varietyguy Posted January 7, 2012 Report Share Posted January 7, 2012 I understand what it is but can someone explain how? Quote 1992 Mazda 323 http://www.stevemead...323-wall-build/ Link to comment Share on other sites More sharing options...
Azagtoth502 Posted January 7, 2012 Report Share Posted January 7, 2012 When the cone starts moving, the magnetic field with the magnet and the moving coil increases the resistance of the voice coil. Quote pa-pa-platypus sorry not everybody has a companies nuts so far down their throat they catch every drop ball sweat when it falls Link to comment Share on other sites More sharing options...
varietyguy Posted January 7, 2012 Author Report Share Posted January 7, 2012 When the cone starts moving, the magnetic field with the magnet and the moving coil increases the resistance of the voice coil. So in theory the bigger the magnet the bigger the rise? Quote 1992 Mazda 323 http://www.stevemead...323-wall-build/ Link to comment Share on other sites More sharing options...
Guest Posted January 7, 2012 Report Share Posted January 7, 2012 also, the more your woofers heat up, the higher the resistance. Quote Link to comment Share on other sites More sharing options...
bkolfo4 Posted January 7, 2012 Report Share Posted January 7, 2012 (edited) No on the bigger magnet comment. A subwoofer is a magnetic coil with an inductance. When you input AC current, the resistance (actually called impedance) varies depending on the frequecncy of the AC signal. A woofer has its own impedance rise at the Fs of the woofer. A 4 ohm woofer is WAY above 4 ohms at Fs. Many people do not realize this and understand that the impendance they are calling "impedance rise" is actually there with the woofer out of the box. But that being said, putting the woofer in a box also creates additional impedance spikes due to the box resonance and the port tuning. Impedance of a subwoofer is based on an average as long as it is a certain percentage over the minimum impedance (a google search can explain how driver nominal impedance is calculated), but it is not a flat X ohms, and like I said, it rises well above the nominal rated impedance at Fs. Impedance rise without a box Edited January 7, 2012 by bkolfo4 Quote Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
2007TBSS Posted January 7, 2012 Report Share Posted January 7, 2012 How do you measure the min/max rise and does it matter? You meter it while it plays? Quote JVC AVX840 Xtant 604x Xtant 403a 2 RE SEX12's Polk Audio DB6501 Front and back http://www.stevemeadedesigns.com/board/topic/127503-re-12s-box-build-system-complete/page__p__1794327__fromsearch__1#entry1794327 Link to comment Share on other sites More sharing options...
bkolfo4 Posted January 7, 2012 Report Share Posted January 7, 2012 Does not matter for daily. Competitors can use the impedance info at the frequency they are competing with so they can maximize the power on the subs. Quote Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
bkolfo4 Posted January 7, 2012 Report Share Posted January 7, 2012 (edited) Edit - double post Edited January 7, 2012 by bkolfo4 Quote Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
bkolfo4 Posted January 7, 2012 Report Share Posted January 7, 2012 Only way to know your impedance is to measure it at each frequency and plot the results. There are several ways to measure it. If you have a DMM and clamp, use ohms law. If you only have a DMM, you can add a series non-inductive resistor and look at voltage at the amp vs. the voltage across the known resistor. The difference is the voltage dropped across the sub. Current can be calculated by the voltage across the resistor / value of the resistor. Once you know the current and the voltage across the sub, you can calculate the impedance at that frequency. Quote Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
varietyguy Posted January 8, 2012 Author Report Share Posted January 8, 2012 excellent info thank you. Quote 1992 Mazda 323 http://www.stevemead...323-wall-build/ Link to comment Share on other sites More sharing options...
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