Directiva r2 monitor prototype build

[jcr159]

After some redesign for proper center axis, here is the latest…

View attachment 192001

Now that the speaker plaform is so small, am redoing the wiring too. Have to ensure there is minimal stress on the speakon connector. Also considering attaching speaker directly to top plate.

Looks as thoughtful as the Directiva design! Nice work Rick!

Maybe on v2, you can mount the pipe to the bottom plate on some under mount drawer slides…. You could then fine tune the center point for future use! Or some kind of worm gear driven plate with 2 axis control.

 

[Rick Sykora]

So you making some LXMini's!

Always wanted to build some, but only thing my effort shares is smart use of pipe.

 

[Rick Sykora]

Looks as thoughtful as the Directiva design! Nice work Rick!

Maybe on v2, you can mount the pipe to the bottom plate on some under mount drawer slides…. You could then fine tune the center point for future use! Or some kind of worm gear driven plate with 2 axis control.

Looks like you have big plans for me!

My initial reaction was it probably not be worth the effort but do have some very nice drawer slides around. Am not sure about the stability and would need a locking mechanism but will keep it in mind. I did buy a couple more flanges as can foresee a need for a larger upper plate.

Should be giving the new stand a test drive later today. Will see how it works out. An indexing table would be handy, but would rather spend the money on driver rn.

 

[Rick Sykora]

My first full day with the new test rig was frustrating. Every time I thought I had everything aligned perfectly, one of the extreme angle measures would go awry. Found REW defaults to IR peak (thanks @napilopez) and thought that was the issue, but had it happen again after I changed the setting.

Still troubleshooting this morning. Need to get it very accurate so know we can reliably compare different bass alignments. Stay tuned!

 

[napilopez]

My first full day with the new test rig was frustrating. Every time I thought I had everything aligned perfectly, one of the extreme angle measures would go awry. Found REW defaults to IR peak (thanks @napilopez) and thought that was the issue, but had it happen again after I changed the setting.

Still troubleshooting this morning. Need to get it very accurate so know we can reliably compare different bass alignments. Stay tuned!

Have you tried manually aligning the impulse response? Just sliding the start point until the data looks right? You should be able to do this after the fact

 

[Rick Sykora]

Have you tried manually aligning the impulse response? Just sliding the start point until the data looks right? You should be able to do this after the fact

May make for better looking FR graphs, but unless REW syncs on export or something, changing the ref point is prob going to mess up timing needed for proper crossover development.

 

[napilopez]

May make for better looking FR graphs, but unless REW syncs on export or something, changing the ref point is prob going to mess up timing needed for proper crossover development.

Not at my pc now but I do think that the settings should carry over on export

 

[mainframe]

My first full day with the new test rig was frustrating. Every time I thought I had everything aligned perfectly, one of the extreme angle measures would go awry. Found REW defaults to IR peak (thanks @napilopez) and thought that was the issue, but had it happen again after I changed the setting.

Still troubleshooting this morning. Need to get it very accurate so know we can reliably compare different bass alignments. Stay tuned!

Distance to walls from DUT/Mic? I had a similar problem, extreme angles 110-180 measurements were all crazy, turned out the distance from the DUT to the back wall was too short. Reflected sound more powerful than DUT sound. I suspect bass isn't as omnidirectional as convention would like us to believe.

 

[Rick Sykora]

Distance to walls from DUT/Mic? I had a similar problem, extreme angles 110-180 measurements were all crazy, turned out the distance from the DUT to the back wall was too short. Reflected sound more powerful than DUT sound. I suspect bass isn't as omnidirectional as convention would like us to believe.

Thanks, getting away from back walls is good advice. In my case, am already pretty far away.

Am still working on this but the ceiling in my room has an abrupt height change. The room is also fairly narrow. Going to move into a bigger room and try.

 

[Rick Sykora]

Not at my pc now but I do think that the settings should carry over on export

I looked at this a bit further and can see what you intended. Not sure why REW is not doing the same when asked to reset the IR delay. It is doing the reset, but not updating the FR graph.

Still need to understand what the ramifications are for crossover design, but time to consult with John.

 

[Rick Sykora]

Well the larger room made almost no difference...

Now that am pretty sure how to remediate (as per @napilopez suggestion above), am moving test rig back to our family room. REW is still not doing what I expect with IR start, but am working that issue with John Mulcahy.

 

[Rick Sykora]

First set of measurements of the sealed box are done and being analyzed by the Directiva team. Not sure whether will create a crossover rn or just go on to measure the slotted side panels. The weather here was unseasonably warm this past week and somehow managed to pick up a head cold. So, no critical listening for me.

Will post some measurements as soon as I get some secondary validation. A quick nearfield measure shows an f3 around 80 and an f10 in the mid 50s. This is in line with modeling by Madisound, but not sure how loud they will go. Does bode well for using them with a subwoofer.

 

[Rick Sykora]

Well my measurements do not match the sims as well as we think they should, so am blaming being sick. Some of it may be sims from one continent and measuring in another, but we are working through it. While am feeling better, still not up to full speed.

Will have to see what tomorrow brings...

 

[Rick Sykora]

Have been working on seeing if ARTA improves measurements, started some of the VCAD work. So here is a look at baffle diffraction...

 

[Rick Sykora]

...and here is the closed cabinet sim:

 

[Rick Sykora]

So dropped the hint about ARTA earlier and as it is part of why r2 progress has slowed, thought would share a little of why. Directiva r1 was essentially @ctrl and I. Along the way, I struggled with getting some kinks out of my test rig. Once those were resolved, that really only left us with 1 major disparity: alignment between @ctrl's sims and my (REW) measurements. In the end, we settled for close enough and the result turned out pretty well. In r2 the initial builds were done by @TimVG and his preliminary measurements were done with REW. Comparable issues with sims but Tim needed to upgrade his test rig and so I started the build for this thread and went back to using REW for design measurements.

If you followed this thread, you know we ran into issues with matching sims and measurements again. Even after refining my setup thoroughly, some significant disparities remained. @ctrl has been able to readily reconcile his sims and his measurements in the past, but his measurements were done with ARTA. After some discussion, I was convinced that ARTA could help make for more consistent measurements across the team. Also am hoping it might help improve the known sim discrepancies.

Tim and I are both starting to work with ARTA. So far, it has been a slow go for me as it is not as easy to use as REW. Tim is quickly catching up to me and, with @ctrl's assistance, we are hoping to improve our ability to share data across the team. So please excuse the delays but are working towards finding whether ARTA is better or just different. Once we have more definitive results, plan to share in a separate thread.

Thanks!

Rick

 

[julbo]

After some redesign for proper center axis, here is the latest…

View attachment 192001

Now that the speaker plaform is so small, am redoing the wiring too. Have to ensure there is minimal stress on the speakon connector. Also considering attaching speaker directly to top plate.

@Rick Sykora - do you fill it with sand or leave it be?
I'm thinking how I'll need to move it away if it's getting too heavy
Appreciate the fantastic effort, most likely I'll never stop learning here

 

[Rick Sykora]

@Rick Sykora - do you fill it with sand or leave it be?
I'm thinking how I'll need to move it away if it's getting too heavy
Appreciate the fantastic effort, most likely I'll never stop learning here

Since I swap various tubes for different speaker heights. am not filling them with anything. I do use a mat on top of the stand to help dissipate some vibration though.

If my test were lower frequency and higher levels, more damping might be needed. So far have not seen any evidence that it is needed.

 

[gnarly]

Enjoying this thread, thx.
A friend on DIY forums has done a lot of cardioid modeling but hasn't committed to a build yet...nice to see a build in play.

Hey, with regards to measurements...i'm not an expert, but i sure do make a lot of them building DIY speakers.
I use REW, ARTA, and SMAART (the most)....taking lots of multi-way polars on a spinorama outdoors, (and indoors in winter time).

REW and ARTA should give the same results, when excess delay, TOF (time of flight), is removed the same. If not, something is amiss.
Since you guys are working with John M, i'm sure all will sync up.

Afaict, all the FFT/DFT measurement programs find impulse peak the same way, the peak of the ETC energy-time curve (log view).
But that provides a confusing catch with the usual impulse response, the linear view (that shows polarity.)
Catch is that linear view gives one vote to each frequency towards finding impulse peak . Which overweight's high-freq response.
This is easily seen by the heights of impulse responses. 10k-20kHz is one octave and gets 10,000 votes. 100-200Hz is one octave and gets 100 votes.

In the case of the Purifi 6.5, looking at its raw response curve down to say -10 dB, i'd judgement call that bandwidth to be 60Hz to about 6 kHz.
Each single frequency in that bandwidth gets a strong vote towards where in time the linear impulse peak falls.
Which means roughly >3000 Hz equals influence of below 3000Hz.
So when the driver is rotated, and the relatively beaming upper end response of its response rolls off, the impulse peak looses its previous time bearing.
And as folks have noted, room reflections want to join the voting then.

The two workarounds i use for measuring drivers used below HF/VHF:
are measure outdoors, so reflections don't get a vote. (belaboring the obvious)

and put a temporary linear phase xover in place somewhere above the final intended xover frequency range.

The temporary xover works indoors too...it forces the measurement software to look for peak ETC energy in the range the driver will be used at....without influence from bandwidth that won't be used.
I use it outdoors as well, as it simply quicken and narrows the time alignment process.

I've come to realize time and phase alignment of a speaker, really mean time and phase alignments of the measurements I took of the speaker.
The closer i can get the raw measurement to reflect the actual passband that will eventually be in use, the less the fixed delay manipulation that goes into the xover.
Key i think, is getting a raw measurement of each driver section that has overall phase trace as flat as possible for the intended passband.

Hope all this is welcome...don't mean to be teaching/preaching/or anything remotely close.
Just want to maybe share some things that i've found helpful making measurements.
And nothing guaranteed. ymmv.

 

[Rick Sykora]

Enjoying this thread, thx.
A friend on DIY forums has done a lot of cardioid modeling but hasn't committed to a build yet...nice to see a build in play.

Hey, with regards to measurements...i'm not an expert, but i sure do make a lot of them building DIY speakers.
I use REW, ARTA, and SMAART (the most)....taking lots of multi-way polars on a spinorama outdoors, (and indoors in winter time).

REW and ARTA should give the same results, when excess delay, TOF (time of flight), is removed the same. If not, something is amiss.
Since you guys are working with John M, i'm sure all will sync up.

Afaict, all the FFT/DFT measurement programs find impulse peak the same way, the peak of the ETC energy-time curve (log view).
But that provides a confusing catch with the usual impulse response, the linear view (that shows polarity.)
Catch is that linear view gives one vote to each frequency towards finding impulse peak . Which overweight's high-freq response.
This is easily seen by the heights of impulse responses. 10k-20kHz is one octave and gets 10,000 votes. 100-200Hz is one octave and gets 100 votes.

In the case of the Purifi 6.5, looking at its raw response curve down to say -10 dB, i'd judgement call that bandwidth to be 60Hz to about 6 kHz.
Each single frequency in that bandwidth gets a strong vote towards where in time the linear impulse peak falls.
Which means roughly >3000 Hz equals influence of below 3000Hz.
So when the driver is rotated, and the relatively beaming upper end response of its response rolls off, the impulse peak looses its previous time bearing.
And as folks have noted, room reflections want to join the voting then.

The two workarounds i use for measuring drivers used below HF/VHF:
are measure outdoors, so reflections don't get a vote. (belaboring the obvious)

and put a temporary linear phase xover in place somewhere above the final intended xover frequency range.

The temporary xover works indoors too...it forces the measurement software to look for peak ETC energy in the range the driver will be used at....without influence from bandwidth that won't be used.
I use it outdoors as well, as it simply quicken and narrows the time alignment process.

I've come to realize time and phase alignment of a speaker, really mean time and phase alignments of the measurements I took of the speaker.
The closer i can get the raw measurement to reflect the actual passband that will eventually be in use, the less the fixed delay manipulation that goes into the xover.
Key i think, is getting a raw measurement of each driver section that has overall phase trace as flat as possible for the intended passband.

Hope all this is welcome...don't mean to be teaching/preaching/or anything remotely close.
Just want to maybe share some things that i've found helpful making measurements.
And nothing guaranteed. ymmv.

Thanks for sharing! Good to hear our experiences are comparable. I can see the advantage of outdoors and higher verticals, but unfortunately, my current location does not support year-round...

Fully agree on how unique measurements are to the individual tester. Until I had to share mine with others, life was a lot simpler. Am sure others in the Directiva team feel the same way. Pretty sure ARTA can improve consistency, but unless you get test rig conditions well-matched, comparing results still requires allowances for variability. Even spending serious money for a Klippel does not mean the operators set them up identically and we see variability there as well.

While I wait for other team members to sync up on ARTA, am sticking to REW for my other projects. For impedance measures, already have a box built and see no need to build the ARTA one. Hope everyone can appreciate the time required to improve!