Introducing Directiva - An ASR open source platform speaker project

[Rick Sykora]

Am wrapping up and preparing to send the first Directiva speaker to Amir next week.

I appreciate his effort to help here, but do not expect him to spend much time with multiple listening tests. He is simply too busy to devote much time to one effort. We are working towards how we can simulate and do measurements that allow us to pick the optimal crossover for r1. Then as he will have the speaker in hand, can send him that minidsp configuration for a full review.

 

[Lbstyling]

Really exited for you guys. 99% don't get their projects through to the end like this and certainly not with the adherence to measurable parameters like this. Your trade offs in design show a real wealth of experience.

I think your team has a prosperous future ahead if you so choose to pursue one.

I'm currently intrigued by Dr Geddes recent interview on Erin's YouTube channel....7th order distortion audible at incredibly low levels....I wonder if this will feed into Amir's tests at some point. One of the notable features of your purifi driver is the low high order distortion.... Could be interesting if the subjective evaluations of that driver is connected to this.

Just thinking out loud.

 

[Rick Sykora]

Shipped to Amir! He will have early next week. Need to check when he can get to it as I need to build another...

May take him a while as I recall he has built a backlog. Directiva r1 should be a lot more interesting than another budget 2-way so hope he can give it some priority!

 

[tktran303]

The Purifi woofer has virtually NO higher order harmonics. 2nd, 3rd, 5th are visible around -55-65dB down but 4, 6, 7, 8th or higher are even further down.
Like -80dB down…

I’ve taken measurements and they are consistent with HifiCompass…

 

[McFly]

Shipped to Amir! He will have early next week. Need to check when he can get to it as I need to build another...m

May take him a while as I recall he has built a backlog. Directiva r1 should be a lot more interesting than another budget 2-way so hope he can give it some priority!

Nice work! I love DIY.

Just for those that havent read 27 pages, the specs so far are? Woof, tweet, volume, alignment etc (or perhaps edit post #1 with updates for new readers?)

 

[ctrl]

In the thread on the Genelec 8351B, concerns were raised about the width of the Directiva-Custom's soundstage.

I fear you’ll have a even smaller soundstage on the Directiva project developed by Rick & Ctrl:
Sound Power DI of 5dB at 650Hz and 9dB at 4500Hz...
But I‘m hoping their calculation is wrong, can’t believe that it is right, the Purifi woofer is not that directional, here is the SPK5 (Purifi plays up to like 3000Hz if I recall)

Therefore, here is the comparison of the Purifi-Celuaris with the simulation of the Directiva-Custom ([email protected]).

Listening window, sound power and DI are compared.

To make the comparison a bit fairer, the curves of the Celuaris in the diagram were smoothed with 1/3 dB/oct.

The curves for the Directiva-Custom are simulations which will deviate significantly from reality above 7kHz in the axis frequency response, therefore the DI may only be assumed to be realistic up to 7kHz.

Of course, the simulation can only be as good as the data available (the dimensions of the Purifi driver Rick sent me) and things like break-up modes are not included in the simulation.

The comparison shows that the expected width of the soundstage up to 2-3kHz should be comparable to that of the Celuaris (same woofer, comparable baffle) - assume that the overall soundstage will be more uniform than that of the Celuaris.

 

[MZKM]

In the thread on the Genelec 8351B, concerns were raised about the width of the Directiva-Custom's soundstage.



Therefore, here is the comparison of the Purifi-Celuaris with the simulation of the Directiva-Custom ([email protected]).
View attachment 130059 View attachment 130054

To make the comparison a bit fairer, the curves of the Celuaris in the diagram were smoothed with 1/3 dB/oct.

The curves for the Directiva-Custom are simulations which will deviate significantly from reality above 7kHz in the axis frequency response, therefore the DI may only be assumed to be realistic up to 7kHz.

View attachment 130052

Of course, the simulation can only be as good as the data available (the dimensions of the Purifi driver Rick sent me) and things like break-up modes are not included in the simulation.

The comparison shows that the expected width of the soundstage up to 2-3kHz should be comparable to that of the Celuaris (same woofer, comparable baffle) - assume that the overall soundstage will be more uniform than that of the Celuaris.

That is using the pyramid cabinet, is it not? What about the rectangular one being sent to Amir?
Apologies if I’m getting anything wrong, this is a large thread to keep up with.

 

[ctrl]

That is using the pyramid cabinet, is it not? What about the rectangular one being sent to Amir?
Apologies if I’m getting anything wrong, this is a large thread to keep up with.

Yep, that was the simulation for the Directiva-Custom. But it's no problem to make the same comparison for the Directiva-Stock (Directiva with the Partsexpress finished cabinet).


Here is the comparison of the Purifi-Celuaris with the simulation of the Directiva-Stock ([email protected]).

Listening window, sound power and DI are compared.

For all the details regarding the simulation and its validity, see my post on the Directiva custom above.

 

[Rick Sykora]

Thanks @ctrl for sharing some more of the current Directiva design assumptions and detail.

So, LOL is there really a posting comparing a simulated Directiva prototype to a Genelec 8351B? If so, you get the credit and if it flops, I will take the blame!

As for some general expectation management, my goal was to develop a decent active 2-way DIY speaker for much less than you would buy from a respected brand name. My hope is that Directiva r1 (the one that Amir is about to help measure), is a good step towards that goal. But anything more is quite premature in my opinion. As we are still at the design stage in this iteration of the project, and we still have much to do. I would encourage everyone to be patient and wait for real measurements and their integration into the r1 speaker design. Thanks!

 

[MZKM]

Yep, that was the simulation for the Directiva-Custom. But it's no problem to make the same comparison for the Directiva-Stock (Directiva with the Partsexpress finished cabinet).


Here is the comparison of the Purifi-Celuaris with the simulation of the Directiva-Stock ([email protected]).
View attachment 130071 View attachment 130070
Listening window, sound power and DI are compared.

For all the details regarding the simulation and its validity, see my post on the Directiva custom above.

View attachment 130067

Thanks, ok that DI is so much better than what was posted earlier:

 

[Rick Sykora]

Hi folks! While waiting for the speaker to be delivered to Amir, have been busy with some other projects including getting a tooth crowned and building a twin speaker. I changed my router bit from the big roundover bit back to a cutting bit and the jasper jig. I now have a matching front baffle but did not come as smoothly as I normally expect.

Am going to start a build thread for those who are interested in those travails. Will explain more there and will share some tips for when the cuts do not turn out as expected. My new router is smooth but the depth gauge is not very precise. So, if you recut a hole, you either need to create a jig or another trick using a rabbeting bit. See the build thread for more on this.

 

[abdo123]

@Rick Sykora

Would it be possible to make a design out of plastic? so everyone can just 3D print it around the world with ease?

it could revolutionize the way we know and make DIY speakers.

 

[Rick Sykora]

@Rick Sykora

Would it be possible to make a design out of plastic? so everyone can just 3D print it around the world with ease?

it could revolutionize the way we know and make DIY speakers.

While I get the basic process, not sure about its current feasibility. Agree it opens up design potentials that go beyond the traditional approach to enclosures though. Clearly some are already using for smaller parts (like ports, waveguides, etc.).

Seems worthy of a separate exploratory thread in its own right.

 

[somebodyelse]

Feasibility depends on the tools and skills you have, or are willing to acquire. If you're regularly 3D printing things but don't do woodworking then modeling the eventual enclosure design and splitting it up into blocks to fit your printer may be the better option. That's more or less what was done to compare nominally identical cabinets of various woods and a couple of different fill densities of 3D print in another video from the same person. Short version: with the heavier perimeter and infill the mass and measured response of the printed one is very similar to the wood ones. It doesn't exploit the full potential of 3D printed cabinets, but it shows it's a viable alternative to wood with broadly comparable performance.

 

[ctrl]

So, there's been a lot going on behind the scenes.
@Rick Sykora has described the construction of the Directiva-Stock variant in the neighboring thread and @amirm has measured the single drivers of the Directiva-Stock speaker cabinet with the Klippel NFS.
Rick has documented part of the result here.

I would like to discuss here how the results of the real measurements of the Directiva compare to the simulation and whether the hype about simulations is justified.


We compared the simulation of the Directiva with a [email protected] crossover (named 12c in the diagrams), with the same crossover based on the real measurements (with a 1/6 oct smoothing, normalized on-axis):

As mentioned in previous posts, the simulation for tweeters usually deviates significantly above 8kHz, because the simulation simulates an ideal driver and does not take into account any breakup modes (the same applies to the simulation of the woofer, but the deviations begin much earlier).
With the SeasDXT, there is also the fact that the waveguide has to be simulated as well.

The frequency responses of the simulation deviate "upwards" above 6 kHz.

However, the frequency range 200Hz to 8-10kHz (the low frequency range should be considered separately) is usually relevant for deciding whether a project is worth implementing. Therefore, let's take a detailed look at this frequency range:

At angles <60° the deviation in the frequency response of simulation and real loudspeaker up to 6.5kHz is mostly well below 1dB.

The results of even this "simple" simulation, are so good that the construction of prototypes (in most cases) is no longer needed.

 

[bigjacko]

because the simulation simulates an ideal driver and does not take into account any breakup modes

Is it possible to use existing frequency response to do simulation rather than assume ideal driver?

 

[ctrl]

Is it possible to use existing frequency response to do simulation rather than assume ideal driver?

Not that I know of. You would also need several frequency response measurements at different angles and interpolate the missing angles, then maybe you could "somehow" convolve the ideal FR with the FR measured in the infinite baffle.

 

[tktran303]

Is it possible to use existing frequency response to do simulation rather than assume ideal driver?

you mean for the woofer or the tweeter?

for the standard cone woofer and dome tweeter Yes you can.

VituixCAD2 can do this, from -90 degrees to +90 (or even wider, I forget)
But at the moment it can only assume a flat faceplate like a standard baffle or standard tweeter. It can also simulate measuring distance and baffle round over.

of course it’s not good as using a turntable, but it gets you close enough to do crossover sim.

the DXT’s unique faceplate can’t be simulated using standard crossover designers, perhaps in Comsol or other FEM tool.

 

[Rick Sykora]

What was the resonance issue? Currently in the testing phase of my own turntable and am curious where to look for problems.

The issue was the mic holder. It was loose and I also flipped it around. Mine is spring loaded, so had already added some foam tape where it holds the mic. Hope this helps!

 

[Selah Audio]

Lol, no but would need @amirm to explain...

You are correct about Purezza comparison. Without a crossover, Directiva r1 bass subsystem should be almost identical performance to Purezza. Expect Directiva to be better or equal depending on crossover implementation. Once I get the speaker back together, will get a better read on a more accurate sensitivity value.

How will it be better?