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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 18th May 2019, 01:06 AM   #691
brooks is offline brooks  United States
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Btw - I do have the specs and freq graphs for all Philips drivers. I have found some great old docs on these, and also found a gem of a online book by M.D. Hull of Philips ‘Building Hi-Fi Speaker Systems’, from 1980, which includes specs on my drivers, acoustic theory, loudspeaker design, and example systems.

In doing some tests, I’ve found that one mid (Mid#2) is damaged, as its output is about nul and distorted. So I am replacing them with the same type as the Mid #1 (AD5060) which I feel better not having two different mids to worry about with different responses. I’ll remove the bandstop add a simple bandpass and should have a much better speaker. Thanks again.
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Old 21st May 2019, 06:01 PM   #692
Tournesol is offline Tournesol  Belgium
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Quote:
Originally Posted by AllenB View Post
We'll need to use one resistor and one capacitor (per woofer).
I have not read the entire thread, and, may-be some one has even said this, but this is far to be optimal.
To linearise a speaker, you need to compensate both its inductance, by a RC network in parallel, and its peak of impedance at its resonance frequency, by a RLC network, in parallel too.
See:
La correction d impédance RC série
La correction d impédance RLC série
La correction d'impédance RC et RLC série

As the good speakers manufacturers usually provide the impedance curve of their speakers, no need to any measurement on your side.
After the correction done, you will have a flat impedance curve, usually at the DC resistance of the coil (6 Ohms for a 8 ohms speaker, 3 for a 4 Ohms). And you can easily calculate your filter on the theoretical values, it will work as expected.
Just my two cents..
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Last edited by Tournesol; 21st May 2019 at 06:03 PM.
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Old 22nd May 2019, 02:09 AM   #693
AllenB is offline AllenB  Australia
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This is a good tool. I have used this technique of RLC compensation on a woofer's impedance when I introduce a finite source impedance. For example a crossover or an amp. It can help to get the wanted result.

I considered this when starting this thread. My thoughts were that typical woofer resonance is around or below 100Hz. Typical crossovers of this kind, are around or above 1kHz. This is an order of magnitude difference. In other words, this is far enough apart in frequency that the interaction can be considered insignificant for most purposes.

I also find RLC compensation is something that can be applied to a tweeter at its resonance.
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Old 23rd May 2019, 01:38 PM   #694
Tournesol is offline Tournesol  Belgium
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Quote:
Originally Posted by AllenB View Post
This is a good tool. I have used this technique of RLC compensation on a woofer's impedance when I introduce a finite source impedance. For example a crossover or an amp. It can help to get the wanted result.

I considered this when starting this thread. My thoughts were that typical woofer resonance is around or below 100Hz. Typical crossovers of this kind, are around or above 1kHz. This is an order of magnitude difference. In other words, this is far enough apart in frequency that the interaction can be considered insignificant for most purposes.

I also find RLC compensation is something that can be applied to a tweeter at its resonance.
This practice (RLC for all speakers) has 4 major benefits.
1- It helps to have theoretically calculated passive filters to work as expected, not having to tune them on the bench with a mic.
2- It helps the speakers , as they have now a flat impedance curve, to keep their response curve unchanged, whatever the serial impedances of the cables and passive filters.
3- It helps to improve the damping of the speakers: you can easily hear the difference (power amps off), by hitting the membrane of the boomer with your finger.
4- It helps the amplifier(s), especially their power supplies, to get more coherency all over their frequency range, having no more to deal with a schizophrenic Voltage:current behavior. May-be too, we will enjoy a benefit on the micro dynamic looking at the levels in their feedback paths to compensate the difference between voltages/currents VS frequencies.

About the "insignificant", OMHO, the best speaker assembly is the one with the less ways as possible, to reduce the acoustic problems of crossovers (phase turns etc.).
So, in my case a two ways (with horn), the crossover frequency is not so far from the resonance frequency of my horn driver, and close too to the first break of the membrane of the boomer. I can hear the difference, despite my filters are 48dB/oct, comparing with/without RLC comp. on each of the two speakers.
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Last edited by Tournesol; 23rd May 2019 at 01:43 PM.
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Old 23rd May 2019, 02:46 PM   #695
picowallspeaker is offline picowallspeaker  Italy
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A boomer!
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Old 23rd May 2019, 03:22 PM   #696
AllenB is offline AllenB  Australia
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I agree that the impedance of a compression driver, and a horn with a cutoff frequency, can be a significant problem. Also these often have to be cut close to their limits to suit other needs.

I have some concerns with other points you have made, but at this level I have no problem with them.
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