Which speaker type puts more stress on the receiver ported or sealed?

Discussion in 'Archived Threads 2001-2004' started by John Pine, Apr 19, 2002.

  1. John Pine

    John Pine Supporting Actor

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    I sealed the port on my JBL L40's and now it appears it's causing my new Yamaha RX-V530 to run slightly warmer. I am running the same content(SRV @ ElMocambo/DVD) at the same volume setting. It's not hot, just slightly warmer. Am I just dreaming or is this possible? I was hoping a guru could give me some feedback. Thanks!
    Below is a previous thread giving more details if needed.
    http://www.hometheaterforum.com/htfo...threadid=63269
     
  2. BrianWoerndle

    BrianWoerndle Supporting Actor

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    It is possible that a sealed speaker puts more strain on the reciever. A sealed speaker needs a stronger magnet to move the cone because as the cone moves the air behind it moves the same as the front. In a ported design, the air moves freely in and out of the port, but in a sealed design it has to play a tug-of-war with the fixed volume of air in the box. Sealed designs tend to be thought of as more accurate because the air moving in and out of the port causes distortion (boomyness). But I feel that if a speaker is well thought out and portrd properly, it can sound just as good. I am not sure if that will cause more strain on the reciever, but it could. I am not an expert, but I would think that if a speaker was ported, it would perform best.
     
  3. Harold_C

    Harold_C Stunt Coordinator

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    A vented enclosure and a sealed enclosure will present somewhat different impedance curves to the amplfier in the bass region.

    However, amplifiers are basically fat, dumb, and happy. Makes no difference to them whatsoever whether they are driving a vented enclosure or a sealed enclosure.

    A sealed enclosure will typically be 3 dB or more less efficient in the bass than a ported enclosure (depends on the tuning), so it is quite likely that you will turn the volume up more to get the same perceived loudness with a sealed enclosure. This, of course, would cause your amp to run slightly warmer as it dissipates the heat from more current. No big deal.

    By the way, air does not flow "in and out" of the port. Instead the mass of the air in the port is like a weight on the end of a spring. The weight moves "up and down" just like the air in the port moves back and forth. Essentially no air actually exchanges from the inside of the cabinet to the outside of the cabinet in a ported enclosure. If you don't believe me, try use the air "moving" in a speaker port to "cool" an amplifier sometime. Doesn't work.
     
  4. Tom Brennan

    Tom Brennan Screenwriter

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    Brian---Actually vented louspeakers generally have more powerfull magnets then sealed ones, this is why a vented speaker can be 3db more efficient than a sealed one for a given volume and F3. It's not that the venting adds 3db efficiency but that the vented design allows the use of a more efficient driver. And more efficiency (for a given moving mass) means a bigger motor--more magnet. I think John has done some weird things to the speaker's f3 (raised it no doubt, perhaps with a big response hump just before the new F3) and impedence (which may have a big spike at F3 now), he should probably unplug the vent and let the speaker work as it's designers (and JBL has some very astute designers) intended. As Harold said John is probably driving the amp harder now to get results he finds pleasing.
     
  5. Harold_C

    Harold_C Stunt Coordinator

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  6. Tom Brennan

    Tom Brennan Screenwriter

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    Harold---Not true? Sealed boxes work best with drivers with a high QTS---small motor. They also work best with massive cones. Both these traits mean lower efficiency. Low QTS--big motored, high efficiency drivers work best in vented boxes. This is easy enough to see if you run some numbers in a box design program. Run an Altec 515 or 416 as a sealed box and see the F3 at around 100hz.
     
  7. kevin_tomb

    kevin_tomb Stunt Coordinator

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  8. kevin_tomb

    kevin_tomb Stunt Coordinator

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  9. John Pine

    John Pine Supporting Actor

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    Good feedback guys! Harold is on to something about having to adjust the volume level to compensate for lack of bass. Before I was content with a -15 setting to achieve "concert level". Now, I have to go up to -12 for similar results due to the fact that it's a large room with a high ceiling. Sadly I do not have a DB meter or the AVIA disc or I would test these myself. I REALLY like the "flatter" sound I'm getting with the port plugged. As I stated earlier the L40's have just been re-coned less than a year ago so I'm hoping they won't be damaged. Is this just wishful thinking?
     
  10. Robert_J

    Robert_J Lead Actor

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  11. Harold_C

    Harold_C Stunt Coordinator

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  12. Tom Brennan

    Tom Brennan Screenwriter

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    Kevin---The venting only effects response near system resonance and isn't effecting efficiency at all above that area. Overall woofer efficiency is determined by the characterisitcs of the driver itself and for a given F3 and box size venting allows the use of a more efficient driver, venting itself doesn't increase the efficiency of a given driver or driver-system. Or for a given efficency and box size venting will give a lower F3 than a sealed box. Or for a given efficiency and F3 venting allows a smaller box. These relationships are fundamental.
     
  13. Tom Brennan

    Tom Brennan Screenwriter

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    Harold---Yet the highest efficiency direct-radiating drivers have 3" and 4" edgewound coils, massive motors and 15" cones. It's a power to weight thing. In any case sealed boxes work best with drivers with weak motors and massive cones and vented works best with bigger motors and lighter cones. Of course not all speakers, such as those at Best Buy, are designed to be "best", there are economic considerations.
     
  14. John Pine

    John Pine Supporting Actor

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    So, how concerned should I be about damaging these newly re-coned speakers?
     
  15. Richard Greene

    Richard Greene Stunt Coordinator

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    Sealed versus ported driver:
    http://deonspace.stryke.com/
    After looking at the chart you'll realize that the statement that ported is 3dB louder in the bass than
    sealed doesn't really describe the effect of a port.
    At one octave above the port tuning frequency there will be little difference. At one actave below the port tuning frequency the sealed driver will be louder.
    Plugging a port will change the impedance seen by the amplifier and could cause it to run slightly warmer --
    I wouldn't expect much difference.
     

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