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Old 18th March 2006, 06:12 AM   #1
cotdt is offline cotdt  United States
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Default Importance of VC inductance in drivers

I am a newbie, so don't flame me if I'm wrong. So how important is VC inductance in midrange drivers? I found that even in subwoofers, low VC inductance subs sound better than high inductance subs. It sounds "faster" since the cone can accellerate faster, since inductance would be the only factor that influences max acceleration of the driver (F=m*a -> (BL)*i=m*a -> but BL and m is constant so only i matters -> current i is limited by the voice coil inductance). Impulse response graphs seem to agree. Higher frequencies would require even higher cone accelleration so wouldn't the inductance have to be even lower?

Based on what I know, the two things to look for in selecting midrange drivers would be inductance and nonlinear distortion. Linear distortion is correctable using advanced techniques and dispersion is similar amongst drivers of same diameter, so we don't care about those. Anyone disagree with this? OK, linear distortion is not completely correctable since speakers are one electrical signal in -> many signals out, but correction should be good enough I think.

However... cone material also has a huge influence on the sound, and neither inductance nor nonlinear distortion seems to explain this. Even when a soft paper cone and a rigid metal cone both does similarly well on linear and nonlinear distortion tests and have similar inductance, they sound very different. The more rigid cone will sound edgier while untreated paper cones sounds more rounded even if resolution is the same, and in my experience this is general. I would like to know of exceptions, but so far I don't know any. Soft paper seems to sound like soft paper, hard paper sounds like hard paper, poly seems to sound like poly, and metal seems to sound like metal, regardless of common forms of distortion testing. Don't get me wrong, I know even when the same cone material is used different drivers sound different, I'm just saying that the cone material makes a unique contribution to the sound. I am looking for a test that can distinguish these subjective differences, and also to know parameters that can predict these differences in the sound. Once I have my perfect speakers I will use digital correction to build my superspeakers! I have over a million dollars in budget! I need your help to figure out what to look for! Yes I can do my own measurements and stuff! The speakers will be used to play DOOM 3!
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Old 19th March 2006, 12:13 AM   #2
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There is no direct link between VC inductance and performance.
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Old 19th March 2006, 01:41 AM   #3
cotdt is offline cotdt  United States
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Quote:
Originally posted by myhrrhleine
There is no direct link between VC inductance and performance.
care to explain? how would you define performance? i never said there was a "direct link" btw, and there clearly isn't.
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Old 19th March 2006, 02:29 AM   #4
ScottG is offline ScottG  United States
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Quote:
Originally posted by myhrrhleine
There is no direct link between VC inductance and performance.

Sure there is.. "all else equal" low inductance allows a more extended freq. response at higher freq.s. (..and this most certainly is an element of performace.)
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Old 19th March 2006, 03:15 AM   #5
soongsc is offline soongsc  Taiwan
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Isn't inductance variation a more drving factor of performance than absolute inductance value? Less coil weight will definitely allow better high frequency performance.
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Old 19th March 2006, 04:37 AM   #6
lndm is offline lndm  Australia
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Quote:
Originally posted by soongsc
Less coil weight will definitely allow better high frequency performance.
I guess this sounds fair.

With a high voice coil inductance, at high frequencies, the impedance will be high therefore little power would be consumed hence little output. Unless other things come in to play like weight.

Quote:
Isn't inductance variation a more drving factor
Up where the inductance dominates - an inductance varies predictably in proportion with frequency.
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Old 19th March 2006, 04:44 AM   #7
cotdt is offline cotdt  United States
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but even if the inductance varies predictably with response to frequency, it varies unpredictably with displacement. the voice coil is like an iron-core inductor it seems (around the pole), so that would mean that they can easily become saturated and vary with displacement. i'm sure this will cause all sorts of nonlinear distortion like IM distortion. so this way i see inductance not only determine the upper-frequency rolloff but also be a factor in nonlinear distortion performance. i expect high inductance drivers to sound blurry like those cheap poly-cone drivers.
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Old 19th March 2006, 05:09 AM   #8
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by cotdt
but even if the inductance varies predictably with response to frequency, it varies unpredictably with displacement. the voice coil is like an iron-core inductor it seems (around the pole), so that would mean that they can easily become saturated and vary with displacement. i'm sure this will cause all sorts of nonlinear distortion like IM distortion. so this way i see inductance not only determine the upper-frequency rolloff but also be a factor in nonlinear distortion performance. i expect high inductance drivers to sound blurry like those cheap poly-cone drivers.

The amount of coils needed depends on magnetic field strength and diapham mass, air resistance, etc.. If you're just trying to find out how to select drivers, this kind of discussion is really only getting you into deeper mess without really accomplishing what you're looking for. Speakers for playing games really don't require fidelity since the source of the sound has no relation with reality, why would someone want speakers of high fidelity?

If you have a million dollars in budget, why not look for proffessional consulting?
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Old 19th March 2006, 05:29 AM   #9
cotdt is offline cotdt  United States
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all those factors can be modified to acheive lower inductance, even air resistance IMHO, by filling the room with a different kind of gas. or just the driver, i don't know. for gaming great imaging is required, so of course the highest fidelity is required. don't you play games, yeah? total immersion is of utmost importance in gaming, or it will be less like a real dream (nightmare in the case of DOOM).

i'm also thinking the the higher inductance would create a delay for the woofer relative to the tweeter, thereby messing up the imaging. is this true or am i misapplying the equations?

DIYAUDIO is my professional consulting of course, and advice is free. =)
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Old 19th March 2006, 06:05 AM   #10
lndm is offline lndm  Australia
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I read in Speaker Builder that all of the parameters like we're talking about, are engineered in proportions that are one big compromise aimed at a particular end.

That is you can have a speaker that is excellent at one thing at the expense of others, or one that is just good all round. This is how many speakers are. Even the best don't escape the laws of physics.

The clue, so I read, is the sales pitch which will give a clue as to what they are good at/best used for. It is also a clue for the clever as to what they are not good for.
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