Revisiting the M8ta...

[JonMarsh]

Peabody, set the WayBack machine to 2004...

Surprise, surprise, I got a message from a re-enlisted member about the M8ta, along with some possibly surprised comments to see me here still active after all these years... (he doesn't know that I'm not really a live person anymore, but a cleverly crafted AI based on DeepSeek and using all the past posts on HTG as the LLM, that Sven crafted in order for me to complete some designs he is interested in...)

For those who haven't been paying attention for 20+ years, this started off as an Avalon inspired two way system, first with the HiVi M8a woofer and Hales tweeter- sort of an evolution of the M8 system that got written up in AudioXpress way back when, and the PDF is on HTG. It did migrate to the Dayton RS225 and the RS28a tweeter. Making a decent 8" two way is NOT an easy or recommended proposition with drivers available back then. A key to feasibility was employing an LR8 crossover configuration, and with the Avalon style cabinet, aligning the Z axis origins by how far apart the tweeter and mid woofer were so that the optimum listening and measurement axis would be at 36-38" above the floor, and parallel. I only have a few relevant files at home here... I have older hardware in storage with the original work.




Cabinet design rendering.

Design work was done with LspCAD, and I don't remember which 3D drawing package...

Here's what the polar response sets looked like, and the calculated overall power response:



Now, an interesting questions might be, would this be practical to update with new drivers, and possibly a new crossover? And, preferably, for a rough estimate, with things I have on hand?


Hmmm, how about this on the woofer? Like the original part, it has a relatively light cone, and wants a big box to breathe...







And this for the tweeter?

[JonMarsh]

will be updated- having server glitches

[JonMarsh]

OK, I was just being a little coy yesterday, anyone familiar with recent driver data or tests will recognize the PuriFi PTT8.0x04 woofer SPL plot, and of course the tweeter SPL is my own measurements of the Peerless DA25TX00-008. The original design evaluated a number of parts, including the then venerable Seas
Millennium Excel tweeter (still have that pair I bought for possible use...

Here's one pic, one of the original development cabinets, with RS225 and Hales tweeter:




Continuing the stroll down memory lane, the crossover schematic, showing how the LR8 networks with impedance stabilization were implemented (yes, I still have layout pictures- I'm a data hoarder)




And schematic for the version with a Seas Millennium tweeter.

[JonMarsh]

And I did find my master file archives for this project this morning- OTOH, the original project is still online at HTG

[JonMarsh]

From the WayBack machine... closed, no further posting.

https://www.htguide.com/forum/primetime-a-v/mission-possible-diy/missions-accomplished/3518-m8ta-fun-or-work

[Bear]

What's interesting to me is that the design was pretty much a stretch in its day, but with waveguided tweeters being available from OEMs, having a Fc in the 1500 Hz range isn't so outlandish anymore with highly usable SPLs. Without resorting to waveguides, there are still a number of great options available (I've got a pair of T34As sitting around waiting for a use case).

[Scareurpasenger]

Same! I have a pairs of the t34a that need a project.

[JonMarsh]

Well, as they say sometimes, it comes down to the crossover, and this issue is why back then we used an LR8, with a partial elliptical network filter.

But, Gee! Funny thing you guys mention... T34's?

I have options on hand...




Probably some measured data around here I can use for some quick evaluations...


And, of course, for the foundation, a spare pair....



Still a lot of non-audio stuff going on, and I can't drop my current projects, BUT, I should be able to do some review of all the old data, and some modeling and updated enclosure work, LF alignment, and some trial crossovers to consider-

[JonMarsh]

And in a related stroll down memory lane, as 8" two says seem to be more popular these days, MarkK's compact two way with the RS225, RS28a- lots of dynamic headroom, especially for a sub-satellite type approach!








Also with an 8th order high pass.


On listening axis...

[JonMarsh]

One more interesting thing- double checked inventory, I have two pairs of the PTT8.0x04-NAB


🤔

[ergo]

Interesting resurrection from past.

For those who haven't been paying attention for 20+ years

so lets see if this guess will be good then

Design work was done with LspCAD, and I don't remember which 3D drawing package...

Might have been SharkCAD that you were into back in those times, or was that a bit later [Click and drag to move]

[JonMarsh]

I think you're correct, it was one of the spin-offs from a 3-D cad program that got sold to PunchCAD; in fact, I ended up getting their Home Design CAD program to do the landscaping design for the backyard for the contractor that implemented it back in September 2022. SharkCAD and ViaCAD Pro used to be on my Macs, even while I had Fusion360 licenses, but dropped off after I got Shapr3D, which I utterly feel in love with. Its import and export are absolutely top flight, and with the Siemens Parasolid Kernel, the computation functionality is beyond reproach. (IMO; YMMV, of course!). And I love the functionality of the 2D sheet files one can create.

https://shapr3d.com

[Evil Twin]

Given some of the newer drivers available, revisiting this concept has a certain appeal... as does blowing it up, in another sense.

In a pure "revisit", why not consider a build inspired by the Ardent D? No veneering, little internal bracing, and an attractive profile.

OTOH, a more purist point of view could engender a relatively cubical internal volume, to assure maximum linearity for the combination of driver and internal enclosure, as presently being pursued by the Saint-Saëns, and perhaps an abbreviated bevel facet location focused on optimizing the power response characteristics of the tweeter? This would likely warrant additional research, but the results could be most impressive...

[JonMarsh]

Slow work takes time, but I've located a basic test enclosure that can be updated to get some useful data from a PTT8.0x04-NAB. And of course, even test enclosures have to be interesting to look at, so I've got a new jumbo 24" bamboo cutting board to provide the front panel rebate surface...

[Bear]

The M8ta and the NeoD seem to have been pretty seminal designs back in their day. I don't think that it's unreasonable to trace the Ardent D back to both of those (as an outside observer). The BOM speculation would be a fun guessing game until the big reveal. I suspect that the main issue for most folks with the Ardent D was simply the cost of the BOM, rather than the complexity of the build. Well, that and the part availability of the tweeter and mid...

[Bear]

While expensive, the PTT8.0X04-NAB-02 models really well in about 40L with the SS 26W PR. Really, anything between about 20L - 60L looks good with that pair, depending upon the tradeoff between bass extension, Xmax, SPL output and step response.