In this thread we can focus on the gimmicks of loudspeaker design. I see this thread as a place to point out potential Gimmicks of popular brands/models, to be dissected for the sake of clarity. There is only so much that can be done with modern loudspeaker design... I bet after a while the older ones of us have heard or seem it all. It is refreshing when something new comes along but it is disheartening when something is passed off as new, different, or legit when in actuality it is a load of BS. Maybe discussing these things can be a sort of therapy as we watch the world burn.
To start off, I present This..... I hypothesize diffraction from the skinny slots/groove in termination of the waveguide... desireable or even on purpose, unknown..... Laminar air flow? Skepticism draws near.... Reduces distortion? Why is there a distortion problem in the first place?
"an unusually complex flower-shaped waveguide to improve dispersion."
To start off, I present This..... I hypothesize diffraction from the skinny slots/groove in termination of the waveguide... desireable or even on purpose, unknown..... Laminar air flow? Skepticism draws near.... Reduces distortion? Why is there a distortion problem in the first place?
"an unusually complex flower-shaped waveguide to improve dispersion."
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Yes! Any sharp edge inside a port will increase chuffing noise.
I tried it and it was disastrous.
One can probably try to force air into laminar flow, but it creates lots of annoying higher pitched noise.
Oh, I thought this was about the first image, presumably a reflex port ... ?
ok I see what the laminar is focused on now.
Either way, we are still in the land of gimmick... I wonder what "technology" they are using to push the midrange waveguide.
Either way, we are still in the land of gimmick... I wonder what "technology" they are using to push the midrange waveguide.
People will believe anything if put in a graph or illustration
Making the illustration on the right black and white really sells the infomercial aesthetic
... even the misconception that a straight air jet at port output is desirable ...
I like your exchanged illustration ... it even took some time to realize it!
I mean its about as credible as the original... Laminar flow is had when the pressure gradient is equal across the the terminus. I regular BR at/near tuing has laminar flow already....Low enough pressure would introduce turbulence but the end of the day, this aspect inconsequential towards sound quality. I might be mistaken but the fins in this creations do nothing beneficial. If any thing there are some consequences of port noise at higher spl levels....
I've often wondered whether square-straw-like guides in a midrange waveguide would avoid long delayed reflections back and forth between walls (the Geddes' High Order Modes). Built kind of like multicell horns, but overall conical and with the cross-section of each path kept smaller by adding straws downstream as the guide expanded. Maybe could be made via 3d printing.
Being that HOMs don't appear to be practical to measure, it would probably be difficult to prove.
Being that HOMs don't appear to be practical to measure, it would probably be difficult to prove.
PMC's "LaminairX" slots at the end of the transmission line are not a "waveguide", they are there to increase the hydraulic diameter of the duct, lowering it's Reynolds number, increasing laminar flow potential, reducing air turbulence, which causes chuffing noise, which is a form of distortion.
The foam in the transmission line (tuned quarter wave pipe, TWQP) absorbs upper bass frequencies which may be out of phase with the woofer's direct output when exiting from the pipe. That "phase distortion" would cause peaks and dips in frequency response, and multiple time arrivals, "impulse response distortion".
The Helmholtz tuned absorber reduces unwanted positive low mid reinforcement (boom/mud).
The foam also increases the effective path length (effectively slowing the speed of sound), so a shorter pipe can reinforce a lower frequency than it would without.
Like JBL's "High definition Imaging" (HDI) waveguide, PMC's "n-compass" waveguide increases lower frequency loading while not restricting the higher frequency dispersion.
The "n-compass" waveguide provides more low frequency output from the 2" dome without requiring increased excursion (a potential source of HD and IMD), while also increasing upper output and widening the dispersion through relatively low diffraction "slots".
As usual, simple marketing names can't give a full description of technological features, but none of PMC's features are "gimmicks", they are all implementations of proven, acoustically valid concepts.
Those concepts are very "legit" imate.
Art
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Reducing the cross-sectional area increases the average velocity and increases the duct Reynold's number. Introducing a significant amount of extra surface area increases the drag opposing the flow in and out of the duct/port. Flow is always laminar next to a wall which would indeed increase the proportion of the air flow that is laminar if the velocity away from the wall hadn't also been increased by the reduction in cross-sectional area which will decrease the thickness of a laminar sublayer. The changed shape will also have an effect. Increasing the friction of the port may not be desirable depending on how the port/line is tuned. PMCs port/lines are often not conventionally tuned and tend not to perform that well by conventional standards.
Assessing if the pros outweigh the cons in a technical sense would require study and presenting it would almost certainly detract from the value added for the kinds of people that tend to be potential PMC customers. Even if there was a slight advantage rather than a slight disadvantage the fact it is tiny would make it a poor feature in a technical/engineering sense due to the added complexity and expense. On the other hand, without quantitative technical information and with a technical-sounding story that appears reasonable to nontechnical people features like this can add significant value to a speaker for many.
It's not just boutique speaker manufacturers like PMC that include features on their speakers to serve marketing purposes rather than engineering ones. KEF for example are currently doing it with their metametrial to absorb the rear radiation from a tweeter. There is no engineering reason to do this compared to using a small cheaper bit of fluff but there is a marketing one in distinguishing their speakers from their competitors with something that adds value for many in being more advanced.
So I wouldn't necessarily label features that have a weak-to-no engineering case gimmicks. There may be a signficant marketing case. A few decades back their was a period when speaker manufacturers almost all started including bi-wiring terminals as a feature. There was little-to-no engineering case to do it but if a speaker manufacture opted not to they ran the risk of losing significant sales to their competitors because many customers valued the feature.
There are two ways to not have laminar flow, too low or too high of a particle velocity. To low can create pressure differentials, as well as too high. @andy19191 is this right? Either way, there is nothing wrong with vents that are designed large enough to avoid high particle velocity or with rounded surfaces... its a gimmick to me, if it does something not needed or should I say, it does something that gives no practical gains over what's already been done.
": a trick or device used to attract business or attention
a marketing gimmick"
If the only reasons something is done, is in order to make a sales bullet... thats a gimmick.
": a trick or device used to attract business or attention
a marketing gimmick"
Not sure I understand. Smooth laminar flow occurs when viscous forces dominate inertia forces. Viscous forces are a product of viscosity and spatial velocity gradients and inertia a product of mass and temporal velocity gradients. Particle velocity is usually the part of the velocity associated with sound (air movement to compress and expand) but in the case of a port/line the largest part of the velocity is likely to be associated with a slug of air moving in and out without compressing.
Technical performance is one way to assess the value of speakers but it isn't the only way. For luxury goods like expensive domestic speakers it is likely to be a fairly small part of the value for most owners. Indeed a fair few "subjective" audiophiles may consider technical performance to be of zero value. People opting to purchase PMC speakers don't place the same value on technical performance that I do. Should I be dismissive of their values because they are different to mine?
Having said that a quantitative understanding of the pros and cons of various speaker features is likely to be of interest to most here. In another thread a PMC owner is considering measuring his speakers which may lead to a bit more information on the subject.
I mean I think everyone gets it. It works but it isn't providing PMC with an performance advantage over the competition, per say...
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Probably because I was talking about this "
I hypothesize diffraction from the skinny slots/groove in termination of the waveguide"
That makes sense. The shape increase the perimeter of the mouth, lowering the fundamental at the mouth. It would be nice to see the performance of a waveguide with similar dimension but without the grooves in comparence, to see the difference.