Sealed Tempest results.....

Discussion in 'Archived Threads 2001-2004' started by TerryC, Mar 4, 2001.

  1. TerryC

    TerryC Stunt Coordinator

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    Spent the day making a sealed Tempest and the results are much, much better than I expected for a sealed sub. No subjective comments yet as I've only finished it so there's only measurement data to find here.
    Here is a Pic of the finished prototype sub:
    [​IMG]
    Dimensions (H x W x D): 22 X 20.25 X 21.25
    Volume after bracing/driver: 3.88ft3
    Qtc: 0.75
    Stuffed with 48oz's of Polyfill(not sure how much this effects Qtc?)
    Here are some measurements taken at the seat as well as after EQ'ing:
    [​IMG]
    Red-No EQ Seated low SPL
    Pink-No EQ, Mic Placed 0.50" away from dustcap
    Green-EQ'd, Mic Placed 0.50" away from dustcap. Attenuated 60hz area and boosted 20 to 40hz to make the sub almost flat nearfield
    Blue-Seated position after the nearfield EQ'ing
    One thing I hope some of the more experienced here can answer, how does EQ'ing change the Qtc of the sub if any at all??
    Here is how it compares to my Ported Mass(4.18ft3, 19hz tune) at Max SPL:
    [​IMG]
    Red-EQ'd Tempest
    Pink-Non EQ'd Mass
    Not much of a difference!! Very surprised at that myself as I'm sure others will be as well!
    Here is a graph about having multiple subs placed within my room to see if I have any cancelation issues. Please note that no EQ used on this test as I do not have another RCA to Phono cable to allow me to have both channels running individually. Both channels are on their own but run off the same input vs, their own input. Will get that cable this week and EQ both subs for bass nirvana. [​IMG]
    [​IMG]
    Subs are located in each of the rear corners on either side of the listening position.
    Red-Tempest on its own(notice it is located in the better corner of the two)
    Pink-Mass 2012 on its own
    Blue-Paradigm Studio 100's on their own
    Green-All three running together, notice the slight cancelation at 75hz, possibly something to be concerned for some but seems okay to me. If the volume gets turned up this cancelation becomes more noticeable, other frequencies get louder but the 75hz area stays where its at.
    Last graph is the different phase settings. [​IMG]
    Nothing was touched except the phase setting of the sub output on the Sony.
    It pays to play with the phase setting which I've already learned long ago. I just put this up for others as an example of what improper phase can do. I get much better response from my rear subs in reverse phase.
    That's it, will post some subjective stuff in the weeks to come. So far I really like the idea of a sealed sub EQ'd with lots of amp power. Seems to make a great combination. Comparing these results to the Velodyne FSR-15 I tested a while back it looks to me as if this sub will annihilate the FSR in about the same sized box. Maybe sometime in the next couple of months I'll be able to compare the two in the same room.
    Terry
     
  2. Julian Data

    Julian Data Second Unit

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    Wow, Terry you have surely outdone yourself! [​IMG]
    I see with all the subs running you are pretty level so to speak. I am pretty impressed!
    Where were the subs located?
    JD
     
  3. Jack Gilvey

    Jack Gilvey Producer

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    Nice job again,Terry.
    Polyfill will lower Qtc, as it increases the apparent Vb.
    Were the Mass and Tempest in the same box size?
    The results seem to me to be about as expected, as the Tempest needs loads of eq below 30Hz to stay flat, and loses lots of output because of it. The Mass seems better suited to a small sealed box, and would have a much lower Qtc in the same size,probably leading to better subjective results as well.
    There is a circuit I've read very little about,called the Linkwits transform, that can eq response and maintain a lower Qtc,or some such thing. Someone else will have to comment on it. You still need lots of driver and amp headroom,though.
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  4. TerryC

    TerryC Stunt Coordinator

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    "Where were the subs located?"
    Back of the room on either side of me. I'll take a picture once the room is cleaner.
    Terry
     
  5. Julian Data

    Julian Data Second Unit

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    Kewl..
    I was planning to move one of my subs to the LF and leave one at the LR of the room.
    JD
     
  6. TerryC

    TerryC Stunt Coordinator

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    "Polyfill will lower Qtc, as it increases the apparent Vb."
    Thanks, I knew that part but don't know by how much?
    "Were the Mass and Tempest in the same box size?"
    I think my post confused you as I wasn't clear but this is my ported Mass, 4.18ft3 tuned to 19hz. That is why I am so blown away(i've updated the post to include this) as sealed subs aren't supposed to compare to ported subs. I must stress though that my mass is under ported and arguably will get a few more db at tuning than what is shown here but the results are still impressive none the less. Also I have yet to listen to single thing other than test tones. So will update within the next few days with a few first impressions.
    "There is a circuit I've read very little about,called the Linkwits transform, that can eq response and maintain a lower Qtc,or some such thing. Someone else will have to comment on it. You still need lots of driver and amp headroom,though"
    Sounds cool but I'll only be using my Behringer FFP, I'm still interested in learning about it though.
    Terry
     
  7. Jack Gilvey

    Jack Gilvey Producer

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  8. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    As usual, great info from Terry.
    quick thoughts
    1)to flatten the 15,it looks like you have to start cutting around 32-35hz. That's fine, but it's also going to reduce a lot of the claimed advantages for a high *RE* driver design too.
    2)once you start EQing (boosting)down low,you eat amp headroom...and the driver needs to be robust enough to handle the additional excursion. The tempest is a great 15 though, so it will probably work well.
    3)imo---and i'm sure others disgree, the mass 12 is being choked by a single 4" non flared port. With a driver like the mass12...>19mm of clean motor throw(the longest ever measured in a review by Tom Nousaine btw)...and no limits on the voltage(amp)...dual flared 4s would be the minimum imo. Based on my own research(which included measuring single 4,dual 4,single 4 flared,and dual 4 flared against one another using various 12-15" drivers a while back)...I'm estimating the mass 12 will pick up a minimum of 3dB down low.(with dual 4" flared ports).
    if you accept that assumption, then the mass12 would have about the same clean lowend headroom as dual sealed tempests.
    IMO--it's best to use the tempest in very large ported enclosures,but as terry has pointed out--with a bunch of EQing and a LOT of amp headroom, it can work really good in a reasonably sized sealed enclosure too.
    TV
     
  9. TerryC

    TerryC Stunt Coordinator

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    Tom,
    I am in total agreement that more port will give the Mass more SPL near tuning, I noticed John J. didn't think that's the case so thats why I said arguably. I can tell just by the port noise at 20hz it's undertuned and at the very least THD at tuning would drop a WHOLE bunch with more ports!
    The corner the sealed Tempest is in now always has that plant in it so I couldn't put the tall(compared to this Tempest) sonosub there, wife won't allow it. To give you an idea how much better that corner is(take a look in graph number three where the Tempest performs better than the Mass but when its in the same corner as the Mass as in graph number 2 the Mass slightly betters the Tempest. Proves positioning is everything) after putting all my equipment away I decided to run a 15hz signal and turned the volume up until the sub wouldn't move my rat shack meters needle any higher and it hit 101db(uncorrected 12feet away that's 112.5db plus real world), I think I am going to like this sub! I know most of the subs I've built would probably do better above their tuning point by 2db to 6db compared to this but this is no slouch in its own right and is smaller to boot(SAF). I have a feeling this sub is going to win me over as it can go in a corner that is going to make it perform better than the kiddie wall the mass is against which hinders it and any sub placed there.
    My big test is how it will perform with lost in space when EQ'd and at reference? I'll be sure to put it back into the corner the mass is in to make it fair and see if I hear any weird noises, being sealed I'm not sure I will??
    I'll also run a max SPL for it on the good corner to see how it comes out.
    I hope music sounds good with this EQ boosting? What kind of geek builds a sub and the first thing he does is run sine waves? [​IMG]
    Terry
     
  10. Patrick Sun

    Patrick Sun Moderator
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    Nice job, Terry. When you find out the kind of geek you are, let me know, I'll lay claim to being one too. [​IMG]
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  11. Jack Gilvey

    Jack Gilvey Producer

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    Tom,did you post these results anywhere? I'd love to see them. I'm very curious at to the effect of the flare on the ubiquitous 4" port kits.
    And,of course, it goes without saying (I'd hope) that if we want to compare these drivers solely on output capability (which doesn't appear to be Terry's goal), we'd have to stick the Mass in a sealed cab of appropriate size to get the same Qtc. That would be a very interesting comparison, as the vaunted 19mm clean stroke of the Mass allows it to get closer to the displacement of the Tempest (which,of course,doesn't need that much stroke for higher displacement) than any other 12".
    ------------------
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  12. DanWiggins

    DanWiggins Second Unit

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    Terry,
    Nice data! Here's some hopeful-answers to your questions:
    1. Stuffing will lower the Qtc. I estimate that, your 3.88 cubic foot box has a Qtc of 0.744 unstuffed; stuffed with 48 ounces of polyfill, you should have a Qtc of around 0.72.
    2. You got some wicked room modes around 45-75 Hz, don't you? [​IMG]
    3. EQ will affect the effective Qtc of the system. Can you post/describe the EQ you used? It looks like you probably used a roughly 6 dB "shelf" type EQ, with the range below 35 Hz generally lifted by 3 dB, and the range above 40 Hz generally lowered by ~3 dB. Close enough?
    4. The Linkwitz Transform (LT) was fully defined by Siegfried Linkwitz (you've heard of Linkwitz-Riley crossovers? Same Linkwitz). There's a pretty good description of the LT at http://www.trueaudio.com/st_lkxfm.htm.
    Additionally, Siegfried has a website at http://www.linkwitzlab.com Let us know how it turns out with LIS at reference level!
    Thanks again for the data,
    Dan Wiggins
    Adire Audio
     
  13. TerryC

    TerryC Stunt Coordinator

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    Dan,
    Here are the quick EQ settings I used to get the semi flat response nearfield.
    20Hz +5db 25/60 octave
    25hz +2db 23/60 octave
    40hz -2db 20/60 ocatve
    60hz -5db 35/60 octave
    Terry
     
  14. DanWiggins

    DanWiggins Second Unit

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    In the words of the great communicator, Homer Jay Simpson, "Doh!"
    I see now the scale is 10 dB per division... That's what I get for staring at LAUD all day, with the default 5 dB per division... [​IMG] So I guess you have 10 dB of total EQ "swing" rather than the 6 I estimated above... [​IMG]
    Thanks!
    Dan Wiggins
    Adire Audio
     
  15. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    >>>Tom,did you post these results anywhere? I'd love to see them. I'm very curious at to the effect of the flare on the ubiquitous 4" port kits.
     
  16. TerryC

    TerryC Stunt Coordinator

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    Dan,
    So given my EQ what do you think the final Qtc of the sub is?
    I did some listening tonight and I am SUPER impressed. I can't really compare it to my Mass though as its in a different corner so read the following with that in mind.
    On the Lost in Space opening I calibrated +6db over reference and it did distort very, very slightly, overall very livable and is quite a bit less then the popping noise I get from the Mass. I "think" this is largely do to the crappy corner the mass is located in as it needs to be set higher than it would be in the good corner. I also ran U-571 with both subs running I absolutely fell in love with the combo, it's almost the same feeling/grin I had when I built my first DIY.
    Amp draw in the good corner is less than the Mass in the crappy corner. Even with EQ and only using one channel of my amp I don't go into clipping territory. With the Mass on it's own in the crappy corner I can easily overdrive the amp, but again I think this is a function of that crappy corner. The mass needs to have the gain on the amp set 4volts higher then the tempest in the good corner to reach equal levels.
    Music sounds great so far, my critical eared buddy Lewis is coming over on Saturday to do some of the critical listening with me.
    Overall I am overjoyed that I built this sub. It's great to run sine waves at 15hz, through to 25hz and get no port noise! Although with single frequency tones at super high SPL's I can distinctly hear when THD starts to become noticeable, but even then it's still lower than the port noise of the ported subs I've built when running sine waves in the high teens.
    My subjective opinion so far given it's size and performance is that this sub is a killer combo and it's going to be rebuilt from scratch with a nice finish(thinking along the lines of a Revel B15 look in Birch right now, any suggestions are welcome) and will be a permanent addition to my home theater as I like it that much! I'll still be using my Mass where it's currently located as I like the extra SPL I get using two subs. 115db at 20Hz is accomplished without a problem or without needing huge water heaters which although I LOVE my wife would leave me or at the least banish me to the couch. [​IMG]
    I'll be doing some spectra measurements(frequency sweep and Max SPL) tomorrow with the Mass and Sealed Tempest in the good corner. Will record the opening scene of Lost in Space individually in the good corner and then both running in their respective corners. Will plug the port of the Mass sub as well making it have a Qtc of 0.58 for a couple runs too.
    Terry
    Tom, I'd love to run some THD tests but my severely underported Mass it makes that a REALLY unfair test. When I have some time I'll do a test mule using one of the spare 20" Sonotubes with the dual ports coming out of the top just to make it more fair. I just realized, if you'd like I can do it with the port plugged tomorrow? What frequencies would you like to see, please remember I'll be short on time so a limited number would be nice.
     
  17. Jack Gilvey

    Jack Gilvey Producer

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  18. Patrick Sun

    Patrick Sun Moderator
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    Yes, it would have been interesting to see just a comparison between a NF 4" port and a flared 4" port and how more more dBs you can squeeze out of the flared port, everything else being equal.
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  19. DanWiggins

    DanWiggins Second Unit

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    Terry,
    I figure your effective box response is approximately Q=0.68, with Fc of 20 Hz. Thanks for the feedback on the sound, too... [​IMG]
    As far as the amp demands, using a standard LFE crossover (80 Hz/second order/Q=0.707), your F3 points BEFORE equalization should be around 30 Hz and 90 Hz, based on a peak at 53 Hz (this is true +0/-3 dB references). Across that bandwidth, the system should average around 86.5 dB SPL at 1W, 1m. So it's relatively efficient; that may be part of the difference you're seeing in amp power needed for a given level. Different corners can affect that, too!
    One thing to consider about seeing how the two different sub locations work would be to move the smaller sealed cabinet to both locations, and measure at your listening position. This may be easier to do than move the larger vented cabinet to the other corner.
    Lastly, is that plant going to stay there? If so, try inlaying the corners of the sub with strips of solid greenheart. Rubbed with heated teak oil (yes, you want to get the oil up around 110 degrees F), it takes on a beautiful deep green color, which may be complimentary to the pot. Buy a chunk and experiment!
    Dan Wiggins
    Adire Audio
     
  20. TerryC

    TerryC Stunt Coordinator

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    Well I only had time to run a few tests before my wife got home from the stables. Mic placement is at the seat 8" from the corner loaded subs.
    Here are the results of both subs placed in the "good" corner using a 100-15hz sweep taken at my seat:
    [​IMG]
    Red-Max SPL of the Tempest on its own
    Pink-Max SPL of the Ported Mass on its own
    Blue-sensitivity of the Tempest-no volume was not changed when changing out subs
    Green-sensitivity of the Ported Mass-no volume was not changed when changing out subs
    It's interesting to see the Sealed tempest can come within a 1.5db of the Ported mass while only using 2db of EQ boost down at 20hz. I had to lower it from 5db earlier as the sub was showing too much stress as well as sucking up all the available 500Watts of power I was using.
    I'm only running 500Watts into the Tempest and 700Watts into the Mass(only used a single channel). I used the clip meters on my Mackie as the maximum volume level as the guide for these tests. I ran the sweep and kept turning down the volume until both subs could run the full sweep without lighting up the clipping light and overdriving the amp. I could have used more power by bridging the amp and increased the SPL up in the higher frequencies but both subs were showing sines of stress in the high teens so I considered this good enough because what's the use of being able to run 120db at 30hz when that power level will distort the sub majorly at 20hz and below?
    You can also see the ported Mass goes louder with the same input signal. This shows just how crappy the corner is where I have to boost the mass by setting the gain on the Mackie to a setting that lists as 4volts higher!
    Both these subs proved to be super performers. Each on their own was able to hit the reference mark throughout most of their usable range. This is quite a feet for any sub!
    Here is the Lost in Space test. (Mains were disconnected.)
    [​IMG]
    Red-Tempest
    Pink-Mass
    In this test I calibrated to +3 to +4db over reference with only my rat shack meter so in real life this is about +5 to +7db over reference. I was encouraged with the higher sensitivity I had with this corner so I decided to see if that setting would "POP" the Mass, unfortunately it did. Where the Tempest cruised through with only a hint of discomfort the Mass made its well known pop during the two sections that seem to cause everyone problems.
    I couldn't tell the difference between each sub other than the "pop" the mass made. Both do their jobs extremely well in this role.
    Its interesting to see the 30Hz area is the signal that causes the Mass to pop, before it popped the graphs were nearly identical. Only when it the Mass popped did the Mass trace extend a little higher around that 30hz area.
    Will see what more I can come up with over the weekend, I found out my original impression of this sub hitting harder was a direct result of the corner I placed it in after my first tests above. After placing each sub in the good corner I have a really hard time telling them apart, if any at all! The added 20-30hz SPL this location gives is a joy, I can't belive I lived so long without utilizing it.
    Overall I'd recommend this type of sub to anyone. Its inexpensive $140 for the driver $20 for some MDF and $150 for the Behringer. This is one inexpensive sub and one hell of a great performer, it comes super close to the performance of my ported Mass and does so without any port noise and zero bottoming along with a smaller enclosure. I think those two reasons alone make it my choice if I had to only pick one as they seem to make a bigger difference to the enjoyment in my mind than a couple db extra SPL. Does that mean I'll only go sealed, hell no, if I had more room I'd still probably build a waterheater! [​IMG] But for now and with the smallish living quarters(large open concept volume though)the SAF weighs big so as it stands now this subs size to performance to cost ratio is a tough one to beat imo.
    Terry
     

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