Coytee Posted December 15, 2008 Share Posted December 15, 2008 Not of a speaker as I presume the speaker rating is contingent to the drivers to a degree. In a driver, you have a magnet, some wire loops for the voice coil, basket all connected to a spider and cone... If you have two otherwise identical drivers, what is the ingredient that makes one an 8 ohm driver and the other 16 ohms? Quote Link to comment Share on other sites More sharing options...
Groomlakearea51 Posted December 15, 2008 Share Posted December 15, 2008 Number of "turns", total length, and diameter of the coil wires? Quote Link to comment Share on other sites More sharing options...
TNRabbit Posted December 15, 2008 Share Posted December 15, 2008 For sure the first two, but I didn't know the diameter/gauge of the wire made any difference....hmmmm..... Quote Link to comment Share on other sites More sharing options...
twistedcrankcammer Posted December 15, 2008 Share Posted December 15, 2008 Number of "turns", total length, and diameter of the coil wires? TNRabit, Marshall is correct. Increasing the length of the wire, increases resistance or voltage drop / ohmage / Impedance. Increasing coil diameter decreases resistance / voltage drop / ohmage / Impedance. Also, increasing the resistance to the movement of the speaker cone also increases the Impedance / ohmage of the speakers, such as a stiffer surround. The Woofer in the Klipschorn is rated at 4 Ohms resistance, but the crossover sees 16 Ohms resistance do to the choke down of the throat at the motor board. This is not my immagination, but is documented by PWK in his Dope from Hope. Roger Quote Link to comment Share on other sites More sharing options...
fenderbender Posted December 15, 2008 Share Posted December 15, 2008 It really depends on the number of Mantra's your Hindi cab man is chanting..... waahoo...I'm on fire today....... Quote Link to comment Share on other sites More sharing options...
WMcD Posted December 15, 2008 Share Posted December 15, 2008 I agree with Twisted. The spec we see is the D.C. resistance of the wire in the voice coil. Let me point out that this is very similar to what we know about speaker feed wire. The the thicker the wire, the lower the resistance per foot; the more feet we have, the more the overall resistance. Wm McD Quote Link to comment Share on other sites More sharing options...
Deang Posted December 15, 2008 Share Posted December 15, 2008 Hmmm, I thought it was a coin toss. Quote Link to comment Share on other sites More sharing options...
Groomlakearea51 Posted December 15, 2008 Share Posted December 15, 2008 It really depends on the number of Mantra's your Hindi cab man is chanting..... Now that's oblique humor!!![Y] Quote Link to comment Share on other sites More sharing options...
fenderbender Posted December 15, 2008 Share Posted December 15, 2008 What did one stomach muscle say to the other stomach muscle?.......I'd love a six pack.... Now thats Oblique Humor......... OK I got to get the meds balanced out....this is getting ridiculous! Quote Link to comment Share on other sites More sharing options...
Coytee Posted December 16, 2008 Author Share Posted December 16, 2008 Marshall is correct. Increasing the length of the wire, increases resistance or voltage drop / ohmage / Impedance. Ok, so if I recall correctly, if I were to buy replacement diaphragms for the pair of JBL 2404's that I no longer have, I had a choice of 8 ohm or 16 ohm. Your comment means the version with 16 ohms had a longer wind of wire loops around the voice coil? Would the wire be the same thickness as the 8 ohm and simply a different length? (would that matter?) Given a driver with higher ohm rating would then do what? Make it more 'reactive' to a signal coming in or less 'reactive'? (I'm thinking would it have more or less sensativity, strictly on ohm rating?) Quote Link to comment Share on other sites More sharing options...
TNRabbit Posted December 16, 2008 Share Posted December 16, 2008 The higher the impedance/resistance/ohms, the less available power your amp will output into it. However, the amplifier is better able to control the cone/dampen unwanted mechanical resonance at higher ohms. This is generally most true in the lower frequencies. Hence, lower resistance speaker systems sometimes exhibit "loose" bass. This is dependent also on the damping factor of the amplifier being used as well. Tube amps GENERALLY have lower damping factors, but that's not an absolute. Quote Link to comment Share on other sites More sharing options...
twistedcrankcammer Posted December 16, 2008 Share Posted December 16, 2008 Marshall is correct. Increasing the length of the wire, increases resistance or voltage drop / ohmage / Impedance. Ok, so if I recall correctly, if I were to buy replacement diaphragms for the pair of JBL 2404's that I no longer have, I had a choice of 8 ohm or 16 ohm. Your comment means the version with 16 ohms had a longer wind of wire loops around the voice coil? Would the wire be the same thickness as the 8 ohm and simply a different length? (would that matter?) Richard, Without knowing the specific two drivers in question, I can't definitively answer this question. Most probably, the 16 Ohm driver would have to have a loger wire, but Electro Voice made two versions of 4 Ohm EV 15W-K that had two diferent voice coil diameters, one was a 2 inch coil, and the more common one has a 2.5 inch coil diameter, hence the 2.5 inch would have less coils unless the wire was also a larger diameter, but alot more comes into play with your next question. Given a driver with higher ohm rating would then do what? Make it more 'reactive' to a signal coming in or less 'reactive'? (I'm thinking would it have more or less sensativity, strictly on ohm rating?) Higher Ohmage of the voice coil would increase the voltage drop across your voice coil and decrease the available wattage your amplifier has to drive the speakerSensitivity is a much more complicated issue then just the Ohms a speaker is rated at. Change your thinking arround, for all intents and purposes, a speakers driver IS an ELECTRIC MOTOR!! Increased sensitivity is the same as building a more efficient motor. We can build a more efficient motor by putting better bearings in and thus reducing friction to it's rotational movement. We can do this with a speaker by reducing the resistance to the movement of the cone surround and stiffness of the spider assembly, but there is a trade off in that the weaker surround will not pull the cone back to center as well, and the weaker spider assembly will not keep the coil as straight inside the magnet structure. We can increase the efficiency of a motor by decreasing the mass of the rotational assembly. We do this in a driver by building alighter cone, dust cap, and weight of the voice coil former, but this has it's limits in what we must balance out in strength of the assembly also. We can increase the efficiency of an electric motor by increase the magnet strength. With a speaker, we can do this by increasing the size of the magnet, changing to a similar sized magnet that is stronger such as Alnico, or even better yet, Neodymium Magnets, but you get into increased production cost here, as well as the need for a stronger stiffer frame for heavier magnets, and it also becomes a cost vs: diminishing returns thing. Magnetic fields drop off verry quickly. You can evidence this by two powerful magnets that you have to slide to sepparate, or a magnetic door lock that you cannot pull apart, yet at an inch apart, you could easily keep that door from closing or the two magnets from snapping together, therefore we can make a more efficient motor, or a more sensitive speaker by decreasing the air gap between the magnet structure and the voice coil, but then we need stiffer surrounds ans spider assembly to keep the coil from rubbing the magnet, or the former from rubbing the magnet structure inside. We can decrease the thickness of the voice coil former, and thus reduce distance between the inside of the coil and the manet structure on that side, but again, materials, strength, and cost play a roll. We can increase the surface proximity of the electro magnetic field of the voice coil by using flat coils of wire instead of round wire, thus increasing sesitivity. Richard, I hope this helps you understand it better.... Roger Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted December 16, 2008 Share Posted December 16, 2008 the density of the flux capacitor? Quote Link to comment Share on other sites More sharing options...
Deang Posted December 16, 2008 Share Posted December 16, 2008 LMAO! I'm still going with the coin toss. Quote Link to comment Share on other sites More sharing options...
Deang Posted December 16, 2008 Share Posted December 16, 2008 I'm surprised no one has stated the obvious yet -- resistance (DCR) and impedance aren't the same thing. Impedance of course changes with frequency, and maybe what Coytee is really asking is what determines the impedance rating of a driver. Once you understand how it works, you'll see why I'm staying with the coin toss. Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted December 17, 2008 Share Posted December 17, 2008 what would Jackson Bart do? huh? Dean, explain to the good folks why measuring the 'impedance' of a static driver with a simple meter is not an accurate gauge of it's 'nominal impedance' in real life scenarios. Quote Link to comment Share on other sites More sharing options...
Deang Posted December 17, 2008 Share Posted December 17, 2008 O.K., when you grab a multimeter and measure across the terminals, all you're doing is measuring the DC resistance of the voice coil. A VC is basically an inductor, but also has a resistive component. At any rate, the measured result is derived simply from the combination of width and length of the wire. This resistance measurement is static -- but impedance is dynamic. Measuring impedance isn't nearly as straightforward as a DCR measurement, and what we find out is that impedance varies quite a bit compared to the DCR measurement. We are given a "nominal" impedance rating, which isn't usually that indicative of what's going on. http://www.epanorama.net/documents/audio/speaker_impedance.html http://www.transcendentsound.com/amplifier_output_impedance.htm The guy for this conversation is John Warren. Quote Link to comment Share on other sites More sharing options...
Coytee Posted December 17, 2008 Author Share Posted December 17, 2008 O.K., when you grab a multimeter and measure across the terminals, all you're doing is measuring the DC resistance of the voice coil. A VC is basically an inductor, but also has a resistive component. At any rate, the measured result is derived simply from the combination of width and length of the wire. This resistance measurement is static -- but impedance is dynamic. Measuring impedance isn't nearly as straightforward as a DCR measurement, and what we find out is that impedance varies quite a bit compared to the DCR measurement. We are given a "nominal" impedance rating, which isn't usually that indicative of what's going on. I didn't know I was asking such an intelligent question! Quote Link to comment Share on other sites More sharing options...
Don Richard Posted December 17, 2008 Share Posted December 17, 2008 When an electric current is put through a movable coil situated near a fixed magnet, motion results. When a moving coil passes through a fixed magnetic field, electric current is generated. In a loudspeaker this is known as "back EMF", the amount of which increases whenever the cone motion increases, such as when the resonant frequency of the driver is reached. It is called back EMF because the voltage that is generated is opposite in polarity to the driving voltage, thus opposing it, causing a reduced electric current to flow through the driver. This results in an impedance increase at that frequency, and other impedance variations throughout that driver's frequency range. DC resistance is static, unless you push the cone in and out. Then you would see a changing reading on the ohmmeter. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted December 17, 2008 Share Posted December 17, 2008 And for frequencies higher than resonance, the inductance of the voice coil causes an impedance which rises with frequency. Quote Link to comment Share on other sites More sharing options...
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