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

[JonMarsh]

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

Another odd thing-- Troel's measurement setup is a bit soft in the top end, by his own admission- and I've recently discovered it's more soft than even I thought, because of find out that mine was, due to some cables and adapters which were in use with the microphone setup- now replaced, and definitely more accurate. He may be voicing things that way deliberately, because with his system and setup, that's what sounds natural or right to him. The matter of system voicing is complex, and still evolving for me... in some cases in the past I think I have just gotten lucky overall, but not by fully understanding the relationship between power response and perception, but I think I'm making progress on that.

[sdl2112]

When Troels published his SS D3004/6640 data is was so different than mine I asked him about it. He did say his system was not calibrated out that high as I remember. Where it starts falling off I may not be able to hear but it should be accurate. I have to visualize a correction curve when I see his data.

For my setup I have a pair of Hiquphon OW1 tweeters with manufacturer test data that I compare against occasionally to make sure something hasn't gone awry.

[JonMarsh]

That's a good way to keep an eye on things. I have been checking lately against several tweeters, mostly ScanSpeak, for which good high frequency info is provided- particularly the 7140.

The thing to be on the watch for, is that something that causes things to be off 6 dB or more at 30 kHz MAY also be causing problems of a few dB down at 10 kHz or so....

In my case, the problem was the cables and adapters going between the buffer interface for my ACO Pacific PS9200 buffer and the TC Konnekt input stage. Situation remedied, but makes me feel a bit like a loon.

[ergo]

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

VituixCAD was a good discovery for me as well and I could not believe it took me a year+ before discovering it. I echo the thanks to Kimmo too!
I now use it as well and I do like it a lot. It also facilitates the LspCAD use in good ways (extended offaxis model), so for now I've been jumping a bit back and forth between the two. One thing I still like in LspCAD is the ability to save number of small iterations of the xover and then quickly compare. In VirtuixCAD one can save under different file name and reopen those, so it's sort of a habit driven I guess.

[ergo]

Microphones and the calibration of microphones is an interesting topic and getting it right is not an easy task. Due to my work there was a project where I needed to test different ECM/MEMS microphones. Doing that I needed to learn about the ways to calibrate/check the reference mic and then how to compare the capsules against this reference etc. In end I built a 'very scaled down IEC baffle' with a soft dome tweeter and a 2.5inch fullrange driver in them. This gave me a smooth enough source that goes to >35kHz without sharp dome issues. Latter is quite important if one uses a comparison/substraction method for finding the mic correction file that does not have anomalies above 10k. Also the lenght of the microphone body and the bracket holding it in stand does give it's own effects. I have some data somewhere on disk where I experimented placing a common measurement mic (EMM-6 from Spectum Labs) to a standard plastic bracket and then to various other more 'acoustically invisible' holders. It can cause +/-1..2dB ripples at high frequencies easily..... If one wants to then make a generic mic correction file out of it it can be smoothed by 1/3octave and it'll be pretty ok. But still, I think a most proper calibration would actually either define a mounting too or one should send in the mic + whatever mounting one uses so the whole can be measured.

For low end below some 500Hz I used a method from ARTA whitepapers with a small pressure chamber. That was not so easy either for repeatability etc, but I will not go into that.

[kimmosto]

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

I echo the thanks to Kimmo too!

Thank you very much Sirs!

Jon, official revision 0.1.4.10 is out now - in case you installed preliminary experiment few days and auto update message is skipped.
There is still some unstability in extrapolation with 1/3 oct. slope detection if peak or dip exists just in the beginning or end of measured frequency range. But generally 1/3 oct. slope detection gives better result than 1/2 or wider.

[JonMarsh]

Thanks Kimmo! :T

I'll be checking that out this evening!

[Steve Manning]

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.

Just wearing my "Research Minion" hat and keeping the master informed .........

[JonMarsh]

well, perhaps I've gotten a little carried away... :W

But the guys in UK at the HiFi Collective have attractive prices, run online inventory, and ship quickly-





This is my 2nd order to them, placed on Sunday, received this morning on Tuesday, for the tweeter crossover in the Isiris/Osiris update. A little bit of dangerous living, as I haven't had the chance to listen to the first ones yet, but since I will have crossovers to compare when I get done with the test build, it may be more informative on the diamond tweeters.

So, YESTERDAY I ordered another batch of parts from them. A bigger one, all the caps and resistors needed for one channel of the midrange and woofer crossover for the Isiris redesign. That hasn't shipped yet, we'll see how this goes, but the pricing and quoted shipping were attractive- more so than PE or Madisound.

[Steve Manning]

Fixturing ......

I've been mulling over the best way to move the cabinet around once I start applying finish. The idea of spraying a side .......wait for the finish to dry ....... flip ....... repeat ...... You get the idea. Also with the weight of these cabinets I was a bit concerned with damaging freshly applied finish during all that flipping.

I came up with this as a solution ...... I'm calling it "The Minerva Rotisserie" Even though the cabinet is not square and I can't get the rod positioned at the center of the cabinet, it still works pretty well.



These locking blocks are able to apply enough tension to stop the threaded rod from slipping and I can hold the cabinet every 90 degrees.









This way I can spray a side, give things a few minutes to set up, rotate and get the next side. Let the cabinet dry, sand and apply the next coat.

[JonMarsh]

Pretty slick, Steve...

In that alternate universe where i'm the chief designer for a speaker company, I'm sure you're the director of Manufacturing.... :T

[sdl2112]

Very cool setup Steve. It should help eliminate runs and allow you to adjust raking angle to view the finish.

[ergo]

Very nice solution. Your project makes a very nice tips&tricks of loudspeaker building series. Even has some metalworks included.

I've been thinking that it would be interesting to know how many man-hours per box of work it takes for these. If one would make a business calc out of that I'm sure you'd be closing in on the TAD price range.... but this is so much more fun to follow than someone just buying a new pair of speakers.

**
I'm listening to mine and enjoying and letting them play in. No urges to change anything in xover yet, even though those sit outside the box still just in case.

[Steve Manning]

Thanks gents ...... Ergo, your right about the number of hours that have gone into these and I've actually started a lessons learned document if we ever make more of these. There are a couple of things that I would certainly do differently that would save a huge amount of time. Of course since it's just me, myself and I doing the work it certainly has taken longer than what TAD could do.

[TEK]

Really appriciate you sharing the work progress Steve (and you to Ergo).
Great info and a lot of stuff to learn from you both :-)

[Steve Manning]

Small Update ...... All of the stand parts and cabinets sides have been repaired, sanded to 220 and have sealer on them, ready for finish.

Got the holes drilled for the SpeakOn connectors for the cabinets. Went with some color coded grommets to identify what connector goes to what. Wiring will have matching heat shrink to match.





First cabinet sanded to 220 grit and first coat of sealer. Voids and tear out repair next for this cabinet. I'm hoping ...... to be ready to start spraying finish by weeks end .... we'll see if life plays along?

[BobEllis]

Looking forward to seeing these finished, too.

[JonMarsh]

Very shiny, Steve. I don't know if either of us thought it would be this long a process... Of course, compared with the original Ardent build or the Three Way Design study, this is happening in a flash!

[Steve Manning]

Very shiny, Steve. I don't know if either of us thought it would be this long a process... Of course, compared with the original Ardent build or the Three Way Design study, this is happening in a flash!

So very true ...... of course we got off to a rather late start with the 2 month wait for the cnc issues to be resolved ....... even so it's taking a while top get them done.

[ergo]

I ordered the ERSE inductors from PE too. I'm in US next week I'll hand carry those back. I'll see if I could then do some high current test attempts on those versus Janzen ones too and of course will try to listen 1 versus the other.

[JonMarsh]

I ordered the ERSE inductors from PE too. I'm in US next week I'll hand carry those back. I'll see if I could then do some high current test attempts on those versus Janzen ones too and of course will try to listen 1 versus the other.

Cool, Ergo. My LCR meters like them better, but I'll be interested to hear what you think. The DCR is quite low on the Jantzen parts, which attracted my initial interest. With a little work I could come up with a fixture to test them at several current levels with one of my Aragon amplifiers, but there are so many irons in the fire already...

[Steve Manning]

Like our man Scott ....... void filling was on the menu yesterday. Since these are going to be "painted" I'm not looking for a perfect match in color. Using some West System epoxy with some filler to thicken it up for better void filling.




Also did a rearrange in the garage to set up my spray area ......





Sprayed some of the tinted lacquer on a test sample, which is next to some of the pieces getting colored.

[JonMarsh]

Hey Steve, you're definitely moving the ball down the field-

What do you use for ventilation with your home made spray booth? That's something that's always been a concern of mine, for various reasons- that's why I had that ridiculous fan setup even working out doors.







The pieces you've done look pretty nice! :T

[Steve Manning]

Hey Steve, you're definitely moving the ball down the field-

What do you use for ventilation with your home made spray booth? That's something that's always been a concern of mine, for various reasons- that's why I had that ridiculous fan setup even working out doors.







The pieces you've done look pretty nice! :T

I actually have the first coat done on the vertical sections for the stands shot .... going to go buff them shortly. We've got storms going on here for the next several days, so that's always good for interruptions to ones plans.

At the moment your seeing it ...... I leave the garage door open and of course wear a good mask. I give things a few minutes to air out after each part. Seems to work pretty well for as much spraying as I do. I would like to improve things, I have a window on the left side of the garage that I could put a fan/filter in. We'll see what long term plans dictate for those changes?

[sdl2112]

Like our man Scott ....... void filling was on the menu yesterday. Since these are going to be "painted" I'm not looking for a perfect match in color. Using some West System epoxy with some filler to thicken it up for better void filling.


[ATTACH=CONFIG]25892[/ATTACH]

Also did a rearrange in the garage to set up my spray area ......

[ATTACH=CONFIG]25891[/ATTACH]

[ATTACH=CONFIG]25890[/ATTACH]

Sprayed some of the tinted lacquer on a test sample, which is next to some of the pieces getting colored.

[ATTACH=CONFIG]25889[/ATTACH]

Nice paint booth setup Steve!....now what parts of the cabinet are painted and what is cleared?

[Steve Manning]

Nice paint booth setup Steve!....now what parts of the cabinet are painted and what is cleared?

Thanks Scott ..... it keeps spray off the tools and most of the bugs off the parts ........ The main cabinets will be painted with clear sides. On the stands, the outsides of the vertical sections will be painted, everything else will be clear.

[sdl2112]

I see...I was thinking of the rendering in the first post...

[Steve Manning]

I see...I was thinking of the rendering in the first post...

We decided to change the cabinet combination due to all of the void issue. Imagine the voids you having been fixing, trying to keep them looking natural and then having to deal with them all over the cabinet surface. A pain in the butt only barely describes it ...... so we swapped the colors around to cut down on that issue. Still have to fix the big holes, but don't have to worry about color matching.

[sdl2112]

Steve...I didn't realize yours was that bad...either way I think the new combination will look great.

Here's my primitive garage exhaust system. Worked surprisingly well (for water based spraying)...I have a door on the opposite side of the garage for inlet air.

[Steve Manning]

Steve...I didn't realize yours was that bad...either way I think the new combination will look great.

Here's my primitive garage exhaust system. Worked surprisingly well (for water based spraying)...I have a door on the opposite side of the garage for inlet air.

[ATTACH=CONFIG]25895[/ATTACH]

Looks like it gets the job done ..... with mine if there's any breeze going I have to close the side door or my tarps want to take off.

My biggest issue with the voids has been compounded by doing the tranlam thing. If you look at what you have and now spread it over the entire surface of the cabinet. What starts as a few, multiplies in a hurry. A lesson learned that's for sure.

[Steve Manning]

Moving the ball ......

Got some finish laid down ...... two coats of clear and tinted on these parts.

[cochinada]

Shiny! :righton:
So, will the speaker be entirely white? I lost track of it...

[Steve Manning]

Shiny! :righton:
So, will the speaker be entirely white? I lost track of it...

Nope, the center of the cabinet will be colored (it's more of a light grey, was going for a platinum) and the sides will be natural. Like this ......

[Evil Twin]

Nope, the center of the cabinet will be colored (it's more of a light grey, was going for a platinum) and the sides will be natural. Like this ......


[ATTACH=CONFIG]25907[/ATTACH]

[ATTACH=CONFIG]25908[/ATTACH]

I love the smell of fresh renders in the morning...

[Steve Manning]

This one's for you Ron ..... Picked up some of your finishing putting. I had laid down a coat of epoxy on all four cabinets for void filling. That was taking forever to accomplish, cure time on that is many hours. Since it always requires more than one attempt to fill in what you missed the first .... or second time, I went to the putty. Of course getting what you wished for, the new stuff gives you a whopping 3 - 4 minutes work time and the parties over. The pay off though is I can sand it out in ~ 15 minutes.



Of note ...... all the stand parts are finished being sprayed and are curing.

[sdl2112]

Nice progress Steve...glad you found a better way to fill the voids. How did the spraying process go? I don't think I'll go that route on mine but I'm always interested for future projects.

[Steve Manning]

Nice progress Steve...glad you found a better way to fill the voids. How did the spraying process go? I don't think I'll go that route on mine but I'm always interested for future projects.

Spraying has gone pretty well, other than the heat and humidity that we have been having. The finish looks good but ends up being a little rough to the touch. I believe this is due to the finish starting to evaporate before it's hitting the surface. The can recommends less than 50% humidity ..... we've been in the 75 - 85% range. So I will need to hit the parts with a high grit sand paper in a few days and see where we sit.

[sdl2112]

With all the rain here the humidity is very high. Next will be the extreme heat. That is one reason I likely won't be spraying. I just applied rattle can primer to my base and had the same issue. Turned out Ok...I think. I plan on making a small paint booth that I hope will help with the upcoming top and clear coats.

[Steve Manning]

With all the rain here the humidity is very high. Next will be the extreme heat. That is one reason I likely won't be spraying. I just applied rattle can primer to my base and had the same issue. Turned out Ok...I think. I plan on making a small paint booth that I hope will help with the upcoming top and clear coats.

I was trying to put a clear coat on the aluminum trim with a rattle can and after multiple attempts I've thrown in the towel. I'm going to put a protective wax on it to fend off oxidation instead.

[sdl2112]

You might look into having them anodized. Another idea is to apply an adhesion promoter then a top coat. I see this is used on aluminum and chrome wheels. They also offer other clear products for wheels.

[Steve Manning]

Thanks for the info Scott ..... next time I do aluminum, anodizing will be the way to go. I picked up some stuff from Meguiar's that is used on aluminum wheels for anti-corrosive protection. Looking at just keeping the oxidation at bay.

[Steve Manning]

Getting close to the first shipment of parts to the west coast ......

Stand parts will be finished within the next day or so, then their off to UPS. Spent the weekend getting the aluminum trim in place and finished final glue up of the vertical stand sections today.

Fixturing to hold trim in place for nailing and epoxy curing.



Part way there ....



After glue up today .....

[dar47]

Ah looking great! That guy does like receiving pallets of stuff. I can attest to that.

[Evil Twin]

Impressive, most impressive! Obi Wan has taught you well, too! :T

[ergo]

Nice progress Steve!

After some more listening and trials it's becoming clear that these speakers do need to be placed further from the back wall than the mere 20cm (as was sorta expected anyway). I hoped I can use and keep the speakers on the tv furniture. The PR on back against the wall will pressurize my room too much and the deep bass notes become too heavy at times otherwise. Moving speakers out by half a meter restores a much better balance.... I'm yet to do measurements for this though, so for now just a judgment by ear.
So the solution will be to also build a pair of stands and move the speakers to more optimal position. Up side of that will be that the crossover that are quite big and heavy would find their home inside the stands too like in yours.

The deal with ERSE coils did not go quite as planned. In end ordering form PE and getting them was more than 7 days, so I left US on Friday and those arrived on next Monday. So the coils are now stuck until I find some of my other co-workers who travels between US and Estonia to bring those along. So the comparison of Janzen vs ERSE is on hold for unknown time for now.