|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
|
|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
In Reply to: RE: Correct.... posted by Coner on May 26, 2015 at 10:44:41:
"As I understand it, loading caps have been used to help control diaphragm excursions with high power inputs at lower frequencies. A diaphragm's suspension, especially if made from aluminum, can work harden then fail after many large excursions. The loading cap presents an acoustic load to the diaphragm that helps to limit these excursions and extend diaphragm life.To the best of my knowledge, the loading cap first appeared in 1945 in the high frequency section of the 604 Duplex, really an Altec 802. I'm not sure whether the standalone 802 driver of the time used the loading cap. This was the first appearance of the tangential compliance in Altec drivers, and it allowed for greater low frequency excursions. It is probably not coincidental that the loading cap appeared at the same time. Since then, Altec most often fitted the loading cap to drivers intended for high level use, and omitted it and substituted the felt in the rear cover in drivers intended for consumer use. The felt pad in the rear cover dates back to the original small format driver, the Lansing 801 field coil driver of 1937, and is present in most of these early drivers.
When using any of these drivers for typical hi fi use with adequate protection from the crossover, I feel that the loading cap is unnecessary and that the drivers sound better without it. I have also found that the drivers sound better still, with greater clarity and less confusion in the sound, with the back cover removed entirely. This is a subjective thing, and somewhat controversial, and measurements won't show any difference with the cover on or off. This can only be done when the driver is not located in a bass cabinet, and is in a situation where kids or cats won't have access to the naked diaphragm!
Some people think [that would have been me] that the volume of air trapped by the back cover is a designed part of the driver, like the sealed rear chamber used for reactance annulling in a bass horn. I don't think this is the case in most drivers though. Early examples of the Western Electric 555W vented the rear of the diaphragm through a mesh screen, and Wente's patent on the original compression driver with circumferential phasing plug, as used in the Fletcher System, indicated screened vents in the rear cover. Lansing's first compression drivers for the Shearer Horn System were based on Wente's experimental driver, and his rear covers had a series of vent holes around the perimeter. My guess is that the pioneers eventually found that sealing the rear covers eliminated a source of contamination to the driver and made no difference in the response curves. Still, I have found many times that removing the cover eliminates a subtle layer of sonic hash from the driver's sound. YMMV of course. "
Steve Schell
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/26/15
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- I guess I stand corrected - Tre' 14:12:32 05/26/15 (2)
- Thanks - nice detective work! - inguz 16:17:56 05/26/15 (1)
- RE: Thanks - nice detective work! - Triode_Kingdom 21:52:51 05/26/15 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
