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Advices on First Crossover Design (VituixCAD2)
Advices on First Crossover Design (VituixCAD2)
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Old 26th January 2019, 05:58 PM   #11
MrZoltan is offline MrZoltan
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Ho and I have used 3 meters for the listening distance in the simulation
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Old 26th January 2019, 09:54 PM   #12
ScottG is offline ScottG  United States
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3 meters works, that means we don't have baffle-step loss artifacts to look at for these graphs. (..in other words, generally a "flat" line is best.)
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Old 26th January 2019, 10:30 PM   #13
ScottG is offline ScottG  United States
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Quote:
Originally Posted by MrZoltan View Post
Hi ScottG,


I think I have messed the dimension of the enclosure in VituixCAD, and maybe one area that I have it wrong is the microphone placement in the diffraction, should I place the mic in front of the speaker each time or keep it in the center ?



I have to check it again


What do you think can cause that dispersion between 1 & 2 Khz ?


For the vertical I think it could be wrong, I suppose the LS Plan is simulated as a circular speaker and not as a planar, I will dig a bit that aspect


I am modeling a speaker that I can use as a reference to make the simulation


Any idea why there is that big bump between 50 & 100 hz ?


Thanks a lot for your help

I'm not familiar with VituixCAD for saying what to do. (..I know of it's excellent capabilities generally, but that's about it.) ..mic placement should generally be centered on the tweeter's 0 degree axis at either 1 meter (for baffle-step loss shown), or 2+ meters (without baffle-step loss). At least in real life (..but it could be different in VituixCAD.) Usually you are targeting/simulating an ANECHOIC condition (in other words no effects from any reflections or other room effects).


Again, that horizontal "flare" looks like a baffle artifact to me.

My guess is the elevated bass response is an artifact of enclosure (relative to driver parameters) and crossover. It's really not as bad as it looks though because the upper-end of the driver should be crossed-over higher in freq. (ie. it's low-pass filter needs to be raised to a higher freq.), plus you'll have floor (boundary) gain here.


General rule for midrange to woofer:

Target a high-pass crossover for the midrange near 300-500 Hz depending on its height from the floor to minimize "floor-bounce" (..do a search on that phrase).

Meanwhile the woofer should be placed closer to the floor not only for some boundary gain from the floor (which can be up to 3 db), but also to raise the freq. for it's "bounce" effect - allowing you to crossover (low-pass) higher in freq..


Ex. Magico S5, while certainly not perfect - it has a reasonably good design:

SoundStage! Hi-Fi | SoundStageHiFi.com - Magico S5 Loudspeakers

In particular note that the 2 meter graphs (..plotted at 1 meter for spl-reference) ANECHOIC:

SoundStageNetwork.com | SoundStage.com - NRC Measurements: Magico S5 Loudspeakers

Note that there is about 2db of pressure loss from the average between 50-200 Hz. The floor will add-in a bit of gain here to the result, so that loss isn't bad.

Look to fig. 5 here for IN-ROOM results (for the MKII version of the S5):

Magico S5 Mk.II loudspeaker Measurements | Stereophile.com

Note that fig. 2 is at *1.27* meters ANECHOIC (as opposed to the in-room above) and has some gain because of the baffle-step compensation. The crossover there is just above 300 Hz and the woofer is near the floor with the midrange up quite a bit off of the floor. Additionally, the filter is "steeper" to further limit floor-bounce. (..and it's not that it removes floor-bounce as seen in the IN-ROOM response 280-500 Hz dip, but the result is less than it might have been.)
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Last edited by ScottG; 26th January 2019 at 10:38 PM.
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Old 29th January 2019, 11:22 PM   #14
MrZoltan is offline MrZoltan
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Hi ScottG,


Again thank for your help on the subject, the VituixCAD thread was indeed an excellent suggestion as Kimmosto is very responsive and helpful for me to understand what aspect of the program needed my attention in this initial step.


The crossover design will be refined especially to match existing and available parts in my country.



I think I could settle with the following results for the baffle design, at least it seem to me I have less potential issues than before, what do you think ?


Sketch : I will leave the woofer higher to lessen that potential 3dB increase but will put the port closer to the floor at the back, I don't know if it's true but that seem to be an OK practice from what I have read, the port size & shape is not yet totally decided, I could still raise the baffle if needed.
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Don't hesitate if you see something that is wrong
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Old 30th January 2019, 02:45 AM   #15
ScottG is offline ScottG  United States
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..floor-standing looks pretty good assuming anechoic 3 meters up to 500 Hz.

Liked to see a bit more baffle-width and larger radius lateral cabinet edges (..that latter is more important than the former).

1.2-to-4 kHz is to elevated, particularly considering the exaggerated horizontal "flair".

Tweeter high-pass should be lowered to at least 4 kHz.. maybe 3.5 kHz.
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Last edited by ScottG; 30th January 2019 at 02:49 AM.
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Old 30th January 2019, 03:57 PM   #16
MrZoltan is offline MrZoltan
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Quote:
Originally Posted by ScottG View Post
..floor-standing looks pretty good assuming anechoic 3 meters up to 500 Hz.
It's just the diffraction simulation from VituixCAD but the listening distance set to 10000cm


Quote:
Originally Posted by ScottG View Post
Liked to see a bit more baffle-width and larger radius lateral cabinet edges (..that latter is more important than the former).
I am a bit constrained on the width of the baffles unfortunately this is already a bit more than I should have, as for the edges rounding I can't do more than close to 17mm radius with 18mm MDF, or at least i don't see how.


Quote:
Originally Posted by ScottG View Post
1.2-to-4 kHz is to elevated, particularly considering the exaggerated horizontal "flair".
Yeah that flair is moving around but I don't find what I can do to get rid of it, I just moved it a bit by playing with the mid/high placement (offset)


Quote:
Originally Posted by ScottG View Post
Tweeter high-pass should be lowered to at least 4 kHz.. maybe 3.5 kHz.

I will try to go a bit lower but this type of ribbon tweeters are not made to go low, I think 4.5Khz are the lowest crossover point


Thanks for you reply
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Old 30th January 2019, 07:07 PM   #17
MrZoltan is offline MrZoltan
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This is what I get if I bring the high crossover lower, to me it don't change much :
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Old 30th January 2019, 07:50 PM   #18
ScottG is offline ScottG  United States
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-still need to go lower with the tweeter. As far as the tweeter's capability, it's a matter of distortion and power handling/excursion, and it has a lot of surface area. My guess is that that with your filter and summed response that 3.5 kHz should be OK, but it's something you can model. (..though you should have distortion measurements of the tweeter (IB) to do that properly.) More problematic would be the pressure drop of the tweeter itself, which to an extent should have at least some correlation with the volume enclosure you have for it (..and it's a dipolar design without a rear chamber - so you should be able to get a bit more extension from it with the correct rear-chamber volume for your cross-over.)

As for the horizontal "flair".. don't worry about it too much (..if you can't really do much with the box *size and edges), instead worry about it in conjunction with the on-axis freq. response. In this case you simply have to much pressure between about 1 kHz and 9 kHz. BECAUSE of the horizontal "flair" it should actually be DEPRESSED/LOWER in pressure near the trouble-spot around 2 kHz. Based on your graph: 91 db is the average; that 2 kHz region should be about 90 db, NOT the current 93 db. BTW, this will also "help out" with the lower high-pass for the tweeter, because the overall pressure is lower (..near and lower than its high-pass).

*Note: the edges are more important than the width (as far as minor changes are concerned) - if you can *narrow* the baffle width a bit but increase the round-over of those lateral edges, you'll be better-off.
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Last edited by ScottG; 30th January 2019 at 08:07 PM.
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Old 30th January 2019, 10:15 PM   #19
MrZoltan is offline MrZoltan
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Quote:
Originally Posted by ScottG View Post
-still need to go lower with the tweeter. As far as the tweeter's capability, it's a matter of distortion and power handling/excursion, and it has a lot of surface area. My guess is that that with your filter and summed response that 3.5 kHz should be OK, but it's something you can model. (..though you should have distortion measurements of the tweeter (IB) to do that properly.) More problematic would be the pressure drop of the tweeter itself, which to an extent should have at least some correlation with the volume enclosure you have for it (..and it's a dipolar design without a rear chamber - so you should be able to get a bit more extension from it with the correct rear-chamber volume for your cross-over.)

As for the horizontal "flair".. don't worry about it too much (..if you can't really do much with the box *size and edges), instead worry about it in conjunction with the on-axis freq. response. In this case you simply have to much pressure between about 1 kHz and 9 kHz. BECAUSE of the horizontal "flair" it should actually be DEPRESSED/LOWER in pressure near the trouble-spot around 2 kHz. Based on your graph: 91 db is the average; that 2 kHz region should be about 90 db, NOT the current 93 db. BTW, this will also "help out" with the lower high-pass for the tweeter, because the overall pressure is lower (..near and lower than its high-pass).

*Note: the edges are more important than the width (as far as minor changes are concerned) - if you can *narrow* the baffle width a bit but increase the round-over of those lateral edges, you'll be better-off.

Sorry but this time you lost me, most of what you write I have no clue about


I have lowered more the tweeter filter and the mid higher filter to 3.5 Khz, I have also attenuated everything closer to 90dB, but then I have a big issue around 1Khz, the impedance there is going as low as 2 ohm (My amp wont like that I think)


Here is a bunch on sentences where I am lost :



  1. When you speak about pressure drop do you say that because I am using a vent?
  2. when you say it's a dipole design, is it based only because of the event oriented toward the back?
  3. You completely lost me creating depression to lower between 1 & 9Khz, is that a design that involve changing the volume/shape of the baffle or something related to passive electronic design ? (like I do with L-Pad Attenuation)
  4. I could in theory make the edge rounder on the baffle design but then It would be difficult to match that on the the MDF, do you have an example for me to understand what you mean ?
  5. That bump now between 15Khz & 30Khz is stubborn, but it don't matter i think I could not hear that.
I thought I was getting close but as I go it gets harder, thanks that you are sticking with me while I stumble during that process.


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Old 30th January 2019, 10:57 PM   #20
ScottG is offline ScottG  United States
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Quote:
Originally Posted by MrZoltan View Post


I have lowered more the tweeter filter and the mid higher filter to 3.5 Khz, I have also attenuated everything closer to 90dB, but then I have a big issue around 1Khz, the impedance there is going as low as 2 ohm (My amp wont like that I think)


Yup. The Impedance is a problem. "Massage" the crossover a bit more.

HOWEVER, excepting that problem it looks a LOT better with the one exception of pressure drop in the 3 kHz range. Still, that's a narrow-band "dip" - and perceptually that won't be easily heard. So with respect to linearity on and off-axis horizontally.
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