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Tempest questions

Discussion in 'Archived Threads 2001-2004' started by RobW, Jan 27, 2001.

  1. RobW

    RobW Member

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    I'm starting to get back into some calculations in WinISD, but I don't have the values for Pe or Z. What are they? Do they make a difference?
    Also, has anyone built a good Tempest sonosub yet? Are there any good webpages for a Tempest sonosub? Thanks.
    Rob
     
  2. Greg Monfort

    Greg Monfort Well-Known Member

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    Pe = peak power handling
    Z = nominal impedance
    Yes.
    Don't know.
    Forget WINISD. Go to Adire's site and download the Lspcad freeware for their products, and learn how to use it, if you want the best in-room response from your design.
    GM
    ------------------
    Loud is beautiful, if it's clean
     
  3. RobW

    RobW Member

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    Is Pe the same as Pmax? That's the only power handling figure on Adire's site.
    Also, does Z depend on how the sub is wired? How should I wire it? What are the advantages and disadvantages?
    You know, I used to know all this stuff, but I forgot it all. Don't make fun of me. School made me forget everything. [​IMG]
     
  4. Patrick Sun

    Patrick Sun Moderator
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    Pe=750W
    Z=4 Ohms.
    I have a modest Sunosub III page detailing its construction, but you should probably go larger than 5.75 ft^3 (internal volume) if you want a "killer" Tempest-based sub. Just click the link below.
    Once I get done re-tooling Sunosub II, I'll be putting up a page for its construction as well (pretty much the same principles involved).
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  5. RobW

    RobW Member

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    Hey, Patrick. Yes, I've seen your Sunosub pages and they have helped a lot in the construction aspect of my sonosub plans. Those detailed construction notes are great. Keep up the good work.
    I downloaded LspCAD, preloaded with the Tempest, so I will play around with it and learn how to use it (much more detailed than WinISD).
     
  6. RobW

    RobW Member

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    A few questions:
    Which would be preferable? Say, 3 4" ports, or 2 5" ports? The 3 4"s give the lower mach (.04 to .05), but I've heard that larger diameter ports are better. What differences would either make?
    Is there an advantage to using flared ports? What, if any, calculations, do I have to make to compensate for the flares?
    After I decide on the enclosure volume and port setup, do I have to compensate for the ports and driver by enlarging the enclosure to get the desired specs? Does anyone know the volume of the Tempest?
    Thanks
     
  7. Patrick Sun

    Patrick Sun Moderator
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    1. It would depend on how long the 4" ports need to be. The most common heuristic advocated by John J. from Stryke, and with no disagreement from Dan from Adire, is that you should aim to have a port length no more than 5 times the width of the port, so if you use 4" wide ports, try to find a design that will allow you to use 20" long ports (or less). For 5" wide ports, 25" long ports should be your max port length. Otherwise, if the port length gets too long, you may encounter pipe resonance, and the port doesn't function as a springy resistance to the rest of the enclosure system anymore. So, yes, a port can be too long to be an effective additon to the enclosure for the subwoofer.
    Case in point: My Sunosub II (Tempest-based, 10 ft^3 internal volume) was designed with a tune of 16Hz, but that called for three 4" wide ports 36" long (vent mach of 0.04). Well, it just didn't sound that great, and the ports were too long, and thus, I'm now reworking Sunosub II by slicing off the existing bottom endcap and creating a new bottom endcap. I will be using just two 4" wide ports 20" long (vent mach is now 0.08, but still acceptable). Learn from my folly. If I can somehow fit 2 flared ports on the bottom endcap along with the 15" wide Tempest driver, I will utilize the flared ports, otherwise, I won't.
    2. The advantage to using flared ports is to get a little better power compression capabilities for the port, to reduce the turbulence from the port. (At some input power point, no matter how much power you send to the subwoofer, it won't result in any more SPL output, a flared port gives you a little more usable power before hitting that wall for input power) If you use the Precision (flared) Port, whatever your final port length needs to be, just add 1" to the final end-to-end length of the flared port. So if you needed an 18" long flared port, you have to cut the center pipe down so that you wind up with 19" of total length to the flared port assembly.
    3. Yep, once you decide on the needed internal volume, you have to add in the volume that the ports take up in the enclosure, and also the driver. I use 0.18 ft^3 for the Tempest driver. It won't make a huge difference in performance if you're off by the amount of the driver. I have a spreadsheet that allows me to put in the number of ports, the port width, and then I just change the height of the sonotube to get to target internal volume. It's a little kludgy, but it works for me.
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  8. Greg Monfort

    Greg Monfort Well-Known Member

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    Hey Pat, why two 4", when you can get more cross sectional area, same vent mach, stay within the 5x 'rule', and my personal limit of 24", with a single 6" pipe?
    GM
    ------------------
    Loud is beautiful, if it's clean
     
  9. Patrick Sun

    Patrick Sun Moderator
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    Rob, sorry to hijack your thread for just a second...
    Greg, well, just blowing the numbers through WinISD, the vent mach goes up to 0.15 using one 6" wide port about 25" long (24.8"). Actually, my problem is finding a 6" wide port, any ideas where I should look in Atlanta? Should I use another Quikrete tube from Home Depot (I don't think they have them in the 6" wide variety, mainly 8" and wider, but I'll check anyway).
    Really, I wouldn't mind going with a 6" wide port, makes life a lot easier routing out one hole instead of two. [​IMG]
    Are you getting a smaller vent mach number with a different sim program?
    (I think I should just start another thread on porting possiblities for Sunosub II, eh?)
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  10. David Judah

    David Judah Well-Known Member

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    Well, I should of had my Tempest Sonosub built by now, but you know how life tends to get in the way sometimes. I'll probably start on it monday and finish it the following week.
    If you want an idea what I'm going to do, Rob, I'm going to use an enclosure of 10.44 ft.^3 (295.6 L) tuned to around 18.8 Hz with a 6" port 16.26 inches long. Dan Wiggins didn't seem to think the smaller port would cause many problems with under 500W sent to it, and I didn't really want an 8" port at 30.85" long for some of the reasons Pat mentioned.
    As for wiring, the dual voice coil arrangement of the Tempest is very flexible. You can just run each channel of a stereo amp to each voice coil to run at 8 ohms, you can run the voice coils in parallel to a single channel for 4 ohms, or you can run the voice coils in series(16ohms)then use a stereo amp that is bridgeable to bring it back down to 8 ohms.
    I have wired my Shiva with a voice coil to each channel of a stereo amp and also in series with a bridgeable amp. I did not notice any difference in performance either way.
    Good luck and let us know how it comes out.
    DJ
     
  11. RobW

    RobW Member

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    David,
    Your design looks good to me on WinISD, but what about driver protection?
    Is 18.8 Hz going to ensure enough protection, and at what amount of power would it be unsafe, if at all? FYI I will be using a QSC amp. With an 8 ohm load it'll pump out 530 watts, as it states, in bridge mono mode. Now, that should be AFTER bridging it, right? So I could wire it in series and get 530 watts?
    Right now, Pat's dual 4" ports look like the best setup on WinISD, but what do you think?
    BTW Pat, it's perfectly alright with me if you guys take over this thread like this because I'm also experimenting with these designs.
     
  12. Greg Monfort

    Greg Monfort Well-Known Member

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    >Actually, my problem is finding a 6" wide port, any ideas where I should look in Atlanta?
    ====
    Since I used to build mostly PA HE subs, I used 6" drain pipe as standard. I haven't bought any in over a year, but I got it at the Sidney Marcus HD down behind Broadview, er, Lindburgh Plaza. Give them a call, as this store carries a much wider variety of stuff than any of the other HDs I've been in.
    ====
    >Are you getting a smaller vent mach number with a different sim program?
    ====
    Yes, I use BoxPlot for quick reference/comparisons. Anyway, think about it, since a single 6" is almost a direct comparison to two 4", doesn't it seem reasonable that they would have ~ the same mach?
    ====
    >(I think I should just start another thread on porting possiblities for Sunosub II, eh?)
    ====
    Sure, why not? At 16hz tuning I didn't normally use T/S tubes anyway, but either large reflex cutouts = Sd, or horn loaded vents, due to the tube's excessive length/volume. Nothing like a pair of JBL or McCauley HE 18"s/15" vents to get some serious HT slam. [​IMG]
    GM
    ------------------
    Loud is beautiful, if it's clean
     
  13. David Judah

    David Judah Well-Known Member

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    I'm not really concerned about driver protection, because I rarely listen to cannon blasts from the 1812 Overture or pipe organ music. [​IMG]
    Seriously though, I haven't had any problems with my Shiva that is tuned to around 20.5, but I haven't run as much power to it either(150W and 240W)as some other folks do, and I don't run it at reference level for normal DVD playback(I'm going to run 400W to the Tempest).
    As far as the ports go, I prefer a single port because I don't want to hassle with the extra work during construction and I don't want to introduce another variable into the design. Some have suggested that the placement of multiple ports can effect output, but I don't know that it has been proven beyond the theoretical realm. ThomasW or Greg would have more offer in that regard.
    Also, as Greg mentioned you would actually get more cross-sectional area from a single 6" port than dual 4's anyways(The dual 4's would equal one 5.65" port).
    DJ
     
  14. TerryC

    TerryC Well-Known Member

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    I built a test mule using the Tempest I have on loan from Dan Wiggins.
    Here is a quick peek of the results.
    [​IMG]
    Used three mic locations for the sweep.
    Seated
    One meter
    Under edge of the sub
    SPL figures are real world using a calibrated LinearX M51 mic
    It's 8.5ft3 tuned to 20hz(size and tuning recommended by Dan Wiggins) using 3 X 4" vents at 26.3" long each.
    Overall it plays louder than the Mass by about 3-5db which is a fair bit and enough not to have any bottoming in my room while watching Lost in Space at reference with the sub +4db. It really did a wonderful job. BTW, My Mass does bottom twice during that opening scene. If you build one you will be happy with it, that I'm sure. Its a killer sub and when you factor in its cost its a steal. Will post a write up soon.
    Regards
    Terry
    PS-you may wonder about the roll off in the bottom end. That is totally normal and has been an ongoing discussion about sims. If you model this sub it says it will be down about 4.9db at 20hz and you would figure with room gain it would be flat to even a little boosted. I have yet to measure a sub where this is true.
     
  15. RobW

    RobW Member

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    WinISD gives me a 0.13 mach for the single 6" (0.07 for dual 4"s). Why? How does the volume, or cross-sectional area, correlate into the port mach? [​IMG]
    The reason I am curious as to the driver protection is, first because Pat talked about it and I remember Dan Wiggins posting about it and the tuning freq., and I will be using a much higher powered amp than you at 530 watts, so I was curious as to what factor that plays; although I may never use THAT MUCH power, I still want to be safe.
     
  16. Patrick Sun

    Patrick Sun Moderator
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    Greg, I'll keep a lookout for drain pipes. Thanks for the suggestion.
    Rob, if you are going to play DVDs that are loaded with sub-20Hz material (Lost In Space, dts Haunting, Titan A.E., etc) at high SPL, the lower tuning will provide a bit of driver protection before the driver will be "unprotected" under 16Hz. But if you are more conservative in your listening levels, like DavidJ, then you can opt for a higher tune (~19Hz) and get a F3 closer to 20Hz. (By tuning to 16Hz, your F3 will slide up to maybe 22Hz). Still, with room gain, it shouldn't be a problem with either design. You just have to consider your design objectives.
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  17. RobW

    RobW Member

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    David,
    Are you positive about bridging the amp cutting the load in half. I just read in another post that the amp doesn't do anything to the load when bridged. I want to have my amp bridged at 8 ohms. Then I will get more power (530 watts), without gaining THD. I want to be sure. The manual states that figure "bridged at 8 ohms". That is how I want to power it. So, wiring it in series would do it? Bridging cuts the load in half? Thanks.
    Rob
     
  18. RobW

    RobW Member

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    I thought that, since the nominal impedance is 4 ohms, if you wire it in series, that would yield 8 ohms, and the amp bridging would not affect this. What am I missing?
    Also, what disadvantages would wiring it in series cause (real world differences, if any)? I understand that in the case of DVCs, they would eliminate EMF, but is there anything else to consider? I don't think so, but I need clarification. Thanks again.
    RW
     
  19. Patrick Sun

    Patrick Sun Moderator
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    Rob, the Tempest voice coils are 8 ohms EACH. To get the nominal 4 ohm load, you have to wire both of the voice coils in parallel.
    It's not recommended to just wire up one of the two voice coil to obtain an 8 ohm load. There are other options that you can read up on in the Tempest white papers on the Adire website.
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  20. David Judah

    David Judah Well-Known Member

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    Rob,
    The formula is (A/B)/2 where:
    A=The impedance of the driver
    B=The number of drivers
    So, (16/1)/2=8 (16ohm because that is what you get when you wire the voice coils in series)
    DJ
     

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