|
Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
|
|
|
Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
|
In Reply to: Well... posted by Charles Hansen on June 22, 2003 at 23:48:40:
Lessee, now...P = E^2/R, so if we plug in 10 mV and 12 ohms, we get (drum roll, please)
8.3 microwatts
It's not an issue of power. It's an issue of voice coil offset.
The greater the DC offset from the amplifier, the greater the voice coil offset in the gap which means that the voice coil will move into the nonlinear region (where the voice coil windings start moving out of the gap) much sooner which means increased distortion.
With your typical 86dB plastic cone woofer with a modest motor system, 5-10 mV doesn't mean a whole lot. But the type of driver Kurt's using, which employs a very light paper cone coupled to a motor system that puts 2.4 Tesla of magnetic flux in the gap and 5-20 mV of DC offset takes on a whole new meaning. This is a single cone (well, single cone plus whizzer) driver and is handling everything from 150Hz on up, so it's not like a woofer that's being cut off at 1-2kHz. Not to mention these things ain't got but a fraction of a millimeter (plus or minus) of linear travel to begin with.
Here's the driver Kurt's using (I presume):
Besides, even with a servo you'll typically get a few mV of offset due to the input offset of the op-amp.
And with a coupling cap, you get none. :)
C'mon now, don't be pissy Steve. It seems like there are certain postings (people?) you just want to jump on, whether or not it's deserved.
Not being pissy at all. Just pointing out that Kurt's situation is not typical. If you think I'm being pissy, just go over to the High Efficiency Speakers Forum and tell 'em that you don't think even 100 mV of DC offset on an AER Mk. II in a front-loaded horn should be any problem.
Then scrape up what bits and pieces of yourself that are left that you can find and come back here and we'll talk about pissy while I stitch you back together. :)
se
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: Well... - Steve Eddy 00:46:01 06/23/03 (2)
- OK, I'll walk you through the math... - Charles Hansen 15:43:32 06/24/03 (0)
- P.S. - Steve Eddy 01:10:48 06/23/03 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
