points:
    0
    Yes, Jack, but I was talking more in terms of excursion and power handling... WinISD shows that 200 watts would have been "safer" for my enclosure and tuning. I'm just trying to avoid potential damage, as at times I push it quite hard! [​IMG]
     
  16. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    Trophy Points:
    0
    Since a Tempest can handle ~750 watts to the driver (both VC's driven) you'll clip the amp long before you overdrive the woofer
     
  17. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    1
    Trophy Points:
    0
     
  18. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Trophy Points:
    0
    Okay, thanks Jack. I'll leave it be.
     

Share This Page