Maelstrom excursion vs power in Adire LSPCad

Discussion in 'Home Theater Projects' started by David_P, Dec 12, 2003.

  1. David_P

    David_P Stunt Coordinator

    Joined:
    Dec 12, 2003
    Messages:
    149
    Likes Received:
    0
    Trophy Points:
    0
    I'm considering purchasing a Maelstrom and using it in a smallish (150liter) sealed box with a PE 500 or 1Kw plate amp.

    My concern? running it thru Adire's LSPCad program shows the excursion to go right off the charts... e.g. in a .577 box you can only apply about 100W to the driver at 20hz before it hits excursion limits.

    I realize that excursion is drastically higher for sealed boxes as compared to ported, but is this actually right?

    And another question? What is the perceived difference in sound quality between the different sealed boxes? For a predominant HT use, which is best?

    thanks...
     
  2. VinhT

    VinhT Second Unit

    Joined:
    Feb 14, 2002
    Messages:
    357
    Likes Received:
    0
    Trophy Points:
    0
    Seems about right, although I'd venture to say that it's closer to 200W. In a smaller .7 box (~51l), 1000W would be no problem.
     
  3. Chris.Brunhaver

    Joined:
    Sep 22, 2002
    Messages:
    15
    Likes Received:
    0
    Trophy Points:
    0
    Hi David,

    You are correct, in that the Maelstrom doesn't need a whole lot of power down low in order to reach its limits in a low Q sealed enclosure. However, I think you’re getting a bit tripped up by lspCAD’s “watts into 8 ohms” field. Because the Maelstrom is a 4 ohm driver (with the VC’s wired in parallel) the driver is seeing twice that amount of power. Still, even with that taken into consideration it takes only a bit over 250 watts of power to drive a maelstrom to full output at 20 hz in that enclosure. With this kind of setup, you should be pushing around 115 db at 20 hz in room. Still, since you mention HT as your primary application, you may also want to take a look at our vented application notes for this woofer.

    Thanks,

    Chris Brunhaver
    Adire Aduio
     
  4. David_P

    David_P Stunt Coordinator

    Joined:
    Dec 12, 2003
    Messages:
    149
    Likes Received:
    0
    Trophy Points:
    0
    I did look at those vented alignments...

    I'm not real partial to vented subs, and even less partial to PR'd subs. Every PR'd sub I've heard has been so "muddy" sounding to my ears as to be unlistenable. Vented is ok, but the size is also much larger, particularly for the EBS version.

    I wish I had a way of comparing the sound quality I'd hear with an EBS maelstrom vs. a few of the different sealed alignments (.577/.7 etc).


    Dave
     
  5. dave alan

    dave alan Second Unit

    Joined:
    Aug 30, 2002
    Messages:
    256
    Likes Received:
    0
    Trophy Points:
    0
    I'm with you on the ported/PR'd subs.

    I'm also not into buying a feature length kid's cartoon just to feel 6 seconds of subsonic rumble.

    The predominence of HT source is better enjoyed without the room gain + some dB, EBS boom anyway.

    I would put a Sadhara, or Brahma 15" in that box.

    An EBS alignment is never gonna satisfy you if you prefer a sealed .577 sub (and rightfully so, IMO).

    I would include a WM8A single board, assembled and tested Bassis circuit with adjustable 'Q' and fixed values otherwise, based on the LSPCAD model, or whatever model, from Dr. Phil (Marchand).

    The perceived differences can then be available on-the-fly for you to judge, in your own room, at any time, with any source, whereas, once an EBS alignment, always an EBS alignment.

    That's 2-300 more bucks, but you could dump 1KW into it, adjust the 'Q' as you like and smile alot, IMHO.
     
  6. Mike Keith

    Mike Keith Second Unit

    Joined:
    Jan 24, 2002
    Messages:
    324
    Likes Received:
    0
    Trophy Points:
    0
    The Maelstrom works well in both a Vented and Sealed alignment, so just model a good size enclosure that has a good compromise between the two and make a vented box with a port plug. I have 2 Maelstroms (245L sonotube) with an adjustable vent valve that will effectively close off the port and give me a .5Q sealed sonotube. In addition, you can still use a Rheostat across the other Voice Coil to further adjust the Q.

    I have tried all this and it does work but the differences are subtler than you might think, closing the port will defiantly make an audible difference but it's not as Night and Day as the modeling shows.

    I think some put too much thought into the perfect size/alignment and tuning of a sub enclosure and in reality it won’t make as much difference as many are lead to believe. The Maelstrom is a great subwoofer that will pump out more SPL for the power than anything I’ve seen for the money.
     
  7. dave alan

    dave alan Second Unit

    Joined:
    Aug 30, 2002
    Messages:
    256
    Likes Received:
    0
    Trophy Points:
    0
    Mike,

    It takes the same amount of thought to build a sub as close to perfect, for your goals and given the ingredients, as it does to approximate everything.

    After all, you wouldn't say that you can cut 1 of the sides 'pretty close' to the required dimension of your plan.

    Adjustable 'Q' in a sealed box sub is a cool thing and can definitely be noticeable. If you change the 'Q' from .5 to .7 you may see it as a 'subtle' change, but if you change it from .45 to 1.2, it's not so subtle.

    Of course, it all hinges on your placement, phase alignment and room curve, too. For Ex., huge room induced peaks and/or valleys won't be effected much by a 1 dB change that results from adjusting the 'Q'or plugging the port.

    I've built 7 sealed and 2 ported subs from 1 cu ft to 10 cu ft, messed with dual-mono, stereo and discrete LFE/RB configurations, placement, phase and time alignment, EQ and adjustable Q.

    Tweaking...or too much emphasis on perfecting the design...has made a rather huge difference in the sound and the satisfaction of the end results, for me. YMMV
     
  8. Mike Keith

    Mike Keith Second Unit

    Joined:
    Jan 24, 2002
    Messages:
    324
    Likes Received:
    0
    Trophy Points:
    0
    What I meant to convey is that all the computer modeling will only get you close anyway, so I use this as a guideline, and build a prototype to tweak to my desired target. The difference between tuning a sub to 18Hz instead of 20Hz will be almost inaudible as long as the driver can handle it. Anyway I don't mean to demean the careful planning process that some go through, just letting the laymen’s know that everything is a guess until the box is available for testing and some things don't make as much a difference as you might think by looking at the graphs in WinISD.
     
  9. dave alan

    dave alan Second Unit

    Joined:
    Aug 30, 2002
    Messages:
    256
    Likes Received:
    0
    Trophy Points:
    0
    Mike,

    Thanks for the clarification. I'm slow sometimes. My apologies.
     
  10. Mike Keith

    Mike Keith Second Unit

    Joined:
    Jan 24, 2002
    Messages:
    324
    Likes Received:
    0
    Trophy Points:
    0
    No problem, I wasn't at all offended, and you make some good points
     

Share This Page