subwoofer design problem

[f4ier]

Which is why such equalizers with inductors would cost a mint Why not use gyrators?

Protel does require a big chunk of HDD space. But PSPICE and Circuit Maker are both well worth the required HDD real estate. Electronic Workbench is a baby compared to the other two -- always complaining about transient and convergence problems.

Thanks for the link! I might check it out now

Isaac

[ThomasW]

gum

The Krell, M&K, etc, aren't isobaric configurations. And the drivers aren't wired push-pull. If they were push-pull they would cancel each other out since they share the same space.

The primary benefit to a true isobarioc config is the reduction in cabinet size do to the decrease in Vas.

Making a true isobaric config with 1503's would be difficult. They can't simply be bolted together in a 'clamshell' manner because the surrounds are to large. An adapter ring would be necessary to avoid having the surrounds rub together.

[BAM]

If you absolutely must fit a woofer box into a really small space, like a car, and must have lots of power handling, then Isobaric might be a nice way to do it. But for large, open listening rooms, or even the occasional bedroom sub, I would not waste my money on more than 1 woofer per hole. I already tried that, and there was no real advantage to having push-pull woofers. It was easier to bottom them out. I would not recommend using isobaric woofers in anything but a sealed box to prevent the woofers from bottoming out so easily.

I'm not lucky enough to have a separate listening room. My listening room/home theater/office is in my bedroom. When I go away to college, that will be my dorm room. My BPD1001 subwoofer will only be 12 inches wide, so it can fit up against the side of my desk or between my bed and the wall, without needing to be an isobaric configuration.

[pkgum]

What actions do subwoofer makers take to reduce distortion?

[ThomasW]

Having a 2 driver cabinet with one woofer facing in and one facing out will result in the cancellation of the harmonics. But understand this isn't 'push-pull', nor is it isobaric

Also the current generation of woofers/subwoofers generate very little even order harmonics, so this type of mounting really isn't necessary.

[pkgum]

is it possible to buy an accelerator servo thingy (the one they use in velodyne) and install it in the woofer. Are there any threads or web pages that show you how to do this?

[f4ier]

It's probably an easy circuit to implement, though I haven't thought about it much simply because there's a better solution -- build better subs with *quality* drivers... more of these would be better of course

I'd set aside such critical thinking for now and proceed with building your BP (or Tempest?) subwoofer then compare it with a Velodyne. It is highly unlikely that you'll feel the need for a current limiter after the comparison.

Isaac

[BAM]

Why would you want to put a current limiter on a subwoofer with as much raw horsepower as the BPD xx03 series? The velodyne uses paper drivers that probably cost them $40 apiece, so they need current limiters to keep their amps from melting the voice coils right off their formers.

[GRollins]

The two common ways to approach servo loops are to use:
1) A piezo element
2) An accelerometer
The piezos have ferocious phase shift, so you'll need to compensate for that, but after that it's pretty straight forward.
The accelerometer chips are available here and there (Digikey has them), but they're damned expensive--about $15-20 per chip. (Compared to piezos for less than a dollar.)
In either case, generally you mount them under the dust cap/center dome.
Phenomenal results can be had from a servo system. Bad drivers sound good. Good drivers sound better. High quality drivers sound magnificent. I've heard several servo (not to be confused with 'feed forward' systems) systems over the years and they all tend to leave you shaking your head, not knowing that subs could possibly sound that deep, fast, and tight.
I've got an optical method that I'm going to try once I can shake free a few hours. I will eventually report on this if I can just get a few more things off my to-do list, as it's a high priority item for me.

Grey

[pkgum]

I think theres a misunderstanding. The accelerator thingy is not a so-called 'current limiter'. Its a chip that measures the motion of the speaker cone several thousand times a second. The data is then carried into a processor where it is compared to the original input signal. Any distortion in movement of the cone is corrected -therefore making it sound just better.


The problem is It doesn't sound possible for a ordinary home user