Fun with the new ND Passive's - The Passive Aggressives

[mattp]

Named for their aggression/size ratio. This is a little project I came up with using our 0.04 cube knock downs and some leftover red oak veneer. Each cabinet uses an ND91-4, two dual opposed ND90 passives and an ND20FB-4. These are some kick @$$ desktop speakers that really don't need a sub. They even hit you a little in the chest with certain kick drums. Very impressive for the footprint they have.

The tricky part was getting everything to fit in the cabinet. I had to slightly offset the passives so the threaded rods wouldn't hit each other under extreme excursions. Dremeling them shorter is another option but I didn't bother. The passives use all of the included weight but I did remove the wing nuts. Tuning according to DATS is around 56 Hz which is about where they modeled. Fairly simple crossover, the ND91's are a little tricky when you are shooting for a minimalist design. XO is around 2.6kHz. Enjoy the forthcoming eye candy.




(Knife for scale)

[mattp]

Electronical shenanigans.

Simulated response:



Measured response:



Measured impedance:

[howard]

Very attractive! I would like to hear them.

[KEtheredge87]

Lookin' good sir! Do you think we might hear these at any upcoming DIY events, like InDIYana or MWAF in July?

I'm really excited to see more projects like this that utilize the new passives. I myself would like to build some small towers for my living room using the ND series, but I can't quite reconcile my feelings on the mounting flange (personally not a fan of the shape) vs. doing a rear mount with chamfer or otherwise on the front. I know the rear mount + chamfer look is troublesome from an acoustics perspective, but it looks sleek, and having the cabinets look great is also a general requirement to satisfy high WAF

[mattp]

Very attractive! I would like to hear them.

Thanks!

Lookin' good sir! Do you think we might hear these at any upcoming DIY events, like InDIYana or MWAF in July?

I'm really excited to see more projects like this that utilize the new passives. I myself would like to build some small towers for my living room using the ND series, but I can't quite reconcile my feelings on the mounting flange (personally not a fan of the shape) vs. doing a rear mount with chamfer or otherwise on the front. I know the rear mount + chamfer look is troublesome from an acoustics perspective, but it looks sleek, and having the cabinets look great is also a general requirement to satisfy high WAF

I will try to have them on display at MWAF and see if the guys can bring them to InDIYana with them to demo. We are hoping to sell these as a kit.

I agree about the pincushion frames. I would have liked to rear mount these but there was no way they would have fit, even just rear mounting the active woofer would've been impossible in order to fit everything in the cabinets. I encourage you to play with the ND series though. Very nice drivers for the money and the passives open up a ton of possibilities for tiny designs. Chris P did a quick model on these and determined that a 1.5" diameter port would have had to be 36" long to get the same tuning frequency.

[Kevin K.]

I like these little guys and I like #7 on the dry erase board too.

[ceiol]

Cool. Gotta build these and integrate the new BTmini plate amp!

edit: so I put the drivers and your XO into XSim. I just can't get the phase to align. Also my curve looks a bit different -- I have to change the R2 resistor from 3 Ohms to 8 Ohms to get my FR looking like yours.

I tried using 0, 0.2, 0.4, 0.6 etc for the offset for the ND91-4, but still it does not align the phase.

what am I doing wrong here?

[tomzarbo]

Very cool, Matt.

They look super... I think this has to be one of the rockin'est 'tiny' speakers out there at this point.
I can imagine that a 5.1 HT system with these and a suitable sub would really knock people's socks off.

It's hard to tell from the pic, but what amp were you using? It kind of looks like it might be hooked up to the new DTA-2.1BT amp? How did that combo perform? I'm borrowing Kevin K's amp hooked to the Bantam speakers using the same driver, and it does have the guts to drive them plenty loud. I've found that the ND91's seem to like a fair amount of power to reach their full output potential.... seems strange for their size, but they just keep getting louder and louder without really complaining.

I'd also love to hear these at the MWAF if possible.

This is exciting stuff if you ask me, I love seeing PR's in motion.

TomZ

[Wolf]

I have 4 of the nd90pr myself for some upcoming fun..

Looks cool, Matt!

Later,
Wolf

[mattp]

Cool. Gotta build these and integrate the new BTmini plate amp!

edit: so I put the drivers and your XO into XSim. I just can't get the phase to align. Also my curve looks a bit different -- I have to change the R2 resistor from 3 Ohms to 8 Ohms to get my FR looking like yours.

I tried using 0, 0.2, 0.4, 0.6 etc for the offset for the ND91-4, but still it does not align the phase.

what am I doing wrong here?

I used my own in-box measurements for my XO design. Phase still isn't perfect but that would explain why you are getting a different curve with your sims.

Very cool, Matt.

They look super... I think this has to be one of the rockin'est 'tiny' speakers out there at this point.
I can imagine that a 5.1 HT system with these and a suitable sub would really knock people's socks off.

It's hard to tell from the pic, but what amp were you using? It kind of looks like it might be hooked up to the new DTA-2.1BT amp? How did that combo perform? I'm borrowing Kevin K's amp hooked to the Bantam speakers using the same driver, and it does have the guts to drive them plenty loud. I've found that the ND91's seem to like a fair amount of power to reach their full output potential.... seems strange for their size, but they just keep getting louder and louder without really complaining.

I'd also love to hear these at the MWAF if possible.

This is exciting stuff if you ask me, I love seeing PR's in motion.

TomZ

Yes Tom that is a DTA2.1, just what we had sitting in that little area in the office. It works well. These will take some power and not complain, I ran them for a while in the lab on an A500 and they didn't miss a beat. I will have them running on an LP1601S at home but I probably won't have them up very loud. Who knows, beer knows no bounds.

These will be on display at MWAF for your audible pleasures.

With tiny dual opposed passives it's especially funny, you can see them both moving if you are looking right at the speaker. The whole thing comes alive...

Thanks for the comments guys!

[Mike Burke]

Looks like my next project.

Looking at the schematic....C2 48UF is that right ? or is it a 4.8UF ?
I hate to ask but I'm going to anyway
Do you have a bill of matterials with part #s

Thanks,
Mike

[mattp]

Looks like my next project.

Looking at the schematic....C2 48UF is that right ? or is it a 4.8UF ?
I hate to ask but I'm going to anyway
Do you have a bill of matterials with part #s

Thanks,
Mike

Mike,

Yes that is indeed 48uF. I used electrolytics for everything just to save space. I also used 5W wire wound resistors for the woofer zobel because it is smaller. There is a 50uF in place of the 48uF in the list because we don't have a 48uF that is small. You can parallel two other values together if you want (this is what I ended up doing) but this 2uF difference will amount to nothing in the long run. Also...the woofer and tweeter need to be wired in positive polarity, unlike what the schematic shows. I forgot to fix this when I uploaded the pic.

Parts list:

Two of each of these:

027-420
027-406
027-354
015-3
004-9.1
257-022
257-036
290-224
275-035
091-1245

Four 290-209

One 300-7060

Driver spacing - Everything is centered on the baffle, the tweeter is 1.5" down from the top and the woofer is 2.5" up from the bottom. The passives are centered on the sides but I would recommend offsetting these each by about 1/8" up and down (one passive a little higher, the other a little lower) unless you want to just cut the excess threaded rod off the back.

I mounted my crossover on the bottom but it will also fit on the back if you make it small enough. Be careful that nothing is in the way of the passives such as wiring. I'm making all this sound a lot more complicated than it really is. If you have any specific questions let me know.

[Mike Burke]

Thanks Matt for posting all the details. Great information..Thanks

" Also...the woofer and tweeter need to be wired in positive polarity"

Does that mean the the positive from the woofer goes to the positive of the tweeter ?

[mattp]

Thanks Matt for posting all the details. Great information..Thanks

" Also...the woofer and tweeter need to be wired in positive polarity"

Does that mean the the positive from the woofer goes to the positive of the tweeter ?

No, instead of the tweeter polarity being reversed as the schematic shows, it just needs to be wired normally.

[Mike Burke]

Oh Yea....I see that now.

Got it

Thanks for the help