Why on earth would you say something like that? 😕 No length-resonances, it doesn't increase losses (much better than long ports) or the enclosure volume, no mid-garbage, lower distortion, the active surface is much bigger. Look at all these mud-shovel subs with extremely high Mms, stiff suspension and deep tuning. A passive radiator is the best thing you can do with these. I'm not a fan of these subs at all but if the port becomes too long, that's the best thing you can do. The two downsides are they are more expensive than a port and they don't add cooling.
The problem with passive radiators is lack of control over them.
They work exactly like a port however a PR is many times heavier than the air column in an equivalent port bringing with it the associated problems that they are comparatively slow to start moving and worse slow to stop.
They work exactly like a port however a PR is many times heavier than the air column in an equivalent port bringing with it the associated problems that they are comparatively slow to start moving and worse slow to stop.
Did you sleep on a book 'unfounded prejudgements'? 😀 Compare the waterfall decay on a small enclosure, deep tuned reflex box and one with a passive radiator, you'll find both are delayed but stop at the same time or the PR in some cases even sooner because the drop off slope is steeper. On these long ports even the losses are usually lower with a PR. What you are talking about is the use of a PR in a inapplicable situation, if the Qts/Qt is too high or the tuning frequency is too high. The same was said about the bassreflex speakers in the 70s and 80s.
Nope, just Physics 101 and 30 odd years of hearing PR enclosures fail.
Like those Mackie monitors, which were flavour of the week until people started actually using them.
However I noticed that the relevant wiki page has been changed recently and now purports erroneously that the weight of a PR is equal to the weight of the air column in an equivalent port which is ludicrous.
Like those Mackie monitors, which were flavour of the week until people started actually using them.
However I noticed that the relevant wiki page has been changed recently and now purports erroneously that the weight of a PR is equal to the weight of the air column in an equivalent port which is ludicrous.
Physics say high air velocity is bad. PRs avoid that.
Well, that's 'semi-logical conclusion'. That's obviously wrong and easily to prove. At least in the most cases, there may be examples where that might be actually correct but these would not be a good use of a PR. The weight does not matter that much like you think it does, it doesn't have to make fast movements because of the low frequencies and above they quickly lose energy/excursion/spl, it comes down to the resonance frequency of the PR and I can understand why you came to the conclusion the PRs are 'slow' - in many cases it's used to get the maximum depth and 'because I can' doesn't mean, it's actually good. Yes, it's very tempting because 'deep, deep, DEEP!' but usually not a good idea because that gives a very high group delay. And a high GD translates to 'sluggish' bass. But that's the same with BR or BP. In most cases it sounds a LOT better with a less deep tuning and/or slow slope to compensate the roomgain but that often means, BR or PR isn't the best speaker principle.
It's about weight/motor ratio. Yes, PR need lower Qts drivers but that doesn't make it bad. You've been wrong about a lot other things before too. Believe what you want to but the physics doesn't change for you.
I made some simulations in WinISD, but my results are different like those suggested in BMS specs.
They suggested 44 liters cabinet with 120mm vent 434mm long tuned to 31Hz.
If i put that vent in WinISD my tuning is around 38Hz. To get 31Hz tuning i need 710mm long vent.
Why there is such a difference? Am i doing something wrong?
They suggested 44 liters cabinet with 120mm vent 434mm long tuned to 31Hz.
If i put that vent in WinISD my tuning is around 38Hz. To get 31Hz tuning i need 710mm long vent.
Why there is such a difference? Am i doing something wrong?
I didn't find any option for level of stuffing in Win ISD.
Any good alternative for box calculation?
Any good alternative for box calculation?
That is seemingly wrong but a lot closer to the praxis. For PA use, slot bottom or triangle corner ports are standard at that size subwoofers. If the port(s) are running along a wall, they are roughly 20% 'virtual' longer than calculated, along the edge and corner it can be up to 50%. Since the needed enclosure volume is given and the baffle size too (because of the size of the driver), you can only get so much variance of the enclosure that hardly anything else than corner or edge-slot ports can be realized. The tuning might be that low or a few Hz be above that, depending on how you build the enclosure and port. You can verify the tuning by measuring the impedance, the lowest point between the two peaks is the tuning f.
For your 3-way speaker with the port not being placed along a wall, that 44cm port might be too short but you can build and measure it, as a port you can use the super-cheap drain pipes and simply creep up to the desired tuning by cutting it off or put a 2nd tube onto it to extend it. At a 70cm long port its length resonance would probably fall into the used frequency range, it's probably not desireable to have a that long port.
The plan is to add a slot vent at the bottom of the enclosure so there will be one corner. I cant add round vent ( easy to try different leght) because of low space, only if i add them outside the box.
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