In this arrangement, or the blade, or the LS60 for that matter are the 4 woofers all producing the same FR? I snagged 4 woofers as part of a Black Friday deal and I'm trying to work through a design that will incorporate a maop 5. My thought is, and this might be dumb, that's why I'm asking, but if the top pair were used to make it a 2 way. Say you cross between 200-500 somewhere and you get that to work. Could you then run the bottom pair with a low pass filter somewhere around the point where the top pair start to roll off and run out of steam which would essentially be pushing the F6/F10 point to lower frequency?
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The max upper frequency in a push push that is slot loaded will be the 1/4 wave cancellation frequency - based on chamber/slot depth. For a 7in depth that is 470Hz. If you use a slot depth that coincides with where you place your low pass filter, you will get a nice steep 4th order filter for price of a 2nd order electrical.
On a push push like a Blade it’s open air so there is no upper limit in the cabinet to help you get a steeper filter. But what you get is a bipole design and it eliminates baffle step loss. So you get a boost in bass output that way.
On a push push like a Blade it’s open air so there is no upper limit in the cabinet to help you get a steeper filter. But what you get is a bipole design and it eliminates baffle step loss. So you get a boost in bass output that way.
Yes. I see no reason for that to not be the case. Part of the concept is the symmetry of the mounting of the bass drivers, and to maintain that symmetry one has to input the same signal and get the same physical reaction to that signal. In the MA we have fairly. convential woofers with the fronts connected together to maintain tight conectin (somethoign a DIYer might do with readty rod), in the KEFs they jump thru hoops to get one voice coil inside the other and stil maintain the same performance of each woofer in a woofer pair.
dave
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X beat me to the Frequency response limitations of the upper end of the response due to the cavcity they are firing into. The KEF firing into free air is limited only by the off-axis performance of the woofers, giving more flexibility in XO frequenmcy.
X has real world experience with these cavity resonances in his variation on the Pass slot-load OB bass (not something he invented but certainly popularized).
dave
PS: using a resonance to steepen the curve will have consequences, likely not beneficial. I’d want that reson ce well out of the passband.
X has real world experience with these cavity resonances in his variation on the Pass slot-load OB bass (not something he invented but certainly popularized).
dave
PS: using a resonance to steepen the curve will have consequences, likely not beneficial. I’d want that reson ce well out of the passband.
Thank you both @planet10 and @xrk971 I think I made have stated my design objectives incorrectly. My apologies. I'll be more direct. Is this a bad idea? I'm not asking anyone to run sims for me. Just responding to the concept.
MAOP 5 in two liter sealed box - PLXO or inline cap to to get 1st order XO around 300hz
Dual opposed LDW7 in 22L sealed box- PLXO or inductor to blend at the XO frequency
Dual opposed LDW7 in 22L sealed box- PLXO or inductor to blend at the F1 point of the other dual opposed woofers.
In a perfect world the 4 could be built into a circuit that allows them to run off of one amp but two amps would be fine too. All crossovers first order.
MAOP 5 in two liter sealed box - PLXO or inline cap to to get 1st order XO around 300hz
Dual opposed LDW7 in 22L sealed box- PLXO or inductor to blend at the XO frequency
Dual opposed LDW7 in 22L sealed box- PLXO or inductor to blend at the F1 point of the other dual opposed woofers.
In a perfect world the 4 could be built into a circuit that allows them to run off of one amp but two amps would be fine too. All crossovers first order.
Has anyone simulated a PPSL? Is it pretty well understood that there is no real benefit to directivity do to the slot? I read some writing by other people claiming that the PPSL configuration somehow shoots a wave at the listener.... ironically, it does do that. along with every other speaker in the world but, some seemed to believe something unique happens due to the slot, in regards of directivity, to which, I would only assume the directivity would perform as expected due to dimensions and wall angles....the normal ideas of waveguiding should apply here, and nothing to write home about regarding the interactions of the 2 woofers in the slot, that would increase LF directivity.
Yes, I have modeled these before in Akabak and the slot loading does give a boost. It’s different than open face driver because the air exits as a jet from the slot.
Could you please share your results!? In the parts of the spectrum that should be omnidirectional to the dimensions of the slot, why does it care about the pressure waves exiting from a slot? Outside of the additional reflections, it would be similar to a planar driver, and show no directivity to waves larger than the Terminus. Why all of a sudden are things changed?
I guess I am jumping the gun here... "boost" hasn't been defined yet..... Theres a boost in the upper range of the PPSL's I've seen, mine is near 150-200hz. This is due to the dimensions of the slot.
I guess I am jumping the gun here... "boost" hasn't been defined yet..... Theres a boost in the upper range of the PPSL's I've seen, mine is near 150-200hz. This is due to the dimensions of the slot.
A slot is just a low pass filter.
(On pressure waves, laminar flow and compression ratios)..
https://www.diyaudio.com/community/threads/gedlee-summa-vs-lambda-unity-horn.156988/post-2021840
I don't see this. If it did, don't you think you'd see nonlinearity over the course of a cycle?
(On pressure waves, laminar flow and compression ratios)..
https://www.diyaudio.com/community/threads/gedlee-summa-vs-lambda-unity-horn.156988/post-2021840
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The above simulation doesn’t account for actual fluid dynamics of jet exiting a plane. It’s a well studied and known hydrodynamic / fluids case.
For example, here is Schlieren image of a rectangular jet at M=0.18. There is directionality in near field of the fluid column. It’s not a simple 2D flat radiator at the wall.
For example, here is Schlieren image of a rectangular jet at M=0.18. There is directionality in near field of the fluid column. It’s not a simple 2D flat radiator at the wall.
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Static flow doesn't need to be taken into consideration in acoustic modelling.
https://www.diyaudio.com/community/...ectors-and-piston-drivers.194316/post-2666091
It’s an oscillating jet with penetration into the ambient fluid - the non-static component is a fluid column that is more than a pressure wave from a flat rectangular aperture. You seem to quote Gedlee a lot. Are we talking about the same thing here?
If such behaviour happens on the way out, what happens on the way back in due to the negative pressure? Sound has a net zero flow, after all. What of symmetry?
This happens to be a specialty of his.
You have reversing re-entrant flow of jet column that now makes a very complex flow that produces rectangular vortices at the boundary and this complicates the sound field quite a bit. The reversal doesn’t “undo” the penetrating jet.
I happened to do research and published a paper on a rectangular oscillating jet driven by a speaker membrane about 25 years ago (the paper was on the interaction of a vortex with a flat flame as imaged using planar laser induced fluorescence imaging). They produce vortex pairs (looks like a mushroom) and launch far out of the aperture. The reverse motion of the flow doesn’t negate the directionally launched vortex pair.
I happened to do research and published a paper on a rectangular oscillating jet driven by a speaker membrane about 25 years ago (the paper was on the interaction of a vortex with a flat flame as imaged using planar laser induced fluorescence imaging). They produce vortex pairs (looks like a mushroom) and launch far out of the aperture. The reverse motion of the flow doesn’t negate the directionally launched vortex pair.
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You showed effects at M=0.18 We generally shy away from anything near M=0.05 in reflex ports since they have problems at high velocities..
That was convenient case I found online to show a rectangular jet. Even at lower velocities typical of what we use it for to produce higher SPL bass, we are in the 10m/s (M=0.03) - which is definitely the same as the velocity range I did my research on.
I don’t have a planar laser imaging setup in my lab anymore 🙂 but I am assembling my new set of SLOB woofers today. I should have it working soon and will make some polar measurements to see what the directionality looks like in practice. This is a dipole with U shaped wings. I think the pattern might be different than a plane wall jet.
I don’t have a planar laser imaging setup in my lab anymore 🙂 but I am assembling my new set of SLOB woofers today. I should have it working soon and will make some polar measurements to see what the directionality looks like in practice. This is a dipole with U shaped wings. I think the pattern might be different than a plane wall jet.
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