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Multi-Way Conventional loudspeakers with crossovers

frequency amplitude R//C serie correction
frequency amplitude R//C serie correction
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Old 26th February 2020, 01:23 AM   #11
diyiggy is online now diyiggy
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oh I see... thank you for the tip,



I have to dive in Arta or REW manual...if they are the ones you refer about? I still have to find time to RTFM... I definitly have to. Not aware they can do such things.
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Old 26th February 2020, 02:10 AM   #12
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frequency amplitude R//C serie correction
Both of those will work. They don't do it for you, you have to do it manually.

For example, run your amp into a 1k resistor in series with a 10 ohm resistor. Plot the Voltage across the 10 ohm resistor vs frequency. Set the level so it measures something like 10mV. Replace it with the speaker. Trace the plot. Derive minimum phase.
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Old 26th February 2020, 11:48 AM   #13
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Thank you AllenB.
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Old 27th February 2020, 03:21 PM   #14
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Default understatment of R//C values

So playing a little with Xsim which default library speaker model is 8 ohms flat impedance rated, my understanding of the R//C in serie with the driver :

C value is giving the low end limit of the spl curve renforcment i.e the top of the climb towards the low frequencies cut off, i.e. spl is climbing as the frequency goes back.

For illustration: if C = 6.8 uF a first order high pass is giving circa 5850 Hz
below 5850 the spl dropes 8 dB per octave if acting as a first order high pass.

R is giving the spl amplitude of the highest spl renforcment which is at XO position, here for the illustration 5850 Hz.. then the spl is slowly droping towards the higher frequencies till the high end sp level given by the tweeter raw spec, for instance, 0 dB (flat) at 20 kHz, spl is the effecitienty of the raw driver here, for instance 90 dB/2.88 V.

For 1R I have a 3 dB bump and the more I raise R value the less the low-end spl increases which will give a total smoother curve; for illustation with 1R5 the bump is 1.5 dB only.

Am I right or not please about the mechanism of this serie R//C frequency correction filter, please ?


R being a simple wirewound cement resistor : has it an increase of inductance following the frequency increase of the curve ? Said differently, does it give an hearable low pass as an inductor effect in the high end, shorting sooner the curve than without the resistor ? Better an Ayrton Perry type here or a bulk resistor or simply can not be heard ?

I advance appologize for these 2 cents questions.

Also as an icing of the cacke ,what is the effect on the phase of such filter please ? Better to avoid such filter ?
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Old 27th February 2020, 09:21 PM   #15
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frequency amplitude R//C serie correction
Again, you haven't shown me your schematic, I have to guess.

Here is my guess.. Look at the frequency where the capacitor equals 1 ohm. Below this the parallel combination acts like a resistor and above this it acts like a short circuit. This causes the higher frequencies to tilt up, (actually the lower ones to shelve down).

Quote:
wirewound cement resistor : has it an increase of inductance
Very small. Not a problem at audio frequencies.
Quote:
what is the effect on the phase
If it gives you better response, then use it.
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Old 28th February 2020, 12:45 PM   #16
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Thank you so much AllenB,

I realise I missunderstood the Dickason book about it. the shematic is not so clear and I understood. I thought it was the lowest frequency till the shortcut that tilted up... and it's quite the oppositt... Great step up for my understanding

I thought it was a bobsleigh curve and it's a launching ramp instead

I didn't give you the values for two reasons : my original question was about to understand the concept for any crossover and refering to the crossover I study I haven't the inductances values nore the exact capacitances. I just see it is in the midle of a LR4 cause there are 2 shunted inductances.


Ok for the phase, curve is more important first, so forgett the phase if you need to correct the curve.

So the idea to choose the capacitance as a starting frequency (first order serie cap) is good but the curve will tilt up towards the highest frequency. the higher the Z of the resistor the stiffer the launching ramp and I assume the spl bump at the end is the independance curve at the frequency level + the Z of the resistor ?
Am I right know ?

Sorry to have not a LCR to give you filter values for a proper more precise illustration, but I haven't a LCR yet...and frankly it doesn't matter for my understanding. I still have to build a diy box for that to use with a Arta or Rew to measure in real life and see the result in a real filter... one step at once

Thank you again AllenB, your help is much appreciated. I wanted first to understand the mechanism of this serie R//C. So the behavior is near a L-pad ... sort of.
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Old 28th February 2020, 08:36 PM   #17
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AllenB, I have a doubt at reading my old edition of the Dickason coocking book,


Does it tilt down the spl just after the short instead, so at the beginning jut after the frequency given by the cap without tilting up the high end ? That's the picture on the book that introduce a doubt ?!
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Old 28th February 2020, 11:30 PM   #18
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frequency amplitude R//C serie correction
Your understanding is much better.
Quote:
Originally Posted by diyiggy View Post
Does it tilt down the spl just after the short instead, so at the beginning jut after the frequency given by the cap without tilting up the high end ? That's the picture on the book that introduce a doubt ?!
There are inductors, and the driver impedance is not simple. Anything is possible.
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Old 29th February 2020, 07:10 AM   #19
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The problem with loudspeaker cookbooks is that they were never meant to teach you how to design loudspeakers.
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Old 29th February 2020, 11:26 AM   #20
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Hum...indeed... that's why I ask! in his book Dickason said one is in the dark with these corection circuits.... and must go with trial and error...so one have to understand the inductors in shunt play a role...in the RL4 indeed there is a shunted coil after the serie R//C... so a part of the current is gojng througj the coil and the tweeter in the same time....hoping the formulas in the soft are working well for such circuits...

Thank you gentlemen
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