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Multi-Way Conventional loudspeakers with crossovers

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Old 16th April 2012, 04:24 PM   #1
jim1961 is offline jim1961  United States
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Default Cone breakup questions

Click the image to open in full size.Let me start by saying hello to everyone. I am new here and hope to share and learn.

Let me start with what I am working with.

Audio Concepts AC-10 woofers (2)

Dynaudio d54af mids

Dynaudio d21af tweets

The Ac-10 woofers have a breakup frequency at about 1600hz. The d54 around 6200hz.

I have been using a 1st order crossover with zobel. Lately, I have attained a Dayton Omnimic, and have finally been able to measure whats going on.

My main question is this:

1) My first inclination was to try to build notch filters to take care of the cone breakups. As I understand things, these come in two versions. Parallel and series.

Looking at the wiring of each, its seems Series would be my preference given the circuitry is not in the signal path. But from what I have been able to understand so far, these are primarily used for resonate frequency issues.

Series Notch Filter Designer / Calculator Help

Parallel seems aimed at dealing with broad frequency peaks within the frequency response of the driver.

Parallel Notch Filter Designer / Calculator Help

Neither describes what I am trying to do. So which do I use? Why? And is there a calculator I can use to determine the parts I need based on the frequency and shape of the peak(s)?

Last edited by jim1961; 16th April 2012 at 05:45 PM. Reason: adding a graph
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Old 16th April 2012, 05:15 PM   #2
jim1961 is offline jim1961  United States
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Click the image to open in full size.
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Old 16th April 2012, 05:18 PM   #3
Pano is offline Pano  United States
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Jim, you should probably use the attach image feature here on the forum. Also, PNG or GIF formats work better for this sort of image than Jpeg. Just FYI.
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Old 16th April 2012, 05:22 PM   #4
jim1961 is offline jim1961  United States
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The graph above is a ROUGH display of what I measured. Measuring criteria was:

Distance 1 meter (39inches)
Time: 5ms

Each driver measured separately with existing crossovers wide open (without attenuation)

-Sorry about the size of the graph. Trying to fix it-

Last edited by jim1961; 16th April 2012 at 05:46 PM.
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Old 16th April 2012, 05:25 PM   #5
jim1961 is offline jim1961  United States
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Quote:
Originally Posted by Pano View Post
Jim, you should probably use the attach image feature here on the forum. Also, PNG or GIF formats work better for this sort of image than Jpeg. Just FYI.
Attach as opposed to inserting? How?
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Old 16th April 2012, 11:45 PM   #6
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Parallel notches are usually used to take the shoutiness out of single driver systems;
series notches are used with more conventional systems when required, e.g. metal cone drivers. It's better to use drivers so that cone breakup occur outside the passband, that way notch filters may not be required if the breakup isn't too severe. If you've been able to live with 1st order crossovers, it probably isn't too bad.
(The idea that series notches would be used on a woofer's fundamental resonance is laughable, but peddled on some car audio sites...)
Irregularities in an impedance graph is also a useful tool in dealing with cone resonances.
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 17th April 2012, 12:52 AM   #7
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by PeteMcK View Post
(The idea that series notches would be used on a woofer's fundamental resonance is laughable, but peddled on some car audio sites...)
It's not so daft an idea really. Just very hard to find good capacitors of sufficient value. You do it with tweeters a lot when using low order filters.

Back on-topic, Jim1961, I have a feeling you are trying to make a silk purse out of a sow's ear here. You'd find it all a lot easier if you crossed over lower, perhaps at the bafflestep point of around 500 Hz to (say) a 5" midrange. Big high-inductance woofers are going to fight you all the way with a high crossover point. That's how it is.
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Old 17th April 2012, 01:23 AM   #8
jim1961 is offline jim1961  United States
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A 5" mid would be easier to work with from the point of view of lending itself to a lower crossover frequency, yes.

But 2" domes is what I have, and what I am limited in working with.

Does 800hz seem too high for a 10" woofer in your opinion? Or anyone elses?

Other choices include going to a 2nd order network. Possibly a notch and a 2nd order network. But I wanted to explore notch filtering because my understanding of them isnt sufficient to know what and how much they can affect the problem of cone breakup.

As far as silk purses go, I think most of us give that a try if we can get away with it
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Old 17th April 2012, 02:00 AM   #9
system7 is offline system7  United Kingdom
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Jim, are you using some modelling software? Like this which is useful even if it really only includes Visaton drivers, hopefully you can find similar:
Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories

My own feeling, without knowing the parameters of the bass unit, is that you need second order filtering here. maybe Likwitz-Riley slopes. First order makes some fairly extraordinary demands of drivers. Like smooth frequency response and good overlap. Have a look at these two Visaton designs (with crossovers) that use dome midranges:
Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories
Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories

Even notches are not easy. Close to crossover they drop the impedance and ring if the Q is high. Well beyond it they are more manageable.
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Old 17th April 2012, 03:50 AM   #10
jim1961 is offline jim1961  United States
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To make sure I am understanding you correctly, are you saying that using a notch 1 octave above the crossover could cause as much harm as good?

I have not investigated modelling software. I was hoping, now that I have decent measuring equipment, to basically use test measurement results to allow me to try various passive crossover ideas and see which work out the best through basically trial and error.

But right now, i am at the information stage. I havent decided on any one approach as of yet.

Let me add that the speakers, just as they are, sound reasonably good to me. But I am also aware that there is room for improvement. So, I am making an effort to see if I can get a bit more out of them. And the cone breakup frequencies stand out as the areas of most needed attention.
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