It occurred to me that I could also add passive radiators to help with the low end. Adding for example two SB12PFCR-00s with some extra mass would give me an extra 10dB at 40Hz, according to WinISD. I don't need the extra SPL, but side-mounted PRs would reduce vibration on the cabinet and relieve the Kartesian from some excursion.
On the other hand, even if we give my initial spec of 70dB@1m a bit of headroom and go for 75dB, the single Kartesian still only reaches 2.3mm of excursion while the Kartesian with PRs would do 0.8mm (with PRs reaching 1.3mm). Since the Kartesian drivers presumably play clean at even triple this excursion, would the PRs "smear" the sound for no benefit other than a bit of vibration reduction and slightly improved efficiency?
Attached is a rough idea of the enclosure I'm going after, with an xrk-inspired 5-sided dagger I'm thinking of 3D printing for the NE65W.
On the other hand, even if we give my initial spec of 70dB@1m a bit of headroom and go for 75dB, the single Kartesian still only reaches 2.3mm of excursion while the Kartesian with PRs would do 0.8mm (with PRs reaching 1.3mm). Since the Kartesian drivers presumably play clean at even triple this excursion, would the PRs "smear" the sound for no benefit other than a bit of vibration reduction and slightly improved efficiency?
Attached is a rough idea of the enclosure I'm going after, with an xrk-inspired 5-sided dagger I'm thinking of 3D printing for the NE65W.
Attachments
PRs get a thumbs-up from me in this application. Easily-adjusted tuning (compared to a ported box) gives you some flexibility - if you find you're barely tickling the drivers and fancy more LF extension, you could add some mass to the PR and EQ the result. So long as you're boosting at/above the PR tuning frequency, all is well.
Chris
Chris
Speaking of flexibility, I guess I could always add the PRs afterwards if I find the bass output lacking. Shouldn't be a problem routing the holes even on an assembled enclosure 🤔
you do nit get the active reaction force cancelation. They will actually weaken the structure as you are adding 2 big holes on the sides.
dave
The cancellation is not as complete as with opposed active drivers, but considering that the PRs would have in total ~8 times the Mms of the Kartesian and they excurse 60% more, surely they would bring most of the benefit? Or am I missing something?
I do need to add bracing if I go with the PRs, that's for sure
I do need to add bracing if I go with the PRs, that's for sure
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The P in PR stands for passive. You will get little to no benefit cabinet vibration wise, the same amount of energy from the active driver is being pumped intot he box. The holes will change the resonance structure but they will not reduce vibrations like ACTIVE push-push does.
dave
dave
I don't understand. Isn't there (practically) the same amount of energy pumped into the box with an active push-push, the forces just end up canceling each other? Similarly, since most of the forces in my example come from the opposing PRs, why would there not be a significant benefit?
In an active push-push the energy that would normally go into the box is canceled before it gets there.
You seem to be under the impression that air space energy is a significant contributor to box resonance. The important energy comes from the driver being attached to the structure and goes thru the structure.
dave
You seem to be under the impression that air space energy is a significant contributor to box resonance. The important energy comes from the driver being attached to the structure and goes thru the structure.
dave
I'm not thinking the air is doing anything here. Of course the energy is transmitted through the structure, which is why I don't understand how the energy could get canceled in a push-push before getting to the box. Or why it would be different from opposed PRs 🤔
A push-push has actice reaction frorce cancelation. The reactive force of one driver is (almost) exactly canceled by the reactive force of the other which (mechanically) equal but opposite. On a micro level it is canceled, at a macro level it is just not there.
With a single driver on the back all of the energy is pumped into the box.
dave
With a single driver on the back all of the energy is pumped into the box.
dave
I am talking about having two PRs, mounted on opposing side walls - not a single PR on the back. Maybe this is where the confusion lies?
Not to hijack the thread, but a question for Chris 661: what did you think of the equalized KEF eggs? The eggs are regularly offered for 10-15 Euro a piece over here in NL, hence my asking.
What confusion? A PR is passive. Doesn’t much matter where they are they will not reduce energy injected into the loudspeaker enclosure.
dave
You mentioned "a single driver on the back", when I'm talking about two opposed drivers on the sides (and the active driver in front). Seems confusing to me 🙂
An active push-push doesn't really reduce energy either, no? There's no vibration due to the opposing forces, but the energy is there. The forces create a sort of compression instead of momentum. In my suggestion nothing is canceling the front driver, yes, but since the PRs reduce the front driver's excursion and the PRs cancel each other, the total vibration is reduced. If you still argue that it is not reduced "because PRs are passive", I guess there is no point continuing on this
E: Also take a look at this build, where the same concept is used. Or is he wrong? https://hificompass.com/en/projects/2-way-systems/puri-bliss-bewg
An active push-push doesn't really reduce energy either, no? There's no vibration due to the opposing forces, but the energy is there. The forces create a sort of compression instead of momentum. In my suggestion nothing is canceling the front driver, yes, but since the PRs reduce the front driver's excursion and the PRs cancel each other, the total vibration is reduced. If you still argue that it is not reduced "because PRs are passive", I guess there is no point continuing on this
E: Also take a look at this build, where the same concept is used. Or is he wrong? https://hificompass.com/en/projects/2-way-systems/puri-bliss-bewg
Built these guys a month back but haven't been able to play around much, as I had to return my Thomann 4x4 Mini Amp due to a dead channel.
I now received a new unit and slapped on a Harsch XO around 300Hz after some quick driver measurements. Chamfering the baffle seemed to make the NE65W a LOT smoother, though I had a few days between the comparison. With some mild MMM based PEQ, I'm very happy. H2 dominated THD stays under 0.5% above 400Hz (1% at 300Hz) or so at 80dB/1m - not spectacular per se, but more than decent considering the fairly smooth off-axis and size of the driver.
The Sub120 is even better. The detail and extension in bass quite blew me away - better than on headphones, though I'm no trained listener. Distortion seems to match manufacturer measurements well. With a fair amount of room gain in my concrete apartment, they have no problem doing 80dB@30Hz with THD below 5% (though H3 dominated). Thanks for the suggestion @chris661 ! Vibration hasn't been a problem with rubber feet underneath - it's just noticeable at max excursion.
Still need to tidy up the enclosures and do some proper measurements.
I now received a new unit and slapped on a Harsch XO around 300Hz after some quick driver measurements. Chamfering the baffle seemed to make the NE65W a LOT smoother, though I had a few days between the comparison. With some mild MMM based PEQ, I'm very happy. H2 dominated THD stays under 0.5% above 400Hz (1% at 300Hz) or so at 80dB/1m - not spectacular per se, but more than decent considering the fairly smooth off-axis and size of the driver.
The Sub120 is even better. The detail and extension in bass quite blew me away - better than on headphones, though I'm no trained listener. Distortion seems to match manufacturer measurements well. With a fair amount of room gain in my concrete apartment, they have no problem doing 80dB@30Hz with THD below 5% (though H3 dominated). Thanks for the suggestion @chris661 ! Vibration hasn't been a problem with rubber feet underneath - it's just noticeable at max excursion.
Still need to tidy up the enclosures and do some proper measurements.
Old post but this caught my eye. Dave, When the item in the hole is mounted properly, it should become part of that structure. In this case, a PR. The basket of the PR or drivers are supposed to be resonance free in the driver's working range. Can you not take advantage of this presence and use it to engineer in further stiffness to the panel?
Where are you with your project now? Do you have any results?
Regarding the enclosure, how are you addressing the ply edge on the lower square part of the baffle?
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That makes sense about the PR becoming part of the structure (assuming screws make the joint completely rigid), and adding a ring of material under the flush-mounted basket of the PR would further stiffen things.
I'm still considering adding PRs, but as I'm currently getting response down to 30Hz in-room, it seems difficult to find PRs that would extend the response low enough. A single PTT4.0PR seems like the only choice, but for similar cost I could just get another Sub120 and have proper force-canceling etc.
Not sure what you mean with the ply edge. I've only lazily painted the enclosures dark grey while working on a 3D printed enclosure (pic). I also wanna try a smaller BMR driver instead of the NE65W - just to make things slightly more compact 🙂
I'm still considering adding PRs, but as I'm currently getting response down to 30Hz in-room, it seems difficult to find PRs that would extend the response low enough. A single PTT4.0PR seems like the only choice, but for similar cost I could just get another Sub120 and have proper force-canceling etc.
Not sure what you mean with the ply edge. I've only lazily painted the enclosures dark grey while working on a 3D printed enclosure (pic). I also wanna try a smaller BMR driver instead of the NE65W - just to make things slightly more compact 🙂
With all the cancellation and the mention of a second driver, have you considered isobaric?
I do wood carving and such. The raw ply edges on your baffle, especially at the square bottom area are calling for some sanding and softening of the hard edges to create a unique contour look under clear finish
I do wood carving and such. The raw ply edges on your baffle, especially at the square bottom area are calling for some sanding and softening of the hard edges to create a unique contour look under clear finish
Right, the edges show up a bit through the layers of paint I have now (which is nice) but the brushstrokes I left are way stronger so it's not such a significant detail 😀
I think isobaric would only make sense if I had an undersized enclosure (and people say it's not the best compromise even then), but it currently has around 3 times the required volume.
I think isobaric would only make sense if I had an undersized enclosure (and people say it's not the best compromise even then), but it currently has around 3 times the required volume.