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Multi-Way Conventional loudspeakers with crossovers

Introduction to designing crossovers without measurement
Introduction to designing crossovers without measurement
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Old 12th November 2019, 04:45 PM   #721
jimk04 is offline jimk04  United Kingdom
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Hello forum

Having read the main elements of this thread, I am readying myself to try this method on my first 2 way speaker build.
Before I go further here with the details...what is the number we use to determine tweeter attenuation level down -9db.? I have a hot tweeter and may well use BSC of -3db on the woofer.
The numbers stop at 6db.
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Old 12th November 2019, 07:06 PM   #722
picowallspeaker is offline picowallspeaker  Italy
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Go to Level Calculator
Strassacker: speaker - kits - tools
(it is comprised also in CRossover Calculator )
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It's like learning sex during the Victorian era: you get to the wedding night and there are many things to do that you never imagined.
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Old 13th November 2019, 02:06 PM   #723
jimk04 is offline jimk04  United Kingdom
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Thanks for that.....good link. If I use a zobel to flatten impedance do I still use the tweeter nominal Z or the new Z?
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Old 13th November 2019, 09:15 PM   #724
AllenB is online now AllenB  Australia
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Does your Zobel cover the whole tweeter range, or just the upper rise or lower peak? Is it after the L-pad or before? Or, if you haven't decided yet, what do you want to achieve with this Zobel?
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Old 14th November 2019, 07:11 AM   #725
jimk04 is offline jimk04  United Kingdom
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I am not really sure. Following your example and my tweeter is 6ohm...adding a 10R for example gives me 3.75ohm.....as in your example. So would I put 6 or 3.75 into the calculator linked above.

My tweeter has an Fs of 720Hz with a peak of 18/19ohms at this point.
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Old 14th November 2019, 08:12 AM   #726
AllenB is online now AllenB  Australia
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It sounds as though you are putting the resistor in parallel then wanting to add the L-pad. Can I suggest instead, just use 6 ohms in the L-pad calculator and don't worry about any of the other resistors. Ie: just the two that the calculator suggests.

Doing this will have the same effect of reducing impedance variation around tweeter resonance.
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Old 14th November 2019, 08:23 AM   #727
AllenB is online now AllenB  Australia
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The word Zobel is often used differently by speaker builders. In electronics it has a common meaning ie: compensating for impedance variations so that a load (eg the whole load) looks like a simple resistor.

Often with speakers it is used to describe an RC circuit, like the one used on the woofer in this thread. This is only a part of what Zobel is intended to mean, and I ask for clarification. An RC circuit does little for a tweeter the way they are normally crossed.

More important for a tweeter is the impedance variation at the lower frequencies around resonance. The ultimate conjugate (makes it flat) is a series RLC circuit (bandstop, notch) across the tweeter, providing a simple platform for future tweaking. However the combination of a parallel resistor and second order filter, especially when tweaked, can bring the correct response.

Last edited by AllenB; 14th November 2019 at 08:30 AM.
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Old 14th November 2019, 01:37 PM   #728
Piersma is offline Piersma  Netherlands
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Default baffle step

Hi,

Could the following assumption make sense?

A 10" woofer with a sensitivity of 90dB
A 5,5 midwoofer with a sensitivity of 86dB
Mounted on a 12 (30 cm) baffle
Baffle step frequency : 115/.3 = ca. 380 Hz

If the woofer and midwoofer are crossed at ca. 400Hz, and the bafflestep Is taken into account, would the SPL of the midwoofer roughly match the woofer?
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Old 15th November 2019, 12:48 AM   #729
AllenB is online now AllenB  Australia
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Thinking 'outside the box' this way saves you from attenuating the mid.

Each of the two drivers is affected by the baffle, each in more or less the same way. When you filter each you would be best to consider the effect this is already having, to subtract this from the filter you are adding.

To make this easier to visualise I ran a sim.

[I used 6dB difference to keep things ideal, you chose 4dB which is more practical. The difference is not clear cut which is why I avoided using 4dB for the sim.]

What this shows is what each driver response should look like (darker trace), vs the amount of filter effect required to achieve it considering the baffle effect. Eg: The first (woofer) plot shows that you need to cut more to compensate for the rising response. This can mean using a larger inductor, aiming for a lower cutoff frequency than first expected.
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File Type: png Image31.png (30.6 KB, 69 views)

Last edited by AllenB; 15th November 2019 at 12:52 AM.
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Old 15th November 2019, 08:33 AM   #730
Piersma is offline Piersma  Netherlands
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Thumbs up Thanks

hi Allen,

Thanks for your response and clear explanation.
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