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

[JonMarsh]

Action shifted to the additional back side pieces, to outline the PR (like an add on rebate plane) and to make it possible to lay the cabinet down temporarily on it's back. Mundane stuff for all the tool time jocks, but I'm sharing for those who are more wires and sparks kind of guys like me.

This is where I used my 18mm BB ply stock from Woodcraft... first rate material. Ripped to 13" on the SawStop, of course, just like the previous 1/2" MDF for the threaded inserts to mount in backs that have been routed out to the through hole diameter using a follower bit in my DeWalt shown above.

The long rip boards have to be cut down to a length to be trimmed after assembly- say, 28", compared with the nominal 27.5" length of each LF cabinet assembly.

This is where serendipity comes in, as my Bosch miter saw purchase based in 2020 comes through, and is able to handle the 13" crosscut.




I own several miter saws bought over the years, but this is by far the favorite and most useful.





Then I have to take the four pieces and epoxy them up into 36mm thick pieces using System West 105 + 205 hardener.





The two Bessel clamps are used to be sure the sides are lined up flush and don't drift when applying the other clamps.

This afternoon I'll switch this assembly out and epoxy up the 2nd pair. Tomorrow will be routing and round overs for the PR clearance holes.

[JonMarsh]

Contingency Planning

If this offshoot enclosure concept does pan out, well, I've been going through the parts bins again, came up with a possible contingency solution for cabinet footers- this is based on some Chinese parts that looked interesting and reasonably priced that I bought 5 years ago- of course, reasonably priced and Chinese apparently will not be part of our future for a while...


So, what I've temporarily identified as a useful path forward for testing includes the basic mounting bar and cones, plus adding in some Rampa M6 inserts, and some appropriately sized M6 hardware- nothing exotic, Hillman parts you can get from places like Lowe's hardware, for example. Or mail order from Ace Hardware- stores around here don't carry these bolts.

Side View




Bottom View





Perspective View

[JonMarsh]

Making some progress on the glued up rebate backside panels... got side tracked hunting down some previously purchased tools for later stages, like drilling the pilot holes for the M6 threaded inserts- found the Rockler drill angle support accessory bought last August, and some other key bits.


Both of the 28" long panels were marked up for locating the PR center holes in order to create rebate holes at 5.75" radius. And of course the old reliable Porter Cable circle router setup was unpacked again!





This picture with the initial first cut completed for one driver shows how the layout works... centered at 6-1/2" from the panel centerline.




A real key to making this go smoothly, besides the circle router adapter, is the solid carbide spiral cut bit- stays pretty cool, considering, and makes very clean cuts.



And now both panels have the initial routing cuts done-
This will be followed by cutting out the center circle with a saber saw, and routing the remaining hole height flush with a follower bit.

[JonMarsh]

Almost finished with the PR rebate panels...

The Bosch router table made fairly quick work of cleaning up the inner route border...




And here both panels stacked, with the rough inner cuts complete. As you might imagine, they weigh less than half of what they did as complete panels!

[JonMarsh]

Some Tech Specs on Rampa M6 threaded inserts.

I've really developed something more than a bit of fondness for the Rampa inserts. You may have to hunt a bit online to find a distributor with them in stock. Here's the basics on the M6 variation that I've been planning to use with several possible footer and base board configurations for the SMJ-40/Saint-Saëns.

[JonMarsh]

Step by Step


Visual alignment check, panel centered




The PR rebate lip will be given a round over.


Glued and clamped

[JonMarsh]

First rear outer baffle glued up, another one should get done today...
And something else about this experiment I probably should have mentioned...





The "something else" refers to configuration options- while I'm primarily looking at the over and under LF configuration, with no long interior cabinet dimensions, another possible option of interest is just using one LF cabinet for a more budget oriented build with less work.


You see, for the dual LF cabinet four driver option, the drivers will be the RSS210HO-4, wired in series parallel resulting in a net four ohm load with some sensitivity gain, and a Unibox predicted response like this:



But, hey folks, Dayton makes an 8 ohm version of this too, (unlike the HF series), so a single LF cabinet configuration is possible, with two of the RSSW210HO-8 wired in parallel.

It models like this, still a four ohm load (basically) for the crossover, but of course about 5 dB lower sensitivity. The series-parallel four driver configuration gives a theoretical sensitivity boost of 6 dB, but part of that is lost due to resistance and differences in driver T/S parameters.





This would reduce the size of the system and build complexity and cost. Puts it more in the Wavecor Ardent range of things, but at higher sensitivity, and a "bit" more construction complexity!

[letiennam]

I hope it is also used for Ardent the poor man's version, as you had a good find last year with the SB15CAC. I also recently tried to simulate a serial RSS210HF-4 on Vituixcad and got good results with a 54l sealed enclosure. What will happen when I make the cabinet for "love child" by Wavecor Ardent and Natalie P

[JonMarsh]

This cabinet design for the LF concept test is ~40-42L net, so it is very compatible with the Wavecor Ardent concept. Here, it is specifically setup for a passive radiator system with a smaller volume to optimize coupling and minimize internal cabinet standing waves.
In this case, a two piece construction for the mid+ tweeter on top should focus on a low diffraction launch design for the midrange and tweeter. Something akin to the upper section of the Wavecor Ardent would be a good starting point.

Another interesting point of note, is that Parts Express is now listing the Peerless DA25TX008 as a new part available in early May, seemingly without the high volume requirements previously enabled for most Peerless parts. This would be an excellent tweeter choice.

[JonMarsh]

Minor update- more System West epoxy supplies and metering pumps arrived today, and the raw BB ply side panels were ripped and cross cut for the two POC cabinets. If all goes well, tomorrow will see trim routing for the outer back panels and gluing up the first of the side panels.
Today was an unusual weather day, with high winds still going in clear skies, up to 55 mph.

[JonMarsh]

Sanding and prepping for the BB Ply side walls is finished on one cabinet, and now one BB ply side wall is glued up....





As always, no claim this is the best way to get it done, but it's what I can manage with what's on hand and trying to do "rapid prototyping" (Hah! as if!) for a moving target...




But, yah know, kinda kludgy perhaps, certainly an inelegant construction plan, but these boxes are very, VERY stiff! and panel resonance is way above the operating planned range of operational frequency- and there shouldn't be any standing waves in the range of interest.

And SpeakOns should be here tomorrow.

[JonMarsh]

Who says Sunday is a day of rest?

2nd cabinet, gluing 1st side wall....





1st cabinet, trimming sides to fit





1st cabinet, more cleanup





1st cabinet, ready for PR inner round overs and fitting a front panel (yet to be fabricated)

[JonMarsh]

A lot of summer startup work distractions limiting my time on this, but some progress...


Of course, front panels have to have a plan...




Cutting the 59" long board into "bite size" pieces is a bit tricky, but the Bosch can handle most of the 14.5" width in one pass... the end test for precision, as I related to Steve, is that when I stacked the boards on top of each other, they were totally flush on both ends...




Now, just to reiterate, this is definitely a CNC free zone when it comes to fabrication, not planning:

[JonMarsh]

OK, pretty CAD drawings are necessary, for the most part, but not sufficient - must make some saw dust, too! So it's time to break out the Porter Cable router I have set up just for circle cutting.

Measuring the radius of the cut is very easy with this setup, but still, the old adage about measure three times (or was it four? 😉 ) still applies.




The 3/8" depth for the wide rebate cut (Whiteside 3/4" bit) is easy to do in one pass.




The thru hole cut with a 1/2" solid carbide spiral up cut bit requires close to a 3/4" depth, so three or four passes is a fairly reasonable approach, using the cutting depth stepper, and setting for the end point depth of cut.



For the radius on the through hole, we're looking at "about" 7.3", I.E., 185mm plus one or two.

Here's a good visual on what that looks like when completed to the point where the rough opening can be cut with a saber saw, then a follower bit used to clean things up (tomorrow!).




As always, it's just a matter of taking your time to be accurate and avoid yield loss.

For those of us like me that are more wires and sparks kind of guys than polished production wood workers, the extra time and care certainly pays off!





(Psst! He needs to plug in a dust extractor like my DeWalt vac to that miter cut-off saw!)

[JonMarsh]

Too much landscaping work yesterday, but got in a little bit of time earlier in the morning! After all, it's supposed to be Sunday Funday, right?

This pic is for all those folks that say my pictures are too clean, don't show enough sawdust...



Of course, my favorite smaller DeWalt router with the Woodpecker STABILMAX trim base, which is absolutely essential to getting good results when working on an overhang like this.

And a quick test fit shows my hole fixture measurements are right on the money. The rebate size is larger than might seem to be needed, just like the ARDENT D, as this facilities getting the driver in and out, and the gap can be filled with a wrap around gasket as I did for the Ardent D. But that's a little too "finished" to worry much about for this design study phase!




Next will be the inside round over, and installing the Rampa M4 inserts.

[JonMarsh]

OK, this part of the work reveals what I don't like about the RSS210HO design- the very narrow mounting baffle and how close the mounting holes are to the through hole. Definitely limits your choices for bolt sizes and threaded inserts if you want to go that way- most 8-32 threaded inserts are just too big. That's why I use M4 bolts and Rampa inserts.

Note that most Dayton 8" woofers have part numbers like "RS-225", and the mechanical dimensioning that implies.







So, rules of the road:

1. The through hole must be sized as small as possible, to give more meat for the mounting baffle and inserts- this means as close to 185mm as possible.
2. Precision techniques must be used for drilling the through holes for inserts.
3. In my case, I use an RSS210HO-PR as a drilling template
4. Use a square to locate and align two opposite holes on the PR
5. Drill those carefully with 3/16" bit, and insert bits in the holes to hold the "template in a fixed position
6. Drill the other through holes with 3/16" bit
7. Remove the positioning bits, and then use a SHARP 1/4" bit on slow speed to open up the 3/16" hole to the 1/4" pass through needed for the RAMPA bits.

If you want a faster easier method, talk to Steve- get setup for CNC- I'm just an old wires and sparks sort of guy!


Drill hole alignment:





Pilot holes:






Inserts Installed:




this particular maple panel was harder and drier, so a little extra care to avoid splintering was needed.

[Johnloudb]

Really cool design and build here … just looked through this thread. Jon, your speaker builds are always creative and very well thought out … and I do love sound of planar drivers. I plan to add some tweeters to my dipole build at some point … planar or AMTs , for 5KHz and above.

Your productivity is in another realm! … will be following this … I look forward to your listening impressions.

[JonMarsh]

Thanks for the kind words- this would have been faster except I had been multi-tasking a lot of stuff, including some other projects at different points of development. I hope/believe this new LF test build will resolve the frequency response linearities in the low end range. Should know pretty soon...

Next up will be preparing the front baffle holes for the deck screws (stainless steel, of course) to provide clamping and attachment force for the center of the front panel to the middle cross panel in the cabinet...

[JonMarsh]

Got to play with my Rockler precision drill fixture today...

I wanted to drill some through holes in the front panels for inserting the deck screws that I wanted to secure the glue clamping in the center... for these stainless steel deckscrews I'm fond of...


I don't know why, but you can't buy these at my local hardware store...

Here's my compact DeWalt drill setup with the Rockler drilling guide



Precision angle drilling is a breeze with this setup for those clamping screws...





Results as desired-





Now I just need to do the side bevels, then gluing up the fronts to each test cabinet.

[Steve Manning]

Looks like that setup works nicely Jon!

[JonMarsh]

It’s the best thing I could come up- with for when I’d like the precision of a drill press, but the dimensions and layout make that impossible.

I’ve had this for couple of years, but first time posting about it.

[Steve Manning]

I was wondering about your drill press but figured the board was too big.

[JonMarsh]

Last basic step for the front panels before mounting is cutting the side edge bevels- pretty easy job on the SawStop job site saw.

I often work with an open blade like this because of the safety of the contact detection circuit and blade clamp- and yes, I have tested this, which of course expends one of the blade lock units when ever this occurs; it has to be replaced. These cost about $99.





Here, after one bevel cut has been completed:




Yes, this is a reverse angle 80 tooth blade designed for smooth cutting in hardwoods and melamine.



Here, bevels completed on both sides of the second front panel. I'll do some light sanding cleanup, then assemble the front panels on the basic test cabinets.

[JonMarsh]

Last step before panel assembly is counter sinking the panel center through holes for the deck screws. In a typical deck or gazebo assembly operation, the wood is soft enough that it can just push in an indentation, but with this maple, a specific countersink operation is necessary.

Here's the bit I use- it's typically sold for cleaning up the inside of cut pipe, such as copper water pipe, not for wood working.




Installed in the drill guide jig and the jig adjusted for drill depth...





check counter sinks...

[technodanvan]

Does the Rockler version of this have an integrated depth stop? Looks like your countersinks are pretty even, even if you eyeballed them!

[Scareurpasenger]

Love the rockler mini drill press. It has two depth stops, one on each side. The lazy part of me liked the drill guides from gator for something quick.

[JonMarsh]

Yes, it does. Countersinks are a bit tricky, considering a minor difference in depth can be a larger than desired diameter difference. Of course, as hard as the maple is, it's fairly easy to "go slow" and not get too deep.

[JonMarsh]

Finally got some time this morning to prep the one of the cabinets and glue up the first front panel. Been a lot of landscaping work and yard stuff going on, plus interviewing pest control firms and selecting who to work with.

Cabinet front edges are sanded up nice and flush and smooth...



Of course, I marked with pencil on the side where the dual cabinet joint is in the middle, and the same for the location of the screw holes on the side, to facilitate accurate line up.

After mixing up the Bob Smith Epoxy (my favorite for detail joint and edge work- nice and viscous, and 30 minute working time, slow cure), the FP, which is sized very slightly over-sized, to be trimmed flush, is installed and clamped on the corners with Bessy clamps. The I'm ready for the deck screw installation with an S2 bit; here you can see the tooling. of course, DIYW based on your own preferences.




Here, a picture with all the screws installed- eazy-peazy, with a good plan and tools.



This will sit up for at least 24 hours before doing the trim work, then installing a SpeakOn socket for the wiring connection.

[JonMarsh]

Shift in weather, much colder, had to move gluing back inside today...

Day of rest? Well, maybe after noon- the glue job and some other errands and tasks are done, but I got an early start!




But, hey, I figured it would get done- even if I had to draft ET to help!

Because, after all...



May the Fourth be with you!

[JonMarsh]

A lot of infrastructure tasks yesterday, but today should have some fun, as wifey will be away helping a friend get ready for her daughter's college graduation party...

Time to break out the "heavy guns", for the front panel fitment milling.

Anyone recognize this, and what the original brand was before the division was spun off?






I've got another one of these that says "Hitachi" instead of "Metabo"- I wish these folks made a wider selection of routers, because when it comes to sheer power and smoothness, this bad boy is tops in my experience. But then, it is beastly in more than one way, being the heaviest and bulkiest of routers that I own.

Of course, "pre-loaded" with a solid carbide spiral uncut bottom follower router bit, which is just what I need for trimming the maple ply front panels.

Need to get a vac hose adapter sorted out this AM, but after than, wish me luck and steady hands getting both the cabinets done.





PS: I'm making a long shot bet, and have already started assembly of the inner knockdown cores for the next pair of POC V 3 LF cabinets. I just have a feeling about this, after reviewing the single cube style driver measurements.

[JonMarsh]

OK, did some gluing in the morning, and some route timing this afternoon!

Drum roll....
.
.
.
.
.
.
.
.

Everything went fine. I was a bit nervous, and quite careful. I hate yield loss at this stage.

And some points I should probably iterate again:

• For a build with this kind of thick dense front panel, this is a risky way to do things.
• Ideal situation would be CNC milled parts, everything dry fitted and checked before a single dollop of epoxy is mixed up.
• But this was an evolving experiment, decisions made as I went along, and not always with construction techniques that I would expect to result in the highest precision.
• Doing a routing trim like this means the front panel should be (theoretically) custom fitted to the dimensions the cabinet "accrued" during assembly. And this was the case.
• Of all the routers and bits I have, this is the only combination I felt somewhat comfortable using for this front panel trim- it's a beast of a router, very low vibration, very high torque and excellent speed control, and the spiral cut follower bit is pretty much as good as it gets, and the 1/2" side makes torque management easier (IMO).

BTW, I weighed one of the cabinets before starting this operation- 71.1 lb. It's lighter than the single large cabinet, but combined they may be heavier.

For perspective of the relative size of the cabinet and tool:



First pass on a side, and a fitment check.




First pass on an end top/bottom side:





Sanding? Who needs sanding?!?




The results, if anything, consistently exceeded expectations of this wires and sparks guy...

[Steve Manning]

Nicely done .... that is a beast of a router that's for sure. That maple certainly seems to cut a lot nicer than bamboo.

[JonMarsh]

The maple cuts very well, but then too, the solid carbide spiral cut 1/2” router bit is the best functioning one I’ve found. The router probably weighs at least 50% more than my next largest 1/2” bit router. But, man, is the motor every smooth and torquey!

[Scareurpasenger]

Metabo makes a 36v cordless router as well. It may be more compact than typical but still handles 1/2” bits. I picked one up during the last sale and have a feeling it will be a new favorite.

[Evil Twin]

Interesting... most interesting!



My Force intuition suggests this may be the one you have purchased....




Impressive... most impressive!

[technodanvan]

I have supplemented my routers with both Milwaukee cordless models (trim router and 'regular' size 1/2" model) and have only been impressed in their capability, if not their cost. If they brought out a big boy like that Metabo I'd surely be interested as I think a bearing on my Triton may be going bad.

I still have my Dewalt corded model as well but may be interested in moving it along to a new user. I just did the same with my Makita trim router. Downsizing feels nice.

[JonMarsh]

Installed threaded inserts for the PR's- a few notes about this:

• The 1/2" backing sheet glued on is cabinet grade MDF so that there is something decent for the inserts to "bite" into
• Furthermore, the epoxy application was done to the routed panel so that the surface would be further "stabilized".
• This approach was chosen after testing several possibilities in order to get the "firmest" threaded insert feel as installed.

With the frame design of the Seas SL26R PR, there is plenty of room in the mounting plane circumference and the pilot hole spacing is pretty reasonable. Note, the standoff back panel is spaced a ways out from the pane deliberately- there is no need for it to fit tight to the PR.


You can see this in this picture taken after the initial assembly of these two panels, with the SL26R dropped in. The through hole is sized for being a snug fit. This pic was prior to the round over routing.




Here, a pic with the inserts all installed:





Next will be drilling and installing the SpeakOn connector and driver cables.

[JonMarsh]

Prepping the cabinet for mounting the Neutrik NL 4 MP connector is the last significant step in preparing for the driver mounting, wiring, stuffing, and final assembly. I'll list out the steps I used first, then do my usual pictorial show and tell.


Keep in mind I'm being a little OCD here, as I'm the wires and sparks guy, not the wood worker.

• Review the Neutrik NL 4 MP mechanical panel layout- key point is needed a 15/16" through hole for the body, and two mounting holes for #4 screws to fasten it to the back of the cabinet. Of course, adding sealant or glue is also an option for the brave of heart...
• then, be sure you have a high quality 15/16" Forstner bit, like the Freud pictured below, which has precision construction, sharp cutting surfaces, and excellent pass through space for removing the debris quickly.
• Mark the center point for the Forstner bit; this is going to be 2-5/8" from the side, and 2-1/2" from the bottom, if you use the orientation I chose that keeps the mounting holes away from the interior.
• I used the smaller lighter 2AH battery pack for this work; it makes the drill and Rockler drill guide easier to handle.
• I used my DeWalt shop vac to clear the drilling area of debris frequently.
• Use the Forstner bit to drill to the bottom of the double 3/4" plywood outer layer.
• Then I switched to a conventional 3/8" bit to drill the initial pilot hole for the cable pass through, following up with a 1/2" bit. I don't recommend using just a 1/2" bit, due to how it would interact with the MDF going in by itself. I did use the Rockler drill fixture to assure angle alignment and aid in bit control.

OK, time for some pictures...





The NL 4 MP panel layout...


Here's a pic of the Freud Forstner bit I selected:



This view mounted in the drill shows the excellent space available for evacuating debris.





Now, lets look at the dimensional location of the center of the drill hole for the SpeakOn connector: from the side and from the bottom:

[JonMarsh]

Here's how things look with the drill fixture in position and a bit of progress made on the 15/16" part of the hole (which is about 1-1/2" deep)




A close up of the view as it gets close to the 1-1/2" point:




Now, a picture of the spool of 4 conductor AWG13 cable I selected to use- the outer diameter is just a skosh over 3/8" (skosh is a technical term for extra margin often used in activities like power supply and amplifier testing, as, desiring to verify the ability to deliver a "shosh" more power.)

😏




Example: this is a "skosh" more wire than we will need for wiring four LF cabinets, if this design path is pursued.


This is the second bit used for drilling the bottom part of the connector pass through, a 1/2" bit (after 3/8") to allow easy pass of the selected LF wiring.

[JonMarsh]

And, I forgot to mention, I cut each piece of cable to 36", and will strip back for running two conductor to the driver in the upper part of the cabinet. Each driver has their own lead pair, allowing flexibility at the cabinet to crossover interface for how the crossover is configured (either series for 4 ohm drivers, parallel for 8 ohm drivers. )

[JonMarsh]

And here, one of the two connection cables:

[JonMarsh]

Progress teasers...









Ready to load RSS210HO's

[JonMarsh]

A lot of distractions, but some progress, more coming today as the wife is going out to the mall with another Russian friend.

Teaser pictures, plus some impedance data for single section and both wired in series...



The backside, 4 pole SpeakOn for connectivity. They way this got built, binding posts would have been hard to do...





HO's loaded, this becomes an approximately 100 lb bass cabinet.

Hmmm, obviously my idea to do a quick prototype of a lightweight Proof Of Concept test cabinet didn't meet all parameters...


Now, one driver measured, and both in series measured for impedance. Acoustically, they're two independent spaces.







Of course, for a complete system speaker, there will be be two cabinets; the second one is mostly finished.

The two 8 ohm cabinets will be wired in parallel for a 4 ohm system load. The real test issue is whether this eliminates what I'm guessing is a standing wave effect in the original design that peaks the LF response at about 50 Hz, as previously shown.

I'm expecting/hoping for something that resembles my first single driver and PR response for QNF and normal distance:



At one meter, the expected baffle step will occur.

[JonMarsh]

Houston, we have successfully completed preflight setup and clearance for testing LF POC V3....


Ground control ready for test...




Houston, we have ignition and lift off on initial QNF test...



Houston, receiving telemetry signals 5 x 5, initial evaluation data including distortion at 2.83VRMS is available....




Initiating 1 meter test protocol for basic far field behavioral evaluation... syncing data stream.... 200ms window with Half Bingham impulse filtering.




Data stream received and processed, 200ms window with Half Bingham impulse filter; initial evaluation pending...

LF response as expected given room positioning and expected modes impacting ~47 Hz region and 63Hz region- no room acoustic baffles, and only 1/24th octave filtering.





Houston Project Control confirms compliance with planned and expected response trajectory and behavior...


Houston, we have lift off confirmed on desired trajectory with initial Proof Of Concept LF V3 Dual cabinet build concept for SMJ-40/Saint-Saëns three way- permission to complete 2nd cabinet build and initiate 3rd and 4th cabinet build with materials already in house.

Expected next phase testing with two dual driver LF cabinets, one on bottom, one on top, and an existing MF-HF planar cabinet in between, but MF-HF cabinet physically inverted compared with original configuration- midrange towards the bottom.

[technodanvan]

Question: Could this not be accomplished with the two cabs directly on top of each other with a thick divider between them?

[JonMarsh]

Possibly, but then the MF/HF origin would be rather tall, for optimization for a seated listening position. With the existing MF-HF cabinet in the tweeter down position, the tweeter height would be about 65". That's not very optimum for a planar style tweeter (PT2522) or the Beyma AMT, both of which have more limited vertical dispersion at high frequencies, due to the source height (about 2") (imagine the dispersion of a 2" dome tweeter...)(Oh yeah, they call those dome midranges!).

Now, if you did something like Sven's HT room, with the prime chair on a raised platform, to bring up the seated ear level, then that might work out fine.

With some care, in my MOD3 and MOD4 subenclosure versions, the 2522 can have smoother response and retain fairly good off axis behavior (0-50 degrees below); part of what I was targeting was a deep enough sub enclosure to dampen some of the intrinsic peaks of the PT2522c and tuned for the flattest net response in the 30-40 degrees off axis response. Many folks don't have good enough HF hearing to notice the immediate on axis rising behavior.


Of course, in all things, DIYW!

The main goal was to eliminate the rising response in the LF between 100 Hz and 50 Hz for the FRD style LF cabinet, about 8 db altogether, and in that this solution seems successful so far. Now, many folks may like that built in bass boost, but it seems to be accompanied by audible degradations in fidelity. And now, one could say this is sort of turned into a big WMTW. Like an MTM, but related to the midrange.

With two 8 ohm parts in parallel (change in wiring after the SpeakOn connector, externally) Ardent like three way solutions are feasible, including, say, a coaxial one with the Tangband Coax. Unfortunately a number of those drivers are going to have rather unattractive prices soon. But no one will build them in America.

My resolute focus though is getting this finished- no distractions.

Reminder, this is a WIP update.

[JonMarsh]

Danny, In all fairness, I should mention that it had crossed my mind to try a straight stack up but with lifting the back of the MF-HF cabinet, perhaps an adjustable spacer, so that the tweeter/midrange assembly can be aimed down towards the seated listening position ear level.

I've got questions in my mind about how well the 425Hz woofer to midrange crossover point would transition compared with having the MF-HF cabinet in the middle, but I'll go ahead and plan on testing this setup also. The advantage of having it in the middle (in my mind) is that the focus will be more like a classic MTM for the mid to woofer crossover, and the seated response would be relatively consistent at any reasonable distance.

[technodanvan]

Thanks Jon, that does sound like an interesting experiment. I was also under the impression one could simply craft the bass bins in a deep/narrow configuration as the first iterations of this design had, thus reducing the overall height of the speaker.

[JonMarsh]

Thanks Jon, that does sound like an interesting experiment. I was also under the impression one could simply craft the bass bins in a deep/narrow configuration as the first iterations of this design had, thus reducing the overall height of the speaker.

One can, but the problem I found with extensive testing is that even with going to a fully stuffed configuration with Acoustastuff, there seemed to be standing wave phenomena (as encountered in much milder form at times in Ardent like projects) which results in a rising bass response as you go lower, peaking at around +8 db at 60Hz and rolling off below that. With just the acoustic foam wall lining, the peaking was about 12 dB. I didn't like the way that sounded... some may, of course. YMMV.

Measured at LF array center- Acoustastuff



Measured at center of top woofer- Acoustastuff




As noted at the start of the concept and construction of this POC V3 LF test, I wanted to see if there was any reason I couldn't get a response plot with more than one driver that was more like the original single woofer+PR test cabinet, for QNF and normal distance measurements. And I figured a key concept was NOT having long internal dimensions, but using a slightly smaller cubic like construction similar to the original test cabinet with relatively short dimensions in all directions.

For reference, initial first cabinet with HO driver substituted, QNF (6") and 1 meter:







To expedite that, I picked an off the shelf PE cabinet for the HO woofer that I hadn't worked with before, and built a relatively compact (in depth) dual driver cabinet by "skinning" it with cabinet grade MDF and BB ply, as documented above. (2nd cabinet is nearly finished, so complete tests are not far off)

WIP, as I often say...

[Steve Manning]

Jon what about this idea we had talked about a while back, side diffusers

[technodanvan]

I think it's more of a cabinet height thing though, is it not? Though perhaps something similar could be employed, or even angled top/bottom pieces in opposing directions?