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Ascendant Audio: Atlas & Avalanche

Discussion in 'Home Theater Projects' started by KurtJ, Jan 13, 2005.

  1. KurtJ

    KurtJ Stunt Coordinator

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    The story here started on another thread last week, and I should've started a new thread then. Received the Atlas 15 Tuesday. Came home and connected it up as per instructions, calibrated it, and fired it up! [​IMG]

    Well, with the 4 ohm amp powering the 4 ohm Atlas, oh man, what a sweet sound. I used DVE, but had some trouble with levels (saw the relevant thread after, of course) so used Avia and VE, but what worked best were the tones from my reciever. I also made a test tone disc using NCH (thank you).

    My windows resonate at around 41.5 Hz, and the dog freaks out around 35 and below. Room gain helped a whole bunch, because I was able to get 20 Hz at around 82 dB.

    3.7 ft^3 enclosure with a Q= .707. MDF is so cheap, I'm thinking about building another enclosure to get a lower Q just to see how tight it can really get. (oh no, the DIY bug has struck again).

    Anyway, the Atlas is everything and more I could have ever hoped for. I haven't been able to really listen yet, but this weekend...

    Only a few MDF mishaps and veneer probs, but nothing serious. Haven't been able to get the amp to self power on yet, but maybe the signal needs to be boosted a bit.

    If anyone knows how to post pictures, please let me know. I really want to share this first DIY with all of you.


    [​IMG]
     
  2. Jack Gilvey

    Jack Gilvey Producer

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    Nice...I've got a pair of Atlas 15's on the way for IB.



    A better option would be to use a Linkwitz transform circuit to lower Q and F3 (more Vb will only lower Q and actually raise F3, .707 is as low as it gets for F3). The 380w plate amp from Rythmic Audio can be ordered with the LT built in and Chris will configure it for any Q and F3 you want based on your present Q/F3. The wattage is perfect to get the most out of that driver in that box. In this case I'd series the VC's for a bit more Pe. I modelled this combo a lot before I decided to go with a pair in IB.
     
  3. Geoff L

    Geoff L Screenwriter

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    Jack:

    Whos Chris at Rythmik?

    Has Brian hired some help, I thought Brian the owner did all the work, LT's included on his/Rythmik's plate amps...

    Curious if I've missed something/someone new at Rythmik..[​IMG]

    Thanks
    Geoff ¥


    Edit:
    Kurt

    How big of room are you filling?

    Im with Jack n LT-ing that baby, big difference down low..

    Regards
    Geoff
     
  4. Jack Gilvey

    Jack Gilvey Producer

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    I'm sorry...Brian it is.
     
  5. Geoff L

    Geoff L Screenwriter

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    Oh, ok cool you had me scratching my head a bit! [​IMG]

    Cheers
    Geoff
     
  6. Robert_CA

    Robert_CA Stunt Coordinator

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    I picked up mine up last weekend. I'll be doing a 4cu.ft. enclosure with the Atlas's coils in series for a 6 ohm load and powering it with the 500 watt PE amp with parametric EQ. Should be real nice.
     
  7. Chad Kuypers

    Chad Kuypers Stunt Coordinator

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    Kurt,

    I am thrilled to hear that everything turned out great. [​IMG] I eagerly anticipate your impressions when you finally have a chance to really take a serious listen at some higher volume levels.

    As Jack mentioned, you also have the option of using an LT. This would get you a flatter, more extended frequency response in a sealed enclosure. Of course, I myself always love huge subwoofer enclosures. [​IMG] I'll be picking up about 3 or 4 more Sonotubes tomorrow for some testing this weekend.

    Robert,

    It was great to meet you this past weekend out at the shop. I am excited to hear how your project turns out. Have you had a chance to listen to the Atlas 15 yet? Keep me posted. [​IMG]


    Chad Kuypers
    Ascendant Audio
     
  8. KurtJ

    KurtJ Stunt Coordinator

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    Could I add an LT to my amp? It's the Rythmik 250. What other options do I have for adding an LT? How much smaller could the enclosure be with the LT?

    My living room is about 2300 ft^3, but it's open to the kitchen and the rest of the house.
     
  9. Jack Gilvey

    Jack Gilvey Producer

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    You could go very small but remember that sensitivity in the low bass falls with Vb, so pretty soon you're running out of power before you get loud enough...or anywhere near XMax. Even with unlimited wattage, it's also much easier to exceed the driver's thermal limits in a small box. Chad has a good reason to love big boxes...they allow high efficiency...more output with less wattage. With 250 watts to play with, I wouldn't go much smaller.
     
  10. RandyMathis

    RandyMathis Stunt Coordinator

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    I read about the LT.

    Am I right in that it is for sealed and not ported?
     
  11. Jack Gilvey

    Jack Gilvey Producer

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  12. KurtJ

    KurtJ Stunt Coordinator

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    I was able to get a quick test tone measurement done while the wife took our baby for a walk. (read: 30 minutes).

    These are uncorrected values
    10 Hz, 63dB; 16 Hz 83; 20 89; 25 92; 30 99; 35 92; 40 98;
    45 96; 50 92; 55 97; 60 96; 63 96; 70 89; 80 98.

    Corrected Values
    16 94.5; 20 96.5; 25 97; 40 100.5; 50 93.5; 63 97.5; 80 99.5.

    I need to down load some more test tones to about 125 Hz or so.

    These measurements were from the listening position with the sub next to the armoire w/ equipment, and the back wall. No time to move it around.

    I am surprised by the amount of apparent room gain, though. Is it possible for this much room gain?

    The subwoofer actually slid across the floor
    [​IMG] Guess I need some type of rubber feet.

    I am soo happy with the performance of the Atlas 15! Great driver, Chad.
     
  13. Geoff L

    Geoff L Screenwriter

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    You never changed the volume control on the sub or receiver once you started runing the tones, right?

    If not, would seem you have some very nice room gain down low.

    I'm to lazy to run the numbers, whats the simmed Fc & F3 for your box Q of .707??
     
  14. Robert_CA

    Robert_CA Stunt Coordinator

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    KurtJ,

    I just brought mine on line last night in my 214L enclosure which was my Tempest's former home. Right now I'm running it sealed at mid-Qts with an Amp350 (Thank's Chad for helping me get my amp fixed). The Atlas 15 produces very deep and well defined bass in this enclosure volume. It's comparable in extension to the ported Tempest and with more clean output as well. A lot different than the Tempest in SQ. When the Atlas is called upon to produce the bass, it let's you know. I played the "LOTR/ FOTR" and "I Robot" disks through it and I was amazed at the quality of sound this driver produces for the money. I will do some preliminary plotting and tweaking for the temporary enclosure on Monday or so. Once I get my 500-watt PE amp (it get's delivered on Monday) and the new enclosure built, I believe that it will only sound better. In the past, I was reluctant to go to a sealed enclosure for fear of losing some extension and impact but I don't beleive that I will lose anything going sealed with this driver. Chad really has a winner here and I'm very happy with mine even right now. Hmm... I wonder what the Avalanche 15 sounds like?[​IMG]
     
  15. KurtJ

    KurtJ Stunt Coordinator

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    Simulations indicate Fc of 41.08 and -3dB of 31.07. I went sealed for the SQ. Wanted extension, but was willing to sacrifice it for SQ. Well, not anymore!

    But room gain indicates -3dB is somewhere else. My preliminary measurements @ 16Hz 94dB. Fc seems about right, though. [​IMG]

    I can tell that the calibration is off (RS SPL errors) and the sound is not as tight as I would like. No fault of the driver. I figure maybe another couple of hours of tweaking to get the sound in the ballpark, and then maybe another hour to move it around.

    I think I'll have to move it further away from the armoire and along the wall to get it just right. I was surprised by the amount of sound created by the 250W Rythmik amp.

    My goal in listening to music (I'm 42 ) since I was about 16 was to hear a 16Hz pipe organ tone accurately reproduced. I used to attend a lot of classical concerts
    and I remember what the kettle drums sound like. I'm only a few hours away from my goal.

    The only problem I'm having is getting the amp's auto on circuitry to detect the LFE signal. I recall reading somewhere here this is common or used to be common. I wish I knew how to fix that other than getting one of those outlets from sears for plugging in a vac and it turning on when the table saw is turned on. Any suggestions?

    The 250W amp is more than enough for my system. It seems impossible for a small amp to power a speaker to such volumes. I'm glad I didn't get the Tempest. Or even the Tumult which requires much more power.

    My enclosure is 4.12 ft^3, because I added about 10% to the enclosure size for bracing and such, but it ended up being more like 2%. I will build another box at 3.7 ft^3, and ignore the bracing in the calculations. Just want everything to be as close to spec as possible.

    Probably won't make much difference sound wise, but my OCD will make me feel much better
    [​IMG]

    So, for about $350 in parts, and another $100 for supplies (mostly veneer), and $100 for a drill press from HD, I have a much better sub than I could buy for the money I've spent.

    There was one website I came across a while back that had RS SPL corrections for almost every freq but I forgot where it is. Anyone know the website? Found It.

    Also, I had a problem for a few hours accessing the forum today. Anyone have the same?
     
  16. Geoff L

    Geoff L Screenwriter

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    Yes the forum was down along with AVS and HSU at some point today.

    I have to run the numbers, your (F3 seems awful low) compared to FC with that cab Q of .707

    I don't know how small your room is, or if it's closed off, but that some killer gain!

    What program did you use to sim,,, and is your F3 in the program compensating for suspected room gain???

    Sorry not doubting you, but just seems strange on the FC to F3 for a Q of .707...But the Atlas is a different driver also...humm
     
  17. KurtJ

    KurtJ Stunt Coordinator

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    My living room is about 2300 ft^3, but it's open to the kitchen and the rest of the house.

    Using Vance Dickason's book, I calculated Fc. I used boxplot to get F3. But I used the book again to calculate F3, and got 41.08. In other words, Fc=F3. Is this right?

    Maybe my math is wrong. Two formulas were in the book (6th Ed) on pg 30. Qtc=.707, Qts=.37, Fs=21.5

    Fc= [(Qtc)(Fs)]/Qts

    = [(.707)(21.5)]/(.37)

    = [(15.2005]/(.37)

    Fc = 41.08


    Table 1.12 lists -3dB rolloff as a ratio for a given Qtc

    Qtc = .707

    F3/Fc =1.0000

    And lists a formula for this ratio:

    F3 = (F3/Fc)(Fc)

    So then,

    F3 = (1)(41.08)
    F3 = 41.08Hz

    Now, there is another formula for F3 on the same page, but I can't get the same answer as above.

    F3= {[1/(Qtc)^2 -2]}+ {([1/(Qtc)^2 -2]^2)}^.5 + 4 /2

    All This is then ^ .5

    And then * Fc

    This is a mathematics nightmare[​IMG]

    Where's calculus when you need it [​IMG]

    If anyone can figure this out, please try it. It's just that the simulated F3 doesn't seem right.
     
  18. Geoff L

    Geoff L Screenwriter

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    Short answer, FC is F3 at Qtc=.707

    I ran a very quick sim with basic Atlas-15" 4-ohm TS-params


    Box Volume 4.84-ft/137.05-lt
    *NO FILL*
    Qtc-->.707
    Qts-->.37

    FC---> 41.08 Hz
    F3---> 41.09 Hz
    F6---> 32.00 Hz -6.15 actual
    F8---> 28.00 Hz -8.15 actual
    F10--> 25.00 Hz -9.96 actual

    Can't post a graph so those will have to do. This is quick and dirty, but should be close.

    Dose look as tho your getting very nice room gain for not being corner loaded..!

    Dose your Rythmik-250 Amp have any boost built in???

    Edit:
    Chad shows VB for Atlas 15 and Qtc of .37 as 3.77ft ~{WITH FILL}~ for a Box Q of .707
    He dose not recomend a specific amount of fill... I'd suspect around 3-lbs fluffed to bring the VB up. His graph looks very close to my dirty :b F numbers for a Q of .707

    Maybe he will stop in and try to clear things up a bit for you as their his nifity new Drivers and Designs..

    Cheers
    Geoff ¥
     
  19. KurtJ

    KurtJ Stunt Coordinator

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    Well, glad to see I'm not crazy. No boost on the amp. This project was basic; now I need to get some help with the auto-on signal. The output signal from the AVR to the sub, does it increase or decrease as I adjust the level when calibrating? I can't figure out why the sub won't/can't auto-power on.

    Any suggestions would be helpful here.
     
  20. Geoff L

    Geoff L Screenwriter

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    If you AVR receivers sub out will not increase or decrease it's sub volume out when set to sub (ON/Yes), this is strange.

    +10 9 8 7 6 5 4 3 2 1 0
    0 -1-2-3-4-5-6-7-8-9-10

    Or what ever the sub out scale runs on your particular AVR, this is odd. Might be a receiver setup problem and you might want to check you manual and if no help, then post in the Receiver area with your problem.
    ~{Could be a simple problem you missed in receiver set up}~.!

    ====>
    Is it just stuck at a random sub out plus or minus number, or what?
    ====>

    If you get this AVR sub out volmue thing figured out and the sub still refuse to Auto On and Off, then Email or call Brain at Rythmik as suggested.

    Till then, guess you'll have to manualy turn it On and Off.
    You could also try a Y-adapter (dual male to 1-female) to feed both inputs on the sub and see if that helps, if your not already using one.

    ====>
    It is a DPL DD DTS Receiver correct, and not a 2 channel stereo receiver your feeding the low level inputs with right????
    ====>

    Regards
    Geoff ¥
     

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