Yes, the grill fits perfectly due to the bigger size of T34B. The hole is about 40,5mm and that is exact the size of the grill. No need for modification. I only added 4 holes for the seas tweeter.
Edit: The phase shield is removed from the seas!
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I wish a passive cardioid setup would be easier to design, but in reality and practicality DSP is the easiest way to go.. However.... being the type of diehard analog lover I am, there is a neat way to do the lowest 2 octaves (say from 30 - 120 hz) using DSP for feeding/powering the rear facing driver exclusivly by means of high quality class D plate amps. The front radiating stuff is run directly fed from the untouched analog signal path powered by your "typical" class A/AB amps.
I'm contemplating this strategy on the quasi-cardiod subs (2 x SB34NRXL75-8 front, 1 x SB34NRX75-6 rear) planned for underneath my large FLH midbass setup (100 - 500 hz). Abruptly losing the directivity below the midbass horns transitioning to conventional direct radiating subs makes the bass sound detached, less punchy and homogeneous. By having some control over the back radiated low end will fix this, as I discovered how good a larger point source PA setup can sound over a wider listening area using cardioid subs. You dont know how many people came up to me, stating some of my subs were "facing the wrong way" LOL. The first experience with cardioid subs was a game changer for me. I honestly will never go back to using standard subwoofer arrangements again.
I'm contemplating this strategy on the quasi-cardiod subs (2 x SB34NRXL75-8 front, 1 x SB34NRX75-6 rear) planned for underneath my large FLH midbass setup (100 - 500 hz). Abruptly losing the directivity below the midbass horns transitioning to conventional direct radiating subs makes the bass sound detached, less punchy and homogeneous. By having some control over the back radiated low end will fix this, as I discovered how good a larger point source PA setup can sound over a wider listening area using cardioid subs. You dont know how many people came up to me, stating some of my subs were "facing the wrong way" LOL. The first experience with cardioid subs was a game changer for me. I honestly will never go back to using standard subwoofer arrangements again.
How does acoustic resistance fit with smaller boxes? I'm intrigued by the concept and have a spare pair of 5" Satori woofers. I'm guessing a smaller (less wide) box isn't an problem for the woofer per se, but how would one match directivity to the tweeter? I'd rather not use a WG larger than the woofer and a 5in waveguide would seem to match most cardioid designs around 3kHz, but that would increase lobing and other problems, no? Would the concept make more sense with a less cardioid woofer? I'm not super experienced in this stuff so this might be a fools errand, but I don't mind wasting my time
Hi, It fits nicely smaller boxes, in fact passive cardioid (or leaky box) allows minimal boxes and removes problems of boxes altogether, trade-off is bass cancels out. Cardioid "action" is from bafflestep down for few octaves. Actually the pattern can be extended to very low frequency but the system loses lows 6db per octave with the cardioid action, so it just limits SPL for the system if trying to stretch it too far, to bass. Basically you are looking at three way system, with that 5" driver as cardioid mid. You could implement tweeter like with any project, response of the woofer above bafflestep is practically same as with closed box. You could put the 5" speaker into 5" x 5" baffle, have ebough depth to fit it in and use freestanding waveguide on top for tweeter. King of boxes, almost no box at all. Open baffle performs about similar and is even less box and pattern is different. OB is much easier to build and tune, it needs to be positioned out in the room though, while cardiod can be closer to wall.
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Huh, that makes sense. I had no idea about the baffle step relevance here. I was thinking of going cardioid only down to 200Hz or so as there seems to be conflicting opinions on the benefits below Schroeder freq and losing SPL on small drivers is a bit of bad recipe, though I do listen at very low levels. I'm filling the very low end with a multi-sub approach, FWIW. Freestanding WG could be nice but not enough WAF for me 
You can check it out in VituixCAD diffraction tool, kinda, just use the ideal driver (don't load any response) and tick "open baffle". Passive cardioid loses the low end similarly as open baffle so we use the open baffle as analog here. You'll see that enlarging the baffle the response stays the same only moves down in frequency. There is the "main diffraction hump" which relates to baffle size and below that smooth rolloff. Above is not very usable due to diffraction so basically baffle size defines the upper end of usable bandwidth and the low end is defined how much bass you can lose. This is why you want to use as big driver as possible, or conversely as small baffle as possible and choose woofer size that can be crossed over to a tweeter.
If you want to have cardioid down to 200Hz you could calculate up from there. Two octaves would be 800Hz but its too low for most tweeters, three octaves would be 1600Hz. Your tweeter defines where the crossover could be so, if it is the 1600Hz then use beefiest woofer below that in order to withstand 3 octaves dropping response. I'm guite sure 8" driver is more suitable than 5", the bigger the better but direct radiating tweeter or small size requirement limits. Its quite easy to build and experiment with, fun time so I encourage try your 5" and see what the system does
Here is example, ideal 8" driver on minimal 20cm x 20cm baffle, open baffle. You see the power response tops out bit above 1kHz and is downhill from there down, around 200Hz its about 12db down from the peak. If your woofer was rated 92db/1W/1m sensitive, after equalizing the response straight from 200Hz up you'd probably looking system with 80db/1W/1m sensitivity. You'd of course lose some on baffle step usually so not great loss, but something that limits the system sooner or later. You could use two in MTM configuration if you wanted more sensitive system.
Although I've played with this kind of boxes some I haven't bumped into configuration that had cardioidish pattern up top and then would fall back to omni around the 200Hz or so, not sure if that was possible. It is certainly possible to have all kinds of variations on the pattern, why I like to call it cardioidish, but it seems the power response would just drop like that regardless, perhaps about 10db down after few octaves of usable cardioidish response.
Above stuff is based on my experiments, most of which are written on this very thread about year ago. Speaker on the thread title has quite good response, it would be hard to surpass the performance with any other driver / size / construct I think. Its pretty well tuned system for what it is. You could use bigger waveguide and bigger woofer for similar response, but not smaller. If you want similar response you should copy it to the teeth.
If you want to have cardioid down to 200Hz you could calculate up from there. Two octaves would be 800Hz but its too low for most tweeters, three octaves would be 1600Hz. Your tweeter defines where the crossover could be so, if it is the 1600Hz then use beefiest woofer below that in order to withstand 3 octaves dropping response. I'm guite sure 8" driver is more suitable than 5", the bigger the better but direct radiating tweeter or small size requirement limits. Its quite easy to build and experiment with, fun time so I encourage try your 5" and see what the system does
Here is example, ideal 8" driver on minimal 20cm x 20cm baffle, open baffle. You see the power response tops out bit above 1kHz and is downhill from there down, around 200Hz its about 12db down from the peak. If your woofer was rated 92db/1W/1m sensitive, after equalizing the response straight from 200Hz up you'd probably looking system with 80db/1W/1m sensitivity. You'd of course lose some on baffle step usually so not great loss, but something that limits the system sooner or later. You could use two in MTM configuration if you wanted more sensitive system.
Although I've played with this kind of boxes some I haven't bumped into configuration that had cardioidish pattern up top and then would fall back to omni around the 200Hz or so, not sure if that was possible. It is certainly possible to have all kinds of variations on the pattern, why I like to call it cardioidish, but it seems the power response would just drop like that regardless, perhaps about 10db down after few octaves of usable cardioidish response.
Above stuff is based on my experiments, most of which are written on this very thread about year ago. Speaker on the thread title has quite good response, it would be hard to surpass the performance with any other driver / size / construct I think. Its pretty well tuned system for what it is. You could use bigger waveguide and bigger woofer for similar response, but not smaller. If you want similar response you should copy it to the teeth.
Now that I'm being eagerly spoonfed I might as well ask: since the SPL loss is a particular concern for small speakers, would it make more sense to go for active cardioid (delayed woofer in the rear) rather than passive? On the other hand, there'd be only about 5dB of open baffle loss at 200Hz - an MTM would give more of a benefit in SPL (if I'm not mistaken), and way more benefit below 200Hz if I manage to limit the cardioid action there. In my case it would have to be a TMM though, so perhaps a 2.5-way.
Having a rear woofer that is delayed only above 200Hz so that it worked as a force-canceling woofer in lower bass would be interesting but not that realistic, I guess
Having a rear woofer that is delayed only above 200Hz so that it worked as a force-canceling woofer in lower bass would be interesting but not that realistic, I guess
Yeah it gives a lot more control on the pattern if you actively manage the sound on the back. Look for posts by nc535, not remember which threads, but he posted some VituixCAD sims of active cardioid last year I think. You can do it too with VituixCAD, its not very complicated. ideal drivers with diffraction tool generated measurement sets, tweak them as if they were measurements of a real speaker you have in your mind. Then build and test if you get to a system with satisfactory results. MTM would give more system sensitivity, also if you mitigate edge diffraction you can just enlarge the baffle which by itself makes cardioidish response, "shadows" high frequencies to back.
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Whether the cancellation that causes the increase in directivity is active or passive, the SPL is limited through the cancellation region in the same way. Using an active driver does give the possibility to shape the cancellation to a specific frequency range and use the active driver below that range without limiting it's SPL.
This will in most cases create a step in the directivity where there is a rapid loss of directivity to keep the SPL up, I am less and less convinced that this is a good trade.
Wait, what do you mean by "in the same way"? A woofer canceling in the rear has (hopefully) no effect on the listening window, whereas an open baffle (or a resistance enclosure) directly reduces the SPL as mentioned. What am I missing?
It does. The physics do not care if the air displacement at the rear comes from a slot or a second (rear) woofer. Maybe the following idea helps:
Cardioid = 1/2 monopole + 1/2 dipole
Making the dipole term requires lots of air to be moved around [assuming wide band operation], which has to pass 'through' the (front) woofer. Most of the woofers displacement is spent on creating this term. Therefore the principle that reduces SPL for a dipole, also applies to a cardioid, given a (front) woofer with a certain volume displacement.
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Damn, I still don't get it. Let's ask this way: if I simulate an active cardioid in VituixCAD (similar to HammerSandwich on ASR), where's the effect on the listening window response?
Indeed, but in cardioid sims the rear is cancelled. I guess my problem then is the open baffle sims which don't account for the "boost" provided by rear radiation?
The directivity is created through acoustic cancellation, a source from the side interfering with the source from the front. It does not matter whether that is a resistance vent or an active driver. There is a loss in SPL output from the cancellation. A dipole and cardioid have the same DI 4.8dB but the patterns are different. The loss is not just to the rear, a true cardioid has the most loss there but there are other cardioid variations where the cancellations occur at different places, while maintaining an overall similar DI.
I don't really understand what you mean about the listening window to help you with whatever it is you are missing
For example: compared to "normal" baffle, an open baffle in my case has around 8dB of reduction at 100Hz directly in front of the speaker. Using a rear woofer for the cancellation, there is no such loss. Even if we compare against two woofers in an open baffle, the setup loses by 2dBI don't really understand what you mean about the listening window to help you with whatever it is you are missing
I think my example confused you somehow. The open baffle setup has no spacing (right?) so it won't be identical
An idealized open baffle doesn't have a loss straight ahead. There is an overall loss of about 8dB at 100Hz from the dipole peak which needs to be equalized.
An active cardioid gives more freedom to choose the lowpass and delay and in this example there is still 10dB difference between front and rear at about 100Hz.
This is the same driver without the processing and active side woofers, the baffle size gives some cardioid like response to 300Hz
What do you mean by "idealized"? I'm just getting more confused here. If you use the diffraction tool and untick "open baffle", there's an increase in the bass response straight ahead. How is there then no loss in the OB straight ahead?