Directiva r2 project: market requirements gathering

[TimW]

Another vote for an active cardioid design here. I would like to see what can be done with affordable woofers and a decent tweeter like the SEAS from Directiva R1. After all the name Directiva was used because directivity is one of the key design principles right? I would love to hear something with controlled directivity down into the bass region but I can't afford the options from Genelec, Kii, or D&D. Something like the GGNTKT Model M1 would be awesome. I will DIY and scrounge to get the required electronics together.

 

[HammerSandwich]

My thinking recently is to build something like Bagby's bass module which can act as a stand for a variety of mid-treble modules on top, which I can swap out as I see fit.

I agree with this approach, especially for DIY. Modular construction is easier in several ways, and it allows swapping just one section at a time.

I would recommend sticking with the DXT. Short of 3d printing a waveguide or using the new SB Beryllium unit ($$) it is the best way to get stellar off axis performance.

It's worth taking a look at Augerpro's waveguides. The SB26ADC works really well, and the price is right. What we need is a list of CNC/3D-print services that are reasonably affordable & friendly to small-volume projects. There's Speaker Hardware and?

How large would the (sealed) speaker have to be if we were to make it properly full range with something like the Dayton UM18? is this a completely bonkers idea?

Pretty bonkers, yes. While I like sealed woofers, full-range performance bumps into both Vd & Hofmann. All dBs from VituixCAD at 1M in half-space.

The PTT6 has Vd of 130cc, and a 15L BR/PR version can do 105+dB in the passband with f3 around 40Hz. Put a woofer with 500cc Vd - say an RSS265HF-8 - in a sealed box, and you get 105+dB in the passband with f3 around 40Hz from 35+L. Well, crap. If room gain cooperates, the slower roll-off could make 20-25Hz useful, but it's hardly an improvement at 30+Hz.

So, you're right about needing to go big if you want a sealed box to outperform significantly the R1 in the bass.

Let's step up to the 15" RSS390HF with >1100cc Vd. (And I'll strongly encourage RSS over UM, especially when using higher XO.) If you want to keep the box reasonably small, say 55L, you get Qtc around 0.9 & need 500W to push near Xmax. An 85L enclosure will drop Qtc to 0.8 & allow Xmax with 300W. Go even bigger, and power requirement drops while output stays the same. In all cases, you see 105dB to 25Hz, so f3 reaches 20-22Hz. That's expected, as 1 octave = 4x Vd.

Considering that Rick & Amir don't want to deal with a massive box, plus the benefits of distributed subs, I'd say that ~55L with an RSS315HF-4 or ~700cc equivalent is about the practical limit. That will deliver 105dB above 30Hz with a 32Vrms amp, such as the NC252MP. External dimensions could be roughly 12" x 18" x 24".

 

[617]

As a long-time DIYer I remember the DIY projects I sort of lusted after when I got into DIY, and many of them were just large tower speakers like Troel's designs or the Statements II or Khanspires. These designs brought a lot of new people into the hobby, and it seems like there was this renaissance of DIY audio which coincided with the availability of inexpensive measurement tools (Omnimic, Soundeasy, ARTA, REW) and inexpensive, high quality drivers (Dayton RS). I'm sure most DIYers here remember those days.

Seeing the DIY scene, it makes me a little sad. A lot of the people I learned from have passed away, most prominently Jeff Bagby and Linkwitz. Others have stepped away from DIY like Zaph. Some look like they're retiring, like the speakerdesignworks guys. As a result, I haven't seen any simple designs that really excited me. Javad Shadzi has some great designs but they use very esoteric drivers for the most part, and Troels is on his own trip; I respect his consistency though.

I think when the Statements came out, there were a lot of people who were prepared to spend $5K on a pair of speakers and said, to hell with it - the statements cost half as much and have twice as many woofers! I'll give it a shot. I'm not seeing designs recently that have that effect.

 

[HammerSandwich]

re: cardioid, I'd think it makes more sense to do an R1 variation with wide baffle, at least as proof of concept. Once we've seen results from NFS & a few listening tests, we'll have a better idea if cardioid is worth the effort. The DSP tweaks are pretty simple, since it's just baffle-step adjustment, so the work is mostly building one box. Heck, just build a big, radiused, baffle to stick on the standard box. Call it the R1G, as it's a combination of R1, Ggntkt, and Grimm.

 

[Lbstyling]

re: cardioid, I'd think it makes more sense to do an R1 variation with wide baffle, at least as proof of concept. Once we've seen results from NFS & a few listening tests, we'll have a better idea if cardioid is worth the effort. The DSP tweaks are pretty simple, since it's just baffle-step adjustment, so the work is mostly building one box. Heck, just build a big, radiused, baffle to stick on the standard box. Call it the R1G, as it's a combination of R1, Ggntkt, and Grimm.

Agreed.

You will find you likely need to go to a 8inch to get the spl, and it will drop of in spl fast under 150hz (hence the 8C being a 3 way)
I got it working with a 10inch driver well in a test box a few years back.
I found it extremely sensitive to the amount of wool I put in the 'vents'.

On a side note: Rick and everyone else who did work on R1, I just wanted to say you guys are awesome! So many people plan to design speakers like this, and so few manage to see the project through. I hope this community appreciates the level of dedication you have given. I for one certainly do!

 

[tktran303]

Re: F208
It's been done. Its the Javad Shadzi & Jeff Bagby Ceramicos; commissioned by SB Acoustics; same format- 2x8" woofers, 5" midrange, and albeit non-wave guided tweeter.

@617 I guess there's an opportunity there to stand on the shoulder of giants. Why not further the work that's been done to advance the state of the art? ASR has a NFS at its disposal, good designers and builders. Double blinded listening tests is all that's left.
But look, let's not let perfection be the enemy of great.

Remember DIYAudio.com member keyser (Martijn Mensink) started over a decade ago, proceeding on the work done with waveguides (Geddes) and cardioids (JohnK) He later struck gold when he found he was able to damp the rear wave in his cardioid at least 6dB more that previous efforts. He later founded Dutch and Dutch and the rest is history!

I've been in this hobby a long time and it all started with the ProAc Response 2.5 clone 2 decades ago. Since that time I've been very fortunate to own some amazing large speakers like Music and Design's NaO II RS (Cardiod-dipole), Statement II (WTMTW monopole), some medium sized ones like Jim Mitchell's resdesigned Thor (MTM), and some small ones like Jeff Bagby's Revolution Mini (MT), as well as able being able to "re-calibrate" with audiophile speakers like Revel Performa 328Be and Dutch and Dutch 8C, and well as live events like concert halls, festivals and superclubs.

The key to the future of speakers in 2000 was DSP and active power. It only took time to get the costs down; and now they are EVERYWHERE; just look at your local Best Buy or big box retailer- there's bluetooth/wifi speakers all smaller than a size of a carton of milk that outperforms anything that was available in the past.

What the home audio scene was missing was a medium sized/floorstanding speaker. But then came the 8c, and the Kii Audio Three+BXT

So what to next?

 

[617]

I agree with this approach, especially for DIY. Modular construction is easier in several ways, and it allows swapping just one section at a time.


It's worth taking a look at Augerpro's waveguides. The SB26ADC works really well, and the price is right. What we need is a list of CNC/3D-print services that are reasonably affordable & friendly to small-volume projects. There's Speaker Hardware and?


Pretty bonkers, yes. While I like sealed woofers, full-range performance bumps into both Vd & Hofmann. All dBs from VituixCAD at 1M in half-space.

The PTT6 has Vd of 130cc, and a 15L BR/PR version can do 105+dB in the passband with f3 around 40Hz. Put a woofer with 500cc Vd - say an RSS265HF-8 - in a sealed box, and you get 105+dB in the passband with f3 around 40Hz from 35+L. Well, crap. If room gain cooperates, the slower roll-off could make 20-25Hz useful, but it's hardly an improvement at 30+Hz.

So, you're right about needing to go big if you want a sealed box to outperform significantly the R1 in the bass.

Let's step up to the 15" RSS390HF with >1100cc Vd. (And I'll strongly encourage RSS over UM, especially when using higher XO.) If you want to keep the box reasonably small, say 55L, you get Qtc around 0.9 & need 500W to push near Xmax. An 85L enclosure will drop Qtc to 0.8 & allow Xmax with 300W. Go even bigger, and power requirement drops while output stays the same. In all cases, you see 105dB to 25Hz, so f3 reaches 20-22Hz. That's expected, as 1 octave = 4x Vd.

Considering that Rick & Amir don't want to deal with a massive box, plus the benefits of distributed subs, I'd say that ~55L with an RSS315HF-4 or ~700cc equivalent is about the practical limit. That will deliver 105dB above 30Hz with a 32Vrms amp, such as the NC252MP. External dimensions could be roughly 12" x 18" x 24".

I think it's a mistake to priortize fullrange sound even in a large tower speaker. Priortize output at 40hz and above.

Re: F208

It's been done. Its the Javad Shadzi & Jeff Bagby Ceramicos; commissioned by SB Acoustics; same format- 2x8" woofers, 5" midrange, and albeit non-wave guided tweeter.

@617 I guess there's an opportunity there to stand on the shoulder of giants. Why not further the work that's been done to advance the state of the art? That's what DIYAudio.com member keyser (Martijn Mensink) started over a decade ago. He later struck some gold when he found he was able to damp the rear wave in his cardioid at least 6dB more that previous efforts. He later founded Dutch and Dutch and the rest is history! All the best to him

I don't disagree at all! I just want to make sure we aren't producing a science project.

 

[McFly]

I think it's a mistake to priortize fullrange sound even in a large tower speaker. Priortize output at 40hz and above.

After a bit of simulation myself, I think the closest you will get is an all active 3 way, sealed RSS265HF-4 side firing in ~35L from 120hz down, a midbass (sealed or vented) doing 120hz to 2khz crossing to a waveguided tweeter from there. from memory it nets an F10 at 22hz, F6 at 30hz and F3 at 40hz. With room gain that would definitely be classed as "full range".

Caveat is the buy in, requires 3x stereo amps and miniDSP.

 

[D!sco]

I feel like a Dayton driver Revel clone has been done, but an f208 with Dayton RS225-8s is definitely riding a value train. Plus the RS125 woofer always looked like a decent candidate for all kinds of things, really.

Probably my favorite feature of the R1 was the standardized, easy to get box. Something like this tower enclosure, or even this pro speaker box are decent candidates for a larger design.

 

[617]

I feel like a Dayton driver Revel clone has been done, but an f208 with Dayton RS225-8s is definitely riding a value train. Plus the RS125 woofer always looked like a decent candidate for all kinds of things, really.

Probably my favorite feature of the R1 was the standardized, easy to get box. Something like this tower enclosure, or even this pro speaker box are decent candidates for a larger design.

The .56 cubic foot cabinet is the same width as the tower speaker, could stack them. I've built both.

 

[tktran303]

The Dayton RS225 and RS125 have been in dozens of designs. It was a favourite budget beater when it was released a decade ago, including CJD's

diVine Audio

Lots of designs to review/peruse/learn from here:

A Guide to HTguide.com Completed Speaker Designs. - HTGuide Forum

This is a guide intended to help people locate and choose between DIY Speaker Designs completed here at HTGuide's Mission Possible DIY Forum or by friends. These are designs that you can have confidence in. These designs are fully documented and ready for building. These designs were based on...

www.htguide.com

 

[Rick Sykora]

So, have not put up the poll yet. If I had the cardiod idea would have not made it. I am a bit skeptical of the d&d 8c clone for a couple of reasons. Am not sure it meets the initial requirement for enough bass output for a large room (at 3-4 meter LP. Its woofer does not seem more capable than r1 and I know r1 would strain to energize solid bass in a large room. Am also not clear on how it might be extensible.

Am leaning towards slimmer bass module that is tall enough to be a stand for various types of monitor. I also liked the goal to get better directivity below 1 kHz. Anyway, grok on that a while as I will have limited online time for the rest of the week. We have a family wedding and will be hosting some family from out of town.

Cheers,

Rick

 

[JRS]

c

As a long-time DIYer I remember the DIY projects I sort of lusted after when I got into DIY, and many of them were just large tower speakers like Troel's designs or the Statements II or Khanspires. These designs brought a lot of new people into the hobby, and it seems like there was this renaissance of DIY audio which coincided with the availability of inexpensive measurement tools (Omnimic, Soundeasy, ARTA, REW) and inexpensive, high quality drivers (Dayton RS). I'm sure most DIYers here remember those days.

Seeing the DIY scene, it makes me a little sad. A lot of the people I learned from have passed away, most prominently Jeff Bagby and Linkwitz. Others have stepped away from DIY like Zaph. Some look like they're retiring, like the speakerdesignworks guys. As a result, I haven't seen any simple designs that really excited me. Javad Shadzi has some great designs but they use very esoteric drivers for the most part, and Troels is on his own trip; I respect his consistency though.

I think when the Statements came out, there were a lot of people who were prepared to spend $5K on a pair of speakers and said, to hell with it - the statements cost half as much and have twice as many woofers! I'll give it a shot. I'm not seeing designs recently that have that effect.

I hear your pain. And try where I can to generate interest here. And for sure, the hobby is feeling the absence of guys like Bagby, but I think the causes may be more to do with a shifting attention to stacks and headphones, and the whole concept of having a large physical setup seems less important, and certainly more rare. I mean growing up every single one of my friends had a decent stereo--it was like the campfire for cavemen. Now not so much. I wonder also to what extent that people don't seem to work with wood, or even know someone who does. So it's a crying shame--as I was just remarking on another thread, these are (or should be) the halcyon days for DIY audio--not so much electronics--that like cars are becoming more and more applied computer science if you are doing design, and for kits, those resemle model cars that have like 20 parts and an hour to build, instead of the ones I built as a kid.

But speakers: We have this great freeware, ability to make very high fidelity and low cost measurements, a great variety of drivers to choose from, and an increasingly sophisticated understanding of what makes a speaker sound the way it does, and all the fire power one could want for 2 to 4 bucks a watt. So it is puzzling--seemingly a hobby dwindling in this huge sea of aplenty.

I'm really excited to see the Directiva R1 come to fruition, and that it's in a knockdown cab is wonderful. And of course eager to see where this thread takes us. It could be a real giant killer if done right. I do hope that there are some alternate versions that use off the shelf cabinets.

 

[TimVG]

So, have not put up the poll yet. If I had the cardiod idea would have not made it. I am a bit skeptical of the d&d 8c clone for a couple of reasons. Am not sure it meets the initial requirement for enough bass output for a large room (at 3-4 meter LP. Its woofer does not seem more capable than r1 and I know r1 would strain to energize solid bass in a large room. Am also not clear on how it might be extensible.

Am leaning towards slimmer bass module that is tall enough to be a stand for various types of monitor. I also liked the goal to get better directivity below 1 kHz. Anyway, grok on that a while as I will have limited online time for the rest of the week. We have a family wedding and will be hosting some family from out of town.

Cheers,

Rick

Have fun!

The thing is that an additional bass module won't improve R1's pattern control below 1kHz. Another option is to draw inspiration from the Amphion Krypton or Xenon, which are slim 3-way models (passive) with cardioid midrange behaviour. CTRL mentioned he could work on something to predict cardioid behaviour, and in January I'll have my Shaper to do some prototyping.

 

[abdo123]

So, have not put up the poll yet. If I had the cardiod idea would have not made it. I am a bit skeptical of the d&d 8c clone for a couple of reasons. Am not sure it meets the initial requirement for enough bass output for a large room (at 3-4 meter LP. Its woofer does not seem more capable than r1 and I know r1 would strain to energize solid bass in a large room. Am also not clear on how it might be extensible.

Am leaning towards slim bass module that is tall enough to be a stand for various types of monitor. I also liked the goal to get better directivity below 1 kHz. Anyway, grok on that a while as I will have limited online time for the rest of the week. We have a family wedding and will be hosting some family from out of town.

Cheers,

Rick

I think a driver based cardiod like the Kii Three would be a really interesting design.

 

[Biblob]

Making a D&D 8C clone is a sought after idea. Many have tried and some have accomplished. In the thread below a lot experimenting is being done regarding size of vents, damping, backwall distance etc. So many variables makes it hard to accomplish a succesful design, that is comparable to the performance of the D&D 8C. It's not easy to do, but possible, it's just very labor heavy. Simulating, experimenting, measuring etc.

In private messaging @Martijn Mensink recommended to try it the Kii Three way, but in the end that won't be easy to make for a not so experienced person or someone with a limited budget; that way requires many channels of amplification and DSP.

Resistive port cardioid active speaker insipired by D&D 8C

Hey guys, Actually, I've been keeping an eye on D&D 8C active monitor speaker for a while now and after Erin's Audio corner YT review, I'm tempted to try my luck designing a similar active speaker to see what would come up at the end. I have access to many sample drivers so it's needless to...

www.diyaudio.com

 

[Severian]

Sticking with the DXT tweeter seems like a no-brainer given its great success in the R1, all of the work that's already gone into working with it, and the reasonable cost.

 

[Rick Sykora]

Have fun!

The thing is that an additional bass module won't improve R1's pattern control below 1kHz. Another option is to draw inspiration from the Amphion Krypton or Xenon, which are slim 3-way models (passive) with cardioid midrange behaviour. CTRL mentioned he could work on something to predict cardioid behaviour, and in January I'll have my Shaper to do some prototyping.

Why? Generally the bass module contribution is below 200 Hz and even then, could be a dipole woofer like LX521...

Or use more drivers to do ala Kii 3.

 

[TimVG]

Why? Generally the bass module contribution is below 200 Hz and even then, could be a dipole woofer like LX521...

Or use more drivers to do ala Kii 3.

Well, I'm not sure there is much to gained performance wise, except yes, deeper and louder bass. But is this R2 then, or simply an R1 add-on?
There's many options but I'm not sure the Purify is money 'well-spent' if only used above ~200Hz as a midrange. Just my opinion.

 

[Rick Sykora]

Well, I'm not sure there is much to gained performance wise, except yes, deeper and louder bass. But is this R2 then, or simply an R1 add-on?
There's many options but I'm not sure the Purify is money 'well-spent' if only used above ~200Hz as a midrange. Just my opinion.

r1 is (almost) done. While it could use a bass module to get louder too, the plan for r2 was to use less expensive woofers...

Or did I miss something earlier in the thread?