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Old 19th April 2011, 01:21 PM   #971
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Just got a call from eminence (i called last night and left a message) they will be getting more 3015LF drivers in stock on 4/25!!
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Old 19th April 2011, 03:29 PM   #972
epa is offline epa  Netherlands
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Quote:
Originally Posted by CRESCENDO View Post
I'm very new to inductors - was just playing w/#'s. 4 cabs without it models pretty flat, however. I provided the HR inputs so you folks could look at all the screens without me flooding my post w/pics. I can sure post them all next time if preferred. As far as delay and transient issues are concerned, I still consider myself new at this and am not entirely sure what to look for. Feel free to point out the problems with that driver in the SS15 enclosure. It looks good from a far, but may be far from good..? Maybe I have my beer goggles on.

In addition, this idea was based on the idea that many have already built SS15's, so the extra wood thing was negated.
hi justin
we discussed the inducter isue in the other topic.
jason pointed out to me that as we introduce an inductor ,we also introduce resistance,wich in turn re-introduce peaks .
so your probably better of not using them at all.
also mh vallues are often given @ 1kz.
as frequenty decreases ,induction increases.in fact it usually doubles or more @ 30>100 hz hz
i discused this with david mcbean.
in pa we can safely take the le vallue @1khz and double it for use in a sub model
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Old 19th April 2011, 05:30 PM   #973
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by epa View Post
in pa we can safely take the le vallue @1khz and double it for use in a sub model
Who is we? Cause I haven't seen any 'doubling' method in any PA sub I came across. Of course I haven't seen them all but I would like to know.

But I think what you meant is that a driver with an inductor in serie raises its impedance as frequency increases. Also a sub with relative low frequency Fs can influence the crossover. You can correct this by a LCR network. But in this case of just an inductor in serie with the driver you don't need to correct this. The added resistance of a high power inductor is relative small (< 0,4Ohm) cause otherwise it would act more as a heater instead of passing the power. But still the inductor can heat up significant under stress conditions (power loss) and that's why inductors are no longer favoured in times of active filtering/powering.

There are a few things you need to consider with inductors for high power PA subs;
1.) What is the saturation point of the inductor (saturation results in distortion)
2.) Power loss.
3.) That a high magnetic field of the loudspeaker can influence the inductor
4.) It can change the impuls/excursion behaviour significant.

The last one is very important for high power loads. All LF PA drivers have an optimized cone damping to smooth out the response at high power loads (often optimised at max continues power). When an inductor is used in series the cone damping/impulse behaviour is influenced and often results in higher excursion. Although this increases SPL also it is VERY important to measure this. At high power it can make the difference between killing a LF driver or not! One of the positive side effects is the pleasing 'punchy/impulsive' sound. Often this is the main reason why inductors are used in high power subs.

Last edited by Djim; 19th April 2011 at 05:55 PM.
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Old 19th April 2011, 06:09 PM   #974
epa is offline epa  Netherlands
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here is an example of a mh curve of a beyma (i think 18")driver.
few manufactures show this info.
they usually only show 1kh and 10 khz values
as you can see below 100 hz induction is ~ double the 1 khz value.

Click the image to open in full size.


here is an other post with ts of a selelenium with le @ 10 khz ,1 khz and fs
i discused it with david mcbean here in the hornresponce topic
but maybe i am incorrect.

Last edited by epa; 19th April 2011 at 06:21 PM.
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Old 19th April 2011, 06:50 PM   #975
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by epa View Post
here is an example of a mh curve of a beyma (i think 18")driver. few manufactures show this info. they usually only show 1kh and 10 khz values as you can see below 100 hz induction is ~ double the 1 khz value.
here is an other post with ts of a selelenium with le @ 10 khz ,1 khz and fs
i discused it with david mcbean here in the hornresponce topic
but maybe i am incorrect.
No, you are not incorrect but you are talking about voice coils and not external inductors that was suggested. Voice coils have relative high resistance, are moving in a magnet field and are coupled to a changing physical resistance (cone). External inductors are not moving in a magnetic field, have the lowest resistance possible and therefore should have stable variables. If they didn't we couldn't use them in crossovers, would we?!

Last edited by Djim; 19th April 2011 at 06:53 PM.
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Old 19th April 2011, 07:19 PM   #976
epa is offline epa  Netherlands
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in the 1st part of the reponce i was talking about a series coil.
1.8 mm 3 mh coil has a resistance of 0.4 ohm
if you add 0.4 to the rg in hr,you reintoduce peaks(wich you want remove)
even 0.2 ohm wil do that.
that was discussed in another topic.
but i think we can agree that a coil in pa use should be avoided,or kept to a minimum for varius reasons.
2nd part of the responce to justin was the voice coil inductance and how one could double the 1 khz vallue for the sub region.
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Old 19th April 2011, 08:03 PM   #977
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by epa View Post
in the 1st part of the reponce i was talking about a series coil.1.8 mm 3 mh coil has a resistance of 0.4 ohm if you add 0.4 to the rg in hr,you reintoduce peaks(wich you want remove) even 0.2 ohm wil do that. that was discussed in another topic.
Show me please cause I'm a little sceptic that it can have that kind of impact within the bandpass of TH subs.

Quote:
Originally Posted by epa View Post
but i think we can agree that a coil in pa use should be avoided,or kept to a minimum for varius reasons.
Yes and no, I totally agree with avoiding such afterwards correction as much as possible. On the other hand it wouldn't be the first time a 6th order bandpass or TH (similar behaviour) could benefit from an inductor.

Quote:
Originally Posted by epa View Post
2nd part of the responce to justin was the voice coil inductance and how one could double the 1 khz vallue for the sub region.
Actually, that statement is even arguable cause those graphs you refer too don't show the non-linearities of the inductance of a voice coil under different power loadings (think of temp and resistance rise, changing magnetic field by excursion )

Last edited by Djim; 19th April 2011 at 08:05 PM.
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Old 20th April 2011, 01:50 AM   #978
NEO Dan is offline NEO Dan  United States
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Well the 3015LF is back in stock.
And I really must say I feel for you guys, @~1000 posts of collaborative refinement and you get the rug yanked out from under the value proposition.
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Old 20th April 2011, 02:23 AM   #979
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Considerably cheaper here...but it still hurts

Speakers | Speaker Hardware
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Old 20th April 2011, 02:36 AM   #980
tb46 is offline tb46  United States
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Hi,

Just as an aside, a $55.-- woofer from 1978 would be $355.-- by 2011 @ 6% annual price increase, and there were no woofers of comparable quality available for $55.-- in 1978.

I know, it still hurts. :-)

Regards,
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