Something New Cooking...............................

[dlneubec]

I have a rather unique design underway at the prototyping stage. It is inspired by a commercial offering. Can you guess what these items have in common and what the design concept is?

Aura NS10-513-4, Transducer Labs N26C-G, Dayton 12" waveguide(s):








Hint for those who have been around awhile, it is a bit of a return to my roots.

[JonMarsh]

It's not hard to guess how you might be putting together those pieces- I'm guessing you're NOT going to be coupling the waveguide to the Aurasound 10's, right? :rofl: What crossover frequency do you think you can manage with the waveguide?

The funny thing is, I have plenty of both the woofers and tweeters "in stock", though not the waveguide. Will be curious to see what you're up to, Dan! It should be interesting... :T


I've been wondering what to do with my NS10's, had been thinking along the lines of some kind of tower system with the Q100 KEF driver for the top end.



But....


Must not get distracted.... must not get distracted!

[gbegland]

You almost gave me a heart attack. When you mentioned NS-10, my first reaction was to think of those craptacular monitors seemingly every recording engineer used in the 80's. Whew, glad that was a false alarm.

Dan, when you said it is a return to your roots, all I can think of is some kind of an omni design, but not sure how that would work with the honkin' sized waveguide. How bout' a lower sensitivity Geddes style? Nah, I don't think so.

Greg

[dlneubec]

Hi Jon,

You are right that the WG will not be used with the NS10. However, I don't think it is quite what you are envisioning.

Hint 2: The horizontal response with a typical waveguide falls as you move off axis. That does not happen with this speaker. :B

BTW, I've done both measurements and sims on the passive XO. Even with a low dcr inductor (.17 or so), I'm not having trouble with keeping impedance above 4 ohms with a single woofer. That was unexpected.

[dlneubec]

You almost gave me a heart attack. When you mentioned NS-10, my first reaction was to think of those craptacular monitors seemingly every recording engineer used in the 80's. Whew, glad that was a false alarm.

Dan, when you said it is a return to your roots, all I can think of is some kind of an omni design, but not sure how that would work with the honkin' sized waveguide. How bout' a lower sensitivity Geddes style? Nah, I don't think so.

Greg

You're getting warm, but no, not a Geddes style implementation.

[dlneubec]

Jon,

I forgot to answer one question. The expected crossover at this point is in the 1-1.2khz range.

[Face]

Waveguide will act as a reflector for omni operation?

[dlneubec]

That is a part of the plan!

[Hank]

Face: That was my guess - waveguide opening pointing skyward.

[dlneubec]

Not quite Hank.

Hint 3: Two of the PE waveguides are utilized in each speaker.

[AdelaaR]

dipole waveguides?

[dlneubec]

No, that's not it.

Hint 4: Two waveguides are used with one tweeter!

[JonMarsh]

No, that's not it.

Hint 4: Two waveguides are used with one tweeter!

Now, that sounds positively evil and perverse! :W I like it! :T

[dlneubec]

OK, so enough teasing. Here is what I'm doing. :twisted:

You start wtih two of the 12" PE waveguides. One you cut just below the metal portion of the threads with a hack saw and then mill it down until the throat size matches the tweeter. You also hack the threads off the second WG. There may be better ways to do it,, but I basically glued a dowel into the opening with the goal of extending the waveguide up into a point to create a diffuser that looks like a witches hat. I added bondo to fill in at the bottom of the dowel and then sanded it all down to a point.

You then attach the two waveguides together such that the pointed diffuser extends just shy of the throat opening in the other waveguide. Turn this so that the point/throat is facing up (vertically) and sit the tweeter on top of it. Place this suspended above an up firing woofer at the top of a cabinet and you have a 360º dispersion horn/waveguide/omni speaker (horizontally), with the exact same horizontal response for 360º around the speaker. The waveguides are only about $13 each, so it is not an expensive experiment.

Below are some prototype photos. The concept came from the Duevel speakers here:

http://www.duevel.com/loudspeaker.htm

Below are the two mated together. You will notice the washers added as spacers. I did this so I could measure various heights of the diffuser in relation to the waveguide. I also measured several tweeters I have on hand. The two best were the Dayton RS28F and the Transducer Labs N26C-G.



The next step was to measure the horn with a base and arrive at the best edge treatment. This photo shows one of the pieces I tested the horn in. I also tested with various treatments at the edges, such as felt strips at the edge of the horn, out on the vertical edge of the wood base, with felt dots of various sizes, etc.



Here is what I eventually ended up with for the time being. The box below was from my original look at this concept and was my very first speaker design. It was the precursor to the HOSS omni and came to the original InDIYana event, I believe. I will rebuild with a new bass bin design, but this serves the purpose well for prototyping.

[Face]

Would a third waveguide mounted upwards above the woofer also help directivity...instead of creating a possible resonance cavity?

[dlneubec]

I thought that initially as well and did test it, but the measurements were really ugly. I will post more detail about that shortly. There was a fair amount of experimenting and measurement involved.

[dlneubec]

Let me review a bit more about the woofer configuration. I was anticipating one of two woofer configurations. My initial thought, since the Aura NS10 is such a great looking driver aesthetically, that I would mount the woofer firing down into the box. I would cut a hole in the base plate for the diffuser and let the woofer magnet fit up inside the diffuser.

I tested this concept a little by cutting a cardboard ring about 12" in diameter with a hole in the center to fit over the woofer magnet to simulate the placement of the diffuser base above the woofer. The measurements initially looked promising. The Aura has a vented pole piece, so I was concerned about what it would do to the driver response if it was somewhat covered. I took a second waveguide, sealed the throat opening, stuffed it with insulation and placed it over the magnet and the cardboard base piece. Still the measurements looked promising.

The second option was like the Duevel approach where a more truncated diffuser is mounted above the woofer. I fashioned this diffuser out of a third PE waveguide. This woofer did not like this arrangement at all. The measurements had big peaks and valleys all over the place, really ugly. I tried it at various heights in ¼” increments and nothing worked, so this idea was abandoned.

So I finished the horn with base, like the last photo shown above and mounted it above, with a cutout in the center so there was maybe 1/8” of clearance around the magnet, stuffed it with insulation and mounted if over the woofer, mounted to fire down into the cabinet. Unfortunately, the measurements with this setup were not nearly as good as the cardboard mockup. Nothing I did seemed to better the results.

At that point I decided to test with the woofer facing up, firing out of the cabinet with the diffuser mounted above, but without the third waveguide to disperse the woofers output. I simply placed painter tape strips over the opening in the diffuser base. The measurements now look great out past 2khz.
I rebuild the base plate so there is no hole and go about finding the optimum height above the woofer for the best raw response. I test this the same way as the tweeter waveguide diffuser by using threaded rod with hex nuts to adjust the height.

During this process, I’m thinking about how I will deal with the woofer’s 2.3khz breakup in the crossover. The on axis, front firing response shows a 9-10db peak at this location. However, I notice that measuring 90 degrees off axis in the omni position, that the peak is attenuated quite a bit compared to forward firing with the mike centered on the woofer. I wondered if it could be dust cap related and decided to play with adding some damping to the dust cap and cone. After trying a bunch of things, some of which made a difference and some not, I tried a roughly round piece of ¾” 3-layer sonic barrier, about ¾ the size of the dust cap. Bam, the resonance peak all but disappears. The driver response is maybe ¼ to ½ decibel lower at the low end due to added mass, but the response looks much improved and in later listening tests with an initial crossover, I don’t hear any negatives from the breakup with this area only about 20db down and no notch filter. I also experimented with some treatments on the opposing diffuser base and find that an application of the same ¾” 3-layer sonic barrier, about 4” in diameter, further improves the overall smoothness of the raw response of the woofer in this setup.

Unfortunately, I didn’t save a measurement of the original breakup to show you, but here is what it looks like after the sonic barrier treatment. This show with and without XO applied.



The next graph shows the tweeter response in the horn with and without the initial crossover. You can see that I’m getting a good 15db of boost at the peak of the raw response compared to the filtered response and around 18db of boost at the XO point. That should provide for a considerable improvement in headroom and reduction in low end distortion with the XO in place.



Here are the two filtered responses together in the initial XO. The woofer response was taken with a 5ms gated window at about 1m, so anything below 2-300hz or so is not accurate. I will later post measurements with a near field measurement merged into the far field to more clearly represent the low end (sealed at this point).



Here is the simulated response followed by the actual measured response with the initial 7 part XO in place. I’m concerned a bit about the hump in response at 400-700hz, but will see how it sounds before considering anything further:





Here are a couple more graphs, including impedance with impedance phase, acoustic phase and transfer function. I’d like to see better phase tracking above the XO point. Note, a Zobel circuit is included in the XO to flatten impedance.







Later, I will post some initial listening impressions.

[---k---]

Good stuff Dan. :T
I may not be able to contribute much more to your thread than that, but I really enjoy reading your posts. I always see something new. I guess I need to see how Paul is coming along for another DIY Chicago so I can hear some of your recent stuff.

[dlneubec]

There is a hump in the 400-700hz range that I initially left intact, to keep things simple and see how it sounded. It did add warmth to the sound and was not evident on all cuts, but on other cuts it stood out and negatively affected the speakers overall balance. I did do minor changes in XO value to adjust for this, while attempting to keep good phase tracking. This resulted in an overall response that was a little less flat than I'd normally like to start with, but clearly improved overall balance. I have since added a notch filter to smooth the overall response while trying to improve phase tracking above the XO point. I will post more on this later. The crossover point is around 1200-1250hz.

This speaker is sounding surprisingly good at this point. It could be really excellent. The vertical response does change as you stand up (listening at only about 9'-10'), not offensively in any way, but there is some vertical pattern control evident. I will most likely adjust to the final cabinet design a little taller than this prototype to try and get the 360º horn at ear level. That said, it still sounds very good when standing up or sitting on the floor. There could certainly be benefits to reduced floor and ceiling reflections as a result of this pattern control. The sound is identical as you move horizontally around the speaker, as would be expected. There is an almost holographic quality with just a single speaker. Given that all the sound emanates from the same general area, it sounds much like a point source, with no vertical shift whatsoever in sound as you go from bass to midrange to treble. There is excellent openness, clarity and definition. Vocalists sound very real and articulate. Complex musical material seems to be rendered with a lot of separation and space around the instruments. These impressions are with a single speaker which I would anticipate to improve further with a pair.

I have the bass bin sealed at the moment, but will try ported as well. A transmission line enclosure does not seem to be beneficial with this driver due to its low qts. I will probably build the flexport concept from my Chameleon design into this design so it can be set to sealed or a variety box tunings on the fly. When I merge a near field in with the woofer far field, it is essentially flat to around 60hz sealed. Despite the high Xmax on the woofer, I can’t seem to sense any issues using it at this higher crossover point.

The N26C-G is doing a fabulous job here and with the horn boost, does not seem to strain at all at this crossover point, even at very loud levels. I think this tweeter, combined with the increased headroom and likely reduction in distortion after attenuating the omni horn boost in the XO, is the reason for the detail and clarity I’m hearing.

One concern I have is resonances in the omni horn itself. I have not tested specifically for this as of yet. Some of the measured irregularities in the tweeter response might be due to this. These are simply 1/4" thick plastic waveguides (about $13 each). Since it is hidden from view, the diffuser portion could be filled with something to eliminate any offending resonances, though I don't know what at this point. The waveguide portion, however, has the back side visible, so I'll have to think of something for this that will both look good and effectively dampen any resonances. I don't really want to enclose it in a box because it will make the speaker more massive visually and less interesting looking. I could see adding some more horizontal wood rings along the surface, or possibly some vertical ribs. The idea I’m most taken with at the moment is to add a 2rd waveguide over top of the single, essentially creating a cavity between them of around ¼” in width. This cavity could be filled with some kind of damping material resulting in a constrained layer approach. This keeps the exterior looking clean and simple, without additional horizontal or vertical ribs. I'm open to any suggestions or ideas on this issue. For now, I will retest the tweeter as it is and then add some ¾” 3-layer sonic barrier to the outside to see if it makes a measurable difference. If it does, it will be clearly due to a reduction of waveguide resonances.

I suspect this omni design concept would be quite easily scalable to smaller or larger waveguides and woofers, using, for example, the PE 8” or 10” waveguides for a smaller version.

[Hank]

Creative, to say the least. Your hint #3 put a vision of the Duevel Venus model configuration in my head. Thanks for taking the time to post details!

[dlneubec]

The following results were after adding a notch filter to suppress the hump in the woofer response in the 400-700hz range. I also hoped this would allow me a little more flexibility to optimize phase tracking, which I would like to see improve above the crossover point.

This first graph shows the woofer, tweeter and combined responses. You can see the hump is completely flattened and the overall response is flatter. I’ve merged in the near field sealed woofer response here, which is pretty much flat to 60hz or so. I like to start with a flat response in an omni design and tweak from there. The reason being that they don’t behave like most other speakers, in the sense that off axis horizontal is the same as on the listening axis, so you don’t have the effects of horizontal directivity change as frequency rises. In this speaker it will change vertically, however, and the I suspect voicing changes will reflect that change and the impact it has in room response. I’ve also shown the reverse null response, which is both wide and deep, indicating good tracking on both sides of the XO point.





Here is the acoustic phase response. You can see how the woofer and tweeter phase tracks almost dead on from around 130hz to 4khz, which covers 5 octaves. This is what I had hoped for and I believe contributes to improved clarity in a speaker.



Here is the impedance and impedance phase. You can see that impedance ranges for just above 4 ohms to around 11 ohms and is quite flat. Impedance phase runs +-20º from around 80 hz and up.



Here is the XO where it stands at this point. With both a notch filter added and the zobel, it is as 11 parts, which is not too bad, though the notch has a pretty large inductor included. Please note that in the notch filter, the R value represents the resistor value. In other locations in the XO where an inductor is shown, the R value represents the dcr value of the inductor. This is just the way SoundEasy illustrates these items.



This brings us up to date with where I'm at. next up is to look at some measurements to see if the horn is resonating and come up with a plan to address it. I will probably work on that this weekend.

[AdelaaR]

It looks a bit ugly still ... but the idea of the design is really nice.
Once you get your design sounding good ... it would be nice to come up with a way to aestethically arrange and secure all the waveguides and drivers to make a piece of art speaker as a result.
Nice goin'

[gbegland]

Maybe I read through too fast, but you ended up with nothing inside the waveguide that is directly over the NS10? I have to imagine that there is something going on btw the woofer cone and the cavity created by the waveguide. Maybe this is creating the 400-700hz bump? Intuitively, it seems like it must be bad. Like a resonance or something. Have you tried stuffing the inside of the waveguide with Bonded Logic or fiberglass to see if that changes the measurements OR the sound? Or maybe line the inside with the same stuff that helped tame the cones peaking response.

Otherwise, it looks killer! Great project and great imagination as always.

Greg

[dlneubec]

I was probably not clear. There is a solid 3/4" mdf base under the diffuser that sits above the woofer. There is no opening into the diffuser from below.

[gbegland]

I was probably not clear. There is a solid 3/4" mdf base under the diffuser that sits above the woofer. There is no opening into the diffuser from below.

Gotcha. Glad to 'hear' that....complete, nerdy pun intended. What is the 90deg response of the woofer without that whole contraption above it? Do you have a plot of that you could layer with the design as it stands now?

Thanks, Dan. Excellent work. ;x(

[gbegland]

It looks a bit ugly still ... but the idea of the design is really nice.
Once you get your design sounding good ... it would be nice to come up with a way to aestethically arrange and secure all the waveguides and drivers to make a piece of art speaker as a result.
Nice goin'

Have you not seen Dan's others projects? The all end up looking fabulous.

[Juhazi]

Omnipolar speakers makes me think of my vintage Sonab's. The are supposed to sit right next to the wall. Partly because of reflections and bass boost. That placement prevents it to be omni (edit: destructs the rearward soundfield) and thus improves spatial stereo image.
http://www.carlssonplanet.com/oa14.php

Dan, have you got a suggestion for the placement of this newborn?

regards,
Juha

[meb46]

Dan, how is it that you manage to churn out really great ideas and designs so quickly... what am I missing here?

[gbegland]

Omnipolar speakers makes me think of my vintage Sonab's. The are supposed to sit right next to the wall. Partly because of reflections and bass boost. That placement prevents it to be omni and improves spatial stereo image.
http://www.carlssonplanet.com/oa14.php

Dan, have you got a suggestion for the placement of this newborn?

regards,
Juha

I my own experience, omnis tend to sound better well away from any boundaries and with the listener in the nearfield, but then again, I'm from the school of thought that says hearing the room is bad. There's already a room to hear on the recording and you wouldn't want to layer yours on top of it.

Greg

[Paul W]

One possibility is to use the actual WG as part of a form for poured resin. Sand to rough up the surface and presto...very inert WG. It is extremely easy to do & you might come up with some sort of "magical" looking resin filler for the part that is exposed...suspended metal flakes, swirled color etc.

[JonMarsh]

I my own experience, omnis tend to sound better well away from any boundaries and with the listener in the nearfield, but then again, I'm from the school of thought that says hearing the room is bad. There's already a room to hear on the recording and you wouldn't want to layer yours on top of it.

Greg

Double Plus 1!! :T

[dlneubec]

Well, I decided to not give up on my original concept of using a waveguide based diffuser above the woofer. I think the hump in the 300-700hz range is a cavity resonance between the woofer cone and the flat base plate of the tweeter diffuser. I was able to get rid of it in the crossover and it sounded very good, but that is a lazy solution. I’d prefer to further optimize the driver’s natural response, though I was not successful at doing so.

It occurred to me that the problem might be due to the concave dust cone on the NS10 and that a woofer with a phase plug might work better. When I was first considering this project a couple years ago, I always thought I’d try out this particular woofer.

Acoustic Elegance Lambda TD12H:



I used a pair of these in my BaSSlines project and since it is in storage, I could pull the woofers to use them in this project. My thinking was that an unaltered waveguide might sit above the TD12H, with the throat sitting right on the tip of the phase plug. I may chamfer the inside of the throat where it matches the phase plug, but for now, I simply added some weather stripping on the inside of the mouth to protect the phase plug. Below are a couple photo’s showing how it fits together.





I’ve totally redone the crossover design, lowered it to about 950-1000hz and did more auditioning today. I also added a port to the design to test it out ported. The TD12H is still available and one of the finest woofers I know of, though not cheap. The have a sensitivity of around 93db and will get to an F3 in the upper 30’s. It turns out to be a great match with the N26C-G in the omni horn.

I need to download the measurements and sims from my measurement laptop and then I’ll post them. They are looking very good and the result sounds fabulous, IMO.

[dlneubec]

It looks a bit ugly still ... but the idea of the design is really nice.
Once you get your design sounding good ... it would be nice to come up with a way to aestethically arrange and secure all the waveguides and drivers to make a piece of art speaker as a result.
Nice goin'

This is really just the test mule, the box from an old project that never was finished. I'll try to make it look better. :B

[dlneubec]

Omnipolar speakers makes me think of my vintage Sonab's. The are supposed to sit right next to the wall. Partly because of reflections and bass boost. That placement prevents it to be omni and improves spatial stereo image.
http://www.carlssonplanet.com/oa14.php

Dan, have you got a suggestion for the placement of this newborn?

regards,
Juha

They do have to placed out away from walls. In my listening room if I get them at least 3' from the walls, it works just fine, 42" is better. How far depends somewhat on the wall treatments, etc. and the distance to the listening position. They will neve do well up against the wall. They are similar to dipoles in that sense.

Have no doubt, omni's can sound wonderful with some room to breath. They don't suffer from the negative affects of uneven horizontal power response that typical monopoles often do. I've had traditional monopoles, open baffle dipoles, bipoles, open back midrange/waveguided tweeter, monopole with waveguided tweeter and hybrid omni's that I've designed in my listening room. They all have their strengths and weaknesses and all have their own special considerations and challenges when placing them in the room and designing them to adapt to a room.

[dlneubec]

Dan, how is it that you manage to churn out really great ideas and designs so quickly... what am I missing here?

Well, I sketch out a lot ideas as they occur to me and eventually get back to them at some point to see if there is something there I want to pursue.

This one has been on the back burner for quite some time. I think I bought the waveguides about 2 years ago and modded the 3 of them at that time in anticipation.

[dlneubec]

One possibility is to use the actual WG as part of a form for poured resin. Sand to rough up the surface and presto...very inert WG. It is extremely easy to do & you might come up with some sort of "magical" looking resin filler for the part that is exposed...suspended metal flakes, swirled color etc.

Interesting idea, Paul, thanks!

[dlneubec]

I my own experience, omnis tend to sound better well away from any boundaries and with the listener in the nearfield, but then again, I'm from the school of thought that says hearing the room is bad. There's already a room to hear on the recording and you wouldn't want to layer yours on top of it.

Greg

Double Plus 1!! :T

All I can say, guys, is that you might want to reconsider.

I've done numerous omni designs, every one of which were taken to several DIY events and judged by my peers and/or a formal judging panel. All have been very well received and award winners.

There is more than one way to the promised land! :B

[JonMarsh]

And that's what is great about DIY! We can each find our own way and try out things we are interested in!

Now if only I could afford to come out to some of the meets in your area, Dan! And hear them myself!

[Juhazi]

Thanks Dan for the findings and comments. I've just read reviews of Duevel Bella Luna and they pretty much confirm your words. Omnis are very sensitive to placement, room treatment and listening distance. I think that's a pro and a con.

I've had the Sonabs for 10 years and in two locations, now at my summer cottage. They give a very nice sonic atmosphere around the room, but I prefer good monopoles or dipoles for "serious" listening. I,m sure that Duevel approach is much better than Sonabs.

[JonP]

One possibility is to use the actual WG as part of a form for poured resin. Sand to rough up the surface and presto...very inert WG. It is extremely easy to do & you might come up with some sort of "magical" looking resin filler for the part that is exposed...suspended metal flakes, swirled color etc.

Possibly a better idea than mine... which was to fill the gap with that Great Stuff poly foam. I guess it'd be doable to trim and 'edge band' something around the foam gap to purty things up after.

Deja vu, all over again... seeing that box. Takes me back a ways... :B

Yet another great one, Dan!!

[dlneubec]

Deja vu, all over again... seeing that box. Takes me back a ways... :B

There has been a lot of water under the bridge since then!

[dlneubec]

I have the prototype in the living room listening to it. I'm very happy with how it sounds. The speaker has a sense of space or soundstage on its own and sounds much more real as a single than any monopole I've designed or any other omni, for that matter. As long as I keep it a minimum of 3' or so from the center of the speaker to the front wall and between 3’ or more from the side walls, I don't notice any degradation due to reflections anywhere around the room out to about 11-12' away. This is in a 15' x 20' room. It sounds the very much the same everywhere in the room, save some bass emphasis changes due to the room itself. That said, I get the sense that there is less variation to the bass around the room, perhaps due to the fact that the woofer is 32" from the floor and no closer than 3' to any other boundary. My speculation is that less boundary reinforcement may lead to less room variation.

I was voicing in my garage, which is all hard surfaces, so I had to up the tweeter output quite a lot when bringing into the house with furniture, drapes, carpet, etc. At this point I'm inspired by its potential, but it is hard to say with this kind of speaker without listening to a pair.

I have a second old box like the one I used for the prototype, so I've decided to assemble a second speaker to hear how a pair sounds. I will need to pick up a couple more waveguides and alter them for use and probably a few crossover parts I don’t happen to have in my possession, but I already have both the drivers.

I have one waveguide left unused, so I decided to create the diffuser for the second speaker, since it takes the most time and effort. This was done by first cutting off the waveguide. Next I glued a hardwood ball into the opening. Rather than creating a jig to mill down the ball with a router, I did it in a simpler way. I used a large forstner bit in the drill press. This was extremely easy and quick and you end up with a perfectly flat surface. I milled it off enough so that in the center I could counterbore the hardwood ball to a depth of ¼” x 1-1/4” dia. Inside of this counterbore a 1-1/4” x 3” tall hardwood dowel section was glued with 5 minute epoxy. As soon as the epoxy was cured, I filled in a bit with bondo. After letting it all set up overnight, I placed the future diffuser in a round jig created from an old woofer cutout. This has a center bolt added to it so it could be turned in the drill press. This was pretty much my only option, since I don’t have a lathe. Of course, it would have taken forever to hand sand the hardwood dowel to a point with just the the diffuser spinning, so I sped thing up considerably by using the combination of a belt sander and a drum sanding wheel in a powered hand drill. The combination knocked it down pretty quickly and easily with pretty good results for the tools I had on hand. Below is a photo of the resulting raw diffuser:



The next thing I wanted to work out was how to mount the 360º horn above the woofer. I want to use the holes in the waveguides for locating vertical support. This worked fine with the 10” woofer, but since I changed to a 12” woofer, the posts come down right at the outside edge of the woofer surround. My thought is to come up with an interesting looking way to continue to use posts through the waveguides, yet mount them above the woofer surround with clearance for it to travel. The following was the concept I came up with. I don’t yet know what the final materials will be, but I like how this looks and it should make for a negligible acoustic footprint. These use ¼” thick x 5/8” wide x 3” long aluminum above ¾” nylon spacers. I may reduce the height of the spacers and add several layers of rubber washers on each side of the spacer for some vibration isolation. Of course, this just shows them with two posts. There will be four.

[Johnloudb]

So, that's what the diffusor looks like in the other speaker too? I'd assume it does.

My opinion about omi-directional speakers is that they are better at recreating believeable acoustic space than any other type of speaker I've heard. My only experience with omi's is from hearing the MBL Radislstrahler a long time ago. But, sounded like Mel Torme was right there in the room.

[Hank]

Clever diffuser fabrication, Dan.

[JonMarsh]

This is definitely creativity at it's finest Dan- hat's off! And thanks for sharing so many details!