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

[JonMarsh]

Ergo,

How does it work buying from shops in the EU from Estonia? Is shipping the coils from USA to Estonia a problem? (I'm sure you explained this previously, but just asking again- no time to read through everything right now.). Is it a customs thing? Duty, even as a gift? Just wondering if there isn't some way we could expedite this for you.

I've been getting a lot of stuff lately from HiFi Collective in the UK, they're becoming my go to source on crossover components because of the mix of offerings they have-

Yes, if you can experiment, even though not practical for day to day use, try a Cardas room setup as described on one of the references on their web site. I've been using the same concept for decades. As a result, most of my designs are optimized for flat anechoic response, which works well with this positioning. Only exception is the occasional build in to the wall, done like a studio monitor.

[ergo]

In PE case the cheapest shipping for 4 coils would have been 67USD to Estonia. Then the VAT is 20% on the goods+shipping, +about 3% import tax on electronics. So sorta gets a bit too expensive along that line.

US shipping was only few USD afaik, so I hoped that by hand carry I would be much better off as I was going anyway. No huge issue with this, I'll find someone in next weeks I'm sure who will bring the stuff over.

[Steve Manning]

Stands are done ...... Finished up the stands today, here's a few pics before they go to UPS tomorrow .....

[Alaric]

Wow. Just wow. You guys really take the duct tape out of DIY. Those are the best looking stands I've seen, ever. Beautiful concept and execution. :T

[Evil Twin]

Exceptional workmanship - as I have said before, the Force is strong in this one.

[Steve Manning]

Wow. Just wow. You guys really take the duct tape out of DIY. Those are the best looking stands I've seen, ever. Beautiful concept and execution. :T

Crap I forgot the duct tape ..... they'll never work! Thanks Lee, appreciate the kind words.

[Steve Manning]

Figured I'd better do a quick check to see if the stands would hold up the cabinets before I sent them out.





Of course the Imperial inspections were present .....



Even without the sides attached yet, I think the scale of the stand and cabinet work pretty well. Guess that CAD stuff works!

[JonMarsh]

Gee, the stands ARE a bit prettier than the cabinets... but signs of things to come!

Is that the pup in the background that had the big Vet visit recently?

[sdl2112]

Very nice indeed...looking forward to the finished cabinets. The inspectors do seem to approve.

[Steve Manning]

Gee, the stands ARE a bit prettier than the cabinets... but signs of things to come!

Is that the pup in the background that had the big Vet visit recently?

Yep, that's her ..... she did not really enjoy that experience at all. She is still a little off yet, but she'll get there.

[Steve Manning]

Very nice indeed...looking forward to the finished cabinets. The inspectors do seem to approve.

Thanks Scott ........ an FYI for you. We talked about spraying in the higher heat and humidity leaving a rough finish, I found a good way of dealing with that. I picked up some 3000 & 5000 grit 3M Trizact sandpaper at Advanced Auto, it's on a foam backing. Did a nice job of just knocking down the roughness without scratching the finish up and left the finish as the satin I sprayed.

[Steve Manning]

Very nice indeed...looking forward to the finished cabinets. The inspectors do seem to approve.

Thanks Scott ........ an FYI for you. We talked about spraying in the higher heat and humidity leaving a rough finish, I found a good way of dealing with that. I picked up some 3000 & 5000 grit 3M Trizact sandpaper at Advanced Auto, it's on a foam backing. Did a nice job of just knocking down the roughness without scratching the finish up and left the finish as the satin I sprayed.

[sdl2112]

Thanks Steve...I do have foam backed 320 and 600 grit and also a variety of automotive grit paper. If all goes well I should be able to spray this weekend...of course the heat index is predicted to be well over 100.

[Hank]

I picked up some 3000 & 5000 grit 3M Trizact sandpaper

Nice. Just add some blue painters tape and the project is complete. :B

[Steve Manning]

Hank, take a closer look at post 717 it's there .....

[JonMarsh]

He's gotcha Hank- this guy is a man of detail! :T Got the bases covered...

[MikePM]

Jon:

I've been following this thread and was greatly disappointed when Seas discontinued the design's coax driver. I'm hoping to build a new speaker this year and this small three-way is about what I'm looking for (although the CNC version is way above my skill level). Is an alternate design using the MR18REX/H1669 mentioned earlier in the thread, still likely? I suppose that if this driver doesn't work out, this might not be a design that can be duplicated.

Thanks
Mike
--------
Zaph L18
Marantz SR7008
Pro-ject Expression

[JonMarsh]

First, I think an alternate design with the MR18REX is quite feasible- it's in my queue to test, have the enclosure setup for it (which currently holds a C18EN001). Second, what we're hearing is that there seems to be an update for the C18EN001 in the pipeline. It's always a question as to how long that will take, and what they are addressing, and what this means for the crossover design.

We've had a lot going on the last few weeks which has reduced my available time for audio temporarily- heck, I haven't even finished the BOM update and ordered inductors yet, though I have all the caps on hand to the best of my knowledge. The roofing job and about half the electrical work is behind us now- the solar installation is going to be the last week of this month; as well, I have one of my nephews from Texas coming out to visit, but I'm going to see if I can't give him a little hands on experience with DIY audio- he's expressed interest in that, will be here for the weekend of July 4.

So hang tight, unfortunately I've got a lot of domestic work to do this weekend, so I don't anticipate getting back to the measurements until around or after July 4th. A physical examination of the MR18ERX is pretty promising, and we certainly can't complain about the price... I may even try them in the acoustic prototype enclosures as a build, after I get the cabinets from Steve and get those finished up. Stands are shipping to me this week- the cabinets will be a while yet.

[NyxOne]

First, I think an alternate design with the MR18REX is quite feasible- it's in my queue to test, have the enclosure setup for it (which currently holds a C18EN001).

FWIW, here's a 3rd party measurement of the MR18REX (FR, Imp, THD, Waterfall).

Tweeter performance look far from stellar... but that might just be me misreading measurements. The 50dB scale make it look terrible!

Chuck

[JonMarsh]

Thanks for the link- these results show why the MR18REX won't be easy to work with, anymore than the C18EN is-

The tweeter distortion profile shows you really don't want to go much below 3kHz and you want to roll it off hard...



The response does look more variable with different measurement axis than the C18EN... he is only using 1/24 octave filtering.





The woofer may be even more difficult to work with than the C18EN-




It has some serious peaks to deal with just above 3 kHz- off hand my strategy would be to nail the first one with a notch filter, and as with the C18EN, use an LR6 network for a fast transition band changeover.

Otherwise, I have to think the measurement is a bit compromised below 500 or 600 Hz= the baffle has a lot of impact, so I'd reserve judgement until doing my own tests.

Thanks again for the link.

The thing that people will likely find a bit weird, is that I suspect the coincident source and time alignment will mitigate some of the other issues if they're handled properly, and this still has the potential to make a very pleasing system.

We'll just have to see how that turns out... who knows, maybe this weekend or even tomorrow night I can measure this myself. Need to get some last measurements out of the way and then tear down and store for a few weeks due to other things in progress.

[Hank]

Steve: I had missed it in #717 - thanks!
Yep Jon, he's a pro's pro!
I've got a list of cars to test drive when I win the Lotto - I think I should add CNC machines to the list ;-)

[TEK]

Stands are done ...... Finished up the stands today, here's a few pics before they go to UPS tomorrow .....

[ATTACH=CONFIG]25960[/ATTACH]

[ATTACH=CONFIG]25959[/ATTACH]

[ATTACH=CONFIG]25958[/ATTACH]

[ATTACH=CONFIG]25957[/ATTACH]

[ATTACH=CONFIG]25956[/ATTACH]

Impressive, just impressive! ;x(

[Steve Manning]

Thanks TEK

[Steve Manning]

Brought out the rotisserie jig and started spraying the first cabinet center section. So far it's working pretty well for spraying and sanding between coats of finish. Discovered translam would not be the best approach for that high gloss look though. Even after lots of sanding and filling you can still see the joints a little ...... Scott I think that satin finish will help a little in this case for those imperfections ...... Of course this is lacquer and not regular paint. I imagine a good coat of polyester gel coat as a sealer would level things out a lot better before the paint and clear coats.

[sdl2112]

Great effort and progress Steve...keep churning away. :T

[sfdoddsy]

Sorry for a slight thread-jack, but I didn't know the C18 had been discontinued.

A real shame.

I was just about to post about how much, after living with them for a while, I'm enjoying my C18 based open baffle system.

There are still things I should do to optimize the crossover, but it is so friendly to listen to and look at that I haven't been able to muster the energy.

[JonMarsh]

There is hope that it's just a temporary hiatus, but we'll just have to see. Measuring the MR18REX is on my to-do list, but boy that list is wide and long these days... It will happen, though.

Glad to hear you are enjoying them, even in a not completely optimized form.

I've got my pair of stands from Steve and they look just as good as the pictures, even better actually... :W

[Tony ray]

Hello all,
Very interested in this build as I have always liked the idea of coaxial drivers.

Went to the Australian Hi Fi show in Melbourne on the weekend and was very impressed by a speaker there that only used a Seas magnesium coaxial in a ported standmount.

Any feed back on how your finished speakers are sounding? Are you happy with them ?

[Steve Manning]

Hello all,
Very interested in this build as I have always liked the idea of coaxial drivers.

Went to the Australian Hi Fi show in Melbourne on the weekend and was very impressed by a speaker there that only used a Seas magnesium coaxial in a ported standmount.

Any feed back on how your finished speakers are sounding? Are you happy with them ?

Hi Tony,

The ones here in the US are not done yet. Jon has the stands and can start on the crossover installation ..... though as you can tell he gets a bit distracted from time to time and has a few other projects that need his attention as well. I'm continuing to finish the cabinets, though that took a bit of a hit with some family issues and a visit out to the west coast for vacation.

I believe Ergo is done with his, though he might have some more crossover tweeks, he can best answer that.

Steve

[ergo]

Hi,

Mine are 'almost done' in a sense that the speakers are intact and play, but crossovers are sitting next to them out in open for now still. I've been listening to Minerva's and also waiting to get the PE coils for woofer to try out next to the Janzen toroids used now.

The initial feelings were that these for sure are best pair I've built to date. First ones where I feel they are truly full range as there is a lot of punch and energy down low (but only when there should be something). Then after a week or so I did move them further out from the wall. Speakers in general don't wanna be too close to wall, but the big PR on the back in this case probably adds to that. That made the bass to be very good and 'fast acting' and stopped the bit of after rumble that tended to happen close to wall with some music material due to room modes.
I have liked speakers with waveguide + tweeter or now the coaxials due to their wide uniform dispersion and the fact that one does not really need to sit still in a very defined spot to get the best sound. With these one can move a fair bit left/right/up/down ect before the stereo image gets disrupted.

Now the latest developments are related to the 'system voicing' curve Jon brought up,
more of it in here: http://www.htguide.com/forum/showthr...-investigation

This curve added to the current Minerva crossover does wonders. Now majority of songs sound very good to me and the imaging and depth has improved further (which is not something I expected from an EQ curve).

There should be some further developments still. One workmate is over in US, so I have some hopes he can bring by coils with him that are waiting there. Also I will redo the measurements for Minerva's this week. Reason is two fold - I'm interested to see how much the measurements have changed after burning in the drivers. Also I think I've learned something from last rounds after the fact, so I'd like to get another go and then perhaps see if I can attempt to massage this type of EQ curve into the actual passive crossover behavior. That would be interesting to try and compare to the EQ on line level.

**
The availability of the C18EN001 is a bit of an open question still. It has been out of stock for a while now. The MR18REX/XF is maybe a replacement, but not a drop in replacement for sure. That's sort of a sad side for this project unless C18 comes back one of these days.

[Steve Manning]

Since it's been a little since the last update due to family issues and a trip to the Pacific Northwest to visit family .......

The first set of cabinets finished with spraying .......







The parts will sit in the ac for a bit and then will get the aluminum trim installed and then final glue up. Then it's on the UPS truck for California.

[JonMarsh]

Very righteous, Steve! I really like how this has turned out since inverting what was painted and what is wood finish! That and all the incredibly detailed and meticulous work you've put in. :T

All part of the CV if we manage to pull in the other job. A lot of work done on that today...

[sdl2112]

Very nice Steve...I'm glad to see you back making progress...getting close. The black and white drivers should really complete the look.:T

[Hank]

So fine, Steve!

[Steve Manning]

Thanks gents ...... I think there finally getting there.

[Carl V]

looking great indeed.8)
Any scalloping needed for that
Coaxial/coincident Midwoofer?

[Steve Manning]

looking great indeed.8)
Any scalloping needed for that
Coaxial/coincident Midwoofer?

Thanks Carl ..... did not go with scalloping, but did put a healthy round over on the backside of the driver holes ..... there's a picture somewhere in the thread of that.

[JonMarsh]

This is designed for the C18EN001, which has a very small neo magnet assembly, with lots of rear window. Not at all like the MR18REX, for example, with the conventional ceramic magnet. That would take more care with a thick front panel.

[ergo]

Good progress Steve!

***

Being on vacation from a day job still leaves only a little bits of time in between of various honey do's and supervising the new fence build etc.

I have done some progress though. I did remeasure the Minervas last week (using Fuzzmeasure). I think I got things done carefully enough for horizontal 0 ...180 deg measurements and making sure the phase is accurate for all files etc.
I also followed Kimmo's instructions (in finnish) here for creating the better off axis simulations for the low end of mid and woofer.

Based on this I've modelled a new revision of the xover I plan to try. I attempted to add "Jon's voicing EQ" into the curve shape too, so will be interesting if it'll work out. More work to be done tomorrow to figure out the part list needed to make these changes.

More images in Flickr

[JonMarsh]

For now, I'm voicing/building the crossovers in a more conventional way, and keeping the voicing filter separate, as it's pretty easy to change or tweak the RCR voicing filter compared with re-doing a number of filter components in a crossover.

[sfdoddsy]

There is hope that it's just a temporary hiatus, but we'll just have to see. Measuring the MR18REX is on my to-do list, but boy that list is wide and long these days... It will happen, though.

Glad to hear you are enjoying them, even in a not completely optimized form.

I've got my pair of stands from Steve and they look just as good as the pictures, even better actually... :W

Another alternative might be one of the KEF coax drivers.

They are only available to DIY if you have the serial number of a KEF speaker and say they are replacements, but that shouldn't be too hard to find.

[Steve Manning]

Sides going on ........ have the trim installed on the first cabinet. Spent a fair bit of time removing epoxy squeeze out during that exercise. I have now moved on to installing the first side. Fortunately the humidity has dropped since this morning, so the heat index is now only 104 instead of 108 that it was earlier, so a little less sweating going on. Of course adding a double layer of lbl to the side of the cabinet kind of balances things out with a little more grunting involved in moving the cabinet around. These things are going to be heavy "little" beasts when their done.

[JonMarsh]

Hello from Palo Alto and Stanford-

Looking very good Steve- your report of the temperature makes me cringe, because I know how high the humidity gets there, compared to CA- and we only had a paltry 98 yesterday...

[Carl V]

looking great.... I see that interior bevel now.
Another question what is the hump for on the
bottom of the enclosure?

[JonMarsh]

That's where we install a special space time modulator that provides an inverse FFT of the music spectrum direct to your brain, but aimed at subliminal induction to stimulate the pleasure centers without you being consciously aware of it. Yeah, it's kind of cheating, and probably violates some FDA rules or something, with regards to wireless medical devices, but it's all good fun....