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Questionable Loudspeaker Enginerding with Aubey Industries and Weeb Labs!

Weeb Labs

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For the past year or so, @ItsMeAubey and I have been experimenting with various evidence-based loudspeaker designs. The task has been to develop a well behaved active speaker that can be assembled by almost anybody, using inexpensive off-the-shelf components and DSP.

The temporary title for this project is "Directron" (a joke aimed at Directiva) and to date, we have iterated through three major redesigns. We have ten primary design objectives and those are:
  • Low distortion
  • High SPL capability (>105dB)
  • Sub-bass capability with an F3 below 27Hz
  • Smooth directivity, later revised to wide and near-constant directivity
  • Extremely inert cabinet
  • Based upon one or two JAB5 DSP amplifiers (slave cascade mode)
  • Utilizes affordable but high performance off-the-shelf drivers from brands such as Dayton Audio
  • Cabinet published as STEP/DXF/PDFs which can readily be sent to any cheap CNC service for fabrication
  • Lossless, low latency wireless capability (optional)
  • Cardioid behavior (optional)

The first generation of our speaker consists of floorstanding cabinets with a great deal of bracing and a four-way design. We selected the following drivers (all Dayton Audio brand):

  • Epique E180 (Subwoofer)
  • DS175 (Passive Radiators)
  • RS180 (Midbass)
  • RS52AN (Midrange Dome)
  • ND25FW (Waveguided Tweeter)

At the moment, I am awaiting CNC cuts for the first generation cabinet and you can see a CAD render of the construction below. The second image is a slightly older render but it will suffice as a simple rear view.

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We have also performed a great deal of simulation and experimentation within VCAD for this design but the data provided by Dayton is somewhat limited and so it won't be possible to fully characterize the speaker's behavior until it is assembled.

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This is a somewhat older screenshot, prior to more precise optimizations. When designing the first generation, constant and wide directivity was secondary to smooth directivity, which means that horizontal beam width isn't particularly large. The expectation is 50 degrees, narrowing above 10KHz.

Data for the second generation is not readily accessible to me at the moment but the primary changes were rear drivers for cardioid behavior and the replacement of the ND25FW with a SEAS DXT tweeter. To my knowledge, this generation was purely theoretical and we don't intend to build it.

For the current (third) generation, we are experimenting with a dual tweeter design which incorporates the Dayton ND14 and ND20 units along with the previous component selection for a total of six drivers.

This generation is something of an experiment and prioritizes the widest, most uniform horizontal directivity possible. We are giving serious consideration to the prospect of fabricating the cabinets as two separate pieces; one containing the subwoofers (second JAB5 in cascade mode) and the other containing the remaining four drivers. As the main cabinet would already contain an RS180 capable of reaching frequencies below 50Hz, we believe this would both simplify assembly and introduce a certain degree of modularity. Builders would have the option of assembling only the portion required.

At the time of writing, it is quite late at night and this opening post is already rather lengthy, so I will conclude it here for the moment. Should you happen to spot a problem or wish to raise a concern which I have not addressed herein, by all means do point it out but please also bear in mind that we have discussed and researched this project to death over the last year. Many dozens of drivers, baffles and cabinet designs have been considered but summarizing all of it here would take hours!

As always, thank you very much for reading and we will continuously update this thread with new developments. We will also likely be using the Discord server linked in my signature for realtime discussion, so feel free to stop by. :D
 
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Ericglo

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Have you seen Zaphs build and/or Dayton RS TMWW?

I haven't heard the Zaph, but I did hear the TMWW about fifteen years ago. It used the Seas tweeter and Murphy crossover. I mentioned this in the PSB thread. In a comparison with the Stratus Golds I had at the time, it was much better. I told the owner that I would have been happy with those speakers for a long time.

I have wondered what a waveguided tweeter version of the TMWW would sound like. That is kind of what Revel is doing.

I will be interested to follow your progress on this.
 
OP
Weeb Labs

Weeb Labs

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I have just stumbled upon the RS75 and ordered a pair. The RS75 retails for €30, which is approximately half the price of the RS52AN while performing very similarly. The €8 Vifa TC7FD00-04 also looks very interesting and represents quite possibly the best value for money in a midrange driver.

Directivity profile for the RS75 looks ideal, with a 2.5KHz buffer above the desired 3.5KHz crossover point to the ND20.

RS75_FreqResp.png



Even at 98dB (1M), distortion remains below 1% within the relevant 900Hz to 4KHz band.

RS75plus12_RelHarm.png



For comparison, the €8 Vifa driver. Very nice on-axis response with a similar directivity profile.

TC7_FreqResp.png



Distortion at 86dB is slightly less than ideal within the relevant band but this driver would still be well suited to a small three-way desktop speaker. Impressive performance for the price.

TC7_RelHarm.png
 

Trdat

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Will you be sending to Amir to get Klippel information? Or a general test for final measureements?

I'm keen to follow this design, I think the directiva is great but a little expensive and just not sold on it yet. I like your design criteria, personally I love horns so maybe a compression driver with cardoid would be my preference, but waveguided tweeter still is fine. I like the idea of using Dayton drivers and having a DXF file for CNC'cing.
  • Smooth directivity, later revised to wide and near-constant directivity
Im just confused about this comment. So will it be a wide dispersion that has constant directivity or contant directivity that is relatively narrow?

The only other thing which I would say is that sub bass isn't to important, most people use subs well at least anyone in this type of DIY would probably be inclined to use subs.

Apolgize for my 2 cents worth I will keep an eye on the thread. Where are you up to in the process of things?
 
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Weeb Labs

Weeb Labs

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Will you be sending to Amir to get Klippel information? Or a general test for final measureements?
It would be very nice to have NFS data but shipping 35KG floorstander from Ireland to the United States would be incredibly expensive. I now have the ability to capture very comparable measurements myself, so that will be sufficient.

Trdat said:
Im just confused about this comment. So will it be a wide dispersion that has constant directivity or contant directivity that is relatively narrow?
The original objective for the first generation design was that directivity behaviour should be smooth but not necessarily constant. It would begin to narrow above 10KHz.

For the second and third generations, it was decided that we could do better than simply "smooth". Wide, constant directivity throughout the band therefore became the new objective.

Trdat said:
The only other thing which I would say is that sub bass isn't to important, most people use subs well at least anyone in this type of DIY would probably be inclined to use subs.
I agree. This is why we have taken a modular design under consideration. I am currently assembling a testbed cabinet for the third generation, based upon the modular concept.
 
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OP
Weeb Labs

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Now testing a few drivers. Directivity is likely to be a complete mess at the moment but that's not yet critical.

image0.jpg
 

alex-z

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Shame the version with DXT tweeter and cardoid woofer behaviour is purely theoretical. That would likely be the best performing version.

Having tried the ND25FW-4 and RST28A-4, the Seas DXT combines the strengths of both, great directivity, low distortion, and 2000Hz crossover capability.

Another mid-range driver worth considering is the LaVoce FSN041. It has the same sensitivity and cost as the RS52AN, but is capable of a 350Hz crossover point, and has a 104mm faceplate, rather than 130mm on the RS52, allowing for tighter vertical directivity.
 

HammerSandwich

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Cool project. Can't wait to hear the video commentary.

The RS75T would be perfect for a tight MTM. Same with the TCs, which are just impressive value across the board.

Since you found Feleppa's site, any thoughts on the Dynavox?
 

Blumlein 88

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Are you pretty much dialed in on a rectangular enclosure?
 

Ilkless

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You can consider the Scanspeak 10F/8414 for midrange - decent pricing, excellent smooth and extended FR, super wide and smooth horizontal directivity for the driver diameter. Well behaved distortion too.
 

Trdat

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Shame the version with DXT tweeter and cardoid woofer behaviour is purely theoretical. That would likely be the best performing version.
This would be a nice option as well.
 
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Weeb Labs

Weeb Labs

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Are you pretty much dialed in on a rectangular enclosure?
Yes, that's what we're doing.

Test fitting the manual cabinet cuts. It looks quite reasonable.

image0.jpg


No passive directivity control yet but this is just a testbed cut from MDF scraps.
 

ItsMeAubey

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Shame the version with DXT tweeter and cardoid woofer behaviour is purely theoretical. That would likely be the best performing version.

I have good news for you!

The 3rd revision of the cabinet (the final release version) that I am working on right now is definitely going to be capable of cardioid bass and maybe cardioid lower-midrange. Additionally, the upper "bookshelf" cabinet will be separate from the lower subwoofer section, so people who don't want to build a massive floor-standing speaker with 8 drivers can instead just build the upper section.

Here's a sneak peek of one of the cardioid sub prototype designs from before the cabinet was split into two separate components:

1647309531332.png
 
OP
Weeb Labs

Weeb Labs

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First in-room measurement of the testbed unit. At this point, I have only implemented a simple crossover in DSP and a couple of PEQ filters to deal with room modes. Driver levels have not been matched at all; I was simply lucky.

When the weather permits, I will capture a full spin outdoors to see how the directivity is behaving (probably poorly) before proceeding further.

unknown.png
 
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OP
Weeb Labs

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Current directivity for the testbed. Approaching 90 degrees but for a variety of reasons (diffraction being one of them), it not quite uniform. Continuing to make refinements.

unknown.png
 

airborne

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do not cross a dome tweeter to a dome mid tweeter - waste of money

i built a speaker like that and it sounded great but then i built one with a bullet tweeter crossed to dome mid-tweeter and it sounded even better

a soft dome mid-tweeter can easily cross to a bullet supertweeter so just do that - a soft dome will never have the air of a bullet supertweeter

with a bigger dome like 2" morel maybe use Faital Pro supertweeter which can go lower ...

with a smaller 1.5" dome any supertweeter should do, perhaps Beyma CP-09
 
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Weeb Labs

Weeb Labs

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The crossover and driver choices for this project are governed by the simulation and measurement data, with wide directivity as an important objective. This is one of the advantages of the current testbed configuration, whether or not it proves to be a feasible solution given the design constraints.
 

airborne

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The crossover and driver choices for this project are governed by the simulation and measurement data, with wide directivity as an important objective. This is one of the advantages of the current testbed configuration, whether or not it proves to be a feasible solution given the design constraints.

directivity of Beyma CP-09 is wider than any 1" dome ...

or you can use CP-21 for even wider directivity but only in horizontal plane ...

anyway if you care about directivity you shouldn't use a flat baffle ... 3D print or CNC that stuff or something ...

a flat baffle will always result in a compromised directivity - unless you do like a 6-way with FIR filters or something but then it will be a colossal waste of money on the amplifier side of things ...

i do wonder though - what's more expensive - to CNC / 3D print a complex shape baffle or to do a multi-way FIR system that controls directivity electronically ...
 
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Weeb Labs

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Again, this is simply a driver testbed assembled from scrap materials; it is not the loudspeaker design described within the OP.

The CP-09 is a relatively expensive, high distortion driver and exhibits narrower horizontal directivity than the unoptimized testbed. It is closer to 45 degrees at the -6dB point.

1647581489778.gif
 
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