Minerva Monitor: "Patience my ass, I'm going to go build something!"

[ergo]

I finally got all the parts, so now in next days onto thinking how to place and assemble these so that if it works it'll fit inside the box too.

[JonMarsh]

I finally got all the parts, so now in next days onto thinking how to place and assemble these so that if it works it'll fit inside the box too.

[ATTACH=CONFIG]25749[/ATTACH]

Super! :B :T

I just love seeing pictures of big piles of crossover parts.... and I know what you mean, some of mine have started arriving, and I'm going to try to have to make a layout that will work in some fashion in the based of the Translam build, as well as for the Minerva TS variant.

There's also an MR18REX on the way- and I am curious to see how it stacks up against the C18EN001 on the bench, and otherwise. For now I'll probably put it in the original test enclosure and give it a whirl there...

[JonMarsh]

No inductors yet, but I'm getting there... lots of shiny bits!

[John Monica]

Here's what you do with your driver cutouts.

http://sploid.gizmodo.com/handmade-bamboo-death-star-looks-better-than-the-real-t-1774659215

~May the 4th be with you.

[hyperducky]

Minerva Monitor: "Patience my ass, I'm going to go build something!"

Jon if I were to send you a test enclosure for measurements with the MR18REX/XF driver would you be willing to do the testing? I am interested in a narrower enclosure than the Minerva. And would love to see what that response would be and if it correlates with what I have modeled from the manufacturer's response on their website and the baffle response model in virtuix cad
-Aaron
Oh and may the fourth be with you

Sent from my iPhone using Tapatalk

[JonMarsh]

May the fourth be with you, too!

How narrow? Note, my original tests for the C18EN were for the PE 0.75 cu ft enclosure- I still have that around, and will first test the MR18REX with that- it's 10" wide. BTW, tracking shows it should arrive on Friday, so I do plan to look at it this weekend, and generate plots and FRD files and ZMA. You're welcome to them if it helps in your planning...

[Evil Twin]

Here's what you do with your driver cutouts.

http://sploid.gizmodo.com/handmade-bamboo-death-star-looks-better-than-the-real-t-1774659215

~May the 4th be with you.

Impressive.... most impressive! Now, the only thing that remains is to install a coaxial driver in place of the laser beam focus mirror...

Stephen Manning's next assignment will be to complete construction of the LBL Death Star... I am most certain we can find the ways to properly motivate him...

Then, the only task remaining will be to integrate a Seas L12RE into the Laser Focusing parabola- undoubtedly a trivial task for one as skilled as Stephen...

[Steve Manning]

Impressive.... most impressive! Now, the only thing that remains is to install a coaxial driver in place of the laser beam focus mirror...

Stephen Manning's next assignment will be to complete construction of the LBL Death Star... I am most certain we can find the ways to properly motivate him...

Then, the only task remaining will be to integrate a Seas L12RE into the Laser Focusing parabola- undoubtedly a trivial task for one as skilled as Stephen...

My purpose is to serve ...... so when does the 5 axis CNC router arrive? :B

[Evil Twin]

Should you need some guidance or suggestions in the necessary design and manufacturing technique, this video should answer some questions... perhaps even YOUR questions...

[JonMarsh]

Now, just imagine a couple of those hanging from your ceiling, with the coax driver pointed- hopefully- towards the main listening area?

Actually, I worked for a small speaker company in Boulder CO in the early 70's, one of the models we produced was a dodecahedron with 5" full range (Bose like) drivers mounted on each facet; they worked real well with a simple EQ box.

[flamethrower1]

No inductors yet, but I'm getting there... lots of shiny bits!

What flavour are the gold colored caps?

[JonMarsh]

Those are from Obligattor, sourced through Parts Connexion in Canada. Something of an experiment, they're the "Gold" series, non-resonant construction with non magnetic metal tube and heavy encapsulation, made with German sourced polypropylene film in China. Recommended by Tony Gee and others as good value, fairly high performance with reasonable prices. Construction is very similar to Jantzen Superior Z caps.

[flamethrower1]

Sweet, I was hoping that's what they were, I have been looking at those.
Have not purchased the caps for my uber build so it will be interesting to see what you find out.

Thanks, Greg

[hyperducky]

May the fourth be with you, too!

How narrow? Note, my original tests for the C18EN were for the PE 0.75 cu ft enclosure- I still have that around, and will first test the MR18REX with that- it's 10" wide. BTW, tracking shows it should arrive on Friday, so I do plan to look at it this weekend, and generate plots and FRD files and ZMA. You're welcome to them if it helps in your planning...

Jon I was going to go as narrow as possible. My model is at 9in with a 1/2in round over. The difference between the 10" and 9" baffles might be minimal. I'd definitely use the frd and Zma files.

Same width as the ansonica's since I'll use the anarchy drivers for the LF.

[JonMarsh]

Which version of the Anarchy's do you have? I've got a few of them stashed away somewhere- actually saw them a few weeks ago!

I should model them to see if they would work with any of the off the shelf PR designs without modifying the PR's...

And yeah, there's little practical difference between 9" and 10" on BSC- just try modeling it in VituixCAD and you'll see what I mean.

[Face]

A pair of Anarchy woofers in a 1.2cf sealed enclosure sound pretty good. As for passive radiators for a pair of Anarchies, look at 10s or larger.

[JonMarsh]

A pair of Anarchy woofers in a 1.2cf sealed enclosure sound pretty good. As for passive radiators for a pair of Anarchies, look at 10s or larger.

Definitely - I wouldn't be surprise to see the 10" ScanSpeak discovery is a reasonable match... thanks for the feedback about sealed, too- I'll have to see whether I have the 4 ohm or 8 ohm version... I just don't remember. And they STILL don't have specs up on the site for the 4 ohm version, though one presumes the sensitivity might be 4 dB or so higher. But Qts is low enough for the 8 ohm rated version, and if Re isn't too low, they might be pretty good paralleled the way you describe... certainly the price is right!

[scottvalentin]

As I look at the pictures of all these crossover parts and having followed this thread and read much of the Ardent threads (looking forward to Bob's progress on the veneering), I can't help but look at the $1,000's of dollars of crossover parts and wonder where an active crossover approach makes more sense.

Can you build an Ardent or Minerva using a MiniDSP, or is the crossover typology (Cauer/Elliptical/MarshmagicNthOrder?) too complex for such an application? Or, does the MiniDSP introduce unwanted noise? I'm just curious when I see the bill of materials for the crossovers and why an active crossover doesn't come up much.

Thanks and these threads (including Osiris/Isiris with Meb46's drool-worthy models) are very informative and exciting!

[JonMarsh]

Well, for me, the $64 question is do I want to run the output of a digital source component running at 24/176.4 sampling rate using re-clocking with rubidium reference standards and having a very high internal S/N (relative to what we can do in the real world these days, which means about 21 bits of real resolution, and a noise floor at about -140dB, though a miniDSP sampling at 48 kHz? For that matter, do I want to run CD quality material from one of my other digital setups, using an Alpha USB converter to AES/EBU into say, my AURALiC Vega, through a miniDSP?


Somewhere I've got a miniDSP, and I saw it a few weeks ago, and should have grabbed it and brought it home to do some testing. I need to make another storage unit run (to pick up an Anarchy 7 to test), there's a small chance that will happen tomorrow, and if so, I'll try to find the miniDSP without taking too much time.

If/when I do, then it's on to the APx555 to see how good it is.

If you go on their site, they have so much more in the way of product offerings and support than when I bought mine... but I'm having trouble finding detailed S/N or distortion specs. Maybe someone can point me to the right pages.

I'm sure that for mobile and some other applications these could do a great job of cutting out the crossover component cost (about $400 for the Minerva) but then you have to add amps- which ones? And amps and digital crossovers have a footprint too, and it's often not one that's hard to hear or pick out. Just think about how many preamps my friend in Munich and I have listened to in his system, and found wanting in one way or another compared to what we have found as references... and that's audible through speakers that are admittedly not perfect, but pretty good. (say, in our opinion, not as good as my homegrown Isiris, but still fairly transparent in the range where must music is found- between 100Hz and 10 kHz. (the Isiris has the clear edge in the high treble and the overall mid bass to low end definition and extension).

I've done the electronic crossover thing with analog, and moved back from it, because doing it well enough was pretty expensive (two way crossover for my X1 SLAM clones, back in the 90's)

Where I do expect to use something like this in the near future is for part of the LF system- i.e., the low frequency crossover and EQ to the bottom end of a system. That probably could be applied to a Minerva, but it seems overkill for that size speaker. And the big money in the crossover is in the midrange to treble. But that could be done, with some adjustment to the rest of the design. Doing the LR6 type crossovers should be possible with a good DSP system, I just haven't looked at that closely, and then with tweeters, there's the fine tuning and shaping of the response due to baffle issues, waveguide issues, etc. Some drivers are easy to work with using electronic crossover, others definitely not.

YMMV, it would be cool to see more projects like that, but I'm creeping into that direction very slowly- I plan to acquire an Accuton DSP, working with MEB46 on some things, and build a custom supply and interface for it, and see what it can do... which will also involved benching it.

Keep in mind, I'm just basically leary of running my source signals through another digital processor, after all the time and effort I'm putting into all kinds of noise reduction (differential and common mode) in the front end. (for instance, have bits for a new digital playback setup prior to the DAC which I have some hopes for, at reasonable price, but not more on that until I've received and tested it.)

[Juhazi]

MiniDSP has HD models that run 24/96 internally. Advanced settings mean biquad and I guess elliptic acoustic slopes would be easy even with LR4 and some eq of response. https://www.minidsp.com/applications...ad-programming
The new 2x4HD box would be enough if one makes mid-tweeter xo passive and has 2x good stereo amplifiers.

I understand that JM is suck with hires and so fine. But anyone who is interested in digital xo can quite easily imitate his measured on-axis slopes to achieve very much the same performance.

[JonMarsh]

As I look at the pictures of all these crossover parts and having followed this thread and read much of the Ardent threads (looking forward to Bob's progress on the veneering), I can't help but look at the $1,000's of dollars of crossover parts and wonder where an active crossover approach makes more sense.

Can you build an Ardent or Minerva using a MiniDSP, or is the crossover typology (Cauer/Elliptical/MarshmagicNthOrder?) too complex for such an application? Or, does the MiniDSP introduce unwanted noise? I'm just curious when I see the bill of materials for the crossovers and why an active crossover doesn't come up much.

Thanks and these threads (including Osiris/Isiris with Meb46's drool-worthy models) are very informative and exciting!

One additional comment-

MiniDSP their high end solution for room correction, with Dirac built in- this is a 24/96 internal resolution solution. Unfortunately, it uses ASRC to convert internally, and if you're concerned about things like the Schitt Yggdrasil which uses closed form calculations to assure that digital up sampling is done without approximations and all the original bit samples are preserved, well, that just goes out the window. Still, I bet they would be fun to play with...

On the other hand, I have a tale to tell, which I haven't got around to posting yet, which is Munich Report Part 2. Bad experience with room correction.

Last, here is some copy for the miniDSP with Dirac from their web site:

The DDRC-22D is typically deployed in the digital signal chain just prior to D/ A conversion. Benefits of deploying the DDRC-22D with Dirac Live® include improved imaging and clarity, tighter bass and reduction of room resonances, elimination of early reflections, and reduced listening fatigue.

Ok, let's get real here- at one listening position, you can attempt to correct the amplitude perturbations which occur because of these architectural issues. If it is something close to a null, you simply can not fix it. Can. Not. Stop. Period.

Early reflections create dense comb filtering. I seriously doubt you can fix this at a listening position- you certainly can't remove them from the room.

Room resonances, same story- the modal responses will be there- you can modify the amplitude impact where you are sitting for early sound- then what will it be else where?

I am not a fan of trying to fix acoustical problems with equalization issues. OTOH, I can imagine the Dirac setup would be quite useful for contouring a speaker that had a lot good characteristics and low distortion, but maybe was too flat, or had a slight suck out in some region? Or a little too much? It could be a very interesting tool for subjectively tuning the reposes, and seeing what seems to be needed. But should be correlated against other listening techniques, too.

Anyway, more about this when I get around to Munich Report Part 2.

[JonMarsh]

Well, UPS delivered, rather late, but they delivered.






It's apparent from peaking at the voice coil, that there is enough overhang to have the quoted 5mm or so of Xmax; on the other hand, the front suspension is pretty much identical to the C18En001, which is really not designed for anything more than 1, maybe 2mm, so this is clearly still a midrange driver.






It will be interesting to get some testing done after we get back from the Tahoe area... don't expect that until later next week, though. Must admit I'm curious.

Truthfully, I'm curious, too, how the C18EN would do with a reed paper cone...

[TEK]

Jon: I'm looking forward to here your experience with room correction.
My experience with room correction is not very good. I have tried to set up room correction with my Marantz AV8001 (and before that my SR7005) several times but the end result is always that I turn it off - never got a sound that I'm very happy with when using room correction.
I try it for some time, but in the end I always end uo with it off.
It might bee something special at my place as it seems to apply a lot of extra level in the upper frequencies.

Now, I do not think that it is right to compare active crossover to room correction - but both things are interesting concepts.

[JonMarsh]

the common thread is using a DSP setup- in this case we're talking about the miniDSP. Using it for room correction is easier than other applications, because you can output in the digital domain and feed the existing DAC- where as for crossovers, you pretty much have to use built in DACs, which creates a whole other ball of problems, IMO.

OTOH, I'm not even remotely surprised at your report of personal experience with room correction- I think it has some possibilities for speaker voicing, but my experience in Munich agrees completely with what you say, and it was a VERY, VERY expensive system-

[ergo]

Some progress. Both crossovers are attached to base boards and one is soldered up. I made a small change too in mid cross I replaced L3 from 0.62mH to 0.68 for a moment as the one I ordered was too small a wire diameter, so I decided against using it. Measurement with 0.62mH one gave very slightly different result. I will check further and perhaps unwind the 0.68mH ones to the intended value.

The LspCAD plot shows simulated versus measured (gray line / 10ms window)

VituixCAD plot shows the 0... 90deg measurements with this xover and again 10ms gate.

[ergo]

Measured hor+20deg with MID normal and reverse polarity (not quite as good as simulation)
And 1/3 octave RTA in middle of the room

[JonMarsh]

It's looking pretty good to me- especially the RTA plot, which is also very room and placement dependent.

Now, the $64 question is, how does it sound to you with program? 8)

We're heading out the door shortly for the south Tahoe area- will be back late Tuesday night.

[5th element]

According to SEAS, Jon, the MR18 has 3mm of one way xmax, not 5mm. If it is suspension limited to 1-2mm then this hardly matters but having some extra coil throw will make sure that if you do drive them beyond where the suspension is linear, at least the distortion will remain low order.

[JonMarsh]

Yeah, I'm thinking the MR18REX may not be a bad deal for the money. No plan to use it below 300 still...

Maybe we should segment along the lines that the C18EN001 is only for the spiffy Translam builds, and the MR18REX is for the Minerva TS? :W. (TS = Table Saw) That would solve the problem of what to load it with, in the end....

[hyperducky]

Ergo how did you enter the midrange components into virtuix cad? Can you screenshot the main page with the mid crossover entry?


Sent from my iPhone using Tapatalk

[ergo]

This is the 1.4 version from Jon

[Steve Manning]

Prep work continues for spraying finish ...... at this point ~70% of the parts need some kind of repair of voids, as well as sanding to 220 grit and 2 coats of sealer. This is adding considerable time to the process as one can imagine.

[Steve Manning]

Even so ..... the pile is slowly moving from the garage into the dining room as they get finished. I'm expecting all of the stand parts to be ready for finish by tomorrow ....... I also have half of the cabinet sides done as well ......





Hopefully the parts will be safer there with our cats than me in the garage :unsure: Though they can get creative when they want to.

[JonMarsh]

Those are looking very nice, Steve! :T Cats can be a problem, if they take a shine to something...

Just got back from being incommunicado in the Lake Tahoe area- it's good to be able to be back in touch... too bad I've got this feeling I'm going to need to cram 5 work days into the next three! Have some customer visits lined up, too.

[sliceofhogan]

Completely off-topic, sorry, but for our eviltwin an evil straight-four custom....


Image not available

[ergo]

Great work Steve. Hope this project has not turned to 'oh I'm sick and tired of seeing those pieces again' phase yet and you'll get to the music listening part soon as well.

***

I got both speakers wired with crossovers finally yesterday and verified with quick measurements. All xovers are outside the boxes for now.

Initial rush listening session that covers small samples of various music styles gave a positive first opinion. Wife agreed as well and commented that there is finally enough low end body in music... with Modula MTmkII-s we have in family room this department is still kinda soso only.

More listening and driving the speakers in to be done in next few weeks before I start trusting what I hear, but I am very happy to be far enough finally to be able to enjoy this next step

[Steve Manning]

Great work Steve. Hope this project has not turned to 'oh I'm sick and tired of seeing those pieces again' phase yet and you'll get to the music listening part soon as well.

***

I got both speakers wired with crossovers finally yesterday and verified with quick measurements. All xovers are outside the boxes for now.

Initial rush listening session that covers small samples of various music styles gave a positive first opinion. Wife agreed as well and commented that there is finally enough low end body in music... with Modula MTmkII-s we have in family room this department is still kinda soso only.

More listening and driving the speakers in to be done in next few weeks before I start trusting what I hear, but I am very happy to be far enough finally to be able to enjoy this next step

Thanks Ergo ...... I will admit to a little "oh these again". The main reason being I was not expecting all the void issues with the wood, so that has added a lot of additional work to the process. Though it's starting to get there.

I'm glad your liking what your hearing from your set.

[JonMarsh]

An interesting suggestion or heads up from Steve yesterday- regarding capacitors. I'm beginning to think Steve spends a lot of time on Troel's site- can't blame him, if I had more spare time, I might, too...

http://www.troelsgravesen.dk/Alumen_Z-Cap.htm

These are a low voltage film and foil cap designed just for speaker crossovers... not metallized film, but film and foil. Something I've generally had some good results from in the past.

This is a link to the Jantzen description.

http://www.jantzen-audio.com/wp-content/uploads/2016/04/Alumen-Z-Cap.pdf

So, being the gullible sort that I am, I did a little further investigation... and didn't find much of anything, other than what's on Jantzen's site.. but I did find what looks like a solid vendor for them, and the prices are not bad at all...

http://www.hificollective.co.uk/catalog/jantzen-alumen-z-caps.html

Besides being Brits, which always is a plus in my mind, they actually have the temerity to have online display of in stock quantities... so I called their bluff last night, and ordered a pair to try in the Minerva (the described characteristics sounded like they might be a good fit to the C18EN001 tweeter) and low and behold, got shipping notice in my email from FedEx and from the HiFi collective this AM.

BTW, these guy seem to have a lot of interesting stuff, if one is DIY oriented, not just for speakers, but electronics, too. I expect I'm going to be getting to know their web site better in the near future... a lot of components, and some interesting kits.

[sdl2112]

Jon, I was just looking at those too. Let me guess...you bought the 2.7uF. Just the other day they had 24 pcs of each now only 22 of the 2.7uF. You must be the first to purchase from them. What was the shipping cost for those?

I like the description of the sound Jantzen and Troels describes. I just wonder if Troels would have the same comments if he didn't read Jantzens description first...not criticizing...it just how the brain (at least mine) works. I do look forward to your evaluation.

[JonMarsh]

Shipping was 15.60 pounds Sterling, which is about 23-24 USD. Thats out to California- might be a little less going to the East Coast, but who knows?

Yes, Troels and Jantzen's description sounds like it would be a good match to an aluminum dome tweeter- not as sure regarding say, a diamond or beryllium, but if this turns out favorable, might be the next thing to try. Actually, Jantzen's description is partly what convinced me, because IMO their silver-gold caps a a bit unnaturally hyper detailed on the top end, which is why from them I've usually preferred the standard Superior Z-Cap, or the Clarity MR's. 10 years ago I was getting some nice results from some film and foil, so with Jantzen doing that, I figure it's worth a shot- next test will be when I rework the Isiris diamond crossover- the price is certainly an attractive balance.

At the price these are selling for, if they deliver what Troels hints they do, they could be a real sleeper, or "best kept secret" IMO.

[JonMarsh]

I got the emulation to work today and listened to single speaker for about 30 minutes with the VituixCAD ver of your crossover and then very slightly modified one trying to get the phases to match with my measured data.
I do like the sound potential - that is there for sure... the details of voicing - too little listening still. I will be attempting to make some measurements of the speaker in mid room as well as in listening position to see if the balance seen on screen maps to what it is in room.


[ATTACH=CONFIG]25581[/ATTACH]
[ATTACH=CONFIG]25582[/ATTACH]

Hello Ergo,

I could say this with just a PM, but I think it is more appropriate to mention in front of the whole forum (well, those reading this thread) Thank you again for bringing the VituixCAD software to our attention- it's becoming a very indispensable tool, in spite of the few small things I miss from my previous favorite- there are so many convenient and useful functions, especially in the Tool Box, that I foresee a long and fruitful (hopefully!) association...

Thanks again! And thanks to Kimmo for developing this and making it available to others at a very reasonable price! :T

[Juhazi]

Shipping was 15.60 pounds Sterling, which is about 23-24 USD. Thats out to California- might be a little less going to the East Coast, but who knows?

Yes, Troels and Jantzen's description sounds like it would be a good match to an aluminum dome tweeter- not as sure regarding say, a diamond or beryllium, but if this turns out favorable, might be the next thing to try. ...
At the price these are selling for, if they deliver what Troels hints they do, they could be a real sleeper, or "best kept secret" IMO.

One thing that makes me wonder (or actually makes my neck hair rise) is Troels' reference recording
"The Bosendorfer piano used by Keith Jarrett's in the Köln Concert is a recording I've been listening to for decades and believe it or not, but I remember the sometimes hard sounding transients from my system 10-20 years ago. How it really did sound we'll never know but the recent Alumen experiments added another level of appreciation."

This recording is a classic, but sound of the piano and recording are just a catastrophe! The legend is in his playing, not the sound. http://theconcourse.deadspin.com/kin...ett-1683837639

"Jarrett was sleep-deprived and harried that night, and his mood wasn't helped by the fact that the opera house had supplied a relatively small, poorly tuned piano rather than the Bösendorfer grand that he requested. Even after an emergency tuning, the instrument supposedly sounded like a toy, with shrieking high notes and little projection in the low registers. On the record, having passed through two microphones, the piano has an almost otherworldly sound, like it's five stories high and made of glass. Jarrett plays it harder than he does on his other solo recordings, bashing the keys and keeping largely to the mid-range notes, perhaps out of frustration. "What happened with this piano was that I was forced to play in what was—at the time—a new way," he explained years later. "Somehow I felt I had to bring out whatever qualities this instrument had."

[JonMarsh]

I can see why that is cause for concern- I've read the same about this recording in the past- but at the price they go for, I figure it's worth a try, especially with only one cap in the series path in this project. Piano's are so, so variable (I speak as a keyboardist in a past life who worked his way through college) but the trick will be giving these as shot with recordings I know well and use for this- if they show promise here, I'll probably buy a set to replace the caps in my Ardents and see how that compares...

[Juhazi]

Yes I believe that those caps are fine. But perhaps we just discovered why Troels tunes his speakers a bit down in low treble!
I didn't have that record until I downloaded a HD version two years ago. First I thought that my dac or amplifier went broke... It was a relief to find those stories about the recording session.

ps. This is a good one https://en.wikipedia.org/wiki/Standards_Live

[JonMarsh]

Yeah, I have Standards Live and a number of other albums of his... if someone was new to Keith, I'd say that would be a great place to start.