Directiva r2 monitor prototype build

[RickS]

Is the team still using the 5” ceramic SB Acoustics woofer?

No, we are using the SB15NBAC30-4.

 

[Inertiaman]

No, we are using the SB15NBAC30-4.

So is this a firm commitment to this SBA mid/woofer model?

I noticed in the other thread that other mid/woofer drivers (like SiG180) seemed to be the front-runner as recently as late March. I realize this is all volunteer work and there are no guarantees; I'm just trying to confirm my perception of the current plan, to the extent there is one.

I'm placing a large-ish order for drivers for a different project and it would be a convenient (and well priced) opportunity to get the SB15NBAC30-4 and the DXT tweeters. I will patiently wait for the crossover design to settle out, and realize it may be weeks/months/seasons before its "done", but it would be great if you could let me know your confidence the SB15NBAC30-4 will not change.

Thanks for all your effort on these designs, they have been great learning.

EDIT: or am I wrong in perceiving "budget Directiva" and "Directiva R2" to be the same project??

 

[somebodyelse]

Different projects as I understand it. This one has the SB15NBAC30-4 with a passive cardioid, to be used with a bass module / subwoofer as it rolls off blow ~100Hz. The SiG180 is proposed as a cheaper replacement for the Purifi driver in something close to the original Directiva design, going low enough that you may not feel the need for a subwoofer. That's why the measured Fs of the SiG180 being significantly higher than the datasheet says is an issue.

 

[RickS]

So is this a firm commitment to this SBA mid/woofer model?

I noticed in the other thread that other mid/woofer drivers (like SiG180) seemed to be the front-runner as recently as late March. I realize this is all volunteer work and there are no guarantees; I'm just trying to confirm my perception of the current plan, to the extent there is one.

I'm placing a large-ish order for drivers for a different project and it would be a convenient (and well priced) opportunity to get the SB15NBAC30-4 and the DXT tweeters. I will patiently wait for the crossover design to settle out, and realize it may be weeks/months/seasons before its "done", but it would be great if you could let me know your confidence the SB15NBAC30-4 will not change.

Confirmed. Stick to the 4 ohm. SIG180 is too large to be a substitute.

Thanks for all your effort on these designs, they have been great learning.

EDIT: or am I wrong in perceiving "budget Directiva" and "Directiva R2" to be the same project??

Separate projects, the budget one is closer to r1 than r2.

 

[hex168]

Confirmed. Stick to the 4 ohm. SIG180 is too large to be a substitute.



Separate projects, the budget one is closer to r1 than r2.

Your work on this is appreciated! Is the SIG180 too large because of cabinet size constraints, or the cardioid effect cannot be achieved over the needed band, or something else?

(I'm hoping to follow along on how this is designed, and then take a shot at something similar but with higher output. I guess I'll see if that will be possible. The Lavoce DF10.144LK, not out yet, looks very promising on paper. )

 

[RickS]

Your work on this is appreciated! Is the SIG180 too large because of cabinet size constraints, or the cardioid effect cannot be achieved over the needed band, or something else?

mainly cabinet size and also design constraints for achieving directivity target.

(I'm hoping to follow along on how this is designed, and then take a shot at something similar but with higher output. I guess I'll see if that will be possible. The Lavoce DF10.144LK, not out yet…

I recall @ctrl posted something he did with higher output.

 

[RickS]

IF you were wondering why r2 is dragging out, along with team member bandwidth, we are struggling to precisely define the type and quantity of damping material needed. Along the way, will also likely modify the side vents. Until this is done, am holding of building a prototype to submit to Amir.

I regret the slow progress but am using the time to improve my speaker measurement rig. Have just created a new rotating base and working on the stand this week.

 

[Morpheus]

IF you were wondering .... we are struggling to precisely define the type and quantity of damping material needed.[\QUOTE]

Thanks for the update Rick. That aspect of the desigh is the "raison d' être" of the whole project and its distinctive feature, so we appreciate that getting it right and precisely reproductible for anyone that tries to build one is key.
In that vein, I think that if you could make that work with globe wide available brand products, like for example example 3M stuff, it would help a lot. It might increase cost, but that way, even if you are starting in DIY and dont have a proper measurement rig or knowledge to verify compliance, you could be sure to get the same results, and would make sourcing and applying it easier, wherever you are located.

 

[RickS]

The global target has been the goal but looks as though we may need to diverge from it. However, with team members in multiple regions, we should be able to optimize for major regions. In any case, once we figure it out, impedance curve matching should help ensure builders closely reproduce with local materials. .

 

[RickS]

As it turns out, mineral wool and some of the alternative materials are pricey and need to buy way more than is need for a small speaker. So, along with needing to add some bass support, the r2 monitor prototype is shipping back to me for a major overhaul.

@Justin Zazzi did some helpful baselining that should help ensure my new spin gear measures accurately. I apologize for slow progress but we set some higher goals for r2 and has taken longer than hoped to determine how to implement. When I get the prototype back, it will be my top priority to drive to completion.

Sincerely,

Rick

 

[RickS]

The prototype arrived and started to work on it over the weekend. My first task is to replace the side panels. After reviewing the initial results and checking sims, we decided to replace the 4 slot configuration with one larger one. Along with making for a simpler cabinet, the sims suggest it should be a bit smoother....

The above is the original slot configuration and this is the new one...

As mentioned, I plan to add a small bass module to make it a small 3-way. Before that will be doing some spins to optimize the damping material.

 

[terryforsythe]

As it turns out, mineral wool and some of the alternative materials are pricey and need to buy way more than is need for a small speaker.

Fiberglass insulation works pretty well (remove the backing). It performs about as well as rockwool according to the video for which I posted the link below. I used it and I am happy with the results.

See the video starting about 4:20.

 

[Fledermaus]

The above is the original slot configuration and this is the new one...

As mentioned, I plan to add a small bass module to make it a small 3-way. Before that will be doing some spins to optimize the damping material.

Would love to see those displayed, since I'm tinkering with a similar project (2-way mid-high frequencies speaker w/resistance enclosure mid box for controlled directivity)...

Among current sims :

 

[RickS]

Fiberglass insulation works pretty well (remove the backing). It performs about as well as rockwool according to the video for which I posted the link below. I used it and I am happy with the results.

See the video starting about 4:20.

Interesting video, thanks for sharing.

Yes, would expect fiberglass to be comparable to rockwool. However, it is a nasty eye, skin and lung irritant so I avoid it for speaker design. If someone is just building a speaker and the exposure is minimal, have less issue recommending to them.

Also, unlike more traditional boxes, there is no simulation for a damping a passive resistance enclosure. So expect I will be handling damping material much more as I test. So, fiberglass is voted out of contention. I plan to use Acousta-stuf and will likely mix with some open cell foam. Both materials are reasonable cost and available in smaller quantities.

 

[Morpheus]

Fiberglass insulation works pretty well (remove the backing). It performs about as well as rockwool according to the video for which I posted the link below. I used it and I am happy with the results.

See the video starting about 4:20.

HI, Rick has answered this already, but as a doctor, let me emphasize this : Do NOT use fiberglass on speaker filling, other than closed boxes, but even then, I would never do it , (if you do, used appropriate protection, at minimum N95 mask, goggles, gloves, gown when opening it ) With manipulation, vibration and degradation over time, it continuously breaks in microscopic shard that is a health hazard, for skin, lung especially, an eye. Its not nearly as bad as asbestos wich is a direct carcinogenic, but it will still provoque itching, asthma, bronchitis and chronic obstrutive lung disesase, as those microscopic glass spiculated shards get stuck in the epithlium and cause chronic inflamation.
Leave this stuff alone, it is acceptable for professional handling with protective gear and specific applications, like hull manufacturing, bodyshop/fairing or surfboard production, but Not including speaker filling.

 

[terryforsythe]

HI, Rick has answered this already, but as a doctor, let me emphasize this : Do NOT use fiberglass on speaker filling, other than closed boxes, but even then, I would never do it , (if you do, used approtiate prote ction, minimum N95 mask, goggles, gloves, gown when opening it ) With manipulation, vibration and degradation over time, it continuously breaks in microscopic shard that is a huge health hazard, particularily for skin and lung, an also eye. Its not as bad as asbestos wich is a direct carcinogenic, but it will still provoque asthma, bronchitis and chronic obstrutive lung disesase, and skin allergy.
Leave this stuff alone, it is only acceptable for professional handling with protective gear and specific applications, like hull manufacturing, bodyshop/fairing or surfboard production but Not including speaker filling.

Thank you for the advice!

I have fiberglass insulation all over my attic, and I do need to go up there from time-to-time.

I had an extra roll sitting up there, which is where I grabbed it for my speakers. I modified the speakers so that they are sealed, though.

 

[Ktacos]

I used fibreglass in my last few builds, it ended up needing to come out and my word what a disaster that was. Never again.

 

[RickS]

Thank you for the advice!

I have fiberglass insulation all over my attic, and I do need to go up there from time-to-time.

I had an extra roll sitting up there, which is where I grabbed it for my speakers. I modified the speakers so that they are sealed, though.

I have encountered fiberglass in attics too and have had to work around it. Any clothes that contact need to be thrown out to keep the fibers from getting into other places and causing health problems. As @Morpheus indicated, it is a step up from asbestos, but not much in my opinion. It is a health hazard.

I have bought speakers with fiberglass damping and always replace it.

 

[RickS]

Here is an early look at a spin of the new single slot cabinet...

This is using minidsp 2x4 HD but avoiding filters with gain except for the very top end where it is needed as the DXT rolls off sharply. There are some further opps for improvement around the 1500 Hz crossover and around 600 Hz. I have started to experiment with the cabinet damping as well. I have narrowed the slot and removed some damping. Neither caused major changes in the directivity. This look is before I run the midwoofer spin so I hacked the crossover and is likely why the directivity is off slightly there.

 

[Fledermaus]

Nice DI curve...
BTW the spl range in that heatmap is quite wide - you might like to narrow it down a bit, since there's hardly any information below "green" (I'm using smth like 50-90 FWIW).
Did you measure some 2- or 3-slot variant ? IME, the 2-slot sim is nicer than 1-slot - haven't measured any yet.

More generally, would you mind sharing some of the things you learned about correlation, or lack thereof, between sim and measurements?
IOW, what makes sim predictive or not, and what did you find discrepancies, if any, to originate from ?
(Asking for a friend )