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Old Today, 01:19 PM   #1341
DBMandrake is offline DBMandrake  Scotland
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Quote:
Originally Posted by mbrennwa View Post
There may be some drivers that are designed like this, but certainly not nearly all cone drivers. It really depends on what a driver is designed for. For instance, a bass driver does not need to have flat response higher than a few hundred Hz.
Maybe a subwoofer driver doesn't care about the response to a few hundred hertz but a normal woofer or mid-bass driver does.

The woofer I gave as an example is a 12" woofer and in the "show effect of voice coil impedance" mode is shown to be 3dB down at 300Hz and 6dB down at 1Khz. The real driver response is nothing like this and is pretty much flat up to 1Khz on axis on an infinite baffle. As the driver may be crossed over realistically as high as about 250-300Hz, that's a large error.

Whether explicitly designed for or not, directivity counterbalancing impedance rise tends to happen naturally as a small driver which starts beaming at a high frequency tends to have a small, low inductance voice coil that doesn't start attenuating until a high frequency, while a larger driver which starts beaming at a lower frequency tends to have a much larger voice coil inductance that starts attenuating at a lower frequency.

In a sense we don't even think about or notice this natural balance occurring until you directly compare two drivers which are the same apart from one having a shorting ring - the one with the abnormally low inductance for it's size then has an upwards slope in its on axis response due to the lack of this natural attenuation through inductance.

So I'd say this is very common in cone drivers.

Quote:
Originally Posted by kimmosto View Post
Now you're talking about actual drivers in practice. Not ideal piston with current driven motor.
Yes, I'm talking about actual drivers in practice - that's what's of interest to me of course.

Although keep in mind that an ideal piston is actually even more directional at high frequencies than real drivers that have cone breakup and decoupling effects whose active area can shrink at high frequencies, whether by design or lucky accident.

So the effect of directivity counteracting voice coil inductance would be even more pronounced on an ideal piston used up to high frequencies.
Quote:
Enclosure tool tries to play both of those, but user is responsible to select which SPL curve is shown and exported. For example I never look SPL curve with impedance effects because it's not very practical approach and useful for purpose of enclosure simulation (which is driver selection and box dimensioning). Basic simulators are not able to simulate HF response so that range is quite useless no matter is there some Z effects or not.
Exactly, so as I suggested earlier I can't see the purpose of that mode or why it's enabled by default. I certainly wouldn't use it.

Incidentally I had a look at WinISD and it also has a mode that tries to include voice coil impedance (although again, why ? The manufacturer already designed the driver for constant voltage operation) however the effect of switching it on is much more subtle than the effect in Vituixcad.

So I'm not sure how they're calculating that...
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Last edited by DBMandrake; Today at 01:32 PM.
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Old Today, 02:32 PM   #1342
kimmosto is offline kimmosto  Finland
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Quote:
Originally Posted by DBMandrake View Post
Incidentally I had a look at WinISD and it also has a mode that tries to include voice coil impedance (...) however the effect of switching it on is much more subtle than the effect in Vituixcad.
'Simulate voice coil inductance' checkbox was added to new WinISD version. It was forced on in earlier versions so you had to zero Le to get flat HF.

You will get equal result by entering equal parameters to both programs. WinISD does not have basic impedance model with Z1k and Z10k so you need to manipulate parameters in Vituix to compare; enter Le and set Z1k and Z10k to zero. That usually gives the worst result with too steep low pass slope at HF though it might look more subtle at LF.
I've never tested more advanced Z parameters (semi-inductance KLe, fLe) with WinISD. Extended Z model is the most accurate for simulating impedance response with Vituix Enclosure.
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