Saint-Saëns planar- AKA SMJ-40- time for a project now?

[JonMarsh]

A quick impedance and Fs comparison for samples of RSS210HF-4 and RSS210HO-4

RSS210HF-4







RSS210HO-4



Note the approximately 10% higher impedance, lower Fs, and much higher impedance peak- related to Qms.

Even though the cone mass is substantially higher for the HO, it is quite stiff and resonant upper breakup is at about 5kHz.

[JonMarsh]

More tests and calculations- tests in the single driver + PR 28L box setup with RSS265-PR with various PR weight disk configurations, and a Unibox Calculation with the Seas SL26R XM003 PR, in 20L, with one added disk (gives Mmp of 350g). if all goes as expected, will be mounting four HO's in the big prototype cabinet today, with the Seas SL26R XM003's.

First, a measurement comparing PR output for two weight disk configurations with the RSS265-PR and HO woofer- 1 disk (275g total) and two disks (350g total).




From this you can see how optimizing the PR tuning to the Driver Fs and Qms has its benefits in output that might not be expected with a "simple" thought experiment.

Next, a comparison of PR output and HO woofer output QNF, 1 disk, 28L. Though we can see the HO version is not as smooth above 1,000 Hz as the HF, for a three way system with a 450Hz crossover it looks just fine...


Last up, for fun, just a Unibox evaluation with the HO woofer and Seas PR, the SL26R-XM003, with one disk.




If valid, this shows interesting potential for the Seas PR and HO in an 80L net enclosure.

I wouldn't jump to conclusions before seeing hardware tested...

[JonMarsh]

OK, now comes the more critical part- working with the big box!

Of course, in the spirit of the times, I figure a little pirate cheer is useful to facilitate the assembly work...

"HO HO HO and a bottle of rum!"



With the four new HO's loaded up, checking the complete impedance curve was next up:




It's looking pretty much as expected, with Fb around 27 Hz, and the slightly higher overall impedance.


Next up was measurements at a variety of distances and elevations; this one is pretty representative for the listening and measurement axis. Note that the level at 500Hz (in the top of the woofer range for this design) and 30Hz is quite similar.




This measurement is at the listening range axis height. Just a Rectangular window, lots of room reflections with a 200ms window.

Looks like something that we can work with.

[JonMarsh]

Actually, that was a bottle of brandy, but it's as close as I could get for a Monday Priate Motiff!

[JonMarsh]

OK, what do we need to do with the crossover? I'm not publishing a schematic until I've tested and tweaked it (as/if needed), but I think getting something interesting in the ball park is not going to be too taxing... but optimizing a large speaker like this will require attention to both speaker and listening placement, as well as some room treatments, I expect.


But the basics look straightforward, and I already have another set of phenolic boards with connectors glued up, so construction can begin soon, as I had some hunches and ordered some parts right after Xmas, and am in better shape for an updated build than I might have expected...



Reverse null check looks good on paper...er, um, on screen...



And that's not at all surprising, given the predicted group delay and phase....




So, time to get the boards and parts organized...

[technodanvan]

Looks like PE heard you want some crossover components...

[Steve Manning]

Don't encourage the man he's bad enough!

[JonMarsh]

I did check this out, put it in my Task list to consider if I needed parts for the crossover update, but it looks like I'm covered with stuff on hand!

But, yeah... I mean, I'm not a stocking distributor, but I do have an awful lot of stuff on hand... you know, saved for retirement and planned projects?

But, I actually got lucky, because reading the tea leaves I was considering another mod for the HF version build, and the updates turned up to be nearly ideal- plus, I got to take out a big cap (100uf) on the LF crossover! Can you believe that? What are the odds?

[technodanvan]

I'd leverage that sale to grab some of the big caps I'll need for the Crescendos but I just don't think that's in the cards right now. I'm rolling with electrolytics for testing purposes and who knows when the final build will happen.

[JonMarsh]

Slow work takes time, but eventually it starts getting done!

Little things keep coming up, like finally getting a new phone after 4 years, to beat the expected tariffs that have been promised. That was needed mainly to boost onboard storage and memory, but a lot of the other details have turned out to be sweeter than I expected.

Just finished the LF POC Filter board, V3, next up will be the updated LCR zobel network V3.




This board is per the recent VituixCAD work, and measured data for the RSS210HO-4.

[JonMarsh]

Speaking of RSS210HO-4, I got some more in, and ran a few tests using the single driver and PR test box I built way back when... 2022?

A reminder, first, the free air impedance:



Then, we want to look at the impedance in the test enclosure with the original 275 gram single disk configuration:




Fb in the range of 27 Hz. problem with that is, that it is below driver Fs and effective coupling and output is low- similar to FR-30.

Dropping the disk, going to minimal PR mass of 200g...



Now we have an Fb of about 31 Hz. Very close to driver resonance, and should have good coupling and a reasonable PR output level combined with attenuation of driver excursion below 45 Hz...

Trust, but verify.

[JonMarsh]

IT's been one of those weeks... of course that could mean any number of things!

But making a bit of progress on the 2nd POC LF crossover test board...

Cut another board from left over Maple ply, mounting the binding post plates and velcro for the crossover and LCR board... I sanded the top nice and smooth, for a flat clean surface for the adhesive backed velcro to mount.




I've already fabricated the cable assemblies with ring terminals, this will go together tomorrow AM and some testing started...




I'll finish the wiring and some basic checks tomorrow, but since I received a new batch of M4 screws, and have lots of Ramp inserts on hand, I'll probably be laying these over and installing inserts so that I can fit and test RSS265-PRs soon. Most likely with no disks on them.

[technodanvan]

I asked this question in one of my threads Jon but I'm going to repost it here. Regarding inductor placement, I see you have two large air core inductors oriented in the same fashion on the left crossover that seem relatively close together (though scale is kind of difficult to see since those are rather large!), likewise with a P-core and toroidal inductor on the right. Did you measure inductance to ensure minimal interactions in these positions?

Also, are toroidal inductors subject to the same positioning requirements as 'regular' inductors if placed close together?

[JonMarsh]

The two large inductors placed relatively close together are wired in series, and any mutual coupling just increases the inductance slightly, which is just fine in this case.

Something to always keep in mind that for coupling to effectively occur, the windings need to be in the same plane or orientation. This is why orienting one inductor with the field orientation at 90 degrees to a nearby one kills nearly any potential coupling or energy transfer.

Now, toroidal cores are used for specific reasons- one of them being that the magnetic field is distributed over a 360 degree range, and so external interaction is minimized- both radiated and absorbed. And if you examine the layout of the LF crossover, the 2nd inductor construction has its magnetic field orientation at 90 degrees to the toroidal inductor at all times, due to its physical construction.

Note, in my alternate life I designed high performance magnetics, both inductors and transformers, for high frequency switching power supplies, including compound devices that acted both like an inductor and transformer, and planar transformers for very high frequency switching applications, having been tutored by skilled scientists on loan from Seinar Industries.

[JonMarsh]

Got the connectors all wired up, and hooked up to the POC LF cabinet and ran an LF impedance sweep check. Not half bad, if I say so myself-


Magico, eat your heart out!

[JonMarsh]

But, though we do acknowledge that "not half bad" may be pretty good, at HTG we shoot for a little more than "pretty good" most of the time.

With the results in post post 460 of this thread above, there are clear indications that getting better coupling near the Fs of the driver reduces the workload on the driver and the LF output, and that EBS (Extended Bass System) alignments don't always work as well as Unibox and other tools predict- especially if you need to include some enclosure damping to deal with standing waves in the long dimension of the cabinet.

So, what with all the other stuff going on around Casa De Juan, it took a bit more time to get the PR holes modified with a new insert set to work with the RSS265-PR, and to "un-disk" 4 PR's, but now there is some preliminary Impedance data to share. SPL probably tomorrow (wife is doing sewing machine work on the dining room table in the great room, and she likes her quiet while working...)


Direct Connection Impedance:





Impedance through crossover and LCR Zobel network:



I have a pretty good feeling about this, but let's not forget that song from "Boston"- we need data to have "More than a Feeling"

[technodanvan]

Your findings suggest I may need to rethink the whole "I don't wanna buy new drivers for this project" statement I made earlier.

[JonMarsh]

For now, as usual, I suggest sitting tight and see how things develop. I’m going to have to buy 3 more HO’s if I move the one in my single driver test cabinet into the second POC build (all the parts cut, but not assembled yet).

My wife is working with her sewing machine on the dining room table, so I won’t be firing up the SPL test until she goes out on her late afternoon walk.

[JonMarsh]

Well, got a few minutes free to fire up the test setup this afternoon...

Here's a composite plot of one of the PRs and the main front output, just out of the baffle step zone - looks like it's in the ball park, so hooking up the MF+HF module and crossovers is on the agenda first thing tomorrow. May need some level adjustments for the midrange and tweeter relative to the HO versus the HF. Both HD2 and HD3 are better than -60 dB in the 60-400Hz area, and nearly identical in level. That's something I like to see...

[JonMarsh]

Efforts have been going on "behind the scenes" so to speak, but I think I can mention that I just put in a parts order yesterday with Solen for some crossover parts to update one of the two POC1 Tweeter crossovers I built, and to trim one midrange crossover.

Of course, it all looks good in VituixCAD, but I'm going to hold off on sharing too much until I have hardware tests to back it up....

But, yeah, I have circled back to a modified version of the first early tweeter crossover design- one specific feature has some advantages in the overall implementation. And of course, this all involved re-measuring the whole setup.

Parts should be here next Tuesday- who knows, maybe earlier- the stuff from Solen got here a day early compared to the original UPS estimate.

Slow work takes time, you know...



Some additional internal damping is being considered for the woofer cabinet, though some of what you see here in the 50-60Hz area is boundary distance reinforcement. I.E., room acoustics.

[JonMarsh]

BTW, I've been ordering more stuff from Solen lately because PE didn't have the necessary common values in stock... strange. It's actually much easier ordering inductors from Solen, because of how they have everything organized into product families based on the wire AWG. This could become habit forming...

I've used Solen a lot in the past, but usually for specialty products or unusual size inductors. the last two orders have been what I would call fairly mainstream kinds of parts. I mean, it's hard to consider a 1mH AWG14 inductor as exotic, right? but couldn't get ANY 1mH inductor from PE yesterday.

[Scareurpasenger]

I ordered all my inductors from them during the sale last year. Also placed an order for a large number of drivers but canceled the order because another place had a better driver in stock. What I did learn is the shipping calculator is quite off. If I tell them to hold and charge actual shipping in the order notes, I usually save half of the shipping amount!

[JonMarsh]

Interesting, and thanks for sharing your experience!

[JonMarsh]

My most recent Solen order did arrive yesterday, and I've finished up a preliminary layout for the TPL75 tweeter crossover update. I guess I would call this the POC V3A or POC V3B version, since the cabinet is the same, but I've been trying to further optimize the crossover configuration and performance. Optimize includes both cost and performance.

This is the layout build that is now in progress this morning:





Which reflects this crossover update for the TPL75 Beyma AMT Tweeter:






The PT5010 board has had a few tweaks on the current board; documentation in process, but I'm waiting for the 1.2 mH inductors from Parts Express to complete the board update. I did order those with 3 day service, should be here today. This will be the midrange configuration used for either the TPL75 build or the PT2522c MOD302 build. I'll check the behavior, then publish documentation.

Slow work takes time... part update deliveries take time... JB Weld connector gluing takes time...

[JonMarsh]

Disappointingly, my 2nd day air order for new value L3 inductors for the midrange crossover has turned into a 6 day planned delivery, next Monday. I suppose it's weather problems for UPS.

As usual, slow work takes time...

[JonMarsh]

Just to show the WIP status for the midrange crossover, where I am currently waiting for the 1.2 mH, all other currently planned updates have been completed:





Midrange crossovers are usually the most complex part, and most expensive, because of the ear's sensitivity in this frequency range and depending on how high the "midrange" goes, a higher standard of capacitor quality is usually beneficial.

Here, the key caps are Clarity CSA copper connect for C5 and C22, and Audyn 800V double layer PP the shunt circuits and the parallel notch network for the upper range peak of the PT5010. Also, note the varied orientation of inductors, in order to minimize magnetic coupling to other nearby inductors, by orienting the field generation at 90 degrees.

IMPORTANT NOTE: This is NOT a generic midrange crossover for the PT5010, but specifically tuned to the behavior of the PT5010 in the sub enclosure previously described. Change that, and modifications to components will be needed in many cases.

[JonMarsh]

Been a lot of distractions this weekend, especially Saturday, but the new WIP test build for the TPL75 tweeter was completed this afternoon. Slow work takes time. Of course, on the Internet, it's not real without pictures, and trust me, I do not have a graphic AI to generate a fake version of a crossover build!





Now, that 3.3 uF Solen in the center left area of the board is an interesting little film and foil part, you wouldn't believe how heavy it is for the size. I would like to have tried the 6.8 uF version of it for the C42 input cap, but you know how things go these days- "Out of Stock", and no re-stock date or notification available.

Sigh...


well, if those 1.2mH inductors DO show up tomorrow, then I'm pretty close to the next major complete crossover check.

[JonMarsh]

Many other important issues to work on this last week and a half, but progress on those, and actually got back to this project a bit yesterday afternoon- some tweaks done on LF crossover last week, but not "field tested" yet (today hopefully), and some tests on adjustment to MF crossover, including a pad configuration with one "trim resistor" position that is connected via the output terminal block, modeled and tested two weeks ago, but got diverted with other activities and not reported. Plus, ordered more tuning parts, and those came in, late, but at least they arrived Thursday and Friday. Some for the Ardent D build update, too.

Just a little tease, testing the mid+tweeter two weeks ago with the update to the midrange crossover and the new TPL75 crossover board shown above. I didn't have the exact pad tuning resistor I wanted, but this is very close, and usable if a typical voiced response is desired. The way I set this up, if one pulls the "tune" resistor, then the mid defaults to the upper range of a response window (not to full midrange sensitivity) as the trim resistor is actually connected in parallel to two other resistors built in to the crossover. Just an experiment... and the new selection of parts arrived yesterday.



The new LF roll off filter was a bit underdamped at the corner, and I already have a modification worked out and built, but will need to be measured next- adding a cap and changing one resistor value. Models the way I want in VituixCAD, so, cross fingers.

This is the last measurement which confirmed the fix is needed.

In this frequency range there are floor effects, of course, more apparent with this 1 meter measurement, responsible for some of the ripple in response compared to what the drivers actually are doing.

Dang, but this has been a long winter with lots of distractions...

[JonMarsh]

More distractions this weekend, didn't get back to this when I expected to, but this afternoon I was able to- the morning was spent on the Ardent D update with the Vintage RS52AN's.
Next will be fine tuning some cabinet damping, and fine tuning the crossover to address a few regions... nothing I'd call major at this point. Of course, you might!



As I expected from the previous MF + HF measurements, things are a bit "warm" from 300 to 500Hz, maybe 700 to 1100 Hz. I need some polar measurements next to assess the overall voicing balance, and perhaps calculating some RMS response profiles over certain forward angles. And the presence range between 1500Hz and 4 kHz looks a bit soft, and sounds that way. I expect that will be straightforward to address.

What is interesting though, is how resolved the midrange is anyway- let's just say very "lucid", even though not forward in the presentation due to the response issues noted above. Nickel Creek's harmonies and overall tonal structure was very clear and voices and instruments resolved, though it would be described through the test speaker as being "laid back". This of course is due largely to the implementation of the PT5010, as well as the TPL75, and their very low HD. In fact, a point I'd note is that at a modest to moderate SPL they don't sound "loud" in a conventional sense because of how clean things are. And then a bass or percussion part kicks in and I realize that, umm, yeah, this test system is putting out as bit of SPL.

Encouraging.

[JonMarsh]

There has been a lot of non-audio stuff on the agenda of late, but I've gotten a few more tests done and am exploring some additional options on the low frequency side, with regards to cabinet design.


The MF+HF side looks pretty solid at this point, the most recent level tweaks turn out to be on the money for the intended targets...

The PT-5010 midrange with crossover by itself...



And the combination with the TPL75 tweeter:



Now, pulling the LF in to this, I'm going to be checking out some ideas this week... two issues on my mind:

• As I've seen in other projects, like the initial Ardent, larger enclosures often show evidence of standing wave resonances on the large dimensions- for something like the original Ardent, a ported design with only wall lining, this shows up in the impedance and response curves. I think I'm getting something like that here also.
• I'm pretty convinced that my current build is larger than I need for the RSS210HO, sized as it was for the RSS210HF. Which brings up the question, how much can I shrink it? Because this big cabinet with all drivers loaded sure is a PITA to work with, due to both the size and weight.
• Back in the 80's and 90's I often did some semi heretical stuff, like stuffing bass reflex cabinets. I think it's time to try that again. In point of fact, since the model data for RSS210HO seems to work OK in both VituixCAD and Unibox 4, I've done some modeling...
• And today will test my single driver + PR cabinet.
• And have ordered some knockdown cabinet kits for the HO from PE, so I can prototype this for a 4 driver set with good isolation, and adjusting the cabinet volume downwards.

Here, two RSS210HO wired in series, in 30L. Stuffed.



This is 1/2 of the LF system- just two RSS210HO. Full system is two of these series arrays in parallel, with +6 dB output.

The smaller enclosure requires upping the PR mass, to about 350g; this works perfectly for my SL26R XM003 on hand, as well as the RSS265PR.


Note the excursion at this power level: just 3mm peak, out of 12mm rating. With 4 drivers, for 108 dB.



Dhar and I had some messaging about smaller footprint tall systems, including discussing Tidal Audio and my yet unfinished Kurosawa project (waiting for me in storage, all the parts and cabinets)

This included looking at a high end Tidal system which like many other top of the line products, incorporates a woofer module below and above a Midrange-tweeter module. The LF to MF crossover frequency is higher here than might be optimum for this approach, but with the new test cabinet build parts ordered, we shall see what we shall see. It might involved flipping the MF-HF cabinet around vertically, with the mid below the tweeter. I need to do some Shapr3D sketches and see what this might look like.

I'm hoping that the overall system depth can be reduced from the current 25" to something more like 15-16". Of course, as a former colleague and I used to say often, "Hope is not a strategy". But investigation and testing is.

[letiennam]

I would like to repeat a familiar saying: slow work takes time. But progress is progress no matter how small they are, they all matter.

[letiennam]

back to topic, can we add some bracing to reduce standing waves?

[JonMarsh]

OK boys and girls, some "subtle" comparisons to start the Hump Day morning off with - just impedance plots for now, two test cases;

• Single RSS210HO-8 woofer + RSS265PR with zero add on disks, lined walls (Denim insulation) versus lined walls with Acousta-Stuff filled interior
• SMJ-40 test enclosure, 4x series parallel RSS210HO-4 + RSS265PR with zero add on disks; acoustic barrier lined walls with a few pieces of fiberglass stuffing, versus the same configuration but the front section of the cabinet stuffed with Acousta-Stuff.

You know what they say about the devil in the details... I find impedance plots quite interesting...

================================================== =======

Single RSS210HO-8 + RSS265PR

Lined





Stuffed







==============================================

SMJ-40 Lined- didn't have this one without the LCR network - recollection from data with lower tuning is that peaks were higher.





SMJ-40 Stuffed






SPL measurements later today.

[letiennam]

It seems that the stuffing has worked. The speaker's impedance peak at Fs has decreased significantly and the resonance at about 350Hz is no longer there.

[JonMarsh]

Yes, it has, in more subtlety noted ways- I often pick a simple item like the level at a frequency of interest (say, 50Hz, where in the big cabinet there seems to be internal standing wave action) and note any impedance shifts.

[JonMarsh]

Well, if all goes well, according to UPS the knock down enclosures I ordered for creating some LF tests for the RSS210HO-4 in smaller volumes with PRs (probably the Seas SL26R I have, which are already setup with 350g mass) should be here no later than 4 PM. UPS says they're loaded on a truck in Nampa for delivery already...

Now, if only there were two or three of me to assign to tasks and keep up with the various projects on hand... I still haven't gotten the hang of this "retirement" biz...

And measuring the SPL for the two test configurations on hand is also on the OmniFocus Task list... plus setting up the 55" TV monitor when the polarized power cables arrive... and I sure do need to get back to the updated crossover builds and tests for the Ardent D's...

[JonMarsh]

UPS delivered both orders of knock down MDF cabinets, plus the Acousta-Stuf.




I'm getting re-organized today to setup for assembly in the "workroom" (my spare "bedroom", eventually to be A/V-music room). I did a quick calculation for the net volume per each enclosure, minus the volume of the woofer and PR- looks like about 18L.

Heavily stuffed, might look something like this...




There are a variety of ways to flatten that out, from boundary placement distance to inline passive EQ. But, -3dB at 35 Hz isn't anything to complain about - I'm just wanting a flatter low mid bass than I've been getting with the big single cabinet so far. I also need to test it since having stuff it, just to see...

[JonMarsh]

Man, distractions of one sort or another seems to be the order of the day- especially with a major re-org of the living room and work room areas under way. And the living room bit just to setup the TV for my wife... with necessary associated electronics. BD player arriving today. Polarized power cables came yesterday for the TV.

BUT, I do have some data now on the stuffed cabinets, and it's interesting, more effects in areas I didn't actually anticipate...

Let's go with the single driver + PR cabinet first- not really much surprising there, except that it was an 8 ohm HO driver, which is not what I recalled ordering at the time!


This is in a PE MDF knock down cabinet, 28L, cut the front panel for what you want. PR mounted on the back- RSS265PR with no weights. You can see the impedance plots in Post 1075, Polk LSi, Sony ES? above.

SPL, on axis, 28" from baffle



SPL, QNF



RSS265PF, NF




No surprises here, single driver setups are nice and straightforward usually. Baffle step is seen in the distant measurement, goes away in the QNF. where you see how the driver would be expected to measure on a more or less infinite baffle.


Put in a column of drivers, and things get more complicated... including where to choose to do measurements. In the earlier measurements, I saw stuff going on that I thought was due to cancellation from out of phase recombination from other drivers in the array- didn't quite turn out that as expected.


Applying the KISS principle, I'm just going to post two key measurements:


Array Center, microphone at 1 meter, positioned at the centerline between the 2nd and 3rd driver from the top:

This is more extended and flatter than with the cabinet mainly just using the Acoustic barrier foam for lining. Would seem to indicate internal reflections in midrange causing unexpected issues.

Center Top Driver, positioned at 1meter from the center of the top RSS210HO-4:





This is quite a bit more extended and flatter than for the cabinet previously just lined with Acoustic Barrier foam. Hmmm...



I do recall doing all my bass reflex builds in the '90's with stuffed cabinets. I don't recall exactly why... (geez folks 30 years ago- can you remember what you normally ate for breakfast then, unless you're still eating it now? I'm not!)


OTOH, the response at the center of the array stuffed is interesting enough that I'm going to finish assembling this new batch of smaller PE knockdown cabinets intended specifically for the RSS210 series, because I'm curious if there is any potential for smoothing out things even more having a two driver LF cabinets top and bottom. Note, these will be about 18L net per driver, and I expect to use the more weighted PR configuration mentioned earlier, due to the smaller enclosure size, as modeled above.

OTOH, I suspect that even this current stuffed big cabinet will resolve some issues I was seeing with response and mating to the mid with just the lined implantation.

Hope and crossing fingers is not really a strategy, but there is enough data to point matters in a reasonable direction at this time...

[JonMarsh]

Man there has been a lot going on, and today is no different, it's a monthly Costco shopping this morning!

BUT!!

I did finally get things organized in the glue up work room (converted bedroom) and before heading out to Costco shortly started gluing up the new test concept PE LF cabinets for RSS210HO.




I'm hoping to get two cranked out fast and loaded for bear wired in series to test the last modeling concept using the SL26R PRs with 350g mass, and if things look as expected, then the other two.

Then full scale measurements in both a stacked configuration and a split stacked configuration. These are a nice size, as just 2" wider than the original LF and MF-HF cabinets, so testing out some ideas should be straight forward.

This may/should point to a smaller shallower system configuration, (one I can implement by cutting off the front of the MF-HF cabinet) and possibly might be interesting in a split LF mode, two each top and bottom, with the MF-HF in between, likely turned upside down from the current configuration.

Now, if I just had an assistant I could pawn off all the other activities and chores on... like nutritional work for friends and book reviews!

[JonMarsh]

First pair of HO basic cabinets glued up, except FP not mounted. Starting second set of front panels, then plan to do the threaded insert installation for all front panels, then start the main cabinet glue up for the second pair. Then route holes for PR's on the back- this set I'm doing for my SL26R XM003 10" PRs.

I'm hoping for good progress this weekend...

[JonMarsh]

Well, this weekend is nearly done...

Keeping in mind that this is sort of a side experiment, I have to admit I'm a bit conflicted about how much effort to make with the details of the construction - this may just be a brief side excursion to check some ideas, or it may point out the path to a substantive change to the WIP, if the results justify it-

And of course while building a really deluxe set of cabinets would be in order EVENTUALLY, it might reasonably be desirable to do this in a manner so that I live with them a year or so, and wrap up some other ongoing efforts before getting back to a "deluxe" version...

The assembled front panels needed to have outside and inside epoxy drips cleaned up after hardening for a day...











These aren't the greatest quality MDF knock down cabinets I've seen from PE- the dimensional accuracy and precision is fine, but this is not what I'd call cabinet grade MDF. But... needs must.


Here, the enclosures just minus the front panel, waiting to be cleaned up.




It's a straight forward process, just a bit tedious on four cabinets! and all 8 seams on each cabinet...





But they're all done...

Next steps are drilling and installing Rampa inserts on the front (yeah, no wood screws, investing in being able to mount and remount the drivers if I decide to finish up the cabinets a bit for mid term duration use).

Then routing through holes on the back for the 10" PRs...

I'm giving serious thought to making a joining panel on the back to aid in linking the cabinets together in pairs, and routing holes for the PRs that are the outer rebate. I have a lot of BB ply on hand, purchased just after the invasion of Ukraine when sanctions were announced.

If I do more finishing work, it will probably be to expoxy coat (System West at brush on density), sand and matte black paint for now. That will likely be deferred for now...

[JonMarsh]

I sure am glad I'm engaging in "fast prototyping", because it sure seems to be taking forever at times!

But here's the first of the individual woofer cabinets going together to make an LF pair...



I sure do wish it was warm enough to glue stuff in the garage, but 40 degrees doesn't work for this Bob Smith Industries Epoxy I've taken a hankering to lately!

[JonMarsh]

2nd one is glued up now, too.

[JonMarsh]

Prepping front panels is SO much fun! Actually, when you have a straightforward way of getting it done, it's not bad at all.

In this case, it's like for the big cabinets- using an RSS210PR as the drilling template with a 3/16" bit, using an extra bit to lock the location of the PR frame after drilling the first hole, then after drilling all the basic pilot holes using the PR as a drill guide, then pulling off the PR and opening up the pilot holes to 1/4", to match up with the Rampa M4 threaded inserts. Fortunately I have bags of those, literally... went on a rampage buying them originally, quantity discount, and the hole sizes for the RSS210 series drivers just work really nicely with an M4 bolt.

[letiennam]

progress is being pushed very fast.

[JonMarsh]

Trying to, but there are a lot of other tasks going on, too.

[JonMarsh]

Now, something I feel compelled to mention, regarding the newer PE knock down MDF cabinets - compared with the original Denovo cabinets, the MDF is not the same grade. I'll get by for what I need to do, as regards testing out a concept, but I sure wish they were more like the ones I got a couple of years ago- for example, this one built for tested RSS210 + RSS265PR. Compare this with the image above. Especially in the core, but also in the consistency of color and grain at the surface. No comparison.

[JonMarsh]

Well, folks, the SMJ Intermountain Prototype Development manager has given this some further thought, and is just getting more and more creeped out by the quality of the MDF routed through for the driver rebate in the front panels of the PE cabinets...

So, a hunk of my favorite Maple ply was just ordered, enough to do front panels for the two HO test cabinet pairs, with a continuous panel on each pair- and having oodles of vintage BB ply on hand (pre-Ukraine Invasion) this will also mean sheathing for the sides and the back.

Hmph.



That's what happens when a grumpy old man starts thinking about stuff and is in conflict over whether these could be purposed for a personal build without a complete reset and rebuild if they turn out interesting acoustically...

[JonMarsh]

Of course, the next question is, do I just eyeball and seat of the pants do this "upgrade", or should we get out Shapr3D and spend time documenting it all right now? Part of me wants to do that, and another part swamped with various activities figures that this is simple enough to improvise using my typical cutting techniques for rectangular enclosures with ply like materials...

[Steve Manning]

Jon you need to see if you have a local lumber supplier ..... not the big box store version. Get some cabinet grade MDF, I'm presently using Medex MR MDF, which is a moisture resistant MDF. You can see in the pictures I've posted how clean it machines.

Though I'm betting you were just looking for an excuse to buy some of that rock maple !! 😁

[JonMarsh]

Yeah, I wanted a sure thing with the Rock maple. but you're right, I should look for good MDF locally, too.

[JonMarsh]

Yeah, if I was going to do these from scratch, I'd go that way... but you hit the real issue, I just can't stay away from the rock maple ply for front panels!

The way I'm seeing this test build now is taking some composite boards I brought back from CA last June, that are BB ply with high density composite 1/4" layered on both sides, using that as an outer panel for the back, routed out like a rebate through and through for the PRs, and running up to flush with the MDF tops, than putting tops on with just BB ply, flush to front and back and MDF sides, then putting on BB ply sides going up flush to the BB Ply top. Last thing will be rock maple ply front panels, with round over, flush to top, sides, and bottom.

That's my plan, and I'm sticking with it.... for at least the next 30 minutes, maybe 45!

(the maple was ordered yesterday, should ship today, and everything else is on hand...)

[JonMarsh]

Fabrication progress continues for the new LF test concept...







Note that there will be another back panel layer approximately 1-1/4" thick which will set the driver rebate and provide standoff for the passive radiators in movement and storage.



But I do not have confirmation of shipping of the maple ply stock; I noted in ordering process that the shipping origin appears to be Canada... this could be problematical.

[JonMarsh]

Good news- the maple panel was shipped on Friday, but they just "forgot" to send me a notification. Followed up this morning, and now know it should be here by Wednesday.





Pondering a few other tweaks to these concept test enclosures, just fabrication quality stuff, not really acoustical. Fortunately I have all the materials in stock at the SMJ Intermountain Prototype Fabrication Facility (SMJ-IPFF) already...

[JonMarsh]

Made progress on cabinet gluing and panel cutting yesterday, collected together my M6 hardware, related M6 footer stuff from PE (their M6 inserts are not very goodly, to put it mildly), and located my likely footer solution, previously purchased, but also had an "Oopsie!" of sorts!



I ordered the maple panel "too quickly" and didn't double check the part number, so I got the same panel as used for the original LF and MF-HF builds... which is NOT wide enough!

well, another panel ordered yesterday, doubled checked, and hopefully may ship by tomorrow.

AND, I did get in another 4 RSS210HO-4 drivers yesterday, plus another set of the knockdown cabinet kits, presuming testing the first lot is promising enough to go stereo... (go stereo or go home?)




Have cut 1/2" HD MDF panels to go over the back to give a better mounting material for the M4 Rampa inserts for the PRs, but meanwhile, need to cut the backside panels which will form the outer rebate holes for the PRs, and side wall panels. Then the single layer side walls to skin the cabinets in.
Sure is nice having this big stock of BB ply on hand... (after the Ukraine war started, I literally went into the Boise Woodcraft store (reportedly the largest in the country) and bought them out on 30" x 58" x 18mm BB ply. They restocked from stuff in their warehouses, at the time, but mostly just sell American Birch ply now. Clearing out some Finnish birch ply. Supply for that has dried up.

As you may have noticed, I'm doing things sort of backwards for this test build. No 3D drawings yet. If it works out as I think it might, then I'll go into documentation mode.


Yeah, maybe I should have started that yesterday, but a big hunk of time was spent going out and looking at and buying Apple trees and some other landscaping shrubs.

[JonMarsh]

Tool Time Tales:

One of the most useful router setups for cleaning up the precision on these ad hoc builds:




It was also used a lot for making layered panels flush in the original builds... very useful for those of us who just have saws and routers, no CNC mill.

Now I'm ready to glue the HD MDF backside panel for the PR mounting plane.

[JonMarsh]

Step by Step... panels are rough cut then through holes matched up with my flush panel router shown above.



A PR through hole back panel for the other enclosure pair is in progress, as well as the rebate relief panels. Once those are done, BB ply side wall covers will be cut and glued up.

WIP is WIPing along, though not as fast as I would like- a gut bug this morning reducing my productivity!


In other news, the "correct" size maple panel will be delivered on Tax Day, if all goes well!

I'll readily concede this is a weird ad hoc way to make these test enclosures, but it's expeditious and the enclosure is turning out to be very stiff.

And, going out on a limb a bit, I did order a second set of PE RSS210HO knockdowns...