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Directiva r2 project: market requirements gathering

Rick Sykora

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The current r2 proposal is for a premium quality (not price) speaker capable of substantial low bass (mid 40 Hz) into a large room.

UPDATED: 27Oct2021

Another contemplation was to use a coaxial mid/tweeter driver for r2. Was started on another thread, so have asked to move here...
 
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Rick Sykora

Rick Sykora

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Requirement(s )added October 26, 2021 - Speaker placement, amplification; updated amplification requirements on November 1.


Requirements for Directiva r2
  1. The r2 speaker should be active and simple to build. It will utilize a bass module and a upper monitor module. Use of commercially available cabinets (notably for the monitor) is preferred if possible.
  2. The design should be reusable and extensible to allow for design variants. There are 2 main extensible aspects that are expected. One stems from the separate bass module and the other is scalability of the bass module (mainly, but not exclusively) for greater output.
  3. Minidsp 2x4 HD should be used as the active crossover for design and costing purposes
  4. The speaker design may require substantive power for active filtering and low impedance drivers. As such, the design is not required to operate with low power amplification.
  5. The Seas DXT tweeter is to be re-used from r1 unless design team finds a less expensive substitute(s) with better performance.
  6. Bass extension is targeted to be comparable to r1, but the bass module should provide additional bass output to allow for use in rooms up to 150 cubic meters. Listening distance is targeted to be 3-5 meters. The monitor module itself can have less bass extension than r1 to allow for use with existing subwoofers or other bass modules.
  7. The bass module should be designed for accurate bass reproduction and low distortion. A sealed cabinet design is preferred.
  8. The design may include passive crossover circuitry to help reduce the number of active channels and allow for a passive version of the monitor section.
  9. Directivity should exceed r1. The primary requirement is for more consistent directivity over a more extended frequency range. Extensibility of bass module design may consider use of variable directivity, but this is NOT a primary requirement for r2. For the monitor, custom waveguides should be avoided.
  10. The base speaker should be able to have good overall performance whether it is located closer to a wall or out into the room.
  11. The cost target for the drivers and crossover would be approximately $1600 US retail per pair. This cost includes the cabinets, and active crossover but NOT the amplification.
  12. The combined cabinet volumes should be 60-75 liters or smaller. Combined height should not exceed 1.2m
  13. The monitor module should be no wider than 50 mm more than the midwoofer used and the bass module should be wide enough to allow monitor to be securely fitted on top. The target width of the bass module is a maximum of 260 mm.
  14. The electronics should be external, but the modules may consider added volume (above stated target) for those who prefer internal active electronics.
  15. The design tools should be free but flexible enough to allow external data import/export. Plan to continue with VituixCAD and REW.
  16. The design should be openly shared and FOR NON-COMMERCIAL USE ONLY.
As the main Directiva r2 stakeholder and project lead, questions or comments should be directed to me.

The deadline for comments is October 31 and plan to finalize the requirements by November 1.

Thanks!

Rick
 
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D!sco

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Alternatively, SEAS and SB Acoustics both have coaxial drivers available for ~$400/pair. For a directivity > all design, these would probably be more economic choices if a full box redesign is in order. There are also crossover swaps available for lower cost KEFs, like the Q150.

That said, going coaxial is how I have been considering approaching directivity in my next living room build. The SB Acoustics series in particular seems like a great way to get into tower-style builds with a slim baffle and easy good looks/tuning. They even have an identical series of woofers for stacking up series/parallel arrangements. If there's more effort into Directiva once this project is done, would coaxial drivers be considered?
 

hex168

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Alternatively, SEAS and SB Acoustics both have coaxial drivers available for ~$400/pair. For a directivity > all design, these would probably be more economic choices if a full box redesign is in order. There are also crossover swaps available for lower cost KEFs, like the Q150.

That said, going coaxial is how I have been considering approaching directivity in my next living room build. The SB Acoustics series in particular seems like a great way to get into tower-style builds with a slim baffle and easy good looks/tuning. They even have an identical series of woofers for stacking up series/parallel arrangements. If there's more effort into Directiva once this project is done, would coaxial drivers be considered?
Not to poach too much on what Sigberg Audio has graciously shared with us, but the SICA coaxs look intriguing. Possibly the 6.5" would be sufficiently different from his offering?
https://en.toutlehautparleur.com/ha...-pouce.html?___store=tlhp_en&___from_store=v2
 

D!sco

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Yeah, something like that would be an awesome candidate for a 2 or 3-way design. Basically, something like the SEAS King Roy for the common man. Amir never got a SEAS Loki to test, did he? As attractive as the Purifi driver is, it's got a high price, and that keeps me from wanting to experiment.
 
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Rick Sykora

Rick Sykora

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Alternatively, SEAS and SB Acoustics both have coaxial drivers available for ~$400/pair. For a directivity > all design, these would probably be more economic choices if a full box redesign is in order. There are also crossover swaps available for lower cost KEFs, like the Q150.

That said, going coaxial is how I have been considering approaching directivity in my next living room build. The SB Acoustics series in particular seems like a great way to get into tower-style builds with a slim baffle and easy good looks/tuning. They even have an identical series of woofers for stacking up series/parallel arrangements. If there's more effort into Directiva once this project is done, would coaxial drivers be considered?

I am interested in doing something with a good co-axial. I know @ctrl has some ideas in that regard too.

I am most interested in a small tower with sufficient bass for larger rooms. Maybe a couple of woofers and the coaxial does the mid to upper duty. :cool:
 
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Rick Sykora

Rick Sykora

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This is a placeholder for the next iteration of Directiva....

NOTE: The original of this post and the following one were consolidated into the first post to fix sequencing issue from posts moved from an older thread.
 
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alex-z

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Salvaging drivers from KEF Q150 to serve as mid/tweeter seems like the most practical approach. Pretty much all the non KEF coaxial drivers seem to suffer from high tweeter distortion, or a lack of uniform frequency response. Some of them get close to being good, but still suffer from little details like the moving waveguide problem.

Dayton RSS265HF-8 seems like an ideal woofer candidate. A 1.67ft sealed box puts the -3dB point at 38Hz. Might need to double up for sensitivity, but the cost isn't prohibitive. Only real downside is the size, would make for rather large floor standers.

Not sure how good the off-axis response is, but crossing over at 320Hz puts it within the quarter wavelength range so it should work.
 

dc655321

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Salvaging drivers from KEF Q150 to serve as mid/tweeter seems like the most practical approach.

Good call! Mine are scheduled for delivery tomorrow :cool:

Accessories4less has refurbs for $340. Was too tempting to pass up..
 

briskly

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This means would likely be sealed design btw.
What's the opposition to going vented in a 3-way? Are you dead-set against a steep HPF response?
Sica 6.5" was measured at Dibirama. Much more usable FR than most pro coax drivers, for sure. Tweeter THD appears to be the major weak area.
Those THD readings are suspicious. Actual driver distortion is likely lower than measured. See the SB26CDC measurement for a clearer example, although this pattern is found throughout: distortion follows SPL too closely. On that note, the distortion sweeps from the Voice Coil test bench are also a bit off. Vance's mic isn't suited for near-field recording of high-power drivers.
 

eddantes

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Why not an ASR version of the R5? Woofer-Coax-Woofer

Also - SB and Seas coaxes are still very expensive, any interest in something a bit more downmarket? After all - there's more drivers and thus more cost.
 

headshake

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How about the SB Acoustics SB16PFCR25-4 COAX alone or with a SB Acoustics SB17NRX2C35-4?

 

alex-z

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The tweeter in the SB16PFCR25-4 coax has good directivity matching in the 2500-4000Hz crossover region. Unfortunately it seems to fall apart even at 20 degrees off-axis if the datasheet is right.
 
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Rick Sykora

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What's the opposition to going vented in a 3-way? Are you dead-set against a steep HPF response?

Those THD readings are suspicious. Actual driver distortion is likely lower than measured. See the SB26CDC measurement for a clearer example, although this pattern is found throughout: distortion follows SPL too closely. On that note, the distortion sweeps from the Voice Coil test bench are also a bit off. Vance's mic isn't suited for near-field recording of high-power drivers.

My general approach is there is usually more than one good solution to a problem. For r1, the woofer was chosen and is inherently a better vented woofer. We contemplated a sealed design but abandoned due to the woofer. Later, applying the power of an active design and a Linkwitz transform, found that a sealed design was more achievable than we previously thought.

Generally, a sealed alignment will result in cleaner bass and allow a smaller cabinet. So suggesting we start there. Some woofers are middling enough that could be used either sealed or vented. In the end, if you prefer vented and the woofer chosen is not optimal, change the woofer. Part of the goal of the Directiva project is to encourage choices and share the results. Any given design may have more or fewer good options, but that is simply another choice between a derivative or a new design. :cool:
 
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mcdn

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While it might be more of a 'Directiva R1.5', a sealed version of R1 would be a nice small step of evolution.

It would allow some work on sealed bass without having to start from scratch with a new cabinet. It's kind of a principle of product design that small iterations lead to better results. By holding more things constant you can see the effects of the changes you _are_ making more easily.

From there you could go to a different woofer, a tower cabinet, a coax mid/high, etc. But just removing the PR from the R1 seems like the easiest first step.
 
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Rick Sykora

Rick Sykora

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Salvaging drivers from KEF Q150 to serve as mid/tweeter seems like the most practical approach. Pretty much all the non KEF coaxial drivers seem to suffer from high tweeter distortion, or a lack of uniform frequency response. Some of them get close to being good, but still suffer from little details like the moving waveguide problem.

Dayton RSS265HF-8 seems like an ideal woofer candidate. A 1.67ft sealed box puts the -3dB point at 38Hz. Might need to double up for sensitivity, but the cost isn't prohibitive. Only real downside is the size, would make for rather large floor standers.

Not sure how good the off-axis response is, but crossing over at 320Hz puts it within the quarter wavelength range so it should work.
Unless KEF markets the driver for DIY use, am hesitant to use something that has limited availability and/or lifecycle issues. If we put major effort into a reusable design, do not want to get to the end and find out the driver is unobtainable. That said, have at it as a side project!

Have looked at the Dayton and agree that it is attractive and so is the RS225. Both @ctrl and I have RS225s already. As you mentioned, it is kind of big, so will keep on the list for now. Thanks!
 
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Rick Sykora

Rick Sykora

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I also have Dayton ES180s that might be a better fit as far as size goes...

Not sure what the plans are with it is as the E180HE is newer and seems to overlap despite the being a "subwoofer".
 

eddantes

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I would love to see the Denovo 1.16 cabinet employed. Those of us with limited skills/equipment would love this shortcut. But at 8" front - woofer selection is limited unless it's side firing... or wide-n-short
 
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