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Introducing Directiva - An ASR open source platform speaker project

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Rick Sykora

Rick Sykora

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Just bought another minidsp 2x4hd for work on Directiva r2. I had planned to buy an SHD a while ago, but had skipped due to lack of bass management feature. However, I see Dirac 3 has resolved this now. Still need to work out how many channels I need, but for a $200 upgrade can go to the DDRC-24 and get Dirac 3.

There is a pretty good thread on this already and @abdo123 has shared some of his experience with the DDRC-24. So is now another item on my todo list to explore this option for Directiva. Seems like a great way to get ARC into a simple stereo setup.
 

abdo123

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Just bought another minidsp 2x4hd for work on Directiva r2. I had planned to buy an SHD a while ago, but had skipped due to lack of bass management feature. However, I see Dirac 3 has resolved this now. Still need to work out how many channels I need, but for a $200 upgrade can go to the DDRC-24 and get Dirac 3.

There is a pretty good thread on this already and @abdo123 has shared some of his experience with the DDRC-24. So is now another item on my todo list to explore this option for Directiva. Seems like a great way to get ARC into a simple stereo setup.
Keep in mind that once you upgrade to the DDRC-24 the input PEQ will be locked out, and so are the FIR filtering capabilities.

Depending on your crossover design / approach this might be a big issue, some crossovers have input / global EQ, this shouldn't be an issue with the R1's current crossover though, just something to keep in mind.

This is the case for all Dirac capable MiniDSP devices btw, so it includes the SHD.
 

mdsimon2

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Just bought another minidsp 2x4hd for work on Directiva r2. I had planned to buy an SHD a while ago, but had skipped due to lack of bass management feature. However, I see Dirac 3 has resolved this now. Still need to work out how many channels I need, but for a $200 upgrade can go to the DDRC-24 and get Dirac 3.

There is a pretty good thread on this already and @abdo123 has shared some of his experience with the DDRC-24. So is now another item on my todo list to explore this option for Directiva. Seems like a great way to get ARC into a simple stereo setup.

What do you mean by lack of bass management? I did not see any change in ability to implement a routing matrix or crossovers when upgrading from Dirac 2 to 3 with my DDRC-24 or my SHD Studio. Of course no miniDSP product has Dirac Live Bass Control.

Michael
 
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Rick Sykora

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What do you mean by lack of bass management? I did not see any change in ability to implement a routing matrix or crossovers when upgrading from Dirac 2 to 3 with my DDRC-24 or my SHD Studio. Of course no miniDSP product has Dirac Live Bass Control.

Michael

Thanks, may have misread then. Which Dirac feature allows multiple subwoofers?
 

mdsimon2

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Thanks, may have misread then. Which Dirac feature allows multiple subwoofers?

Only the DDRC-88A and 88D allow for multichannel Dirac correction, all other miniDSP products only offer stereo Dirac correction. None of them offer any sort of automated sub / main integration. In principle I do not think this is a big deal, just requires a bit more fiddling around to get the x-over right before applying Dirac.

Michael
 
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Rick Sykora

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Only the DDRC-88A and 88D allow for multichannel Dirac correction, all other miniDSP products only offer stereo Dirac correction. None of them offer any sort of automated sub / main integration. In principle I do not think this is a big deal, just requires a bit more fiddling around to get the x-over right before applying Dirac.

Michael
Have not found what I read previously and dirac website is not much help.

This minidsp app note states you can do 4: https://www.minidsp.com/applications/subwoofer-tuning/ddrc24-multisub

So, seems you could do a 2.2 system with a ddrc-24 or am I missing something? :confused:
 

Jdunk54nl

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Have not found what I read previously and dirac website is not much help.

This minidsp app note states you can do 4: https://www.minidsp.com/applications/subwoofer-tuning/ddrc24-multisub

So, seems you could do a 2.2 system with a ddrc-24 or am I missing something? :confused:
Also this article listed on the 2x4hd to ddrc-24 upgrade page: https://www.minidsp.com/products/dirac-series/2x4hd-to-ddrc-24
It does state Full range correction too.

This is the article:
 
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mdsimon2

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Have not found what I read previously and dirac website is not much help.

This minidsp app note states you can do 4: https://www.minidsp.com/applications/subwoofer-tuning/ddrc24-multisub

So, seems you could do a 2.2 system with a ddrc-24 or am I missing something? :confused:

Of course the DDRC-24 has 4 outputs so you can hook up 4 subs to it, however Dirac is applied on the input before the routing matrix so it can only independently correct 2 channels.

1639071248627.png


In the tutorial you linked they are summing the left and right signals in the routing matrix which will ensure that each sub receives the same Dirac correction which is probably not what you want when managing multiple subs.

1639071332365.png


Again you can use the DDRC-24 in a 2.2 system but you will need to set the crossovers manually before running Dirac and it is not possible to correct the sub independently from the mains.

Michael
 
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Rick Sykora

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Hi Rick,

I have a vague recollection of a technique using a woofer as a PR, with a resonant circuit between the otherwise-unconnected woofer terminals. That approach might be able to reduce that 400Hz resonance (or whatever it might be with a different passive radiator).

Just getting around to trying your suggestion. The woofers were inexpensive enough and do have to add about 25g of mass to get them have an Fs close to the passive radiator, but with diff resistance values, the tuning frequencies do not change much, but to no huge surprise, the magnitude of the impedance peaks do. Shorting the woofer yields single resonance, much like a sealed enclosure.

Will share some more another thread as this may have some interest beyond Directiva.

Thanks for sharing!
 

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Have the new Dayton Epiques been considered as an affordable alternative to the Purifi drivers?
 
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Rick Sykora

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Have the new Dayton Epiques been considered as an affordable alternative to the Purifi drivers?

Yes, but most any substitute driver is a pretty much a redesign. The GF180-4 may be an easier substitute. There are some other decent SB drivers that might match better to the passive radiator (Including its matching woofer). The matching woofer needs more volume to go as low as the Purifi though.

Otherwise, if you plan to use with a subwoofer, suggest you wait for the r2 monitor. It should be less expensive and have better directivity than r1.

Hope this helps!

Rick
 

muad

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Rick,

Any general idea of the size and layout of the bass module?

What drivers are you thinking of?
 
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Rick Sykora

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Rick,

Any general idea of the size and layout of the bass module?

What drivers are you thinking of?

Just conceptually at this point. Am waiting on the monitor module to be closer to final. I anticipate there may be a couple of bass modules. As mentioned earlier, foresee one as a slim tower to match the monitor. Ofc, this tends to limit the size of the woofer used. The other unit would be wider to allow for larger drivers to be used.

To allow for greater design flexibility, have loosened the slim version requirements to allow the bass module design to be vented or other than sealed. This also opens up the possibility for enough bass output to have a passive crossover as an alternative to an active design. :cool:
 

changer

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As luck would have it, I have a simulation of a 170mm waveguide on my hard drive - comparable to the one you used.

First, let's look at the waveguide in infinite baffle (normalized on-axis sonogram):
View attachment 158296
The directivity at smaller angles looks a bit strange, this is because the waveguide was designed for a specific baffle width.
So if you are right, then the frequency response should not change when installed in a loudspeaker cabinet as long as the waveguide controls the radiation.
In our example the -6dB limit is drawn in black and up to 2.7kHz the Waveguide seems to control the radiation.

If the baffle and speaker enclosure have little effect, then there should be virtually no change above 2.7kHz when installed in a speaker enclosure (horizontal, normalized on-axis sonogram):
View attachment 158298
As expected, the control of the waveguide increases to lower frequencies due to the interaction with the loudspeaker cabinet. The radiation is now controlled down to about 1.3kHz.
But what is also noticeable is that in the frequency range 2.7-7kHz the frequency response curves have also changed significantly for small angles.

You can see this a little better if you look at the frequency responses in direct comparison (IB=infinite baffle, LS=loudspeaker cabinet, horizontal, normalized on-axis sonogram):
View attachment 158313


Hence the difference in horizontal directivity between the normal and the optimized version of the Directiva cabinet shown in post446.​
Dear ctrl,
I have been preparing a waveguide to be 3D printed for my DIY two-way speaker. I have attached some illustrations and analyses. Yet, until now the waveguide, which was calculated with Marcel Batík's ath software, was always simulated on an infinite baffle. This is due to the software output, which is setting up the perimeters for the waveguide and creating an output readable by ABEC. It can then be calculated and further analyzed with VACS. After I saw your above post from the review thread, I wanted to ask you if you could tell me what I need to do to simulate an enclosure! This is not a feature of the software and I need to learn how to do this by hand in ABEC/AKABAK. As I do not have a 3D printer myself, and have to rely on helping hands, I do not want to ask my friends for too many iterations of the piece until it works as intended. It would be good to simulate this waveguide in its enclosure (60 cm × 31 cm × 27.5 cm H × W × D, with 37 mm roundover on the vertical front edges) to see what happens to its dispersion pattern. Is there an accessible way to start with and can you give me a hint, how I can do this?

front.jpgprofile h.jpgprofile v.jpgsono.pngspl.png
 
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ctrl

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Is there an accessible way to start with and can you give me a hint, how I can do this?

I have described a "simple" way in the software-tool thread. Download the file ABEC_Template.zip. This is a parameterized loudspeaker template.

You must then adapt the scripts so far (e.g. remove the shell-element based waveguide) that you can insert the script generated by ath (after adaptations) or you must rebuild the result of ath with other means of ABEC.
 
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Rick Sykora

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@Rick Sykora any updates or sneak peeks on the r2 ? :p

Yes, thanks for asking. We have had some promising results from the first prototype and am just about to share.

Hopefully will do later this evening, but am making homemade pizza for dinner and need to go chop some veggies. :)
 

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Yes, thanks for asking. We have had some promising results from the first prototype and am just about to share.

Hopefully will do later this evening, but am making homemade pizza for dinner and need to go chop some veggies. :)
Yum! Thanks for taking the time to comment! Looking forward for the update.
 
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Rick Sykora

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As promised, here is an r2 update...

First of all, let me say that most of the work was done by @TimVG and @ctrl. Other team members helped with driver selection and my main role was to rebalance requirements as needed. I anticipate they may add some commentary to this post, but both are very busy with other projects rn. So the first target was to design a small monitor with better directivity than r1 and at a lower cost. Am pleased to say, we meet this goal with one noteworthy exception. We had hoped that we could get enough bass extension to use with a subwoofer, but fell back to needing to pair with the planned bass module. We plan to revisit a derivative monitor design with lower bass extension later.

I had mentioned that simulations indicated a need to narrow the baffle to get better directivity, so we went with a simple shape that is like a small Salk Veracity. To push constant directivity even lower in frequency, we decided to use the approach used by the Dutch & Dutch 8C. @TimVG had some experience with the approach and @ctrl did several sim iterations to refine. Once this was done, Tim had gotten a CNC and decided he wanted to deploy it to build the prototype. His design takes the original shape and rounds off the top. So, it is reminiscent of a mantel clock as show here...

index.php


The tweeter as expected is the Seas DXT and the woofer is a SB15NBAC30-8 midwoofer. The SB was chosen as a balance of size and price/performance. Here is a look at the normalized horizontal directivity:

as
index.php

As you can see, the prototype exhibits fairly constant directivity well below 1 kHz.

And here is a preview of the frequency response with an initial crossover:

index.php


While some aspects may still change, will know better once I build the less rounded cabinet and we test it. Like my r1 measurement system upgrade, Tim is in the process of upgrading his. I will start as soon as I wrap up the passive crossover for r1 (hopefully this week).

Cheers!

Rick and the Directiva r2 team.
 
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