Introducing Directiva - An ASR open source platform speaker project

[ctrl]

2 options come to mind:-

The third optin is to wait until reliable distortion measurements are available for the Directiva r2.

Perhaps down to 100-150Hz these will not be worse than the D&D 8C, where Erin (from erinsaudiocorner.com) confirms that the 8% HD3@100Hz@96dB@1m are not audible.

Then a crossover at 100Hz would be possible if one is willing to accept some harmonic distortion.

 

[abdo123]

Because I am interested in using the 2-way module as a satellite (and who knows, I may not be alone), it would be good if we can identify a neat way to use it as such, while keeping the project goal of being somewhat affordable compared to Purifi. It only needs to get down to 80-ish Hz, or possibly 120 Hz at the very highest, and all in one cabinet (desirable for a satellite speaker).

2 options come to mind:-

• 1. A small, affordable, but adequate bass driver, built into the 2-way module in a compact way.
• 2. Replace the SB15 driver with one capable of handling the task to a lower frequency, at a similar price to the combined price of the SB15 plus the bass driver identified in option 1.

Is anyone on the project team willing to put a little thought into this idea?

thanks

There are thousands of DIY speakers online that satisfy your requirements. I recommended the DXT-MON.

 

[Newman]

There are thousands of DIY speakers online that satisfy your requirements. I recommended the DXT-MON.

Sorry, but no. Neither the DXT-MON nor the rest deliver what the Directiva r2 does. I want the Directiva performance, usable as a satellite speaker to be used with subs.

 

[abdo123]

Sorry, but no. Neither the DXT-MON nor the rest deliver what the Directiva r2 does. I want the Directiva performance, usable as a satellite speaker to be used with subs.

The driver choices have been mulled over for weeks so i doubt things will change at this point. the current -10 dB is @100Hz, a Linkwitz-Riley crossover is -6 dB at the crossover frequency. So it's possible but you will be limited by output.

On the other hand with the DXT-MON you have this:

And with the DXT-MON 182 you have this:

 

[TimVG]

A better driver wouldn't really help in this regard. Think of trying to make a ported sub play below its tuning frequency - it just doesn't work well.

It is possible to get passive controlled directivity behaviour at lower frequencies, but it would require a complete redesign, and would most likely negate some or most of the positive attributes we have achieved now. It would most definitely result in a bigger loudspeaker.

On the other hand, as ctrl mentioned, if you can live with some added distortion, perhaps have a bit of gain in the lower region and use careful placement you may reach the point where you could cross over to a sub. No promises though.

 

[Newman]

A better driver wouldn't really help in this regard. Think of trying to make a ported sub play below its tuning frequency - it just doesn't work well.

I thought the better analogy would be a dipole sub, where short-circuit cancellation is the issue, and a better driver *does* help.

 

[Newman]

The driver choices have been mulled over for weeks so i doubt things will change at this point.

I am not asking for the R2 design to change, for using on top of a bass module. That is the R2 concept.

I am simply asking how it would most optimally be reconfigured for use as a satellite crossing to a sub.

TimVG has already said, on this very issue, that using a much less gutsy/cheaper bass module might be the go. So we could think of this option as not being a variation to the R2 module, but a variation on its bass module. And, since I think of satellite speakers as a single box, and with the option for on-wall use, my initial thought is for this particular bass module variant to be integrated with the R2 cabinet, eg:-

• Add another 6" bass driver below the SB15, and
• simply extend the R2 box dimensions a further 6" downwards with no other changes, and
• internally block off the cabinet between the SB15 and the new driver, creating a sealed sub-box, and
• EQ the output of the third driver actively (just like the originally-conceived bass module).

The key question then becomes what 6" driver is both economical and competent enough for the job?

And if the answer adds enough to the total driver cost (eg a second SB15 adds US$80), I think a sub-question arises, namely, what if that 2x $80 was put into a more gutsy single driver to replace the R2's SB15 and that could go down to 80-100 Hz even with the cardioid vents. What might that driver be? The 18 Sound 6ND430 is US$150, for instance, and is 92.5 dB/W and 200+W power handling. Good idea, bad idea?

the current -10 dB is @100Hz, a Linkwitz-Riley crossover is -6 dB at the crossover frequency. So it's possible but you will be limited by output.

On the other hand with the DXT-MON you have this:

DXT-MON /182 excellent speakers have long been on my radar, so I know they have plenty of bass. And although they also have good directivity control, it is no Directiva. I am simply exploring the option of having my cake and eating it too. Sometimes it can happen, sometimes it can't.

My gut feeling is that it *can* happen in this instance, so I am asking for input.

 

[TimVG]

And if the answer adds enough to the total driver cost (eg a second SB15 adds US$80), I think a sub-question arises, namely, what if that 2x $80 was put into a more gutsy single driver to replace the R2's SB15 and that could go down to 80-100 Hz even with the cardioid vents. What might that driver be? The 18 Sound 6ND430 is US$150, for instance, and is 92.5 dB/W and 200+W power handling. Good idea, bad idea?

Unfortunately it won't work that way - while it is possible to shift working range of the cardioid system - it will lead to different compromises in the arguably more important lower mid-range. It's not simply a matter of putting in a more capable driver since it is the ports themselves which contribute to the distortion.

In my opinion there are also much better alternatives if you're looking for an on-wall speaker than the R2 top module.

 

[Newman]

Thanks Tim, don’t be afraid to actually name the “much better alternatives”!

 

[TimVG]

Thanks Tim, don’t be afraid to actually name the “much better alternatives”!

Well since you mentioned Heissmann, have you looked at the wavewall?

And don't get me wrong, in theory R2 should be compatible with near- or on-wall placement, but I haven't checked it out in practice yet - a small bass module would really assist though. Something like an Exodus Anarchy, or there's the new(ish) Dayton Epique extended range woofers.

Since 200Hz is still in the modal range of quite a bit of rooms, placing the bass module in the vicinity of the top module should be sufficient, you'd be responsible for integration and EQ though. I suspect anyone who builds this will have access to a measurement microphone.

 

[howard416]

It's quite a little speaker isn't it?

I think we can mitigate diffraction a bit more by using a larger roundover (I only had an R6,5 roundover bit around, R13 would be better still) according to the sims, and by using more appropriate screws on the DXT (had to use what was around, again) and covering the ones in the waveguide with bits of tape, maybe @Rick Sykora will try one or more of these 'tweaks'.

Seas DXT Tweeter

 

[Rick Sykora]

Seas DXT Tweeter

Thanks, info is pretty dated , but still interesting.

 

[D!sco]

Maybe I'm wrong, but wouldn't the cardioid effect make it easier to place the monitors around a room, on walls, different heights etc. without so much interference from the room itself? This kinda sounds ideal for home theater. I could even see the 200hz-20khz monitors being useful as side or rear channels without the bass module. Definitely would want bass extension for the LCR channels, but still. And at the current price point the monitor alone is very doable. I hear the arguments against, but there are some interesting experiments to be done. Again, super exciting project. Probably the most interesting thing happening in DIY at the moment.

Plus, if the bass module is adjustable, what's stopping the individual from crossing dual subs up to, say 250hz? Cars audio does it. Probably not the best for sub-40hz information, but that's a different kind of issue IMO

 

[hex168]

Unfortunately it won't work that way - while it is possible to shift working range of the cardioid system - it will lead to different compromises in the arguably more important lower mid-range. It's not simply a matter of putting in a more capable driver since it is the ports themselves which contribute to the distortion.

In my opinion there are also much better alternatives if you're looking for an on-wall speaker than the R2 top module.

I understand it would be a completely different design, but could you control directivity in the lower mid by using a 10" or 12" mid-bass driver and use the cardioid cabinet to reach down to 80 or 100 Hz? Of course, once the cabinet gets that much wider, a larger waveguide than the DXT is also possible. Just spitballing for a cardioid/waveguide two-way for the use case of meeting a subwoofer without compromise. (But other that that, exactly the same speaker, right?)

 

[Rick Sykora]

I understand it would be a completely different design, but could you control directivity in the lower mid by using a 10" or 12" mid-bass driver and use the cardioid cabinet to reach down to 80 or 100 Hz? Of course, once the cabinet gets that much wider, a larger waveguide than the DXT is also possible. Just spitballing for a cardioid/waveguide two-way for the use case of meeting a subwoofer without compromise. (But other that that, exactly the same speaker, right?)

Always open to possibilities for Directiva, but as I think you allude, a large midbass is yet another speaker project (which I recall has been done already on DIYAudio). r2 is moving into the bass module integration and we will see if the proposed design is viable.

 

[howard416]

Thanks, info is pretty dated , but still interesting.

Well, it at least addresses the assembly screw counterbore holes that TimVG mentioned.

 

[Rick Sykora]

Maybe I'm wrong, but wouldn't the cardioid effect make it easier to place the monitors around a room, on walls, different heights etc. without so much interference from the room itself? This kinda sounds ideal for home theater. I could even see the 200hz-20khz monitors being useful as side or rear channels without the bass module. Definitely would want bass extension for the LCR channels, but still. And at the current price point the monitor alone is very doable. I hear the arguments against, but there are some interesting experiments to be done. Again, super exciting project. Probably the most interesting thing happening in DIY at the moment.

Plus, if the bass module is adjustable, what's stopping the individual from crossing dual subs up to, say 250hz? Cars audio does it. Probably not the best for sub-40hz information, but that's a different kind of issue IMO

You can cross higher than 80 or 100 Hz but risk potential localization issues. Some of this depends on the location, but other things like high order harmonics can affect it too. The car situation is a pretty unique one.

I have struggled with localization of much higher frequency sounds in a car. While it is all acoustics in the end, unless your home is a glass-walled pod, a typical room is a very different space.

 

[TimVG]

Thanks, info is pretty dated , but still interesting.

I'd also mount it with the screw holes facing the oblique angles

 

[TimVG]

Maybe I'm wrong, but wouldn't the cardioid effect make it easier to place the monitors around a room, on walls, different heights etc. without so much interference from the room itself?

No you're not wrong at all in theory (don't know about heights though, this is still a traditional 2-way speaker).
Here's a good thread on the subject.

 

[K31z0]

Have you considered that the top module needs a bass module for it function properly, since it does not play well below ~200Hz?

Thank you for pointing this out, yes I am aware of this. I am currently looking for a compact monitor that can be mounted on or near the back wall in my home theater setup. I don't currently have a subwoofer, but am considering two to four compact Dayton RSS210-8 8" woofers in several closed cabinets (possibly two of each impulse compensated). These will then be driven by my Denon X3300 AVR, which is equipped with Audyssey MultEQ XT32.
I currently do own a three way speaker with a sidemounted 8" Woofer that is crossed at 480hz to the 4" Coaxial driver. The bass blends in very nicely, unfortunately it might be to big after the birth of my twins.

This ist the speaker that i currently own, you can find more details here. With Directiva R2 i hope to find a solution for a small speaker for my subpar position for my new speakers. I think i'll have to start a new thread on this topic.
Thanks for your comments and ideas.