..and at the input.
There was a discussion of the JBL M2 waveguide where it was thought that if the diffraction were spread and diversified enough, there might be some relief.
On the other hand, is it really necessary to prioritise loading in a domestic situation? Perhaps the intended use extends beyond our typical uses?
I find this to make the list because the marketing goes pretty far out of bounds.
The only Distortion graph is in DBFS so this measurement might be at 60db at who knows what distance... The waveguide is horrendous. This makes the Gimmick list for me as soon as I seen the 20,000 dollar asking price,.
Regarding the Kef "metamaterial" which totally isn't a metamaterial, still represents a step forward that I think more manufacturers should do. My view is based on @Patrick Bateman's experiment with a Helmholtz array and I remember being impressed with the impact on low frequency distortion around Fs. I think he even made the comment on how well behaved it was at high SPL iirc.
On the subject of the thread, I think enough work has been done to show port performance is really limited by the termination, and how the movement of the air in the port transforms as it meets the outside. As long as the port is smooth inside, and not too curved, there is really nothing interesting going on there that is a practical limit. I don't see how the PMC really addresses this. I guess its termination device is kind of like a huge flare according to their claims of increased surface area. But is it? And is it enough of an increase to matter?
On the subject of the thread, I think enough work has been done to show port performance is really limited by the termination, and how the movement of the air in the port transforms as it meets the outside. As long as the port is smooth inside, and not too curved, there is really nothing interesting going on there that is a practical limit. I don't see how the PMC really addresses this. I guess its termination device is kind of like a huge flare according to their claims of increased surface area. But is it? And is it enough of an increase to matter?
Gimmicks in audiophilia? Surely it can't be true.
Yes. It's basically and in accordance to the law/equation of Hagen-Poiseuille. For the (laminar) flowing resistance in a tube:
R is the laminar flow resistance, di is the diameter of the tube.
So, very roughly approximated, if you e.g. split a duct of diameter di_pre = 2 into four subtubes, you get four ducts of half the diameter di_post = 1.
di_pre = 2,
di_pre ^ 4 = 16
di_post = di_pre / 2 = 1
di_post ^ 4 = 1
Each new subtube will have a 16-fold laminar flow resistance R.
As there are 4 new subtubes connected in parallel, the total R_post = 16/4 = 4
So, making 4 ducts out of one single duct increases the flow resistance by a factor of 4.
Same calculations apply in approximation for other duct subsplittings.
This was assuming laminar flow. Keep in mind that for the turbulent flow R raises more, because of di^5 inside of the equation:
It's a matter of physics that intersecting an acoustic duct into parallelled sub-ducts does raise it's acoustic impedance. This fact might be used to tailor it's acoustical behavior. Keep in mind that thes basic equations are valid for circular ducts and for quasi non-compressible media, such as water. Different cross-sections an air will lead to different result. The basic principles however remain the same.
Instead, claiming that "... multiple channels increase hydrolic diameter of duct, reducing turbulence ..." is nothing but nonsense.
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From a historical perspective, I don't think there's ever been a speaker design nor an audio technology that wasn't at least partly a gimmick—and I don't think that's changed even today.
The whole stereo system itself is basically a gimmick on the level of 3D glasses at the movies. Conversely, the 4-channel systems of the 1970s were seen as a gimmick and ended up failing.
For some reason, certain gimmicks catch on and become popular, and as they become more widespread, people stop seeing them as gimmicks.
I think that's all there is to it.
Are you saying that increasing flow resistance and raising the acoustic impedance in a compressible rapidly oscillating media (air) between 20-100Hz reduces or increases turbulence noise?
It's fairly difficult to name a ten dollar enhancement that does more to improve speaker perfromance than Kef's metamaterial absorber.
I've posted measurements I've made of the ones I 3D printed. They achieved the following:
1) simplifies passive crossover design by reducing the height of the impedance peak of the driver.
2) It significantly lowers distortion. Someone who knows loudspeaker motors better than I do would have to chime in on this one. I believe it's related to the change in the impedance curve. For instance, I put a metamaterial absorber on a BG NEO3 clone and it did absolutely nothing. I believe the reason for this is because the NEO3 has nearly no impedance peak.
3) Due to the larger chamber size, the tweeter tends to play lower.
Could the same benefits have been obtained more cheaply using a conventional approach with stuffing and perhaps a grille if the objective is more than absorption?
Could it be Patrick and Andy are not in disagreement: proper stuffing might achieve the same results, but the absorber array is a heck of lot cheaper to use (and is more consistent) in large series production of the drivers?
Hagen-Poiseuille is only strictly valid for the case of f = 0Hz. This excludes e.g. any resonances within the tube. We should then have a valid and specific model for f > 0Hz to anwer the question about what happens for oscillating media. So my input was an approximation of what might happen in non-stuffed, acoustically short (below f_res) LS ducts.
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Good point w.r.t. to mass production. I cannot see it being cheaper than a conventional solution but the cost in tooling and materials for the numbers KEF manufacture is likely to be modest.
KEF have a history with similar innovations/featutes such as activated carbon which did offer an engineering improvement in reducing speaker volume rather than a solution in a different package. Not familiar with the pros and cons of activated carbon but it didn't seem to receive the same response as metamaterials.
Gimmicks are usually marketing nonsense like "digital speakers".
I don't understand speakers with a phase plug that is attached to the cone. I'm sure it does something with phase, but probably not anything good.
Thin speakers with a stack of 3 or 4" drivers that aren't in any kind of electrical or acoustic array.
Bose 901's were a great gimmick. Bose sold thousands of the direct-indirect radiating speakers. It's OK if that's your thing, but to call it HiFi is a stretch.
Super-tweeters for people over 40.
Tiny little subwoofers with tiny little amps that make Top Gun rumble.
I think loudspeaker spikes are a huge gimmick, I know I'll go to HiFi jail for that, but I really don't think they are magical. You raise the speaker 1" off the floor, big effin deal. 'It's anchored to the floor now.' I imagine it is since it weighs 85 pounds, where the heck is it going?
Plinths. I love this one, these are great money makers. Sell people blocks of hardwood and tell them that oak sounds different than maple. Great stuff. Personally I like hardwood railroad ties. They bring a certain rustic appeal to the music. If it's good enough for a GE diesel electric it's good enough for my LaScalas.
I don't understand speakers with a phase plug that is attached to the cone. I'm sure it does something with phase, but probably not anything good.
Thin speakers with a stack of 3 or 4" drivers that aren't in any kind of electrical or acoustic array.
Bose 901's were a great gimmick. Bose sold thousands of the direct-indirect radiating speakers. It's OK if that's your thing, but to call it HiFi is a stretch.
Super-tweeters for people over 40.
Tiny little subwoofers with tiny little amps that make Top Gun rumble.
I think loudspeaker spikes are a huge gimmick, I know I'll go to HiFi jail for that, but I really don't think they are magical. You raise the speaker 1" off the floor, big effin deal. 'It's anchored to the floor now.' I imagine it is since it weighs 85 pounds, where the heck is it going?
Plinths. I love this one, these are great money makers. Sell people blocks of hardwood and tell them that oak sounds different than maple. Great stuff. Personally I like hardwood railroad ties. They bring a certain rustic appeal to the music. If it's good enough for a GE diesel electric it's good enough for my LaScalas.
I agree with what you said except I believe some products have a higher level of deception.
This is the most eloquent load of crap I've ever seen, rivaling AI's ability to generate a large amount of content that is as insignificant. Its impressive in a diabolical way.
Looks like in the first few posts PMC is using a dome mid with waveguide.
Then using Helmholtz Absorber and improved port exit for transmission line.
No gimmicks, dome mid has numerous advantages and using a waveguide to extend low frequency
is more than good idea for the common low frequency tradeoffs you might encounter using a standard dome mid.
transmission lines tend to barf a lot of resonance peaks.
So using a absorber and improved port exit is a notable amount of design time to improve known downfalls of TL lines.
Far as the " brand" using 6 zillion tweeters with horrid center to center. serving no purpose.
yes horrible. Making assumptions how horrible was assumption. until finally seeing some measurements of the things.
Yup did what expected.
Then using Helmholtz Absorber and improved port exit for transmission line.
No gimmicks, dome mid has numerous advantages and using a waveguide to extend low frequency
is more than good idea for the common low frequency tradeoffs you might encounter using a standard dome mid.
transmission lines tend to barf a lot of resonance peaks.
So using a absorber and improved port exit is a notable amount of design time to improve known downfalls of TL lines.
Far as the " brand" using 6 zillion tweeters with horrid center to center. serving no purpose.
yes horrible. Making assumptions how horrible was assumption. until finally seeing some measurements of the things.
Yup did what expected.
I can understand the marketing hype put forth by companies like PMC. Customers need to feel like they getting excellent value for their dollar (at least here in the US) and showering them with fancy, impressive technical mumbo jumbo usually does a sufficient job to convince them they're getting their money's worth.
I believe that companies like Bose wouldn't exist without alot of BS patented technical hype being put out by the so called engineers. This makes some people feel very warm and fuzzy, like they're purchasing a highly engineered, scientific grade device designed by aero-space engineers. Bose customers are usually very well off and know absolutely nothing about audio. They listen to music on their iPhone through boomy, muddy sounding air pods or their pathetic TV sound bar.
I’ve owned a few PMC systems and some of them are very good sounding, professional monitor grade speakers. I don’t look at or pay attention to marketing gimmicks. I just don't care how its done or with which patented method. As long as the speaker sounds right for my needs and is serviceable (warranty backed) in the event of an issue, that's all I care about.
I believe that companies like Bose wouldn't exist without alot of BS patented technical hype being put out by the so called engineers. This makes some people feel very warm and fuzzy, like they're purchasing a highly engineered, scientific grade device designed by aero-space engineers. Bose customers are usually very well off and know absolutely nothing about audio. They listen to music on their iPhone through boomy, muddy sounding air pods or their pathetic TV sound bar.
I’ve owned a few PMC systems and some of them are very good sounding, professional monitor grade speakers. I don’t look at or pay attention to marketing gimmicks. I just don't care how its done or with which patented method. As long as the speaker sounds right for my needs and is serviceable (warranty backed) in the event of an issue, that's all I care about.