What is box imp rise?
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Silver Member Username: Jprix82Post Number: 458 Registered: Jan-06 | What is box imp rise? |
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Gold Member Username: B101Queen City, NC USA Post Number: 2127 Registered: Sep-05 | impedance rise is freq related, but it depends on the enclosure also.. a very large box will have bigger impedance rise... while playing music, impedence rise is almost double of the wired resistance anyway!  |
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Gold Member Username: BlainewPost Number: 1109 Registered: Nov-05 | does that mean that if you have your subs wired to one ohm..thats its really more than that?? |
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Gold Member Username: B101Queen City, NC USA Post Number: 2129 Registered: Sep-05 | exactly |
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Gold Member Username: BlainewPost Number: 1111 Registered: Nov-05 | so ... lets say you get a good amp..like the RE 12.1 (1200 watts @ 1 ohm) and you wire your subs to one ohm, your not REALLY getting that full 1200 watts. so could you get subs and wire them to .5 ohm so that you are more likely to get the 1 ohm rating of 1200 watts?? |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11443 Registered: Dec-03 | when you talk about a sub being 4 ohms, that's a nominal or "average" impedance. The DCR or DC resistance of that usb is actually about 3.6 ohms at rest. A speaker is a reactive load. You're sending current through a coil of wire when producing sound with a speaker, and this generates inductance. As a result, the impedance of the speaker will vary with the frequency of the alternating current going through it's coil (the frequency of the sound you're playing.) The box also has an effect on this change in impedance, and the rise in impedance as you approach the Fs of the driver and enclosure is directly proportional to the efficiency. (weird but that's how it works.. balances out in a sense.) but to answer your question, yes you can load match an amp and sub combination with the enclosure you use and the box's tuning frequency to get the most power from the amp at a certain frequency range for SPL events, and that combination may not be what would sound like an ideal match under normal circumstances. I've seen people run amps at 1 or .3 ohms with big subs (nominal) to get ideal load at their burping frequency because the math worked out that way. The trick is how long you plan to run the system at those loads. |
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Silver Member Username: Jprix82Post Number: 459 Registered: Jan-06 | Is there any way to figure out box impedance rise |
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Silver Member Username: Jprix82Post Number: 461 Registered: Jan-06 | So if i run a 1ohm stable amp at .7ohms will it be ok because of impedence rise or will it damage the amp? |
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Gold Member Username: B101Queen City, NC USA Post Number: 2131 Registered: Sep-05 | yea, what GW said, what you measure at the terminals is only resitance (letter R)(dc related)! ITs part of the formula for impedance (Z) (ac related) When you pass a AC current through a coil, you get capacitance & inductance which changes your impedance when the frequencies changes.. simple formula ex: Z(impedance) = R(resistance) + C(capacitance=cap) + L(inductance=coil) if u run a amp rated @ 1ohm with a .7ohm load, the amp will still be able to handle it, cause its designed to go a ""little"" lower.. Now if you have cheap equipment, u should wire above the rated rms. also like GW said.., its exactly how I try to match my personal systems!! not by rms numbers of subs matching amps, not by "any" box, not at "any" ohm load.. But you have to fully know the operations of each component of your system. |
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Silver Member Username: Graphix1Santa Rosa Heights, Arima Trinidad & T... Post Number: 813 Registered: Oct-05 | wow...i just learned something new...... |
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Gold Member Username: 54danny54Betsy layne, Kentucky..GO... USA duh Post Number: 2114 Registered: Nov-04 | ha ha same here |
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Silver Member Username: Jprix82Post Number: 462 Registered: Jan-06 | So your saying you will never really know what ohms your amp is seeing because of so many freq changes when playing music? |
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Gold Member Username: SouthernrebelMonroe, Louisiana USA Post Number: 2590 Registered: Mar-04 | bingo. box rise will change depending on the sub, box, and freq. but, you can find out what your box rise is at a given freq if you have a multimeter and an amp clamp. just run a freq to your sub and measure current (amps) and voltage the sub is seeing: Imp = Volts / Amps you can also see how much power the sub is actually seeing: Watts = Volts x Amps For instance...the box rise w/ my SX 15 w/ my SPL port in burping at 48hz is ~3.35ohm. |
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Silver Member Username: Dustin3Tigard, Or U.S. Post Number: 677 Registered: Oct-05 | i guess so. ITS A CONFUSING TOPIC: WHATS capacitance? AND inductance? |
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Silver Member Username: Jprix82Post Number: 463 Registered: Jan-06 | Hey marshall i would need a true RMS DMM to check all that right? |
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Gold Member Username: SouthernrebelMonroe, Louisiana USA Post Number: 2593 Registered: Mar-04 | yep...here is the one i use: http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=0 3482014000&subcat=Multi-Meters%2C+Testers+%26+Accessories |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11451 Registered: Dec-03 | www.bcae1.com all of the basics are explained in good detail there. capacitance, inductance, impedance, etc. |
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Gold Member Username: Jonathan_fGA USA Post Number: 5866 Registered: May-04 | This link has a graph of an impedance curve: http://www.lenardaudio.com/education/a05_zspeaker.gif Came from this page, which has a lot of great info about speakers: http://www.lenardaudio.com/education/05_speakers.html |
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Gold Member Username: Jonathan_fGA USA Post Number: 5867 Registered: May-04 | Another note: You can think of the impedance curve as sort of an electrical "mirror" of what's happening mechanically. |
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