Let's engage the time circuits- and bring the Isris back to the future...

[JonMarsh]

All kinds of things are getting scrambled in their sequence, compared with recent plans; this is just one more... in this case, I'll put the responsibility on the shoulders of an HT Guide member from Singapore who has strong interest in building something like the Isiris three way design study. And this was on my moderately near term list of to-do's, so it got pushed forward a bit.

Let's summarize some issues:

• Like many older designs, component availability may be an issue- in this case, the new builder has recently acquired a pair of Jantzen JDT0-1024, so scratch that issue off the list.
• The Accuton C173-6-090 is still the best part to consider for this application out of their entire series of similar drivers, and a review of the data sheets and graphs will show why... and with care, they can still be sourced.
• Aurasound woofers... no way. Long discontinued.
• But that brings us to the option I had been pondering a long time, the conversion to using the Dayton Audio RSS315HFA-8 woofers, connected in parallel. This driver has T/S parameters not all that dissimilar to the NS12-513A, and wiring two 8 ohm drivers in parallel, instead of connecting two four ohm drivers in series, can give a pronounced sensitivity boost, 6-7 dB.
• The RSS315HFA also can deliver 40% greater Xmax, not to be sneezed at.
• Both drivers have their resonant breakup mode near 2kHz, and the big Dayton has pretty smooth response out to 1200Hz, making it quite suitable for a 300-400Hz crossover point, given the motor design and modest impedance rise.
• Mechanically, the RSS315 is just slightly larger, but the gods of fate smile upon me, and it fits in the original cabinets OK. Well, an RSS315HF-4 does, and I don't think it's going to be any different in size than the four RSS315HFA-8 winging their way toward me since the middle of last week.
• There was a Test Article 6 crossover developed but not yet built- all the parts are on hand, but obviously some components will need to change, especially the woofer crossover.

Running the numbers looks pretty good in the same sealed enclosure- and of course could easily be improved with even just a modest 3dB Linkwitz Transform:






So, what are we waiting for, other than 4 drivers from PE?

I'm going through the archives, and pulling out the stuff that could constitute a build guide, and updating the CAD drawings to add Metric values and clarify a few points...

This one should move pretty fast... can you say, "Isiris summer camp"?

[technodanvan]

Dang Jon, I thought you were going to announce a 'budget' version with an SB Acoustics ceramic mid and re-use the Peerless tweeter. If you did though I'd have to figure out how to build a pair...the wife saw these and proclaimed her interest.

Yes, even before we get the Ardents and three other projects in the works, with another one in the exploratory stages...I might have a problem.

[JonMarsh]

Dang Jon, I thought you were going to announce a 'budget' version with an SB Acoustics ceramic mid and re-use the Peerless tweeter. If you did though I'd have to figure out how to build a pair...the wife saw these and proclaimed her interest.

Yes, even before we get the Ardents and three other projects in the works, with another one in the exploratory stages...I might have a problem.

What you describe is possible... even a scaled down version using the RSS265HF-8 woofers, say, and some yet to be determined 5-6" midrange (could be the 18 Sound, might be an SB acoustic Nero 6MRN150D Pro midrange (plenty of sensitivity to work with, massive Neo motor), even the Textrene MW13TX-4 could be a possibility. The 5" ceramic SB part is a bit low on the sensitivity side to cope with the baffle step needed though it might squeak by with the RS265's in parallel- it would really be close. The 2pi target for the RSS265's would be about 86dB. So it could be doable.. so think of a 3/4 scale Isiris. And the DA25 corundum tweeter would be my first choice.

Hmmmm...





I'll put it in the queue to do some modeling work...

[JonMarsh]

...the wife saw these and proclaimed her interest.

This could be the "money quote" as we say in reviewing news articles and editorial...

[JonMarsh]

The SB Ceramic 6" woofer

Lest anyone forget what we're talking about with the SB ceramics, (and I know I have a pair or two on hand, but not sure which impedance)




Because the frame diameter is 150mm, or 6x 25mm, I normally consider the SB15CAC30 a 6" driver, not a 5" driver. It's certainly too big to go places one would usually put a 5" driver.

[JonMarsh]

On order

Ok, I checked the AudioWorx/SMJ driver inventory, I have the 8 ohm version of the SB ceramic, but not the 4 ohm version... remedying that has been put in motion, with a pair on order, just because I'm such a gullible, wait, no, "enthusiastic" kind of guy. And feel I ought to spend the unexpected stimulus money on something worthwhile...

Any excuse for buying more interesting drivers to test...

[technodanvan]

Oh geez, I feel that I opened a can of worms or two. ops:

This could be the "money quote" as we say in reviewing news articles and editorial...

I'm just glad she doesn't find anything from Wilson attractive.

[JonMarsh]

well, the wonders of modern FedEx tracking, those 4 ohm SB 6" ceramic-aluminum woofers from Madisound are now in Chicago today! I don't expect to actually be holding them in my hand until Sunday, when I get back from a working trip to CA. I have a reasonable test cabinet to pop them into in storage here, so checking them out won't be far down the road.

Also, just to give you some idea of ways that a scaled down front baffle for the upper module might work out, here's comparison of the Osiris baffle next to an Isiris upper module. This will handle the DA25 tweeter, not problem, and obviously a wide range of more conventional ones, such as the SB26CDC-C0004, which is quite Scanspeak like in it's distortion behavior, and is planned for the CC type speaker for the TTC portfolio.

The smaller the tweeter diameter, the smaller the top width of the cabinet can be made. I'm looking at something like this, but reducing the top width and increasing the bottom width from 12-1/2" to 14".

[technodanvan]

The smaller the tweeter diameter, the smaller the top width of the cabinet can be made. I'm looking at something like this, but reducing the top width and increasing the bottom width from 12-1/2" to 14".

You might want to have that drawn up in CAD to see how it would look. I know we have more important considerations than aesthetics, but a squatty top section might look funky. If things are being shrunk down to a 3/4 Isiris perhaps a more conventional single baffle (a la Ardent) would work just as well - unless you think it important to isolate the 'bass bin' segment. Simpler construction may also yield more interest in the DIY community (if that is a consideration) or perhaps fit in the existing TTC cabinet (assuming they're large enough for a 10" subwoofer!)

[Steve Manning]

You might want to have that drawn up in CAD to see how it would look. I know we have more important considerations than aesthetics, but a squatty top section might look funky. If things are being shrunk down to a 3/4 Isiris perhaps a more conventional single baffle (a la Ardent) would work just as well - unless you think it important to isolate the 'bass bin' segment. Simpler construction may also yield more interest in the DIY community (if that is a consideration) or perhaps fit in the existing TTC cabinet (assuming they're large enough for a 10" subwoofer!)

Now Danny ..... when has Jon ever gone the simple route?

[JonMarsh]

Now Danny ..... when has Jon ever gone the simple route?

Uhh, I think the last time was, uhh, around 2007. But it might have been 2009.

But as to why... well, you must not have read the Three Way Design Study thread!

But I'll refresh your memory...



And you know, Danny, this is Mission Possible DIY, so the poster's role is just to show what Mission is actually Possible... then it's up to the audience to decide how they want to DIY...

And if someone wants to take an Isiris/Isis design and put it in a Ardent style cabinet, well, who am I to gain say that? The Design and Audio Taste Police? I think not... even though at times I'm tempted!

Besides, I'll have the last laugh, with someone trying to move around a single cabinet with those big heavy woofers AND a big heavy midrange driver, at 120L or so!

[JonMarsh]

Vendors getting their pre-pandemic delivery Mo-Jo back!

And since progress is out most important product, good news to report!

But, since without pictures, it's not real, on the internet, and these days, half the time WITH pictures it's actually UNREAL, still for the record...






And yes, those boxes are heavy! it would be an exaggeration to say that one of these RSS315HFA-8 drivers weighs as much as all four of the Neo NS12-513A, but ONLY a SLIGHT exaggeration!

[technodanvan]

...if someone wants to take an Isiris/Isis design and put it in a Ardent style cabinet, well, who am I to gain say that? The Design and Audio Taste Police? I think not...

I seem to recall a certain alter ego that may or may not have something to say about that!

And yes, those boxes are heavy! it would be an exaggeration to say that one of these RSS315HFA-8 drivers weighs as much as all four of the Neo NS12-513A, but ONLY a SLIGHT exaggeration!

I haven't bought a meaningful subwoofer in a long long time. I have not even explored that as an option with my wife at this point - the last sub build I did was back in college some years ago, well before meeting her. By this I of course mean a real subwoofer, not the little 5" Tang Band I have in my office!

That said, I suppose if she is into the style of the Isiris perhaps should wouldn't mind some mammoth subs sitting behind them.

[JonMarsh]

With the Isiris built with the RSS315HFA-8, you have the sub built in- just use a small Linkwitz transform in the signal path, it could even be passive in the preamp path, just modify the voicing filter design.

With just a 3dB Linkwitz transform at 28 Hz, your F3 winds up being 28Hz, and your F6 22Hz, not factoring in boundary gain.

[JonMarsh]

And a test enclosure is ready...

Well, I have never received so many updates from FedEx on the progress of a shipment across the country, but I can't complain when it finally gets here...

Unassuming looking in some regards, it may be the perfect maximum bang for the buck midrange.

Besides the smooth and extended SPL response, the other key to me is the very flat impedance curve, which is a fundamental signature about important motor characteristics.

[technodanvan]

Unassuming looking in some regards...

It really does in that photo. One could guess it'd have a poly cone just by looking at it.

[Dave Bullet]

Better not let ET find out you've chosen a non-approved colour.

Let me rectify that for you...

[JonMarsh]

Yeah, well, we're just keeping this one "out of sight, out of mind" with regards to ET for now. Since the original big guy Accuton midrange is obviously white, that seemed like a reasonable choice for a proposed baby version.

Of course, the logical question ET would have, in all likelihood, is what is the destiny of that black aluminum cone version you have? Most likely the SB15NBAC30-4? The published data does look awful similar... a skeptic might be inclined to wonder if there actually is any acoustical benefit to the ceramic chemical etch process the CAC likely uses?

[JonMarsh]

You know, when you plan on upgrading something designed and built 8-9 years ago, you can't really count on things working out mechanically the way you hope...

There's no planning ahead for a complete woofer upgrade in that time frame. And dimensions vary from driver to driver... as we all know...





But some days we get lucky...

And occasionally I'll be happy to settle for luck over skill and foresight!

But are these cabinets ever going to be heavy with the new RSS315HFA woofers!

[Dave Bullet]

....the logical question ET would have, in all likelihood, is what is the destiny of that black aluminum cone version you have? Most likely the SB15NBAC30-4?

Very close - your impedance senses are spot on. It is the SB17NBAC35-4. Not meaning to threadjack.... I am attempting a few simple concepts before I try an open baffle (likely a future disaster).
Facet baffle
2-channel active DSP via Raspberry Pi-3 piggy back Suptronics 7.1 DSP board using Linux and ecasound for the crossover

Have a SBA Satori TW29D-B which I got on sale to pair with the SB17NBACs

A small ported design will allow me to carry these to the local audio club I attend for some feedback.

[Efalegalo]

"Budget Version"

Unassuming looking in some regards, it may be the perfect maximum bang for the buck midrange.

Besides the smooth and extended SPL response, the other key to me is the very flat impedance curve, which is a fundamental signature about important motor characteristics.

Wow - if there ever ends up being a "budget" version of the Isris, I'm definitely interested.

I've never built any of your designs, Johh, but I'm dying to try. Only the highest praise can be found on your designs.

Is that the SB17CAC35-4? If so, you may find the following link helpful (if you are not aware of it already):

https://www.erinsaudiocorner.com/driveunits/sbacoustics_sb17cac35-4/

Aparently its an excellent driver, with the only limitation being the low-end extenstion. Erin indicated he would be reluctant to use it below 80hz, and suggested its best use as a mid in a 3-way, as opposed to do dual-duty as mid&bass in a 2-way.

[JonMarsh]

Great testing on Erin's part, and it confirms what I've seen in the SB15 version of this part. And his conclusions are the same as mine, which is why I am interested in it for the midrange role- but due top slightly better top end and off axis characteristics, I think I'd stick with the SB15 version. My area of use would be something like 300Hz and up, maybe a 350Hz nominal crossover with the time offset integrating 3rd order network that I like. From 350Hz to 2kHz, it should shine pretty well.

I'm giving the Isiris Jr. some serious consideration- heck, the drivers are practically self selecting, when you can find some of the newer parts that play out of their league in key performance areas. In someways, it's likely to seem strange to some folks to go to so much effort on the cabinets for drivers that won't be all that expensive, but hey, that's what I was doing in the late 70's, relative to today, and that's basically how Avalon started out, optimizing the performance with similar "extreme" cabinet and crossover approaches, using Eton and titanium dome tweeters that were pretty reasonably priced compared with the ceramic and beryllium parts in favor the last several years.

If an initial driver tests and test build is promising, I'll probably go forward with this- there's a nice opportunity for something to slot in between the Wavecor Ardent and the Isiris, but priced much more like the Ardent- or less!

[JonMarsh]

Very close - your impedance senses are spot on. It is the SB17NBAC35-4. Not meaning to threadjack.... I am attempting a few simple concepts before I try an open baffle (likely a future disaster).
Facet baffle
2-channel active DSP via Raspberry Pi-3 piggy back Suptronics 7.1 DSP board using Linux and ecasound for the crossover

Have a SBA Satori TW29D-B which I got on sale to pair with the SB17NBACs

A small ported design will allow me to carry these to the local audio club I attend for some feedback.

[ATTACH=CONFIG]31195[/ATTACH]

This looks like a lot of fun for a compact system- hope you can do some polar studies of the driver performance, including the TW29D-B. I did a lot of SB driver testing back in 2019, but didn't have the time available then to build anything! That situation is changing, but not as fast as I'd like- been a lot of work to do in retirement what with relocation to a different state, working on a home construction contract (mostly done, even the fine details now- but that all takes time!)

Please keep us posted on how this little guy turns out!

[Efalegalo]

I think I'd stick with the SB15 version.

In the video version of Erin's review, he comes to the same conclusion for the SB17. He indicates that while it is an awesome driver, he would not use it for bass duty. He would instead use it only for mid-duty, but also adds that for mid-duty situation, one would be better off using the smaller version of the SB17 (i.e., the SB15), to better match tweeter directivity/operating range of a tweeter.

[Bear]

Wow - if there ever ends up being a "budget" version of the Isris, I'm definitely interested.

I've never built any of your designs, Johh, but I'm dying to try. Only the highest praise can be found on your designs.

Is that the SB17CAC35-4? If so, you may find the following link helpful (if you are not aware of it already):

https://www.erinsaudiocorner.com/driveunits/sbacoustics_sb17cac35-4/

Aparently its an excellent driver, with the only limitation being the low-end extenstion. Erin indicated he would be reluctant to use it below 80hz, and suggested its best use as a mid in a 3-way, as opposed to do dual-duty as mid&bass in a 2-way.

I've got a much-delayed project with this limitation in mind. For "pragmatic" people, this is a hard-to-beat value option for a 6+1 that hands over to a subwoofer (or two) at the 80Hz cutoff. Versus the 15cm version, it's a little cleaner and more sensitive, but it requires a lower crossover for directivity matching.

And yes, I really want to know what I give up with the more attractive gray driver vs the white ones that had a dye job and some extra electricity applied to to cone.

[knifeinthesink]

What you describe is possible... even a scaled down version using the RSS265HF-8 woofers, say, and some yet to be determined 5-6" midrange (could be the 18 Sound, might be an SB acoustic Nero 6MRN150D Pro midrange (plenty of sensitivity to work with, massive Neo motor), even the Textrene MW13TX-4 could be a possibility. The 5" ceramic SB part is a bit low on the sensitivity side to cope with the baffle step needed though it might squeak by with the RS265's in parallel- it would really be close. The 2pi target for the RSS265's would be about 86dB. So it could be doable.. so think of a 3/4 scale Isiris. And the DA25 corundum tweeter would be my first choice.

Hmmmm...

YES!

God id love to see what you do with the DA25 and sb15 combo. And a big JM combo I could actually afford to build. Oh boy.