|
Bottlehead Forum Welcome! Need support, you got it. Or share you ideas and experiences. |
|
|
|
Bottlehead Forum Welcome! Need support, you got it. Or share you ideas and experiences. |
|
In Reply to: Parafeed Cap Sizing Question for P. Joppa posted by Garland on March 27, 2003 at 10:06:07:
The reason I have not said more about this is that I don't know any more. At this point, the best option I know is to model it in Spice or another electrical network program. To do that, you first need to be enough of a speaker designer to model the electrical impedance of your speakers. The alternative is to do it experimentally, either measuring the voltage at the speaker terminals as a function of frequency in the bass and sub-bass, or subjectively, or (preferably) a combination of both.Most of us use reflex boxes because they are more size-efficient, but that means the bass impedance of the speaker has four poles (reactances) in addition to the three in the amplifier (plate choke, cap, and OPT) - so it's a seventh order filter, even if you ignore the power supply cap. Which you can't; often it is a significant player. And don't forget the frequency- and level-dependent inductance of the OPT, which complicates things. (Mikey will say at this point that it's not a problem if the OPT inductance is just plain huge. With a nickel-cre TFA2004, he's right, but with the Paramour's SPECO you can't make that assumption.)
I suppose that if the parafeed components are large enough, then the parafeed interactions happen at low frequencies below where the speaker impedance is fluctuating. In that case, the formulas are OK, since for the most part they assume a fixed resistance load. A speaker with a flat impedance curve would also have less interaction. Where it gets sticky is with smaller plate chokes and parafeed caps; then they will resonate and have interactions with speaker and box resonances. That's why I have suggested trying a 1.5uF cap with the Paramour, but have not recommended it explicitly. The smaller cap moves the resonance up a bit, presenting more liklihood of speaker interactions, good or bad.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Tough one.. - Paul Joppa 13:12:17 03/27/03 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
