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Try your hand at a 2 way VituixCAD crossover with full Spin-O-Rama data (108 sweeps)!

DaveFred

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Hello,

I have seen many crossover simulations with VituixCAD, but very few with the full 360º X and Y measurements in 10º increments of each driver that Kimmo recommends.

Here are the full measurements of a sealed two way I am working on with the Dayton DA175 woofer and Seas 27TFFC tweeter.

Attached are four zip files,

27TFFC - Tweeter data (names in the zip might show 27TFF and 27TFFC, I named one set wrong, just load them all from that directory)
DA175 natural - Woofer with GHP
DA175 GHP 540uf -Woofer nearfield with Geschlossen mit Hochpass (540uf high pass filter for the woofer built into the measurement)
DA175 27TFFC ZMA - Tweeter and woofer impedance files

My suggestion is to extract them to their own folders so they are easier to find and load (and to not confuse the two sets of woofer data)

The only "distance" data to be entered into VituisCAD is "-165mm" in the Y offset for the woofer.

There is no "Z" or delay to be entered anywhere for the tweeter as the time of flight was captured with dual channel Arta measurements.

Here are a couple of different scenarios,

Be sure and check out all the excellent graphs that are available when you have a full data set.

Scroll through the frequency range both vertical and horizontal and look at the lobing pattern as the frequency changes.

See the horizontal and vertical polar plots, line charts, graphs, etc.

There is sooo much more to explore when you have more than a simple on axis woofer/tweeter response.

Here are a couple of XO's I have been playing around with, you can enter them and see what the full results are,

Please feel free to post any XO's you come up with as well!

ASR xo1.png


ASR 6p1.png


ASR xo2.jpg


ASR 6p2.jpg



ASR xo3.jpg


ASR 6pk3.jpg


ASR xo4.jpg


ASR 6pk4.jpg
 

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Draki

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An IIR active variant (since no bass ZMA file)
 

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Draki

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Variant 1: This is what I would tinker with as an acceptable compromise between power response, ER, listening window, phase and impedance...
It does take a leap of faith to weigh a PR/ER response over a flat on-axis FR, but it works (for me at least). One can fine tune and EQ 'till the cows come home but some starting point is needed.

Variant 2: Emphasis on on-axis, at the expense of PR and phase. More complex too, shown for comparison.
 

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alex-z

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Are these measurements just the drivers, or is there a baffle/cabinet involved?
 

OrionX76

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Dave, thanks for the data! I'll give it a go.

This challenge brings up some interesting questions regarding the measurement setup:

I see you are using ARTA. I use REW and I'm wondering how they compare with regard to the set up procedures. With REW we measure each driver on driver access but at equal Z-distance (1Meter) from the baffle. We then set a hard timing offset (usually 2.907ms without correcting for speed of sound at elevation/ temp) for all measurements.

The first set of good data I was able to take required a serious level of setup and patience. I am only confident I was accurate to +-10mm for the mic placement. I'm currently designing a jig that would keep everything plumb and square between driver measurements.

Does ARTA have a solution that allows you to get around this kind of measurement prep?

It looks like you are able to measure both drivers from tweeter axis and then call out the vertical offset for the woofer in VituixCAD. How does this effect the accuracy when you go to make the vertical axis measurements?
 

alex-z

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First design is expensive due to the large inductor on the notch filter, prioritizing a +/-1dB response.

Second design is focused more on cost, with a bit more deviation in response and possibly distortion from the tweeter playing lower.

Neither version is great for vertical dispersion, although nothing unusual by 2 way bookshelf standards.

Just my amateur 2 cents.
 

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DaveFred

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Dave, thanks for the data! I'll give it a go.

This challenge brings up some interesting questions regarding the measurement setup:

I see you are using ARTA. I use REW and I'm wondering how they compare with regard to the set up procedures. With REW we measure each driver on driver access but at equal Z-distance (1Meter) from the baffle. We then set a hard timing offset (usually 2.907ms without correcting for speed of sound at elevation/ temp) for all measurements.

The first set of good data I was able to take required a serious level of setup and patience. I am only confident I was accurate to +-10mm for the mic placement. I'm currently designing a jig that would keep everything plumb and square between driver measurements.

Does ARTA have a solution that allows you to get around this kind of measurement prep?

It looks like you are able to measure both drivers from tweeter axis and then call out the vertical offset for the woofer in VituixCAD. How does this effect the accuracy when you go to make the vertical axis measurements?

I used to use REW and a USB mic.

Kimmo hates USB mics as they do not record time of flight/phase and told me over and over that is what is needed for proper measurements is an XLR mic and external sound card.

Read the measurement setup instructions from Kimmo for Vcad and they really are simple. I have to say (I'm kinda thick headed) that I didn't fully understand/get them until I simply followed along step by step like a recipe and did them a couple of times. Because I am using an automated turntable (which Arta supports), taking 100+ measurements is really quite easy.

https://kimmosaunisto.net/Software/VituixCAD/VituixCAD Measurement Preparations.pdf

I am using full dual channel measurement, which means Arta listens to the what the amp is putting out (feedback loop) vs. what it is being sent to the amp and compensates for any deviation the amp might be imparting on the signal being measured.

I still use REW for simple "lets look" measurements and distortion plots because of how simple it is.

David.
 

OrionX76

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I used to use REW and a USB mic.

Kimmo hates USB mics as they do not record time of flight/phase and told me over and over that is what is needed for proper measurements is an XLR mic and external sound card.
David.

Absolutely. I use a mic with calibration file as well as the dual channel set up.

In his documentation, Kimmo recommends measuring each driver on axis. This becomes a challenge when trying to keep everything lined up perfectly... especially when I go to do the vertical measurements.

It looks like you did all of your measurements from the tweeter Y-axis and used the Y-axis of the woofer to adjust and simulate the response. Is this an option only available with ARTA or can this be done with REW in a dual-channel set up as well? Any down side from doing it this way?

And now the fun part... I'm finally sitting down to play with the data this morning. Thanks again!
 

OrionX76

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This is a pretty good result I think... I am still learning so be gentle ;-)

I have included the vertical lobe and heat map graphs for reference. Seems ok for a 2-way?

I have some questions on the power and impedance response. Is this acceptable for a decent amp? My test rig is an Emotiva 50watt 2-channel. I have done a couple other projects with similar impedance curves and it doesn't seem to have an issue. I wonder about lesser amps and cheap home theater systems holding up. I try and shoot for a minimum 4 ohm load on my projects.

And I have no idea really what to look for with regard to the power curve... Any discussion on this would help a lot!
 

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ctrl

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So, after the "normal" crossover tunings have already been presented, the somewhat more exotic solutions remain. In a time long before Linkwitz-Riley existed, third order Butterworth was very popular :)

This filter has significant weaknesses in vertical dispersion - a tilted radiation lobe. But when a driver is connected in reverse polarity, it gives excellent group delay.

The version here is intended for near-wall placement in an environment with low reverberation time.
1617301113767.png 1617301134528.png 1617301249040.png 1617301292841.png

Looking at the DI, a version with even slightly less sound power in the frequency range 2-5kHz could be advantageous.
1617301350523.png 1617301384970.png

I deliberately left the raised upper treble as it is, which should not be a problem with a slight angle. For the notch filters, the cheapest air core coils will do (but keep in mind the total resistance). The 15µF capacitor may also be an electrolytic capacitor.
 

Draki

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I would really like if you could expand on that statement (please).
Having been used to the traditional flat on-axis for a long time, a switch to a multi-axis measurement and the excellent VituixCAD (and the concept of power response, DI, dispersion and the physical layout and shape of the baffle, etc) was a revelation. However it took time to sink in, to "unlearn" the flat-on-axis above all concept. The practice proved it (to me) to be the correct way. I didn't make any blind listening tests so this is my subjective opinion - i.e I find the loudspeakers with the correct power, DI etc to be - in a lack of a better expression - neutral. Like water - tasteless and transparent. Dull perhaps, nothing exciting - the excitement comes from the program played. It was hard to admit to the imperfections (faults!) of the already made loudspeakers which had all the right ingredients by the book, in nice boxes made with a lot of effort and were designed by flat-on-axis only.
I must say that Kimmo (the author of VituixCAD) provided a lot of support and really insisted on some principles which ultimately proved him right all the way.
 
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DaveFred

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Absolutely. I use a mic with calibration file as well as the dual channel set up.

In his documentation, Kimmo recommends measuring each driver on axis. This becomes a challenge when trying to keep everything lined up perfectly... especially when I go to do the vertical measurements.

It looks like you did all of your measurements from the tweeter Y-axis and used the Y-axis of the woofer to adjust and simulate the response. Is this an option only available with ARTA or can this be done with REW in a dual-channel set up as well? Any down side from doing it this way?

And now the fun part... I'm finally sitting down to play with the data this morning. Thanks again!

All measurements were done 100% on axis to each driver, that is why you need to make the woofer -165mm, other wise Vcad would treat the woofer and tweeter as coincident drivers (i.e., like a coaxial).

I made a speaker stand with a backstop so as the speaker was moved, Z was maintained. The speaker stand is mechanically fastened to the turntable so that the axis of rotation is the front centre of the baffle. The turntable is reasonably heavy and not easily bumped when moving the speaker around for different axis/drivers.

I looked to buy a microphone stand that only only moved in Y while rigidly maintaining all other parameters and I could not find one, so I built one. It only moves up and down.

Between the turntable/speaker stand rig and the microphone stand rig, I am quite confident I am maintaining the same distance between the drivers and the microphone between measurements. Because I am a very anal person, I also use a self leveling construction laser (vert. and hor. beam) on a second tripod to align everything. If you are interested, I could make a post about all of this with pics. Let me know.

David.
 

OrionX76

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A post covering setup would be excellent!

I have been mulling over a jig to keep everything square and level. Thinking of using either aluminum or unistrut.

It would be nice to see a well organized setup process with all of the considerations addressed in one post.
J.
 
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DaveFred

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Here is what I am going to spend some time listening to today,

april 2 r3 trying this April 2nd was hold 7 XO-schema-3.jpg


april 2 r3 trying this April 2nd was hold 7 Six-pack.jpg


The high resistance with the main inductor on the woofer is because it is 20g.

I will let you know how it sounds... :)

David.
 
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DaveFred

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Work continues on the DA175/27TFFC Bamboo project.

This is the crossover I am going with. It is bright on axis at the high end, but get off axis a little and it levels out. Often speakers have to be "toed" in because of a dead flat on axis response, these ones won't.

F3 on these sealed speakers will be about 47Hz.

Not shown in the crossover diagram is the 560uf high pass filter (Geschlossen mit Hochpass) on the woofer that flattens out the woofer response because the cabinet is undersized.

The REW graphs are real measurements of the actual crossover and the rest are simulations from VituixCAD based the XO design and 100+ measurements of both the tweeter and woofer individually in 10º increments in both horizontal and vertical.

20210403_153814_resized.jpg20210403_153443_resized.jpgDA175 27TFFC response.jpgimp april 3rd going to build R4  Impedance.jpgfilter april 3rd going to build R4  Filter.jpgphase april 3rd going to build R4  GD+Phase.jpgVer Polar april 3rd going to build R4  Directivity (ver).jpgVer up dir april 3rd going to build R4  Directivity (ver, pos front).jpgHor polar april 3rd going to build R4  Directivity (hor).jpgHor dir april 3rd going to build R4  Directivity (hor).jpgSPL april 3rd going to build R4  SPL.jpgPower and DI april 3rd going to build R4  SPL.jpgapril 3rd going to build R4  XO-schema-4.jpg
 
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