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Directiva r2 project: market requirements gathering

JRS

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How do you like the Kairos/Adelphos? Always wanted to build one.
I have only built the Kairos. It is an outstanding speaker. The build was for a friend, but before it left home I took the opportunity to measure the drivers and implement a biamped/DSP'ed version of the same. It was a question that had been kicking around in my mind for a while as to whether a really well done passive XO could be improved upon (or even equaled--that being the POV of many who prefer analog vs digital XO's.)

I made no effort to target the FR of the analog version, but just aimed for flat as I could make it. (The analog version was perhaps +/- 2 from 50 upwards anyway). I could not A/B instantly as there was wiring of the XO to deal with. In any event I couldn't pick a clear "winner"--whatever differences were minor. I consider that testimony to how good the design was, and posted over at Tech Talk to that effect, congratulating Jeff for a job very well done. As always he was most gracious, though I believe he was surprised, and perhaps even a wee bit skeptical that the active was as good. Whereas I of course held the opposite view.

It has a fine bass response as is, but if one wanted to kick up their heels, the strain on the little 7" Satori would become evident with LF heavy material. I believe that would be a helluva system for the price.

Edit: One thing I forgot to mention is that Jeff used a first order XO in keeping with the goal of exceptional phase response while I used 96dB/octave linear phase FIR filters.
 

BenB

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I'd be interested in collaborating on speakers that do something few commercial products are doing (or doing well, anyway). My current areas of interest are for optimizing on-wall speakers (whether they be bookshelves or towers), or creating a speaker with variable (user controllable) directivity. Other options may pique my interest as well, but it would have to be something atypical.
 

JRS

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The success of the directiva hinged on the constraints chosen early in the project. Decide now, active vs passive and how big.

My suggestion. Copy the driver sizes of revel f206 or 208.

2x Sb17nbac-4 in series
1x sb15mfc or other mid
1x seas dxt

I've simulated this speaker and the bass would be excellent.


Or if you want to get drivers from parts express:
2x rs225-4 in series
1x rs150p or something else
Wavecor horn loaded tweeter or maybe peerless dx34 corundum dome. Or DXT.

I've been working off and on with this idea for a while and I think the rs225, sb17 and sb23 are your best passive tower woofer values.

Another good option is a rs270p sealed, for a small classic shaped speaker like a JBL century.

If you want to do wide dispersion there is a very intriguing new satori dome tweeter.

I would recommend avoiding coaxial, the only options available to diyers are pretty mediocre compared to what you can get with a cheap mid and tweeter.
Or
The success of the directiva hinged on the constraints chosen early in the project. Decide now, active vs passive and how big.

My suggestion. Copy the driver sizes of revel f206 or 208.

2x Sb17nbac-4 in series
1x sb15mfc or other mid
1x seas dxt

I've simulated this speaker and the bass would be excellent.

Or for a big speaker:

2x sb23nbac4 in series
1x sb17mfc or something else
Dxt

Or if you want to get drivers from parts express:
2x rs225-4 in series
1x rs150p or something else
Wavecor horn loaded tweeter or maybe peerless dx34 corundum dome. Or DXT.

I've been working off and on with this idea for a while and I think the rs225, sb17 and sb23 are your best passive tower woofer values.

Another good option is a rs270p sealed, for a small classic shaped speaker like a JBL century.

If you want to do wide dispersion there is a very intriguing new satori dome tweeter.

I would recommend avoiding coaxial, the only options available to diyers are pretty mediocre compared to what you can get with a cheap mid and tweeter.
Or for really big how about the Elsinore with it's 4 6.5" drivers (DIY project initiated in 2007 and now 425 pages in length). Only instead of the Peerless drivers, 4 SB17xxxx. IIRC its a 2.5, and the tweeter is a WG augmented Vifa VF-25. The upper and lower woofers extend the bass and fill in the baffle step compensation.

https://www.diyaudio.com/forums/multi-way/97043-elsinore-project-thread-423.html
 

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mcdn

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I'm still liking the idea of bass modules, if only for the flexibility it would give to mix and match different ideas and approaches. If @ctrl wants a real modelling challenge how about something with pattern control like the W371A? Combine with a lower cost (non Purifi) version of the R1 on top and the price/performance would be incredible.
 

JRS

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In case I wasn't clear^^^. And I already have some modules,:)
 

McFly

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LF - MF pattern control is difficult in small enclosures without going full D&D cardiod vent style, not so DIY friendly but certainly doable.
 

fluid

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I'm still liking the idea of bass modules, if only for the flexibility it would give to mix and match different ideas and approaches. If @ctrl wants a real modelling challenge how about something with pattern control like the W371A?
It would not be much of a challenge to ctrl to model this in Vituix or ABEC, the basic principle of an active cardioid is relatively simple. A low pass filter on the rear driver with the correct amount of group delay or digital delay to match the time of flight from the front. Fine tuning the depth and filter for specific drivers through simulation would be much the same process as it was with baffle options for r1.

Attached is my mockup of a W371 ish layout using 15" drivers. I cheated a bit and used a 2nd order FIR and digital delay but it works almost as well with an IIR filter. A low slope FIR like this can be made accurate enough with not that many taps and only 10ms of latency. This is intended to replicate the continued directivity mode where it is cardioidish until about 100Hz where it goes back to full omni to avoid losing all the low bass.

What is impressive about the W371 is the software to measure the speaker in situ and get the desired patterns without any user knowledge or effort. Doing it manually is easy enough but more time consuming.
 

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abdo123

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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?

Edit: simple calculation based on Qts and Vas suggest 424 liters or 15 cubic feet! :p

Edit: that F10 at 14.3 Hz SEALED sure screams end-game to me though.

1634022344014.png
 
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tktran303

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It’s all volume displacement limited. What that means is your SPL at a frequency is dependant on how much volume of air you can move.

So Full range; we’ll that depends for what listening material and what distance and loudness you need?

Music in a bedroom eg. Eg. 40Hz and 85dB.
Dinosaur footsteps or crashing UFOs in a movie theatre? 20Hz at 100+dB

Synth bass in a Nightclub or Superclub. 16Hz;
120dB.

Most people think a Sonos sub is all you need.

Some people don’t think subwoofers don’t get interesting until you get a few 18”s in a tapped horn, and sealed is just boring and inefficient.

see data-bass.com
 
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Rick Sykora

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While fantasizing is just fine, want to be clear that I do not have space for any monstrosities. For that matter, Amir would not be able to measure it either.

The r2 target should be something no more than the size of a Revel F206 for a floorstaander. Am still keep an open mind to a bass module, but thinking something the size of a B&W 801…

If it needs 250 watts or more to get decent bass output, am good with that too. :)
 

abdo123

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While fantasizing is just fine, want to be clear that I do not have space for any monstrosities. For that matter, Amir would not be able to measure it either.

The r2 target should be something no more than the size of a Revel F206 for a floorstaander. Am still keep an open mind to a bass module, but thinking something the size of a B&W 801…

If it needs 250 watts or more to get decent bass output, am good with that too. :)

well since you raised the bar so high with the r1 (flat to 40Hz) i feel it's only natural that it's successor would go even lower with similar or higher max output.
 

JRS

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It’s all volume displacement limited. What that means is your SPL at a frequency is dependant on how much volume of air you can move.

So Full range; we’ll that depends for what listening material and what distance and loudness you need?

Music in a bedroom eg. Eg. 40Hz and 85dB.
Dinosaur footsteps or crashing UFOs in a movie theatre? 20Hz at 100+dB

Synth bass in a Nightclub or Superclub. 16Hz;
120dB.

Most people think a Sonos sub is all you need.

Some people don’t think subwoofers don’t get interesting until you get a few 18”s in a tapped horn, and sealed is just boring and inefficient.

see data-bass.com
I had two 2" P-P 18"ers in an IB arrangement that was flat into the teens. Watching the windows flex was interesting for a while, feeling the floors shake much less so. Now I confine bandwidth to a more sensible high 20's (and don't tack drivers to what passes as modern home building).
 

D!sco

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well since you raised the bar so high with the r1 (flat to 40Hz) i feel it's only natural that it's successor would go even lower with similar or higher max output.
Probably with emphasis on the output. It would be nice to get low distortion at theater volumes. I also feel like accessibility is a size issue as well. Deep extension and high volumes require large enclosures.
 
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Rick Sykora

Rick Sykora

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617

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Lbstyling

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Was on my bucket list until I found out how much open space the LX521 needs.

Not sure how much community interest there is either…

Maybe time for a poll.
No no....wrong end of the stick.

A la one of the best measuring speakers ever made: the D+D 8c.
Works best against a wall. Uses the same DXT tweeter you used in the R1 if I remember right.

The cardioid design narrows the dispersion of the mid driver (it's an active 3 way) to bridge smoother directivity transition between tweeted and bass.

Your half way there with the R1 design already. The cardioid calculation is actually very simple as you can see the entire thread on how the 8C was interested in DIY audio in detail. The advantage for D2 is that the competition is $20k, making DIY very competitive. It's important to remember that making a design cardioid in of itself does not raise the cost of a build either.
Do what you like, but I would design it to be only used down to 100hz (as a 2 way as efficiency drops fast with frequency in a cardioid) and build a bottom cab 'sub' that can be purchased/build separately.

The mid enclosure just has the back wall located as close to the mid driver magnet as you can and a couple of inches of insulation against the inside of the holes on the sides if i remember right.

If I wasn't so busy with work I would be setting a company up to do this right now to be honest.

DIY audio member 'Keyser' created the 8c with the experiments here I think:

 

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