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Introducing Directiva - An ASR open source platform speaker project

fluid

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are we reading the same review?

Because the THD graph is missing

View attachment 157625

But the parting thoughts say this
Yes audioexpress says the same except they calculated 7.2mm

"Displacement limiting numbers calculated by the Klippel analyzer using the full-range woofer criteria for Bl was XBl @ 82% (Bl dropping to 82% of its maximum value) equal to 10.2mm for the prescribed 10% distortion level. For the compliance, XC @ 75% Cms minimum was only 7.2mm, which means that for the Purifi PTT6.5X woofer, the compliance is the more limiting factor for getting to the 10% distortion level. However, if we use the less conservative 20% distortion criteria, XBl @ 70% = 11.7mm and XC @ 50% = 9.7mm, showing the Cms number closer to the driver’s physical Xmax."

When you limit the driver to 100Hz or 70 Hz it would probably hit thermal limits before distortion. But these are long throw drivers designed to be used low. The scanspeak is not.
 

abdo123

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Yes audioexpress says the same except they calculated 7.2mm

that's exactly the maximum excursion that would be used with 250W + BW12 @ 80Hz electric filter. seems like a match made in heaven between the Hypex F253 and this driver.
 
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Rick Sykora

Rick Sykora

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@abdo123 your proposed project is very interesting, but (at the very least) for better organization, suggest you move to its own thread.

If you want to do in the context of Directiva, can assign it a r number?

Thanks,

Rick
 
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Rick Sykora

Rick Sykora

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Rick - Earlier you tiptoed around a possible doubling of the passive (SB 5x8) radiators, would you target a box vol. of 22L? would this be necessary for higher SPL at lower freq? (not more extension) to avoid the passives reaching xmech?

I recall pondering the dual Purifi PRs in the truncated cabinet. It had some (likely) midrange leakage issues so that is why I abandoned it.

The hificompass folks do this in a cabinet that is 50% larger than Directiva r1. They have a brace that keeps woofer back waves from hitting the PRs directly. Given how much smoothing they use, not sure I can trust what I see, but they do seem knowledgeable. OTOH, we have the March Audio speaker using 2 PR's in a smaller cabinet.

Neither the VCAD sims or Amir's testing suggest the PR maxes out. However, there is indication that he may have encountered the woofer hitting its bounds. I will explore further once I have 2 speakers here together. :cool:
 
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Rick Sykora

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Btw, once I am done with stereo voicing and another round of spins, am done with r1. If you want a sealed version or lower crossover point, have at it. If requested, I will try to help, but otherwise my efforts are focused on r2 going forward. :cool:

Edit: should have mentioned a passive crossover, but this is gathering stream, so only may have to pick one!
 
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Rick Sykora

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Amir’s speaker arrived today and so was able to verify the woofer diffs that we discovered as we designed. Swapped in a newer woofer and matches much more closely. Before any critical stereo listening, will need to spend some time matching the 2 speakers closely.

Will share some pics in the morning. :cool:
 
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Rick Sykora

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Here are the plots...

1634133441823.png


took a little tweeter matching to do, but now have a pretty good match between the speaker pair!
 
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chych7

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Please tell me some double blind tests are planned with some known speaker models (maybe throw some Revels in there). It would be great to see how well objective measurements (and designing speakers with respect to optimizing metrics associated with those measurements) correlate to subjective evaluations, which IMO would ultimately validate the method and importance of going through all this effort to measure speakers so comprehensively.
 

fluid

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Can you educate a newbie? What is tweeter matching?

thx
Matching tweeters or drivers would be to pick drivers that have the most similar response to each other when measured out of the box or equalising them to measure close to each other to ensure good channel matching between speakers.
 

Paweł L

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Here are the plots...

View attachment 158775

took a little tweeter matching to do, but now have a pretty good match between the speaker pair!
This is just unbelievably beautiful, I think the industry standard is around +/-0.75dB for tight match, or something like that. Holly father of decibels, I wish other sets were like this (mine aren't). Rick, did you do some DSP correction for left and right channels or the drivers really measure that close.
 
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Rick Sykora

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This is just unbelievably beautiful, I think the industry standard is around +/-0.75dB for tight match, or something like that. Holly father of decibels, I wish other sets were like this (mine aren't). Rick, did you do some DSP correction for left and right channels or the drivers really measure that close.

No, just worked with the limited set of drivers I have 4 woofer and 4 tweeters. No addition eq was done, but suspect there may be need at times...
 
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Rick Sykora

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Wedding is over and house guests are gone. Still recovering from too much food and drink, but managed to get the stereo configuration working. After turning stereo back on and ensuring left was left, gave a quick listen with some of my music and some of Amir's. I have yet to listen to test tracks critically, but have been very pleased overall. Still have a lot more listening to do, but got in a solid round of listening to bass heavy tracks and some classical to test dynamic range...

In both cases, I did not hear any signs of strain at fairly high listening levels. My classical listening was mainly Mozart symphonies and Tchaikovsky's Capriccio Italien (Telarc CD with the 1812 Overture). The speaker are well out into the room, but still got a sense of "being there". The bigger swells in the symphonic pieces had nice heft. Just shy of much larger speakers I have owned/heard. My room is about 60 cubic meters and am listening about 4 m away. The dynamics on Claire Martin's Too Much In Love To Care (from Amir's playlist) were as impressive as are her vocals are lush.

Am pretty sure the sound could be even better if I move to better equipment. For now, was just using the DAC in the minidsp HD. As I have reduced the electronics in the chain, the hiss has gone to barely perceptible. After all has settled down with crossover tweaks, I plan to build a hybrid pair and (hopefully) eliminate the hiss entirely. These speakers final destination will be a smaller room with close LP, so need to drive his levels way down. :cool:
 
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D!sco

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I'd love to know what kind of levels you're seeing with a stereo pair in-room, and what hits it's limit first; the PR or the power handling.
 
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Rick Sykora

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I'd love to know what kind of levels you're seeing with a stereo pair in-room, and what hits it's limit first; the PR or the power handling.

As design and room sims handle this well enough, do not plan to drive speakers to these levels. It not only helps preserve drivers and my hearing, it makes for happier neighbors too.
 
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Rick Sykora

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Despite my quasi-anechoic measure being a bit bright, I measured again once the speakers were in listening position and they are much flatter.

I have been listening to them for most of the week and am pleased to report that I do not have any further crossover changes to make.

My next step for r1 will be to do a hybrid crossover. Will also test the passive one and if it checks out, post it too. :)
 
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Rick Sykora

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A quick update on r2 for those who may be interested....

The team is mainly focused on the monitor part of the r2 speaker. Once we settle on what is needed there, fitting a bass module to it should be more straightforward. The monitor module is targeted to be smaller than r1 and use a less expensive midwoofer.

To improve directivity into the lower midrange, the approach from the Dutch and Dutch 8C is being simulated. This cabinet alignment is more art at this point, so more sims and fine tuning are needed. Our target here is also to allow the monitor to be more flexible room placement. To improve the upper end directivity, we have looked at several approaches, but the current leader involves a graduated round-over by the tweeter. This would likely require a more skill than most builders might want to tackle, so we are working with local shops to prototype (and possibly supply).

The r2 monitor crossover design is more focused on a passive implementation. This has also helped constrain the midbass driver choice as we want to avoid ones with major high frequency ringing. So, this should yield a monitor that is more desirable for use with subwoofers. :cool:
 
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sarumbear

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A quick update on r2 for those who may be interested....

The team is mainly focused on the monitor part of the r2 speaker. Once we settle on what is needed there, fitting a bass module to it should be more straightforward. The monitor module is targeted to be smaller than r1 and use a less expensive midwoofer.

To improve directivity into the lower midrange, the approach from the Dutch and Dutch 8C is being simulated. This cabinet alignment is more art at this point, so more sims and fine tuning are needed. Our target here is also to allow the monitor to be more flexible room placement. To improve the upper end directivity, we have looked at several approaches, but the current leader involves a graduated round-over by the tweeter. This would likely require a more skill than most builders might want to tackle, so we are working with local shops to prototype (and possibly supply).

The r2 monitor crossover design is more focused on a passive implementation. This has also helped constrain the midbass driverr choice as we want to avoid ones with high frequency ringing. So, this should yield a monitor that is more desirable for use with subwoofers. :cool:
Strange differentiation of the words speaker and monitor…
 
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Rick Sykora

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Just wanted to share another update on r2 progress…

After many simulations, the team is at the point of actually starting to build a prototype to evaluate. One major challenge is how to improve directivity and still have a design that is easy to build. In r1, the choice was made to compromise towards the flat pack cabinet. While this is still an r2 option, we have iterated on improving beyond a rectangular box. A key takeaway for me is how important baffle shape is and now have a better appreciation for tradeoffs that are made for mass market products.

We have tried straight bevels, curved bevels and even reconsidered waveguides. The optimized design is currently like the Salk Veracity monitor, but much smaller. In fact, it is considerably smaller than r1 rn. This is another key design choice towards subsystem optimization as low end will be handled in the bass module. We are starting to get more serious about a bass module design, but is still being brainstormed at this time. It has a more known set of constraints, so expect it will come together much more rapidly.

Availability issues remain a nagging challenge. One waveguide candidate had lead times into March and the few that could be found were commanding more than twice the previous price. Even the current midwoofer was in low supply at a major distributor here. Ofc, hoping the latest covid variant does not hamper people or parts, but will see…

Overall am very pleased with the progress and results to date. The team has collaborated well considering we are quite geographically spread apart. This has been mainly been due to @ctrl’s ongoing generous efforts to simulate the initial designs for the team to evaluate. As you will soon see, we are still trying to wrap up r1 plans. Notably, firming up a passive crossover design has been delayed as I have been distracted by recent holiday tasks and car and computer problems. :eek: All that is fixed now and am back to full speed!

Stay safe and healthy and look forward to more Directiva progress.

Best wishes,

Rick and the r2 team
 
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