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Disappointed- went from sealed to ported (Tempest)

Discussion in 'Home Theater Projects' started by KyleGS, Jul 13, 2004.

  1. KyleGS

    KyleGS Well-Known Member

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    Hey guys-

    I went from 122L sealed to 200L (19hz) ported with my Tempest. I'm running a PE250 (no boost).
    I heavily braced the new box and used a 6in straight pipe (sched. 40 PVC). I also used about 3 lbs of stuffing.

    I listen to alot of music and maybe this wasn't the best idea. The sub seems a great deal slower. The quality of the bass just isn't there anymore.

    It does play a lot louder from 25hz and down but I really miss the detail and speed of the sealed box. The two set-ups used the same location, same material, same amp, same everything.

    I've eq'ed the sub to knock out any peaks. Even then the sub just sounds slow and bloated in the lower octaves.

    Has anyone had similar results when going ported?

    I'm now considering just keeping the sealed box and running arounnd 520w of clean power via a Yammie M-85 solid state power amp...or... should I try to tweak the ported design?
     
  2. Darren_T

    Darren_T Well-Known Member

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    Hi KyleGS,

    What was your reason for going with the larger vented alignment? I built the Adire alignment Tempest a while back which is their 214L vented sub. 3lbs of polyfil sounds like way too much but it's been a while, I could be wrong. With the larger vented enclosure you'll get better extension etc... but I don't believe it is a preferred alignment for music only. Mine souded great with music though... was plenty quick but may not be as quick as your sealed enclosure.
     
  3. DanWiggins

    DanWiggins Well-Known Member

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    Tune lower. Drop your tuning frequency to 15-16 Hz or so. It will help a lot.

    My guess is you're now hearing "room boom", the result of a "anechoically flat" speaker loaded in a room. Room gain exaggerates the bottom end of a flat speaker, so you end up with bloated and "slow sounding" bass (yes, for the physicists out there, I know it's not slow - this is when used as a subjective description - please see Tolve and Gabrielsson, JAES).

    Tune lower. It will integrate better with the room, and should audibly improve. And you really won't sacrifice any usable output, either.

    Dan Wiggins
    Adire Audio
     
  4. Cam McFarland

    Cam McFarland Well-Known Member

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    How did you come up with the idea to use a 6" dia. pipe.
    My 214l AA Tempest calls for (2) 3" ports. I used no "stuffing", but lined the box with polyfil batting which
    I stapled to the interior walls. I also added an extra set of braces to the inside (2 pair of small braces as opposed
    to just one).

    To my uneducated ear, it sounds great....[​IMG]
     
  5. Patrick Sun

    Patrick Sun Moderator
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    I used a 6" wide PVC port in my Sunosub II (Tempest, roughly 9 ft^3, tuned to 16Hz). [​IMG]
     
  6. dave alan

    dave alan Well-Known Member

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    IMO, this is the perfect example of a comparison of sealed vs ported.

    Same everything (including the room), except for the box type. This is when you can really hear the difference, all computer models, group delay numbers, tuning choices, etc., aside.

    You can't factor the sonic sig of the driver in because it's the same driver.

    I agree with Dan that modeling a ported sub to play anechoically flat to 20 or less Hz causes huge bloat, in-room, at the bottom end of the music bandwidth.

    I also don't care what the physicists say about 'slow' and/or 'fast', or whether or not 20-30 ms is audible.

    Low GD + no EQ = less time smear than high group delay + EQ latency/phase shifts. This means that the sealed sub delivers music bandwidth sound to the ear before the ported, EQ'd sub. That would mean the sealed sub is 'faster'. Some prefer the term 'more on-time', but it's saying the same thing...'faster'.

    The speed of sound, in your room, is the speed of sound. If the musician is playing in your room, all of the direct radiated sound from each note would arrive at your ear at the same time. The low frequencies wouldn't be delayed 1/3 or more of a second.

    To answer the question...yes, I've heard the difference in sound instantly...every time I do the comparisons...all things being equal except for the order and curve of the box. It's the price paid for HT boom.

    The answer is a simple one. Use 1 sub for discrete redirected bass and another sub for discrete LFE. Design and tweak the redirected bass sub for best integration and design and crank the LFE sub for the movie sound tracks.

    Just an opinion that I've had success with, YMMV.
     
  7. BrianAe

    BrianAe Well-Known Member

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    Dave, in one's setup, from a wiring and processor standpoint, how does one accomplish this?
     
  8. KyleGS

    KyleGS Well-Known Member

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    Well I hate to say that I may be stuck with the 19 hz tuning. My port is on the top of the cabinet with the sub on the bottom. If I make the tube longer it will get too close to the motor structure.
    Mr. Wiggins described the sound perfect.
    I'm going to try to move the sub out from the corner and take away some of that room gain.
    I'll get back with ya'll.
     
  9. Cam McFarland

    Cam McFarland Well-Known Member

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    How does this compare to a 200l box....??
     
  10. Cam McFarland

    Cam McFarland Well-Known Member

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    nevermind... 9 cu.ft. is 254l


    just a 6" pipe has twice the volume of 2-3" of same length.
     
  11. dave alan

    dave alan Well-Known Member

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    Dave, in one's setup, from a wiring and processor standpoint, how does one accomplish this?
    _______________________________________

    You need a player with 6 analog outs.

    You need analog bass management, ala the Outlaw ICBM.

    1. Run the player's SW out to the LFE sub.

    2. Run the ICBM's SW out to the redirected bass sub.

    3. Set all speakers 'large' and sub 'yes' in the player.

    (Or, you may be lucky enough to have the Lex MC-12 pre that has seperate L and R RB outs and a seperate LFE out...woo-hoo).

    The LFE sub will get only LFE and the RB sub will get only RB (because there is no LFE input into the ICBM in the first place).

    You'll get the same total output with 2 identical subs as you would with 1 sub that gets the summed signal, but you'll have 5ish dB more headroom in each sub.

    If you decide, during movie playback, to switch to the digital input of the pre/pro or receiver, instead of bypass mode, the RB sub will get the summed signal and the LFE sub will act as an LFE boost sub. This will add 6 dB of SPL gain if you feel the need to bleed.

    You can select any crossover point for integration of the RB and not affect the LFE signal at all. You'll also have seperate control of the LFE volume and, more importantly, you'll know when there is LFE content.

    When switching to CD, the LFE sub will be silent, and when playing MC SACD and DVD-A, you can add as little or as much .1, or even switch the LFE sub off altogether.

    This way, you have the best of both worlds and switching from movies to music requires no tweaking.

    Hope this helps.
     
  12. Pete Mazz

    Pete Mazz Well-Known Member

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    I feel the same way about ported subs, or speakers for that matter. They just don't have that clean sound that I prefer.

    And by the time you tune really low, you lose a lot of the additional output of the port, so why bother.

    Pete
     
  13. Brian Bunge

    Brian Bunge Well-Known Member

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    Kyle,

    Try adding another 1b. of polyfill. Hank Frankenberg build a Tempest is 175L tuned to 17.5Hz and used 64oz. (4 lbs.) of polyfill. This should effectively lower the tuning frequency a bit. I'm not totally sure how much, but probably a couple Hz.

    Also, I built a similar sub for my father using the PE DVC 15". Sounds great to me! [​IMG]
     
  14. Aaron Gilbert

    Aaron Gilbert Well-Known Member

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    I'm with Dan, I bet this is a result of room gain added to a subwoofer that is anechoically flat into the low 20's (-3dB point looks to be right at 20Hz). I have my subwoofer tuned to 11Hz, and aside from extension below 20Hz, I can't tell the vented version apart from the sealed.

    Also, I ran into a situation with my last subwoofer in an apartment, where it sounded absolutely horrible. This was a sealed isobaric subwoofer (push-pull, of course) that had sounded great in larger rooms. F3 was in the low 30's. In the apartment though, room gain contributed to make it sound slow and boomy, at least in a corner. Different placement, such as in the center of the room, might have helped, but that was not an option, unfortunately.

    So certainly don't forget to remember that room dimensions can play a huge part in the overall frequency response and quality of sound. The great thing about DIY is that you can adjust/remove the port to best fit your needs. Try asking the salesman at your local store how much they'd charge to adjust the port in that latest and greatest subwoofer you purchased, to best fit the gain in your room. [​IMG]

    Cheers,

    Aaron Gilbert
     
  15. Patrick Sun

    Patrick Sun Moderator
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    Not true, two 3" wide ports yield roughly the same surface area as a 4.24" wide port, not a 6" wide port.
     
  16. Greg Monfort

    Greg Monfort Well-Known Member

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    KyleGS/BB,

    There's much more damping/lowering of Fb to be gained by stuffing the vent to make it more aperiodic than increasing the cab's stuffing. If there's considerable output around/at Fb, then a screen will be required to keep the stuffing from being pumped out.

    Pete,

    If you don't use speakers, how are you reproducing the LF/sub BW to get a clean sound? WRT low tuned EBS alignments, I consider any acoustic gain as good, so that's why me and many others bother. The more extreme among us build huge basshorn systems to narrow the gap between 'live' and Memorex. [​IMG]

    GM
     
  17. Paul Spencer

    Paul Spencer Well-Known Member

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    Kyle,

    Perhaps you should look at doing some in room measurements. This might help. Then again, if vented doesn't work for you, why persist with it?

    I have two subs and I have compared vented vs sealed and my first reaction was that there was very little difference for music - no major difference in SPL or extension or quality either for that matter. Both were in a 70L box, vented Fb @ 18 Hz. I have also noticed in my simulations that in the range commmonly covered by music, there is barely a JND (just noticeable difference) in extension. +6db @ 25 Hz probably won't help you much for music! Maybe you should revert back to sealed!

    Another route is TL. Then you get the best of both sealed and vented (extension of vented, yet more refined) and some more ... better transient response - I believe a vented box is just about the worst commonly used alignment for transient response, while TL's are far better. For HT this can lead to LFE overexcursion, but for music this shouldn't be a problem. When people talk about subjective "speed" then I wonder if transient response is a part of what they are hearing.
     
  18. Cam McFarland

    Cam McFarland Well-Known Member

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    Patrick...reread my post.....[​IMG]

    I dont say it is equal....I said a 6" port has TWICE the volume of 2 - 3" ports.

    Pretty close to what you are stating, I think....[​IMG]
     
  19. Seth_L

    Seth_L Well-Known Member

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    A large part of your problem is likely that the bass coming from the speaker is not in phase with the rest of your system anymore.

    Set the phase on the amp to 0 (if you have that adjustment). Play a test tone that is 1 octave below your crossover point of your front speakers(40Hz for an 80Hz setting). Increase the distance setting for you sub in your reciever until you get max SPL at your seat (use a meter and your ear). Now your sub will be in phase with your mains. It should sound quite a bit better.
     
  20. DanWiggins

    DanWiggins Well-Known Member

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    Kyle,

    Get an elbow - you can bend the port around, if needed.

    Greg,

    Don't tell them about the screen over the port - let them experience the Cannon of Polyfill at least once! [​IMG]

    Dan Wiggins
    Adire Audio
     

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