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Need to go to subwoofer school...

Discussion in 'Speakers & Subwoofers' started by Strong Lead, Nov 3, 2015.

  1. Strong Lead

    Strong Lead Auditioning

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    Glenn
    Having listened to music for most of my life, I have a pretty good understanding of how speakers sound (or fail to sound, or hurt my ears when they fail to sound, or...).


    All I know about subwoofers is what I feel about them, so to speak, and I know what they need to do. Subwoofers have "A" requirements that often conflict:
    • Accuracy: When listening to the Grateful Dead jam, I want to hear the individual notes Phil Lesh plays on the bass, and I want to hear the low percussive beats. Accuracy comes down to precisely the sub moves moderate volumes of air.
    • Amplitude: I don't care which notes special effects hit. I want to feel the impact of the effects rumble through the room and my chest. In rock 'n roll terms, "Shake it baby, shake it!" Amplitude comes down to how quickly the sub can move large volumes of air. Unlike music, however, HT must sustain those movements of air.
    I totally get lost understanding how various manufacturers achieve those results. (Why do some 8" woofers outperform 18" woofers?) More importantly, I do not know what to look for in specs and reviews that indicate how well they perform the various functions. Within any given manufacturer I do not know which product lines (and which models within the lines) match up to various speaker lines. Yeah, I know woofers don't match like fronts and centers, but I assume general capabilities will correspond.


    Being a cheap basid, I'm looking to maximize bang for the buck by purchasing used or "vintage" product that matches my needs.


    Can some one point me to a few links that explain:
    1. the basics of how subwoofers work
    2. the different approaches taken to achieve results
    3. the trade-offs involved in various subwoofer designs
    4. how to read and understand the specs
    5. how to match subwoofer specs/reviews to speaker reviews
    I may have graduated 20 years ago, but I still cannot get away from the mindset that needs to understand "how" and "why" so I can apply governing principles to my own situation.
     
  2. John Garcia

    John Garcia Executive Producer

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    For musical quality, one typically wants a sealed subwoofer. Due to the nature of their design (air inside the cabinet is sealed from the outside air), the tend to have a "cleaner" more musical sound. While many still reach deep down, the "rumble" associated with movies is often not as good in the lowest octave. This would be one of the biggest the trade offs. The other trade off being that sealed subs also typically have lower output compared to a vented design. I gladly take that trade off for musical capability. A vented sub uses one or more vents (aka not sealed, air may move in and out of the cabinet) to tune the cabinet to a specific frequency and allows the sub to be louder around that tuning frequency. If that tuning is low, the sub can essentially be made to sound louder in the desired range. The trade off with a vented design is often giving up some accuracy for that output and extension down low. There are of course designs that can be good in both regards, as well as a few designs that basically allow you to switch between the two types by plugging the vent. Having owned many subs over the years, I've come to stick with sealed because I prefer it for music.


    Forget speaker reviews :) They can tell you what the listener hears, but everyone hears differently and has their own preferences. What I can say about a good speaker to someone else is: it is worth listening to. When it comes to numbers for subs, IMO, you're looking for good 20Hz performance and a relatively flat curve in-room.


    VIntage doesn't always work with subs, but good used subs can still be a good value for what they are. The question with subs quickly becomes how much and then how large is the space it will need to fill?
     
  3. Robert_J

    Robert_J Lead Actor

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    1. A subwoofer works like any driver. Electrical current passes through a coil of wire inside a magnetic field. That coil is either attracted or repelled to said magnetic field. The cone moves back and forth based on the alternating current of the signal. Rate of movement depends on signal strength, frequency and how the driver was designed.

    2. John did a great job explaining it. I only disagree with one part - a ported sub can sound just as good as a sealed sub if designed correctly.

    3. Hoffman's Iron Law - What they don't explain is that large subs are expensive to ship and also have a very low WAF (Wife Approval Factor). That's why there are so many poor sub designs on the retail market. Internet direct is better about building larger subs. DIY will allow you to build a sub and it can double as a coffin when you are done listening.

    4. Driver specs or just the frequency response specs of a sub?

    5. You don't. You match the sub specs to your room and goals. A sub that meets your expectations in your room may sound weak in mine.


    John mentioned that vintage doesn't work with subs. True. High excursion subs took off in the mid to late 90's and it was lead by members of this forum. My subs from 1990 have an xmax of 8mm. My current subs have an xmax of 30mm. Since both are 15" drivers, that means my current subs can move over 3.5 times the air. That translates into lower frequencies at higher volumes. And 30mm isn't the limit. There are retail drivers with 40+mm of excursion and even one rare one that is close to 100mm.
     
  4. John Garcia

    John Garcia Executive Producer

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    Yes, vented subs have definitely come a long way, a lot of which owes to much better drivers, cabinet design methodology and construction techniques as well as better vent designs. For the sake of the explanation, I generalized for the OP. There are always exceptions in both categories - I've heard poor sounding sealed subs and I've owned musical vented subs.
     
  5. inzer585

    inzer585 Auditioning

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    Your room plays a huge part in the "accuracy" of those notes. The sound waves bounce around your room, making them less detailed and muddy sounding. Proper placement and room treatments like floor to ceiling corner treatments at least in the front corners and thick panels on the back wall.


    You need output to get the slam in your chest from drum kicks. Lots of output in the 50-100hrz range. Seems to me a few tapped horns or BFM HT Tuba is what your after.
     
  6. Grady Hollums

    Grady Hollums Second Unit

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    I have been away from the forums for a very long time, but I'm getting bit by the HT bug again. I'm looking for the threads that discussed building your own subs. I think I might like to get into that world a little bit and start looking at a sub that would compliment my older passive SVS cylinder sub. Any website suggestions or maybe a link to the thread of building your own subs? Thanks everyone! Blessings.
     
  7. Mike Frezon

    Mike Frezon Moderator
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    Hey, Grady!


    Welcome home! :welcome:


    Here's a link to a page of search results on DIY Subwoofers. Maybe you'll find what you're looking for in one of those threads.


    Your question also jogged my memory of some great DIY threads featuring Patrick Sun's DIY sonotube projects.
     
    Grady Hollums likes this.
  8. Race Bannon

    Race Bannon Supporting Actor

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    What do you guys think about getting a pair of SVS subwoofers, one sealed and one ported? (Large room, home theater).


    Might this give you the benefits of twin subs, while at the same time "smoothing out" the different strengths and weaknesses of ported and sealed?
     
  9. schan1269

    schan1269 HTF Expert
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    No. Cause you can do the same thing with DSP.
     
  10. vidiot33

    vidiot33 Stunt Coordinator

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    I would consider a servo sub, as well as sealed, if music is the priority. Rythmik makes sealed servo subs which are very highly regarded.
     

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