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Post Directiva r1 Passive Crossovers here

abdo123

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This looks very promising.

As long as the loudspeaker can still be called a 4 Ohm LS according to the official designation (impedance always >= 3.2 Ohm), I don't see any problem if the impedance falls below 4 Ohm.
But your min 4 ohms are of course even better.


Make sure that the component values always remain within the E12 series range. A coil with 2.31mH will be hard to find ;)

Is there a way to calculate sensitivity with these passive crossovers? obviously that's an important parameter to include in the process (that can be somewhat ignored in active crossovers).
 

TimVG

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This looks very promising.

As long as the loudspeaker can still be called a 4 Ohm LS according to the official designation (impedance always >= 3.2 Ohm), I don't see any problem if the impedance falls below 4 Ohm.
But your min 4 ohms are of course even better.


Make sure that the component values always remain within the E12 series range. A coil with 2.31mH will be hard to find ;)

I'm looking at readily available crossover parts right now. Thanks for the tip. The issue was that part of crossover was a library block from the vcad library and the only option is to tune the whole block according to frequency. E12 snap was in place but it won't let me tune individual parts. I was able to adjust it to a 2,2mH coil by adjusting the crossover value of the block.

I agree that the result looks good in terms of frequency response, directivity, impedance, and parts count. I wouldn't concern myself with the 2.31 mH inductor nearly as much as the 15 mH inductor in the tweeter circuit. That would be... atypical (and expensive).

I'm seeing these go for €20 - I guess that's a lot then?
 

ctrl

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I wouldn't concern myself with the 2.31 mH inductor nearly as much as the 15 mH inductor in the tweeter circuit. That would be... atypical (and expensive).
I agree, neither is ideal. Of course, you should also pay attention to the costs of the components, in addition to the possible feasibility of the component values.


Is there a way to calculate sensitivity with these passive crossovers?
Oh no, now the sensitivity discussion starts ;)

If I remember correctly, I have adjusted the frequency responses in the v20 VCAD project so that the sensitivity should be roughly correct.
So about [email protected] in the low bass range. You can easily check this again with a VCAD enclosure simulation.


I'm seeing these go for €20 - I guess that's a lot then?
If that's for a 15mH air coil, then it's very reasonable.
 

Phorize

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Out of interest, it it considered advantageous to house the cross over in the box, given the possible advantages of easy iteration of the crossover if housed externally?
 

TimVG

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If that's for a 15mH air coil, then it's very reasonable.

Cost would come down to €72 €51 per speaker for network components using air core coils and Jantzen standard z-cap capacitors. I doublechecked if all the values check out in terms of availability. I have another one that doesn't dip under 6 ohm and with slightly better behaviour still, but more parts on the woofer.

1633897735210.png


Final sim

1633894997891.png


Comparison to standard R1 as tested (ON & PIR)

1633895134865.png
 
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617

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Out of interest, it it considered advantageous to house the cross over in the box, given the possible advantages of easy iteration of the crossover if housed externally?

Housing passive crossovers externally is not uncommon but the typical solution if you want to make changes is to mount it to a removable panel of the speaker. I've seen designers do two crossovers in a switch box though.

I don't think it would make any difference for sound.

Different designers have different jigs for prototyping crossovers but most commonly you will see pairs of wires from each driver coming though the port tube and they will make changes to the crossover using alligator clips or terminal blocks.
 

TimVG

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If that's for a 15mH air coil, then it's very reasonable.

Updated my post. By manually remaking the vcad library block, turns out the 15mH air coil was completely redundant! €51 per speaker in this version. Will post an alternative tomorrow.
 

Zvu

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@TimVG Don't sweat over parts count. If it is on the schematic, it does something good for the loudspeaker. Wait till i get to my computer and do a sim or two :)
 

3ll3d00d

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I had a go, ended up with something v similar. You can vary the R in the RC on the tweeter to shape the response, with 8.2 then it might be a little bright on axis but the DI is smoother

1634160354300.png


bump it up to ~18 & the DI a bit less smooth but on axis is a bit more on target

1634160464642.png


probably have to listen in the target room/setup to decide which one to go with (if not using any dsp)

haven't checked cost but would expect this to be fairly cheap, if really trying to cut costs then probably just accept a bigger DCR on the 1st woofer coil (and probably tweak other components to pad tweeter down a bit) though cutting costs given driver prices seems a bit of an odd move to me :)
 

617

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I had a go, ended up with something v similar. You can vary the R in the RC on the tweeter to shape the response, with 8.2 then it might be a little bright on axis but the DI is smoother

View attachment 158856

bump it up to ~18 & the DI a bit less smooth but on axis is a bit more on target

View attachment 158857

probably have to listen in the target room/setup to decide which one to go with (if not using any dsp)

haven't checked cost but would expect this to be fairly cheap, if really trying to cut costs then probably just accept a bigger DCR on the 1st woofer coil (and probably tweak other components to pad tweeter down a bit) though cutting costs given driver prices seems a bit of an odd move to me :)

Lots of people already have expensive amps, which are essentially investments in passive speakers. Well, not an investment. What do you call an asset which costs a lot and can only be recovered on ebay?

I'd be willing to bet one of these passive crossovers would be indistinguishable from an active set up. Just my feeling. Would be a fun blind test.
 

BenB

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I had a go, ended up with something v similar. You can vary the R in the RC on the tweeter to shape the response, with 8.2 then it might be a little bright on axis but the DI is smoother

bump it up to ~18 & the DI a bit less smooth but on axis is a bit more on target

probably have to listen in the target room/setup to decide which one to go with (if not using any dsp)

haven't checked cost but would expect this to be fairly cheap, if really trying to cut costs then probably just accept a bigger DCR on the 1st woofer coil (and probably tweak other components to pad tweeter down a bit) though cutting costs given driver prices seems a bit of an odd move to me :)
This looks pretty good. I noticed you were the only one to post in this thread who has a 17.9 mm offset next to your tweeter icon. I asked about how the offsets were handled, but didn't get a really satisfactory response.

Looking at the response text files for the woofer and tweeter, it appears as though the files include phase delay associated with 3 meters of travel time at 340 meters per second.

Interestingly, the relative timing between the tweeter and the woofer is the same in the text files for a mic location above the speaker as it is for a mic location below the speaker. This means there has to be another method for the simulation software to know about the Y offset. (Since the extra travel time isn't captured in the files.) I suspect that's why you want/need to specify the Y offset on the woofer. In contrast, there appears to be a delay associated with the woofer in the on-axis measurement, and that delay goes away off-axis. This implies that the Z offset is already captured in the files, and if the simulator adds another Z offset, you would be doubling it. With this in mind, you may want to remove the 17.9 mm offset from your simulations, which may cause a relative change of about 37 degrees at 2 kHz.

Or maybe others ought to add the Z offset... or maybe I'm completely off base and it doesn't mean what I think it does.

It would be nice to have an expert on the simulation software and/or the software that generated the files weigh in.
 

McFly

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If you add a Z adjustment with a passive crossover, that measurement must be physically built into the cabinet, e.g. most of Troels Gravesen designs.

The drivers and their responses captured for this particular project have the drivers built onto the same flat baffle. Acoustic centers easily aligned by adding a timing delay to a driver in the DSP.
 

3ll3d00d

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I noticed you were the only one to post in this thread who has a 17.9 mm offset next to your tweeter icon. I asked about how the offsets were handled, but didn't get a really satisfactory
I interpreted https://www.audiosciencereview.com/...r1-passive-crossovers-here.27189/#post-935940 as meaning the additional offset is required (as it has been added digitally in that active implementation). I didn't notice any info on how exactly the data was generated so i can't say if it is correct or not.

I did check with and without though, as far as I recall there is not much difference either way so does not seem a big deal in practice. Certainly for some other speakers, it makes a v large difference so would be important.
 

BenB

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I'm afraid I wasn't being sufficiently clear in my questions and concerns regarding the offsets and how to deal with them. I will try to add clarity with this post.

The Directiva 1 design is a two-way design in an off-the-shelf box that does not time align the woofer and tweeter. The tweeter is above and effectively in front of the woofer. From directly below the speaker, you would expect the woofer energy to reach you before the tweeter energy, because of the vertical offset between the drivers. From in front (on-axis), you would expect the tweeter energy to arrive slightly before the woofer, because the woofer is effectively a little bit farther away. From directly off to the side (left or right), you would expect the energy from the woofer and tweeter to reach you practically simultaneously.

In order to correctly simulate the response at any location in space, the relative distances to the drivers must be accurately represented. (The impact of errors here will obviously depend on the magnitude of the error.) In order for this to happen, there must be synergy between the delays introduced in the simulator, and any delays captured in the data files themselves. If the data files captured a delay, then the simulator needs to avoid introducing that same delay, or else it will double that delay and be in error. If the data files did not capture a delay, then the simulator needs to account for that delay, or else it will be in error.

I went through the trouble of turning spectral plots into time domain (impulse response) plots. For clarity, I decided to use distance (mm) on the x-axis. The measurements were apparently taken from 3 meters away.

Let's start by seeing what happens on the sides (left and right). I don't know if there's a standard for which is "left" and which is "right". Would it be from the speaker's perspective or the listener... at any rate, it doesn't matter for this analysis. Left or right should show a roughly equal distance to the tweeter and the woofer.

Impulses_mm_Left.png
Impulses_mm_Right.png
The tweeter looks a lot more impulsive at this angle than the woofer, but we can see that they start to respond to the energy at around the same time (and distance).

Now let's look above and below.

Impulses_mm_Top.png
Impulses_mm_Bottom.png

There's a large vertical offset between the woofer and tweeter, so we might expect to see a large difference between the alignment here, but we don't. The woofer and tweeter still both begin to respond at about the same time / distance. This implies that the simulator will need to account for the vertical offset.

Let's see what happens on-axis:
Impulses_mm_onAxis_annotated.png
Both the woofer and tweeter are much more impulsive at this angle (have much more high frequency energy than at the other angles). Interestingly, there appears to be a delay associated with the woofer, when compared to the tweeter. The files appear to capture the fact that the woofer is farther from the mic position than the tweeter is. This implies that the simulator needs to not account for the z offset between the drivers, if it wants to represent the natural physical layout of the drivers on the baffle. However, if the system designer wants to manipulate (or compensate for) the natural physical layout, they can do so.

I believe this is why Rick had a delay in his active crossover, but had a z offset of 0 (none) for his tweeter and woofer. The z offset was apparently already accounted for in the files (even though the Y offsets weren't... which is a strange inconsistency and makes me concerned that everything may not be fully understood by all involved, myself included). To be clear, the crossover delay and the z offset are not the same thing at all. The crossover delay is a fixed amount of time regardless of mic position. The Z offset generates a delay that is dependent on the microphone position. By aligning the response on-axis, Rick has effectively misaligned the response at other positions. This is a design decision and the trade-off was apparently worth it.

For anyone simulating passive crossovers, it looks to me like the best thing to do will be to make sure you have the appropriate vertical offset for your woofer and tweeter, but don't include a z offset, because that's apparently captured in the files.

Someone please correct me if I'm mistaken.
 

ctrl

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The z offset was apparently already accounted for in the files (even though the Y offsets weren't... which is a strange inconsistency and makes me concerned that everything may not be fully understood by all involved, myself included).
In principle, everything is correct so far. Since this is the first time Amir has measured individual drivers for a loudspeaker design, there are a few uncertainties in the data.

It seems that Amir set the NFS so that the reference point for tweeter and woofer was the center of the driver for both measurements.

Therefore, in VCAD, the driver spacing of tweeter and woofer must be entered for the y-axis. We have chosen the center of the tweeter as the listening reference axis. Therefore, the y-value for the tweeter remains 0 in VCAD, and -145mm is entered for the woofer.
1634322172513.png
With the measurement method described above, it is crucial that the distance to the baffle (z-direction) does not change when the microphone is set once at the height of the tweeter and once at the height of the woofer. Therefore, the relative z-axis offset of the sound origins of tweeter and woofer is already included in the measurement (but the y-axis offset not).

Amir is not sure whether he has entered the selected reference points in the Klippel NFS in the z-direction with millimeter precision.
This is still a small uncertainty until someone has either built the first passive crossover or has checked via measurements that the 52µs delay set for the active version corresponds to reality.
 

TimVG

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In principle, everything is correct so far. Since this is the first time Amir has measured individual drivers for a loudspeaker design, there are a few uncertainties in the data.

It seems that Amir set the NFS so that the reference point for tweeter and woofer was the center of the driver for both measurements.

Therefore, in VCAD, the driver spacing of tweeter and woofer must be entered for the y-axis. We have chosen the center of the tweeter as the listening reference axis. Therefore, the y-value for the tweeter remains 0 in VCAD, and -145mm is entered for the woofer.
View attachment 159239
With the measurement method described above, it is crucial that the distance to the baffle (z-direction) does not change when the microphone is set once at the height of the tweeter and once at the height of the woofer. Therefore, the relative z-axis offset of the sound origins of tweeter and woofer is already included in the measurement (but the y-axis offset not).

Amir is not sure whether he has entered the selected reference points in the Klippel NFS in the z-direction with millimeter precision.
This is still a small uncertainty until someone has either built the first passive crossover or has checked via measurements that the 52µs delay set for the active version corresponds to reality.

So if you wanted to design the listening axis to be exactly between the two voice coils you'd set the Y axis to plus and minus 72,5mm on each drive unit, correct?
 
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ctrl

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So if you wanted to design the listening axis to be exactly between the two voice coils you'd set the Y axis to -72,5mm on both drive units, correct?
-72.5mm woofer, +72.5mm tweeter
 

TimVG

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-72.5mm woofer, +72.5mm tweeter
Yeah I corrected probably as you were typing :)

Because it seems to me that depending on the listening distance (as you move closer and further to and from the speaker), designing on the tweeter axis will cause phase differences as the relative distance between your ear and both drive units isn't consistent.
 

McFly

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I don’t know why the tweeter is the design axis, to me it makes much more sense to design in the vocal region so in this case, the woofer mid bass
 

TimVG

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I don’t know why the tweeter is the design axis, to me it makes much more sense to design in the vocal region so in this case, the woofer mid bass

lol - that's not how it works.
 
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